39: Aspiration

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CHAPTER 39 Aspiration

Malcolm Packer, MD

1 What is aspiration and what differentiates aspiration pneumonitis from aspiration pneumonia?

Aspiration is the passage of material from the pharynx into the trachea. Aspirated material can originate from the stomach, esophagus, mouth, or nose. The materials involved can be particulate such as food or a foreign body or fluid such as blood, saliva, or gastrointestinal contents. Aspiration of gastric contents may occur by vomiting, which is an active propulsion from the stomach up the esophagus, or by regurgitation, which is the passive flow of material along the same path.

Aspiration pneumonitis describes the initial imflammatory response after aspiration, and aspiration pneumonia describes the consolidation along with the imflammation.

2 How often does aspiration occur and what is the morbidity and mortality rate?

The results of several different retrospective and prospective surveys of adult anesthetics place the incidence at one to seven cases of significant aspiration per 10,000 anesthetics. Studies of children’s anesthetics demonstrate about twice that occurrence. The average hospital stay is 21 days, much of which is in intensive care. Complications range from bronchospasm and pneumonia to acute respiratory distress syndrome, lung abscess, and empyema. The average mortality rate is 5%.

3 What are risk factors for aspiration?

image Extremes of age
image Emergency cases
image Type of surgery (most common in cases of esophageal, upper abdominal, or emergency laparotomy surgery)
image Recent meal (Preoperative fasting guidelines for elective surgery are discussed in Chapter 17.)
image Delayed gastric emptying and/or decreased lower esophageal sphincter tone (diabetes, gastric outlet obstruction, hiatal hernia
image Medications (e.g., narcotics, anticholinergics)
image Trauma
image Pregnancy
image Pain and stress
image Depressed level of consciousness
image Morbid obesity (including after bariatric surgery and the resulting weight loss)
image Difficult airway
image Neuromuscular disease (impaired ability to protect the trachea)
image Esophageal disease (e.g., scleroderma, achalasia, diverticulum, Zenker’s diverticulum)

4 What precautions before anesthetic induction are required to prevent aspiration or mollify its sequelae?

The main precaution is to recognize which patients are at risk. Patients should have an adequate fasting period to improve the chances of an empty stomach. Gastrokinetic medications such as metoclopramide have been thought to be of benefit because they enhance gastric emptying, but no good data support this belief. It is helpful to increase gastric pH by either nonparticulate antacids such as sodium citrate or histamine-receptor (H2) antagonists, which decrease acid production. The market now includes several H2 antagonists, giving anesthesiologists a choice (e.g., cimetidine, ranitidine, and famotidine). Cimetidine was first on the market and is still widely used. Although cimetidine increases gastric pH, it also has a significant side-effect profile, including hypotension, heart block, central nervous dysfunction, decreased hepatic blood flow, and significant retardation of the metabolism of many drugs. Ranitidine, a newer H2 antagonist, is much less likely to cause side effects; only a few cases of central nervous dysfunction and heart block have been reported. Famotidine is equally as potent as cimetidine and ranitidine and has no significant side effects. To be effective at induction, H2 blockers must be administered 2 to 3 hours before the procedure, although medications given near the time of induction may have some benefit after extubation. The use of proton pump inhibitors in place of or in concert with H2 antagonists has not proven to be more efficacious. The use of orogastric or nasogastric drainage preinduction is most effective in patients with intestinal obstruction.

5 How might a patient with a difficult airway and at risk for aspiration be managed?

A regional anesthetic is a desirable alternative when appropriate for the surgery and has been shown to definitely be of value in the setting of cesarean section, during which the patient population is definitely at risk for aspiration. A rapid sequence with cricoid pressure is preferred when a general anesthetic is needed and the patients are thought not to have a difficult airway. Discussions on the efficacy and potential hazards of cricoid pressure continue, but to date is usually recommended for rapid sequence intubations.

Patients with difficult airways may require placement of an endotracheal tube while awake to allow spontaneous breathing and protect the airway from aspiration. Awake intubations are facilitated by devices such as light wands, fiberoptic bronchoscopes, and retrograde intubation kits. Patient comfort is aided by the judicious use of sedation and topical local anesthetic. Oversedation and a topicalized airway may make the patient unable to protect the airway. Therefore keeping the patient conscious and applying topical local anesthetic only to the airway above the glottis lead to safe intubation. Endotracheal intubation does not guarantee that no aspiration will occur. Material may still slip past a deflated or partly deflated cuff.

