Esophageal reflux and regurgitation during anesthesia represent significant concerns when providing care for canine patients. These complications can lead to serious consequences including aspiration pneumonia, esophagitis, esophageal strictures, and potentially life-threatening outcomes if not properly managed.
The physiology behind reflux during anesthesia involves several key mechanisms. Under normal circumstances, the lower esophageal sphincter (LES) serves as the primary barrier against reflux, maintaining tonic contraction to prevent gastric contents from entering the esophagus. Additional protection comes from the diaphragmatic crura, which provide mechanical support, while esophageal peristalsis works to clear any refluxed material. However, during anesthesia, these protective mechanisms become significantly compromised. Most anesthetic agents, particularly inhalants, opioids and alpha2 agonists, can reduce LES tone by up to 90%. Positive pressure ventilation alters the pressure gradient between thorax and abdomen, while certain patient positions—especially dorsal recumbency and Trendelenburg positions—increase intragastric pressure. The absence of protective reflexes such as coughing and swallowing during anesthesia further limits the clearance of refluxed material, and delayed gastric emptying associated with preanesthetic medications compounds these risks.
Several patient-specific factors increase the risk of reflux during anesthesia. Dogs with pre-existing gastrointestinal disorders, brachycephalic breeds with inherent upper airway abnormalities, obese patients, geriatric dogs with decreased esophageal motility, and those with a history of previous regurgitation events are all at higher risk. Anatomical abnormalities such as hiatal hernia and emergency procedures with inadequate fasting periods also significantly increase risk. Notably, the use of certain medications poses additional concerns. Opioids, particularly full μ-agonists like morphine and hydromorphone, can decrease gastric motility, increase pyloric tone, and delay gastric emptying, all of which predispose patients to reflux. Alpha-2 adrenergic agonists such as dexmedetomidine and medetomidine significantly reduce gastric motility and can cause relaxation of the LES, substantially increasing reflux risk, especially when combined with other anesthetic agents.
Procedure-related factors further contribute to reflux risk. The duration of anesthesia correlates directly with increased risk, as do abdominal procedures involving manipulation of viscera. Certain patient positions, endotracheal tube placement issues, and the use of neuromuscular blocking agents all factor into potential complications. Inadequate anesthetic depth, with periods of light anesthesia, can trigger reflex swallowing and increase the likelihood of regurgitation.
Prevention strategies should be implemented for all canine anesthesia cases, with additional precautions for high-risk patients. Preoperatively, appropriate fasting protocols should be followed: 8-12 hours for adult dogs with shorter intervals of 4-6 hours for pediatric, geriatric, or compromised patients. Administration of gastric protectants and prokinetics before anesthesia can reduce risk, as can avoiding unnecessary delays between premedication and induction. When selecting an anesthetic protocol, consider agents with less effect on LES tone when possible. Metoclopramide (0.2-0.5 mg/kg IV) administered 30 minutes before induction can increase LES tone and promote gastric emptying, while cisapride (0.1-0.5 mg/kg PO) given 2-3 hours preoperatively may improve gastric emptying.
Intraoperative management should focus on maintaining appropriate anesthetic depth to avoid excessive depths that further relax the LES. Ensuring proper endotracheal tube placement with appropriate cuff inflation creates a barrier against aspiration if reflux occurs. Whenever clinically feasible, position patients with the head elevated 10-30 degrees and avoid excessive abdominal pressure during positioning or surgery. Vigilant monitoring for signs of reflux, such as regurgitation around the endotracheal tube or gastric fluid in the oropharynx, allows for early intervention.
When reflux occurs during anesthesia, prompt intervention becomes essential. Immediate management includes elevating the patient’s head and thorax while thoroughly suctioning the pharynx to remove refluxed material. Protection of the airway by ensuring proper endotracheal tube cuff inflation is critical. Esophageal lavage represents an important treatment step when significant reflux has occurred. This procedure involves gently introducing a soft, flexible tube into the esophagus and slowly instilling warm saline or water (10-20 ml/kg divided into multiple aliquots) to dilute and flush away acidic gastric contents. The fluid should be immediately removed via gentle suction to prevent further contamination. This lavage procedure may need to be repeated several times until the returned fluid is clear, indicating removal of the caustic material.
Pharmacological interventions following reflux include administration of H2-receptor antagonists such as famotidine (0.5-1.0 mg/kg IV), proton pump inhibitors for severe cases, and sucralfate for esophageal mucosal protection. Metoclopramide may be used for motility enhancement. Postoperatively, continued head elevation for 2-4 hours, maintenance of NPO status for at least 4-6 hours following reflux events, and careful monitoring for signs of aspiration pneumonia are essential. Implementation of broad-spectrum antibiotic therapy should be considered if aspiration is suspected, and gastric protectants should be continued for 5-7 days following reflux episodes.
Clinical monitoring for aspiration following reflux events must be vigilant, including regular thoracic auscultation, temperature monitoring, respiratory assessment, pulse oximetry, and thoracic radiographs if indicated. Brachycephalic breeds require additional precautions, including more aggressive prophylactic medication protocols, maintained head elevation throughout anesthesia, rapid sequence induction techniques, and extended post-anesthetic monitoring periods.
Esophageal reflux during anesthesia in dogs represents a preventable complication with potentially serious consequences. Understanding the underlying physiology and risk factors allows for implementation of effective preventive strategies. When reflux does occur, prompt recognition—followed by appropriate intervention including careful esophageal lavage—minimizes the risk of long-term complications. Individualized anesthetic protocols that account for the additional risks posed by opioids and alpha-2 agonists, combined with vigilant monitoring, significantly reduce the incidence and impact of this common anesthetic complication.
