Myocardial preservation during coronary surgery with and without cardiopulmonary bypass.

BACKGROUND: There is increased interest in coronary artery bypass grafting (CABG) without cardiopulmonary bypass (CPB), although the preservation of the myocardium under such circumstances has not been properly investigated. The aim of this randomized study was to compare the changes in myocardial metabolism during CABG with and without CPB. METHODS: Myocardial energy metabolism and tissue injury during CABG was monitored in a series of 22 patients (11 with and 11 without CPB). RESULTS: The maximum myocardial lactate production was significantly higher (p = 0.02) in the group operated with CPB (0.56 mmol/L) than without it (0.17 mmol/L). A similar phenomenon was seen in the transcardiac pH differences (0.085 and 0.034 with and without CPB, p = 0.007). The postoperative peak values of creatine kinase-MB mass (15.1 vs 6.3 microg/L) and troponin I (13.8 vs 5.2 microg/L) were significantly higher (p < 0.001 and p = 0.008) with than without CPB. CONCLUSIONS: CABG on a beating heart is associated with better myocardial energy preservation and less myocardial damage compared with conventional CABG with CPB and intermittent antegrade mild hypothermic blood cardioplegia.

Myocardial metabolism and hemodynamics during coronary surgery without cardiopulmonary bypass.

BACKGROUND: Although renewed interest has recently been shown in coronary artery bypass grafting without cardiopulmonary bypass, no reports are available on myocardial metabolism and hemodynamics during temporary coronary occlusion and rotation of the contracting heart. METHODS: Changes in myocardial energy metabolism and hemodynamics were monitored in 12 patients undergoing elective coronary artery bypass grafting without cardiopulmonary bypass, and the postoperative efflux of creatine kinase-MB mass and troponin T were also determined. RESULTS: There was a significant increase in myocardial production of ATP degradation products (p = 0.026) and lactate (p = 0.004) during the operation. Myocardial oxygen extraction decreased (p = 0.012) in correlation with use of the short-acting beta-blocker, esmolol (r = -0.71). Apart from a decrease in mean arterial blood pressure (p = 0.002), there were no significant hemodynamic changes during the operation. The overall postoperative troponin T and creatine kinase-MB mass changes remained nonsignificant during the first two postoperative days. One patient had a myocardial infarction, diagnosed by electrocardiography, on the second postoperative day, but otherwise there were no major complications. CONCLUSIONS: Coronary artery bypass grafting without cardiopulmonary bypass seems to be well tolerated as only minor changes in myocardial energy metabolism and hemodynamics are observed during the operation.

Myocardial protection during antegrade versus retrograde cardioplegia.

BACKGROUND: It has been suggested that the right ventricular myocardium is suboptimally protected during retrograde blood cardioplegia. METHODS: Twenty patients undergoing an elective coronary bypass procedure were randomized to receive antegrade or retrograde mild hypothermic blood cardioplegia. Transventricular differences in oxygen extraction, lactate production, and pH were monitored during aortic cross-clamping, and myocardial biopsy specimens were taken from both ventricles before cannulation and 15 minutes after aortic declamping for analysis of adenine nucleotides and their breakdown products. The extent of myocardial injury was estimated by monitoring postoperative leakage of troponin T and the MB isoenzyme of creatine kinase. Hemodynamic recovery and postoperative complications were noted. RESULTS: The preoperative characteristics of the two groups were similar. Oxygen extraction and lactate production in the right ventricular myocardium were higher in the retrograde group. In this group, the right ventricle also extracted more oxygen and produced more lactate and acid than did the left ventricle. Tissue levels of adenine nucleotides tended to decrease in both ventricles during operation, with no differences between them. The level of adenosine catabolites did increase somewhat in the right ventricular myocardium of the retrograde cardioplegia group after aortic declamping. There was a tendency for more prominent efflux of troponin T and the MB isoenzyme of creatine kinase in the retrograde group. Nevertheless, the postoperative course was uneventful in both groups. CONCLUSIONS: Retrograde mild hypothermic blood cardioplegia leads to metabolic changes compatible with right ventricular ischemia. Nevertheless, tissue levels of high-energy phosphates are well preserved, and the postoperative course seems to be unproblematic. Care should be taken when retrograde normothermic blood cardioplegia is provided for patients with right ventricular hypertrophy, poor right ventricular function, or severe preoperative myocardial ischemia.

