Intravenous loss of over-the-wire catheter guidewires in 13 horses.

BACKGROUND: Over-the-wire (OTW) catheter placement is performed frequently in horses. Intravascular loss of a guidewire has been anecdotally reported, but there is limited information regarding the treatment and outcome of horses that have experienced this complication of OTW catheter placement. OBJECTIVES: Describe the clinical and diagnostic features, treatment, and outcome of horses experiencing IV guidewire loss at the time of OTW catheter placement. ANIMALS: Thirteen horses. METHODS: Multicenter retrospective study to identify horses with IV guidewire loss. Horses of all ages were considered for inclusion. Horses were excluded from the study if complete medical records of signalment, indication, and outcome were not available. Intravenous guidewire loss was defined as the guidewire being lost IV at the time of OTW catheter placement. RESULTS: No horses in this study experienced adverse clinical signs associated with the loss of a guidewire. Eight horses had the guidewire removed and the guidewire was left in situ in 5 horses. None of the horses with the guidewire in situ had experienced long-term effects. CONCLUSIONS AND CLINICAL IMPORTANCE: Intravenous guidewire loss seems to have a good long-term prognosis even in horses in which removal of the guidewire was not possible. Thus, in horses where guidewire removal is not feasible, guidewires that remain in situ may have limited to no adverse effects.

Effects of Bit Chewing on Gastric Emptying, Small Intestinal Transit, and Orocecal Transit Times in Clinically Normal Horses.

Ileus is a common life-threatening problem in horses, and currently available treatments may be ineffective. The purpose of this study was to determine whether bit chewing, a form of sham feeding, decreases the gastric emptying time (GET), small intestinal transit time (SITT), and total orocecal transit time (OCTT) in clinically normal horses in a prospective crossover study. Nine healthy horses were acclimated and fed a standardized diet. Following 24 h of fasting, self-contained video endoscopy capsules and acetaminophen were administered into the stomach via a nasogastric tube. Each horse underwent experimental (bit chewing for 20 min every 6 h) or control (no bit chewing) conditions, with a 3-week minimum washout period between conditions. The horses were enrolled in either part of the study until all video capsules were retrieved and/or 30 days lapsed. The video capsules were recovered from manure, and GET, SITT, and OCTT were determined from a video analysis. Bit chewing significantly decreased OCTT (p = 0.015) compared to the control conditions. Bit chewing decreased GET and SITT, but the differences were not significant. The mean (median) times determined via the video capsule analysis for the bit-chewing conditions were as follows: GET, 2.34 h (2.86 h); SITT, 3.22 h (3.65 h); and OCTT, 5.13 h (6.15 h), and for the control conditions, they were as follows: GET, 3.93 h (5 h); SITT, 3.79 h (4.4 h); and OCTT, 8.02 h (9.92 h). Bit chewing decreased OCTT in healthy horses. Because this segment of the gastrointestinal tract is frequently affected by ileus, bit chewing may be a safe and inexpensive intervention for that condition in horses. Further investigation in clinical patients with ileus is warranted.

The Clinical Pharmacology and Therapeutic Evaluation of Non-Steroidal Anti-Inflammatory Drugs in Adult Horses.

This review firstly examines the underlying pathophysiology of pain and inflammation associated with orthopedic disease and endotoxemia. Then, it reviews the clinical pharmacology (pharmacokinetics and pharmacodynamics) of both conventional and non-conventional NSAIDs in the adult horse, and finally provides an overview of different modalities to evaluate the therapeutic efficacy of NSAIDs in research.

Pharmacokinetics and efficacy of orally administered acetaminophen (paracetamol) in adult horses with experimentally induced endotoxemia.

