Background:
Aspiration is defined as either passive or active entrance of either oropharyngeal or gastric contents through the glottic opening and into the distal airways of the lung. Predisposing conditions and risk factors of aspiration include reduced consciousness (resulting in compromised cough reflex and glottic closure), dysphagia or neurological deficits, mechanical disruption of glottic closure and/or lower esophageal sphincter closure (e.g. endotracheal tube, nasogastric tube), and existence of a large reservoir of gastric contents with active emesis. The following case presentation explores these predisposing factors, and offers options to both the prevention and treatment of massive aspiration.
Case Presentation:
A 75 year-old Caucasian male with Parkinson's Disease presented with chest pain, nausea, and minimal emesis was found by CT to have a large incarcerated type IV paraesophageal hernia with organoaxial rotation/volvulus and gastric outlet obstruction at the level of the gastroduodenal junction. The patient was brought to the OR for emergent endoscopic decompression. An airway exam revealed narrow mouth opening and a Mallampati class IV airway. Given the small amount of emesis reported, and last oral intake reportedly 2 days prior to surgery, a rapid sequence fiberoptic intubation was chosen. During induction, intubation was complicated by inability to visualize the glottic opening, followed immediately by a large volume of emesis that required suctioning before an endotracheal tube could be secured. After establishing an airway, aspirated gastric contents were noted in copious amounts, and suctioned from the endotracheal tube. 700 mL of regurgitant volume was suctioned from the oropharynx and the trachea together, and an additional 2 liters of gastric contents were suctioned from the stomach during the procedure. Post operatively, the patient's massive aspiration resulted in acute hypoxic respiratory failure, evident by the initial ABG pH 7.32, pCO2 43, pO2 <55, and bicarbonate 22.3 on 100% FiO2 while intubated. CXR revealed patchy bilateral airspace opacities consistent with aspiration pneumonia and developing ARDS. In the Critical Care Unit, the patient was started on methylprednisolone and cisatricurium on post-operative day 1 for ARDS. On post-operative day 2 he was proned in 16 hour increments until his shunt fraction decreased to less than 25%, which lasted approximately 5 days. The patient was discharged on POD 19, and received surgery 2 months later for more definitive hernia repair.
Discussion:
Prevention of massive aspiration during anesthesia starts with proper choice of induction technique, in this case awake vs asleep rapid sequence fiberoptic intubation. Prior suctioning via an NG tube may be considered but can be complicated by potential perforation, particularly in the case of existing volvulus and ischemia. For this case, intervention through early pronation and ARDS protocol before clinical deterioration resulted in a positive outcome. Calculation of shunt fractions for guidance of pronation in addition to ARDS protocol may also provide morbidity/mortality benefit.
Primary avoidance and prevention of massive aspiration in the setting of anesthetic use is obtained through careful selection of induction technique. Treatment of a massive aspiration with early pronation and vigilant lung protective ventilation appear to be vital for improved outcomes.
