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[Cerebrovascular reactivity to CO2 during general anesthesia maintained with either isoflurane-N2O or propofol-N2O. A
1Département d'Anesthésie-Réanimation, Hôpital Neurologique et Neurochirurgical Pierre-Wertheimer, Lyon-Montchat.
Objectives:
To compare, using transcranial doppler velocimetry (TDV), the cerebral blood flow velocity and CO2 reactivity during general anaesthesia maintained with either isoflurane-N2O-O2(IF) or propofol-N2O-O2 (PF) in adults with a normal brain.
Study Design:
Nonrandomized controlled trial.
Patients:
Forty ASA I patients (mean age 41 +/- 13 yrs, 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 midazolam (0.05 mg.kg-1), phenoperidine (0.03 mg.kg-1), thiopentone (5 mg.kg-1), vecuronium (0.1 mg.kg-1) and maintained with N2O (50 vol %) and O2 (50 vol %) and either isoflurane (0.8 < Fet < 1 vol %) in IF group or propofol (6 mg.kg-1.h-1) in PF group. The vascular reactivity was assessed with velocimetry measurements (Angiodine DMS, with a probe transmitting a 2-MHz pulsed wave) of flow in the middle cerebral artery at a given PetCO2 (obtained by adjustments of VT) during systole (SV) and diastole (DV). Three measurements were made: at T1 (PetCO2 = 30 +/- 2 mmHg), at T2 (PetCO2 = 40 +/- 2) and at T3 (PetCO2 = 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 PetCO2. Similarly, in the PF group VS increased by + 31 % at T2 (P < 0.0001) with an increase of 2.9 %/1 mmHg of PetCO2. 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 PetCO2. Similarly in the PF group, VD increased by + 61% (P < 0.0001) with an increase of + 5.7%/1 mmHg of PetCO2. In both groups the VD returned to baseline values at T3.
Conclusions:
During anaesthesia maintained with either isoflurane-N2O-O2 or propofol-N2O-O2, a change in PetCO2 results in similar changes in VS and VD. These anaesthetic agents preserve the cerebrovascular reactivity of the normal brain. The results of this study are in accordance with those obtained with other reference techniques in healthy volunteers. Transcranial doppler velocimetry can be a useful noninvasive tool of clinical research in neuroanaesthesia.