Increased ventilation requirements during obstetric general anaesthesia

Abstract

The inspiratory fresh gas flow rate (FGF) required to produce an end-tidal carbon dioxide tension (PE' CO2)of 4kPa during general anaesthesia, neuromuscular blockade and artificial ventilation, was compared in a group of 46 obstetric patients and a matched group of 50 non-pregnant female patients. The non-pregnant patients required a mean (SD) inspiratory FGF of 77 (10.6) ml kg-1 min-1, whereas the pregnant patients required a mean FGF of 121 (24.6) ml kg-1 min-1 before delivery (in those who reached a stable state), and 109 (19.3) ml kg-1 min-1 after delivery. These represent significant (P < 0.0001) increases of 57% and 42%, respectively, over the non-pregnant state. © 1988 British Journal of Anaesthesia.