Ambulatory esophageal pHmetry in healthy dogs with and without the influence of general anesthesia

Esophageal pH-monitoring in nonbrachycephalic dogs; a reference

OBJECTIVE

To establish parameters that describe acidic gastroesophageal reflux (GER) events in nonbrachycephalic, hospitalized dogs without gastrointestinal disease following short total intravenous anesthesia, to establish upper reference limits for parameters that describe GER.

STUDY DESIGN

Clinical prospective study.

ANIMALS

Healthy, client-owned dogs presenting for elective orthopedic surgery.

METHODS

Dogs were sedated with IM methadone (0.2 mg/kg) and medetomidine (5 ug/kg), followed by alfaxalone total intravenous anesthesia. The Digitrapper esophageal dual pH monitoring probe was placed transnasally into the esophagus. Dogs were unsedated during the subsequent recording period. A GER event was defined as esophageal pH less than 4.0. Parameters that described GER were: (1) number of GER events per hour, and (2) cumulative esophageal acid exposure (percentage of recording duration) at each sensor. Upper reference limits were calculated for each parameter.

RESULTS

Thirty-five dogs were included (median age 7 years, range 1-12). The median recording duration was 21.1 h (range 13.6-29.3). Productive regurgitation was not noted in any dog. The median number of distal and proximal GER events per hour was 0.3 (range 0-4.3) and 0 (range 0-1), respectively. The median cumulative distal and proximal esophageal acid exposure was 0.2% (range 0.3-9%) and 0% (range 0%-1%), respectively.

CONCLUSION

Upper reference limits for distal and proximal GER per hour was 2.4 and 0.4, respectively, and, for cumulative distal and proximal esophageal acid exposure, 2.3% and 0%, respectively.

CLINICAL SIGNIFICANCE

Dogs undergoing esophageal pH monitoring in a similar hospital setting with parameters above these upper reference limits have excessive GER.

Effect of the reverse Trendelenburg position on the incidence of gastroesophageal reflux in dogs anesthetized for elective stifle surgery

OBJECTIVE

To determine if a 15° reverse Trendelenburg position decreases the incidence of gastroesophageal reflux (GER) compared with a horizontal position in dogs anesthetized for stifle surgery.

STUDY DESIGN

Prospective, randomized parallel-arm study.

ANIMALS

A total of 44 healthy client-owned dogs were enrolled and data from 36 dogs were analyzed.

METHODS

Dogs requiring preoperative radiographs under anesthesia, or with a history of gastrointestinal signs or administered gastroprotectant therapy within 1 month of surgery were excluded. Anesthesia protocol was standardized to include hydromorphone, dexmedetomidine, ketamine, propofol and isoflurane. Dogs were randomly assigned at enrollment to be positioned in a 15° reverse Trendelenburg or a horizontal position for surgery. Continuous pH monitoring was documented throughout the procedure with a 6.4 Fr (2.13 mm) esophageal pH probe positioned in the distal esophagus via the oral cavity. GER was defined as pH < 4.0 (acidic) or > 7.5 (alkaline) for more than 30 seconds. The proportions of dogs developing GER were compared between groups using Fisher's exact test. Time to reflux was compared using survival curves and the Gehan-Breslow-Wilcoxon test. Statistical significance was set as p < 0.05.

RESULTS

An episode of GER occurred in 11/36 (30%) dogs. Reflux was alkaline in two dogs and acidic in nine dogs. The proportion of dogs with GER was 5/18 (28%) and 6/18 (33%) for dogs in the reverse Trendelenburg position and horizontal position, respectively, and was not statistically significant (p > 0.99). Median (range) time until reflux was 44 (23-135) and 44.5 (9-56) minutes when dogs were positioned in reverse Trendelenburg position and horizontal position, respectively (p = 0.66; two-tailed Mann-Whitney U test).

CONCLUSIONS AND CLINICAL RELEVANCE

Positioning the surgery table in a 15° rostral elevation for dogs anesthetized for elective stifle surgical procedures did not decrease the incidence of GER.

