Cardiopulmonary and sedative effects of intravenous administration of low doses of medetomidine and xylazine to adult horses.

OBJECTIVE: To determine the cardiopulmonary and sedative effects of medetomidine hydrochloride in adult horses and to compare those effects with effects of an equipotent dose of xylazine hydrochloride. ANIMALS: 10 healthy adult female horses. PROCEDURE: 5 horses were given medetomidine (4 microg/kg of body weight, i.v.), and the other 5 were given xylazine (0.4 mg/kg, i.v.). Heart rate, respiratory rate, arterial blood pressures, pulmonary arterial blood pressures, and cardiac output were recorded, and sedation and ataxia scores were assigned before and every 5 minutes after drug administration for 60 minutes. Rectal temperature and blood gas partial pressures were measured every 15 minutes after drug administration. RESULTS: Arterial blood pressure was significantly decreased throughout the study among horses given medetomidine and was significantly decreased for 40 minutes among horses given xylazine. Compared with baseline values, cardiac output was significantly decreased 10, 20, and 40 minutes after administration of medetomidine and significantly increased 40 and 60 minutes after administration of xylazine. Despite the significant decrease in respiratory rate in both groups, results of blood gas analyses were not significantly changed over time. Ataxia and sedation scores were of similar magnitude for the 2 groups, but ataxia persisted slightly longer among horses given medetomidine. Horses resumed eating hay 10 to 55 minutes after drug administration. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that equipotent low doses of medetomidine and xylazine induce comparable levels of ataxia and sedation and similar cardiopulmonary changes in adult horses.

Hemodynamic and metabolic alterations associated with intravenous infusion of a combination of adenosine triphosphate and magnesium chloride in conscious horses.

OBJECTIVE: To determine hemodynamic and metabolic effects of IV infusion of ATP-MgCl2 combination and maximal safe IV infusion rate in conscious horses. ANIMALS: 6 adult female horses. PROCEDURE: All horses received an IV infusion of ATP-MgCl2 combination, beginning at a rate of 0.05 mg of ATP/kg of body weight/min, which was increased by 0.05 mg/kg/min increments at 10-minute intervals until a rate of 1.0 mg/kg/min was achieved. Data were collected prior to the start of the infusion, at the end of each infusion rate, and at 15-minute intervals for the next hour after discontinuation of the infusion. Measured or calculated hemodynamic variables included cardiac output, cardiac index, heart rate, stroke volume, systemic and pulmonary arterial pressures, and systemic and pulmonary vascular resistances. Arterial blood gas tensions, CBC, plasma biochemical profiles, urine volume and specific gravity, and selected clinical signs of disease also were evaluated. RESULTS: Intravenous infusion of ATP-MgCl2 significantly increased cardiac output, decreased systemic vascular resistance, and caused mild pulmonary hypertension. Magnitude of the hemodynamic alterations was dependent on rate of infusion. Maximal safe infusion rate for these horses was 0.3 mg/kg/min. All horses became lethargic, and their appetites diminished during the infusion; 5 horses had mild signs of abdominal discomfort. Flank sweating was observed in all horses as infusion rate increased. Urine volume and specific gravity and hematologic, biochemical, and arterial blood gas alterations were detected during and after infusion. CONCLUSIONS AND CLINICAL RELEVANCE: Intravenous administration of ATP-MgCl2 in healthy, conscious, adult horses caused various metabolic and hemodynamic alterations that were without appreciable detrimental effects.

Plasma and urine nitric oxide concentrations in horses given below a low dose of endotoxin.

