Equine Pulmonary Cryptococcosis: A Comparative Literature Review and Evaluation of Fluconazole Monotherapy.

Cryptococcus is the most common fungal respiratory pathogen in Australian horses, manifesting primarily as pulmonary granulomas. Disease severity at presentation is dependent on the athletic use of the horse. The diagnosis and estimation of disease severity are centred around clinical findings, cytological evaluation of respiratory tract secretions, diagnostic imaging, and antigen titre testing. Both the lateral flow assay and the latex cryptococcal antigen titre are used, and important similarities and differences between species are discussed. Cryptococcus gattii occurs with greater frequency than Cryptococcus neoformans in equine pulmonic cryptococcosis and can be successfully treated with enteral fluconazole monotherapy, with disease severity determining treatment length.

The relationship between bronchoalveolar lavage fluid cytology and airway hyper-reactivity in a population of Australian horses presented for poor performance.

OBJECTIVE: To investigate the relationship between bronchoalveolar lavage fluid cytology, particularly mast cells, and airway hyper-reactivity in athletic horses presented for poor performance that included a respiratory tract evaluation in two disparate locations in Australia. DESIGN: Multi-centre, retrospective and prospective cross-sectional study METHODS: Eighty four adult horses underwent both pulmonary function testing and histamine bronchoprovocation with a commercial flowmetric plethysmography system. A bronchoalveolar lavage was performed four to twelve hours later. Bronchoalveolar lavage fluid cytology was categorised using two differing classification systems to define mild equine asthma. Statistical analysis was used to assess associations between bronchoalveolar lavage fluid relative inflammatory cell percentages, and airway hyper-reactivity and their associated categorisations. RESULTS: Sixty four percent (54/84) of horses displayed airway hyper-reactivity, as defined by PC35 < 6 mg/ml of histamine. A relative mastocytosis was the most common bronchoalveolar lavage fluid cytological abnormality. Horses with a sole mast cell response of ≥ 5% within their bronchoalveolar lavage fluid displayed airway hyper-reactivity at a lower dose of nebulized histamine than horses with normal bronchoalveolar lavage fluid cytology. Horses with mixed cell responses (relative mast cell percentage > 2% and/or relative neutrophil percentage > 5% and/or eosinophil relative cell percentage ≥ 1%) displayed airway hyper-reactivity at a lower dose of nebulized histamine than horses with normal bronchoalveolar lavage fluid cytology. CONCLUSION: In the Australian context, recently revised increased bronchoalveolar lavage fluid cytology relative cell percentage cut offs appear appropriate for sole mast cell responses. The historical lower cut offs appear to be appropriate for mixed inflammatory cell responses.

Exercise-induced pulmonary haemorrhage in Thoroughbred racehorses: a longitudinal study.

BACKGROUND: Exercise-induced pulmonary haemorrhage (EIPH) is considered a progressive disease based on histopathology, but it is unknown if tracheobronchoscopic EIPH severity worsens over time. OBJECTIVES: The aim of this study was to examine tracheobronchoscopic EIPH changes over time in a population of Thoroughbred racehorses. A secondary aim was to identify factors that affect changes in tracheobronchoscopic EIPH severity between observations. STUDY DESIGN: Prospective, longitudinal, observational cross-sectional study. METHODS: Thoroughbred racehorses were examined with tracheobronchoscopy no earlier than 30 min after racing. Examinations were recorded and graded blindly by experienced veterinarians using a 0-4 scale. Horses with 2 or more observations were included in the analysis. The association between the previous and current EIPH score was investigated using a linear mixed effect model. Factors associated with transitioning from a lower to a high EIPH grade and vice versa were examined using multiple ordinal regression. A semi-parametric regression model was used to examine progression using the number of career starts as a marker for time. Models were adjusted for potential confounding variables. RESULTS: There were 2974 tracheobronchoscopic examinations performed on 747 horses. Blood was detected in over half of all examinations (55.6%). The population prevalence of EIPH increased as the number of examinations for each horse increased. The preceding EIPH score was significantly associated with the current EIPH score. Significant variables associated with moving between EIPH grades were the number of days since last racing, ambient temperature and weight carried. Tracheobronchoscopic EIPH is mildly progressive over the first thirty career starts. MAIN LIMITATIONS: Enrolment was voluntary. Horses were not followed for their entire career. CONCLUSION: Limiting the number of days in the current racing preparation and spacing races for horses with moderate to severe EIPH may be beneficial for reducing tracheobronchoscopic EIPH severity. The association between ambient temperature and EIPH warrants further investigation.