The Effect of Premedication on the Incidence of Gastroesophageal Reflux in 270 Dogs Undergoing General Anesthesia

The aim of this prospective, non-randomized study was to evaluate the effect of nine different premedication medications on the incidence of gastroesophageal reflux (GOR) in anesthetized dogs. Two hundred and seventy dogs undergoing non-intrathoracic, non-intrabdominal elective surgeries or invasive diagnostic procedures were included in the study, and were allocated into nine groups (30 dogs/group) defined by the type of premedication administered. Premedication consisted of dexmedetomidine with either morphine, pethidine or butorphanol, acepromazine with either one of the three opioids or midazolam with one of the above-mentioned opioids. Anesthesia was induced with propofol and maintained with isoflurane in oxygen. Esophageal pH was measured with the use of a pH-meter electrode and a pH-value less than 4 and over 7.5 was considered to be GOR. The study revealed that 119/270 (44.1%) dogs experienced a reflux episode during anesthesia. The incidence of reflux did not differ among groups (p = 0.117). In group AB the dogs refluxed within 10 min of the beginning of pH-measurements, in comparison with group DB in which dogs refluxed within 30 min (p = 0.029). Invasive diagnostic procedures had a lower incidence of GOR in comparison to castrations (p = 0.09). The outcome of the study suggests that none of the opioids used increased the incidence of GOR in anesthetized dogs.

Gastrointestinal transit time is faster in Beagle dogs compared to cats

OBJECTIVE

To characterize gastrointestinal transit times (GITTs) and pH in dogs, and to compare to data recently described for cats.

ANIMALS

7 healthy, colony-housed Beagles.

PROCEDURES

The GITTs and pH were measured using a continuous pH monitoring system. For the first period (prefeeding), food was withheld for 20 hours followed by pH capsule administration. Five hours after capsule administration, dogs were offered 75% of their historical daily caloric intake for 1 hour. For the second period (postfeeding), food was withheld for 24 hours. Dogs were allowed 1 hour to eat, followed by capsule administration. Both periods were repeated 3 times. The GITTs and pH were compared to published feline data.

RESULTS

The mean ± SD transit times in dogs for the pre- and postfeeding periods, respectively, were esophageal, 3 ± 5 minutes and 13 ± 37 minutes; gastric, 31 ± 60 minutes and 829 ± 249 minutes; and intestinal, 795 ± 444 minutes and 830 ± 368 minutes. The mean ± SD gastrointestinal pH in dogs for the pre- and postfeeding periods, respectively, were esophageal, 6.6 ± 0.6 and 5.7 ± 1.0; gastric, 3.0 ± 1.4 and 1.8 ± 0.3; intestinal, 7.9 ± 0.3 and 7.7 ± 0.6; first-hour small intestinal, 7.6 ± 0.5 and 7.1 ± 0.4; and last-hour large intestinal, 7.9 ± 0.6 and 7.7 ± 1.0. The first-hour small intestinal pH and total transit times varied between dogs and cats depending on feed period (P = .002 and P = .04, respectively). Post hoc analysis revealed significantly shorter total transit times in dogs prefeeding (P = .005; mean ± SD for cats, 2,441 ± 1,359 minutes; for dogs, 828 ± 439 minutes) and postfeeding (P = .03; mean ± SD for cats, 3,009 ± 1,220 minutes; for dogs, 1,671 ± 513 minutes). Total transit time for dogs was also shorter pre- versus postfeeding (P = .003).

CLINICAL RELEVANCE

GITT is faster in Beagles compared to cats, but gastrointestinal pH are similar when fed the same diet.

A Comparative Assessment of the Diagnosis of Swallowing Impairment and Gastroesophageal Reflux in Canines and Humans

Swallowing impairment is a highly prevalent and clinically significant problem affecting people and dogs. There are myriad causes of swallowing impairment of which gastroesophageal reflux is the most common in both species. Similarities in anatomy and physiology between humans and canines results in analogous swallowing disorders including cricopharyngeus muscle achalasia, esophageal achalasia, hiatal herniation, and gastroesophageal reflux with secondary esophagitis and esophageal dysmotility. Accordingly, the diagnostic approach to human and canine patients with swallowing impairment is similar. Diagnostic procedures such as swallowing fluoroscopy, high-resolution manometry, pH/impedance monitoring, and endolumenal functional luminal imaging probe can be performed in both species; however, nasofacial conformation, increased esophageal length, and the difficulty of completing several of these procedures in awake dogs are inherent challenges that need to be considered. Human patients can convey their symptoms and respond to verbal cues, whereas veterinarians must rely on clinical histories narrated by pet owners followed by comprehensive physical examination and observation of the animal eating different food consistencies and drinking water. Dogs may also be unwilling to drink or eat in the hospital setting and may be resistant to physical restraint during diagnostic procedures. Despite the species differences and diagnostic challenges, dogs are a natural animal model for many oropharyngeal and esophageal disorders affecting people, which presents a tremendous opportunity for shared learnings. This manuscript reviews the comparative aspects of esophageal anatomy and physiology between humans and canines, summarizes the diagnostic assessment of swallowing impairment in both species, and discusses future considerations for collaborative medicine and translational research.

