Effects of atropine and glycopyrrolate on esophageal, gastric, and tracheal pH in anesthetized dogs

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.

Prevalence of and covariates associated with the oculocardiac reflex occurring in dogs during enucleation

OBJECTIVE

To determine the prevalence of and covariates associated with the oculocardiac reflex (OCR) occurring in dogs during enucleations.

SAMPLE

145 dogs that underwent enucleation at 2 veterinary teaching hospitals between January 2010 and June 2015.

PROCEDURES

Information was collected from the medical records of included dogs regarding age and body weight at hospital admission, breed (for classification of brachycephalic status), and whether they had received anticholinergic drugs or a retrobulbar nerve block (RNB) prior to enucleation. An OCR was considered to have occurred if there was a sudden decrease of ≥ 30% in heart rate from the baseline value (mean heart rate prior to the sudden decrease) during surgery in the absence of intraoperative administration of opioids or α₂-adrenoceptor agonists. Associations were explored between the collected data and the prevalence of OCR by means of binomial logistic regression.

RESULTS

4.8% (7/145) of dogs had an OCR noted during enucleation. Dogs that received a preoperative RNB (n = 82) had significantly lower odds of an OCR being observed than dogs that received no preoperative RNB (OR, 0.12). No association with OCR was identified for age or brachycephalic conformation or for preoperative administration of anticholinergic drugs.

CONCLUSIONS AND CLINICAL RELEVANCE

These findings suggested that preoperative administration of an RNB, but not preoperative administration of anticholinergic drugs, was associated with a lower prevalence of OCR in dogs during enucleations.

A “Light Meal” Three Hours Preoperatively Decreases the Incidence of Gastro-Esophageal Reflux in Dogs

Emerging evidence from veterinary and medical clinical research shows that reducing preoperative fasting time may reduce the incidence of gastro-esophageal reflux (GER) intraoperatively. In order to evaluate the effect of two different preoperative fasting times on the incidence of GER during general anesthesia, 120 dogs were randomly assigned to two groups: administration of canned food 3 h before premedication (group C3, n = 60) and administration of canned food 10 h before premedication (group C10, n = 60). The animals were premedicated with propionyl-promazine. Anesthesia was induced with thiopental sodium and maintained with halothane. A pH electrode was introduced into the esophagus, and the esophageal pH was constantly monitored. Esophageal pH of less than 4 or greater than 7.5 was taken as an indication of GER. Three of the 60 dogs of group C3 and 12 of the 60 dogs of group C10 experienced a GER episode, the difference being statistically significant (P = .025). Feeding the dog 3 h before anesthesia at a half daily rate reduces significantly the incidence of GER during anesthesia, compared to the administration of the same amount and type of food 10 h before anesthesia. The administration of a half daily dose of an ordinary canine diet may be useful in clinical practice.

Effects of intramuscular injection of glycopyrrolate on Schirmer tear test I results in dogs

OBJECTIVE To determine effects of glycopyrrolate administered IM on Schirmer tear test I (STT I) measurements in dogs. DESIGN Prospective clinical study. ANIMALS 13 client- and staff-owned dogs. PROCEDURES For both eyes of each dog, STT I measurements were recorded twice 20 minutes apart (at T1 and T2) and 2 to 4 hours later (at T3). Glycopyrrolate (0.01 mg/kg [0.005 mg/lb]) was administered IM to all dogs (3 dogs received an injection of saline [0.9% NaCl] solution on an earlier occasion), and final STT I measurements were recorded 20 minutes later (at T4). Intraocular pressures, heart rate, and respiratory rate were also recorded at each time point. RESULTS Ophthalmic variables did not differ between right and left eyes. In all dogs, variables at T1, T2, or T3 (measurements before glycopyrrolate administration) did not differ; baseline values were therefore defined at T3. At T4, STT I measurements were significantly decreased (mean ± SD decrease, 67.4 ± 15.4% [mean actual decrease, 15.8 mm/min]). During the same period, mean heart rate increased by 26.5 ± 12.0% (mean actual increase, 30.2 beats/min). Glycopyrrolate had no effect on intraocular pressure or respiratory rate. In 5 dogs at 24 hours after glycopyrrolate treatment, STT I measurement in each eye had returned to baseline value. Saline solution treatment (3 dogs) had no effect on any variables. CONCLUSIONS AND CLINICAL RELEVANCE In dogs, IM injection of glycopyrrolate resulted in a clinically relevant transient decrease in aqueous tear production. Application of lacrimomimetics beginning at the time of or within 20 minutes after glycopyrrolate premedication is recommended until STT I measurements return to baseline.

The influence of esomeprazole and cisapride on gastroesophageal reflux during anesthesia in dogs

BACKGROUND

Gastroesophageal reflux (GER) is common in anesthetized dogs and can cause esophagitis, esophageal stricture, and aspiration pneumonia.

OBJECTIVE

To determine whether preanesthetic IV administration of esomeprazole alone or esomeprazole and cisapride increases esophageal pH and decreases the frequency of GER in anesthetized dogs using combined multichannel impedance and pH monitoring.

ANIMALS

Sixty-one healthy dogs undergoing elective orthopedic surgery procedures.

METHODS

Prospective, randomized, placebo-controlled study. Dogs were randomized to receive IV saline (0.9% NaCl), esomeprazole (1 mg/kg) alone, or a combination of esomeprazole (1 mg/kg) and cisapride (1 mg/kg) 12-18 hours and 1-1.5 hours before anesthetic induction. An esophageal pH/impedance probe was utilized to measure esophageal pH and detect GER.