Magnesium substitution in elective coronary artery surgery: a double-blind clinical study.

Magnesium may be beneficial in the control of ventricular ectopy and supraventricular tachyarrhythmias after coronary artery bypass graft (CABG) surgery, but it is not known whether a high-dose magnesium regimen is superior to a regimen keeping the patient normomagnesemic. A prospective randomized and double-blind clinical comparison was performed in 81 elective CABG patients in order to assess the effects of two different magnesium infusion regimens on electrolyte balance and postoperative arrhythmias. Forty-one patients (high-dose group, H) received 4.2 +/- 0.7 g (mean +/- SD), of magnesium sulfate before cardiopulmonary bypass, followed by an infusion of 11.9 +/- 2.8 g of magnesium chloride until the first postoperative (PO) morning, and a further 5.5 +/- 1.0 g until the second PO morning. Forty patients (low-dose group, L) received magnesium sulfate only after bypass to a total of 2.9 +/- 0.5 g at the first, and 1.4 +/- 0.1 g at the second PO morning. A blood cardioplegia technique was used in both groups, including bolus doses of magnesium chloride to a total of 2.4 +/- 0.6 g and 2.3 +/- 0.6 g to H and L patients, respectively. Continuous Holter tape-recording was used for 12 to 15 hours preoperatively, and for 48 hours postoperatively. Serum magnesium peaked in H patients on the first PO morning at 1.60 +/- 0.25 mmol/L, whereafter it declined to the normal level on the third PO morning. Patients in the L group were normomagnesemic, except after the start of bypass.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino acid-enriched glucose-insulin-potassium infusion improves hemodynamic function after coronary bypass surgery. A double-blind study in patients with unstable angina and/or compromised left ventricular function.

OBJECTIVE: The goal of this study was to assess the effects of a combination of glucose-insulin-potassium (GIK) and the amino acids aspartate and glutamate upon perioperative hemodynamics in coronary surgery patients with unstable angina and/or compromised left ventricular function. DESIGN: Prospective, randomized, and double-blind clinical study. SETTING: Operating theatre and intensive care unit (ICU) of a university hospital. PATIENTS: 44 coronary artery bypass graft (CABG) patients with unstable angina and/or compromised left ventricular function. INTERVENTIONS: 22 patients (group A) were given 1l of an infusion with 250g glucose, 100 I.U. fast-acting human insulin, 72 mmol potassium, 32 mmol magnesium, 20 mmol phosphate, 65 mmol aspartate, and 65 mmol glutamate, while another 22 patients (group C) were given 1l of an infusion with 50 g glucose, 72 mmol potassium, 32 mmol magnesium, and 8 mmol phosphate. The infusion rate was 1.2 ml/kg/h from the anesthesia induction onward to the commencement of cardiopulmonary bypass, when it was reduced to 0.8 ml/kg/h. When 11 had been infused, but not later than 4 a.m., the infusion was continued by giving 10% glucose at the same rate to both groups. Additional insulin (median: 14.2 I.U., range: 0-41.5) or saline was given during bypass to the A and C patients, respectively. A blood cardioplegia technique containing aspartate and glutamate was used in both groups. RESULTS: At aortic cannulation, the cardiac index (CI) had increased from the pre-anesthetic level by 15.3% (mean) (SD: 31.7%) in group A and decreased by 7.7% (15.1%) in C patients, p = 0.0069. Also the changes in stroke index (SI; p = 0.022), left (LVSWI; p = 0.0037) and right ventricular stroke work index (RVSWI; p = 0.0097) were more favorable in group A. Despite longer aortic cross-clamp, p = 0.031, and perfusion times, p = 0.042, in A patients, the change in cardiac index was also better in this group after bypass: At decannulation, the difference between mean values was 31.8%, p = 0.0001, and at arrival in the ICU it was 16.1%, p = 0.028. The same was also seen 8 h postoperatively and on the 1st and 2nd postoperative mornings; p = 0.034, 0.040, and 0.037, respectively (Wilcoxon test). Favorable changes were seen for the A patients also regarding SI at decannulation (p = 0.0002) and after 8 h (p = 0.017); LVSWI at decannulation (p = 0.0002), at arrival in the ICU (p = 0.0023), and after 8 h (p = 0.0011); and RVSWI at decannulation (p = 0.0027), at the ICU (p = 0.021), after 8 h (p = 0.014), and on the 1st postoperative morning (p = 0.039). However, the response to a hemodynamic loading test (6% hydroxyethyl starch 5 ml/kg) was similar in the 2 groups, and there was no difference in the need for inotropic support. CONCLUSIONS: Amino acid-enriched GIK infusion improves hemodynamic function in CABG patients with unstable angina and/or compromised left ventricular function.

