You are taking care of a 65-year-old man with Type 1 diabetes, which is well controlled using an insulin pump. Unfortunately, he was recently admitted with his second attack of diverticulitis and is now on your service for an elective sigmoidectomy. His surgery is uncomplicated, but now you have to write his postoperative orders.
1. Is glycemic control really that important for patients after surgery? Why or why not?
2. What types of insulin does a surgical patient require?
Diabetes is very common in hospitalized patients and inpatient hyperglycemia has been associated with an increase in overall infection rate, morbidity, mortality, and length of stay in surgical patients. These complications are probably because hyperglycemia triggers phagocyte and endothelial cell dysfunction, as well as increased vascular inflammation, platelet activation, and oxidative stress. Exogenous insulin administration not only decreases blood glucose levels but may also have a direct anti-inflammatory effect on vascular endothelial cells. However, overaggressive glycemic management can lead to hypoglycemia with possible coma, neurological injury, and death. In short, while hypoglycemia is more dangerous than hyperglycemia, both are bad. Therefore, it is essential that you understand how to properly manage perioperative insulin dosages.
In broad terms, the easiest way to think about insulin requirements is the concept that inpatients require a basal or baseline amount of insulin and then a prandial or nutritional requirement (see Figure 42-1). The baseline amount is the quantity of insulin that patients need to avoid unchecked gluconeogenesis and ketogenesis. The prandial amount is the quantity of insulin needed to cover meals, dextrose in intravenous fluids, enteral feeds, and/or TPN. If the patient is eating, then ideally the prandial amount is given as a correction-dose therapy before or between meals. Sliding insulin scales are substandard for this purpose since the dosage of insulin is given without regard to meals and after hyperglycemia has already occurred. If the patient is NPO and on a continuous infusion of intravenous fluids that contain dextrose, then sliding insulin scales may be sufficient to cover nutritional insulin requirements, although they should be adjusted daily until optimal glycemic control is achieved.
By definition, these patients are insulin deficient and therefore require a constant basal supply of insulin to avoid entering diabetic ketoacidosis. Adult Type 1 diabetics are frequently very familiar with how much insulin their bodies require and are very comfortable recognizing sensations of hyperglycemia or hypoglycemia. Often these patients will be able to subcutaneously administer insulin to themselves via an insulin pump that lets them control the precise dosage of insulin administered to their bodies. In my experience, it is best to work/negotiate with these patients and let them control their own insulin delivery. If they are eating, these patients should be on a long-acting insulin (such as NPH or lente) that they administer in the morning or ...