Risk Factors for Aspiration: Anesthesia and Surgical Considerations

Pulmonary aspiration of gastric contents is a serious perioperative complication that can lead to aspiration pneumonitis, pneumonia, hypoxia, and respiratory failure. Identifying patients at increased risk for aspiration is a critical component of pre-anesthetic evaluation, particularly in office-based anesthesia and maxillofacial surgery.

Aspiration risk is influenced by gastric volume, gastric acidity, impaired protective reflexes, and delayed gastric emptying, as well as patient-specific neurologic and systemic conditions.

Common Risk Factors for Aspiration

Several medical and situational factors increase the likelihood of aspiration during sedation or general anesthesia.

Gastroesophageal reflux disease (GERD) predisposes patients to regurgitation of acidic gastric contents due to lower esophageal sphincter incompetence.

Pregnancy increases aspiration risk because of delayed gastric emptying, increased intra-abdominal pressure, and reduced lower esophageal sphincter tone.

Trauma patients are assumed to have full stomachs due to stress-induced ileus, recent oral intake, and altered mental status.

Diabetes mellitus, particularly when complicated by autonomic neuropathy, can result in gastroparesis. Importantly, diabetic gastroparesis is often asymptomatic and undiagnosed, increasing aspiration risk despite appropriate NPO status.

Recent oral intake, especially fatty or solid meals, directly increases residual gastric volume.

Bowel obstruction and intra-abdominal pathology impair gastric emptying and increase intragastric pressure.

Obesity is associated with increased intra-abdominal pressure, GERD, and reduced functional residual capacity, all of which elevate aspiration risk.

Neurologic and Systemic Conditions Increasing Aspiration Risk

Certain neurologic and autoimmune disorders impair airway protection and swallowing mechanisms.

Parkinson’s disease is a neurodegenerative disorder caused by loss of dopaminergic neurons in the substantia nigra. Clinical features include resting tremor, rigidity, bradykinesia, and postural instability. Advanced disease can impair coordination of swallowing and airway reflexes, increasing aspiration risk.

Myasthenia gravis is an autoimmune disorder of the neuromuscular junction characterized by fatigable weakness of striated muscle. Bulbar weakness leads to impaired swallowing, poor secretion management, and increased aspiration risk. Inspiratory muscle weakness further complicates airway protection.

Systemic lupus erythematosus (SLE) may present anesthetic challenges, including reduced temporomandibular joint range of motion, decreased arytenoid mobility, diaphragmatic dysfunction, pulmonary infiltrates, and reduced pulmonary function tests. These factors contribute to both airway and aspiration risk.

Aspiration Prophylaxis

Aspiration prophylaxis aims to reduce gastric volume and acidity and improve gastric emptying.

Agents commonly used include:

• H2 receptor antagonists (e.g., ranitidine) to decrease gastric acid production

• Non-particulate antacids (e.g., sodium citrate) to neutralize gastric acid and reduce severity of pneumonitis if aspiration occurs

Metoclopramide is a prokinetic agent that:

• Increases gastric emptying

• Increases lower esophageal sphincter tone

• Reduces gastric volume

Metoclopramide is particularly useful in patients with suspected gastroparesis but does not eliminate aspiration risk.

Clinical Importance

Aspiration risk assessment should be integrated with:

• ASA NPO guidelines

• Medication review (e.g., opioids, GLP-1 agonists)

• Airway evaluation

• Planned depth of anesthesia

Patients with multiple risk factors may require modified anesthetic technique, rapid-sequence induction, or postponement of elective surgery.

Board and Exam Pearls

• Diabetes increases aspiration risk via autonomic neuropathy and gastroparesis

• Gastroparesis may be asymptomatic

• Myasthenia gravis increases aspiration risk due to bulbar weakness

• Parkinson’s disease impairs swallowing and airway reflexes

• Sodium citrate reduces acidity, not volume

• Metoclopramide increases gastric emptying and LES tone

Conclusion

Aspiration is a preventable but potentially catastrophic perioperative complication. Careful identification of risk factors, appropriate use of prophylactic agents, and thoughtful anesthetic planning are essential to minimizing aspiration risk and ensuring patient safety.