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  • Author or Editor: Sheila M. McGuirk x
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Summary

In an effort to better understand the role of vasodilators in the management of pulmonary hypertension associated with chronic heartworm disease (hwd), pulmonary hemodynamic measurements were obtained from 7 experimentally infected, anesthetized dogs before and after hydralazine administration (mean dose, 1.96 mg/kg of body weight). Five dogs were maintained on room air, while 2 were maintained on 100% oxygen during the hydralazine study. The hemodynamic effect of hydralazine in dogs with hwd was evaluated, using heart rate, cardiac index, mean pulmonary artery pressure, mean arterial pressure, total pulmonary resistance, total systemic resistance, total systemic resistance/total pulmonary resistance, left ventricular dP/dtmax, left ventricular end diastolic pressure, and left and right ventricular double products ([mean arterial pressure × heart rate] and [mean pulmonary artery pressure × heart rate], respectively). Responders were defined as those in which total pulmonary resistance decreased ≥ 20% without an increase in mean pulmonary arterial pressure and in which heart rate increase was ≤ 10%. Comparison was also made between maximal hemodynamic effect of hydralazine with that after 100% oxygen administration for 15 minutes to previously normoxemic dogs (n = 5). Significance was determined if P < 0.05, using the paired t-test.

Hydralazine induced significant reductions in mean pulmonary and systemic arterial pressures and total pulmonary resistance, with no significant change in heart rate, cardiac index, total systemic resistance, left ventricular dP/dtmax, left ventricular end diastolic pressure, or right and left ventricular double products. Four (57%) of the 7 dogs studied were considered responders. Pretreatment cardiac index, mean pulmonary artery pressure, and total pulmonary resistance did not allow differentiation of responders from nonresponders. However, pretreatment right ventricular end diastolic pressure was significandy less in responders than in nonresponders. Two dogs sustained hypotension after hydralazine administration, but no dogs had significant tachycardia. In dogs with experimentally induced hwd, treatment with hydralazine had significantly greater effect on cardiac index and mean pulmonary and systemic arterial pressures and resistance than did administration of 100% oxygen. These data indicate that further study of vasodilators for treatment of hwd-induced pulmonary hypertension may be warranted.

Free access
in American Journal of Veterinary Research

SUMMARY

Hypochloremic metabolic alkalosis accompanied by hypokalemia and hyponatremia was induced experimentally in 7 adult sheep by diversion (loss) of gastric contents through an Ivan and Johnston cannula placed in the cranial part of the duodenum just distal to the pylorus. Cannula placement was easily accomplished, and cannulae were tolerated well by the sheep. Volume of effluent produced during the 60- to 120-hour period of diversion ranged from 7.7 to 14.9 L and tended to be greatest during the first 24 hours. All sheep became dehydrated, with mean pcv and plasma total protein concentration increases of 94.2 and 61.7%, respectively. Plasma chloride concentration decreased in linear fashion from a prediversion mean of 113 mEq/L (range, 111 to 117 mEq/L) to an end-point mean of 54 mEq/L (range, 45 to 65 mEq/L). Plasma sodium and potassium concentrations also decreased, though potassium concentration increased terminally. There were rapid increases in arterial blood pH and bicarbonate and base excess concentrations during the first 48 hours after diversion. However, during the final stages of diversion, sheep developed superimposed metabolic acidosis with increased plasma lactate concentration and high anion gap.

Free access
in American Journal of Veterinary Research

SUMMARY

Renal electrolyte and net acid excretion were characterized during generation and maintenance of hypochloremic metabolic alkalosis in a ruminant model. Two phases of renal response with regard to sodium and net acid excretion were documented. An initial decrease in net acid excretion was attributable to increase in bicarbonate excretion with associated increase in sodium excretion. As the metabolic disturbance became more advanced, a second phase of renal excretion was observed in which sodium and bicarbonate excretion were markedly decreased, leading to increase in net acid excretion and development of aciduria. Throughout the metabolic disturbance, chloride excretion was markedly decreased; potassium excretion also decreased. These changes were accompanied by increase in plasma renin and aldosterone concentrations. There was apparent failure to concentrate the urine optimally during the course of the metabolic disturbance, despite increasing plasma concentration of antidiuretic hormone.

Free access
in American Journal of Veterinary Research

Summary

Bradycardia was documented in 12 cattle from which food had been withheld for 48 hours in preparation for general anesthesia and an elective surgical procedure. The heart rates decreased by a mean of 14 beats/min, and 4 cows had sinus arrhythmia. To evaluate this finding, the heart rates of 21 clinically normal cattle were evaluated before and after food was withheld for 48 hours. Bradycardia developed in all of the clinically normal cattle, with the mean decrease in heart rate being 23 beats/min. Five of the clinically normal cows developed sinus arrhythmia. It was concluded that bradycardia and sinus arrhythmia in cattle are associated with deprivation of food.

