Abstract
BackgroundPregnancy is associated with higher incidence of failed endotracheal intubation and is exacerbated by labor. However, the influence of labor on airway outcomes with laryngeal mask airway (LMA) for cesarean delivery is unknown.MethodsThis is a secondary analysis of a prospective cohort study on LMA use during cesarean delivery. Healthy parturients who fasted > 4 h undergoing Category 2 or 3 cesarean delivery with Supreme™ LMA (sLMA) under general anesthesia were included. We excluded parturients with BMI > 35 kg/m2, gastroesophageal reflux disease, or potentially difficult airway (Mallampati score of 4, upper respiratory tract or neck pathology). Anesthesia and airway management reflected clinical standard at the study center. After rapid sequence induction and cricoid pressure, sLMA was inserted as per manufacturer’s recommendations. Our primary outcome was time to effective ventilation (time from when sLMA was picked up until appearance of end-tidal carbon dioxide capnography), and secondary outcomes include first-attempt insertion failure, oxygen saturation, ventilation parameters, mucosal trauma, pulmonary aspiration, and Apgar scores. Differences between labor status were tested using Student’s t-test, Mann-Whitney U test, or Fisher’s exact test, as appropriate. Quantitative associations between labor status and outcomes were determined using univariate logistic regression analysis.ResultsData from 584 parturients were analyzed, with 37.8% in labor. Labor did not significantly affect time to effective ventilation (mean (SD) for labor: 16.0 (5.75) seconds; no labor: 15.3 (3.35); mean difference: -0.65 (95%CI: − 1.49 to 0.18); p = 0.1262). However, labor was associated with increased first-attempt insertion failure and blood on sLMA surface. No reduction in oxygen saturation or pulmonary aspiration was noted.ConclusionsAlthough no significant increase in time to effective ventilation was noted, labor may increase the number of insertion attempts and oropharyngeal trauma with sLMA use for cesarean delivery in parturients at low risk of difficult airway. Future studies should investigate the effects of labor on LMA use in high risk parturients.Trial registrationThe study was prospectively registered at clinicaltrials.gov (NCT02026882) on 3 January 2014.
Highlights
Pregnancy is associated with higher incidence of failed endotracheal intubation and is exacerbated by labor
Labor has been associated with anatomical changes that increase the likelihood of difficult intubation, and Mallampati scores after labor were 1 to 2 grades higher compared to pre-labor, with a greater proportion of parturients possessing Mallampati scores of 3 or 4 [6, 7]
Labor was associated with increased Category 2 cesarean delivery and longer surgical duration
Summary
Pregnancy is associated with higher incidence of failed endotracheal intubation and is exacerbated by labor. Pregnancy is associated with higher risk of failed endotracheal intubation, with an estimated incidence of 1:250 compared to 1:2000 in non-pregnant patients [1, 2]. Labor significantly decreases oropharyngeal area and volume, which may further impede endotracheal intubation [6]. These anatomical changes are attributed to laryngeal edema arising from rapid intravenous fluid administration, antidiuretic effects of oxytocin, and prolonged straining during labor [10]
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