Factors associated with outcome in foals with neonatal isoerythrolysis (72 cases, 1988-2003).

BACKGROUND: Neonatal foals with isoerythrolysis (NI) often die, but the risk factors for death have not been identified. OBJECTIVES: To identify factors associated with outcome in foals with NI and to identify factors associated with death from liver failure or kernicterus in the same population. ANIMALS: Seventy-two foals with NI examined at referral institutions. METHODS: Retrospective case series. Information on signalment, clinical examination findings, laboratory testing, treatment, complications, outcome, and necropsy results were obtained. RESULTS: The overall survival rate was 75% (54 of 72). Liver failure (n=7), kernicterus (n=6), and complications related to bacterial sepsis (n=3) were the 3 most common reasons for death or euthanasia. The number of transfusions with blood products was the factor most strongly associated with nonsurvival in a multivariate logistic regression model. The odds of liver failure developing in foals receiving a total volume of blood products >or= 4.0 L were 19.5 (95% confidence intervals [CI]: 2.13-178) times higher than that of foals receiving a lower volume (P= .009). The odds of kernicterus developing in foals with a total bilirubin >or= 27.0 mg/dL were 17.0 (95% CI: 1.77-165) times higher than that of foals with a lower total bilirubin (P= .014). CONCLUSIONS AND CLINICAL IMPORTANCE: Development of liver failure, kernicterus, and complications related to bacterial sepsis are the most common causes of death in foals with NI. Foals administered a large volume of blood products are at greater risk for developing liver failure.

Hypertrophic cardiomyopathy in a Clydesdale gelding.

CASE REPORT: A 7-year-old Clydesdale gelding was referred with a history of progressive lethargy and ventral oedema. The horse developed diarrhoea after treatment with antibiotics by the referring veterinarian. History, clinical signs, imaging and laboratory findings were consistent with hypertrophic cardiomyopathy complicated by antibiotic-associated colitis. Progression of clinical signs prompted euthanasia and the antemortem diagnosis of hypertrophic cardiomyopathy was confirmed at postmortem examination. CONCLUSION: Primary HCM is reported as rare in horses, but specific descriptions are lacking. The history, clinical, laboratory and postmortem findings in this case supported a diagnosis of HCM, complicated by antibiotic-associated colitis.

Bronchoalveolar lavage fluid cytology and airway hyper-reactivity in clinically normal horses.

OBJECTIVE: To characterise the relationship between bronchoalveolar lavage fluid (BALF) cytology and pulmonary function testing with histamine bronchoprovocation (HBP) methods in a population of clinically normal horses. DESIGN: Cross-sectional study METHODS: Clinically normal adult horses (n = 33) underwent pulmonary function testing and HBP with a commercial flowmetric plethysmography system. BAL was performed 1-5 days later. Statistical analysis was used to assess associations between BALF cell concentration, relative inflammatory cell percentages and categorisation, and airway hyper-reactivity (AHR). RESULTS: AHR (PC35 ≤ 8 mg/mL) was demonstrated in 17 (52%) of the horses. Using current definitions, BALF cytology was consistent with inflammatory airway disease in 14 (42%) of the horses and 7 of those demonstrated either mastocytic and/or eosinophilic responses. There was no correlation between total inflammatory cell counts or relative percentage and AHR. No statistical association was found between BALF inflammatory cell categories and AHR. CONCLUSION: A direct association between cytological evidence of airway inflammation and AHR was not identified in this population of clinically normal horses. Determining the presence and measuring inflammatory cell mediators in BALF may more accurately reflect AHR. In addition, normal values for cell proportions in BALF may vary between different populations of horses and more appropriate regional reference ranges should be established.

