THE PATIENT WITH DIABETES UNDERGOING SURGERY
During periods of physiologic stress such as surgery, blood glu-cose levels tend to rise as a result of an increase in the level of stress hormones (epinephrine, norepinephrine, glucagon, cortisol, and growth hormone). If hyperglycemia is not controlled during surgery, the resulting osmotic diuresis may lead to excessive loss of fluids and electrolytes. Patients with type 1 diabetes also risk developing ketoacidosis during periods of stress.
Hypoglycemia is also a concern in diabetic patients under-going surgery. This is especially a concern during the preoperative period if surgery is delayed beyond the morning in a patient who received a morning injection of intermediate-acting insulin.
There are various approaches to managing glucose control during the perioperative period. Frequent capillary glucose mon-itoring is essential throughout the preoperative and postoperative periods, regardless of the method used for glucose control. Ex-amples of these approaches are as follows, although the use of IV insulin and dextrose has become widespread with the increased availability of meters for intraoperative glucose monitoring:
· The morning of surgery, all subcutaneous insulin doses are withheld (unless the blood glucose level is elevated—for ex-ample, more than 200 mg/dL [11.1 mmol/L], in which case a small dose of subcutaneous regular insulin may be pre-scribed). The blood glucose level is controlled during surgery with the IV infusion of regular insulin, which is balanced by an infusion of dextrose. The insulin and dextrose infusion rates are adjusted according to frequent (hourly) capillary glucose determinations. After surgery, the insulin infusion may be continued until the patient can eat. If IV insulin is discontinued, subcutaneous regular insulin may be admin-istered at set intervals (every 4 to 6 hours), or intermediate-acting insulin may be administered every 12 hours with supplemental regular insulin as necessary until the patient is eating and the usual pattern of insulin dosing is resumed. The nurse caring for a patient with diabetes who is receiv-ing IV insulin must carefully monitor the insulin infusion rate and blood glucose levels. IV insulin has a much shorter duration of action than subcutaneous insulin. Thus, if the infusion is interrupted or discontinued, hyperglycemia will develop rapidly (within 1 hour in type 1 diabetes and within a few hours in type 2 diabetes). The nurse must ensure that subcutaneous insulin is administered 30 minutes before dis-continuing the IV insulin infusion.
· One half to two thirds of the patient’s usual morning dose of insulin (either intermediate-acting insulin alone or both short- and intermediate-acting insulins) is administered subcutaneously in the morning before surgery. The remain-der is then administered after surgery.
· The patient’s usual daily dose of subcutaneous insulin is divided into four equal doses of regular insulin. These are then administered at 6-hour intervals. The last two ap-proaches do not provide the control achieved by IV admin-istration of insulin and dextrose.
· Patients with type 2 diabetes who do not usually take insulin may require insulin during the perioperative period to con-trol blood glucose elevations. Patients who are taking chlor-propamide, a long-acting oral antidiabetic agent, may be instructed to discontinue the oral agent 24 to 48 hours before surgery. Some of these patients may resume their usual regimen of diet and oral agent during the recovery pe-riod. Other patients (whose diabetes is probably not well controlled with diet and an oral antidiabetic agent before surgery) need to continue with insulin injections after dis-charge.
· For patients with type 2 diabetes who are undergoing minor surgery but who do not normally take insulin, glucose levels may remain stable provided no dextrose is infused during the surgery. After surgery, they may require small doses of regular insulin until the usual diet and oral agent are resumed.
During the postoperative period, diabetic patients must also be closely monitored for cardiovascular complications because of the increased prevalence of atherosclerosis in patients with dia-betes, wound infections, and skin breakdown (especially in the patient with decreased pain sensation in the extremities due to neuropathy). Maintaining adequate nutrition and blood glucose control promotes wound healing.
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