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Isoflurane: Coronary blood flow and myocardial metabolism in patients with coronary heart disease
LITERATURE REVIEW
the myofilaments, extra- or intracellular edema, broken cristae or granules in the mitochondria, and nuclear changes suggestive of ischemic injury. The degree of ischemic injury, dilatation of the T system and sarcoplasmic reticulum, and presence or absence of glycogen were incorporated into a scoring system used by the authors to evaluate myocardial ischemic injury. The degree of ischemic injury was time related with the Kirsch solution, with a safe limit for cardiac arrest of no more than 50 minutes. Intermittent fibrillation, although not time dependent, also resulted in severe, even irreversible, ischemic injury. The other three chemical cardioplegia solutions provided non-time-dependent myocardial protection. Tolerance to ischemia was greater in patients with coronary disease than in those with myocardial hypertrophy secondary to aortic valvular disease. L a r s e n R , H i l f i k e r O, P h i l b i n D M , et al: Isoflurane: Coronary blood flow and myocardial metabolism in patients with coronary heart dise a s e . Anaesthesist 3 5 : 2 8 4 - 2 9 0 , 1 9 8 6 Adding to the growing evidence of the coronary vasodilator activity of isoflurane, the findings in this paper suggest the development of myocardial ischemia caused by coronary vasodilation and redistribution of myocardial blood flow. Isoflurane significantly decreased coronary blood flow in a group of ten patients with coronary artery disease and normal ventricular function during the induction (0.4% endtidal isoflurane) and maintenance (1.5% end-tidal isoflurane during sternotomy) of isoflurane-nitrous oxide anesthesia. However, during sternotomy, myocardial blood flow and myocardial uptake of free fatty acids, pyruvate, lactate, and glucose increased to preinduction levels. Nevertheless, myocardial lactate production occurred in four patients, one after induction and three during sternotomy, while three additional patients decreased their myocardial lactate uptake during sternotomy. Unlike the patients in previous reports of isoflurane's coronary vasodilatory action (Reiz S e t al: Anesthesiology 59:91-97, 1983), these subjects had normal ventricular function and remained on their maintenance doses of beta and calcium entry blocking drugs, a more clinically relevant situation.
89
H e l b o - H a n s e n S, F l e t c h e r R , L u n d b e r g D,
et al: Clonidine and the sympatico-adrenal response to coronary artery bypass surgery. Acta Anaesthesiol Scand 30:235-242, 1 9 8 6 Postcardiotomy hypertension has been attributed to coronary reflexes, increased activity of the renin-angiotensin system, preexisting hypertension, beta blockade withdrawal, and sympathetic overactivity. Helbo-Hansen and colleagues evaluated the perioperative administration of intravenous clonidine (4 ~g/kg before surgery, 2 #g/kg after cardiopulmonary bypass, and 1 gg/kg during skin closure) as a method to control sympathetic overactivity and postoperative hypertension. In a prospective, randomized study of 40 patients, the authors noted significantly decreased epinephrine and norepinephrine in the group receiving clonidine, but no attenuation of postcardiotomy hypertension. Plasma clonidine concentrations, determined by radioimmunoassay, were about 2 #g/L throughout the study. These concentrations have been reported to produce a maximal hypotensive effect. Significant hypotension or other adverse effects from clonidine were absent from the study population. ACKNOWLEDGMENT
The papers reviewed for this issue included those published in the following journals: Anesthesiology, Anesthesia and
Analgesia, Anaesthesia, Acta Anaesthesiologica Scandinavica, Canadian Anaesthetists Society Journal, British Journal of Anaesthesia, Anaesthesist, Japanese Heart Journal, Pediatric Cardiology, Perfusion, Journal of Clinical Monitoring, Circulation, American Journal of Cardiology, Journal of Vascular Surgery, Journal of the American College of Cardiology, Journal of Pharmacology and Experimental Therapeutics, Journal of Applied Physiology, Critical Care Medicine, American Heart Journal, Journal of Critical Care, Journal of Thoracic and Cardiovascular Surgery, European Heart Journal, Annals of Thoracic Surgery, American Review of Respiratory Diseases, British Heart Journal, and Chest. The reviewer thanks Professor Dr J.G. Bovill and Professor Takao Saito for providing abstracts from the foreign literature.
