The accuracy of visual estimation of blood loss on SWABS by operating theatre staff st two academic hospitals

Abstract

Visual estimation of intra-operative blood loss is commonly used, however it is known to be inaccurate with both over and under estimation being reported. The aim of this study was therefore to assess accuracy of visual estimation of blood loss on commonly used swabs by operating theatre staff at two academic hospitals in Johannesburg. A prospective, descriptive, single blinded, contextual research design with convenience sampling was used. Twelve swabs (4 vascular swabs, 4 small abdominal swabs and 4 large abdominal swabs) with known volumes of reconstituted red pack cells were displayed for estimations. Hundred and forty six participants made 1739 of a possible 1752 estimations. Of these estimations 316 (18%) were accurate within 10% of the actual blood volume. There were significant differences between different size swabs with different volumes (p=0.0001), large swabs with similar volumes (p=0.0001) and two different size swabs and same volumes (p=0.0001). No significant difference was found between large swabs with same volumes. Significance between same size swabs with same volumes varied. Anaesthetists and surgeons were significantly more accurate (p= 0.025) than nurses in estimating blood volumes. There was no significant difference (p=0.109) between years of experience of participants. Visual estimation of blood on swabs is the subjective method used at the two academic hospitals to estimate intra-operative blood loss. Operating theatre staff at these hospitals were inaccurate in estimating blood volumes on swabs. Inaccurate blood volume estimations may have clinical implications for patients, it is therefore recommended that various strategies should be used to educate operating theatre staff.