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Jean-Marie Ekoé, M.D., FRCPC
Section of Endocrinology, Department of Medicine,
Centre Hospitalier de l'Université de Montréal
Montreal, QC Introduction
Surgical stress induces a complex series of hormonal and metabolic changes. These changes predominantly result in enhanced catabolism which may lead to dangerous hyperglycemia and ketosis. Successful management of surgery in persons with diabetes requires simple and safe protocols that should be understood by all staff1.
Management of the individual patient is determined by the severity and nature of surgical trauma, the duration of perioperative fasting and the capacity of the patient's insulin reserves. Insulin treated individuals, most of whom have type 1 diabetes mellitus, will require exogenous insulin administration. By contrast, subjects treated with oral agents have at least some residual B-cell function (type 2 diabetes mellitus) and need insulin treatment only for major surgery. Simple observation is generally sufficient. The essentials for perioperative management are to ensure reasonable glycemic control.
Surgery in Patients Not Treated with Insulin
Glycemic control should be monitored carefully during the period before admission. Shorter acting sulfonylureas should be prescribed and long-acting sulfonylureas such as chlopropamide should be stopped at least nine days before surgery. These patients should be evaluated before surgery.
Patients who achieve good control (fasting blood glucose < 7 mmol/L., other values < 10 mmol/L) and who will undergo a minor procedure generally require only close observation1. Surgery should be scheduled for the morning if possible. Breakfast and any morning dose of oral hypoglycemic agent are omitted. Throughout the perioperative period, frequent glycemic monitoring is required and glucose containing fluids must be avoided. Oral agents should be restarted with the first postoperative meal. Patients with type 2 diabetes, undergoing major surgery that requires prolonged fasting, are best managed using continuous glucose and insulin delivery as for patients with type 1 diabetes. Persons with type 2 diabetes, who have suboptimal glycemic control and who do not achieve the above glycemic targets, should also be managed in this fashion.
Surgery in Persons with Diabetes Managed with Insulin
Uncertainty over the physiological principles of treatment was reflected by the many management methods advocated in the past2,3. Currently, regimens that provide continuous intravenous glucose and regular insulin delivery are generally preferred1. Rates of insulin (2-4 U/h) are recommended, but must be titrated to serum glucose levels. Insulin and glucose can either be infused separately or given as a mixture; potassium chloride is added to the latter (glucose-potassium-insulin or GKI infusion) to counteract the risk of hypokalemia.
The separate-line system includes infusion line to deliver 10% glucose solution at 80-100 mL/h (an electronic drip-counter is recommended), while a syringe driver pump delivers insulin through the other line usually at 2-4 U/h. The glucose-potassium-insulin (GKI) is more simple and also effective. To a 500 mL bag of 10% dextrose are added 10 mmol potassium and 15 U soluble insulin. The mixture is infused at a rate of 80-100 mL/h.
During GKI infusion, blood glucose should be monitored at least hourly until insulin requirements have been determined according to the following schedule:
Standard GKI Infusion
500 mL 10% dextrose (glucose) solution + 15 U short-acting insulin + 10 mmol KCl
* infuse 80-100 mL/h
Sliding Scale Control measure Blood Glucose with Strip 1-2 Hourly Initially
- 6-11 mmol/L -------> standard GKI infusion
- > 11 mmol/L -------> GKI containing 20 U insulin
- < 6 mmol/L -------> GKI containing 10 U insulin
Continue 5 U adjustments as necessary
The insulin delivery rate is altered by substituting a new bag containing a different dosage and the potassium content is varied according to regular plasma electrolyte measurements. When GKI is prolonged dilutional hyponatremia may occur. This should be treated by additional saline infusion. If patients are at risk of volume overload, smaller volumes can be used with appropriate adjustment of insulin and potassium content. The GKI infusion is versatile and can also be used in type 1 diabetes patients undergoing radiological or endoscopic investigations that required fasting or when patients are unable to eat because of anorexia or vomiting.
Postoperative Management
As soon as the patient is able to eat, the usual treatment regimen can be resumed. Frequent glycemic monitoring is essential because of the variable effects of surgical trauma and other factors such inactivity, postoperative infection and changes in medication.
In places where a "diabetes team" is available for the care of persons with diabetes undergoing surgery, there are no major problems using locally designed protocols. Even without this team in other places, a successful service can still be provided. A simple and concise management protocol should be drawn up and agreed upon by the diabetes team, surgeons and anesthetists. The protocol can be widely distributed and routine care can be undertaken by junior surgical and anesthetic staff having the diabetologist to supervise difficult cases. A vital aspect is adequate blood glucose monitoring. This is generally done by nursing staff at the bedside, using glucose-oxidase reagent strip read by meter. Measurements should be made at least every two hours on the day of surgery and every six hours thereafter.
Summary
Surgical stress induces enhanced catabolism which may result in hyperglycemia and ketosis in diabetes. Successful management of surgery in persons with diabetes requires simple and safe protocols. For type 2 diabetes, long-acting sulfonylureas should be changed for shorter-acting agents some days before surgery. Even persons with type 2 diabetes and appropriate glycemic control will require close glucose monitoring during the perioperative period. Persons with type 2 diabetes, whose glycemic control is suboptimal, should be treated the same way as the person with type 1 diabetes who requires continuous administration of insulin, glucose and potassium. Insulin and electrolyte adjustments should be made during the perioperative and postoperative periods. Infusion should be stopped as soon as the patient is able to eat normally and then the usual treatment regimen can be restarted.
References
- Gill G.V.: Surgery in patients with diabetes mellitus. In: Textbook of Diabetes. Eds. Pickup J. and Williams G. Blackwell Science. 1997, vol. 2, chap. 71:71.1-71.7.
- Alberti K.G., Thomas D.J.: The management of diabetes during surgery. Br J Anaesth, 51(7): 693-710, 1979.
- Alberti K.G., Gill G.V., Elliott M.J.: Insulin delivery in the diabetic patient. Diabetes Care 5 (Suppl 1): 65-77, 1982.
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