JOURNAL OF THE LOUISIANA STATE MEDICAL SOCIETY
Table 1: Risk Factors for Pulmonary Aspiration Risk Factor
Conditions where risk factors exist
Patient factors
Emergency surgery Inadequate fasting time Gastrointestinal obstruction
Full stomach
Systemic disease (e.g., diabetes mellitus, chronic kidney disease) Recent trauma Opioids Raised intra-cranial pressure
Delayed gastric emptying
Previous gastrointestinal surgery Pregnancy (including active labor)
Incompetent lower esophageal sphincter
Hiatal hernia Recurrent regurgitation Dyspepsia Previous upper gastrointestinal surgery Pregnancy Previous gastrointestinal surgery Morbid obesity
Figure 2. Noncontrast CT scan of the abdomen and pelvis, sagittal view, demonstrating a distended stomach (S).
Esophageal diseases
Surgical factors
-
Upper gastrointestinal surgery Lithotomy or head down position Laparoscopy Cholecystecomy Light anaesthesia Supraglottic airways Positive pressure ventilation Length of surgery > 2 hours Difficult airway First generative supra- glottic airway devices
The patient was scheduled for immediate laparoscopic appendectomy.TheCTscanwasreviewedbytheanesthesiologist preoperatively. In addition to appendix rupture and free peritoneal fluid, the CT scan demonstrated a full stomach posing significant risks of pulmonary aspiration on induction of general anesthesia. The anesthesiologist inserted a nasogastric (NG) tube (Salem Sump, #16 French) and drained 900 milliliters of dark green fluid from the stomach. An additional 600 ml of gastric contents was drained intraoperatively. The anesthetic and laparoscopic appendectomy proceeded uneventfully, and the patient was discharged from the hospital on postoperative day two.
Anaesthetic factors
-
Device factors
-
Table 1. Risk factors for pulmonary aspiration [2] (Table borrowed with permission from Continuing Education in Anaesthesia, Critical Care, & Pain 2014; 14.4: 171-175)³
DISCUSSION
Pulmonary aspiration is a significant cause of anesthesia- associated airway related mortality. Preoperative review of recent abdominal imaging may permit early placement of a NG tube to relieve gastric distention and reduce the risks of intraoperative pulmonary aspiration. Although gastric distension is a major risk factor for pulmonary aspiration, other risk factors predispose patients to aspiration risks and often coexist with gastric distension. In 2004, Asai reviewed the major risk factors for pulmonary aspiration (Table 1).³ Table 2 summarizes the available strategies for reducing aspiration risk.³ When gastric distension and aspiration risk are suspected, patients are typically scheduled for rapid sequence endotracheal intubation (RSI). During the procedure, positive pressure ventilation is avoided and anterior cricoid pressure is applied to gently seal the esophagus against the cervical spine and to limit the risk of aspiration. Despite becoming a standard of care, RSI remains controversial. There remains no consensus on the best physical maneuvers and the best intravenous anesthetics to support RSI. There is also no consensus on the risks and benefits of avoiding positive pressure ventilation and applying cricoid pressure during RSI.⁵-⁶
Table 2: A summary of the available strategies for reducing aspiration risk Mode of reducing risk
Mechanism to reduce risk Reducing gastric volume
Preoperative fasting Nasogastric aspiration Prokinetic premedication
Avoidance of general anaesthetic
Regional anaesthetic
Antacids H2 histamine antagonists Proton pump inhibitors
Reducing pH of gastric contents
Trachael intubation Second-generation supra-glottic airway devices
Airway protection
Prevent regurgitation
Cricoid pressure Rapid sequence intubation
Awake after return of airway reflexes Position (lateral, head down, or upright)
Extubation
Table 2. A summary of the available strategies for reducing aspiration risk.²
J La State Med Soc VOL 170 JULY/AUG 2018 99
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