The effect of spinal anesthesia on pulse oximetry

Abstract

Background: Pulse oximetry provides valuable data on the arterial oxygen saturation. Significant impairment in the arterial oxygen saturation can occur under vasoconstriction, hypothermia, and hypotension. This study compared the percutaneous oxygen saturation (SpO2) at the hand and the foot with the arterial oxygen saturation (SaO2) during spinal anesthesia. Methods: Twenty eight, ASA physical status 1 or 2, patients received a spinal block with 0.5% hyperbaric bupivacaine. Two pulse oximeter probes were applied to the index finger and second toe of the patients, and the SpO2 values were recorded before, 10, 20, and 30 minutes after the intrathecal injection. The SaO2 was measured before and 30 minutes after the intrathecal injection. Results: During spinal anesthesia, there were similar changes in the SpO2 value from the hand. However, there was a progressive decrease in SpO2 of the foot of 97.6 ± 2.8%, 97.3 ± 2.8%, and 97.2 ± 3.3% at 10, 20, and 30 minutes, respectively (P ＜ 0.05 compared with the baseline). There were significant differences between the hand and foot SpO2 in 20 and 30 minutes (0.79 ± 1.55%, 0.93 ± 1.86%) after the intrathecal injection. The SaO2 value was similar before and 30 minutes after the intrathecal injection. Before spinal anesthesia, there were significant differences between the SaO2 (96.4 ± 2.6%) and SpO2 values of the hand (98.1 ± 2.6%) and the foot (98.3 ± 2.6%). Conclusions: During spinal anesthesia, it is appropriate to measure the SpO2 from the hand because it dose not change significantly. (Korean J Anesthesiol 2008; 55: 700~3)