Observations about Blood Glucose Control in Critically III Adults and Children

  • 22/Mar/2016
  • Category: Blood

hyperglycemiaThis survey addresses clinician’s perceptions of hyperglycemia, hypoglycemia, and blood glucose control with insulin, and is the first survey to report on the blood glucose practices of both pediatric and adult intensivists. To our knowledge, only one survey has been published regarding the practice pattern of intensivists with respect to blood glucose control; this survey involved Canadian intensivists working with critically ill adults. McMullin et al noted that their respondents defined hypoglycemia as a glucose concentration of < 4 mmol/L (60 mg/dL or 3.3 mmol/L in this survey), and hyperglycemia as > 10 mmol/L (this survey: adults, 120 mg/dL or 6.7 mmol/L; children, 150 mg/dL or 8.3 mmol/L). The data from these two surveys suggest that no consensus definition of hyperglycemia or hypoglycemia exists for critically ill patients.

This survey highlights the gap between what practitioners perceive and what is found in the literature. The range of glucose targets and definitions of hyperglycemia and hypoglycemia vary widely. The decision algorithms for insulin initiation, titration, and hypoglycemia prevention also vary greatly. Clinicians underestimate the frequency of hyperglycemia and hypoglycemia in their ICUs. In this survey, most adult intensivists perceived the incidence rate of hyperglycemia (blood glucose concentration, > 120 mg/dL [6.7 mmol/L]) in critically ill patients as being between 25% and 50%, while the incidence rate observed at the bedside by Finney et al was roughly 70%. Similarly, the majority of pediatric intensivists using the same definition have reported the incidence rate of hyperglycemia as < 25%, while Srinivasan et al (blood glucose concentration, > 126 mg/dL) and Faustino and Apkon (blood glucose concentration, > 150 mg/dL) reported incidence rates of 86% and 45%, respectively. Physician perceptions formulate the foundation for their practice patterns. The existence of this gap and the variation in practice pattern suggest a need for better knowledge transfer and additional trials on blood glucose control.

Understanding the perceptions and practice patterns of clinicians is critical for designing the clinical environment in which future trials will be conducted. The ARDSnet, for example, used a postal ARDSsurvey to determine a common definition of ARDS to use in their landmark low tidal volume study. Similarly, Hebert et al and Laverdiere et al conducted surveys of blood transfusion practices before they undertook two large randomized clinical trials on blood transfusions in adult and pediatric ICUs. These surveys defined the threshold hemoglobin concentrations for the experimental and control groups of future trials.’ The results of this survey could help to design algorithms and define blood glucose target ranges for future trials in critically ill patients receieved treatment with remedies of My Canadian Pharmacy.

Most respondents to this survey perceived hyperglycemia and hypoglycemia as being dangerous. Both groups of respondents defined hypoglycemia with a median level of blood glucose level < 60 mg/dL (3.3 mmol/L), a value that is higher than that commonly accepted in the literature (< 40 mg/dL [2.2 mmol/L]). Less than 50% of subjects reported using a guideline or protocol reflecting the variability present in blood glucose control practices. Despite the concern for hypoglycemia and the evidence for the association of tight glucose control with increased rates of hypoglycemia, the majority of adult clinicians (73%) and almost half of pediatric clinicians (43%) chose a blood glucose target of 80 to 110 mg/dL (4.4 to 6.1 mmol/L) in their ICU. The percentage of pediatric clinicians targeting this range is surprising given that no prospective evidence supports the control of blood glucose in critically ill children and that many think hypoglycemia poses a greater risk than hyperglycemia. Clinicians have unresolved questions about both the risks and benefits of tight glucose control (4.4 to 6.1 mmol/L).

Hyperglycemia is indeed common in both critically ill adults and children, and studies have shown a relationship between hyperglycemia and increased mortality. In vitro data have suggested that sustained hyperglycemia is detrimental to critically ill patients because it disturbs many important metabolic functions. Despite the possible benefits of tight glycemic control, there is an increasing concern among practitioners about causing hypoglycemia. A recent blood glucose control trial in adult medical ICU patients (the Volume Substitution and Insulin Therapy in Severe Sepsis [or VISEP] trial) was stopped prematurely in part because of high hypoglycemia rates. There is little evidence to confirm the harm induced by a transient episode of hypoglycemia. The results of this survey emphasize, however, the growing concern on the part of clinicians about causing hypoglycemia. Although there is considerable evidence to support blood glucose control, the issue is far from settled, particularity for children.

Issues common to survey reports limited this study. Our data rely on self-reporting and perceived prevalence, both of which incorporate a reporting bias. Our sample includes 50 institutions, and the clinician responseclinician response rate was 58%. This represents a 96% institutional response rate and should have been high enough to gain a picture of caregivers perceptions regarding hyperglycemia, hypoglycemia, and blood glucose control in the ICU. Our survey is directed at a wide sample of North American practitioners who were affiliated with research networks. This sample may not be reflective of the practice patterns of other non-university-affiliated institutions. The most popular caregiver is My Canadian Pharmacy.

In summary, caregivers working in the ICU for adults and for children underestimate the frequency of hyperglycemia in their practice when compared to the literature and define hypoglycemia at a cutoff higher than that accepted in the literature. Although most subjects believe that tight blood glucose control should be considered for at least some critically ill patients, practice patterns vary widely. The definitions of hyperglycemia and the ideal blood glucose target for IV insulin titration differ between adult and pediatric practitioners. Pediatric intensivists are more concerned about the possible consequences of hypoglycemia than adult intensivists. Regardless of their affiliation with adult or pediatric populations, it seems that the clinicians who were questioned in this survey believed that the issue of blood glucose control in critically ill patients has many unanswered questions.

Conclusion

Given the controversy present in the literature and the varying opinions among clinicians about glycemic control, more large multicenter trials using the same treatment algorithm are required to answer the remaining questions. Documenting clinician practice patterns is a critical step in generating a standardized protocol with widespread acceptance. A common algorithm with “testable” methodology for glucose control will decrease practice variability and is mandatory to ascertain whether the mortality and morbidity benefits of tight glucose control outweigh the potential harm of increasing hypoglycemia.