Fateh Bazerbachi, MD

In Reply: We welcome the comments from Dr. Chongnarungsin on our article and the opportunity to further discuss our opinions.

In our paper, we discussed current recommendations for prophylaxis of stress ulcer-related bleeding in hospitalized patients and advocated against the blind administration of drugs without risk stratification.

The landmark trial that provides the most-cited definitions and the risk factors for clinically significant stress ulcer-related bleeding in critically ill patients was published in 1994 by Cook et al.¹ In their multicenter prospective cohort study of 2,252 patients, the authors reported that prolonged mechanical ventilation is an important risk factor for clinically significant stress ulcer-related bleeding.

Another major prospective cohort study observed an incidence rate of clinically significant stress ulcer-related bleeding of 3.5%.²

Dr. Chongnarungsin cites another prospective cohort study of 183 patients from the same era,³ wherein the authors defined stress ulcer-related bleeding as bleeding requiring transfusion of packed red blood cells, found on endoscopy or on postmortem evaluation. This was in contrast to the 1994 study of Cook et al,¹ who had a more rigorous and comprehensive definition for overt and clinically significant stress ulcer-related bleeding, applied by up to three independent adjudicators not involved in the patients’ care. Their definition not only entailed a more accurate transfusion-dependent bleeding criterion, but also included hemodynamic and laboratory criteria. As such, the “very low rate” of stress ulcer-related bleeding reported by Zandstra et al³ should be critically appraised. Of note, the authors in that study did not report the rates of patients who received early enteral feeding, and their patients received cefotaxime for digestive tract decontamination, an important confounder to the interpretation of the study results.

Indeed, the remarkable variation in estimates of the incidence of stress ulcer-related bleeding is probably related to the lack of a uniform definition. Even when rates of endoscopic and occult bleeding are set aside, agreement is lacking as to which category of bleeding is clinically significant.

Dr. Chongnarungsin also cites the study by Ellison et al⁴ of a cohort of 874 patients who had no previous gastrointestinal bleeding or peptic ulcer disease and who were enrolled in a multicenter randomized controlled trial of prophylactic intravenous immune globulin to prevent infections associated with an intensive care unit. In a secondary objective, the authors did not identify coagulopathy or prolonged mechanical ventilation as a principal risk factor for bleeding. The authors ascribed this discrepancy with previously published literature to their unique study population, which consisted predominantly of elderly men and rarely included trauma patients. In light of these unique peculiarities of their population, the lack of an association between prolonged mechanical ventilation and stress ulcer-related bleeding cannot be determined. Moreover, that study showed that prolonged nasogastric tube insertion was one of the risk factors for increased risk of gastrointestinal bleeding, and not the risk factor for development of stress ulcer as stated by Dr. Chongnarungsin.

The decrease in the incidence of stress ulcer-related bleeding in critically ill patients over the years could be attributed to an era effect, from advances in critical care medicine and prophylactic methods.⁵ We agree with Dr. Chongnarungsin that the increased introduction of early enteral feeding may have also contributed to the reduced incidence of stress ulcer-related bleeding.⁶ However, we think the conclusion that “mechanical ventilation for more than 48 hours does not seem to increase the risk of stress ulcer” is overelaborated, and we believe that strong evidence demonstrates this association.^1,2

Alternatively, we recognize the lack of mortality-benefit evidence for stress ulcer prophylaxis. This notwithstanding, according to recent Surviving Sepsis Campaign guidelines, the use of stress ulcer prophylaxis is listed as a 1B recommendation (strong recommendation) for severely septic patients who require prolonged mechanical ventilation. In addition, the updated 2014 guidelines of the American Society of Health-System Pharmacists⁷ continue to recommend stress ulcer prophylaxis in the context of mechanical ventilation, with H2 receptor antagonists being the preferred first-line agents.⁸

It is important to acknowledge that these recommendations were endorsed despite the lack of obvious mortality benefit, and it is our opinion that large randomized controlled studies are needed to evaluate the risks and mortality benefit of these prophylaxis methods.

In Reply: We welcome the comments from Dr. Chongnarungsin on our article and the opportunity to further discuss our opinions.

In our paper, we discussed current recommendations for prophylaxis of stress ulcer-related bleeding in hospitalized patients and advocated against the blind administration of drugs without risk stratification.

The landmark trial that provides the most-cited definitions and the risk factors for clinically significant stress ulcer-related bleeding in critically ill patients was published in 1994 by Cook et al.¹ In their multicenter prospective cohort study of 2,252 patients, the authors reported that prolonged mechanical ventilation is an important risk factor for clinically significant stress ulcer-related bleeding.

Another major prospective cohort study observed an incidence rate of clinically significant stress ulcer-related bleeding of 3.5%.²

Dr. Chongnarungsin cites another prospective cohort study of 183 patients from the same era,³ wherein the authors defined stress ulcer-related bleeding as bleeding requiring transfusion of packed red blood cells, found on endoscopy or on postmortem evaluation. This was in contrast to the 1994 study of Cook et al,¹ who had a more rigorous and comprehensive definition for overt and clinically significant stress ulcer-related bleeding, applied by up to three independent adjudicators not involved in the patients’ care. Their definition not only entailed a more accurate transfusion-dependent bleeding criterion, but also included hemodynamic and laboratory criteria. As such, the “very low rate” of stress ulcer-related bleeding reported by Zandstra et al³ should be critically appraised. Of note, the authors in that study did not report the rates of patients who received early enteral feeding, and their patients received cefotaxime for digestive tract decontamination, an important confounder to the interpretation of the study results.

Indeed, the remarkable variation in estimates of the incidence of stress ulcer-related bleeding is probably related to the lack of a uniform definition. Even when rates of endoscopic and occult bleeding are set aside, agreement is lacking as to which category of bleeding is clinically significant.

Dr. Chongnarungsin also cites the study by Ellison et al⁴ of a cohort of 874 patients who had no previous gastrointestinal bleeding or peptic ulcer disease and who were enrolled in a multicenter randomized controlled trial of prophylactic intravenous immune globulin to prevent infections associated with an intensive care unit. In a secondary objective, the authors did not identify coagulopathy or prolonged mechanical ventilation as a principal risk factor for bleeding. The authors ascribed this discrepancy with previously published literature to their unique study population, which consisted predominantly of elderly men and rarely included trauma patients. In light of these unique peculiarities of their population, the lack of an association between prolonged mechanical ventilation and stress ulcer-related bleeding cannot be determined. Moreover, that study showed that prolonged nasogastric tube insertion was one of the risk factors for increased risk of gastrointestinal bleeding, and not the risk factor for development of stress ulcer as stated by Dr. Chongnarungsin.

The decrease in the incidence of stress ulcer-related bleeding in critically ill patients over the years could be attributed to an era effect, from advances in critical care medicine and prophylactic methods.⁵ We agree with Dr. Chongnarungsin that the increased introduction of early enteral feeding may have also contributed to the reduced incidence of stress ulcer-related bleeding.⁶ However, we think the conclusion that “mechanical ventilation for more than 48 hours does not seem to increase the risk of stress ulcer” is overelaborated, and we believe that strong evidence demonstrates this association.^1,2

Alternatively, we recognize the lack of mortality-benefit evidence for stress ulcer prophylaxis. This notwithstanding, according to recent Surviving Sepsis Campaign guidelines, the use of stress ulcer prophylaxis is listed as a 1B recommendation (strong recommendation) for severely septic patients who require prolonged mechanical ventilation. In addition, the updated 2014 guidelines of the American Society of Health-System Pharmacists⁷ continue to recommend stress ulcer prophylaxis in the context of mechanical ventilation, with H2 receptor antagonists being the preferred first-line agents.⁸

It is important to acknowledge that these recommendations were endorsed despite the lack of obvious mortality benefit, and it is our opinion that large randomized controlled studies are needed to evaluate the risks and mortality benefit of these prophylaxis methods.