Perioperative glucose-insulin-potassium infusion in elective coronary surgery: minor benefit in connection with blood cardioplegia?

OBJECTIVE: The goal of this study was to examine the metabolic and hemodynamic effects of a glucose-insulin-potassium infusion in elective coronary surgery, when blood cardioplegia was used for cardiac protection. DESIGN AND PATIENTS: A prospective, randomized, open, clinical comparison was performed between 2 perioperative infusion regimens in 40 elective nondiabetic coronary artery bypass graft (CABG) surgery patients. SETTING AND INTERVENTIONS: 20 patients (glucose-insulin-potassium-GIK-group) received glucose 0.2 g/kg/h, insulin 0.12 U/kg/h, potassium 0.15, magnesium 0.032 and phosphate 0.024 mmol/kg/h from anesthesia induction to the start of bypass, when infusion rate was reduced to 30%, and after bypass increased to 50% of the initial rate. The infusion was continued until the first postoperative morning. Another 20 patients (control-R-group) received glucose 0.05 g/kg/h, potassium 0.075, magnesium 0.016 and phosphate 0.008 mmol/kg/h from the end of bypass to the next morning. Pump prime was glucose-free and a blood cardioplegia technique was used for cardiac protection. RESULTS: The GIK patients needed less dopamine support in the intensive care unit (ICU) (p < 0.05). No difference was found between the groups with regard to myocardial injury, the MB-fractions of serum creatine kinase (CK-MB) being elevated to a similar degree in both groups. Likewise there were no significant differences in hemodynamic changes or duration of ICU stay. Although the glucose infusion was continued during bypass in the GIK patients, there was a considerable risk of hypoglycemia (due to insulin and hemodilution) after the onset of bypass: in 5 GIK patients (25%; 95% confidence interval 8.7 to 49.1%) blood glucose was less than 2 mmol/l. However, the hypoglycemia was of short duration and no detrimental effects were seen. CONCLUSIONS: Perioperative GIK infusion entailed a slight decrease in the postoperative need for dopamine support, but was connected with a considerable risk of hypoglycemia.

Angiographic long-term outcome of carotid endarterectomy.

Late postoperative digital subtraction angiographic (DSA) findings after a mean follow-up of 6 years were examined after 61 internal carotid artery (ICA) endarterectomies performed for symptomatic (mainly TIAs) ICA stenosis on 52 patients. All 34 surviving patients were re-examined. Six of them (17.6%) had become neurologically symptomatic during the follow-up period with an annual stroke rate of 1%. DSA revealed progression of ipsilateral ICA stenosis in seven cases (23%), two of whom had evidence of bilateral angiographic deterioration. Two out of seven patients had symptomatic ipsilateral restenosis (6%). Progression of contralateral ICA stenosis was detected in five cases (16%).