Estimation of blood haemoglobin concentration using the HemoCue® during caesarean section: the effect of sampling site

BackgroundHaemoglobin concentration measured using the HemoCue® is accurate for capillary and venous/arterial blood, provided the recommended sampling method is strictly observed. Analysis of blood, particularly of capillary samples, using the HemoCue® is useful during caesarean section. The toe might be preferred to the thumb since it is numb during neuraxial anaesthesia, but whether sampling at either site is accurate in this situation, given the cardiovascular effects of anaesthesia and pregnancy, is not known. We aimed to compare haemoglobin values measured in venous and capillary samples (toe and thumb) during caesarean section under neuraxial anaesthesia.MethodFifty healthy women having caesarean section under spinal or combined spinal-epidural anaesthesia were included. At the end of surgery, the great toe and thumb (non-i.v. fluid side) were lanced as recommended for a HemoCue® reading. A venous blood sample (non-i.v. fluid side) was also taken and sent for formal laboratory measurement and tested with the HemoCue®. Bland-Altman analysis was applied to the haemoglobin values.ResultsBias (mean difference) and precision ± 2 SD were respectively 0.2 ±1.6 for laboratory vs. toe, 0.1 ±1.8 for laboratory vs. thumb, and 0.2 ±1.6 laboratory vs. venous.ConclusionOur results suggest that in terms of accuracy, the two sites are equally suitable for use during caesarean section under neuraxial anaesthesia.