In Reply: We welcome the comments from Dr. Chongnarungsin on our article and the opportunity to further discuss our opinions.

In our paper, we discussed current recommendations for prophylaxis of stress ulcer-related bleeding in hospitalized patients and advocated against the blind administration of drugs without risk stratification.

The landmark trial that provides the most-cited definitions and the risk factors for clinically significant stress ulcer-related bleeding in critically ill patients was published in 1994 by Cook et al.¹ In their multicenter prospective cohort study of 2,252 patients, the authors reported that prolonged mechanical ventilation is an important risk factor for clinically significant stress ulcer-related bleeding.

Another major prospective cohort study observed an incidence rate of clinically significant stress ulcer-related bleeding of 3.5%.²

Dr. Chongnarungsin cites another prospective cohort study of 183 patients from the same era,³ wherein the authors defined stress ulcer-related bleeding as bleeding requiring transfusion of packed red blood cells, found on endoscopy or on postmortem evaluation. This was in contrast to the 1994 study of Cook et al,¹ who had a more rigorous and comprehensive definition for overt and clinically significant stress ulcer-related bleeding, applied by up to three independent adjudicators not involved in the patients’ care. Their definition not only entailed a more accurate transfusion-dependent bleeding criterion, but also included hemodynamic and laboratory criteria. As such, the “very low rate” of stress ulcer-related bleeding reported by Zandstra et al³ should be critically appraised. Of note, the authors in that study did not report the rates of patients who received early enteral feeding, and their patients received cefotaxime for digestive tract decontamination, an important confounder to the interpretation of the study results.

Indeed, the remarkable variation in estimates of the incidence of stress ulcer-related bleeding is probably related to the lack of a uniform definition. Even when rates of endoscopic and occult bleeding are set aside, agreement is lacking as to which category of bleeding is clinically significant.

Dr. Chongnarungsin also cites the study by Ellison et al⁴ of a cohort of 874 patients who had no previous gastrointestinal bleeding or peptic ulcer disease and who were enrolled in a multicenter randomized controlled trial of prophylactic intravenous immune globulin to prevent infections associated with an intensive care unit. In a secondary objective, the authors did not identify coagulopathy or prolonged mechanical ventilation as a principal risk factor for bleeding. The authors ascribed this discrepancy with previously published literature to their unique study population, which consisted predominantly of elderly men and rarely included trauma patients. In light of these unique peculiarities of their population, the lack of an association between prolonged mechanical ventilation and stress ulcer-related bleeding cannot be determined. Moreover, that study showed that prolonged nasogastric tube insertion was one of the risk factors for increased risk of gastrointestinal bleeding, and not the risk factor for development of stress ulcer as stated by Dr. Chongnarungsin.

The decrease in the incidence of stress ulcer-related bleeding in critically ill patients over the years could be attributed to an era effect, from advances in critical care medicine and prophylactic methods.⁵ We agree with Dr. Chongnarungsin that the increased introduction of early enteral feeding may have also contributed to the reduced incidence of stress ulcer-related bleeding.⁶ However, we think the conclusion that “mechanical ventilation for more than 48 hours does not seem to increase the risk of stress ulcer” is overelaborated, and we believe that strong evidence demonstrates this association.^1,2

Alternatively, we recognize the lack of mortality-benefit evidence for stress ulcer prophylaxis. This notwithstanding, according to recent Surviving Sepsis Campaign guidelines, the use of stress ulcer prophylaxis is listed as a 1B recommendation (strong recommendation) for severely septic patients who require prolonged mechanical ventilation. In addition, the updated 2014 guidelines of the American Society of Health-System Pharmacists⁷ continue to recommend stress ulcer prophylaxis in the context of mechanical ventilation, with H2 receptor antagonists being the preferred first-line agents.⁸

It is important to acknowledge that these recommendations were endorsed despite the lack of obvious mortality benefit, and it is our opinion that large randomized controlled studies are needed to evaluate the risks and mortality benefit of these prophylaxis methods.

No. Hemoglobin A_1c has been validated as a predictor of diabetes-related complications and is a standard measure of the adequacy of glucose control. But sometimes we need to regard its values with suspicion, especially when they are not concordant with the patient’s self-monitored blood glucose levels.

UNIVERSALLY USED

Measuring glycated hemoglobin has become an essential tool for detecting impaired glucose tolerance (when levels are between 5.7% and 6.5%), for diagnosing diabetes mellitus (when levels are ≥ 6.5%), and for following the adequacy of control in established disease. The results reflect glycemic control over the preceding 2 to 3 months and possibly indicate the risk of complications, particularly microvascular disease in the long term.

The significance of hemoglobin A_1c was further accentuated with the results of the DETECT-2 project,¹ which showed that the risk of diabetic retinopathy is insignificant with levels lower than 6% and rises substantially when it is greater than 6.5%.

However, because the biochemical hallmark of diabetes is hyperglycemia (and not the glycation of proteins), concerns have been raised about the universal validity of hemoglobin A_1c in all diabetic patients, especially when it is used to monitor glucose control in the long term.²

FACTORS THAT AFFECT THE GLYCATED HEMOGLOBIN LEVEL

Altered glycation

Although the hemoglobin A_1c value correlates well with the mean blood glucose level over the previous months, it is affected more by the most recent glucose levels than by earlier levels, and it is especially affected by the most recent peak in blood glucose.³ It is estimated that approximately 50% of the hemoglobin A_1c level is determined by the plasma glucose level during the preceding 1-month period.³

Other factors that affect levels of glycated hemoglobin independently of the average glucose level during the previous months include genetic predisposition (some people are “rapid glycators”), labile glycation (ie, transient glycation of hemoglobin when exposed to very high concentrations of glucose), and the 2,3-diphosphoglycerate concentration and pH of the blood.²

Hemoglobin factors

Age of red blood cells. Red blood cells last about 120 days, and the mean age of all red blood cells in circulation ranges from 38 to 60 days (50 on average). Turnover is dictated by a number of factors, including ethnicity, which in turn significantly affect hemoglobin A_1c values.

Race and ethnicity. African American, Asian, and Hispanic patients may have higher hemoglobin A_1c values than white people who have the same blood glucose levels. In one study of racial and ethnic differences in mean plasma glucose, levels were higher by 0.37% in African American patients, 0.27% in Hispanics, and 0.33% in Asians than in white patients, and the differences were statistically significant.⁴ However, there is no clear evidence that these differences are associated with differences in the incidence of microvascular disease.⁵

Effects due to heritable factors could vary among ethnic groups. Racial differences in hemoglobin A_1c may be ascribed to the degree of glycation, caused by multiple factors, and to socioeconomic status. Interestingly, many of the interracial differences in conditions that affect erythrocyte turnover would in theory lead to a lower hemoglobin A_1c in nonwhites, which is not the case.⁶

Pregnancy. The mechanisms of hemoglobin A_1c discrepancy in pregnancy are not clear. It has been demonstrated that pregnant women may have lower hemoglobin A_1c levels than nonpregnant women.^7–9 Hemodilution and increased cell turnover have been postulated to account for the decrease, although a mechanism has not been described. Interestingly, conflicting data have been reported regarding hemoglobin A_1c in the last trimester of pregnancy (increase, decrease, or no change). Iron deficiency has been presumed to cause the increase of hemoglobin A_1c in the last trimester.¹⁰

Moreover, hemoglobin A_1c may reflect glucose levels during a shorter time because of increased turnover of red blood cells that occurs during this state. Erythropoietin and erythrocyte production are increased during normal pregnancy while hemoglobin and hematocrit continuously dilute into the third trimester. In normal pregnancy, the red blood cell life span is decreased due to “emergency hemopoiesis” in response to these elevated erythropoietin levels.

