Hypoglycaemia as a Consequence of Pre-Operative Fasting: Myth or Reality?

Background: The fatal risk of pulmonary aspiration of gastric contents during anaesthesia had since been recognized and consequently preoperative fasting guideline is usually prescribed to prevent this. Concern about development of hypoglycaemia during prolonged fasting has often been expressed, especially in children. AIM: This study is intended to determine the fasting blood glucose in preoperative patients of different age groups who were fasted for varying duration of time, and determine whether indeed hypoglycaemia occurs during inadvertently prolonged fasting which we often encounter in our practice setting. Methodology: A prospective cohort study of fasting blood glucose (FBG) of patients presenting for elective surgery in the principal investigator's operating rooms at the National Orthopaedic Hospital, Enugu, Nigeria was carried out. Blood glucose meter was used for estimation of glucose in capillary whole blood of the patients and the obtained data were analysed using SPSS version 16.0 statistical software. Comparison of mean values was done using the Chi-square test with statistical significance put at P < 0.05. Results: Out of one hundred and thirty three patients studied with mean age of 30.2 ± 19.60 years (range: 1-72 years), and mean duration of fasting 12.73 ± 2.01 hours, (range: 8-16 hours), the mean fasting blood glucose was found to be 91.49 ± 13.36mg/dl (range: 58 - 124mg/dl). No relationship was found between age and FBG (Pearson's correlation coefficient, r = 0.025). Likewise duration of fasting did not relate with FBG (Pearson's correlation coefficient, r = 0.088). One patient (0.8%) had hypoglycaemia, with blood glucose of 58mg/dl. Conclusion: Hypoglycaemia as a consequence of pre-operative fasting is rare, even in non-infants fasted for considerably long hours. Neither patient's age, gender, nor duration of fasting had any significant influence on the fasting blood glucose of the patients.