From the *Department of Anesthesiology, Northwestern University Feinberg School of Medicine, Chicago, Illinois; and †Department of Anesthesia, University of Iowa Carver College of Medicine, Iowa City, Iowa.
Anesth Analg. 2017 Mar;124(3):872-878. doi: 10.1213/ANE.0000000000001751.
Neuraxial morphine is the most commonly used analgesic technique after cesarean delivery. The incidence of respiratory depression is reported to be very low (0%-1.2%) in this patient population as measured by pulse oximetry and respiratory rates. However, hypercapnia may be a more sensitive measure of respiratory depression. In the current study, the incidence of hypercapnia events (transcutaneous CO2 [TcCO2] >50 mm Hg) for ≥2-minute duration was evaluated using the Topological Oscillation Search with Kinematical Analysis monitor in women who received intrathecal morphine for postcesarean delivery analgesia.
Healthy women (>37 weeks of gestation) scheduled for a cesarean delivery with spinal anesthesia with intrathecal morphine were recruited. Baseline STOP-BANG sleep apnea questionnaire and TcCO2 readings were obtained. Spinal anesthesia was initiated with 12 mg hyperbaric bupivacaine, 15 µg fentanyl, and 150 µg morphine. The Topological Oscillation Search with Kinematical Analysis monitor was reapplied in the postanesthesia care unit and TcCO2 measurements obtained for up to 24 hours. Supplemental opioid administration and adverse respiratory events were recorded. The primary outcome was the incidence of hypercapnia events, defined as a TcCO2 reading >50 mm Hg for ≥2 minutes in the first 24 hours after delivery.
Of the 120 women who were recruited, 108 completed the study. Thirty-five women (32%; 99.15% confidence interval, 21%-45%) reached the primary outcome of a sustained hypercapnia event. The median time (interquartile range [IQR]) from intrathecal morphine administration to the hypercapnia event was 300 (124-691) minutes. The median (IQR) number of events was 3 (1-6) and longest duration of an event was 25.6 (8.4-98.7) minutes. Baseline median (IQR) TcCO2 measurements were 35 (30-0) mm Hg and postoperatively, median (IQR) TcCO2 measurements were 40 (36-43) mm Hg, a difference of 5 mm Hg (99.15% confidence interval of the difference 2-8 mm Hg, P < .001). The incidence of hypercapnia events was 5.4% in women with a baseline TcCO2 value ≤31 mm Hg, 22.5% with a baseline TcCO2 between 32 and 38 mm Hg, and 77.4% with a baseline TcCO2 >38 mm Hg (P < .001).
Hypercapnia events (>50 mm Hg for ≥2-minute duration) occurred frequently in women receiving 150 μg intrathecal morphine for postcesarean analgesia. Higher baseline TcCO2 readings were observed in women who had hypercapnia events.
椎管内吗啡是剖宫产术后最常用的镇痛技术。通过脉搏血氧饱和度和呼吸频率测量，该患者人群的呼吸抑制发生率报告非常低（0%-1.2%）。然而，高碳酸血症可能是呼吸抑制的更敏感指标。在目前的研究中，使用拓扑振荡搜索与运动学分析监测仪评估了 120 名接受鞘内吗啡用于剖宫产术后镇痛的女性中持续 2 分钟以上的高碳酸血症事件（经皮二氧化碳 [TcCO2] >50mmHg）的发生率。
招募了计划接受脊髓麻醉和鞘内吗啡的>37 周妊娠健康女性。获得基线 STOP-BANG 睡眠呼吸暂停问卷和 TcCO2 读数。脊髓麻醉起始于 12mg 布比卡因、15μg 芬太尼和 150μg 吗啡。在麻醉后护理单元重新应用拓扑振荡搜索与运动学分析监测仪，并在 24 小时内获得 TcCO2 测量值。记录补充阿片类药物的使用和不良呼吸事件。主要结局是高碳酸血症事件的发生率，定义为分娩后 24 小时内 TcCO2 读数 >50mmHg 持续 2 分钟以上。
在 120 名被招募的女性中，108 名完成了研究。35 名女性（32%；99.15%置信区间，21%-45%）达到了持续高碳酸血症事件的主要结局。从鞘内吗啡给药到高碳酸血症事件的中位时间（四分位间距 [IQR]）为 300（124-691）分钟。中位（IQR）事件数为 3（1-6），最长持续时间为 25.6（8.4-98.7）分钟。基线中位数（IQR）TcCO2 测量值为 35（30-0）mmHg，术后中位数（IQR）TcCO2 测量值为 40（36-43）mmHg，差值为 5mmHg（99.15%置信区间差值为 2-8mmHg，P<.001）。基线 TcCO2 值≤31mmHg 的女性中高碳酸血症事件的发生率为 5.4%，基线 TcCO2 值在 32-38mmHg 之间的女性为 22.5%，基线 TcCO2 值>38mmHg 的女性为 77.4%（P<.001）。
接受 150μg 鞘内吗啡用于剖宫产术后镇痛的女性中经常发生高碳酸血症事件（持续>2 分钟，>50mmHg）。发生高碳酸血症事件的女性基线 TcCO2 读数较高。