Disseminated cryptococcosis including osteomyelitis in a horse.

A 4-year-old Arab mare was diagnosed with disseminated cryptococcosis, including osteomyelitis of the proximal phalanx of the left hind limb, osteomyelitis with associated soft tissue granuloma of a rib and disseminated, large cryptococcal nodules in the lungs. The lesion in the dorsoproximal aspect of the proximal phalanx had a large area of cortical lysis with spiculated periosteal new bone and extensive soft tissue swelling. The affected rib had a pathological fracture. Cryptococcal osteomyelitis has not been previously reported in horses but should be considered as a differential diagnosis, particularly in endemic regions.

The association between exercise-induced pulmonary haemorrhage and race-day performance in Thoroughbred racehorses.

BACKGROUND: Exercise-induced pulmonary haemorrhage (EIPH) is commonly implicated as a cause of poor athletic performance but there is limited and conflicting evidence for this association. OBJECTIVES: The aim of this study was to determine if EIPH, based on endoscopic examination after racing, is associated with a variety of novel and established performance parameters. STUDY DESIGN: Prospective, observational cross-sectional study. METHODS: Thoroughbred racehorses competing between 2012 and 2015 were examined on-course no earlier than 30 min after racing. Examinations were recorded and graded blindly by experienced veterinarians using a 0-4 scale. Linear mixed effect models were used for analysis of continuous response variables with horse name incorporated as a random effect to account for repeated sampling and horse variability. Generalised estimating equations were used for analysis of binary responses. Performance variables were examined in 2 models, comparing EIPH grade 0 to grades 1-4, and EIPH grade ≤2 compared with EIPH grades ≥3, controlling race factors that could influence performance. RESULTS: There were 3794 observations collected from 1567 horses. EIPH was detected in 55.1% of observations. Horses with grade 4 EIPH were significantly more likely to have a lower finishing position and finish further behind the winner, less likely to place in the first 3 positions and collect race earnings, collected less earnings per race start and were slower over the last 600 m of the race than horses without EIPH (grade 0). Similar associations were seen in Model 2, with horses with EIPH grade ≥3 having inferior performance when compared to horses with EIPH ≤2. MAIN LIMITATIONS: Enrolment was voluntary. CONCLUSION: Mild to moderate haemorrhage was not associated with inferior race day performance in this population of Thoroughbred racehorses.

The effect of dobutamine and bolus crystalloid fluids on the cardiovascular function of isoflurane-anaesthetised horses.

REASONS FOR PERFORMING STUDY: Cardiac output does not always increase with dobutamine administration in anaesthetised horses and information on peripheral perfusion is lacking. OBJECTIVES: To determine the effect of intravenous (i.v.) dobutamine infusion with and without a concurrent 20 mL/kg bodyweight (bwt) bolus of crystalloid fluids on the cardiovascular function of acepromazine premedicated, hypotensive, isoflurane-anaesthetised horses. STUDY DESIGN: Randomised, cross-over experiment. METHODS: A total of 6 horses aged 5-13 years, weighing 464-578 kg were premedicated with acepromazine 0.02 mg/kg bwt and then sedated with xylazine 0.8 mg/kg bwt i.v. Anaesthesia was induced with ketamine 2.2 mg/kg bwt and diazepam 0.08 mg/kg bwt i.v. and maintained with isoflurane, adjusted to achieve a target mean arterial pressure (MAP) (60 mmHg ± 5%) 60 min post-induction of anaesthesia (T0). One of 2 treatments was then given. In treatment D, dobutamine was initially infused at 0.5 µg/kg bwt/min and adjusted to achieve a target MAP (80 mmHg ± 5%) within 30 min of infusion initiation. In treatment D+F dobutamine was administered as described for treatment D, with 20 mL/kg bwt Hartmann's solution infused i.v. over 20 min. Cardiac index (CI), haemoglobin concentration ([Hb]), arterial oxygen content (CaO2 ), oxygen delivery index (DO2 I) and bilateral femoral arterial blood flow (FBF) were recorded at T0, 30 min following dobutamine initiation (T1) and 15 min following dobutamine cessation (T2). Data were analysed using a mixed-effect linear model (P<0.05 considered significant). RESULTS: A significant increase in DO2 I (P = 0.008, T0/T1), CaO2 (P = 0.0002, T0/T1) and [Hb] (P<0.0001, T0/T1) and in CaO2 (P = 0.0005, T1/T2) and [Hb] (P = 0.002,T1/T2) occurred during treatment D. A significant increase in FBF (P = 0.005, upper limb; P = 0.042 lower limb, T0/T1) occurred during treatment D+F. Significant differences between treatments were recorded at T1 ([Hb] P = 0.0001, CaO2 P = 0.0003) and T2 ([Hb] P = 0.013). There was no change in CI during either treatment. CONCLUSIONS: The increase in FBF seen with co-administration of fluids and dobutamine may provide a beneficial effect on muscle compared with the use of dobutamine alone.