BACKGROUND: Acetaminophen has been evaluated in horses for treatment of musculoskeletal pain but not as an antipyretic. OBJECTIVES: To determine the pharmacokinetics and efficacy of acetaminophen compared to placebo and flunixin meglumine in adult horses with experimentally induced endotoxemia. ANIMALS: Eight university owned research horses with experimentally induced endotoxemia. METHODS: Randomized placebo controlled crossover study. Horses were treated with acetaminophen (30 mg/kg PO; APAP), flunixin meglumine (1.1 mg/kg, PO; FLU), and placebo (PO; PLAC) 2 hours after administration of LPS. Plasma APAP was analyzed via LC-MS/MS. Serial CBC, lactate, serum amyloid A, heart rate and rectal temperature were evaluated. Serum IL-1ß, IL-6, IL-8, IL-10, and TNF-α were evaluated by an equine-specific multiplex assay. RESULTS: Mean maximum plasma APAP concentration was 13.97 ± 2.74 µg/mL within 0.6 ± 0.3 hour after administration. At 4 and 6 hours after treatment, both APAP (P = <.001, P = .03, respectively) and FLU (P = .0045 and P < .001, respectively) had a significantly greater decrease in rectal temperature compared to placebo. FLU caused greater heart rate reduction than APAP at 4 and 6 hours (P = .004 and P = .04), and PLAC at 4 hours (P = .05) after treatment. CONCLUSIONS AND CLINICAL IMPORTANCE: The pharmacokinetics of acetaminophen in endotoxemic horses differ from those reported by previous studies in healthy horses. Acetaminophen is an option for antipyresis in clinical cases, particularly when administration of traditional NSAIDs is contraindicated.

Pharmacokinetics and clinical efficacy of acetaminophen (paracetamol) in adult horses with mechanically induced lameness.

BACKGROUND: Acetaminophen has been used clinically in horses alone or combined with traditional non-steroidal anti-inflammatory drugs for treatment of musculoskeletal pain in horses. OBJECTIVES: To determine the pharmacokinetics and efficacy of acetaminophen at two doses in horses with mechanically induced lameness compared with phenylbutazone or placebo control. STUDY DESIGN: In vivo experiment. METHODS: Nine healthy mares with mechanical lameness induced via a reversible sole pressure horseshoe model were treated with acetaminophen (20 mg/kg PO; A20), acetaminophen (30 mg/kg PO; A30), phenylbutazone (2.2 mg/kg, PO; PB) and oral placebo (C) in a randomised four-way Latin square model. Plasma concentrations for A20 and A30 were analysed via LC-MS/MS and noncompartmental pharmacokinetic analysis. Heart rate and heart rate variability were measured using a portable telemetry. Lameness was scored by three blinded boarded equine surgeons using the AAEP and 10-point scales. RESULTS: Mean maximum plasma concentration (Cmax ) for A20 was 20.01 µg/ml within 0.66 h (Tmax ) after administration; The mean Cmax for A30 was 30.02 µg/ml with a Tmax of 0.43 h. Post-treatment heart rate for A30 was significantly lower than A20 at 1 and 7 h; lower than PB at 2, 3, 4.5 and 7 h; lower than C at 2, 3.5, 4.5, 6, 7 and 8 h. 10-point Lameness scores were significantly improved for A30 than C at 2 and 4 h post-treatment; PB was significantly improved than C at 8 h post treatment. There were no significant differences in lameness between A20, A30 and PB. MAIN LIMITATIONS: Small sample size, lack of objective lameness measurement. CONCLUSIONS: Acetaminophen at 30 mg/kg produced a more rapid improvement in lameness scores and heart rate compared with other treatments in this model. Further evaluation of the pharmacokinetics and safety of repeated oral dosing of acetaminophen at 30 mg/kg is needed to determine clinical utility.

