August 19, 2020Journal of Clinical Monitoring and Computing127 citationsOpen Access
Comparison of common perioperative blood loss estimation techniques: a systematic review and meta-analysis
Structured PICO
Do colorimetric methods improve the accuracy of perioperative blood loss estimation compared to gravimetric or visual methods?
P
Population
In vivo and in vitro human studies investigating the accuracy of techniques for quantifying blood loss (90 studies included in systematic review, 6 studies in meta-analysis).
I
Intervention
Colorimetric methods for estimating blood loss
C
Comparator
Gravimetric methods and visual methods, compared against a validated reference (e.g., Haemoglobin extraction assay)
O
Outcome
Systematic measurement errors (correlation to reference and bias in ml) of the different blood loss estimation methodssurrogate
Colorimetric methods provide significantly higher accuracy and lower bias in estimating perioperative blood loss compared to traditional visual and gravimetric methods.
Abstract
Estimating intraoperative blood loss is one of the daily challenges for clinicians. Despite the knowledge of the inaccuracy of visual estimation by anaesthetists and surgeons, this is still the mainstay to estimate surgical blood loss. This review aims at highlighting the strengths and weaknesses of currently used measurement methods. A systematic review of studies on estimation of blood loss was carried out. Studies were included investigating the accuracy of techniques for quantifying blood loss in vivo and in vitro. We excluded nonhuman trials and studies using only monitoring parameters to estimate blood loss. A meta-analysis was performed to evaluate systematic measurement errors of the different methods. Only studies that were compared with a validated reference e.g. Haemoglobin extraction assay were included. 90 studies met the inclusion criteria for systematic review and were analyzed. Six studies were included in the meta-analysis, as only these were conducted with a validated reference. The mixed effect meta-analysis showed the highest correlation to the reference for colorimetric methods (0.93 95% CI 0.91-0.96), followed by gravimetric (0.77 95% CI 0.61-0.93) and finally visual methods (0.61 95% CI 0.40-0.82). The bias for estimated blood loss (ml) was lowest for colorimetric methods (57.59 95% CI 23.88-91.3) compared to the reference, followed by gravimetric (326.36 95% CI 201.65-450.86) and visual methods (456.51 95% CI 395.19-517.83). Of the many studies included, only a few were compared with a validated reference. The majority of the studies chose known imprecise procedures as the method of comparison. Colorimetric methods offer the highest degree of accuracy in blood loss estimation. Systems that use colorimetric techniques have a significant advantage in the real-time assessment of blood loss.