Copyright © 2018 International Anesthesia Research Society. Unauthorized reproduction of this article is prohibited. XXX 2018 • Volume XXX • Number XXX www.anesthesia-analgesia.org 1 DOI: 10.1213/ANE.0000000000003449 KEY POINTS • Question: To evaluate the correlations between blood loss (measured using a gravimetric method, visual estimation by an anesthesiologist, visual estimation by an obstetrician, and the Triton System) and hemoglobin values after elective cesarean delivery. • Findings: We observed a statistically signifcant but weak correlation between blood loss measured by the Triton System and postcesarean hemoglobin (r = −0.33; P = .01), and no statistically signifcant differences in the magnitude of the correlations across the 4 measure- ment modalities. • Meaning: There is limited clinical utility in estimating postcesarean hemoglobin levels from blood loss values measured across the 4 studied measurement modalities. BACKGROUND: 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. METHODS: 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 mea- sured 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 quantifed 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 com- pared the magnitude of the correlations across the 4 measurement modalities using William t test. A Bonferroni correction was set to identify a statistically signifcant correlation (P < .0125) and statistically signifcant differences between correlation coeffcients (P < .008). RESULTS: 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 sta- tistically signifcant but weak correlation was observed between tBL and post-CD Hb (r = −0.33; P = .01). No statistically signifcant 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 signif- cant differences between any 2 correlation coeffcients across the 4 modalities. CONCLUSIONS: Given that we observed only weak correlations between each modality with post-CD Hb and no signifcant 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. (Anesth Analg XXX;XXX:00–00) Assessing the Association Between Blood Loss and Postoperative Hemoglobin After Cesarean Delivery: A Prospective Study of 4 Blood Loss Measurement Modalities Kelly Fedoruk, MD, FRCPC,* Katherine M. Seligman, MD,† Brendan Carvalho, MBBCh, FRCA, MDCH,* and Alexander J. Butwick, MBBS, FRCA, MS* From the *Department of Anesthesiology, Perioperative, and Pain Medicine, Stanford University School of Medicine, Stanford, California; and †Department of Anesthesiology and Critical Care Medicine, University of New Mexico, Albuquerque, New Mexico. 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. Conficts of Interest: See Disclosures at the end of the article. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s website (www.anesthesia- analgesia.org). Institutional review board: Stanford University Institutional Review Board, Research Compliance Offce, Stanford University, 3000 El Camino Real, Five Palo Alto Sq, 4th Floor, Palo Alto, CA 94306. E-mail: irbeducation@lists.stanford.edu. Clinical Trial Registration: This study was registered at ClinicalTrials.gov. The ClinicalTrials.gov Identifer = 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, De- partment of Anesthesiology, Perioperative and Pain Medicine (MC: 5640), Stanford University School of Medicine, 300 Pasteur Dr, Stanford, CA 94305. Address e-mail to ajbut@stanford.edu. Copyright © 2018 International Anesthesia Research Society