CONTEXTO: Acetaminofeno tem sido usado rotineiramente em cavalos com dor musculoesquelética, tanto como terapia solo quanto em associação com outros anti-inflamatórios não esteroides tradicionais. OBJETIVOS: Determinar a farmacocinética e eficácia de duas doses de acetaminofeno em cavalos com claudicação mecanicamente induzida, e comparar com fenilbutazona e placebo. DELINEAMENTO DO ESTUDO: Estudo randomizado, cego e controlado utilizando quadrado latino. METODOLOGIA: Nove éguas adultas com claudicação induzida mecanicamente pelo método de aplicação de pressão na sola através de ferradura foram tratadas com acetaminofeno (20 mg/kg VO; A20), acetaminofeno (30 mg/kg VO; A30), fenilbutazona (2.2 mg/kg, VO; PB) e placebo oral (C) em um estudo quadrado latino de forma randômica. Concentração plasmática dos grupos A20 e A30 foram analisadas pelo método LC-MS/MS e análise farmacocinética não compartimentar. Frequência cardíaca e variação da frequência cardíaca foram mensuradas usando telemetria portátil. O grau de claudicação foi avaliado usando a escala de 10 pontos da AAEP por três cirurgiões especialistas (board-certified) que estavam cegos ao tratamento. RESULTADOS: A média máxima da concentração plasmática (Cmax ) do grupo A20 foi 20.01 µg/ml dentro de 0.66 h (Tmax ) da administração. A média Cmax do grupo A30 foi 30.02 µg/ml dentro da Tmax de 0.43 h. A frequência cardíaca do grupo A30 foi significativamente mais baixa do que a do grupo A20 nos momentos 1 e 7 h; mais baixa do que o grupo PB nos momentos 2, 3, 4.5 e 7 h; e mais baixa do que as do grupo C nos momentos 2, 3.5, 4.5, 6, 7 e 8 h. O grau de claudicação diminuiu significativamente no grupo A30 quando comparado com o grupo C nos momentos 2 e 4 h pós tratamento, e no grupo PB quando comparado com o grupo C no momento 8 h pós tratamento. Não houve diferença significativa em grau de claudicação quando os grupos A20, A30 e PB foram comparados. PRINCIPAIS LIMITAÇÕES: Número pequeno de animais, ausência de mensuração de claudicação objetiva. CONCLUSÕES: A dose de 30 mg/kg de acetaminofeno proporcionou uma superior melhora na escala de claudicação e frequência cardíaca quando comparada com os outros tratamentos avaliados neste estudo. Mais informações sobre a farmacocinética e efeitos da repetida dosagem de 30 mg/kg de acetaminofeno precisam ser avaliadas para determinar a sua aplicabilidade clínica.

Small intestinal pseudodiverticulosis in a pony mare.

A 14-y-old pony mare was referred after 30-d duration of intermittent pyrexia, anorexia, weight loss, and change in manure consistency. Physical examination revealed a palpable but reducible ventral abdominal mass. Transabdominal ultrasonography revealed multiple distended, hypomotile, and thickened small intestinal loops in close approximation with numerous, well-defined, hyperechoic masses. There was a large amount of echogenic peritoneal fluid; abdominocentesis revealed a neutrophilic and macrophagic inflammatory exudate, and a mixed bacterial population was cultured. Given the poor prognosis, the mare was euthanized. The autopsy findings included a large abdominal abscess, serosanguineous peritoneal fluid with fibrin strands, and ~50 outpouches communicating with the lumen and extending from the anti-mesenteric aspect of the duodenum, jejunum, and ileum. These structures were classified as pseudodiverticula based on the histologic absence of the tunica muscularis layer of the intestinal wall. Pseudodiverticula should be included as a differential etiology in horses when clinical signs consistent with colic, diarrhea, or weight loss are recognized and, when on examination, one or more organized masses are palpated or visualized on transabdominal ultrasound, as well as visualization of small intestinal loops with thickened walls.

Nutritional Considerations when Dealing with an Underweight Adult or Senior Horse.

Weight loss occurs when the supply of energy is insufficient to meet the energy needs of an individual. The energy supply may be reduced by inadequate provision of feed, inadequate consumption, reduced digestion and absorption, or disruption in metabolic processing. Increased energy expenditure occurs with exercise and during cold temperatures, pregnancy, and lactation. Underlying clinical disease, particularly chronic inflammation, neoplasia, and protein-losing conditions, can cause weight loss or exacerbate existing weight loss. A methodical approach to weight-loss investigation and treatment is necessary, because of the often multifactorial nature of this condition.

Pharmacokinetics and pulmonary distribution of Draxxin® (tulathromycin) in healthy adult horses.