The Effect of the Preoperative Fasting Regimen on the Incidence of Gastro-Oesophageal Reflux in 90 Dogs

Simple Summary

Gastro-oesophageal reflux (GOR), a potential risk during anaesthesia, happens when the stomach contents move up into the oesophagus. The refluxed contents can damage the lining of the oesophagus or the respiratory tract. For many years it was believed that an increase in the stomach contents’ volume increases the risk of GOR. However, more recent studies have demonstrated this to be incorrect. The objective of this study was to compare the effects of three different pre-anaesthetic fasting regimens on the frequency of GOR in dogs under anaesthesia. Ninety dogs undergoing non-abdominal and non-thoracic elective surgery were included in the study and equally allocated to three groups. The results of this study suggest that the administration of a meal 3 h before anaesthesia does not have any beneficial effect in the reduction of GOR incidence in dogs compared to the administration of a meal 12 h before anaesthesia.

Abstract

This study aimed to investigate the effect of three different preoperative fasting regimens on the incidence of gastro-oesophageal reflux (GOR) in dogs under general anaesthesia. Ninety dogs undergoing non-abdominal and non-thoracic elective surgery were included in the study and equally allocated to three groups. Dogs received canned food providing half the daily resting energy requirements (RER) 3 h prior to premedication (group 3H), a quarter of the daily RER 3 h before premedication (group 3Q), and half the daily RER 12 h before premedication (group 12H). The animals were premedicated with acepromazine and pethidine, anaesthesia was induced with propofol and maintained with isoflurane vaporised in oxygen. Oesophageal pH was monitored throughout anaesthesia. Demographic and surgery-related parameters were not different among groups. The incidence of GOR was 11/30 in group 3H (36.7%), 9/30 in group 3Q (30.0%) and 5/30 in group 12H (16.7%), which was not statistically different (p = 0.262). Reduction of the amount of the preoperative meal from half to a quarter of the daily RER did not reduce the incidence of GOR but resulted in a lower oesophageal pH (p = 0.003). The results of this study suggest that the administration of a meal 3 h before anaesthesia does not have any beneficial effect in the reduction of GOR incidence in dogs compared to the administration of a meal 12 h before anaesthesia.

A Systematic Review of the Methods of Assessment of Gastro-Oesophageal Reflux in Anaesthetized Dogs

Simple Summary

Regurgitation and gastro-oesophageal reflux (GOR) are common complications in dogs under anaesthesia. We reviewed the definitions and methods of GOR assessment in anaesthetized dogs published in 22 scientific papers to assess if studies were comparable (i.e., looking at the same thing). The definition of GOR implied the presence of fluids not reaching the mouth or nose in the oesophagus in all studies. Most studies measured the acidity in the oesophagus to state if fluids were present or not. The probes were not always placed in the same location and definitions varied. This means that it is complicated to compare findings of the different studies.

Abstract

We reviewed the definitions and methods of assessment of gastro-oesophageal reflux (GOR) in anaesthetized dogs. Three databases were used. Titles and abstracts were screened by two of the authors independently. A total of 22 studies was included in the analysis. The definition of GOR implied the presence of fluids not reaching the mouth or nose in the oesophagus in all studies. Most studies considered a change in pH using oesophageal pH meters as the sole method of assessment. Calibration of the pH probe was inconsistently reported. The position of the tip of the oesophageal probe was inconsistent and not always precisely described. The correct positioning in the intended location was verified in a limited number of studies. Some studies considered that GOR had happened for changes in pH below 4.0 or above 7.5 while others considered that GOR had happened when the pH dropped below 4.0 only. Some studies stated that the pH change had to be sustained for a minimum period of time (20 or 30 s) whereas others did not mention any duration. The variability of definitions and methods of assessment of GOR in anaesthetized dogs precludes meaningful comparison of the findings. Re-evaluation and uniformization of the methods appear necessary.