Bar shoes and ambient temperature are risk factors for exercise-induced pulmonary haemorrhage in Thoroughbred racehorses.

REASONS FOR PERFORMING STUDY: Ambient temperature has been identified as a risk factor for exercise-induced pulmonary haemorrhage (EIPH) in racing Thoroughbreds. This warranted a more expansive investigation of climatic conditions on the incidence and severity of EIPH. The impact of other variables such as the type of bit used, tongue ties and nonstandard shoes has not been reported and also warrant investigation. OBJECTIVES: To examine the effect of various climatic variables as contributing risk factors for EIPH. Other previously uninvestigated variables as well as standard track and population factors will also be examined. STUDY DESIGN: Cross-sectional study. METHODS: Thoroughbred racehorses competing at metropolitan racetracks in Perth, Western Australia were examined 30-200 min post race with tracheobronchoscopy. Examination took place at 48 race meetings over a 12 month period. Examinations were graded (0-4), independently by two experienced veterinarians. Univariable analyses were performed and variables with a P<0.25 were entered into a multivariable logistic regression analysis. The analysis was performed twice using the presence of blood (EIPH grade 0 vs. grades ≥1) and EIPH grades ≤1 vs. EIPH grades ≥2 as dependent variables. RESULTS: Exercise-induced pulmonary haemorrhage was diagnosed in 56.6% of observations. Lower ambient temperature was significantly associated with EIPH grades ≥1 (OR 0.95; 95% CI 0.93-0.98) and EIPH grades ≥2 (OR 0.97; 95% CI 0.94-1.0). Bar shoes were significantly associated with EIPH grades ≥1 (OR 6.35; 95% CI 2.17-18.54) and EIPH grades ≥2 (OR 2.72; 95% CI 1.3-5.68). Increasing race distance was significantly associated with EIPH grade ≥1 and increasing lifetime starts was significantly associated with EIPH grade ≥2. CONCLUSIONS: Ambient temperature is a risk factor for EIPH in Thoroughbred racehorses, with lower temperatures associated with increased risk. Bar shoes are a novel risk factor for EIPH in this population.

Retrospective survey of bronchoalveolar lavage fluid cytology in Western Australian horses presented for evaluation of the respiratory tract: effect of season on relative cell percentages.