The objective of this study was to determine the pharmacokinetics and tolerability of tulathromycin (Draxxin® ; 2.5 mg/kg once) after intramuscular (IM), subcutaneous (SC), and slow intravenous (IV) administration to six adult horses. A three-phase design and 4-week washout period were used. Drug concentrations in blood and bronchoalveolar lavage (BAL) samples were determined by ultra-performance liquid chromatography tandem mass spectrometry and pharmacokinetic parameters calculated using noncompartmental analysis. Following SC and IM administration, all horses exhibited sweating, discomfort, and periods of recumbency. As signs were more severe after SC administration this route was only used in 3/6 horses. Intravenous administration of tulathromycin was well tolerated in all horses. Mean bioavailability was 99.4% IM and 115% SC. Mean maximum plasma concentration was 645 ng/ml IM and 373 ng/ml SC. Mean half-life was 59.8 h, 54.8 h, and 57.9 h for IV, IM, and SC administration, respectively. Mean clearance was 3.25 ml/kg/min, and mean volume of distribution was 16.8 L/kg following IV administration. Drug was detectable in plasma and BAL samples for 120 h following all routes; however, adverse effects may prevent IM use and SC use is not recommended. Tulathromycin may be a practical and affordable antimicrobial for use in adult equine patients.

Catheter-associated venous air embolism in hospitalized horses: 32 cases.

BACKGROUND: Venous air embolism is a potentially life-threatening complication of IV catheter use in horses. Despite widespread anecdotal reports of their occurrence, few cases have been reported in the literature and the prognosis is currently unknown. HYPOTHESIS/OBJECTIVES: Our objective was to describe the surrounding circumstances, clinical signs, treatment, progression, and outcome of venous air embolism in hospitalized horses. ANIMALS: Thirty-two horses with acute onset of compatible clinical signs associated with IV catheter disconnection or damage. METHODS: Multicenter retrospective study. Data extracted from clinical records included signalment, presenting complaint, catheter details, clinical signs, treatments, and outcome. RESULTS: Most cases resulted from extension set disconnection occurring within approximately 24 hours after catheter placement. In fewer horses, extension set damage was cited as a cause. Common clinical signs included tachycardia, tachypnea, recumbency, muscle fasciculations and agitation, with abnormal behavior including kicking and flank biting. Less commonly, pathological arrhythmias or more severe neurologic signs, including blindness and seizures, were noted. Progression was unpredictable, with some affected horses developing delayed-onset neurologic signs. Mortality was 6/32 (19%), including 2 cases of sudden death and other horses euthanized because of persistent neurologic deficits. Negative outcomes were more common in horses with recorded blindness, sweating or recumbency, but blindness resolved in 5/8 affected horses. CONCLUSIONS AND CLINICAL IMPORTANCE: The prognosis for resolution of clinical signs after air embolism is fair, but permanent neurologic deficits or pathologic cardiac arrhythmias can arise. Unpredictable progression warrants close monitoring. Systematic clinic-based surveillance could provide additional useful information to aid prevention.

An investigation of the role of soluble CD14 in hospitalized, sick horses.

The objectives of this study were to (1) evaluate the effects of equine soluble CD14 (sCD14) and monoclonal antibodies (mAb) to equine CD14 on lipopolysaccharide-induced tumor necrosis factor α (TNF-α) secretion from equine peripheral blood mononuclear cells (PBMC); and to (2) determine serum concentrations of sCD14 in a population of horses with gastrointestinal diseases or other illnesses likely to result in endotoxemia. Equine PBMC isolated from 10 healthy horses were incubated with Escherichia coli LPS plus CD14 mAb or sCD14 and assayed for TNF-α activity. Pre-incubation with CD14 mAb did not inhibit LPS-induced TNF-α production, whereas use of sCD14 inhibited LPS-induced TNF-α production in a concentration-dependent manner. Additionally, blood samples from 55 ill and 23 healthy horses were used to determine serum concentrations of sCD14. Concentrations of sCD14 were positively correlated to respiratory rate, duration of clinical signs and band neutrophil count. Although serum sCD14 was significantly increased in the ill horses compared to healthy horses, sCD14 did not correlate with outcome. Results of this study indicate that release of sCD14 is increased in ill horses and that TNF-α production by PBMC is decreased when cells are treated with sCD14.

Induction and characterization of endotoxin tolerance in equine peripheral blood mononuclear cells in vitro.

