Glucose and insulin infusion directly after cardiac surgery: effects on systemic glucose uptake, catecholamine excretion, O2 consumption, and CO2 production

Metabolic and Hemodynamic Effects of High-Dose Insulin Treatment in Aortic Valve and Coronary Surgery

BACKGROUND

Glucose and insulin have been used as an adjuvant therapy in cardiac surgery because of their potentially beneficial effects on myocardial metabolism and contractile function. This study evaluated the effects of high-dose insulin on systemic metabolism and hemodynamics after combined heart surgery.

METHODS

Forty elective patients scheduled for combined aortic valve replacement and coronary artery bypass surgery were randomly assigned to receive either high-dose insulin treatment (short-acting insulin 1 IU.kg(-1).h(-1) with 30% glucose 1.5 mL.kg(-1).h(-1) administered separately) or control treatment (saline). The blood glucose levels were maintained within a targeted range by adjusting the rate of glucose infusion in the treatment group and by short-acting insulin bolus doses in the control group.

RESULTS

The lactate clearance was faster (p = 0.046), and the lactate levels (p = 0.016), blood glucose levels (p < 0.001), and free fatty acid levels (p < 0.001) were lower in the insulin group postoperatively. Besides, there was lesser need for dobutamine support (p = 0.013) and a trend toward better cardiac indices. Insulin treatment increased the respiratory quotient (p < 0.001), but there were no differences between the groups with regard to systemic oxygen consumption or energy expenditure measured by indirect calorimetry. The average glucose uptake in the insulin group was 7.1 g/kg in 24 hours (28 kcal.kg(-1).day(-1)).

CONCLUSIONS

The high-dose insulin treatment was associated with lower blood glucose levels, better preserved myocardial contractile function, and less need for inotropic support, and hence led to lower lactate levels postoperatively. The protocol is safe, but requires strict control of blood glucose level.

High-dose glucose-insulin-potassium after cardiac surgery: a retrospective analysis of clinical safety issues

BACKGROUND

Metabolic treatment with insulin or glucose-insulin-potassium (GIK) has received attention in association with myocardial infarction, cardiac surgery and critical care. As a result of insulin resistance during neuroendocrine stress, doses of insulin up to 1 IU kg-1 b.w.*h are required to achieve maximal metabolic effects after cardiac surgery. The clinical experience with regard to safety issues of such a high-dose GIK regime in critically ill patients after cardiac surgery is reported.

METHODS

Retrospective, observational study involving all patients treated with high-dose GIK after cardiac surgery during one year in a cardiovascular center at a University Hospital.

RESULTS

Eighty-nine patients out of 854 adult patients undergoing cardiac surgery were treated with high-dose GIK. Mean age was 69 +/- 1 years, Higgins score 5.3 +/- 0.3. Preoperatively 31.4% had left ventricular function EF< or =0.35 and 32.5% had sustained a myocardial infarct during surgery. Mortality was 5.6% and the average ICU stay was 3.7 +/- 0.5 days. The main indication for GIK was intraoperative heart failure (69.7%). The average glucose infusion rate during the first 6 h was 4.22 +/- 0.15 and 4.91 +/- 0.14 mg kg-1 b.w.*min, respectively, in diabetic and non-diabetic patients (P = 0.023). Blood glucose and s-potassium control was acceptable.

CONCLUSIONS

The high-dose GIK regime allowed substantial amounts of glucose to be infused both in diabetic and critically ill patients with maintenance of acceptable blood glucose control. Provided careful monitoring, this regime can be safely used in clinical practice and deserves further evaluation for treatment of critically ill patients following cardiac surgery.

Influence of glucose-insulin-potassium on left ventricular function during coronary artery bypass grafting

To evaluate the hemodynamic effect of glucose-insulin-potassium administered during cardiopulmonary bypass grafting (CABG), i.v. infusion of glucose 0.5 g, insulin 1.35 IU and potassium 0.25 mmol/kg b.w/hour was begun after induction of anesthesia and continued until aortic cross-clamping in seven patients. Seven controls underwent CABG without such infusion. The left ventricular ejection fraction was measured after i.v. injection of Tc-99m-HSA before and at termination of cardiopulmonary bypass (CPB), in conjunction with invasive measurements to obtain left ventricular pressure-volume indices at end-systole and end-diastole. Three-step transfusion from the oxygenator was given before and after CPB in order to assess left ventricular contractility during volume-load, using the end-systolic pressure-volume index. Left ventricular contractility remained unchanged after CPB in the patients given glucose-insulin-potassium but decreased significantly in the controls. The left ventricular passive diastolic properties were unchanged after the ischemic period in both groups. The arterial glucose concentration rose markedly in the infused group (7.3-18.5 mmol/l) and moderately (6.4-8.2) in the controls. Glucose-insulin-potassium infusion thus favorably influenced left ventricular function during CABG by preventing decrease in contractility after CPB.

Glucose and lactate balances in heart and leg after coronary surgery: influence of insulin infusion

Glucose and lactate balances in leg (representing mainly skeletal muscle) and heart were studied 1 hour after aortocoronary bypass surgery and insulin treatment. Seventeen men were randomized to receive 25 U fast-acting insulin as a bolus injection, followed by continuous infusion of 1 U/kg b.w. for 1 hour, or to serve as controls. In the leg a small glucose uptake was found while the lactate balance was negative. During the study period the lactate release increased further in the control group. In the myocardium no significant extraction of glucose or lactate could be demonstrated. Insulin treatment resulted in a fivefold increment of leg glucose uptake and in significant myocardial glucose uptake. Myocardial lactate balance was also improved by insulin treatment, with fractional extraction increased from 6 to 21%. It is concluded that myocardial carbohydrate metabolism is restricted in the early period after cardiac surgery, and that this seems to result from insulin resistance induced by the surgical trauma.