Abstract
Intravenous anesthesia is commonly used during endoscopy. This approach greatly improves patient satisfaction with pain control. The risks of anesthesia are usually focused on the cardiopulmonary effects of anesthetics. The risk of pulmonary aspiration is often overlooked, unless there are other risk factors that may increase the incidence of pulmonary aspiration. Here, we report a patient with unexpected aspiration pneumonia after gastroscopy under intravenous anesthesia. We suggest that pulmonary aspiration should be taken into consideration as a risk associated
with anesthesia for gastroscopy.
Keywords
anesthesia; conscious sedation; gastroscopy; pneumonia;
1. Introduction
Endoscopy is commonly used to detect diseases of the digestive tract. Because patients usually feel uncomfortable during the examination, sedatives are commonly used to reduce the painful sensations and unpleasant experiences during these procedures.
In particular, intravenous sedation has been introduced to reduce patient anxiety during endoscopy. Although sedation improves the quality of the procedure and the patient reports better satisfaction, there are some potential risks. In particular, the risks of anesthesia during endoscopy include cardiopulmonary effects1 and possible iatrogenic injuries, such as perforation of the alimentary canal. However, there are some complications that are often overlooked. This report describes an instance of aspiration pneumonia after gastroscopy.
2. Case Report
The patient was a 65-year-old man (height, 161 cm; weight, 65 kg; body mass index, 25.1 kg/m2) with a history of being a hepatitis C carrier for 20 years and who had coronary artery disease for 1 year. Apart from these diseases, his general condition was fine. There were no symptoms of upper respiratory infection before the examination. He was scheduled to undergo a series of routine physical examinations, which included gastroscopy and colorectoscopy; the patient had adequately fasted before the examinations (nil per os since 22:00 hours on the previous night). Fleet enema was performed twice the day before the examination at 13:00 and 21:00 hours, and comprised 45 mL of Fleet mixed with 360 mL of a residual-free drink.
The endoscopy started at 11:10 hours and finished at 11:30 hours. The patient was placed in the left-lateral decubitus position during the procedure. Oxygen was supplied via a face mask and assisted ventilation was not necessary. Before the gastroscopy, 5 mL of simethicone was given to eliminate excessive gastric gas bubbles and facilitate the insertion of the gastroscope. No other medications or local anesthetic were used. The patient received 75 μg fentanyl, 2 mg midazolam and 50 mg propofol before the gastroscopy. Ten minutes later, the gastroscopywas completed, and 20 mg propofol was given before starting the colorectoscopy. The patient was completely unconscious and immobile during the procedure, and no lavage was used.
On completion of the gastroscopy, gastric juice was removed by suction. The entire procedure was done smoothly and lasted for about 20 minutes. There was no agitation, choking, coughing or vomiting.
After the procedure, he was placed in a recovery room for 1 hour. However, the patient felt mild dyspnea and chilliness, and fever set in a few hours later. Therefore, he was sent to our emergency department for further examination. A chest X-ray showed diffuse infiltration over the upper and lower lobes of the left lung. He was admitted for further treatment under the impression of acute pneumonia of unknown cause. During hospitalization, the patient received antibiotic treatment with fluoroquinolone. A computed tomography scan of the chest was performed the next day and showed groundglass opacity and consolidation in the left upper and lower lung. Based on these imaging findings, aspiration pneumonia was highly suspected. A series of X-ray findings are shown in Figure 1. The pneumonia was under control and the fever subsided gradually. Echocardiography was also performed to rule out congestive heart failure with cardiogenic pulmonary edema. Blood and sputum cultures revealed negative findings. After 10 days of medical treatment, the pneumonia subsided and he was discharged in a stable condition.
In terms of the possible causes of the pneumonia, there was no solid evidence for a specific pathogenesis, although aspiration was considered the most likely cause, based on the rapid onset, the absence of previous upper respiratory infection, and X-ray findings.
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3. Discussion
Applying intravenous anesthesia for endoscopy is usually considered safe and is a service done for the patient’s satisfaction. Most patients are willing to undergo endoscopy under sedation.2 Adequate sedation may also help the examination to progress more smoothly. Thus, sedation is now widely used in endoscopy. Although it is considered safe under appropriate monitoring, it still carries some risks.
The risks mostly involve cardiopulmonary complications such as hypoxia and changes in electrocardiography or blood pressure. The risks of pulmonary aspiration are usually overlooked, unless the patient has a history of gastrointestinal diseases such as gastroesophageal reflux disease,3 upper gastrointestinal bleeding,4 intestinal obstruction, and inadequate fasting time.5 Indeed, aspiration pneumonia is seldom observed in healthy patients undergoing regular endoscopy. In our case, there were no underlying factors that would have increased the risks of pulmonary aspiration. The precise time at which the aspiration occurred is unknown and it may have occurred either during or after the procedure.