OBJECTIVE: To characterise the cytological changes in equine bronchoalveolar lavage (BAL) samples over multiple years to determine if the prevalence of a relative mast cell response was influenced by season. METHODS: Medical records of 228 horses with clinical signs consistent with non-infectious respiratory disease or poor performance where a BAL was performed were reviewed retrospectively. BAL fluid cytology and categorised clinical variables were analysed using a Chi-square test to determine associations. RESULTS: The predominant signalment was a racing horse between 2 and 6 years of age, and poor athletic performance was the most common presenting complaint. Based on published criteria, 69.7% of horses had abnormal BAL cytology. The presence of nasal discharge was the only clinical finding that differed significantly between horses with abnormal and normal cytology. The most common cytological derangement was a mixed cell response (26.7%), the majority of which comprised elevated percentages of neutrophils and mast cells. A solely neutrophilic response or mast cell response occurred with equal frequency (18% and 18.95%, respectively), and an isolated eosinophilic response was noted in 6.1% of cases. Of the horses with cytology consistent with non-infectious lower airway inflammation, 58.4% had increases in the relative percentage of mast cells. Cell profiles were significantly associated with season, with mastocytosis occurring more commonly in spring, whereas eosinophilic and neutrophilic responses were more common in summer. CONCLUSION: In this study, a relative mast cell increase was the most common cytological profile in horses with lower airway inflammation and was associated with season.

Effect of dietary composition on abomasal and duodenal myoelectrical activity.

The changes in the frequency of abomasal slow waves and their propagation, the abomasal spike burst rate and the duodenal spike burst rate were assessed in sheep fed three diets containing either 100 per cent concentrate, 50 per cent concentrate and 50 per cent forage, or 100 per cent forage. The frequency of abomasal slow waves and spike burst frequency were both significantly reduced in sheep fed the diets high in concentrate when compared with animals fed the 100 per cent roughage diet. The velocity of propagation of the slow waves and the duodenal spike burst frequency were not significantly affected by the dietary composition. The sheep consumed significantly less of the 100 per cent concentrate diet in the 45 minutes before recording than of the other two diets, but the amount of feed consumed was not correlated significantly with the changes observed in the myoelectrical activity. These are consistent with an inhibitory effect of concentrate on abomasal motility.

Pancytopenia secondary to lymphoid leukemia in three horses.

Pancytopenia was observed in two 3-year-old geldings and one 11-year-old mare. All horses had a brief history (2 days to 4 weeks) of fever, anorexia, and depression. One of the three horses had blast cells present on a peripheral blood smear. Examination of the bone marrow showed substantial infiltration with neoplastic lymphoid cells. At necropsy, neoplastic cells were restricted to the bone marrow in one horse, present in bone marrow, liver, and spleen in the second horse, and reported in multiple tissues in the third horse, including bone marrow, kidneys, lung, myocardium and lymph nodes. The value of a bone marrow aspirate and core biopsy in the investigation of pancytopenia is highlighted.

Cochet-Bonnet aesthesiometer-determined corneal sensitivity in neonatal foals and adult horses.

Corneal touch threshold (CTT) was measured in sick neonatal foals, healthy foals, and healthy adult horses with a Cochet-Bonnet aesthesiometer. The mean overall CTT for the adult horses, sick foals, and healthy foals was 4.82 +/- 0.87 cm, 3.21 +/- 0.24 cm, and 5.01 +/- 0.61 cm, respectively. The central cornea of adult horses was more sensitive than the limbal cornea. Corneal sensitivity was significantly reduced in sick neonatal foals compared to adults. The mean Schirmer I tear test values were significantly lower in foals than adults, and were 14.2 +/- 1.0 mm, 12.8 +/- 2.4 mm, and 18.3 +/- 2.1 mm wetting in sick neonatal foals, normal neonatal foals, and adult horses, respectively. Reduced corneal sensation and lower tear production may be associated with ulcerative keratitis and slow corneal healing in some foals.

Induction of the acute-phase cytokine, hepatocyte-stimulating factor/interleukin 6, in the circulation of horses treated with endotoxin.

