Comparative Study of Brain Protection Effect between Thiopental and Etomidate Using Bispectral Index during Temporary Arterial Occlusion

Abstract

Objective: This study was conducted to compare the effect of etomidate with that of thiopental on brain protection during temporary vessel occlusion, which was measured by burst suppression rate (BSR) with the Bispectral Index (BIS) monitor.

Methods: Temporary parent artery occlusion was performed in forty one patients during cerebral aneurysm surgery. They were randomly assigned to one of two groups. General anesthesia was induced and maintained with 1.5-2.5 vol% sevoflurane and 50% N(2)O. The pharmacological burst suppression (BS) was induced by a bolus injection of thiopental (5 mg/kg, group T) or etomidate (0.3 mg/kg, group E) according to randomization prior to surgery. After administration of drugs, the hemodynamic variables, the onset time of BS, the numerical values of BIS and BSR were recorded at every minutes.

Results: There were no significant differences of the demographics, the BIS numbers and the hemodynamic variables prior to injection of drugs. The durations of burst suppression in group E (11.1±6.8 min) were not statistically different from that of group T (11.1±5.6 min) and nearly same pattern of burst suppression were shown in both groups. More phenylephrine was required to maintain normal blood pressure in the group T.

Conclusion: Thiopental and etomidate have same duration and a similar magnitude of burst suppression with conventional doses during temporary arterial occlusion. These findings suggest that additional administration of either drug is needed to ensure the BS when the temporary occlusion time exceed more than 11 minutes. Etomidate can be a safer substitute for thiopental in aneurysm surgery.

Keywords: Aneurysm; Barbiturate; Bispectral Index (BIS) Burst suppression; Etomidate; Temporary arterial occlusion.

Fig. 1

Changes of Bispectral Index (BIS) values after thiopental or etomidate administration in patients who underwent temporary arterial occlusion during aneurysm surgery. Changes of BIS present the difference from the time of drug injection shows similar changes according to the time in both groups. The magnitude of BIS number change in group E was compared with that of group T, but there was no significant difference between the groups (p=0.878).

Fig. 2

Changes of burst suppression ratio (BSR) after thiopental or etomidate administration during temporary arterial occlusion on aneurysm surgery. The SR (%) means BSR. The first appearance time of BSR are 59.2±29.7 sec in group thiopental (T) and 68.0±39.1 sec in group etomidate (E) (p=0.434). The duration of burst suppression as measured by the BSR on the Bispectral Index monitor is 11.1±6.8 min in group T and 11.1±5.6 min in group E, which indicates no significant difference between the groups (p=0.979).