the myofilaments, extra- or intracellular edema, broken cristae or granules in the mitochondria, and nuclear changes suggestive of ischemic injury. The degree of ischemic injury, dilatation of the T system and sarcoplasmic reticulum, and presence or absence of glycogen were incorporated into a scoring system used by the authors to evaluate myocardial ischemic injury. The degree of ischemic injury was time related with the Kirsch solution, with a safe limit for cardiac arrest of no more than 50 minutes. Intermittent fibrillation, although not time dependent, also resulted in severe, even irreversible, ischemic injury. The other three chemical cardioplegia solutions provided non-time-dependent myocardial protection. Tolerance to ischemia was greater in patients with coronary disease than in those with myocardial hypertrophy secondary to aortic valvular disease. L a r s e n R , H i l f i k e r O, P h i l b i n D M , et al: Isoflurane: Coronary blood flow and myocardial metabolism in patients with coronary heart dise a s e . Anaesthesist 3 5 : 2 8 4 - 2 9 0 , 1 9 8 6 Adding to the growing evidence of the coronary vasodilator activity of isoflurane, the findings in this paper suggest the development of myocardial ischemia caused by coronary vasodilation and redistribution of myocardial blood flow. Isoflurane significantly decreased coronary blood flow in a group of ten patients with coronary artery disease and normal ventricular function during the induction (0.4% endtidal isoflurane) and maintenance (1.5% end-tidal isoflurane during sternotomy) of isoflurane-nitrous oxide anesthesia. However, during sternotomy, myocardial blood flow and myocardial uptake of free fatty acids, pyruvate, lactate, and glucose increased to preinduction levels. Nevertheless, myocardial lactate production occurred in four patients, one after induction and three during sternotomy, while three additional patients decreased their myocardial lactate uptake during sternotomy. Unlike the patients in previous reports of isoflurane's coronary vasodilatory action (Reiz S e t al: Anesthesiology 59:91-97, 1983), these subjects had normal ventricular function and remained on their maintenance doses of beta and calcium entry blocking drugs, a more clinically relevant situation.
89
H e l b o - H a n s e n S, F l e t c h e r R , L u n d b e r g D,
et al: Clonidine and the sympatico-adrenal response to coronary artery bypass surgery. Acta Anaesthesiol Scand 30:235-242, 1 9 8 6 Postcardiotomy hypertension has been attributed to coronary reflexes, increased activity of the renin-angiotensin system, preexisting hypertension, beta blockade withdrawal, and sympathetic overactivity. Helbo-Hansen and colleagues evaluated the perioperative administration of intravenous clonidine (4 ~g/kg before surgery, 2 #g/kg after cardiopulmonary bypass, and 1 gg/kg during skin closure) as a method to control sympathetic overactivity and postoperative hypertension. In a prospective, randomized study of 40 patients, the authors noted significantly decreased epinephrine and norepinephrine in the group receiving clonidine, but no attenuation of postcardiotomy hypertension. Plasma clonidine concentrations, determined by radioimmunoassay, were about 2 #g/L throughout the study. These concentrations have been reported to produce a maximal hypotensive effect. Significant hypotension or other adverse effects from clonidine were absent from the study population. ACKNOWLEDGMENT
The papers reviewed for this issue included those published in the following journals: Anesthesiology, Anesthesia and
Analgesia, Anaesthesia, Acta Anaesthesiologica Scandinavica, Canadian Anaesthetists Society Journal, British Journal of Anaesthesia, Anaesthesist, Japanese Heart Journal, Pediatric Cardiology, Perfusion, Journal of Clinical Monitoring, Circulation, American Journal of Cardiology, Journal of Vascular Surgery, Journal of the American College of Cardiology, Journal of Pharmacology and Experimental Therapeutics, Journal of Applied Physiology, Critical Care Medicine, American Heart Journal, Journal of Critical Care, Journal of Thoracic and Cardiovascular Surgery, European Heart Journal, Annals of Thoracic Surgery, American Review of Respiratory Diseases, British Heart Journal, and Chest. The reviewer thanks Professor Dr J.G. Bovill and Professor Takao Saito for providing abstracts from the foreign literature.