Efficacy of noninvasive pulse co-oximetry as compared to invasive laboratory-based hemoglobin measurement during spinal anesthesia

Abstract

Background: The Masimo Radical 7 (Masimo Corp., Irvine, CA,USA) pulse co-oximeterⓇ noninvasively determines the hemoglobinconcentration using the principle of transcutaneous spectrophotometry. We compared hemoglobin levels determined using thisdevice (SpHb) with those determined using an invasive laboratory-based technique (tHb) during spinal anesthesia. Methods: Thirty patients received spinal anesthesia with 0.5%hyperbaric bupivacaine. The pulse co-oximeter probe was mountedon the second toe, and arterial blood samples were obtained froma radial artery catheter. SpHb, tHb, and perfusion index (PI) valueswere recorded before and 20 and 40 min after intrathecal injectionof bupivacaine. Results: Before spinal anesthesia, the SpHb and tHb showed asignificant difference of −2.86 ± 1.56 g/dl (P ＜ 0.005), but nosignificant differences were found between tHb and SpHb at 20 and40 min after spinal anesthesia (−0.16 ± 2.45 g/dl and 0.29 ± 2.68g/dl). Additionally, PI was significantly increased at 20 and 40 minafter spinal anesthesia compared to the pre-anesthetic value (P ＜0.001). Conclusions: The toe is not the monitoring site for pulseco-oximetry in adult patients, but the pulse co-oximetry on the toeappears to be appropriate as a noninvasive hemoglobin monitoringdevice after spinal anesthesia.