Nevertheless, we believe that the pulmonary aspiration occurred during the procedure because the patient only showed left-sided pneumonia and he was placed in the left-lateral decubitus position during gastroscopy. In contrast, common aspiration pneumonia is usually found in the right lung. To our surprise, the procedure was performed smoothly and coughing, choking and vomiting were not noted during or after the procedure. However, it is possible that the protective reflexes were impaired by the sedation, meaning that these symptoms were not observed.6
Conscious sedation is usually recommended in endoscopy.7 However, the choice and doses of analgesic agents vary greatly among anesthesiologists, usually depending on the patient’s response. Lower doses of anesthetics may preserve more active protective reflexes and have less effect on cardiopulmonary function, but the patient may not be placid and agitation may interrupt the procedure.
A deeper sedation level is usually considered safe, unless the patient has underlying diseases that may increase the risk of aspiration. However, aspiration pneumonia still occurred in our patient.
Overall, the anesthesiologist should consider that the volume of air and water injected into the stomach during gastroscopy may be large, and suction through the endoscope may not be adequate to prevent aspiration. The experience of the examiner may also influence the risks of aspiration. The lower and upper esophageal sphincters prevent passive regurgitation from the stomach to the esophagus and from the esophagus to the pharynx, respectively, when they are working optimally. However, their tone is reduced as consciousness is depressed.
Furthermore, the tone of the esophageal sphincter may be influenced by the drugs administered by the anesthesiologist.8,9 These factors may account for the pulmonary aspiration in this patient.
Pulmonary aspiration can be classified into two distinct clinical entities, aspiration pneumonitis and aspiration pneumonia.10 The former is a chemical injury caused by the inhalation of sterile gastric contents. It usually occurs in patients with severely impaired consciousness resulting from drug overdose, seizures, massive cerebrovascular accident, or anesthesia. Meanwhile, aspiration pneumonia is an infectious process that develops after the inhalation of oropharyngeal material colonized by pathogenic bacteria. The clinical presentation and symptoms also vary. The differences between aspiration pneumonitis and aspiration pneumonia are summarized in Table 1. In this case, because of the suppressed consciousness, the symptoms developed rapidly, within a few hours, with negative culture findings. Thus, aspiration pneumonitis seems more likely in this patient.
Since unexpected aspiration may occur in patients without obvious risk factors for pulmonary aspiration, we should endeavor to prevent it from
occurring and minimize the damage it causes should it occur. The patient described here was placed in the left-lateral decubitus position. Some authors have reported that some body positions, including sitting and the semi-recumbent position, could reduce the incidence of aspiration.11−14 Placing patients in the head-up position is also simple. Thus, we suggest that tilting the head up should be routinely
considered during gastroscopy. Meanwhile, reducing gastric acidity may help avoid severe injury resulting from massive aspiration15 and can be achieved by administering proton pump inhibitors (PPI) or histamine receptor-2 (H2) antagonists before the procedure. These medications can effectively increase the gastric pH and decrease the volume of gastric juice if administered sufficiently early before endoscopy.16−19 As found in previous studies, extremely low acidity and large amount of gastric aspirates are associated with higher morbidity and mortality rates.20,21 It is generally considered that a pH of less than 2.5 and a volume of gastric aspirates greater than 0.3 mL/kg body weight (20−25 mL in adults) may lead to aspiration pneumonitis. 20,22−24 Prescription of either H2 antagonists or PPIs can prevent severe morbidity or mortality if aspiration does occur. Although routine prescription of these drugs is not currently recommended in the American Society of Anesthesiologists guidelines, and the incidence of pulmonary aspiration is very low, it can be lethal in some patients. A single dose of these drugs is relatively inexpensive and may avoid medical malpractice lawsuits in the event of severe aspiration pneumonia. We suggest that, in the future, the prescription of H2 antagonists or PPIs be considered as preventive therapy before endoscopy, particularly if the procedure is performed under sedation.
In conclusion, this case reminds us that, even in a healthy patient, endoscopy under sedation carries the risk of pulmonary aspiration. Therefore, we should be aware of unexpected aspiration pneumonia and should be particularly cautious when performing endoscopy in combination with anesthetic agents. Tilting the head upwards and the prescription of PPIs or H2 antagonists may prevent severe aspiration. The risk of aspiration should be included in the preoperative evaluation and should be explained to the patient as a possible risk of the procedure.