6 Describe the different clinical pictures caused by the three broad types of aspirate: acidic fluid, nonacidic fluid, and particulate matter

image Acidic aspirates with a pH less than 2.5 and volumes of more than 0.4 ml/kg immediately cause alveolar-capillary breakdown, resulting in interstitial edema, intra-alveolar hemorrhage, atelectasis, and increased airway resistance. Hypoxia is common. Although such changes usually start within minutes of the initiating event, they may worsen over a period of hours. The first phase of the response is direct reaction of the lung to acid; hence the name chemical pneumonitis. The second phase, which occurs hours later, is caused by a leukocyte or inflammatory response to the original damage and may lead to respiratory failure.
image Aspiration of nonacidic fluid destroys surfactant, causing alveolar collapse and atelectasis. Hypoxia is common. The destruction of lung architecture and the late inflammatory response are not as great as in acid aspiration.
image Aspiration of particulate food matter causes both physical obstruction of the airway and a later inflammatory response related to the presence of a foreign body. Alternating areas of atelectasis and hyperexpansion may occur. Patients show hypoxia and hypercapnia caused by physical obstruction of airflow. If acid is mixed with the particulate matter, damage is often greater, and the clinical picture worse.

7 Review the clinical signs and symptoms after aspiration

Fever occurs in over 90% of aspiration cases, with tachypnea and rales in at least 70%. Cough, cyanosis, and wheezing occur in 30% to 40% of cases. Aspiration may occur silently—without the anesthesiologist’s knowledge—during anesthesia. Any of the previous clinical deviations from the expected course may signal an aspiration event. Radiographic changes may take hours to occur and may be negative, especially if performed soon after an event.

8 When is a patient suspected of aspiration believed to be out of danger?

The patient who shows none of the previous signs or symptoms and has no increased oxygen requirement at the end of 2 hours should recover completely.

9 Describe the treatment for aspiration

Any patient who is thought to have aspirated should receive a chest radiograph and, at a minimum, many hours of observation. Supportive care remains the mainstay. Immediate suctioning should be instituted. Supplemental oxygen and ventilatory support should be initiated if respiratory failure is a problem. Patients with respiratory failure often demonstrate atelectasis with alveolar collapse and may respond to positive end-expiratory pressure. Patients with particulate aspirate may need bronchoscopy to remove large obstructing pieces. Antibiotics should not be administered unless there is a high likelihood that gram-negative or anaerobic organisms have been aspirated such as with a bowel obstruction. However, a worsening clinical course over the next few days suggests that a broad-spectrum antibiotic may be indicated. Corticosteroids have not been shown to be helpful in human studies. Lavaging the trachea with normal saline or sodium bicarbonate after aspiration has not been shown to be helpful and may actually worsen the patient’s status.

More aggressive treatments of severe aspiration usually occur in the critical care setting. Surfactant installation, high-frequency occilatory ventilation, nitric oxide, and prone positioning have all shown some promise for certain patients with severe aspirations.

KEY POINTS: Aspiration image

1. Numerous patient subgroups are at increased risk of aspiration, including patients presenting for emergency surgery, those having had a recent meal, those with bowel obstruction or delayed gastric emptying, the obese, trauma or pregnant patients, those having pain or being treated with opioids, and those who cannot protect the airway such as patients with a depressed level of consciousness or neuromuscular disease.
2. Such patients may require prophylaxis to decrease the severity of aspiration should it occur, and medications valuable for decreasing the acidity of gastric secretions include nonparticulate antacids, H2 blockers, and proton pump inhibitors given at an interval before surgery appropriate to their onset of action. Patients with bowel obstruction should receive gastric decompression before anesthetic induction.
3. Regional anesthetics are ideal for patients at risk for aspiration if appropriate. A rapid-sequence induction with cricoid pressure is the technique of choice when general anesthesia is required in patients with manageable airways. Awake intubation may be necessary in patients with difficult airways.
4. Should aspiration occur, the treatment is mostly supportive.

SUGGESTED READINGS

1. Cohen N.H., Yanakakis M. Is there an optimal treatment for aspiration? In: Fleisher L.A., editor. Evidence-based practice. Philadelphia: Saunders; 2004:125-129.

2. Jean J., Compère V., Fourdrinier V. The risk of pulmonary aspiration after weight loss due to bariatric surgery. Anesth Analg. 2008;107:1257-1259.

3. Kluger M., Visvanathan T., Myburgh J. Crisis management during anesthesia: regurgitation, vomiting and aspiration. Qual Saf Health Care. 2005;14:4-9.

4. Marrano G., Marco L. Selected medicated (saline vs. surfactant) bronchoalveolar lavage in severe aspiration syndrome in children. Pediatr Crit Care Med. 2007;8:476-481.

5. Neelakanta G., Chikyarapra A. A review of patients with pulmonary aspiration of gastric contents during anesthesia reported to the departmental quality assurance committee. J Clin Anesth. 2006;18:102-107.

6. Tasch M. What reduces the risk of aspiration? In: Fleisher L.A., editor. Evidence-based practice. Philadephia: Saunders; 2004:118-124.

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