Prospective Observational Investigation of Capnography and Pulse Oximetry Monitoring After Cesarean Delivery With Intrathecal Morphine

BACKGROUND: Intrathecal morphine provides excellent analgesia after cesarean delivery; however, respiratory events such as apnea, bradypnea, and hypoxemia have been reported. The primary study aim was to estimate the number of apneas per subject, termed "apnea alert events" (AAEs) defined by no breath for 30–120 seconds, using continuous capnography in women who underwent cesarean delivery. METHODS: We performed a prospective, observational study with institutional review board approval of women who underwent cesarean delivery with spinal anesthesia containing 150-µg intrathecal morphine. A STOP-Bang obstructive sleep apnea assessment was administered to all women. Women were requested to use continuous capnography and pulse oximetry for 24 hours after cesarean delivery. Nasal sampling cannula measured end-tidal carbon dioxide (EtCO2) and respiratory rate (RR), and oxygen saturation (SpO2) as measured by pulse oximetry. Capnography data were defined as "valid" when EtCO2 >10 mm Hg, RR >5 breaths per minute (bpm), SpO2 >70%, or during apnea (AAE) defined as "no breath" (EtCO2, 30 kg/m2/weight >90 kg, and 11% with suspected obstructive sleep apnea (known or STOP-Bang score >3). The duration of normal capnography and pulse oximetry data was mean (SD) (range) 8:28 (7:51) (0:00–22:32) and 15:08 (6:42) (1:31–23:07) hours:minutes, respectively; 6 women did not use the capnography. There were 198 AAEs, mean (SD) duration 57 (27) seconds experienced by 39/74 (53%) women, median (95% confidence interval for median) (range) 1 (0–1) (0–29) per subject. Observation of RR by nurses was ≥14 bpm at all time-points for all women, r = 0.05 between capnography and nurse RR (95% confidence interval, −0.04 to 0.14). There were no clinically relevant adverse events for any woman. Sixty-five women (82%) had complaints with the capnography device, including itchy nose, nausea, interference with nursing baby, and overall inconvenience. CONCLUSIONS: We report 198 AAEs detected by capnography among women who underwent cesarean delivery after receiving intrathecal morphine. These apneas were not confirmed by the intermittent hourly nursing observations. Absence of observer verification precludes distinction between real, albeit nonclinically significant alerts with capnography versus false apneas. Discomfort with the nasal sampling cannula and frequent alerts may impact capnography application after cesarean delivery. No clinically relevant adverse events occurred. Accepted for publication April 26, 2018. Funding: This study was supported by an Investigator Research Grant (VT ID# ISR-2013–10323) from Medtronic, which provided financial support and the capnography equipment. The funding body had no role in the study design, raw data extraction and processing, data analysis or interpretation, writing of the manuscript, or manuscript submission for publication. Conflicts of Interest: See Disclosures at the end of the article. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's website (https://ift.tt/KegmMq). This study was conducted at the Lucile Packard Children's Hospital, Stanford, California. Clinical trial number: clinicaltrials.gov (NCT02417038; April 10, 2015). Institutional review board: Shana Stolarczyk, Research Compliance Office, Stanford University, 3000 El Camino Real, Five Palo Alto Sq, 4th Floor, Palo Alto, CA 94306. E-mail: irbeducation@lists.stanford.edu; Shana.Stolarczyk@stanford.edu. Reprints will not be available from the authors. Address correspondence to Carolyn F. Weiniger, MBChB, Division of Anesthesia, Critical Care and Pain, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel. Address e-mail to carolynfweiniger@gmail.com. © 2018 International Anesthesia Research Society

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