SMALL ANIMAL MEDICINE
Gastro-eosophageal Reflux and Regurgitation in
Anaesthetised Dogs
Liesel van der Merwe BVSc MMedVet(Med) Small Animals
Oesophagitis oesophageal strictures and aspiration pneumonia are potential consequences of peri-anaesthetic
vomiting, regurgitation and gastro-oesophageal reflux (GER). A lot has been published recently on what could be
risk factors for GER. Various studies have reported rates of regurgitation in anaesthetised dogs from 0.42 – 5.5%.
Regurgitation is defined as the passive discharge of gastric or oesophageal fluid from the mouth or nose. GER in
anaesthetised dogs is a more common but less visible complication than regurgitation and is detected in 16 – 55% of
anaesthetised dogs.
GER occurs when the lower oesophageal sphincter (LES) tone is decreased due to the administration of anaesthetic
agents, gastric acidity and withholding food prior to anaesthesia. Gastric contents will enter the oesophagus but
not reach the pharynx. Monitoring of lower oesophageal pH has a high degree of sensitivity for detecting GER and
is considered the gold standard. Reflux of gastric contents into the oesophagus is recorded when oesophageal pH
decreases to <4 (acidic reflux) or increases above 7.5 (biliary reflux). Bile acids and gastric acids can work synergistically
to cause greater inflammatory injury to the mucousa than either alone.
GER can be clinically silent and is only clinically detected as fluid reaches the oronasal cavity. Once oesophageal
contents reach the pharynx and mouth it is termed regurgitation. Aspiration of the gastric material into the lungs may
cause pneumonitis or or it may cause local oesophageal irritation and oesophagitis.
GER during anaesthesia is associated with 46 – 65% of cases of benign oesophageal stricture secondary to oesophagitis
in dogs. Approximately 25% of dogs which have GER under anaesthesia have evidence of refluxed gastric content
in the pharynx, increasing the risk of aspiration pneumonia. Prolonged exposure (>1-2 hours) of the oesophageal
mucousa to acid (pH <4) is an important cause of oesophagitis. Oesophageal acid clearance does not occur under
anaesthesia or during sleep.
Practical risk management - endotracheal entubation with inflated cuff until the animal regains full consciousness and
laryngeal function. References available online www.vet360.vetlink.co.za
Table 1 – Medications and factors affecting GER
INCREASED REFLUX (GER) DECREASED REFLUX (GER)
Morphine, ACP, Atropine , Xylazine, IM meperidine (dogs, not cats)
Isoflourane (>> than halothane) IV Maropitant 45 – 60 min prior (no vomiting with premed but still GER in 30% of
dogs compared to 46% of control dogs )
50% of dogs receiving propofol had GER Feed a small meal 3- hours prior to GA (reduced fasting time)
(Savvas et al JAAHA, 2016)
Brachycephalic breed disposition due to increased negative intra-tho-
racic pressures (shown in some reports and not in others) Maropitant did not prevent the occurrence of gastro-oesophgageal reflux (GER)
although fewer dogs in the treated group did show GER.
Prolonged food withholding (18 hrs) 17,4% of dogs receving thiopentone had GER.
Metoclopramide (0.4mg/kg bolus with 0.3mg/kg CRI failed to reduce
GER) Metoclopramide 1mg/kg bolus IV and 1mg/kg CRI resulted in a 54% reduction in
the risk of GER
Increased duration of surgery Diazepam premed
Changes in body position during anaesthesia. GER is also more likely
in dogs in sternal recumbency Cisapride significantly decreased the frequency of GER (11% vs 36% in
omeprazole and placebo group)
Intra-abdominal surgery.
Orthopaedic surgery - often involves pre and post- operative imaging
under the same anaesthesia and changes in the dogs position and
transfer between areas may result in changes in abdominal and gastric
pressures.
Light meal 3 hour pre-GA ( Viskjer et al AJVR)
Patients > 40kg (larger breed size more than obesity)
Omeprazole/esomeprazole – no effect on number of reflux events.
But percentage time pH < 4 was significantly decreased
*Some drugs and factors are clearly implicated whereas other factors are multivariate – example NSAIDs are implicated - but these are
given in dogs for orthopaedic surgery which also generally receive morphine - so there is no direct cause and effect.
vet360
Issue 05 | NOVEMBER 2018 | 22