The incidence of pulmonary aspiration in anesthesia occurs as often as 1 in every 2,000-3,000 cases. Pulmonary aspiration can be a devastating complication. The incidence of pulmonary aspiration from all causes in the emergency population varies from 1 to 20% depending on the population and situation. The pre-hospital incidence is as high as 39%.
Pulmonary aspiration can be minor or life-threatening. It can potentially cause chemical pneumonitis, aspiration pneumonia, and acute respiratory distress syndrome (ARDS). Aspirating as little as 0.4 ml/kg of pH 2.5 liquid can cause severe pneumonitis. In a 70 kg adult, 0.4 ml/kg is 28 ml, or about 2 tablespoons. Almost half of all patients who aspirate during surgery develop lung related injury.
The 30 day mortality rate of aspiration reaches 10-30% in certain studies.
Pulmonary Aspiration Can Occur At Any Time
We all know that anesthesia itself places patients at risk for aspiration due to:
- the effects of medications on the lower esophageal sphincter
- level of consciousness, and
- loss of protective reflexes.
Therefore, take precautions. One case I had years ago illustrated that a patient can potentially aspirate at any time during an anesthetic, no matter how prepared you are.
30 y.o. female, BMI 33, for ORIF tibial fracture at a free-standing surgery center. NPO 10 hours. History of moderate reflux with large meals. Very nervous and tearful. Surgery had been delayed 2 days to decrease swelling and she had suffered significant pain since the accident. Anesthesia could easily have been performed with a supraglottic airway (SGA). However, the combination of reflux history, obesity, stress, and prolonged pain made me view her as a risk for full stomach.
I premedicated with 2 mg versed and 50 mcg of fentanyl, pre-oxygenated, then induced with 200 mg of I.V propofol, and 80 mg of succinylcholine using rapid sequence induction. I did not place cricoid pressure. The patient vigorously fasciculated, including her abdominal muscles. To my horror, she immediately passively regurgitated a large amount of thick particulate matter into her oro-pharynx.
We turned her onto her side, put the bed into trendelenberg, and suctioned her airway. I intubated easily and suctioned green tinged secretions and some particulate matter out of the endotracheal tube (ETT). Bronchospasm was so severe that we couldn’t hear breath sounds. SPO2 fell into the low 80s. Compliance was extremely poor with peak pressures around 40. I suctioned the ETT again. Since she did not respond to bronchodilators, I immediately turned up the sevoforane, thereby deepening anesthesia in attempt to break the bronchospasm. SPO2 rose to 90. Bronchospasm improved; we could now hear wheezing in all lung fields. There were decreased breath sounds on the left. We had no bronchoscope, therefore we couldn’t examine the lower airway.
Clearly this patient had pulmonary aspiration. We canceled surgery. After stabilizing the situation for 10 minutes, the SPO2 remained steady in the low 90s on 50% FiO2. I started to lighten the plane of anesthesia to see if extubation was possible. An awake patient can cough and clear the airway better than an intubated one.
As anesthesia lightened, wheezing worsened, although SPO2 remained steady in the mid 90s. Ironically, increased wheezing in severe bronchospasm can sometimes indicate improving airflow. The ETT suctioned clear. Sometimes the presence of the ETT itself can stimulate further bronchospasm. Therefore, knowing that she had been an easy intubation, I extubated her when her gag reflex returned.
She remained stable with SPO2 of 89% in the PACU on 6 liters by face mask. We gave additional albuterol as we arranged transfer to the nearest hospital. After several hours in the ICU, she deteriorated and was reintubated. She was extubated next day. Her broken tibia was repaired 2 days later. Afterwards, she suffered no long-term complications and did not develop pneumonia.
Potential Opportunities For Improvement
Feeling that the patient was at risk for aspiration, I could have prescribed preoperative prophylaxis such as metoclopramide or cimetadine to help empty her stomach and increase pH. However, in the surgery center setting, there is often less than 15 minutes between performing a preoperative evaluation and induction of anesthesia. There might, or might not, have been sufficient time for it to work.
I could have had my assistant place cricoid pressure. It is still commonly used in rapid sequence induction despite the lack of clear evidence that it is effective. A more extensive discussion of cricoid pressure below appears below.
Preventing Pulmonary Aspiration in Anesthesia
Be vigilant and prepared. Fast action can often prevent aspiration if your patient vomits.
