Aspiration of gastric contents with subsequent severe chemical pneumonitis (Mendelson syndrome) and/or pneumonia.
Aspiration occurs in the presence of a triad:
- Fluid or solids in the stomach
- Vomiting or passive regurgitation
- Depression of the airway protective reflexes
- Breach of NPO guidelines or emergent (nonelective) surgical procedure
- Acute or chronic, upper or lower, GI pathology (e.g., intestinal obstruction, Barrett esophagus, GERD)
- Obesity; increased risk if bariatric surgery
- Opioid administration, sedation, impaired level of consciousness
- Increased ICP, neurological disease affecting gastric emptying, esophageal sphincter tone, or upper airway reflexes; diabetes with autonomic dysfunction leading to gastroparesis
- Difficult intubation/airway
- Pregnancy beyond 18–20 weeks of gestation
- Preanesthetic ultrasonographic measurement of the antral cross-sectional area (not performed routinely):
- Upright 45°, low-frequency (2–5 MHz) probe
- Antrum imaged in a parasagittal plane in the epigastric area using the left lobe of the liver, the inferior vena cava, and the superior mesenteric vein as internal landmarks
- Anteroposterior and craniocaudal diameters measured
- CSA = (AP × CC × π)/4
- “At-risk” stomach if CSA ≥340 mm2
- H2 antagonist: two oral doses of ranitidine (150 mg)—one the night before surgery and one on the morning of surgery (to decrease gastric acidity)
- Alternatively, nonparticulate antacid (sodium citrate) 30 mL PO before bringing patient to the OR
- It is best to use GA and protect the airway by a cuffed endotracheal tube. Regional anesthesia with minimal sedation can be considered in selected cases, after carefully weighing risks and benefits
- Empty the stomach with a nasogastric tube (if not contraindicated), although this by no means guarantees that there will not be regurgitation of gastric contents. If NGT in place, put in suction and do not remove before induction
- Preoxygenate well (3 minutes or several FVC breaths) until FeO2 above 80%
- Rapid sequence intubation:
- Hypnotic: propofol 2.5 mg/kg (or etomidate 0.3 mg/kg or ketamine 3–4 mg/kg if concern about hemodynamic stability)
- Succinylcholine 1 mg/kg (do not “precurarize” with a nondepolarizing agent to avoid fasciculations, as this will delay onset of NMB)
- Rocuronium if contraindication to succinylcholine (hyperkalemia, allergy, myopathy, paraplegia/tetraplegia, absent/abnormal plasma pseudocholinesterase) in patient not at risk for difficult intubation: 0.6–0.9 mg/kg
- Sellick maneuver: probably not very effective but little potential to harm:
- The cricoid cartilage is pushed against the body of the sixth cervical vertebra, compressing the esophagus to prevent passive regurgitation
- The cricoid cartilage can be located inferior to the thyroid prominence and cricothyroid membrane
- Cricoid pressure is applied before intubation, immediately after injection of induction medications, and should not be released until ETT position is confirmed by EtCO2 and auscultation
- The cricoid cartilage should be fixed between digits and then pressed backwards at a force of 20–30 N (training with a sealed 50 mL syringe: compression of the syringe to 34 mL approximates 30 N of pressure)
- Cricoid pressure must be released if active vomiting supervenes, to reduce the risk of ...
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