Nearly 10% of the U.S. population now has diabetes, and the American Diabetes Association estimates another 30% is pre-diabetic, making it likely you'll encounter diabetic patients with greater frequency. We know surgical stress response can lead to short-term resistance to insulin, which in turn causes hyperglycemia. During surgery, hyperglycemia can cause dehydration, fluid shifts, electrolyte abnormalities, a predisposition to infection and impaired wound healing. For patients undergoing major surgery, these occurrences may be associated with increased perioperative morbidity and mortality. While insufficient evidence exists to provide strong recommendations regarding glycemic control specifically for outpatient surgery, here are steps we can take to ward off diabetic complications.
Determine the following pre-operatively:
- level of glycemic control based on blood glucose levels and, ideally, HbA1c;
- type (oral antidiabetics and/or insulin) and dose of antidiabetic therapy in use;
- frequency and symptoms of hypoglycemia;
- the blood glucose level at which hypoglycemic symptoms occur;
- hospital admissions that have come about from glycemic control issues; and
- the patient's ability to test blood glucose levels.
Diabetic patients should land as early in the schedule as possible, so they fast for less than 12 hours and miss no more than 1 meal.
Hypoglycemia isn't generally a worry in patients on oral antidiabetics; it occurs only rarely with sulfonylureas, meglitinides and non-insulin injectables. Patients should continue use of these drugs, including metformin, until the day before but not on the day of surgery.
Pre-operative patient preparation
Provide patients with instructions for handling their insulin regimens leading up to surgery (see table for dosing-instruction guidelines). Instruct them to bring all their diabetes medications, including insulin, with them on the day of surgery, and to travel with glucose tablets or a sugary drink in case of post-op hypoglycemia. When the patient arrives, make sure she hasn't consumed the tablets or drink en route, nor anything else barred by your general NPO instructions.
Pre-operative decision to proceed
There isn't a specific pre-op blood glucose level above which surgery should be postponed; however, you should always consider comorbidities and the risk of surgical complications. Postpone surgery if the patient is suffering significant complications of hyperglycemia, such as severe dehydration, ketoacidosis and hyperosmolar non-ketotic states, on the morning of surgery. If the patient is only hyperglycemic, proceed with a plan for perioperative glycemic control.
Intraoperative monitoring and prevention
In patients with well-controlled diabetes, intraoperative blood glucose levels should be maintained at less than 180mg/dl. Don't try to acutely decrease (normalize) the level in the chronically elevated patient. To maintain optimal blood glucose in the first set of patients, administer subcutaneous rapid-acting insulin analogs perioperatively using the "rule of 1,800 or 1,500." This is meant to represent the ratio of expected decrease in blood glucose with each unit of insulin used. For example, if a patient's daily insulin dose is 60 units, 1 unit of insulin would reduce the blood glucose level by 25 to 30mg (for example, 1,800/60 or 1,500/60).
Enact PONV-prevention protocols, as patients with diabetes are more prone to post-op nausea, and need to return to normal feeding more quickly, to prevent glycemic complications. You can use dexamethasone 4mg, but you should follow it with appropriate monitoring of blood glucose levels.
Perioperative blood glucose monitoring and management
Check blood glucose levels upon the patient's arrival to the facility and before discharge home. Perform intraoperative blood glucose monitoring every 1 to 2 hours, depending on the procedure duration (generally, longer than 2 hours) and insulin type used. For patients who have received insulin and those with lower blood glucose levels, monitor more often as appropriate.
Blood glucose under 70mg/dl (4.0mmol/l) is an alert value for hypoglycemia. If the patient is symptomatically hypoglycemic, have the patient consume 15 to 20gm of glucose, repeated until blood glucose rises and symptoms resolve. Avoid overzealous glucose administration, as hyperglycemia can lead to post-op complications.
Aim for blood glucose levels in the ideal range before discharge. Observe patients until the possibility of hypoglycemia from perioperatively administered insulin has been ruled out.
Instruct patients to check blood glucose levels frequently while fasting. Remind them to use their hypoglycemia treatments if they begin to feel symptomatic. Advise them to delay transition to daily pre-op antidiabetic regimens if normal caloric intake is delayed.
Insulin Regimens in Diabetic Patients
|Insulin Regimen||Day Before Surgery||Day of Surgery|
|Insulin pump||No change; use "sick day" or "sleep" basal rates||No change; use "sick day" or "sleep" basal rates|
|Long-acting, peakless insulins||75% of evening dose if history of nocturnal or morning hypoglycemia is present||75% to 100% of morning dose, administered upon arrival to the facility|
|Intermediate-acting insulins||No change in the daytime dose; 75% of evening dose if history of nocturnal or morning hypoglycemia is present||50% to 75% of morning dose, administered upon arrival|
|Fixed combination insulins||75% of evening dose if history of nocturnal or morning hypoglycemia is present||50% to 75% of morning dose of intermediate-acting component; neutral protamine Hagedorn in place of lispro-protamine|
|Short- and rapid-acting insulin||No change||Hold the dose|
|Non-insulin injectables||No change||Hold the dose|
Adapted from the Society for Ambulatory Anesthesia's Consensus Statement on Perioperative Blood Glucose Management in Diabetic Patients Undergoing Ambulatory Surgery.