Because hepatocyte-stimulating factor/interleukin 6 (IL-6) is the principal inducer of acute-phase protein synthesis in the liver, quantification of its activity in blood provides an early and sensitive assessment of the acute-phase response. Circulating IL-6 activity was monitored in 4 adult horses for 72 hours after IV administration of endotoxin. In 4 experiments performed at weekly intervals and in randomized order, each horse was given endotoxin--1,000 30, 1, and 0 ng/kg of body weight. Plasma IL-6 activity was quantified as the ability to promote growth of the IL-6-dependent B-cell hybridoma, B13.29 clone B9. Interleukin-6 activity (171 +/- 10.2 U/ml) was found in all pretreatment plasma samples and was significantly (P less than 0.05) increased above baseline from 2 to 12 hours after 1,000 ng of endotoxin/kg was given and at 3 hours after 30 ng of endotoxin/kg was given. After 1,000- or 30-ng/kgt dosage of endotoxin, peak plasma IL-6 activity (10,128 +/- 4,096 and 1,555 +/- 1,326 U/ml, respectively) was observed for 3 hours. The IL-6 response of endotoxin-treated horses began about 1 hour after tumor necrosis factor appeared in the circulation, and its course closely approximated the endotoxin-induced febrile reaction. Significant increase in plasma IL-6 activity was not detected in horses given 1 ng of endotoxin/kg or control buffer.

Computer-based collection and analysis of myoelectric activity of the intestine in horses.

Extracellular myoelectric activity from the terminal ileum, cecum, and colonic pelvic flexure was assessed in 4 adult horses. The collection and analysis of myoelectric data involved the development and use of a computer-based system. After collection, the myoelectric signal was digitally filtered to enhance the activity of interest. The smoothed signal was then processed by use of computer programs designed to identify and count spike-burst activity and estimate burst duration. The intense phases of myoelectric complexes also were identified. The propagation of myoelectric spike-burst activity was assessed over 3 electrode sites to identify the propagative patterns of intestinal motility. There was high correlation between the results of computer-based analysis and those of visual analysis. We concluded that the computer provides a fast, accurate, and reliable means of assessing myoelectric activity.

Effect of inhaled nitric oxide on experimentally induced pulmonary hypertension in neonatal foals.

OBJECTIVE: To evaluate the efficacy of inhaled nitric oxide (NO) in anesthetized healthy newborn foals with experimentally induced pulmonary hypertension. ANIMALS: Five 1- to 3-day-old foals. PROCEDURE: Anesthesia was induced and maintained with propofol, and foals were intubated and mechanically ventilated. Systemic pressure and pulmonary arterial pressure (P(PA)) were recorded every 30 seconds. Hypertension was induced via a hypoxic gas mixture or chemical vasoconstriction, using the thromboxane mimetic U46619. Nitric oxide was added at a concentration of 80 parts per million (ppm) for 6 minutes under baseline conditions and during pulmonary hypertension-induced alveolar hypoxia (inspired oxygen concentration = 0.08). Nitric oxide (20, 40, 80, and 160 ppm) was evaluated during U46619-induced hypertension. Samples for determination of arterial blood gas tensions were collected before and after each NO treatment. RESULTS: Inhaled NO (approx 80 ppm) did not have an effect on baseline variables. Infusion of U46619 (0.35 +/- 0.04 microg/kg of body weight/min) or alveolar hypoxia resulted in increased P(PA) and decreased arterial oxygenation (PaO2) and hemoglobin saturation (HbSat). The increase in P(PA) was attenuated, in a dose-dependent manner, by NO during U46619 infusion and reversed by NO during induced hypoxemia. The PaO2 and HbSat were significantly improved at all NO doses during U44619 infusion but not during alveolar hypoxia. For all inhaled NO concentrations, nitrogen dioxide and methoglobin values were < 5 ppm and 3%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Nitric oxide is a potent, selective vasodilator of the pulmonary circulation in healthy newborn foals. Inhaled NO may have value as a therapeutic agent in foals with pulmonary hypertension.

Influence of an abrupt change in diet on antroduodenal myoelectric activity in lactating cattle.

