Visual estimation and gravimetric methods are commonly used to quantify the volume of blood loss during cesarean delivery (CD). However, the correlation between blood loss and post-CD hemoglobin (Hb) is poorly studied, and it is unclear whether the correlation varies according to how blood loss is measured.
After obtaining Institutional Review Board approval, we performed a prospective study of 61 women undergoing CD to assess the relations between post-CD Hb and blood loss measured using 4 modalities: gravimetric blood loss measurement (gBL), visual blood loss estimation by a blinded obstetrician (oBL) and anesthesiologist (aBL), and the Triton System (tBL). Hb was measured preoperatively and within 10 minutes after CD. gBL was quantified as blood volume in a suction canister in addition to the weight of blood-soaked sponges. tBL was measured with the Triton System by photographing blood-soaked sponges and suction canister contents. To assess the relation between blood loss and post-CD Hb, we performed correlation analyses and compared the magnitude of the correlations across the 4 measurement modalities using William t test. A Bonferroni correction was set to identify a statistically significant correlation (P < .0125) and statistically significant differences between correlation coefficients (P < .008).
The mean (standard deviation) preoperative Hb was 12 (1.1) g/dL and post-CD Hb was 11.3 (1.0) g/dL. Median (interquartile range) values for gBL, oBL, aBL, and tBL were 672 mL (266–970), 700 mL (600–800), 750 mL (600–1000), and 496 mL (374–729), respectively. A statistically significant but weak correlation was observed between tBL and post-CD Hb (r = −0.33; P = .01). No statistically significant correlations were observed among aBL (r = −0.25; P = .06), oBL (r = −0.2; P = .13), and gBL (r = −0.3; P = .03) with post-CD Hb. We did not detect any significant differences between any 2 correlation coefficients across the 4 modalities.
Given that we observed only weak correlations between each modality with post-CD Hb and no significant differences in the magnitude of the correlations across the 4 modalities, there may be limited clinical utility in estimating post-CD Hb from blood loss values measured with any of the 4 modalities.
From the *Department of Anesthesiology, Perioperative, and Pain Medicine, Stanford University School of Medicine, Stanford, California
†Department of Anesthesiology and Critical Care Medicine, University of New Mexico, Albuquerque, New Mexico.
Published ahead of print 12 April 2018.
Accepted for publication April 12, 2018.
Funding: This study was supported by the Department of Anesthesiology, Perioperative, and Pain Medicine, Stanford University School of Medicine.
Conflicts of Interest: See Disclosures at the end of the article.
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Institutional review board: Stanford University Institutional Review Board, Research Compliance Office, Stanford University, 3000 El Camino Real, Five Palo Alto Sq, 4th Floor, Palo Alto, CA 94306. E-mail: firstname.lastname@example.org.
Clinical Trial Registration: This study was registered at ClinicalTrials.gov. The ClinicalTrials.gov Identifier = NCT02667600 URL: https://clinicaltrials.gov/ct2/show/NCT02667600.
Reprints will not be available from the authors.
Address correspondence to Alexander J. Butwick, MBBS, FRCA, MS, Department of Anesthesiology, Perioperative and Pain Medicine (MC: 5640), Stanford University School of Medicine, 300 Pasteur Dr, Stanford, CA 94305. Address e-mail to email@example.com.