Search Results

Abstract

Objective—To determine and compare sensitivity, specificity, accuracy, and predictive values of measurement of serum total protein concentration by refractometry as well as 5 commercially available kits for the diagnosis of failure of passive transfer (FPT) of immunity in foals.

Design—Prospective study.

Animals—65 foals with various medical problems and 35 clinically normal foals.

Procedure—IgG concentration in serum was assessed by use of zinc sulfate turbidity (assay C), glutaraldehyde coagulation (assay D), 2 semiquantitative immunoassays (assays F and G), and a quantitative immunoassay (assay H). Serum total protein concentration was assessed by refractometry. Radial immunodiffusion (assays A and B) was used as the reference method.

Results—For detection of IgG < 400 mg/dL, sensitivity of assay H (100%) was not significantly different from that of assays C, E, and G (88.9%). Specificity of assays H (96.0%) and G (95.8%) was significantly higher than that of assays C (79.4%) and E (78.1%). For detection of IgG < 800 mg/dL, sensitivities of assays H (97.6%), D (92.9%), C (81.0%), and G (81.0%) were significantly higher than that of assay F (52.4%). Specificity of assays F (100%), G (94.7%), and H (82.8%) was significantly higher than that of assays C (56.9%) and D (58.6%). Serum total protein concentration ≤ 4.5 g/dL was suggestive of FPT, whereas values ≥ 6.0 g/dL indicated adequate IgG concentrations.

Conclusions and Clinical Relevance—Most assays were adequate as initial screening tests. However, their use as a definitive test would result in unnecessary treatment of foals with adequate IgG concentrations. (J Am Vet Med Assoc 2005;227:1640–1645)

Abstract

Objective—To compare cardiac output (CO) measured by use of the partial carbon dioxide rebreathing method (NICO) or lithium dilution method (LiDCO) in anesthetized foals.

Sample Population—Data reported in 2 other studies for 18 neonatal foals that weighed 32 to 61 kg.

Procedures—Foals were anesthetized and instrumented to measure direct blood pressure, heart rate, arterial blood gases, end-tidal isoflurane and carbon dioxide concentrations, and CO. Various COs were achieved by administration of dobutamine, norepinephrine, vasopressin, phenylephrine, and isoflurane to allow comparisons between LiDCO and NICO methods. Measurements were obtained in duplicate or triplicate. We allowed 2 minutes between measurements for LiDCO and 3 minutes for NICO after achieving a stable hemodynamic plane for at least 10 to 15 minutes at each CO.

Results—217 comparisons were made. Correlation (r = 0.77) was good between the 2 methods for all determinations. Mean ± SD measurements of cardiac index for all comparisons with the LiDCO and NICO methods were 138 ± 62 mL/kg/min (range, 40 to 381 mL/kg/min) and 154 ± 55 mL/kg/min (range, 54 to 358 mL/kg/min), respectively. Mean difference (bias) between LiDCO and NICO measurements was −17.3 mL/kg/min with a precision (1.96 × SD) of 114 mL/kg/min (range, −131.3 to 96.7). Mean of the differences of LiDCO and NICO measurements was 4.37 + (0.87 × NICO value).

Conclusions and Clinical Relevance—The NICO method is a viable, noninvasive method for determination of CO in neonatal foals with normal respiratory function. It compares well with the more invasive LiDCO method.

Abstract

Objective—To determine the effects of dobutamine, norepinephrine, and vasopressin on cardiovascular function and gastric mucosal perfusion in anesthetized foals during isoflurane-induced hypotension.

Animals—6 foals that were 1 to 5 days of age.

Procedures—6 foals received 3 vasoactive drugs with at least 24 hours between treatments. Treatments consisted of dobutamine (4 and 8 μg/kg/min), norepinephrine (0.3 and 1.0 μg/kg/min), and vasopressin (0.3 and 1.0 mU/kg/min) administered IV. Foals were maintained at a steady hypotensive state induced by a deep level of isoflurane anesthesia for 30 minutes, and baseline cardiorespiratory variables were recorded. Vasoactive drugs were administered at the low infusion rate for 15 minutes, and cardiorespiratory variables were recorded. Drugs were then administered at the high infusion rate for 15 minutes, and cardiorespiratory variables were recorded a third time. Gastric mucosal perfusion was measured by tonometry at the same time points.

Results—Dobutamine and norepinephrine administration improved cardiac index. Vascular resistance was increased by norepinephrine and vasopressin administration but decreased by dobutamine at the high infusion rate. Blood pressure was increased by all treatments but was significantly higher during the high infusion rate of norepinephrine. Oxygen delivery was significantly increased by norepinephrine and dobutamine administration; O₂ consumption decreased with dobutamine. The O₂ extraction ratio was decreased following norepinephrine and dobutamine treatments. The gastric to arterial CO₂gap was significantly increased during administration of vasopressin at the high infusion rate.

