Visual estimation of blood loss on swabs by surgeons and anaesthetists in KwaZulu-Natal: an online survey study



swab analysis, blood loss, blood-soaked swabs, blood loss estimation, blood conservation


Background: Human blood products are a scarce resource in South Africa. Doctors estimate blood loss from assessing swabs during surgical procedures to decide whether to transfuse blood or not. The objective of this study was to evaluate how accurate anaesthetists and surgeons in KwaZulu-Natal are at estimating the volume of blood in soaked swabs. Additionally, the study sought to determine whether choice of medical discipline, experience or medical rank had an influence on accuracy.

Methods: An observational cross-sectional study was conducted whereby medical officers, registrars and specialists within the anaesthetic and surgical disciplines were sent an electronic survey. The survey consisted of closed-ended questions and images of swabs soaked in known volumes of blood. The survey required participants to visually estimate the blood volumes from the images. Data were analysed using Stata v17.1 (StataCorp, USA) with descriptive statistics determining the accuracy. Multilevel mixed effects logistic regression was used to estimate how medical rank, discipline or experience influenced the accuracy of the assessment. An accurate estimate was defined as within 25% either above or below the actual volume.

Results: In total, 104 surveys were completed; 14 incomplete surveys were excluded. A general accuracy of 28.6% (within a deviation of 25%) was obtained for the 104 participants. No significant differences in accuracy were found based on medical discipline, medical rank, or years of experience in discipline, but accuracy improved with increased volumes.

Conclusion: Anaesthetists and surgeons are poor at visually estimating blood loss from swabs, with marginal non-significant improvements in accuracy with rank and experience. Pictorial guides placed in theatre and further teaching are suggested as options to improve the rate of accuracy among staff, along with the use of quantitative measures of blood loss.

Author Biographies

SB Gangen, University of KwaZulu-Natal

Department of Anaesthesiology and Critical Care, Nelson R Mandela School of Clinical Medicine, University of KwaZulu-Natal, South Africa

TC Hardcastle, University of KwaZulu-Natal

Trauma Unit, Inkosi Albert Luthuli Central Hospital and Department of Surgery, Nelson R Mandela School of Clinical Medicine, University of KwaZulu-Natal, South Africa


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