Anemia. Hemolytic anemia, acute bleeding, and iron-deficiency anemia all influence glycated hemoglobin levels. The formation of reticulocytes whose hemoglobin lacks glycosylation may lead to falsely low hemoglobin A_1c values. Interestingly, iron deficiency by itself has been observed to cause elevation of hemoglobin A_1c through unclear mechanisms¹¹; however, iron replacement may lead to reticulocytosis. Alternatively, asplenic patients may have deceptively higher hemoglobin A_1c values because of the increased life span of their red blood cells.¹²

Hemoglobinopathy. Hemoglobin F may cause overestimation of hemoglobin A_1c levels, whereas hemoglobin S and hemoglobin C may cause underestimation. Of note, these effects are method-specific, and newer immunoassay techniques are relatively robust even in the presence of common hemoglobin variants. Clinicians should be aware of their institution’s laboratory method for measuring glycated hemoglobin.¹³

Chronic illnesses can cause fluctuation in hemoglobin A_1c and make it unreliable. Uremia, severe hypertriglyceridemia, severe hyperbilirubinemia, chronic alcoholism, chronic salicylate use, chronic opioid use, and lead poisoning all can falsely increase hemoglobin A_1c levels.

Vitamin and mineral deficiencies (eg, deficiencies of vitamin B₁₂ and iron) can reduce red blood cell turnover and therefore falsely elevate hemoglobin A_1c levels. Conversely, medical replacement of these deficiencies could lead to higher red blood cell turnover and reduced hemoglobin A_1c levels.

Blood transfusions. Recent reports suggest that red blood cell transfusions reduce the hemoglobin A_1c concentration in diabetic patients. This effect was most pronounced in patients who received large transfusion volumes or who had a high hemoglobin A_1c level before the transfusion.¹⁴

Renal failure. Patients with renal failure have higher levels of carbamylated hemoglobin, which is reported to interfere with measurement and interpretation of hemoglobin A_1c. Moreover, there is concern that hemoglobin A_1c values may be falsely low in these patients because of shortened erythrocyte survival. Other factors that influence hemoglobin A_1c and cause the measured levels to be misleadingly low in renal failure patients include use of recombinant human erythropoietin, the uremic environment, and blood transfusions.¹⁵

It has been suggested that glycated albumin may be a better marker for assessing glycemic control in patients with severe chronic kidney disease.¹⁶

Medications and supplements that affect hemoglobin

Drugs that may cause hemolysis could lower hemoglobin A_1c levels. Examples are dapsone, ribavirin, and sulfonamides. Other drugs can change the structure of hemoglobin. For example, hydroxyurea alters hemoglobin A into hemoglobin F, thus lowering the hemoglobin A_1c level. Chronic opiate use has been reported to increase hemoglobin A_1c levels through mechanisms yet unclear.

Aspirin, vitamin C, and vitamin E have been postulated to interfere with hemoglobin A_1c measurement assays, although studies have not been consistent in demonstrating these effects.

Labile diabetes

In some patients with diabetes, blood glucose levels are labile and oscillate between states of hypoglycemia and hyperglycemia, despite optimal hemoglobin A_1c levels.¹⁷ In these patients, the average blood glucose level may very well correlate appropriately with the glycated hemoglobin level, but the degree of control would not be acceptable. Fasting hyperglycemia or postprandial hyperglycemia, or both, especially in the setting of significant glycemic variability over the month before testing, may not be captured by the hemoglobin A_1c measurement. These glycemic excursions may be important, as data suggest that this variability may independently worsen microvascular complications in diabetic patients.¹⁸

ALTERNATIVES TO MEASURING THE GLYCATED HEMOGLOBIN

When hemoglobin A_1c levels are suspected to be inaccurate, other tests of the adequacy of glycemic control can be used.¹⁹

Continuous glucose monitoring is the gold standard and precisely shows the degree of glycemic variability, usually over 5 days. It is often used when hypoglycemia and wide fluctuations in within-day and day-to-day glucose levels are suspected. In addition, we believe that continuous monitoring could be used to confirm the validity of hemoglobin A_1c testing. In a clinical setting in which the level does not seem to match the fingerstick blood glucose readings, it can be a useful tool to assess the range and variation in glycemic control.

This method, however, is not practical in all diabetic patients, and it certainly does not have the same long-term predictive prognostic value. Yet it may still have a role in validating measures of long-term glycemic control (eg, hemoglobin A_1c). There is evidence that using continuous glucose monitoring periodically can improve glycemic control, lower hemoglobin A_1c levels, and lead to fewer hypoglycemic events.²⁰ As discussed earlier, patients who have labile glycemic excursions and higher risk of microvascular complications can still have “normal” hemoglobin A_1c levels; in this scenario, the use of continuous glucose monitoring can lead to lower risk and better control.

1,5-anhydroglucitol and fructosamine are circulating biomarkers that reflect short-term glucose control, ie, over 2 to 3 weeks. The higher the average blood glucose level, the lower the 1,5-anhydroglucitol level, since higher glucose levels competitively inhibit renal reabsorption of this molecule. However, its utility is limited in renal failure, liver disease, and pregnancy.

Fructosamines are nonenzymatically glycated proteins. As markers, they are reliable in renal disease but are unreliable in hypoproteinemic states such as liver disease, nephrosis, and lipemia. This group of proteins represents all of serum-stable glycated proteins; they are strongly influenced by the concentration of serum proteins, as well as by coexisting low-molecular-weight substances in the plasma.

Glycated albumin is superior to glycated hemoglobin in reflecting glycemic control, as it has a faster metabolic turnover than hemoglobin and is not affected by hemoglobin-opathies. Unlike fructosamines, it is not influenced by the serum albumin concentration. Moreover, it may be superior to the hemoglobin A_1c in patients who have postprandial hypoglycemia.²¹

Interestingly, recent cross-sectional analyses suggest that fructosamines and glycated albumin are at least as strongly associated with microvascular complications as the hemoglobin A_1c is.²²

BE ALERT TO FACTORS THAT AFFECT GLYCATED HEMOGLOBIN

Hemoglobin A_1c reflects exposure of red blood cells to glucose. Multiple factors—pathologic, physiologic, and environmental—can influence the glycation process, red blood cell turnover, and the hemoglobin structure in ways that can decrease the reliability of the hemoglobin A_1c measurement.

Clinicians should be vigilant for the various clinical situations in which hemoglobin A_1c is hard to interpret, and they should be familiar with alternative tests (eg, continuous glucose monitoring, 1,5-anhydroglucitol, fructosamines) that can be used to monitor adequate glycemic control in these patients.

No. Hemoglobin A_1c has been validated as a predictor of diabetes-related complications and is a standard measure of the adequacy of glucose control. But sometimes we need to regard its values with suspicion, especially when they are not concordant with the patient’s self-monitored blood glucose levels.

UNIVERSALLY USED

Measuring glycated hemoglobin has become an essential tool for detecting impaired glucose tolerance (when levels are between 5.7% and 6.5%), for diagnosing diabetes mellitus (when levels are ≥ 6.5%), and for following the adequacy of control in established disease. The results reflect glycemic control over the preceding 2 to 3 months and possibly indicate the risk of complications, particularly microvascular disease in the long term.

The significance of hemoglobin A_1c was further accentuated with the results of the DETECT-2 project,¹ which showed that the risk of diabetic retinopathy is insignificant with levels lower than 6% and rises substantially when it is greater than 6.5%.

