25/02/2026
Protecting against reflux and regurgitation during anaesthesia.
Definition & Incidence:
Reflux is the movement of gastric contents into the oesophagus. It can consist of either:
• acid reflux pH 7.5
Reflux can cause postoperative pain and oesophageal stricture formation (Epstein and Swirsky 2009). There is a reported incidence of up to 67% (Raptopoulos and Galatos, 2008), (Wilson 2006), and 33% in one study in cats – (Garcia et al, 2017).
Regurgitation is the end stage, dangerous & extreme manifestation of reflux, consisting of material flowing into the pharynx and sometimes exiting the mouth or nose. It has a reported incidence of up to 48% (Raptopoulos and Galatos, 1997). Regurgitation can cause dangerous clinical issues such as laryngospasm and aspiration pneumonia.
Mechanics:
There are two oesophageal sphincters in mammals – the upper oesophageal (esophageal) sphincter (UES) and the lower oesophageal (esophageal) sphincter (LES). Neither are isolated anatomical structures but consist of the contribution of a range of structures to resisting the cranial flow of gastric contents.
The UES consists mainly of the cricopharyngeus muscle and pharyngeal constrictor muscle. These muscles clamp around the dorsal aspect of the larynx, compressing the proximal oesophagus. The strength of this seal does depend to an extent on head position. A hyper-extended head (commonly observed if the patient’s head is unsupported during anaesthesia) reduces the strength of the UES and increases the risk of regurgitation.
The LES consists of several structures:
The oblique dorso-ventral direction of the oesophagus as it enters the stomach creates a flap valve like constructed of smooth muscle and has considerable resting muscle tone. This helps to keep the gastro-oesophageal junction closed, especially as the stomach fills.
A circumferential arrangement of muscle fibres is present at the gastro-oesophageal junction.
The soft ridges of gastric and oesophageal mucosa at the gastro-oesophageal junction contribute to the LES.
The diaphragm muscles constrict the oesophagus as it passes from the thorax into the abdomen. The right diaphragmatic crus is longer and stronger than the left crus, contributing disproportionately to the LES. Patients in right lateral recumbency are more likely to reflux than those in left lateral recumbency. Heavy dogs placed in sternal recumbency on a flat surface will experience thoracic and diaphragmatic distortion which also increases the risk of reflux. Heavy dogs placed in sternal recumbency should be supported with conforming foam or bean bag supports to reduce this risk.
A variable amount (depending on species and breed) of the oesophagus lies within the abdomen before it joins the stomach. The intra-abdominal pressure acts more strongly on the narrow diameter oesophagus than it does on the wider diameter stomach, exerting more pressure on the oesophagus than on the stomach. This makes it harder for gastric contents to enter the oesophagus. Animals with a longer abdominal oesophagus (e.g. rats) are more resistant to reflux and regurgitation. Greyhounds and Beagles have been found to have a very short abdominal oesophagus compared to other dog breeds.
Risk Factors
Various risk factors increase the likelihood of a reflux or regurgitation effect:
• Right lateral or ventral recumbency, especially if unsupported
• Movement (changing rooms) at a light plane of anaesthesia
• Increased intra-abdominal pressure
• Increased intra-thoracic pressure (IPPV)
• Obesity (probably as a result of increased body mass creating diaphragmatic distortion)
• Over-starving patients
Best practice for many years was to starve dog and cat patients overnight. Studies now show that starving for too long an increase the production of gastric fluid. Recommendations vary but 5 hours is now frequently discussed. Some studies recommend a low fat meal 3 hours prior to anaesthesia (Savas et. al. 2009). Gastric volume is more indicative of risk than starvation time. (Cichocki, 2008). Paediatric patients should not be fasted for more than four hours.
Reflux events are more likely to happen if patients are moved at a light plane of anaesthesia. (Bradbrook 2011) Recumbent patients should be supported to minimise thoracic distortion. If possible, the patient’s head should be slightly raised.
Airway management:
A high volume, low pressure cuffed endotracheal tube is only moderately effective at holding back regurgitated material from the trachea. Positioning the cuff in the proximal trachea will reduce the amount of tracheal mucosa exposed to regurgitated material but this requires the tube to be cut to size for each patient to avoid excessive dead space.
Unlike an endotracheal tube, which has no upper glottis barrier, the v-gel® supraglottic airway devices have various features which reduce the risk of reflux turning into regurgitation Supraglottic airway devices form a seal around the larynx on the floor of the pharynx. On the cat and rabbit devices, the tip of the device sits in the oesophagus, terminating in an ‘oesophageal plug’ which makes it harder for reflux fluid to enter the pharynx.
On the dog v-gel®, this oesophageal plug contains a gastric channel running through the device, exiting by the circuit adapter. Including a gastric channel in the device means that it is easier to identify when a serious reflux/regurgitation event has occurred. It also isolates the upper airway and channels regurgitated fluid away from the airway and allows the anaesthetist to drain oesophageal or gastric material during an anaesthetic procedure.
Supraglottic airway devices do not touch the arytenoid cartilages of the larynx and are much softer than endotracheal tubes. In the majority of cases, they can be left in place for longer than an endotracheal tube during anaesthetic recovery. This allows additional protection against regurgitation in this critical period.