Endotoxemia is responsible for severe illness in horses. Individuals can become clinically unresponsive to the endotoxin molecule after an initial exposure; a phenomenon referred to as 'endotoxin tolerance' (ET). ET has been observed clinically in horses in vivo; however, cytokine expression associated with ET has not been investigated. The purpose of this study was to develop and validate a method for inducing ET in equine peripheral blood mononuclear cells (PBMC) in vitro, and to describe selected cytokine responses which are associated with ET. ET was induced by culturing cells with three concentrations of endotoxin, and evaluated after a second dose of endotoxin given to challenge the cells. The relative mRNA expression of IL-10 and IL-12 was measured by use of quantitative PCR. ET was induced in all cells exposed to the 2-step endotoxin challenge. The relative mRNA expression of IL-10 in tolerized cells was not different from positive control cells. In contrast, the relative mRNA expression of IL-12 in tolerized cells was decreased by 15-fold after the second endotoxin challenge. This experiment demonstrated a reliable method for the ex vivo induction of ET in equine PBMC. A marked suppression of IL-12 production is associated with ET.

Gastric and enteric phytobezoars caused by ingestion of persimmon in equids.

CASE DESCRIPTION-13 equids (10 horses, 2 donkeys, and 1 pony) were examined for signs of colic (n = 7), weight loss (6), anorexia (3), and diarrhea (2). Ten equids were evaluated in the fall (September to November). Seven equids had a history of persimmon ingestion. CLINICAL FINDINGS-A diagnosis of phytobezoar caused by persimmon ingestion was made for all equids. Eight equids had gastric persimmon phytobezoars; 5 had enteric persimmon phytobezoars. Gastroscopy or gastroduodenoscopy revealed evidence of persimmon ingestion in 8 of 10 equids in which these procedures were performed. TREATMENT AND OUTCOME-2 of 13 equids were euthanatized prior to treatment. Supportive care was instituted in 11 of 13 equids, including IV administration of fluids (n = 8) and treatment with antimicrobials (5), NSAIDs (5), and gastric acid suppressants (4). Persimmon phytobezoar-specific treatments included dietary modification to a pelleted feed (n = 8); oral or nasogastric administration of cola or diet cola (4), cellulase (2), or mineral oil (2); surgery (4); and intrapersimmon phytobezoar injections with acetylcysteine (1). Medical treatment in 5 of 7 equids resulted in resolution of gastric persimmon phytobezoars. Seven of 8 equids with gastric persimmon phytobezoars and 1 of 5 equids with enteric persimmon phytobezoars survived > 1 year after hospital discharge. CLINICAL RELEVANCE-Historical knowledge of persimmon ingestion in equids with gastrointestinal disease warrants gastroduodenoscopy for evaluation of the presence of persimmon phytobezoars. In equids with gastric persimmon phytobezoars, medical management (including administration of cola or diet cola and dietary modification to a pelleted feed) may allow for persimmon phytobezoar dissolution.

Glucose and insulin dynamics associated with continuous rate infusion of dextrose solution or dextrose solution and insulin in healthy and endotoxin-exposed horses.

OBJECTIVE: To investigate the effects of a continuous rate infusion (CRI) of dextrose solution or dextrose solution and insulin on glucose and insulin concentrations in healthy and endotoxin-exposed horses. ANIMALS: 9 adult mares. PROCEDURES: During phase 1, treatments consisted of saline (0.9% NaCl) solution (control group; n = 4) or 20% dextrose solution (group 1; 4) administered IV as a 360-minute CRI. During phase 2, treatments consisted of 360-minute CRIs of 20% dextrose solution and insulin administered simultaneously at 367.6 mg/kg/h (30 kcal/kg/d) and 0.07 U/kg/h, respectively, in healthy horses (group 2; n = 4) or horses administered 35 ng of lipopolysaccharide/kg, IV, 24 hours before starting the dextrose solution and insulin CRIs (group 3; 4). A balanced crossover study design was used in both phases. Blood samples were collected for measurement of plasma glucose and insulin concentrations. RESULTS: Infusion of dextrose solution alone resulted in hyperglycemia for most of the 360-minute CRI. Insulin concentration increased significantly in group 1, compared with that in the control group. Mean insulin concentration of group 2 was significantly higher throughout most of the infusion period, compared with concentrations of the control group and group 1. Mean glucose concentration did not differ significantly between groups 2 and 3. CONCLUSIONS AND CLINICAL RELEVANCE: Insulin infusion at a rate of 0.07 U/kg/h was found to be effective for the prevention of hyperglycemia when administered concurrently with dextrose solution. This rate was considered to be safe because horses did not become hypoglycemic during infusions of dextrose solution.

