Thiopental-induced burst suppression measured by the bispectral index is extended during propofol administration...

Thiopental is used to suppress cerebral metabolism during temporary clip ligation of the cerebral arteries. Electroencephalogram (EEG) can measure intraoperative burst suppression as evidence of cerebral metabolic suppression, but EEG is not always available during clip ligation. This study was conducted to compare the effect of propofol-based total intravenous anesthesia (TIVA) with sevoflurane-based inhalational anesthesia on thiopental-induced burst suppression during aneurysm surgery. The effect of thiopental was measured by burst suppression ratio (BSR) using the bispectral index (BIS) monitor.

Forty-six patients who underwent temporary clipping during aneurysm surgery were randomized into 2 groups. The inhalation group (n=21) received sevoflurane-N(2)O anesthesia and the TIVA group (n=25) received propofol-remifenatanil-N(2)O anesthesia. The anesthesia level maintained a BIS value between 40 and 55. Pharmacological burst suppression was induced with bolus administration of thiopental (5 mg/kg) before temporary clipping. The BIS number, BSR values, the onset time and duration of BSR, and hemodynamic variables were recorded every minute in both groups.

There were no significant differences between groups in the onset time of burst suppression (P=0.394) and BIS changes (P=0.878). However, statistically significant longer duration (P<0.001) and significantly higher degree of burst suppression (P=0.006) were observed in the TIVA group compared with the inhalation group.

Our results suggest that at equivalent BIS values TIVA with propofol anesthesia provides longer duration and greater cerebral metabolic suppression compared with sevoflurane-N(2)O inhalation anesthesia. BIS may be an acceptable alternative to standard EEG monitoring when assessing burst suppression during temporary clipping.