The patient with diabetes, whether insulin-dependent, on oral or injectable diabetes medications, or diet-controlled, has an excess risk of perioperative complications. A medical assessment of any complications of the patient's diabetes is essential before considering surgery. Intractable problems with hypertension, coronary heart disease, nephropathy or autonomic neuropathy, should be warnings to the surgical team to consider consultation with appropriate specialists as part of the preoperative planning.
Repeated hypoglycemic attacks, recurrent admission to hospital with diabetes complications, inability to measure blood glucose at home, or general lack of understanding of the patient's responsibilities for self-care, should prompt a pre-op assessment by a diabetes educator.
Pre-op planning for the patient with diabetes must include clarification of who's going to manage the blood glucose level during the perioperative period. Someone must be identified in advance, and that person must have the knowledge and experience to write appropriate orders for controlling the diabetes, and must be available to advise on adjusting the orders if things get out of hand for any reason.
Patients who smoke or use tobacco should be advised to stop several weeks before surgery. Tobacco use increases the risk of surgical and anesthesia complications. Smokers suffer from more respiratory ailments than non-smokers; smokers require more supplemental oxygen during surgery and may need assistance with breathing following surgery.
Metformin, a commonly-used medication for T2DM, should be stopped pre-operatively, as having metformin on board during surgery increases the risk of a potentially-fatal complication called lactic acidosis. The patient must be asked if they have been on metformin (or combination medications that include metformin). Metformin therapy should be temporarily suspended for any surgical procedure (except minor procedures not associated with restricted intake of food and fluids) and should not be restarted until the patient's oral intake has resumed and renal function has been evaluated as normal.
The patient should bring their blood sugar meter to the hospital on the day of the surgery. If there are long delays, self-checking of blood glucose (blood glucose) levels, perhaps as often as hourly, will allow the surgical team to know if unexpected pre-op changes in glucose level occur.
Although many patients frequently have their oral intake stopped at midnight before surgery, even if the surgery is scheduled for mid-afternoon, this is inappropriate for people with diabetes, as it risks dehydration, and indeed if diabetes pills or insulin therapy is withheld due to outdated pre-op protocols, compounds the risks of dehydration with a risk of hyperglycemia. There should be modification of the "NPO at midnight" instruction if surgery will be in the mid-day or afternoon hours to minimize the NPO period to 4-6 hours, depending on anesthetic needs. Similarly, patients with diabetes should be scheduled as "first case" whenever possible to minimize the time that they are NPO. When use of an intravenous insulin infusion is planned, it may be helpful for the patient to be second, rather than first on the operating list, to allow more time to set up the infusion.
Any diabetic patient arriving at the surgical setting with a blood glucose significantly higher than usual (above 300 mg/dl in patients not doing home glucose monitoring) should be checked for the likely cause of the hyperglycemia (infections and non-compliance with starvation instructions are the among the likely explanations). Consideration should be given to postponing the surgery in such cases.
The time-honored tradition to withhold medications on the morning of surgery is sometimes inappropriate, and diabetic glycemic medications should not be routinely omitted on the morning of surgery. For patients on insulin, whether to adjust the usual doses depends on the insulin program: if the only morning insulin is a short-acting insulin (Humalog, Novolog, Apidra or Regular), withholding it is totally inappropriate as the patient will become insulin deficient and hyperglycemic. If the patient is on longer-acting insulins such as NPH or Lantus or Levemir insulin, the doses of these insulins might be continued unchanged (especially for Lantus, which is such a long-lasting product that doses can usually be continued unchanged). The patient's usual diabetes team should be asked what they would advise about morning medications, as the decision will depend on the medication and the expected period of time before the patient is again eating well.
Patients who use insulin pumps, especially those who also use continuous-glucose monitoring devices, should have specific orders written to allow them to control the rate of insulin delivery through the pump whenever the patient is alert and oriented. The pump should never be discontinued unless adequate intravenous access for fluids and insulin have been established, and a protocol for frequent blood glucose monitoring and adjustment of intravenous insulin doses is in place to substitute for the patient's program.
Whenever possible, the patient should be managed with local anesthesia as this may remove the need for the patient to starve pre-operatively. Avoidance of general anesthesia can also help to reduce post-operative nausea and vomiting. Where general anesthesia is employed, careful technique aimed at reducing post-operative vomiting is essential.
If general anesthetic will be used, even for a short period of time, an intravenous line to give fluids and minerals and dextrose as needed is mandatory, and the patient may also need insulin by continuous intravenous infusion if glucose levels are elevated.
If a general anesthetic will be used, it should be clear as to who will be checking the patient's blood glucose levels in the OR and recovery room. It is inappropriate for a blood specimen to be sent to the hospital laboratory for a "STAT blood glucose" if glucose meters are available (unless the meter displays an inconsistent result); blood glucose meters should definitely be in the OR, and someone should be trained in their use; and the appropriate control solutions run regularly to verify that the meter is correctly calibrated.
For people with diabetes, especially those who take insulin, post-op care obviously should include orders for frequent blood glucose testing, and appropriate insulin administration. For people who are alert and knowledgeable, it would usually be appropriate to allow the patient to check their own blood glucose and give their own insulin injections.