Effects of a change from a diet composed primarily of forage to a diet composed primarily of concentrate on abomasal antral and duodenal motility were assessed in 5 lactating Holstein cows. Antroduodenal motility was measured by use of 8 silver electrodes sutured to the abomasum and duodenum, and abomasal emptying was assessed by continuous measurement of intraduodenal pH. Both diets were fed to achieve a daily dry matter intake of 2.7 kg/100 kg of body weight. The abrupt change in diet did not alter antroduodenal myoelectric activity or abomasal emptying. Initiation of phase III of the migrating myoelectric complex in the proximal portion of the duodenum corresponded with a decrease in abomasal antral spiking activity and an increase in intraduodenal pH. Results suggest that a high concentrate diet alone does not adversely affect antroduodenal motility in adult dairy cattle.

Effects of general anesthesia on myoelectric activity of the intestine in horses.

Myoelectric activity was monitored from the terminal ileum, cecum, and colonic pelvic flexure by use of AgpAgCl bipolar electrodes in 4 adult horses before, during, and after general anesthesia. Horses were anesthetized by way of 3 commonly used regimens, including xylazine (1.1 mg/kg of body weight) and ketamine hydrochloride (2.2 mg/kg); thiopental sodium (7.7 mg/kg), followed by halothane vaporized in oxygen; and thiopental sodium (2.5 g) in guaifenesin (100 mg/ml) solution given to effect, followed by halothane in oxygen. All 3 anesthetic regimens decreased intestinal spike-burst activity in the areas monitored. The slowest return to preanesthetic myoelectric activity was observed after xylazine and ketamine administration. After both of the barbiturate/halothane anesthetic regimens, there was a rebound increase in spike-burst frequency, without alteration in the proportion of propagative myoelectric events. All 3 anesthetic regimens appeared to reset the timing of the small and large intestinal migrating myoelectric complexes. By 9 hours after recovery from anesthesia, the effects of anesthesia, irrespective of regimen, had disappeared. Although anesthesia significantly (P less than 0.05) altered intestinal myoelectric activity, no particular anesthetic regimen had a prolonged effect. Results of our study indicate that the particular chosen regimen of general anesthesia is unimportant in development of motility disturbances in horses after anesthesia.

Effect of bethanechol or erythromycin on gastric emptying in horses.

OBJECTIVE: To investigate the prokinetic effect of bethanechol and erythromycin in the upper gastrointestinal tract of healthy horses by measuring the gastric emptying (GE) rate of a radioactive meal. ANIMALS: 4 healthy adult horses. PROCEDURE: After food was withheld for 12 hours, horses were given 370 MBq of 99mTc-labeled sulfur colloid incorporated into egg albumen and 37 MBq of 111In-labeled diethyltriaminepentaacetic acid in 120 ml of water via nasogastric intubation. Intravenously administered treatments were 0.9% NaCl solution, erythromycin (0.1 or 1.0 mg/kg of body weight), or bethanechol (0.25 mg/kg). All drugs were given in 10 ml of 0.9% NaCl solution. Dual-phase scintigraphic images were obtained by use of a gamma camera. The best-fit function was determined for each study, and the resultant curves were then analyzed by use of least squares nonlinear regression. Two variables, time to 50% emptying of the stomach (T-50) and slope of the emptying curve, were derived from the calculated power exponential equation. CONCLUSIONS: Treatment had a significant (P < 0.05) overall effect on T-50 of solid-phase GE. The T-50 of bethanechol (30.09 +/- 10.01 minutes), erythromycin at 0.1 mg/kg (59.08 +/- 10.01 minutes), and erythromycin at 1 mg/kg (60.50 +/- 10.01 minutes) were significantly shorter than T-50 after saline administration (89.97 +/- 10.01 minutes). There was a trend (P = 0.09) for the slope of solid-phase GE of bethanechol and erythromycin (0.1 mg/ kg; P = 0.37) to be steeper than that of saline solution. For liquid-phase GE, the T-50 and the slope of bethanechol differed significantly (P < or = 0.05) from those for saline solution. CLINICAL RELEVANCE: Bethanechol and erythromycin significantly increased solid-phase GE in healthy horses and may have value for use as prokinetic agents in certain gastrointestinal tract diseases.