Continuous surveillance of oxygen saturation and respirations after bariatric surgery

Abstract

Background: Continuous, post-operative patient monitoring can provide healthcare workers with earlier warning signs of patient deterioration. The Masimo Pulse CO-Oximeter (Masimo Corporation, Irvine, CA) has acoustic monitoring technology which measures respiratory rate (RR) by analyzing acoustic signals generated across the upper airway while breathing. We continuously monitored for 19-24 hours (hrs) post-surgery RR and oxygen saturation (SpO2) in obese patients who underwent laparoscopic Roux-en-Y gastric bypass (RYGB) for bariatric surgery weight loss. The objective was to assess incidence of decreased RR (< 10 rpm), respiratory pauses and desaturation (< 90%) in a patient population that is at higher risk for hypoventilation, for an extended time after discharge from Post Anesthesia Care Unit (PACU).
Methods: After Institutional Review Board approval, 20 patients aged 18-65 with a body mass index (BMI) between 40 kg/m2 and 60 kg/m2 who received primary laparoscopic RYGB surgery by the same surgeon were enrolled in this study. After surgery, post-operative pain management included IV patient-controlled anesthesia dilaudid as an adjunct to intraoperative lidocaine infusions (see reference 3). We recorded Visual Analogue Scale (VAS) scores every 3 hrs for 24 hrs. RR and SpO2 were continuously monitored from the time of PACU arrival and for the following 19-24 hrs. The SpO2 alarm was set at 90% and respiratory pause alarm was set at 30 seconds to ensure a rapid response. Floor nurses were alerted immediately when these values were reached. Collected data for SpO2 and RR were graphed versus time for the 24-hr period for each patient in order to evaluate the incidence of low values. The data were then graphed versus time to yield a representation of cumulative time spent at each SpO2 level or respiratory rate. The data were stratified into two ranges for SpO2 (SpO2 90% and < 90%) and three ranges for RR (RR > 30, between 30 and 10, and < 10 breaths per minute). The percentage of time that the patient spent in each range was calculated. Median values were calculated for each category.
Results: During the extended monitoring period, the median percentage of time spent with SpO2 below 90% was 5.4%. The median percentage of time that a subject had a RR of less than 10 respirations/min was 0%. There was no correlation between SpO2 and respiratory rate. Fourteen patients in our study population were on continuous positive airway pressure (CPAP) and reported VAS scores between 3 and 6. This may have prevented them from being deeply sedated. There were no apnea periods longer than 30 seconds.
Conclusions: In this small group of obese patients, a low RR was not encountered during an extended post-operative period. These patients did not experience desaturation, apnea, or significant reductions of RR.