Conclusion and Clinical Relevance—Norepinephrine and dobutamine are better alternatives than vasopressin for restoring cardiovascular function and maintaining splanchnic circulation during isofluraneinduced hypotension in neonatal foals.

Abstract

Objective—To determine pharmacokinetics of clarithromycin and concentrations in body fluids and bronchoalveolar (BAL) cells of foals.

Animals—6 healthy 2-to 3-week-old foals.

Procedures—In a crossover design, clarithromycin (7.5 mg/kg) was administered to each foal via IV and intragastric (IG) routes. After the initial IG administration, 5 additional doses were administered IG at 12-hour intervals. Concentrations of clarithromycin and its 14-hydroxy metabolite were measured in serum by use of high-performance liquid chromatography. A microbiologic assay was used to measure clarithromycin activity in serum, urine, peritoneal fluid, synovial fluid, CSF, pulmonary epithelial lining fluid (PELF), and BAL cells.

Results—After IV administration, elimination half-life (5.4 hours) and mean ± SD body clearance (1.27 ± 0.25 L/h/kg) and apparent volume of distribution at steady state (10.4 ± 2.1 L/kg) were determined for clarithromycin. The metabolite was detected in all 6 foals by 1 hour after clarithromycin administration. Oral bioavailability of clarithromycin was 57.3 ± 12.0%. Maximum serum concentration of clarithromycin after multiple IG administrations was 0.88 ± 0.19 μg/mL. After IG administration of multiple doses, clarithromycin concentrations in peritoneal fluid, CSF, and synovial fluid were similar to or lower than concentrations in serum, whereas concentrations in urine, PELF, and BAL cells were significantly higher than concentrations in serum.

Conclusions and Clinical Relevance—Oral administration of clarithromycin at 7.5 mg/kg every 12 hours maintains concentrations in serum, PELF, and BAL cells that are higher than the minimum inhibitory concentration (0.12 μg/mL) for Rhodococcus equiisolates for the entire 12-hour dosing interval.

Abstract

Objective—To identify factors associated with short-term survival in bacteremic neonatal foals, evaluate the racing performance of Thoroughbred survivors, and evaluate changes in causative organisms and their antimicrobial susceptibility.

Design—Retrospective case series.

Animals—423 bacteremic foals.

Procedures—Medical records of foals that were hospitalized in 1982 through 2007 were reviewed, and those with bacteremia were included in the study. Data retrieved included signalment, physical examination and clinicopathologic findings at admission, localized infections, concurrent illnesses, duration of hospitalization, and outcome (survival to discharge from the hospital vs nonsurvival). The number, identity, and antimicrobial susceptibility of organisms isolated from blood samples were also obtained. Racing records for surviving Thoroughbred foals and maternal siblings were examined.

Results—Of 423 bacteremic foals, 254 survived. Odds of survival were negatively associated with age at admission, septic arthritis, band neutrophil count, and serum creatinine concentration and positively associated with year of admission, diarrhea, rectal temperature, neutrophil count, and arterial blood pH. Overall, microbial culture of blood samples yielded 554 isolates; Escherichia coli was consistently isolated most frequently. Percentage of isolates susceptible to enrofloxacin, but no other antimicrobial, decreased over time. Surviving Thoroughbred foals did not differ from siblings with regard to percentage of starters, percentage of winners, or number of starts; however, surviving foals had significantly fewer wins and total earnings.

Conclusions and Clinical Relevance—During the study period, microbial resistance to antimicrobials commonly used to treat bacteremic foals did not develop. Surviving bacteremic Thoroughbred foals were as likely to start races as their siblings but earned less money.

Abstract

Objective—To compare the diagnostic performance of a point-of-care (POC) analyzer with that of established methods for the measurement of plasma IgG, total protein, and albumin concentrations in neonatal foals.

Design—Evaluation study.

Animals—100 neonatal foals < 7 days of age.

Procedures—Plasma IgG, total protein, and albumin concentrations were measured with a POC analyzer via an immunoturbidimetric method. Corresponding measurements of plasma IgG, total protein, and albumin concentrations were measured by means of automated biochemical analyzers via automated immunoturbidimetric, biuret, and bromocresol green dye–binding assays, respectively (standard laboratory methods).

Results—The sensitivity and specificity of the POC analyzer for detection of failure of passive transfer of immunity (FPTI) in foals were 80.7% and 100%, respectively, when FPTI was defined as a plasma IgG concentration < 400 mg/dL and were 75.9% and 100%, respectively, when FPTI was defined as a plasma IgG concentration < 800 mg/dL. The POC analyzer overestimated plasma albumin concentrations and, to a lesser extent, plasma total protein concentrations, compared with values determined with the standard laboratory methods.

