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Correspondence |
Montreal, Quebec
To the Editor:
Evidence is mounting that maintenance of normoglycemia (4–6 mmol·L–1) improves outcome after myocardial infarction1 and cardiac surgery.2,3 Although perioperative glucose control is a laudable goal, its achievement is elusive as illustrated by the failure of a sliding scale insulin administration preserving normoglycemia.4,5 A recent case at our institution demonstrates that hyperglycemia when severe is difficult to treat, particularly in a diabetic patient.
A 48-yr-old female type I diabetic was transferred to our coronary care unit from a nearby community hospital with unstable angina. She had elevated cardiac enzymes and ST elevations in multiple leads. During transport to our institution her insulin infusion was stopped. The patient was scheduled for immediate revascularization surgery after coronary artery angiography revealed multi-vessel disease. Due to the urgency of the situation insulin administration was likely overlooked and not restarted. When our team learned of the scheduled emergency surgery her blood glucose was 23.7 mmol·L–1. The patient was transferred to the operating room within 30 min while on a nitroglycerin infusion diluted in 5% dextrose. After induction of anesthesia the patient’s blood glucose level was greater than the upper detection limit of our glucose analyzer, i.e., > 27 mmol·L–1 (GEM Premier 3000 Blood Gas and Electrolyte Analyzer Model 5700 Instrumentation Laboratory Canada Ltd Richmond Hill, ON, Canada). We immediately started an insulin infusion at 10 U·hr–1 and administered insulin in boluses of 30 or 40 units every 20 to 30 min over the course of the surgery. Despite the massive doses of insulin administered, a total of 300 U over four hours after induction until arrival of the patient in the intensive care unit, the blood glucose remained elevated at 12.4 mmol·L–1. After another four hours the blood glucose reached normal levels but thereafter the patient required exogenous glucose to maintain normoglycemia. Twelve hours after the end of the operation, the blood glucose was finally stabilized at 7.2 mmol·L–1 with the patient receiving insulin at 4 U·hr–1. The patient’s postoperative course was complicated by renal failure requiring continuous veno-veno hemodialysis. The patient was discharged home on postoperative day ten.
This case demonstrates that a good deal of time and massive doses of insulin are required to reverse the insulin resistance of cardiac surgery in a diabetic patient; once established, severe hyperglycemia is impossible to overcome during the typical three to four hour time frame of cardiac surgery. Preoperative attention to the prevention of hyperglycemia is necessary for successful blood glucose control and the potential benefits of insulin therapy.
References
1 Malmberg K, Norhammar A, Wedel H, Ryden L. Glycometabolic state at admission: important risk marker of mortality in conventionally treated patients with diabetes mellitus and acute myocardial infarction: long-term results from the Diabetes and Insulin-Glucose Infusion in Acute Myocardial Infarction (DIGAMI) study. Circulation 1999; 99: 2626–32.
2 Furnary AP, Gao G, Grunkemeier GL, et al. Continuous insulin infusion reduces mortality in patients with diabetes undergoing coronary artery bypass grafting. J Thorac Cardiovasc Surg 2003; 125: 1007–21.
3 Furnary AP, Zerr KJ, Grunkemeier GL, Starr A. Continuous intravenous insulin infusion reduces the incidence of deep sternal wound infection in diabetic patients after cardiac surgical procedures. Ann Thorac Surg 1999; 67: 352–62.
4 Chaney MA, Nikolov MP, Blakeman BP, Bakhos M. Attempting to maintain normoglycemia during car-diopulmonary bypass with insulin may initiate postoperative hypoglycemia. Anesth Analg 1999; 89: 1091–5.
5 Groban L, Butterworth J, Legault C, Rogers AT, Kon ND, Hammon JW. Intraoperative insulin therapy does not reduce the need for inotropic or antiarrhythmic therapy after cardiopulmonary bypass. J Cardiothorac Vasc Anesth 2002; 16: 405–12.[Medline]
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