Equine hyperlipidemias.

Hyperlipidemia is the presence of elevated lipid concentrations in the blood and is associated with periods of negative energy balance and physiologic stress. In increased concentrations, circulating lipids typically occur in the triglyceride form, which may interfere with numerous normal physiologic functions, particularly by reducing insulin sensitivity. Although the hyperlipidemia risk is greatest in ponies, miniature horses, and donkeys, all equids are at risk if they are in a situation involving negative energy balance. The sedentary lifestyle of many modern horses and the frequent feeding of high-carbohydrate diets contribute substantially to the risk of excessive fat mobilization and the development of hyperlipidemias.

Comparison of serum iohexol clearance and plasma creatinine clearance in clinically normal horses.

Objective-To determine whether a limited sampling time method based on serum iohexol clearance (Cl(iohexol)) would yield estimates of glomerular filtration rate (GFR) in clinically normal horses similar to those for plasma creatinine clearance (Cl(creatinine)). Animals-10 clinically normal adult horses. Procedures-A bolus of iohexol (150 mg/kg) was administered IV, and serum samples were obtained 5, 20, 40, 60, 120, 240, and 360 minutes after injection. Urinary clearance of exogenous creatinine was measured during three 20-minute periods. The GFR determined by use of serum Cl(iohexol) and plasma Cl(creatinine) was compared with limits of agreement plots. Results-Values obtained for plasma Cl(creatinine) ranged from 1.68 to 2.69 mL/min/kg (mean, 2.11 mL/min/kg). Mean serum Cl(iohexol) was 2.38 mL/min/kg (range, 1.95 to 3.33 mL/min/kg). Limits of agreement plots indicated good agreement between the methods. Conclusions and Clinical Relevance-Use of serum Cl(iohexol) yielded estimates of GFR in clinically normal adult horses similar to those for plasma Cl(creatinine). This study was the first step in the evaluation of the use of serum Cl(iohexol) for estimating GFR in adult horses.

Feeding management of sick neonatal foals.

Nutritional support of the foal can be challenging because of the constant changes in nutritional requirements and dietary composition during the transition from neonate to weanling. Additional complexity arises because of dilemmas regarding the means and route of delivery of nutrition to the foal, and the possibility that metabolic dysfunction may impair the ability of the foal to use nutrients appropriately. This article provides practical information on enteral and parenteral nutritional support of sick neonatal foals. The potential benefits of a conservative, hypocaloric feeding strategy, particularly in the very sick patient, are also discussed.

Effects of small- and large-volume resuscitation on coagulation and electrolytes during experimental endotoxemia in anesthetized horses.

BACKGROUND: Small-volume resuscitation (SVR) has been advocated in place of large-volume isotonic resuscitation for the treatment of endotoxemia in horses. The effects of this type of therapy during experimental endotoxemia on electrolytes and coagulation have not been evaluated in the horse. As part of a larger project, the objective of this study was to determine the effects of SVR (hypertonic saline solution [HSS] plus hetastarch [HES]) on coagulation and serum electrolytes concentration, and to compare SVR with large- and small-volume isotonic resuscitation during experimental endotoxemia in anesthetized horses. HYPOTHESIS: SVR does not affect coagulation parameters or serum electrolyte concentrations when compared with either small- or large-volume isotonic crystalloids. ANIMALS: Horses were randomly assigned to 1 of 3 groups. Under halothane anesthesia, endotoxemia was induced by administering 50 microg/kg Escherichia coli endotoxin i.v. The horses were treated for 30 minutes with 15 mL/kg of balanced polyionic crystalloid solution (control), 60 mL/kg of balanced polyionic crystalloid solution (ISO), or 5 mL/kg of HSS followed by 10 mL/kg HES (HSS-HES). METHODS: Prospective randomized trial. RESULTS: Significant differences in coagulation parameters were not found among the groups. Thrombocytopenia was severe in all 3 groups. Serum ionized calcium concentration significantly decreased from baseline in control and ISO groups but not in the HSS-HES group. CONCLUSIONS AND CLINICAL IMPORTANCE: These results suggest that the HSS-HES combination, at the dosage used in this study had no adverse effects on coagulation beyond those produced by endotoxemia. HSS-HES may have a protective effect against endotoxemia-induced ionized hypocalcemia.

