Does Day 1 Haemoglobin Drop Correlate with Visual Estimated Blood Loss at Caesarean Section?.

Abstract

Introduction: There is an increasing focus on improving the accuracy of estimated blood loss (EBL), with the introduction of weighed quantitative blood loss (QBL) in many maternity units. QBL at caesarean section is of uncertain value, as the liquor volume voids at the same moment as bleeding from the uterine incision begins. Aim(s): To determine if visual EBL at caesarean section correlates with postoperative haemoglobin drop. Method(s): As part of a randomised controlled trial recruiting women undergoing elective caesarean sections, EBL and postoperative haemoglobin drop were recorded as secondary outcomes. EBL was estimated by the Obstetrician or Registrar, based on visual assessment, number of soaked packs and volume of fluid suctioned. Pre-operative and Day 1 postoperative haemoglobins were obtained from participants, facilitating universal calculation of haemoglobin drop. Linear regression and multiple linear regression were used to assess for correlation. Result(s): Ninety consented participants had EBL and haemoglobin drop measured. There was a significant correlation between haemoglobin drop and EBL (R2 = 0.40, p < 0.01, 95% confidence interval: 0.0103-0.0176). An EBL of 1000 mL is predicted to yield a haemoglobin drop of 20 g/L. Multiple linear regression, controlling for BMI as a confounder, yielded a similarly significant correlation (R2 = 0.41, p < 0.001, 95% confidence interval: 0.0108-0.0182). Discussion(s): Visually estimated blood loss is a validated tool at caesarean section to predict postoperative haemoglobin drop. Given the difficulty excluding liquor from quantitative blood loss at caesarean section, it is reasonable to continue using estimated blood loss.