OBJECTIVE: To quantify plasma and urine nitric oxide (NO) concentrations before and after low-dose endotoxin infusion in horses. ANIMALS: 11 healthy adult female horses. Procedure-Eight horses were given endotoxin (35 ng/kg of body weight,i.v.) over 30 minutes. Three sentinel horses received an equivalent volume of saline (0.9% NaCl) solution over the same time. Clinical signs of disease and hemodynamic variables were recorded, and urine and plasma samples were obtained to measure NO concentrations prior to endotoxin infusion (t = 0) and every hour until postinfusion hour (PIH) 6, then every 2 hours until PIH 24. Blood for hematologic and metabolic analyses and for serum cytokine bioassays were collected at 0 hour, every hour until PIH 6, every 2 hours through PIH 12, and finally, every 6 hours until PIH 24. RESULTS: Differences in plasma NO concentrations across time were not apparent, but urine NO concentrations significantly decreased at 4 and 20 to 24 hours in endotoxin-treated horses. Also in endotoxin-treated horses, alterations in clinical signs of disease, and hemodynamic, metabolic, and hematologic variables were significant and characteristic of endotoxemia. Serum interleukin-6 (IL-6) activity and tumor necrosis factor (TNF) concentrations were increased above baseline values from 1 to 8 hours and 1 to 2 hours, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Plasma and urine NO concentrations did not increase in horses after administration of a low dose of endotoxin, despite induction of an inflammatory response, which was confirmed by increased TNF and IL-6 values characteristic alterations in clinical signs of disease, and hematologic, hemodynamic and metabolic variables.

Prepubic urethrostomy for permanent urinary diversion in two Vietnamese pot-bellied pigs.

Two Vietnamese pot-bellied pigs were evaluated because of disruption of the distal portion of the urethra. In 1 pig, disruption was a complication of castration; in the other, disruption was associated with a stricture at the junction of the membranous and penile portions of the urethra. Prepubic urethrostomy was performed in the first pig, because the urethra and penis had been damaged extensively during castration and primary repair of the urethra was not considered possible. Prepubic urethrostomy was performed in the second pig, because the stricture was too close to the vesicourethral junction for perineal urethrostomy to be successful. Both pigs recovered without complications and maintained urinary continence. Lack of tension at the urethrostomy site, atraumatic tissue handling, spatulation of the urethral orifice, and accurate apposition of the urethral mucosa to the skin margin are essential to maintain urinary continence and to prevent stricture of, and urine-induced dermatitis around, the urethrostomy site.

Tourniquet-induced hypertension in an ostrich.

Surgery was performed on a 3-year-old 110-kg male ostrich (Struthio camelus) to remove a sequestrum from the dorsal aspect of the left tarsometatarsal bone. A pneumatic tourniquet was positioned proximal to the surgical site and inflated to 600 mm of Hg. Systolic blood pressure increased 35% over 105 minutes while the tourniquet was inflated. Systolic blood pressure decreased 31.5% within 30 seconds after removal of the tourniquet pressure. Recovery from anesthesia and surgery was routine. The tourniquet-induced hypertension in this ostrich was similar to that reported for human beings and horses.

Isoflurane anesthesia in a rhinoceros.

During surgical exploration of the reproductive tract of a 15-year-old female white rhinoceros, anesthesia was maintained by administration of isoflurane in oxygen. Anesthesia was induced with IM administration of etorphine, and, to facilitate endotracheal intubation, muscle relaxation was achieved by IV administration of additional etorphine, acepromazine maleate, guaifenesin, and thiamylal sodium. Minor complications encountered during the anesthetic monitoring period included hypoventilation and ventilation/perfusion inequality, which contributed to hypoxemia. Recovery was not evaluated because the rhinoceros was euthanatized at the end of the surgical procedure.

Fluid therapy.

Fluid therapy is an integral part of treatment of the equine emergency patient. In this article, general principles of fluid therapy are discussed, including formulas for calculation of fluid volumes, fluid types and their indications, and specific therapy for several emergency conditions.

Suspected malignant hyperthermia syndrome in a miniature pot-bellied pig anesthetized with isoflurane.

Hyperthermia developed in a 7-week-old Vietnamese pot-bellied pig after isoflurane anesthesia for routine ovariohysterectomy. Shivering and a sudden increase in heart rate were noticed 90 minutes after anesthetic induction, both of which persisted throughout the remaining anesthetic period. Rectal temperature increased from 37 C immediately after anesthetic recovery to a peak of 41.5 C, and remained high for 18 hours. Treatment included external cooling and treatment with dantrolene sodium. Malignant hyperthermia was suspected to be the cause of the clinical signs in this pig, but specific tests to support this diagnosis were not performed. This report illustrates that hyperthermia may develop in this breed of swine during isoflurane anesthesia, and rectal temperature should be monitored during and after the anesthetic period.