CEREBROVASCULAR REACTIVITY TO CO2 DURING GENERAL-ANESTHESIA MAINTAINED WITH EITHER ISOFLURANE-N2O OR PROPOFOL-N2O - A COMPARATIVE-STUDY WITH TRANSCRANIAL DOPPLER VELOCIMETRY

Objectives: To compare, using transcranial doppler velocimetry (TDV), the cerebral blood flow velocity and CO2 reactivity during general ana esthesia maintained with either isonurane-N2O-O-2 (IF) or propofol-N2O -O-2 (PF) in adults with a normal brain. Study design: Nonrandomized c ontrolled trial. Patients: Forty ASA I patients (mean age 41 +/- 13 yr s, 15 F/35 M) undergoing surgery of the lumbar spine in prone position . The first 20 were allocated into the IF group and the subsequent 20 into the PF group. Methods: General anaesthesia was induced with midaz olam (0.05 mg . kg(-1)), phenoperidine (0.03 mg . kg thiopentone (5 mg . kg(-1)), vecuronium (0.1 mg . kg(-1)) and maintained with N2O (50 v ol %) and O-2 (50 vol %) and either isoflurane (0.8 < Fet < 1 vol %) i n IF group or propofol (6 mg . kg(-1). h(-1)) in PF group. The vascula r reactivity was assessed with velocimetry measurements (Angiodine(TM) DMS, with a probe transmitting a 2-MHz pulsed wave) of flow in the mi ddle cerebral artery at a given PetCO(2) (obtained by adjustments of V T) during systole (SV) and diastole (DV). Three measurements were made : at T1 (PetCO(2) = 30 +/- 2 mmHg), at T2 (PetCO(2) = 40 +/- 2) and at T3 (PetCO(2) = 30 +/- 2 mmHg). Results: In the IF group, VS increased by + 32 % at T2 (P = 0.006) with an increase of + 3.4 %/1 mmHg of Pet CO(2). Similarly, in the PF group VS increased by + 31% at T2 (P < 0.0 001) with an increase of 2,9 %/1 mmHg of PetCO(2). In both groups the VS returned to baseline values at T3. In the IF group, VD increased by + 66 % at T2 (P < 0.0001), with an increase of + 7 %/ 1 mmHg of PetCO (2). Similarly in the PF group, VD increased by + 61 % (P < 0.0001) wi th an increase of + 5.7 %/ 1 mmHg of PetCO(2). In both groups the VD r eturned to baseline values at T3. Conclusions: During anaesthesia main tained with either isoflurane-N2O-O-2 or propofol-N2O-O-2, a change in PetCO(2) results in similar changes in VS and VD. These anaesthetic a gents preserve the cerebrovascular reactivity of the normal brain. The results of this study are in accordance with those obtained with othe r reference techniques in healthy volunteers. Transcranial doppler vel ocimetry can be a useful noninvasive tool of clinical research in neur oanaesthesia.