Cerebrovascular CO2 reactivity in elderly and younger adult patients during sevoflurane anaesthesia

Abstract

Purpose: General anaesthetic agents and aging affect cerebrovascular CO2 reactivity (CCO2 R). The purpose of this study was to investigate the effect of aging on CCO2 R in patients during sevoflurane anaesthesia. Methods: Twenty-four patients were divided into two groups of 12 according to age; 20-40 yr and 50-70 yr. Anaesthesia was induced with 5 mg·kg-1 thiopentone and maintained with sevoflurane 1.0 to 1.5% (end-tidal) and nitrous oxide 66% in oxygen to maintain anaesthesia. End-tidal CO2 tension (P(ET) CO2) was altered from 20 to 50 mmHg in 5 mmHg steps by changing the respiratory rate. Middle cerebral blood flow velocity (CBFV) and pulsatility index (PI) were measured by transcranial Doppler (TCD) at each step change in P(ET) CO2. The CCO2 R was calculated as the change of CBFV per mmHg at each 5 mmHg interval. Results: In each group, there were no changes in blood pressure, heart rate, end-tidal sevoflurane concentration, or PI as the P(ET) CO2 was increased from 20 to 50 mmHg. The CCO2 R at P(ET) CO2 of 35 to 50 mmHg in the younger group (0.80 ± 0.27 (SD) cm·sec-1·mmHg-1) was larger than that in the elderly group (0.31 ± 0.16 cm·sec-1·mmHg-1)(P<0.01). Conclusion: It is concluded that, during sevoflurane anaesthesia, CCO2 R is well preserved, and that the CCO2 R at P(ET) CO2 of 35 to 50 mmHg in the 20 to 40 yr age group is greater than that in the 50 to 70 yr age group.