However, because the biochemical hallmark of diabetes is hyperglycemia (and not the glycation of proteins), concerns have been raised about the universal validity of hemoglobin A_1c in all diabetic patients, especially when it is used to monitor glucose control in the long term.²

FACTORS THAT AFFECT THE GLYCATED HEMOGLOBIN LEVEL

Altered glycation

Although the hemoglobin A_1c value correlates well with the mean blood glucose level over the previous months, it is affected more by the most recent glucose levels than by earlier levels, and it is especially affected by the most recent peak in blood glucose.³ It is estimated that approximately 50% of the hemoglobin A_1c level is determined by the plasma glucose level during the preceding 1-month period.³

Other factors that affect levels of glycated hemoglobin independently of the average glucose level during the previous months include genetic predisposition (some people are “rapid glycators”), labile glycation (ie, transient glycation of hemoglobin when exposed to very high concentrations of glucose), and the 2,3-diphosphoglycerate concentration and pH of the blood.²

Hemoglobin factors

Age of red blood cells. Red blood cells last about 120 days, and the mean age of all red blood cells in circulation ranges from 38 to 60 days (50 on average). Turnover is dictated by a number of factors, including ethnicity, which in turn significantly affect hemoglobin A_1c values.

Race and ethnicity. African American, Asian, and Hispanic patients may have higher hemoglobin A_1c values than white people who have the same blood glucose levels. In one study of racial and ethnic differences in mean plasma glucose, levels were higher by 0.37% in African American patients, 0.27% in Hispanics, and 0.33% in Asians than in white patients, and the differences were statistically significant.⁴ However, there is no clear evidence that these differences are associated with differences in the incidence of microvascular disease.⁵

Effects due to heritable factors could vary among ethnic groups. Racial differences in hemoglobin A_1c may be ascribed to the degree of glycation, caused by multiple factors, and to socioeconomic status. Interestingly, many of the interracial differences in conditions that affect erythrocyte turnover would in theory lead to a lower hemoglobin A_1c in nonwhites, which is not the case.⁶

Pregnancy. The mechanisms of hemoglobin A_1c discrepancy in pregnancy are not clear. It has been demonstrated that pregnant women may have lower hemoglobin A_1c levels than nonpregnant women.^7–9 Hemodilution and increased cell turnover have been postulated to account for the decrease, although a mechanism has not been described. Interestingly, conflicting data have been reported regarding hemoglobin A_1c in the last trimester of pregnancy (increase, decrease, or no change). Iron deficiency has been presumed to cause the increase of hemoglobin A_1c in the last trimester.¹⁰

Moreover, hemoglobin A_1c may reflect glucose levels during a shorter time because of increased turnover of red blood cells that occurs during this state. Erythropoietin and erythrocyte production are increased during normal pregnancy while hemoglobin and hematocrit continuously dilute into the third trimester. In normal pregnancy, the red blood cell life span is decreased due to “emergency hemopoiesis” in response to these elevated erythropoietin levels.

Anemia. Hemolytic anemia, acute bleeding, and iron-deficiency anemia all influence glycated hemoglobin levels. The formation of reticulocytes whose hemoglobin lacks glycosylation may lead to falsely low hemoglobin A_1c values. Interestingly, iron deficiency by itself has been observed to cause elevation of hemoglobin A_1c through unclear mechanisms¹¹; however, iron replacement may lead to reticulocytosis. Alternatively, asplenic patients may have deceptively higher hemoglobin A_1c values because of the increased life span of their red blood cells.¹²

Hemoglobinopathy. Hemoglobin F may cause overestimation of hemoglobin A_1c levels, whereas hemoglobin S and hemoglobin C may cause underestimation. Of note, these effects are method-specific, and newer immunoassay techniques are relatively robust even in the presence of common hemoglobin variants. Clinicians should be aware of their institution’s laboratory method for measuring glycated hemoglobin.¹³

Chronic illnesses can cause fluctuation in hemoglobin A_1c and make it unreliable. Uremia, severe hypertriglyceridemia, severe hyperbilirubinemia, chronic alcoholism, chronic salicylate use, chronic opioid use, and lead poisoning all can falsely increase hemoglobin A_1c levels.

Vitamin and mineral deficiencies (eg, deficiencies of vitamin B₁₂ and iron) can reduce red blood cell turnover and therefore falsely elevate hemoglobin A_1c levels. Conversely, medical replacement of these deficiencies could lead to higher red blood cell turnover and reduced hemoglobin A_1c levels.

Blood transfusions. Recent reports suggest that red blood cell transfusions reduce the hemoglobin A_1c concentration in diabetic patients. This effect was most pronounced in patients who received large transfusion volumes or who had a high hemoglobin A_1c level before the transfusion.¹⁴

Renal failure. Patients with renal failure have higher levels of carbamylated hemoglobin, which is reported to interfere with measurement and interpretation of hemoglobin A_1c. Moreover, there is concern that hemoglobin A_1c values may be falsely low in these patients because of shortened erythrocyte survival. Other factors that influence hemoglobin A_1c and cause the measured levels to be misleadingly low in renal failure patients include use of recombinant human erythropoietin, the uremic environment, and blood transfusions.¹⁵

It has been suggested that glycated albumin may be a better marker for assessing glycemic control in patients with severe chronic kidney disease.¹⁶

Medications and supplements that affect hemoglobin

Drugs that may cause hemolysis could lower hemoglobin A_1c levels. Examples are dapsone, ribavirin, and sulfonamides. Other drugs can change the structure of hemoglobin. For example, hydroxyurea alters hemoglobin A into hemoglobin F, thus lowering the hemoglobin A_1c level. Chronic opiate use has been reported to increase hemoglobin A_1c levels through mechanisms yet unclear.

Aspirin, vitamin C, and vitamin E have been postulated to interfere with hemoglobin A_1c measurement assays, although studies have not been consistent in demonstrating these effects.

Labile diabetes

In some patients with diabetes, blood glucose levels are labile and oscillate between states of hypoglycemia and hyperglycemia, despite optimal hemoglobin A_1c levels.¹⁷ In these patients, the average blood glucose level may very well correlate appropriately with the glycated hemoglobin level, but the degree of control would not be acceptable. Fasting hyperglycemia or postprandial hyperglycemia, or both, especially in the setting of significant glycemic variability over the month before testing, may not be captured by the hemoglobin A_1c measurement. These glycemic excursions may be important, as data suggest that this variability may independently worsen microvascular complications in diabetic patients.¹⁸

ALTERNATIVES TO MEASURING THE GLYCATED HEMOGLOBIN

When hemoglobin A_1c levels are suspected to be inaccurate, other tests of the adequacy of glycemic control can be used.¹⁹

Continuous glucose monitoring is the gold standard and precisely shows the degree of glycemic variability, usually over 5 days. It is often used when hypoglycemia and wide fluctuations in within-day and day-to-day glucose levels are suspected. In addition, we believe that continuous monitoring could be used to confirm the validity of hemoglobin A_1c testing. In a clinical setting in which the level does not seem to match the fingerstick blood glucose readings, it can be a useful tool to assess the range and variation in glycemic control.

This method, however, is not practical in all diabetic patients, and it certainly does not have the same long-term predictive prognostic value. Yet it may still have a role in validating measures of long-term glycemic control (eg, hemoglobin A_1c). There is evidence that using continuous glucose monitoring periodically can improve glycemic control, lower hemoglobin A_1c levels, and lead to fewer hypoglycemic events.²⁰ As discussed earlier, patients who have labile glycemic excursions and higher risk of microvascular complications can still have “normal” hemoglobin A_1c levels; in this scenario, the use of continuous glucose monitoring can lead to lower risk and better control.

1,5-anhydroglucitol and fructosamine are circulating biomarkers that reflect short-term glucose control, ie, over 2 to 3 weeks. The higher the average blood glucose level, the lower the 1,5-anhydroglucitol level, since higher glucose levels competitively inhibit renal reabsorption of this molecule. However, its utility is limited in renal failure, liver disease, and pregnancy.

