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

PURPOSE

General anaesthetic agents and aging affect cerebrovascular CO2 reactivity (CCO2R). The purpose of this study was to investigate the effect of aging on CCO2R 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 (PETCO2) 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 PETCO2. The CCO2R 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 PETCO2 was increased from 20 to 50 mmHg. The CCO2R at PETCO2 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, CCO2R is well preserved, and that the CCO2R at PETCO2 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.