Abstract
Purpose
Carbon dioxide (CO$_{2}$) increases cerebral perfusion. The effect of CO$_{2}$ on apnea tolerance, such as after anesthesia induction, is unknown. This study aimed to assess if cerebral apnea tolerance can be improved in obese patients under general anesthesia when comparing O$_{2}$/Air (95%O$_{2}$) to O$_{2}$/CO$_{2}$ (95%O$_{2}$/5%CO$_{2}$).
Methods
In this single-center, single-blinded, randomized crossover trial, 30 patients 18–65 years, with body mass index > 35 kg/m$^{2}$, requiring general anesthesia for bariatric surgery, underwent two apneas that were preceded by ventilation with either O$_{2}$/Air or O$_{2}$/CO$_{2}$ in random order. After anesthesia induction, intubation, and ventilation with O$_{2}$/Air or O$_{2}$/CO$_{2}$ for 10 min, apnea was performed until the cerebral tissue oxygenation index (TOI) dropped by a relative 20% from baseline (primary endpoint) or oxygen saturation (SpO$_{2}$) reached 80% (safety abortion criterion). The intervention was then repeated with the second substance.
Results
The safety criterion was reached in all patients before cerebral TOI decreased by 20%. The time until SpO$_{2}$ dropped to 80% was similar in the two groups (+ 6 s with O$_{2}$/CO$_{2}$, 95%CI -7 to 19 s, p = 0.37). Cerebral TOI and PaO$_{2}$ were higher after O$_{2}$/CO$_{2}$ (+ 1.5%; 95%CI: from 0.3 to 2.6; p = 0.02 and + 0.6 kPa; 95%CI: 0.1 to 1.1; p = 0.02).
Conclusion
O$_{2}$/CO$_{2}$ improves cerebral TOI and PaO$_{2}$ in anesthetized bariatric patients. Better apnea tolerance could not be confirmed.
Schmidt, Marc T