Fructosamines are nonenzymatically glycated proteins. As markers, they are reliable in renal disease but are unreliable in hypoproteinemic states such as liver disease, nephrosis, and lipemia. This group of proteins represents all of serum-stable glycated proteins; they are strongly influenced by the concentration of serum proteins, as well as by coexisting low-molecular-weight substances in the plasma.

Glycated albumin is superior to glycated hemoglobin in reflecting glycemic control, as it has a faster metabolic turnover than hemoglobin and is not affected by hemoglobin-opathies. Unlike fructosamines, it is not influenced by the serum albumin concentration. Moreover, it may be superior to the hemoglobin A_1c in patients who have postprandial hypoglycemia.²¹

Interestingly, recent cross-sectional analyses suggest that fructosamines and glycated albumin are at least as strongly associated with microvascular complications as the hemoglobin A_1c is.²²

BE ALERT TO FACTORS THAT AFFECT GLYCATED HEMOGLOBIN

Hemoglobin A_1c reflects exposure of red blood cells to glucose. Multiple factors—pathologic, physiologic, and environmental—can influence the glycation process, red blood cell turnover, and the hemoglobin structure in ways that can decrease the reliability of the hemoglobin A_1c measurement.

Clinicians should be vigilant for the various clinical situations in which hemoglobin A_1c is hard to interpret, and they should be familiar with alternative tests (eg, continuous glucose monitoring, 1,5-anhydroglucitol, fructosamines) that can be used to monitor adequate glycemic control in these patients.

No. Hemoglobin A_1c has been validated as a predictor of diabetes-related complications and is a standard measure of the adequacy of glucose control. But sometimes we need to regard its values with suspicion, especially when they are not concordant with the patient’s self-monitored blood glucose levels.

UNIVERSALLY USED

Measuring glycated hemoglobin has become an essential tool for detecting impaired glucose tolerance (when levels are between 5.7% and 6.5%), for diagnosing diabetes mellitus (when levels are ≥ 6.5%), and for following the adequacy of control in established disease. The results reflect glycemic control over the preceding 2 to 3 months and possibly indicate the risk of complications, particularly microvascular disease in the long term.

The significance of hemoglobin A_1c was further accentuated with the results of the DETECT-2 project,¹ which showed that the risk of diabetic retinopathy is insignificant with levels lower than 6% and rises substantially when it is greater than 6.5%.

However, because the biochemical hallmark of diabetes is hyperglycemia (and not the glycation of proteins), concerns have been raised about the universal validity of hemoglobin A_1c in all diabetic patients, especially when it is used to monitor glucose control in the long term.²

FACTORS THAT AFFECT THE GLYCATED HEMOGLOBIN LEVEL

Altered glycation

Although the hemoglobin A_1c value correlates well with the mean blood glucose level over the previous months, it is affected more by the most recent glucose levels than by earlier levels, and it is especially affected by the most recent peak in blood glucose.³ It is estimated that approximately 50% of the hemoglobin A_1c level is determined by the plasma glucose level during the preceding 1-month period.³

Other factors that affect levels of glycated hemoglobin independently of the average glucose level during the previous months include genetic predisposition (some people are “rapid glycators”), labile glycation (ie, transient glycation of hemoglobin when exposed to very high concentrations of glucose), and the 2,3-diphosphoglycerate concentration and pH of the blood.²

Hemoglobin factors

Age of red blood cells. Red blood cells last about 120 days, and the mean age of all red blood cells in circulation ranges from 38 to 60 days (50 on average). Turnover is dictated by a number of factors, including ethnicity, which in turn significantly affect hemoglobin A_1c values.

Race and ethnicity. African American, Asian, and Hispanic patients may have higher hemoglobin A_1c values than white people who have the same blood glucose levels. In one study of racial and ethnic differences in mean plasma glucose, levels were higher by 0.37% in African American patients, 0.27% in Hispanics, and 0.33% in Asians than in white patients, and the differences were statistically significant.⁴ However, there is no clear evidence that these differences are associated with differences in the incidence of microvascular disease.⁵

Effects due to heritable factors could vary among ethnic groups. Racial differences in hemoglobin A_1c may be ascribed to the degree of glycation, caused by multiple factors, and to socioeconomic status. Interestingly, many of the interracial differences in conditions that affect erythrocyte turnover would in theory lead to a lower hemoglobin A_1c in nonwhites, which is not the case.⁶

Pregnancy. The mechanisms of hemoglobin A_1c discrepancy in pregnancy are not clear. It has been demonstrated that pregnant women may have lower hemoglobin A_1c levels than nonpregnant women.^7–9 Hemodilution and increased cell turnover have been postulated to account for the decrease, although a mechanism has not been described. Interestingly, conflicting data have been reported regarding hemoglobin A_1c in the last trimester of pregnancy (increase, decrease, or no change). Iron deficiency has been presumed to cause the increase of hemoglobin A_1c in the last trimester.¹⁰

Moreover, hemoglobin A_1c may reflect glucose levels during a shorter time because of increased turnover of red blood cells that occurs during this state. Erythropoietin and erythrocyte production are increased during normal pregnancy while hemoglobin and hematocrit continuously dilute into the third trimester. In normal pregnancy, the red blood cell life span is decreased due to “emergency hemopoiesis” in response to these elevated erythropoietin levels.

Anemia. Hemolytic anemia, acute bleeding, and iron-deficiency anemia all influence glycated hemoglobin levels. The formation of reticulocytes whose hemoglobin lacks glycosylation may lead to falsely low hemoglobin A_1c values. Interestingly, iron deficiency by itself has been observed to cause elevation of hemoglobin A_1c through unclear mechanisms¹¹; however, iron replacement may lead to reticulocytosis. Alternatively, asplenic patients may have deceptively higher hemoglobin A_1c values because of the increased life span of their red blood cells.¹²

Hemoglobinopathy. Hemoglobin F may cause overestimation of hemoglobin A_1c levels, whereas hemoglobin S and hemoglobin C may cause underestimation. Of note, these effects are method-specific, and newer immunoassay techniques are relatively robust even in the presence of common hemoglobin variants. Clinicians should be aware of their institution’s laboratory method for measuring glycated hemoglobin.¹³

Chronic illnesses can cause fluctuation in hemoglobin A_1c and make it unreliable. Uremia, severe hypertriglyceridemia, severe hyperbilirubinemia, chronic alcoholism, chronic salicylate use, chronic opioid use, and lead poisoning all can falsely increase hemoglobin A_1c levels.

Vitamin and mineral deficiencies (eg, deficiencies of vitamin B₁₂ and iron) can reduce red blood cell turnover and therefore falsely elevate hemoglobin A_1c levels. Conversely, medical replacement of these deficiencies could lead to higher red blood cell turnover and reduced hemoglobin A_1c levels.

Blood transfusions. Recent reports suggest that red blood cell transfusions reduce the hemoglobin A_1c concentration in diabetic patients. This effect was most pronounced in patients who received large transfusion volumes or who had a high hemoglobin A_1c level before the transfusion.¹⁴

Renal failure. Patients with renal failure have higher levels of carbamylated hemoglobin, which is reported to interfere with measurement and interpretation of hemoglobin A_1c. Moreover, there is concern that hemoglobin A_1c values may be falsely low in these patients because of shortened erythrocyte survival. Other factors that influence hemoglobin A_1c and cause the measured levels to be misleadingly low in renal failure patients include use of recombinant human erythropoietin, the uremic environment, and blood transfusions.¹⁵

It has been suggested that glycated albumin may be a better marker for assessing glycemic control in patients with severe chronic kidney disease.¹⁶

Medications and supplements that affect hemoglobin

Drugs that may cause hemolysis could lower hemoglobin A_1c levels. Examples are dapsone, ribavirin, and sulfonamides. Other drugs can change the structure of hemoglobin. For example, hydroxyurea alters hemoglobin A into hemoglobin F, thus lowering the hemoglobin A_1c level. Chronic opiate use has been reported to increase hemoglobin A_1c levels through mechanisms yet unclear.