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To compare serum total protein (sTP) and serum IgG (sIgG) concentrations In neonatal calves administered colostrum or a bovine serum-based colostrum replacement (CR) product followed by a bovine serum-based colostrum supplement (CS) product.

Design—Randomized controlled clinical trial.

Animals—18 Jersey and 269 Holstein neonatal heifer calves.

Procedures—141 calves were given 4 L of colostrum in 1 or 2 feedings (first or only feeding was provided ≤ 2 hours after birth; when applicable, a second feeding was provided between 2 and 12 hours after birth). Other calves (n = 146) were fed 2 L of a CR product ≤ 2 hours after birth and then 2 L of a CS product between 2 and 12 hours after birth. Concentrations of sTP and sIgG were measured 1 to 7 days after birth. Data from cohorts on individual farms and for all farms were analyzed.

Results—Mean sTP and sIgG concentrations differed significantly between feeding groups. In calves fed colostrum and calves fed CR and CS products, mean ± SD sTP concentration was 5.58 ± 0.67 g/dL and 5.26 ± 0.54 g/dL, respectively, and mean sIgG concentration was 1,868 ± 854 mg/dL and 1,320 ± 620 mg/dL, respectively. The percentage of calves that had failure of passive transfer of immunity (ie, sIgG concentrations < 1,000 mg/dL) was not significantly different between groups.

Conclusions and Clinical Relevance—Results suggested that sequential feeding of bovine serum-based CR and CS products to neonatal calves is an alternative to feeding colostrum for achieving passive transfer of immunity.

Full access
in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association

Abstract

Case Description—A 19-month-old 536.4-kg (1,180-lb) Brown Swiss heifer was referred for evaluation of a firm swelling over the distal aspect of the right metatarsal region and chronic lameness in the right hind limb.

Clinical Findings—Examination of radiographs of the right metatarsophalangeal joints revealed an expansile, smoothly marginated, cyst-like lesion within the distal metaphysis of the metatarsal III and IV bone. Differential diagnoses included bone abscess, bone cyst, aneurysmal bone cyst, neoplasia, osteomyelitis, and metabolic bone disease. Aerobic microbial culture of the aspirate yielded moderate growth of branching, gram-positive, rod-shaped bacteria, which were presumptively identified as Nocardia spp. The isolate was subsequently identified as Nocardia arthritidis by 16S rRNA gene sequence analysis.

Treatment and Outcome—The lesion was surgically debrided, lavaged, and bandaged. Exercise was restricted, and systemic and local administration of antimicrobials was instituted. After a communication between the abscess and the metatarsophalangeal joints was iatrogenically created, the extralabel use of aminoglycosides was initiated. The heifer had noticeable clinical improvement within 2 weeks after initial evaluation and reportedly had no evidence of lameness and minimal external blemishes 3 months after the second evaluation.

Clinical Relevance—To our knowledge, this is the first report on the diagnosis and management of a long-bone abscess attributable to N arthritidis infection in cattle. Complications encountered during treatment and the decision to engage in extralabel use of antimicrobial agents in the heifer described here may serve as a guide for food animal practitioners faced with the treatment of valuable cattle.

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To describe signalment; surgical findings; short-, medium-, and long-term outcome; and recurrence rate for cattle undergoing celiotomy because of jejunal hemorrhage syndrome (JHS) and to analyze risk factors associated with outcome and recurrence.

Design—Retrospective case series.

Animals—31 dairy cattle with JHS.

Procedures—Medical records were analyzed. Follow-up information was obtained from owners of cattle surviving until discharge.

Results—18 of 31 (58%) cattle undergoing celiotomy survived to initial discharge. Fifteen (48%) and 13 (42%) were alive 6 and 12 months after discharge, respectively. All 5 deaths within 12 months after discharge were attributed to JHS recurrence. Survival time was 12 to 85 months for the 13 long-term survivors. Six of 7 that died > 12 months after celiotomy did so for reasons unrelated to JHS. Recurrence rate among short-term survivors was 7 of 18; 1 of these survived long-term. A significant proportion of affected cattle were Brown Swiss, compared with proportions for other breeds. Manual massage of the bowel to break down clots was associated with a significantly higher short-term survival rate than was en-terectomy or enterotomy. Medium- and long-term survival rate was higher in cattle referred 24 to 48 hours after onset of signs. Length of obstructing blood clots was not associated with outcome. Other factors were not significantly associated with recurrence.

Conclusions and Clinical Relevance—Survival rates were higher than those in other reports. Prompt celiotomy and resolution by use of manual massage were associated with higher survival rates. In this population, JHS recurred in 7 of 18 short-term survivors.

Full access
in Journal of the American Veterinary Medical Association