Unanticipated Difficult Airway Due to Succinylcholine-Induced Masseter Spasm in the Term Parturient
Abstract Number: F-68
Abstract Type: Case Report/Case Series
Though regional anesthesia is preferred for Cesarean delivery, conversion to general anesthesia is occasionally warranted. In these cases, rapid sequence induction with succinylcholine to facilitate intubation is customary. We present a case of unanticipated difficult airway due to succinylcholine-induced masseter spasm.
A 39-year-old G2P0 at 40 weeks EGA underwent Cesarean delivery with labor epidural for failure to progress. Her airway exam was reassuring with favorable 11-point exam, and Mallampati class 2. She was comfortable with incision but experienced discomfort on further dissection. After induction with propofol and succinylcholine, she developed masseter spasm resulting in initially impossible intubation and ventilation. Emergency surgical airway was requested 2 minutes after induction, when initial mask attempts were unsuccessful. Oral intubation was established at 2 minutes 45 seconds when the spasm broke. Nadir oxygen saturation was 65%. Induction-to-delivery time was 7 minutes, and an infant with Apgars 9 and 9 was delivered. The remainder of her intra- and post-operative course was unremarkable.
Masseter spasm after succinylcholine is defined as jaw rigidity with limb flaccidity and results from prolonged depolarization of slow tonic fibers of the masseter and lateral pterygoid. Increased masseter tone after succinylcholine is common, and it is generally mild and transient. In rare, more severe cases, it may result in inability to ventilate and need for emergent surgical airway (1). Though malignant hyperthermia is only associated with extreme cases, vigilance for this entity is essential (2).
Masseter spasm during induction of general anesthesia is particularly concerning in the laboring patient, where a full stomach, hyperemic tissues, decreased functional residual capacity, increased oxygen consumption, and concern for fetal wellbeing complicate a difficult airway. Planning for the unanticipated difficult parturient airway is essential and should include strict adherence to preoxygenation, early call for help (including emergency surgical airway), and communication with the obstetric team about maternal and fetal wellbeing, with possible need for emergent delivery. Research has shown this communication to be difficult, necessitating repetitive practice (3). Familiarity with emergency procedures and adherence to an algorithm ensures the greatest likelihood of positive outcome (4).
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3. Minehart RD, Pian-Smith MC, Walzer TB, Gardner R, Rudolph JW, Simon R, Raemer DB. Simul Healthc 2012;7(3):166-70.
4. Mhyre J, Healy D. The unanticipated difficult intubation in obstetrics. Anesth Analg 2011;112(3):648-52.