Aspirin, vitamin C, and vitamin E have been postulated to interfere with hemoglobin A_1c measurement assays, although studies have not been consistent in demonstrating these effects.

Labile diabetes

In some patients with diabetes, blood glucose levels are labile and oscillate between states of hypoglycemia and hyperglycemia, despite optimal hemoglobin A_1c levels.¹⁷ In these patients, the average blood glucose level may very well correlate appropriately with the glycated hemoglobin level, but the degree of control would not be acceptable. Fasting hyperglycemia or postprandial hyperglycemia, or both, especially in the setting of significant glycemic variability over the month before testing, may not be captured by the hemoglobin A_1c measurement. These glycemic excursions may be important, as data suggest that this variability may independently worsen microvascular complications in diabetic patients.¹⁸

ALTERNATIVES TO MEASURING THE GLYCATED HEMOGLOBIN

When hemoglobin A_1c levels are suspected to be inaccurate, other tests of the adequacy of glycemic control can be used.¹⁹

Continuous glucose monitoring is the gold standard and precisely shows the degree of glycemic variability, usually over 5 days. It is often used when hypoglycemia and wide fluctuations in within-day and day-to-day glucose levels are suspected. In addition, we believe that continuous monitoring could be used to confirm the validity of hemoglobin A_1c testing. In a clinical setting in which the level does not seem to match the fingerstick blood glucose readings, it can be a useful tool to assess the range and variation in glycemic control.

This method, however, is not practical in all diabetic patients, and it certainly does not have the same long-term predictive prognostic value. Yet it may still have a role in validating measures of long-term glycemic control (eg, hemoglobin A_1c). There is evidence that using continuous glucose monitoring periodically can improve glycemic control, lower hemoglobin A_1c levels, and lead to fewer hypoglycemic events.²⁰ As discussed earlier, patients who have labile glycemic excursions and higher risk of microvascular complications can still have “normal” hemoglobin A_1c levels; in this scenario, the use of continuous glucose monitoring can lead to lower risk and better control.

1,5-anhydroglucitol and fructosamine are circulating biomarkers that reflect short-term glucose control, ie, over 2 to 3 weeks. The higher the average blood glucose level, the lower the 1,5-anhydroglucitol level, since higher glucose levels competitively inhibit renal reabsorption of this molecule. However, its utility is limited in renal failure, liver disease, and pregnancy.

Fructosamines are nonenzymatically glycated proteins. As markers, they are reliable in renal disease but are unreliable in hypoproteinemic states such as liver disease, nephrosis, and lipemia. This group of proteins represents all of serum-stable glycated proteins; they are strongly influenced by the concentration of serum proteins, as well as by coexisting low-molecular-weight substances in the plasma.

Glycated albumin is superior to glycated hemoglobin in reflecting glycemic control, as it has a faster metabolic turnover than hemoglobin and is not affected by hemoglobin-opathies. Unlike fructosamines, it is not influenced by the serum albumin concentration. Moreover, it may be superior to the hemoglobin A_1c in patients who have postprandial hypoglycemia.²¹

Interestingly, recent cross-sectional analyses suggest that fructosamines and glycated albumin are at least as strongly associated with microvascular complications as the hemoglobin A_1c is.²²

BE ALERT TO FACTORS THAT AFFECT GLYCATED HEMOGLOBIN

Hemoglobin A_1c reflects exposure of red blood cells to glucose. Multiple factors—pathologic, physiologic, and environmental—can influence the glycation process, red blood cell turnover, and the hemoglobin structure in ways that can decrease the reliability of the hemoglobin A_1c measurement.

Clinicians should be vigilant for the various clinical situations in which hemoglobin A_1c is hard to interpret, and they should be familiar with alternative tests (eg, continuous glucose monitoring, 1,5-anhydroglucitol, fructosamines) that can be used to monitor adequate glycemic control in these patients.

No. Based on current evidence and guidelines, routine acid-suppressive therapy to prevent stress ulcers has no benefit in hospitalized patients outside the critical-care setting. Only critically ill patients who meet specific criteria, as described in the guidelines of the American Society of Health System Pharmacists, should receive acid-suppressive therapy.

Unfortunately, routine stress ulcer prophylaxis is common in US hospitals, unnecessarily putting patients at risk of complications and adding costs.

STRESS ULCER AND CRITICAL ILLNESS

Stress ulcers—ulcerations of the upper part of the gastrointestinal (GI) mucosa in the setting of acute disease—usually involve the fundus and body of the stomach. The stomach is lined with a glycoprotein mucous layer rich in bicarbonates, forming a physiologic barrier to protect the gastric wall from acid insult by neutralizing hydrogen ions. Disruption of this protective layer can occur in critically ill patients (eg, those with shock or sepsis) through overproduction of uremic toxins, increased reflux of bile salts, compromised blood flow, and increased stomach acidity through gastrin stimulation of parietal cells.

More than 75% of patients with major burns or cranial trauma develop endoscopic mucosal abnormalities within 72 hours of injury.¹ In critically ill patients, the risk of ulcer-related overt bleeding is estimated to be 5% to 25%. Furthermore, 1% to 5% of stress ulcers can be deep enough to erode into the submucosa, causing clinically significant GI bleeding, defined as bleeding complicated by hemodynamic compromise or a drop in hemoglobin that requires a blood transfusion.² In contrast, in inpatients who are not critically ill, the risk of overt bleeding from stress ulcers is less than 1%.³

ADDRESSING RISK

A multicenter prospective cohort study of 2,252 intensive care patients² reported two main risk factors for significant bleeding caused by stress ulcers: mechanical ventilation for more than 48 hours and coagulopathy, defined as a platelet count below 50 × 10⁹/L, an international normalized ratio greater than 1.5, or a partial thromboplastin time more than twice the control value.⁴ In hemodynamically stable patients receiving anticoagulation in a general medical or surgical ward, the risk of GI bleeding was low, and acid suppression failed to lower the rate of stress ulcer occurrence.³

Other risk factors include severe sepsis, shock, liver failure, kidney failure, burns over 35% of the total body surface, organ transplantation, cranial trauma, spinal cord trauma, history of peptic ulcer disease, and history of upper GI bleeding.^3,5,6 Steroid therapy is not considered a risk factor for stress ulcers unless it is used in the presence of another risk factor such as use of aspirin or nonsteroidal antiinflammatory drugs (NSAIDs).²

INDICATIONS FOR PROPHYLAXIS

Prophylaxis with a proton pump inhibitor (PPI) is indicated in specific conditions—ie, peptic ulcer disease, gastroesophageal reflux disease, chronic NSAID therapy, and Zollinger-Ellison syndrome—and to eradicate Helicobacter pylori infection.⁷ But in the United States, stress ulcer prophylaxis is overused in general-care floors despite the lack of supporting evidence.

The American Society of Health System Pharmacists guidelines recommend it in the intensive care unit for patients with any of the following: coagulopathy, prolonged mechanical ventilation (more than 48 hours), GI ulcer or bleeding within the past year, sepsis, a stay longer than 1 week in the intensive care unit, occult GI bleeding for 6 or more days, and steroid therapy with more than 250 mg of hydrocortisone daily.⁸ Hemodynamically stable patients admitted to general-care floors should not receive stress ulcer prophylaxis, as it only negligibly decreases the rate of GI bleeding, from 0.33% to 0.22%.⁹

WHY ROUTINE ULCER PROPHYLAXIS IS NOT FOR ALL HOSPITALIZED PATIENTS

Although stress ulcer prophylaxis is often considered benign, its lack of proven benefit, additional cost, and risk of adverse effects, including interactions with foods and other drugs, preclude using it routinely for all hospitalized patients.^10,11 Chronic use of PPIs has been associated with complications, as discussed below.

