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Noninvasive Hemoglobin Monitoring in Patients at High Risk for Excessive Bleeding during Cesarean Section
Abstract Number: S 6
Abstract Type: Original Research
If accurate, noninvasive continuous hemoglobin monitoring by Pulse CO-Oximetry (SpHb) has the potential to detect blood loss during cesarean deliveries sooner than intermittent blood sampling. Our objective was to assess the accuracy of SpHb compared to laboratory hemoglobin measurement (Hb) in women at high risk of excessive bleeding during cesarean deliveries.
Women scheduled for cesarean sections (C/S) and determined to be at high risk for excessive perioperative bleeding were enrolled. As per routine, a preoperative Hb was collected for all enrolled patients. An adhesive SpHb sensor attached to a Pulse CO-Oximeter (R2-25 rev E, F, G, connected to a Radical-7, Masimo, Irvine, CA) was placed on a finger with good pulsatile signal and covered with a light shield. Anesthesia care was at the discretion of the attending physician. If during the procedure a patient required a blood transfusion, the anesthesiologist recorded the time the decision was made, the estimated blood loss, the expected Hb at that time and any changes in vital signs. Additionally, a blood sample was sent to the lab for Hb measurement (LH-750, Beckman Coulter Inc., Brea, CA). At the conclusion of the procedure a blood sample was sent to the lab for Hb measurement. This occurred no sooner than one hour after delivery of the placenta. Bias and standard deviation of the bias of SpHb to Hb were calculated and a Bland Altman graph was plotted.
Results: Twenty eight patients, aged 18-42 years, were enrolled. Six patients received a blood transfusion. After discarding 5 paired samples due to low signal quality, the bias and standard deviation of the bias for the 35 paired samples collected was 1.3±1.3 g/dL.
Bland Altman graph had limits of agreement of -1.1 to 3.8 g/dL (Fig 1).
Conclusion: Clinical estimation of blood loss, and estimation of Hb as a correlate, is difficult. This is especially true in patients undergoing C/S where physiologic changes of pregnancy must be taken into account when making decisions about transfusion. SpHb monitoring had clinically acceptable bias and trending but tended to overestimate Hb. We found SpHb monitoring to be a useful tool in our population of women at high risk of excessive bleeding during cesarean deliveries.