Combined effect of isoflurane and esmolol on sympathetic responses to tracheal intubation.

BACKGROUND

Influences of isoflurane and esmolol on endotracheal intubation induced sympathetic changes could be different. The effect of isoflurane and its combination with esmolol on catecholamine, blood pressure and pulse during endotracheal intubation were investigated.

METHODS

Thirty patients were anesthetized with 3.0% isoflurane and tracheal intubation was carried out at the 5th min following the exposure to isoflurane. Half of them received intravenous saline and the other half received esmolol 2 mg/kg at the 4th min. Cardiovascular parameters were recorded and venous blood samples were taken for measurement of catecholamines every min.

RESULTS

One min after administration of isoflurane, there was increase of heart rate (P < 0.05), while at the same time the epinephrine level fell (P < 0.05) and norepinephrine level remained unaltered. Both catecholamines raised after intubation (P < 0.05). The sympathetic responses to and the beta-antagonistic effect of esmolol on intubation were not significantly changed in the presence of isoflurane.

CONCLUSIONS

Isoflurane increased heart rate while paradoxically decreased epinephrine. Norepinephrine was more specifically related to endotracheal intubation, for its serum level had little change before the event. Based on catecholamine findings, the mechanism of isoflurane effect on the sympathetic system is probably different from that of endotracheal intubation.