Pulse oximetry-guided rational use of oxygen in patients for ambulatory surgical procedures under spinal anesthesia

ABSTRACT

Background: In an effort to prevent and address perioperative hypoxemia, it has become customary to provide supplemental oxygen to all surgical patients. Recently, the value of such a practice has been questioned. This study was designed to determine the incidence as well as the potential risk factors associated with perioperative hypoxemia. Methods: During a 9 - week period, 84 ASA I-II patients who underwent ambulatory surgical procedures under spinal anesthesia were observed. Arterial oxygen saturation (SpO2) was monitored using a pulse oximeter prior to induction of anesthesia, during operation and until the patient was discharged from the recovery room. Patients breathed room air during the entire perioperative course unless dyspnea and/or desaturation occurred. Descriptive statistics was used to examine differences in oxygen saturations before, during, and after surgery. The association between each of the potential risk factors and the number of patients requiring supplemental oxygen was analyzed using Fisher's exact test (for attribute data e.g. level of sensory block) and the Wilcoxon's rank sum test for continuous data (e.g. age, smoking in pack years) to calculate the probability that the proportions did not differ. A/>< 0.05 was considered statistically significant. Results: The incidence of preoperative, intra-operative and postoperative hypoxemia was 0 percent, 0 percent and 1.14 percent respectively while the need for supplemental oxygen was 2.27 percent intra-operatively and 2.27 percent postoperatively. Statistical analysis revealed that the level of block and body mass index were significant factors (P < 0.05) influencing the need for oxygen support. The need for supplemental oxygen was not associated with age, smoking history, surgical position, sedation level and Visual Analog Scale score. Conclusion: Results suggest that seemingly healthy patients who undergo lower abdominal, urologic, gynecologic or lower extremity surgical procedures under spinal anesthesia are at a low risk for hypoxemia. Pulse oximetry as part of routine monitoring may obviate the need for supplemental oxygen in this patient population. (Author)