You have Chance, a 3-year-old Labrador anesthetized for porcupine quill removal. As you are proceeding with quill plucking, you notice a bit of brown fluid on his tongue. Further investigation reveals there is a slow trickle of brown fluid from his esophagus into his mouth. Great, you’re only 20 minutes in and now he’s regurgitating. What do you do?
First, what is regurgitation? For the purpose of our discussion, we are talking about the movement of contents from the stomach into the esophagus +/- oropharynx. This is often termed gastroesophageal reflux (GER). Let’s go through the anatomy and physiology, risk factors, protective factors, and clinical recommendations for GER during anesthesia.
Anatomy and Physiology
Food and liquid normally pass through the upper esophageal sphincter, esophagus, lower esophageal sphincter, into the stomach, through the pylorus, and into the duodenum, so three sphincters are involved: the upper and lower esophageal sphincters and the pyloric sphincter. Gastric and pancreatic fluid have a variety of enzymes designed to digest material. Material is moved along the gastrointestinal (GI) tract with peristaltic waves.
This can all be disrupted by anesthesia in several ways:
First, the body position changes, possibly several times.
Second, many drugs affect sphincter tone.
Finally, some drugs cause emesis, ileus, and similar events in the GI tract.
Gastroesophageal reflux is a passive process whereby contents exit the stomach into the esophagus. These contents can be acidic or basic. They cause damage to the lining of the esophagus, which can cause esophagitis and, in the worst case, esophageal strictures. This reflux can be “silent” when it does not appear in the oropharynx. In this case, it will not be recognized unless special equipment- such as a pH monitor- are put into the esophagus.
The incidence of GER is estimated to be between 24% and 47% in dogs, depending on type of procedure, and up to 33% in cats. The table below breaks down incidence by the research study conducted. As you can see, there is a lot of variability.
Many drugs have been shown to NOT affect the incidence: including glycopyrrolate, inhalant anesthetics, atropine, maropitant, and metoclopramide.
In contrast, morphine increases the incidence - from ~27% without morphine to ~50% if morphine is included in the protocol.
Pre-operative vomiting does not affect GER incidence but age (more likely in older dogs), body position, intra-abdominal surgery, prolonged fasting, anesthesia duration, and being a large dog all increase the risk of GER.
Finally, although some laboratory studies indicated that a small meal of canned food shortly before induction to anesthesia decreased GER, a clinical study in dogs undergoing orthopedic procedures documented an increased incidence of GER if a canned meal (½ daily resting energy requirements) was fed 3 hours before anesthesia compared with fasting patients for 18 hours.
There are a few pharmaceutical approaches you can use to try to decrease the occurrence of GER. High-dose metoclopramide (1 mg/kg IV bolus followed by 1 mg/kg/hr) produced a 54% reduction in the incidence of GER. Omeprazole (1mg/kg) PO 4 hours before anesthesia reduced GER almost 80% in one study. In another, S-omeprazole alone (1mg/kg IV 12 and 2 hours before anesthesia) did not reduce GER, but when combined with cisapride (1mg/kg IV given at the same times), reduced the incidence from 38% to 11%. Due to the varied protocols and perianesthetic management in these studies, it is difficult to make direct comparisons amongst them.
First, identify high-risk patients. These are patients who have a history of regurgitation, patients you are concerned about being able to protect their airway (e.g. laryngeal paralysis cases), and brachycephalic breeds. In high-risk patients, you may want to do a metoclopramide CRI or consider oral omeprazole.
Second, communicate with clients. An esophageal stricture is an extremely frustrating condition for owners to manage. The treatment is repeated balloon dilation of the esophagus to stretch the stricture; this typically means serial anesthetic events, tremendous discomfort and expense, and repeated hospitalizations. Luckily, although GER is relatively common, strictures are extremely uncommon, so much so that we don’t have good data on how often they occur. I have personally seen about 15 strictures in 20 years of anesthesia practice. Obviously, you can’t spend two minutes with every client talking about extremely rare complications, but maybe including it on your consent form or information for them to read may be worthwhile. If you do have a high-risk patient, certainly discuss the risks with the client.
Third, minimize the risk of GER. Minimize body position changes and keep anesthesia short. If I have a high risk patient, I use metoclopramide CRI 1mg/kg bolus and 1 mg/kg/hr.
Finally, if GER does occur, treat it. See the GER Critical Event Checklist above. Suctioning the fluid seems like a reasonable first step. However, when done alone, it does not get enough of the material, and the esophagus can still be damaged even if suction is applied. Instilling water into the esophagus helped in one study, but instilling bicarbonate was the most effective treatment.
If you see fluid, check the pH with a normal pH strip. If it is neutral, you don’t need to do anything. If it is acidic or alkaline, you need to deal with it. My approach is to lavage the heck out of the esophagus. Check the endotracheal tube to make sure the cuff is inflated and the tube secured. Then dangle the patient’s head off the edge of the table. I usually use a horse tube and pump and pump water until it runs clear. Another option would be a red rubber urinary catheter and a source of active suction.
Gastroesophageal reflux occurs commonly in anesthetized small animal veterinary patients and can result in rare, though potentially devastating sequelae such as esophagitis and esophageal strictures.
Identify high risk patients, communicate with clients, minimize the likelihood of GER occurring, and treat it aggressively if observed.
What questions do you have about GER under anesthesia?
Does your hospital have a policy for addressing GER during anesthesia?
Have you had a patient develop a esophageal stricture following anesthesia?