Cardiovascular and pulmonary effects of hetastarch plus hypertonic saline solutions during experimental endotoxemia in anesthetized horses.

BACKGROUND: Small volume resuscitation has been advocated as a beneficial therapy for endotoxemia in horses but this therapy has not been investigated in a prospective manner. The objective of this study was to determine the cardiopulmonary effects of small-volume resuscitation using hypertonic saline solution (HSS) plus Hetastarch (HES) during experimental endotoxemia in anesthetized horses. HYPOTHESIS: Treatment of horses with induced endotoxemia using HES-HSS does not alter the response of various cardiopulmonary indices when compared to treatment with either small- or large-volume isotonic crystalloid solutions. ANIMALS: Eighteen healthy horses were randomly assigned to 1 of 3 groups. Anesthesia was maintained with halothane. Endotoxemia was induced by administering 50 microg/kg of Escherichia coli endotoxin IV. The horses were treated over 30 minutes with 15 mL/kg of balanced polyionic crystalloid solution (control), 60 mL/kg of balanced polyionic crystalloid solution (ISO), or 5 mL/kg of HSS followed by 10 mL/kg of HES (HSS-HES). METHODS: Prospective randomized trial. RESULTS: Cardiac output (CO) after endotoxin infusion increased significantly (P < .05) from baseline in all groups, whereas mean central venous pressure increased significantly (P < .05) in the ISO group only. Mean pulmonary artery pressure increased from baseline (P < .05) in horses treated with isotonic fluids and HSS-HES. There was no effect of treatment with HSS-HES on CO, systemic vascular resistance (SVR), mean arterial pressure, blood lactate concentrations, or arterial oxygenation. CONCLUSIONS AND CLINICAL IMPORTANCE: The use of HSS-HES failed to ameliorate the deleterious hemodynamic responses associated with endotoxemia in horses. The clinical value of this treatment in horses with endotoxemia remains unconfirmed.

Concentrations of gentamicin in serum and bronchial lavage fluid after once-daily aerosol administration to horses for seven days.

OBJECTIVE: To assess gentamicin concentrations in serum and bronchial lavage fluid (BLF) of horses during a 24-hour period after once-daily aerosol administration of gentamicin (GAER) for 7 days and the pattern and degree of bronchial tree inflammation associated with repeated GAER. ANIMALS: 13 healthy adult horses (9 geldings and 4 mares). PROCEDURE: The treatment group comprised 8 horses, and 5 horses were untreated control animals. Gentamicin (20 mL of gentamicin [50 mg/mL]) was administered via aerosol once daily for 7 days. Samples of serum and BLF were obtained from all horses before GAER and 0.5, 4, 8, and 24 hours after the final day of GAER. Gentamicin concentrations were determined for all samples from treated horses, and cytologic examinations were performed on all BLF samples. RESULTS: Peak median BLF gentamicin concentration detected at 0.5 hours was 2.50 microg/mL. Median serum gentamicin concentration was < 0.50 microg/mL at all time points. Significant differences were not observed in total nucleated cell counts or differential cell counts in BLF between groups at any time point. Neutrophil count in BLF for all horses was increased over baseline at 4 and 24 hours. CONCLUSIONS AND CLINICAL RELEVANCE: We did not detect evidence of gentamicin accumulation or respiratory inflammation after once-daily GAER for 7 days. This protocol appears unlikely to result in local or systemic toxicosis. Repeated daily GAER to horses appears to be a safe procedure and may have clinical use in the treatment of horses with bacterial infections of the airways.