Nitrous Oxide Enhances the Level of Sensory Block by Epidural Lidocaine

Goo, Young Gwon; Woo, Soo Young; Cho, Kang Hee

Abstract

BACKGROUND: Systemic administration of opioid can prolong the duration of epidural anesthesia. The authors examined the effect of nitrous oxide (NO) on the level of sensory block induced by epidural lidocaine.
METHODS
Twenty minutes after epidural injection of 2% lidocaine (below 70 years: 20 ml, 70 years and above: 15 ml), the level of sensory block was assessed (2nd stage). Patients were randomly assigned to receive either medical air (control group, n-15) or 50% N2O in oxygen (N2O group, n 15) for 10 minutes, the level of block was reassessed (3rd stage). Pateints were given room air (control group) or 100% oxygen for 5 minutes and room air for 5 minutes (N2O group), and the level of block was reassessed (4th stage).
RESULTS
At the 3rd stage, N2O group showed 4.3 cm cephalad increase in the level of sensory block (p=0.005), but control group revealed 1.43 cm regression. After discontinuation of gas, the level of block regressed in both group (p=0.000). At the 4th stage, NO group revealed 3.5 cm cephalad increase (p=0.048) and control group 1.97 cm regression (p=0.001) as compared with the 2nd stage.
CONCLUSIONS
The level of sensory block induced by epidural lidocaine was significantly increased cephalad by concommitant use of 50% NO for 10 minutes.