Infection

Acid suppression may impair the destruction of ingested microorganisms, resulting in overgrowth of bacteria.¹² Overuse of PPIs may increase the risk of several infections:

• Diarrhea due to Clostridium difficile¹²
• Community-acquired pneumonia, from increased microaspiration of overgrown microorganisms into the lung.¹²
• Spontaneous bacterial peritonitis in patients with cirrhosis,¹³ although the mechanism is not clear. (Small-bowel bacterial overgrowth is the hypothesized cause.)

Bone fracture

PPIs lower gastric acidity, and this can inhibit intestinal calcium absorption. Furthermore, PPIs may directly inhibit bone resorption by osteoclasts.¹⁴

Reduction in clopidogrel efficacy

PPIs may reduce the efficacy of clopidogrel as a result of competitive inhibition of cytochrome CYP2C19, which is necessary to metabolize clopidogrel to its active forms. Therefore, concomitant use of clopidogrel with omeprazole, esomeprazole, or other CYP2C19 inhibitors is not recommended.¹⁵

Nutritional deficiencies

The overgrown microorganisms consume cobalamin in the stomach, resulting in vitamin B₁₂ deficiency. Acid-suppressive therapy can also reduce the absorption of magnesium and iron.¹²

Unnecessary cost

Heidelbaugh and Inadomi¹⁶ reviewed the non-evidence-based use of stress ulcer prophylaxis in patients admitted to a large university hospital and estimated that it entailed a cost to the hospital of $111,791 over the course of a year.

WHICH ULCER PROPHYLAXIS SHOULD BE USED IN CRITICALLY ILL PATIENTS?

Studies have shown histamine-2 blockers to be superior to antacids and sucralfate in preventing stress ulcer and GI bleeding,^8,15 but no study has compared PPIs with sucralfate and antacids.

When indicated, an oral PPI is preferred over an oral histamine-2 blocker for GI prophylaxis.¹⁷ This practice is considered cost-effective and is associated with lower rates of stress ulcer and GI bleeding. In intubated patients, however, an intravenous histamine-2 blocker is preferable to an intravenous PPI.^3,8,11 Interestingly, no difference was reported between PPIs and histamine-2 blockers in terms of mortality rate or reduction in the incidence of nosocomial pneumonia.¹⁷

OUR RECOMMENDATION

Only critically ill patients who meet the specific criteria described here should receive stress ulcer prophylaxis. More effort is needed to educate residents, medical staff, and pharmacists about current guidelines. Computerized ordering templates and reminders to discontinue prophylaxis at discharge or step-down may decrease overall use, reduce costs, and limit potential side effects.¹⁸

No. Based on current evidence and guidelines, routine acid-suppressive therapy to prevent stress ulcers has no benefit in hospitalized patients outside the critical-care setting. Only critically ill patients who meet specific criteria, as described in the guidelines of the American Society of Health System Pharmacists, should receive acid-suppressive therapy.

Unfortunately, routine stress ulcer prophylaxis is common in US hospitals, unnecessarily putting patients at risk of complications and adding costs.

STRESS ULCER AND CRITICAL ILLNESS

Stress ulcers—ulcerations of the upper part of the gastrointestinal (GI) mucosa in the setting of acute disease—usually involve the fundus and body of the stomach. The stomach is lined with a glycoprotein mucous layer rich in bicarbonates, forming a physiologic barrier to protect the gastric wall from acid insult by neutralizing hydrogen ions. Disruption of this protective layer can occur in critically ill patients (eg, those with shock or sepsis) through overproduction of uremic toxins, increased reflux of bile salts, compromised blood flow, and increased stomach acidity through gastrin stimulation of parietal cells.

More than 75% of patients with major burns or cranial trauma develop endoscopic mucosal abnormalities within 72 hours of injury.¹ In critically ill patients, the risk of ulcer-related overt bleeding is estimated to be 5% to 25%. Furthermore, 1% to 5% of stress ulcers can be deep enough to erode into the submucosa, causing clinically significant GI bleeding, defined as bleeding complicated by hemodynamic compromise or a drop in hemoglobin that requires a blood transfusion.² In contrast, in inpatients who are not critically ill, the risk of overt bleeding from stress ulcers is less than 1%.³

ADDRESSING RISK

A multicenter prospective cohort study of 2,252 intensive care patients² reported two main risk factors for significant bleeding caused by stress ulcers: mechanical ventilation for more than 48 hours and coagulopathy, defined as a platelet count below 50 × 10⁹/L, an international normalized ratio greater than 1.5, or a partial thromboplastin time more than twice the control value.⁴ In hemodynamically stable patients receiving anticoagulation in a general medical or surgical ward, the risk of GI bleeding was low, and acid suppression failed to lower the rate of stress ulcer occurrence.³

Other risk factors include severe sepsis, shock, liver failure, kidney failure, burns over 35% of the total body surface, organ transplantation, cranial trauma, spinal cord trauma, history of peptic ulcer disease, and history of upper GI bleeding.^3,5,6 Steroid therapy is not considered a risk factor for stress ulcers unless it is used in the presence of another risk factor such as use of aspirin or nonsteroidal antiinflammatory drugs (NSAIDs).²

INDICATIONS FOR PROPHYLAXIS

Prophylaxis with a proton pump inhibitor (PPI) is indicated in specific conditions—ie, peptic ulcer disease, gastroesophageal reflux disease, chronic NSAID therapy, and Zollinger-Ellison syndrome—and to eradicate Helicobacter pylori infection.⁷ But in the United States, stress ulcer prophylaxis is overused in general-care floors despite the lack of supporting evidence.

The American Society of Health System Pharmacists guidelines recommend it in the intensive care unit for patients with any of the following: coagulopathy, prolonged mechanical ventilation (more than 48 hours), GI ulcer or bleeding within the past year, sepsis, a stay longer than 1 week in the intensive care unit, occult GI bleeding for 6 or more days, and steroid therapy with more than 250 mg of hydrocortisone daily.⁸ Hemodynamically stable patients admitted to general-care floors should not receive stress ulcer prophylaxis, as it only negligibly decreases the rate of GI bleeding, from 0.33% to 0.22%.⁹

WHY ROUTINE ULCER PROPHYLAXIS IS NOT FOR ALL HOSPITALIZED PATIENTS

Although stress ulcer prophylaxis is often considered benign, its lack of proven benefit, additional cost, and risk of adverse effects, including interactions with foods and other drugs, preclude using it routinely for all hospitalized patients.^10,11 Chronic use of PPIs has been associated with complications, as discussed below.

Infection

Acid suppression may impair the destruction of ingested microorganisms, resulting in overgrowth of bacteria.¹² Overuse of PPIs may increase the risk of several infections:

• Diarrhea due to Clostridium difficile¹²
• Community-acquired pneumonia, from increased microaspiration of overgrown microorganisms into the lung.¹²
• Spontaneous bacterial peritonitis in patients with cirrhosis,¹³ although the mechanism is not clear. (Small-bowel bacterial overgrowth is the hypothesized cause.)

Bone fracture

PPIs lower gastric acidity, and this can inhibit intestinal calcium absorption. Furthermore, PPIs may directly inhibit bone resorption by osteoclasts.¹⁴

Reduction in clopidogrel efficacy

PPIs may reduce the efficacy of clopidogrel as a result of competitive inhibition of cytochrome CYP2C19, which is necessary to metabolize clopidogrel to its active forms. Therefore, concomitant use of clopidogrel with omeprazole, esomeprazole, or other CYP2C19 inhibitors is not recommended.¹⁵

Nutritional deficiencies

The overgrown microorganisms consume cobalamin in the stomach, resulting in vitamin B₁₂ deficiency. Acid-suppressive therapy can also reduce the absorption of magnesium and iron.¹²

Unnecessary cost

Heidelbaugh and Inadomi¹⁶ reviewed the non-evidence-based use of stress ulcer prophylaxis in patients admitted to a large university hospital and estimated that it entailed a cost to the hospital of $111,791 over the course of a year.

