Clinical Indicators of the Need for Telemetry Postoperative Monitoring in Patients With Suspected Obstructive Sleep Apnea Undergoing Total Knee Arthroplasty

Background and Objectives: Obstructive sleep apnea is associated with increased complication rates postoperatively. Current literature does not provide adequate guidance on management of these patients. This study used the STOP-Bang questionnaire to diagnose patients with possible obstructive sleep apnea (score >= 3). We hypothesized that a STOP-Bang score of 3 or greater would significantly correlate with the number of oxygen desaturation episodes during the first 48 hours after total knee arthroscopy. Methods: The STOP-Bang questionnaire was administered to 110 patients preoperatively. All patients underwent spinal-epidural anesthesia with a saphenous nerve block and sedation and were connected to the Nellcor OxiMax N-600x pulse oximeter for 48 hours postoperatively. Results: Final analysis included 98 patients. There was no significant difference in the total number of desaturation events between STOP-Bang groups (score <3 vs >= 3 and score <5 vs >= 5). The total number of desaturation events on postoperative day 1 was greater than that on day 0 (32.8 +/- 42.7 vs 4.1 +/- 10.0, P < 0.0001). The total number of desaturation events correlated with length of hospital stay (r = 0.329, P = 0.0001). Patients with a preoperative serum CO2 of 30 mmol/L or greater had significantly longer episodes of desaturation on postoperative day 0 compared with CO2 of less than 30 mmol/L (233.7 +/- 410.1 vs 82.0 +/- 126.2 seconds, P = 0.044). Conclusions: A high preoperative value of CO2 should be a warning for possible prolonged episodes of desaturation postoperatively. An attempt to limit postoperative desaturation events should be made to minimize length of stay.