Conclusions and Clinical Relevance—Results suggested the POC analyzer was acceptable for determination of plasma IgG and total protein concentrations in ill foals. The POC analyzer overestimated plasma albumin concentration such that its use was clinically unacceptable for the determination of that concentration. The POC analyzer provided timely measurements of plasma IgG concentrations, which is necessary information for the assessment of passive transfer of maternal antibodies to neonatal foals.

Abstract

Objective—To compare the outcome of horses with nephrosplenic entrapment of the large colon (NSELC) that were treated nonsurgically by IV administration of phenylephrine and exercise with that of horses treated by IV administration of phenylephrine and a rolling procedure under general anesthesia.

Design—Retrospective case series.

Animals—88 horses with NSELC.

Procedures—Horses examined between 2004 and 2010 because of acute abdominal pain that had NSELC on the basis of findings on abdominal palpation per rectum, abdominal ultrasonography, or both were included. Medical records were reviewed to obtain information on treatment (IV administration of phenylephrine and exercise vs IV administration of phenylephrine and a rolling procedure) and outcome.

Results—Overall, 85% (75/88) of horses with NSELC responded to exercise or rolling under general anesthesia. The success rate of rolling under general anesthesia (42/50 [84%]) was significantly higher than the success rate of exercise after IV administration of phenylephrine (24/38 [63.2%]). Resolution of NSELC was achieved by rolling under general anesthesia in 8 of 14 horses that initially failed to resolve with exercise.

Conclusions and Clinical Relevance—A rolling procedure performed under general anesthesia had a higher success rate than exercise after IV phenylephrine administration for resolution of NSELC in horses, suggesting that rolling could be considered as the initial medical treatment. The rolling procedure may be labor intensive and should only be attempted in a surgical facility in the event that exploratory laparotomy is required

Abstract

Objective—To determine efficacy of a commercially available hyperimmune plasma product for prevention of naturally acquired pneumonia caused by Rhodococcus equiin foals.

Design—Randomized clinical trial.

Animals—165 foals.

Procedure—Foals were randomly assigned to 1 of 2 groups (hyperimmune plasma or nontreated controls). Foals with failure of passive transfer (FPT) of immunity were treated with hyperimmune plasma and evaluated as a third group. Foals that received plasma were given 950 ml between 1 and 10 days of age and between 30 and 50 days of age. A tracheobronchial aspirate was obtained from foals with clinical signs of respiratory tract disease for bacteriologic culture.

Results—A significant difference in incidence of pneumonia caused by R equi in foals with adequate passive transfer was not detected between foals that received plasma (19.1%) and nontreated foals (30%). Of 13 foals without FPT that received plasma and developed pneumonia caused by R equi, 12 developed disease prior to administration of the second dose of hyperimmune plasma. Incidence of undifferentiated pneumonia of all causes was not different between groups.

Conclusion and Clinical Relevance—Intravenous administration of the commercially available hyperimmune plasma was safe, and the product contained high concentrations of anti-R equi antibodies. However, within this limited foal population, the difference in incidence of pneumonia caused by R equi observed between foals that received plasma and control foals was not significant. (J Am Vet Med Assoc 2002;220:59–63)

Abstract

Objective—To evaluate WBC concentration, plasma fibrinogen concentration, and an agar gel immunodiffusion (AGID) test for early identification of Rhodococcus equi-infected foals.

Design—Prospective study.

Animals—162 foals from a farm with enzootic R equi infection.

Procedure—Blood samples were obtained from each foal at 4-week intervals for measurement of WBC and plasma fibrinogen concentrations and at 2-week intervals for detection of anti-R equi antibody by an AGID assay. Diagnostic performance of WBC and fibrinogen concentrations was assessed by use of receiver operating characteristic curve analysis. For each assay, sensitivity, specificity, and predictive values were calculated at various cutoff points; bacteriologic culture of R equi from a tracheobronchial aspirate was used as the reference standard test.

Results—Diagnostic performance of WBC concentration was significantly higher than that of fibrinogen concentration. Sensitivity and specificity of measurement of WBC concentration at a cutoff of 13,000 cells/µL were 95.2 and 61.2%, respectively; at a cutoff of 15,000 cells/µL, sensitivity was 78.6% and specificity was 90.8%. When a positive test result was used as the cutoff, sensitivity of the AGID assay was 62.5% and specificity was 53.8%.

Conclusion and Clinical Relevance—Monitoring WBC concentration is a useful approach for early detection of infected foals on farms with a high prevalence of R equi pneumonia. In contrast, serologic surveillance by use of an AGID assay is of little benefit for that purpose. (J Am Vet Med Assoc 2003;222:775–781)