The incidence of maternal hypoglycaemia with prolonged fasting before elective caesarean section

Abstract

Background: Both national and international guidelines recommend that parturients fast from solids and clear fluids for six and two hours, respectively, prior to a caesarean section (c-section) in order to reduce the risk of pulmonary aspiration. The objective of this study was to evaluate whether fasting times conform to the current American Society of Anesthesiologists’ (ASA) recommendations and whether prolonged fasting times are associated with metabolic sequelae, namely hypoglycaemia and ketonuria.

Methods: A total of 56 parturients were enrolled and interviewed at Tygerberg Hospital, a tertiary referral hospital in Cape Town, South Africa. Women who were unable to provide consent (below the age of 18) and/or women who were not scheduled for an elective c-section were excluded from the study. Whole blood glucose and urine ketone levels were measured immediately before anaesthesia.

Results: Fasting times for solids and fluids were 15 hours (IQR 12–18; 95% CI 14–17) and 14 hours (IQR 11–16; 95% CI 12–15), respectively. During the preceding week, 32% of the participants were subjected to repeated fasting periods with a median cumulative time (all the fasting periods added) of 40 hours (IQR 35–64; range 28–133). Hypoglycaemia occurred in 39.3% (95% CI 26.8–53.3) and significant ketonuria occurred in 51.8% (95% CI 38.1–65.1) of the participants, with both conditions associated with longer fasting times (p < 0.001). A sigmoid relationship was observed between fasting time and the probability of hypoglycaemia. Hypoglycaemia was unlikely to occur before nine hours of fasting, and thereafter, the risk of hypoglycaemia increased 1.5-fold per hour (95% CI 1.2–1.8).

Conclusion: Fasting times before an elective c-section were longer than what is recommended by the ASA guidelines and were associated with statistically and clinically significant metabolic consequences. Maternal glucose should be checked after nine hours of fasting, since the incidence of hypoglycaemia exceeds 5% after nine hours of fasting. Adherence to outdated fasting practices should also be addressed. Fasting time may be a simple, useful healthcare quality indicator.