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.

Topical head cooling during rewarming after experimental hypothermic circulatory arrest.

BACKGROUND: The aim of this study was to evaluate the potential neuroprotective effect of topical head cooling during the first 2 postoperative hours after experimental hypothermic circulatory arrest. METHODS: Twenty pigs underwent a 75-minute period of hypothermic circulatory arrest and were randomly assigned to rewarming to 37 degrees C or to undergo topical cooling of the head for 2 hours from the start of rewarming followed by a period of external rewarming to 37 degrees C. RESULTS: The 7-day survival rate was 70% in the control group and 60% in the topical head cooling group. Despite brain tissue oxygenation, intracranial pressures, mixed oxygen venous saturation, oxygen consumption, and extraction tended to be favorable in the topical head cooling group as a clear effect of mild hypothermia. The latter group had significantly higher postoperative brain lactate and pyruvate ratios, and lactate and glucose ratios. Furthermore, the topical head cooling group had worse fluid balance throughout the postoperative period. Brain histopathologic scores were comparable with the study groups, but among 7-days survivors these scores tended to be worse in the topical head cooling group. CONCLUSIONS: Topical cooling of the head during the first 2 postoperative hours after experimental hypothermic circulatory arrest does not appear to provide any neuroprotective effect.

Ischemic preconditioning does not improve myocardial preservation during off-pump multivessel coronary operation.

BACKGROUND: The value of ischemic preconditioning during coronary operations has remained controversial. The aim of this study was to evaluate the effects of ischemic preconditioning on myocardial energy metabolism and tissue injury during off-pump multivessel coronary surgery. METHODS: Eleven patients with preceding preconditioning were compared with 11 patients without it. The preconditioning group underwent a 5-minute period of ischemia followed by a 5-minute reperfusion period before coronary occlusion for each of the first two anastomoses. RESULTS: The transmyocardial differences (coronary sinus - arterial) in inosine and the sum of adenine degradation products increased in both groups, but the differences in xanthine and hypoxanthine increased only in the preconditioning group. Myocardial lactate production increased to a maximum of 0.09 mmol/L with preconditioning and to a maximum of 0.17 mmol/L without it. Transmyocardial pH differences increased to 0.03 U in both groups. The maximum postoperative concentration of creatine kinase-MB mass was 14.8 microg/L with preconditioning and 6.3 microg/L without preconditioning, and that of troponin I 7.4 microg/L and 5.2 microg/L, respectively. There were no statistically significant differences between the groups, however. CONCLUSIONS: Ischemic preconditioning of 5 minutes followed by reperfusion of 5 minutes during off-pump multivessel coronary artery surgery did not prevent myocardial metabolic derangement and tissue injury and thus cannot be routinely recommended.

Lamotrigine plus leukocyte filtration as a neuroprotective strategy in experimental hypothermic circulatory arrest.

BACKGROUND: Lamotrigine and leukocyte filtration seem to improve cerebral protection during experimental hypothermic circulatory arrest (HCA). This study was performed to evaluate whether their combined use may further improve cerebral protection. METHODS: Twenty-four pigs undergoing 75-minute period of HCA at 20 degrees C were randomly assigned to receive saline; lamotrigine (20 mg/kg) before HCA (L); or lamotrigine (20 mg/kg) before HCA plus leukocyte filtration before and after HCA (L + LF). RESULTS: Seven animals (87%) in the L + LF group, 4 (50%) in the L group, and 3 (37%) in the control group were alive on the seventh postoperative day. The median electroencephalogram burst recovery was 94% in the L + LF group (p = 0.024 versus control group), 81% in the L group, and 64% in the control group. Among the surviving animals, the median behavioral scores were 9, 9, and 6 at the seventh day, respectively (p = 0.005 between the L + LF group and the control group). The median histopathologic score was 14 in the L + LF group (p = 0.046 versus control group), 14.5 in the L group (p = 0.062 versus control group), and 21 in the control group. CONCLUSIONS: Lamotrigine has neuroprotective effect during HCA. The combined use of lamotrigine and LF may further improve the survival outcome.