Ensure you have functional suction, and a yankauer suction catheter — no matter how minor the case. Don’t just look at it, make sure it works. Do this before the first case and check between every case. I have found that failing to check the suction before the day begins risks forgetting to set it up later. Seconds matter when a patient vomits. See:
Recognize Patients At Risk For Aspiration
Any condition producing gastrointestinal stasis and/or obstruction increases the risk of vomiting or passive regurgitation. Passive regurgitation with induction of general anesthesia is far more common than active vomiting. Common predispositions include:
- Gastroparesis from any cause, including drugs, pain, stress, trauma, autonomic dysfunction, or chronic disease process. (Gastroparesis: An Anesthetic Risk)
- Full stomach
- Recent nausea and vomiting
- Gastrointestinal obstruction
- Need for emergency surgery
- Previous esophageal surgery
- Lack of coordination of swallowing or respiration
- Esophageal cancer
- Hiatal hernia
- Increased intra-abdominal pressure
The decision to use a supraglottic airway, such as a laryngeal mask airway, is a judgement call based partially on perceived aspiration risk.
Provider Experience Affects Risk of Pulmonary Aspiration
At least one study found that provider factors such as improper decision making (75%), lack of experience (53.5) and lack of knowledge (21.4) were responsible for the majority of intraoperative aspiration events. Factors minimizing incidence, were vigilance (85.7%), having an experienced assistant (50%) and experience in that situation (25%).
Always be ready for vomiting and pulmonary aspiration. This starts with prevention:
Elective patients should be fasted. The American Society of Anesthesiologists currently recommends the “2-4-6-8” rule of fasting to minimize the risk of vomiting and aspiration.
- 8 hours for fatty foods and meat,
- 6 hours for light, non-fatty meal,
- 4 hours for breast milk,
- 2 hours for clear liquids, including water, pulp free juice, tea or coffee without milk.
Preop Nausea Prophylaxis
Consider adding preoperative medication prophylaxis to higher risk patients. Three common medication choices include Cimetadine, Metoclopramide (Reglan) and Ondansetron (Zofran). Cimetadine is an H2 blocker and decreases gastric pH. Metoclopramide facilitates gastric emptying by enhancing peristalsis of both the esophagus and stomach. Ondansetron is a potent anti-emetic that blocks the action of serotonin at the 5-HT3 receptor. Be aware of side effects and contraindications of any medications given.
Does Cricoid Pressure Prevent Pulmonary Aspiration?
Application of cricoid pressure (the Sellick Maneuver) is a common practice. It is a component of rapid sequence induction (R.S.I) — a widely used technique to minimize risk of aspiration in anesthesia in the presence of a full stomach. R.S.I includes:
- Preoxygenation (maximizes safe apneic interval)
- Rapid administration of induction and paralytic agents which are not titrated to effect (avoid delay waiting for onset of paralysis)
- Cricoid pressure (originally described to prevent passive regurgitation but not currently recommended for all patients),
- Avoidance of bag and mask ventilation (avoid delay and minimize distention of the stomach with air)
- Transoral insertion of an endotracheal tube using direct or video laryngoscopy.
Current Recommendation for Cricoid Pressure in R.S.I.
The American Heart Association found that the average practitioner’s was unable to correctly perform cricoid pressure on mannequins. Accordingly, they removed it from in-hospital and out-of-hospital resuscitation algorithms. Many studies show cricoid pressure displaces the esophagus in 50% or more patients. It also can distort the airway if performed incorrectly.
Conclusive data on the efficacy of cricoid pressure as part of R.S.I does not currently exist. Aspiration is a rare event, and therefore therefore would require large numbers of cases with and without cricoid pressure in order to assess true efficacy. In addition, the technique of R.S.I varies, making direct comparisons in studies difficult. Based on the available literature, systematic review concluded that cricoid pressure is benign and should be used in R.S.I, but lowered or released if the pressure is creating difficulties securing the airway. The Difficult Airway Society and the Obstetric Anesthesia Society advocate its use.
Avoid use of elective cricoid pressure with cervical spine injury. Cricoid pressure should be released if there is difficulty with intubation. It should also be released if the patient starts to actively vomit, as increased esophageal pressure could potentially cause esophageal rupture.
Aspiration is still possible despite cricoid pressure. Effective cricoid pressure requires teamwork. For a discussion on how to perform effective cricoid pressure see:
General Anesthesia vs Sedation?