WHICH ULCER PROPHYLAXIS SHOULD BE USED IN CRITICALLY ILL PATIENTS?

Studies have shown histamine-2 blockers to be superior to antacids and sucralfate in preventing stress ulcer and GI bleeding,^8,15 but no study has compared PPIs with sucralfate and antacids.

When indicated, an oral PPI is preferred over an oral histamine-2 blocker for GI prophylaxis.¹⁷ This practice is considered cost-effective and is associated with lower rates of stress ulcer and GI bleeding. In intubated patients, however, an intravenous histamine-2 blocker is preferable to an intravenous PPI.^3,8,11 Interestingly, no difference was reported between PPIs and histamine-2 blockers in terms of mortality rate or reduction in the incidence of nosocomial pneumonia.¹⁷

OUR RECOMMENDATION

Only critically ill patients who meet the specific criteria described here should receive stress ulcer prophylaxis. More effort is needed to educate residents, medical staff, and pharmacists about current guidelines. Computerized ordering templates and reminders to discontinue prophylaxis at discharge or step-down may decrease overall use, reduce costs, and limit potential side effects.¹⁸

No. Based on current evidence and guidelines, routine acid-suppressive therapy to prevent stress ulcers has no benefit in hospitalized patients outside the critical-care setting. Only critically ill patients who meet specific criteria, as described in the guidelines of the American Society of Health System Pharmacists, should receive acid-suppressive therapy.

Unfortunately, routine stress ulcer prophylaxis is common in US hospitals, unnecessarily putting patients at risk of complications and adding costs.

STRESS ULCER AND CRITICAL ILLNESS

Stress ulcers—ulcerations of the upper part of the gastrointestinal (GI) mucosa in the setting of acute disease—usually involve the fundus and body of the stomach. The stomach is lined with a glycoprotein mucous layer rich in bicarbonates, forming a physiologic barrier to protect the gastric wall from acid insult by neutralizing hydrogen ions. Disruption of this protective layer can occur in critically ill patients (eg, those with shock or sepsis) through overproduction of uremic toxins, increased reflux of bile salts, compromised blood flow, and increased stomach acidity through gastrin stimulation of parietal cells.

More than 75% of patients with major burns or cranial trauma develop endoscopic mucosal abnormalities within 72 hours of injury.¹ In critically ill patients, the risk of ulcer-related overt bleeding is estimated to be 5% to 25%. Furthermore, 1% to 5% of stress ulcers can be deep enough to erode into the submucosa, causing clinically significant GI bleeding, defined as bleeding complicated by hemodynamic compromise or a drop in hemoglobin that requires a blood transfusion.² In contrast, in inpatients who are not critically ill, the risk of overt bleeding from stress ulcers is less than 1%.³

ADDRESSING RISK

A multicenter prospective cohort study of 2,252 intensive care patients² reported two main risk factors for significant bleeding caused by stress ulcers: mechanical ventilation for more than 48 hours and coagulopathy, defined as a platelet count below 50 × 10⁹/L, an international normalized ratio greater than 1.5, or a partial thromboplastin time more than twice the control value.⁴ In hemodynamically stable patients receiving anticoagulation in a general medical or surgical ward, the risk of GI bleeding was low, and acid suppression failed to lower the rate of stress ulcer occurrence.³

Other risk factors include severe sepsis, shock, liver failure, kidney failure, burns over 35% of the total body surface, organ transplantation, cranial trauma, spinal cord trauma, history of peptic ulcer disease, and history of upper GI bleeding.^3,5,6 Steroid therapy is not considered a risk factor for stress ulcers unless it is used in the presence of another risk factor such as use of aspirin or nonsteroidal antiinflammatory drugs (NSAIDs).²

INDICATIONS FOR PROPHYLAXIS

Prophylaxis with a proton pump inhibitor (PPI) is indicated in specific conditions—ie, peptic ulcer disease, gastroesophageal reflux disease, chronic NSAID therapy, and Zollinger-Ellison syndrome—and to eradicate Helicobacter pylori infection.⁷ But in the United States, stress ulcer prophylaxis is overused in general-care floors despite the lack of supporting evidence.

The American Society of Health System Pharmacists guidelines recommend it in the intensive care unit for patients with any of the following: coagulopathy, prolonged mechanical ventilation (more than 48 hours), GI ulcer or bleeding within the past year, sepsis, a stay longer than 1 week in the intensive care unit, occult GI bleeding for 6 or more days, and steroid therapy with more than 250 mg of hydrocortisone daily.⁸ Hemodynamically stable patients admitted to general-care floors should not receive stress ulcer prophylaxis, as it only negligibly decreases the rate of GI bleeding, from 0.33% to 0.22%.⁹

WHY ROUTINE ULCER PROPHYLAXIS IS NOT FOR ALL HOSPITALIZED PATIENTS

Although stress ulcer prophylaxis is often considered benign, its lack of proven benefit, additional cost, and risk of adverse effects, including interactions with foods and other drugs, preclude using it routinely for all hospitalized patients.^10,11 Chronic use of PPIs has been associated with complications, as discussed below.

Infection

Acid suppression may impair the destruction of ingested microorganisms, resulting in overgrowth of bacteria.¹² Overuse of PPIs may increase the risk of several infections:

• Diarrhea due to Clostridium difficile¹²
• Community-acquired pneumonia, from increased microaspiration of overgrown microorganisms into the lung.¹²
• Spontaneous bacterial peritonitis in patients with cirrhosis,¹³ although the mechanism is not clear. (Small-bowel bacterial overgrowth is the hypothesized cause.)

Bone fracture

PPIs lower gastric acidity, and this can inhibit intestinal calcium absorption. Furthermore, PPIs may directly inhibit bone resorption by osteoclasts.¹⁴

Reduction in clopidogrel efficacy

PPIs may reduce the efficacy of clopidogrel as a result of competitive inhibition of cytochrome CYP2C19, which is necessary to metabolize clopidogrel to its active forms. Therefore, concomitant use of clopidogrel with omeprazole, esomeprazole, or other CYP2C19 inhibitors is not recommended.¹⁵

Nutritional deficiencies

The overgrown microorganisms consume cobalamin in the stomach, resulting in vitamin B₁₂ deficiency. Acid-suppressive therapy can also reduce the absorption of magnesium and iron.¹²

Unnecessary cost

Heidelbaugh and Inadomi¹⁶ reviewed the non-evidence-based use of stress ulcer prophylaxis in patients admitted to a large university hospital and estimated that it entailed a cost to the hospital of $111,791 over the course of a year.

WHICH ULCER PROPHYLAXIS SHOULD BE USED IN CRITICALLY ILL PATIENTS?

Studies have shown histamine-2 blockers to be superior to antacids and sucralfate in preventing stress ulcer and GI bleeding,^8,15 but no study has compared PPIs with sucralfate and antacids.

When indicated, an oral PPI is preferred over an oral histamine-2 blocker for GI prophylaxis.¹⁷ This practice is considered cost-effective and is associated with lower rates of stress ulcer and GI bleeding. In intubated patients, however, an intravenous histamine-2 blocker is preferable to an intravenous PPI.^3,8,11 Interestingly, no difference was reported between PPIs and histamine-2 blockers in terms of mortality rate or reduction in the incidence of nosocomial pneumonia.¹⁷

OUR RECOMMENDATION

Only critically ill patients who meet the specific criteria described here should receive stress ulcer prophylaxis. More effort is needed to educate residents, medical staff, and pharmacists about current guidelines. Computerized ordering templates and reminders to discontinue prophylaxis at discharge or step-down may decrease overall use, reduce costs, and limit potential side effects.¹⁸