Comparison between gravimetric measurement and visual estimation of postpartum blood loss

Abstract

Background In clinical practice, postpartum blood loss is usually estimated visually. Studies have demonstrated visual estimation of blood loss is inaccurate in comparison to other methods, but little attention has been given to gravimetric measurement (weighing). Objective To determine the difference between gravimetric measurement of blood loss (MBL) and visual estimation of blood loss (EBL) after delivery. Methods A prospective study recruited women in labour or having elective caesarean section. Blood-stained items from delivery were weighed, and the total dry weight of items subtracted from total blood-stained weight. Blood weight (g) was converted into blood volume (ml). Results There were 60 normal vaginal deliveries, 24 instrumental deliveries and 25 caesarean sections (n=109). MBL was significantly higher than EBL in instrumental deliveries (p=0.018, Mann–Whitney) and caesarean sections (p=0.0268, Mann Whitney). There was no significant difference in MBL and EBL in normal vaginal deliveries. Blood loss was underestimated in 75% of women, and overestimated in 23%. In EBL <249 ml median difference to MBL was underestimation of 55 ml (range overestimation 80 ml – underestimation 420 ml). In EBL 250–499 ml median difference to MBL was underestimation of 65 ml (range overestimation 219 ml – underestimation 760 ml). In EBL ≥500 ml median difference to MBL was underestimation of 272 ml (range overestimation 115 ml – underestimation 1375 ml). Conclusions Gravimetric measurement is economical and easy to perform. It should be employed as an adjunct to visual estimation with blood loss greater than 250 ml, and should be utilised in instrumental deliveries and caesarean sections.

Quantification of blood loss in obstetric haemorrhage: implications on intervention and transfusion

“…Compared with visual estimation, gravimetric assessment of blood loss is more accurate in both simulated scenarios and real time studies. [24][25][26] Both volumetric and gravimetric are forms of quantitative measurement; studies have shown that when used in combination, the accuracy of blood loss assessment is improved. 27 Gravimetric blood loss assessment requires minimal resources and is a cost-effective method of assessing PPH.…”

“…27 Gravimetric blood loss assessment requires minimal resources and is a cost-effective method of assessing PPH. 25 However, it can be labour intensive, requiring a designated member of staff trained in the process. The method also assumes that 1 g of blood is equal to 1 ml of blood, but as blood density is proportional to haematocrit, this value may be inaccurate in pregnancy and acute haemorrhage.…”

“…The gravimetric method of quantifying blood loss involves weighing blood‐stained items and subtracting the dry weight to obtain a blood volume measurement. Compared with visual estimation, gravimetric assessment of blood loss is more accurate in both simulated scenarios and real time studies 24–26 . Both volumetric and gravimetric are forms of quantitative measurement; studies have shown that when used in combination, the accuracy of blood loss assessment is improved 27 .…”

“…Both volumetric and gravimetric are forms of quantitative measurement; studies have shown that when used in combination, the accuracy of blood loss assessment is improved 27 . Gravimetric blood loss assessment requires minimal resources and is a cost‐effective method of assessing PPH 25 . However, it can be labour intensive, requiring a designated member of staff trained in the process.…”