Effects of anesthesia and open-thorax surgery on coronary vascular reserve in swine

The coronary reactive hyperemic response was examined in seven pigs under anesthetized and conscious conditions, (i.e., 5 days and 3 and 5 weeks after surgery). Tygon catheters were inserted in the descending aorta of five pigs; transonic flow probes and hydraulic occluders were placed on the left cranial descending and/or left circumflex coronary arteries. Two pigs underwent long-term implantation of similar instruments. The coronary reactive hyperemic response, expressed as repayment of flow deficit, was induced by brief complete coronary artery occlusion for 15 sec. Baseline mean arterial pressure, heart rate, and coronary blood flow were similar in the anesthetized and conscious pigs. There was also no significant difference in repayment of flow deficit between the anesthetized and conscious pigs 5 days after surgery. The repayment of flow deficit (709 +/- 144%) in conscious pigs 5 days after surgery tended to be greater, but was not statistically significant from that observed in the anesthetized pigs (510 +/- 79%). However, at 3 and 5 weeks after surgery, the reactive hyperemic flow and the repayment of flow deficit were numerically greater than those values observed in anesthetized pigs. The difference in reactive hyperemic flow between conscious and anesthetized pigs was statistically significant at week 3. The difference in repayment of flow deficit between conscious and anesthetized pigs was statistically significant at week 5. These results suggest that anesthesia, as well as recent surgery, attenuates coronary vascular reserve. The major factor in the attenuation of coronary reserve appears to be recent surgical manipulation, because repayment of flow deficit was still depressed in conscious pigs during the early phase of recovery from surgery.