RESULTS

Eight of 21 dogs in the placebo group (38.1%), 8 of 22 dogs in the esomeprazole group (36%), and 2 of 18 dogs in the combined esomeprazole and cisapride group (11%) had ≥ 1 episode of GER on impedance testing during anesthesia (P < .05). Esomeprazole was associated with a significant increase in gastric and esophageal pH (P = .001), but the drug did not significantly decrease the frequency of GER (P = .955). Concurrent administration of cisapride was associated with a significant decrease in the number of reflux events (RE) compared to the placebo and esomeprazole groups (P < .05).

CONCLUSIONS AND CLINICAL RELEVANCE

Preanesthetic administration of cisapride and esomeprazole decreases the number of RE in anesthetized dogs, but administration of esomeprazole alone was associated with nonacid and weakly acidic reflux in all but 1 dog.

Prevalence of gastrointestinal tract lesions in 73 brachycephalic dogs with upper respiratory syndrome

OBJECTIVES

To determine the prevalence of gastrointestinal tract lesions in brachycephalic dogs with upper respiratory tract disease.

METHODS

The gastrointestinal tract and respiratory disorders of 73 brachycephalic dogs presented with upper respiratory signs were evaluated. Clinical signs and endoscopic and histological anomalies of the upper digestive tract were analysed.

RESULTS

A very high prevalence of gastrointestinal tract problems in brachycephalic dogs presented with upper respiratory problems was observed clinically, endoscopically and histologically. Endoscopic anomalies of the upper digestive tract were present even in dogs without digestive clinical signs. Furthermore, histological evaluation of the digestive tract sometimes showed inflammatory lesions not macroscopically visible at endoscopy. Statistical analysis showed a relationship between the severity of the respiratory and digestive signs. This was significant in French bulldogs, males and heavy brachycephalic dogs.

CLINICAL SIGNIFICANCE

These observations show a correlation between upper respiratory and gastrointestinal tract problems in brachycephalic breeds with upper respiratory disease. Surgical treatment of respiratory disease could improve the digestive clinical signs, and/or gastro-oesophageal medical treatment could improve the outcome for surgically treated brachycephalic dogs.

Evaluation of the effects of premedication on gastroduodenoscopy in cats

OBJECTIVE

To evaluate the effects of hydromorphone, hydromorphone and glycopyrrolate, medetomidine, and butorphanol premedication on the difficulty and time required to pass an endoscope into the stomach and duodenum of cats anesthetized with ketamine and isoflurane.

DESIGN

Randomized complete block crossover study.

ANIMALS

8 purpose-bred adult female cats.

PROCEDURES

Each cat was premedicated and anesthetized 4 times with an interval of at least 7 days between procedures. Cats were premedicated with hydromorphone, hydromorphone and glycopyrrolate, medetomidine, or butorphanol administered IM. Twenty minutes after premedication, sedation was assessed by use of a subjective ordinal scale. Cats received ketamine administered IM, and 10 minutes later a cuffed orotracheal tube was placed and anesthesia maintained with isoflurane. Cats breathed spontaneously throughout the procedure. When end-tidal isoflurane concentration was stable at 1.4% for 15 minutes, endoscopy was begun. The times required to pass the endoscope through the cardiac and pyloric sphincters were recorded, and the difficulty of endoscope passage was scored by use of a subjective ordinal scale.

RESULTS

No significant differences in difficulty or time required to pass the endoscope through the cardiac and pyloric sphincters were found among premedicant groups. Premedication with medetomidine resulted in the greatest degree of sedation and longest time to return to sternal recumbency.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that hydromorphone, hydromorphone and glycopyrrolate, medetomidine, and butorphanol at the doses tested can be used satisfactorily to premedicate cats prior to general anesthesia for gastroduodenoscopy.

Gastroesophageal reflux and tracheal aspiration in the thoracotomy position: should ranitidine premedication be routine?

Aspiration of gastric contents may contribute to pulmonary complications after thoracotomy. The incidence of gastroesophageal reflux (GER) and tracheal acid aspiration in patients undergoing thoracotomy in the lateral position is unknown. Ranitidine premedication reduces gastric volume, increases gastric pH, and may reduce GER. We used continuous intraluminal esophageal and tracheal pH monitoring probes to investigate the effect of ranitidine on the incidence of GER and tracheal aspiration in 80 adult patients undergoing thoracotomy. The study was placebo-controlled, randomized, and double-blinded. Patients at high risk of GER were excluded from the study. The incidence of acid GER in the placebo and ranitidine groups was 28.2% and 2.5%, respectively (P = 0.006). Multiple episodes of GER occurred in some patients in the placebo group only. The total number of episodes of GER in the placebo and ranitidine groups was 16 and 1, respectively (P = 0.002). The incidence of tracheal acid aspiration in the placebo and ranitidine groups was 7.7% and 2.5%, respectively (not significant). Patients undergoing thoracotomy are therefore at high risk of acid GER, which may lead to tracheal acid aspiration in an appreciable proportion. Premedication with ranitidine significantly reduces, but does not eliminate, the incidence of this potentially life-threatening complication.

IMPLICATIONS

Gastroesophageal reflux (GER) and tracheal aspiration of acid may increase morbidity and mortality in patients undergoing thoracotomy. This randomized, double-blinded, placebo-controlled study demonstrates frequent incidences of both acid GER and tracheal acid aspiration during surgery that are significantly reduced by premedication with ranitidine.

Newer diagnostic and surgical techniques and their impact on anesthesia

There are several newer diagnostic and surgical techniques available to veterinarians today. Careful anesthetic management is essential when using these modalities both to avoid accidents and to enable their use. For example, total intravenous anesthetic techniques can be used if the airway is occupied by an endoscope or laser surgery is being performed in the airway. The anesthesiologist must also be aware of the physiological changes that may occur during procedures such as laparoscopy and act to minimize their impact on patients.