The effect of isocapnic hyperventilation on early recovery after remifentanil/sevoflurane anesthesia in O /air: A randomized trial.

BACKGROUND

Isocapnic hyperventilation (ICHV) may hasten emergence from general anesthesia but remains inadequately studied. We prospectively determined emergence time after sevoflurane anesthesia of variable duration with and without ICHV.

METHODS

In 25 ASA I-II patients, general anesthesia was maintained with one age-adjusted MAC sevoflurane in O /air and target-controlled remifentanil delivery. At the start of skin closure, the remifentanil effect-site concentration was reduced to 1.5 ng/mL, any residual neuromuscular block reversed, and once the remifentanil effect-site concentration had decreased to 1.5 ng/mL, remifentanil and sevoflurane administration was stopped, and the fresh gas flow increased above minute ventilation. Patients randomly received either normoventilation (n = 13) or ICHV (doubling minute ventilation while titrating CO into the inspiratory limb to maintain isocapnia [n = 12]). Three early recovery end points were determined: time to proper response to verbal command; time to extubation; and time to stating one's name.

RESULTS

Demographics were the same in both groups. Recovery end points were reached faster in the ICHV group compared to the normoventilation group: time to proper response to verbal command was 7.6 ± 2.2 vs 9.9 ± 2.9 min (P = 0.03); time to extubation was 7.6 ± 2.6 vs 11.0 ± 2.4 min (P = 0.002); and time to stating one's name was 8.9 ± 2.8 vs 12.5 ± 2.6 min (P = 0.003). Within each group, duration of anesthesia only marginally affected the times to reach these recovery end points.

CONCLUSION

Isocapnic hyperventilation only had a small effect on emergence times after anesthesia, suggesting that isocapnic hyperventilation may have limited clinical benefits with modern potent inhaled anesthetics.