Haemodynamic and catecholamine response to isoflurane anaesthesia in patients undergoing coronary artery surgery

Abstract

Haemodynamic and p/asma catecholamine responses were evalualed during isoflurane anaesthesia in ten patients undergoing coronary artery bypass surgcry. Following thiopentone induction the patients were anaesthetized with isoflurane 1.5-2.0 per cent in oxygen. The results show that after 10 minutes of isoflurane anaesthesia there was a significant increase from baseline in heart rate, 68 to 80; cardiac output, 3.75 to 4.61; and plasma epinephrine, 0.80 to 1.33 p~g/l. Conversely, there was a significant reduction in systemic vascular resistance index, 3388 to 2260, and plasma norepinephrine, 1.10 to 0.88 Ftg/1. Twenty-five minutes later, after sternotomy, heart rate, cardiac output and the level of plasma epinephrine were still elevated, and systemic vascular resistance index and plasma norepinephrine remained lowered (p < 0.05). This study demonstrates significant catecholamine responses daring isoflutane anaesthesia. The increase in plasma epinephrine paralleled the increase in heart rate and cardiac output, and the decrease in plasma norepinephrine paralleled the decrease in systemic vascular resistance. Based upon these findings we conclude that catecholamine responses contribute to the cardiac and peripheral cardiovascular changes observed with isoflurane anesthesia.

Impact of surgical stress on the haemodynamic profile of isoflurane–induced hypotension

“…Another assumption may be that the enhancement of PRA results partly from the renal sympathetic stimulation and the centrally released catecholamines, as supported by other studies (25,26). Even though several groups of investigators (3, [27][28][29][30] have assessed the effects of isoflurane on autonomic function, comparison of the various results is difficult due to differences in experimental protocols such as duration of procedure, dosing regimen, presence or severity of cardiovascular disease, and the methods used to assess autonomic function. One should point out with determination that the nature and the potency of narcotic analgesia as well as the magnitude of the stress response is frequently unfocused.…”

“…One should point out with determination that the nature and the potency of narcotic analgesia as well as the magnitude of the stress response is frequently unfocused. For example, the suggestion that haemodynamic and catecholamine responses are similar during isoflurane anaesthesia used alone or in association with low doses (2 pg/kg) of fentanyl (30) is incorrect with regard to surgical stress (upper abdominal surgery); likewise the suggestion that the catecholamine response contributes to the cardiac and peripheral vascular changes observed with isoflurane anaesthesia used in combination with morphine (0.1 mg/kg) (27) is largely inconsistent with the lack of protective effect against laryngoscopy and sternotomy. The most likely reason for the catecholamine release is inadequate analgesia.…”