Some procedures can be managed with either a combination of sedation plus local/regional anesthesia or with general anesthesia. When there is a choice, it is tempting to keep the patient “awake” because an awake patient can protect their own airway in the event of emesis.
However, not all conscious sedations are equal. Some of the surgeons I work with will complain that sedation is inadequate if the patient still maintains a lid reflex. Clearly such a patient will not protect their airway very well. Any sedation case can become an uncontrolled general anesthetic at a moment’s notice. Always take the appropriate precautions for aspiration in anesthesia.
Watch For Repetitive Swallowing!
Repetitive swallowing is a very common sign of nausea and impending emesis. You will often see it in the OR and PACU before a patient vomits. If you’re preparing to transfer the patient to PACU, wait a moment. Prepare suction. When the patient stops repetitive swallowing, the risk of vomiting has likely passed. Leave the OR — and your suction — only after you assess the patient is safe to travel.
When Vomiting Occurs:
When vomiting or passive regurgitation occur, you should:
- Immediately alert your team to help you. Good communication and teamwork will be critical.
- Turn the patient on the side, if possible.
- Quickly suction the pharynx.
- Place the bed in Trendelenburg, if possible, to allow emesis to pool away from the larynx.
- Immediately suction the endotracheal tube/SGA, if any.
- Administer 100% oxygen.
- Verify breath sounds.
- Deepen the anesthetic if appropriate to the progress of the case. Emesis can occur with light anesthesia.
- Treat bronchospasm with bronchodilators. Resistant bronchospasm may also respond to deepening the inhalational agent.
- Consider bronchoscopy, if available.
- If in a free-standing surgery center, consider early transfer to a hospital for serious symptoms.
- Consider immediate intubation, depending on how far the case has progressed and the risk of repeat emesis.
Many of these steps can be done concurrently by the team.
Minor aspiration can be asymptomatic. Wheezing, unequal breath sounds, an acidic pH of tracheal secretions, or actual particulate matter in the endotracheal tube indicate a major aspiration. Treat major aspiration aggressively with bronchoscopy, tracheal toilet, and chest physiotherapy.
Thick particulate material can plug your endotracheal tube and therefore be difficult to suction. Whenever ventilation is difficult, you may need to consider replacing a plugged ETT with a clean one. Weigh the risks of further aspiration.
Extubation With Aspiration Risk
Take precautions when your patient has high risk for passive regurgitation, vomiting, and aspiration.
- Unless contraindicated by the surgery or medical condition, plan on extubating awake.
- Prepare suction and suction the airway well
- Consider use of a nasograstric tube to drain the stomach before wakeup
- Extubate after restoration of airway reflexes.
If the patient aspirates upon extubation, use your clinical judgment regarding reintubation. Extubated patients are better able to cough and deep breathe than intubated patients. On the other hand, applying positive inspiratory pressure or high concentrations of oxygen is much easier in the intubated patient. Let the patient’s status guide you.
For a previous posts on safe extubation practice see:
Should You Continue With Surgery?
If aspiration occurs, then the decision to proceed with surgery is at the surgeon’s and anesthesiologist’s discretion. Factors influencing the decision include:
- urgency of the operation,
- the patient’s oxygen saturation,
- pulmonary compliance,
- response to interventions such as bronchodilators and positive end-expiratory pressure.
What Not To Do With Aspiration
- Bronchial lavage: may flush aspirate further into the lungs.
- Prophylactic antibiotics: may increase the risk of developing ventilator acquired pneumonia.
- Prophylactic corticosteroids: increases mortality in critically ill patients.
Aspiration is a serious complication, with potentially life-threatening consequences. We can minimize the risk to our patients by assessing risk, being vigilant, using good judgment, preparing for the worst, and acting quickly
Preparing for emergencies requires the ability to visualize those emergencies, as well as the possible responses to them before they happen. My previous review articles discuss many of these emergencies/complications and how to avoid them. Check out:
May The Force Be With You
Christine E Whitten MD, author
Anyone Can Intubate: A Step-By-Step Guide
Pediatric Airway Management: A Step-By-Step Guide
Nason, KS: “Acute Intraoperative Pulmonary Aspiration”, Thorac Surg Clin. 2015 August; 25(3): 301–307. doi:10.1016/j.thorsurg.2015.04.011.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4517287/pdf/nihms684298.pdf