Incidence of Gastroesophageal Reflux in Dogs Undergoing Orthopaedic Surgery or Endoscopic Evaluation of the Upper Gastrointestinal Tract

Gastroesophageal reflux (GER) is a common event during general anaesthesia but is often underdiagnosed in veterinary medicine. The oesophageal pH in anaesthetised dogs undergoing endoscopic evaluation of the upper gastrointestinal tract (END group; n = 12) or orthopaedic surgery (ORT group; n = 12) was measured using an oesophageal probe. The dogs were sedated with acepromazine or with methadone or butorphanol, and anaesthesia was induced with propofol and maintained with isoflurane. Of the 24 dogs in this study, 21 (87.5%) had an episode of GER during anaesthesia. The incidence of GER, as well as the first, the minimum, and the maximum pH values, did not differ significantly between the groups. The mean maximum difference versus the first pH value was higher for dogs in the END group (−2.6 ± 3.5) as compared with those in the ORT group (−0.7 ± 2.5), although they were not statistically significant (p = 0.25). The administration of methadone or butorphanol had no significant effect on the development of acidic reflux or biliary reflux. In the acepromazine-sedated dogs, the incidence of GER did not differ significantly between patients undergoing an endoscopic procedure and those undergoing orthopaedic surgery; however, during endoscopy, fluctuations in the oesophageal pH can be expected, even without any clinical signs of GER.

Gastroduodenal Ulceration in Small Animals: Part 2. Proton Pump Inhibitors and Histamine-2 Receptor Antagonists

In the first part of this review, we discussed the pathophysiology and epidemiology of gastric acid secretion and the epidemiology of gastroduodenal ulceration in dogs and cats. In this section, we discuss the pharmacology and evidence-based clinical use of histamine-2 receptor antagonists and proton pump inhibitors.

Effects of Anesthesia on Pediatric pH Impedance

OBJECTIVES

Anesthesia can alter gastric and small intestinal motility, but its effect on gastroesophageal reflux (GER) is unclear. We set out to evaluate the effect of anesthesia on pH-multichannel intraluminal impedance (pH impedance) evaluation of GER.

METHODS

Retrospective single-center analysis of 95 pH impedance probe studies performed in patients both with anesthesia exposure and esophagogastroduodenoscopy (n = 50) and without (n = 45).

RESULTS

Increased acid reflux per hour, nonacid reflux per hour, and total reflux per hour were observed in the first 4 hours, both overall and in children 1 year or older and in both sedation groups. This difference remained for the older children without sedation by multiple regression analysis for nonacid reflux per hour and total reflux per hour. Patients using proton pump inhibitors had more nonacid reflux events per hour and total reflux events per hour regardless of sedation.

CONCLUSIONS

Based on the results of the present study, there is no need to eliminate the data collected immediately after placement of the probe in children younger than 1 year of age, but in those who are 1 year or older without sedation, there may be a greater number of reflux events in the first 4 hours. The first 4 hours, therefore, should be carefully evaluated in patients older than 1 year of age. Further study is needed to provide normative data for the first 4 hours versus the later time period, both for those undergoing sedation and for unsedated patients, to validate the findings from the present study and to better understand the mechanism of GER.

Wireless ambulatory esophageal pH monitoring in dogs with clinical signs interpreted as gastroesophageal reflux

Background

Although gastroesophageal reflux (GER) often is assumed to be causative for upper gastrointestinal and respiratory signs in dogs, no attempts have been made to verify this assumption.

Objectives

To monitor esophageal pH with the Bravo pH system in healthy dogs and client‐owned dogs displaying signs commonly attributed to GER.

Animals

Seven healthy and 22 client‐owned dogs.

Methods

After routine esophagogastroduodenoscopy, radiotelemetric pH capsules were placed in distal esophagus for continuous pH recording. Reflux was defined as single pH measurement <4. At discharge, owners were instructed to press individually predefined clinical sign‐buttons on the receiver whenever indicated. Results between groups were compared using Mann–Whitney U‐test.

Results

The median (range) number of refluxes in client‐owned and healthy dogs, respectively, was 17 (1–205) and 10 (1–65), the number of refluxes >5 minutes in duration was 1 (0–14), and 1 (0–4), duration of longest reflux (min) was 10 (0–65) and 8 (0–27), and fractional time pH <4 (%) was 0.76% (0.01–6.28), and 0.3% (0–3.1). No differences were found between groups. The median of 7 (1–35) clinical sign‐button pushes were recorded in 21 dogs. Median of 12.5% (2.8% [1/35]–50% [2/4]) reflux‐positive clinical sign‐button pushes was found in 10 dogs with reflux‐positive pushes. Five (22.7%) dogs had increased esophageal acid exposure, and mild esophagitis was noted in 1 dog.

Conclusion and Clinical Importance

Despite evidence of increased GER in some dogs, the clinical sign‐reflux association remained poor. Future investigation should focus on dogs with esophagitis.