If a reflux or regurgitation event is seen, or suspected in the dog, consider the following points:
Pass a flexible catheter/drain tube through the gastric channel of a supraglottic airway device. Drain remaining reflux fluid from the oesophagus, passively/with syringe/ with suction unit.
Lavage the oesophagus; areas where regurgitated or refluxed material has sat should be gently washed ideally using sterile isotonic saline. Merely draining material will not give optimal protection against acid damage. (Bradbrook, 2011)
Medication can be administered directly onto the oesophagus via a clean gastric tube.
Regurgitation can lead to postoperative laryngospasm and aspiration pneumonia. Close monitoring in the postoperative period is mandatory. Thoracic radiographs are a sensible precaution if aspiration is suspected.
In summary:
• Reflux and regurgitation are common complications in dog and cat anaesthetics.
• Clinical sequelae include oesophagitis, postoperative pain, oesophageal strictures, laryngospasm and aspiration pneumonia.
• Ventral and right lateral recumbency positions can increase the risk of reflux, especially in large dogs. Supporting the thorax to minimise thoracic distortion is vital.
• Reflux and regurgitation is more likely in situations where thoracic or abdominal pressures are increased.
• Sudden unexpected changes in respiratory pattern during anaesthesia may be a marker of reflux
• If a reflux or regurgitation event occurs, ensure that material is removed and flush the mucosa with sterile isotonic saline wherever possible. Ensure that all pharyngeal and oesophageal liquid is removed to reduce the risk of aspiration during anaesthetic recovery.
• Clinical signs of reflux or regurgitation in the postoperative period may include hypersalivation, swallowing, neck stretching, or pain when swallowing.
References and reading:
1. Benign esophageal stricture in the dog and cat: a retrospective study of 20 cases. Adamama-Moraitou KK, Rallis TS, Prassinos NN, Galatos AD; Can J Vet Res, 2000 Jan: 66(1) 55-59
2. Bracker, K, Peri-anesthetic Gastroesophageal Reflux and Regurgitation. mspca.org/angell_services/peri-anesthetic-gastroesophageal-reflux-and-regurgitation
3. Bradbrook C, Gastro-oesophageal reflux: Risk Factors and Treatment.
vettimes.co.uk/app/uploads/wp-post-to-pdf-enhanced-cache/1/gastro-oesophageal-reflux-risk-factors-and-treatment.pdf
4. Effect of pre-anaesthetic fasting time on Gastroesophageal reflux and stomach size. Brandy Cichocki, 2008.
5. Favarato ES, Souza MV, Costa PRS Evaluation of metoclopramide and ranitidine on the prevention of gastroesophageal reflux episodes in anesthetised dogs. Res Vet Sci 2011:91 (3) e25-e27
6. Prevalence of Gastroesophageal Reflux in Cats During Anesthesia and Effect of Omeprazole on Gastric pH: Garcia RS, Belafsky PC, Della Maggiore A, Osborn JM, Pypendop BH, Pierce T, Walker VJ, Fulton A and Marks SL, J Vet Intern Med, 2017 May-Jun 21(3): 734-742
7. Epstein A and Swirsky N; Post-anesthetic esophageal dysfunction in a dog, Israel Journal of Veterinary Medicine Vol 64 (1) 2009
8. Galatos AD, Raptopoulos D, Gastrooesophageal reflux during anaesthesia in the dog: the effect of preoperative fasting and premedication. 1993, The Veterinary Record 137 (19): 479-83
9. Feline lower esophageal sphincter sling and circular muscles have different functional inhibitory neuronal responses; L’Heureux MC, Muinuddin A, Gaisano HY, Diamant NE, Am J Physiol Gastrointest Liver Physiol, 2006 Jan: 290 (1)
10. Effects of preanesthetic administration of morphine on gastroesophageal reflux and regurgitation during anesthesia in dogs. Wilson DV, Evans T, Miller MS; American Journal of Veterinary Research 2005, Vol 66, No 3, 386-390
11. Influence of halothane, isoflurane and sevoflurane on gastroesophageal reflux during anesthesia in dogs. Wilson DV, Boruta DT, Evans AT. Am J Vet Res 2006, 67 (11) 1821-5
12. Wilson DV, Evans A, Maurer WA, Influence of metoclopramide on gastroesophageal reflux in anesthetized dogs. Am J Vet Res 2006; 67 (1) 26-31
13. The effect of omeprazole on oesophageal pH in dogs during anaesthesia. Panti A, Bennett RC, Coreltto F, Brearley J, Jeffery N, Mellanby RJ, J Small Animal Pract. 2009 Oct 50 (10) 540-4
14. Raptopoulos D, Galatos AD, Gastro-oesophageal reflux during anaesthesia induced with either thiopentone or propofol in the dog. Veterinary Anaes Analg 1997 Vol 24, 1, p20-22
15. Gastroesophageal reflux in anesthetized dogs: a review. Rodriguez-Alarcon CA, Beristain-Ruiz DM, Rivera-Barreno R, Guadalupe D, Uson-Casaus JM, Garcia-Herrera R, Perez-Merino EM. Revista Colombiana de Ciencias Pecuarias Ver Colom Cienc Pecua vol 29, no 2 Medellin April/June 2015
16. Savas I, Rallis T, Raptopoulos D. The effect of pre-anaesthetic fasting time and type of food on gastric content volume and acidity in dogs, 2009, Vet Anaesth Analg 36: 539-546.
