Tight glucose control is an area of controversy in critical care. A normal fasting blood glucose levels range between 70 and 100mg/dl, in persons who are healthy. According to Kasper et al., 2015, Critically ill patients frequently have higher blood glucose levels and based on several conducted retrospective analyses it has shown that the mortality rate for these patients is higher compared to those who have normal blood glucose levels. Hyperglycemia, as well as insulin resistance, are two of the prevailing conditions in critically ill patients, even if a patient has not been previously diagnosed with diabetes. It has been reported that insulin resistance and pronounced hyperglycemia in critically ill patients may lead to complications such as multiple organ failure and the severity of this “diabetes stress” eventually reflects the risk of death. Although one study showed a significant mortality benefit when glucose levels were aggressively normalized in a large group of surgical ICU patients, more recent data for a large population of both medical and surgical ICU patients suggested that tight glucose control resulted in increased rates of mortality, Berghe, 2004 reiterated. In recent studies that were conducted, it was shown that prevention of hyperglycemia in critically ill patients through intensive insulin management has substantially improved patient outcomes.
Insulin resistance and hyperglycemia in the critically ill
Berghe, 2004 also emphasized that it is well known today that any illness or injury may result in insulin resistance, glucose tolerance, and hyperglycemia, a constellation termed as “diabetes injury.” Illness from diseases or trauma in within the body increases hepatic glucose production with ongoing gluconeogenesis despite hyperglycemia and abundantly released insulin as described by Kasper et al., 2015. Hepatic insulin resistance is further characterized by elevated circulating levels of IGF-binding protein 1 (IGFBP-1). Impairment of the insulin-stimulated glucose uptake is also seen in skeletal and heart muscles. Overall, glucose uptake in critically ill patients, however, is increased but takes place mainly in tissues that are not dependent on the utilization of insulin for glucose uptakes such as the nervous system and blood cells. Most of the severe cases of these stress-induced hyperglycemia and highest levels of circulating IGFBP-1 are seen in patients who present the highest risk of death.
Blood Glucose Monitoring
In some established institutions, if the blood glucose of patients is greater than 180mg/dl, patients are then started insulin therapy by continuous delivery of the medication intravenously (IV). To monitor the patient’s condition and their response with insulin therapy, these patient’s blood glucose levels are monitored on an hourly basis via a point of care glucometer to titrate the patient’s existing insulin drip. Several blood sample collection techniques can be used to monitor a patient’s blood sugar.
In one study between conventional and intensive insulin treatment by Berghe et al, 2001, wherein the conventional insulin treatment (continuous infusion 50 IU of Actrapid HM in 50ml 0.09 % Sodium Chloride with the use of a pump) was started only if the blood glucose level exceeded 215mg per deciliter, and the infusion was adjusted to maintain a level between 180 and 200 mg per deciliter (10.0 and 11.1 mmol per liter) in critically ill patients. In the intensive-treatment group, an insulin infusion was started if the blood glucose level exceeded 110mg per deciliter, and the insulin infusion was then adjusted to maintain normoglycemia (80 to 110mg per deciliter 4.4 to 6.1 mmol per liter). Early trials showed that achieving normoglycemia (4.4 to 6.1?mmol/L) in cardiac surgery patients or patients in postoperative surgical ICU settings reduced mortality. However, subsequent trials in mixed populations of critically ill patients did not show a benefit of targeting a blood glucose level of 4.4 to 8.3?mmol/L. The study also revealed that hypoglycemia (blood glucose level of 40mg per deciliter 2.2mmol per liter or less) occurred in 39 patients in the intensive-treatment group and only 6 percent in the conventional-treatment groups.
Clinical Benefits for Intensive Insulin therapy in critical illness
Titrating insulin infusion during intensive care to strict normoglycemia (below 110mg/dl) strikingly reduced mortality when compared with the conventional insulin treatment approach according to the Leuven study of critically ill patients in which majority of whom did not have a history of diabetes. It was apparent in the study that patients with a prolonged critical illness who required longer intensive care of more than five days benefited more with intensive insulin therapy in the ICU wherein mortality rate showed a reduction from 20.2% down to 10.6%. As further emphasized by Urden et al., 2018, the intensive insulin therapy prevented complications such as nosocomial infections, multiple organ failures, critical illness polyneuropathy, muscle weakness and anemia, therefore, reducing the number of days that the patient is dependent on intensive care in return it increases and confirms the survival benefits of implementing tight blood glucose control with insulin into clinical practice. Despite the drawback of having a slightly higher incidence of hypoglycemia compared to the conventional insulin therapy approach, the utilization of a titration algorithm guaranteed that whenever hypoglycemia occurred, it was always quickly resolved. This substantial improvement in patient outcome with the aid of simple measure was considered to be major progress in the field of intensive care.
The vigilance of the critical care nurse is necessary for the success of any intervention to lower and control blood glucose levels with the aid of a continuous insulin infusion. The results of clinical studies such as those performed by Leuven and other researches showed that simple metabolic intervention, maintaining normoglycemia or blood glucose below 110mg per deciliter with the aid of insulin, improved survival and reduced morbidity of critically ill patients within the intensive care units. As a result of the studies conducted, clinical practice guidelines were then developed by the American Association of Clinical Endocrinologists and the American Diabetes Association that recommend the use of continuous insulin infusions to maintain blood glucose levels in a critically ill patient in a range of 140 to 180 mg per deciliter with hourly monitoring. This range has been selected to reduce the risk of occurrence of hypoglycemia while also trying to avoid extreme hyperglycemia brought up by insulin resistance or glucose intolerance which is the body’s response to acute illnesses or injury.
Therefore, the majority of the healthcare institutions has developed an institution-specific glucose-insulin algorithm that they may utilize in their practice that would help lower the blood glucose levels of critically ill patients into a targeted range.