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Non-invasive Hemoglobin Measurement during Cesarean Delivery: Has Device Performance Improved?
Abstract Number: F-18
Abstract Type: Original Research
Background: Pulse CO-Oximetry™ (PCO) uses multi-wavelength spectrophotometry for non-invasive hemoglobin (SpHb) measurement. In studies of women undergoing cesarean delivery (CD) first generation PCO technology was found to be too unreliable for measuring venous hemoglobin concentration (vHb).(1,2) In recent years PCO technology has been refined but it is uncertain whether device performance has improved in the obstetric setting. We present an interim analysis describing the accuracy of intraoperative SpHb measurement relative to vHb values during CD.
Methods: After gaining IRB approval and patient consent, 42 healthy term women undergoing elective CD with neuraxial anesthesia were enrolled in an ongoing prospective study. SpHb values were measured using Masimo Resposable probes (R1 25) and Radical-7 PCO (version 184.108.40.206). SpHb values were compared to vHb values, analyzed by laboratory CO-Oximetry (Beckman Coulter LH 780). To assess the level of agreement between SpHb and vHb, we calculated the bias (mean difference and 95% CI) and limits of agreement (LOA), corrected for repeated measurements using a linear mixed-effects model. We examined for interaction to assess if bias was consistent over time. P <0.05 as statistically significant.
Results: Mean (SD) vHb and SpHb values at baseline were 12.0 (1.1) g/dl and 11.8 (1.0) g/dl respectively, and in PACU were 11.1 (1.2) g/dl and 11.8 (1.0) g/dl respectively. We observed no significant bias between SpHb and vHb (-0.12 g.dl; P=0.33); the 95% CIs were -0.37 and 0.13 g/dl. The LOA were relatively wide: 2.13 g/dl and -2.37 g/dl (Figure). We observed no interaction between bias and the time of measurement (P=0.85).
Conclusion: Refinements in PCO technology may have resulted in reduced bias between SpHb and vHb. However, as reported in prior studies, (1,2) the LOA were relatively wide therefore it remains uncertain whether PCO is clinically reliable during elective CD. Future studies are also needed to determine the accuracy/precision of PCO in the setting of severe maternal anemia and obstetric hemorrhage.
References: (1) Br J Anaesth 2012;108:271-7 (2) Anaesthesia 2013;68:40-5.