Fire in the OR! How would you have responded? What was done well? What could have been improved upon?
This is a video of a simulation done a number of years ago at the Winter Institute For Simulation Education and Research (WISER) at the University of Pittsburg. It is used with permission of Laederal Corporation and the WISER simulation center.
Video courtesy of WA Kofke M.D.
Airway management for Cesarean section is a common question on the American Anesthesiology Written Board or In training exam. Valerie Arkoosh, M.D., reviews the approach to this complex clinical challenge. Emergency C/S: Difficult Airway. Anesthesia-related maternal mortality is the 7th leading cause of maternal morality in the U.S. The ASA Closed Claims Analysis found that 23% of the damaging events associated with obstetrical general anesthesia were due to difficult tracheal intubation and esophageal intubation. Other problems included aspiration of gastric contents, inadequate ventilation and respiratory failure. Incidence of failed intubation in OB is estimated at 1 in 280. Compounding the difficulty is the urgency of many situations and the needs of the fetus.
Relevant anatomic and physiologic changes during pregnancy include: upper airway edema (changes in voice often a clue to this), breast enlargement, excessive weight gain, cephalad displacement of diaphragm, decreased functional residual capacity, increased oxygen consumption, increased risk of aspiration (incompetence of the gastroesophageal junction due to shift in the position of the stomach, progesterone-mediated decrease in gastroesophageal smooth muscle tone, prolonged gastric emptying during labor), and edema associated with preeclampsia.
Prevention: Timely evaluation of the airway prior to an emergency allows for placement of epidural in high-risk parturients. The vast majority of urgent or emergent cesarean sections can be anticipated with regular evaluation of laboring patients. Ongoing communication between the obstetric and anesthesia teams is essential for prevention of disasters.
Airway Assessment: Mallampati Class (may advance during pregnancy and during labor), atlanto-occipital joint extension (normal = 35 degrees), thyromental distance (>6.5 cm = reassuring, <6 cm = likely difficult/impossible), and ability to protrude the mandible anterior to the front of the upper incisors are used. There is a risk of difficult laryngoscopy in pregnant women (>90%) if the following combination is present: Mallampati III or IV, protruding maxillary incisors, short neck and receding mandible.
Difficult airway identified, regional anesthesia contraindicated/impossible, now what? Cesarean Section – non-emergent: Administer aspiration prophylaxis and drying agent such as glycopyrrolate, consider awake oral fiberoptic intubation, awake look via direct laryngoscopy or the use of other specialized scopes depending upon your skill and availability of equipment. Position: Patient should be “ramped” with head, upper body and shoulders elevated above the chest. Equipment: Smaller ETTs should be utilized due to airway edema. The recommend size is 6.5 or smaller. Avoid nasal airways if possible due to increased risk of significant epistaxis.
Cesarean section – emergent, unanticipated difficult airway: Administer aspiration prophylaxis as time allows (Bicitra usually possible), position carefully. If the first attempt at intubation fails a more experienced person should make the next attempt. A call for additional help (including surgical airway experts), smaller ETT, different blade, gum elastic bougie, repositioning should all be considered. DO NOT make more than three attempts at direct laryngoscopy as this may increase upper airway edema and make ventilation impossible. Mask ventilation will be required in between each attempt at intubation due to the rapid oxygen desaturation experienced by pregnant women. Consider use of an oral airway and jaw thrust maneuvers to facilitate ventilation. After three attempts, mask ventilation with cricoid pressure should be initiated. If fetus/mother stable, patient can be ventilated until awake. If fetus/mother not stable, delivery can proceed with mask ventilation and cricoid. An LMA or other airway device may also be placed at this time. Cricoid pressure will need to be released during LMA placement then re-established. If mask ventilation is not possible, an LMA should be tried first. The LMA has a very high success rate in ventilating the obstetric patient. The Combitube is also an option. If ventilation proves impossible, transtracheal jet ventilation should be instituted. A route for exhalation through the mouth or nose must be established to avoid barotrauma.
Cesarean section – emergent, known difficult airway: Consider regional (spinal or continuous spinal with an epidural catheter). This may be faster than any other option. Surgeons may also proceed with local anesthesia (Busby T: Local anesthesia for cesarean section. Am J Obstet Gynecol 1963; 87:399-404). Consider emergency surgical airway. Induction of general anesthesia should be the last resort and emergency airway equipment and surgical support should be immediately available. The ASA guidelines for Difficult Airway Management apply also to the parturient and need to be followed. Additional reference Crit Care Med 2005; 33[Suppl.]:S259-S268.
Valerie Arkoosh, M.D., MPH is Professor of Clinical Anesthesiology and Critical Care at the University of Pennsylvania. Her subspeciality interest is Obstetrical Anesthesia
