The effects of enflurane and isoflurane on the regional blood flow and arteriovenous shunt in various organs in dogs
Yano, H.; Matsumoto, N.; Fukui, A.; Fujita, Y.; Sakai, T.; Takaori, M.
Masui. Japanese Journal of Anesthesiology 37(6): 667-677
1988
ISSN/ISBN: 0021-4892 PMID: 3216462 Document Number: 315454
The effects of enflurane and isoflurane on microcirculation of organs were studied in 14 dogs. Organ capillary blood flow and organ fraction of cardiac output were measured by the microsphere (.vphi. 9 .mu.m) trapping method in 14 organs. Simultaneously, arteriovenous shunt rate was meausred by continuously collecting of drainaged venous blood at 4.8 ml .cntdot. min-1 for two minutes from the brain, kidney, splanchnic organs, skeletal muscle of pelvic limb and all systemic circulatory organs. In four dogs which were anesthetized with 67% nitrous oxide alone, capillary blood flow, organ fraction of cardiac output and shunt rate were unchanged in all the organs. The remaining ten dogs were anesthetized by gas mixture of 67% nitrous oxide and either enflurane (five dogs) or isoflurane (five dogs). The capillary blood flows were decreased during inhalation of enflurane in the thyroid gland, myocardium, adrenal gland, liver, spleen, pancreas, myocardium, adrenal gland, liver, spleen, pancreas, great omentum and small intestine at 0.75 MAC, and at 1.5 MAC, also in the kidney. Although the capillary blood flows were decreased during inhalation of isoflurane in the pancreas, great omentum and small intestine at 0.75 MAC, and in the myocardium, liver and spleen at 1.5 MAC, the degree of circulatory depressant effect was less than that of enflurane. The organ fraction of cardiac output was increased in the brain during 1.5 MAC inhalation of both agents. In the other organs, it showed a similar change with the capillary blood flow. Arteriovenous shunt rate was decreased in the kidney by 0.75 and 1.5 MAC enflurane. During inhalation of isoflurane, however, it was increased in the brain at 0.75 MAC, and at 1.5 MAC, also in the skeletal muscle and systemic circulatory organs. These results suggest that, although isoflurane is more useful to keep the organ capillary blood flow than enflurane, it increases the arteriovenous shunt rate due to its vasodilating effect on the arteriovenous shunt vessels.