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.
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)
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.
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.
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.
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.
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
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.
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.
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.
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
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
Objective—To determine the pharmacokinetics of
azithromycin and its concentration in body fluids and
bronchoalveolar lavage cells in foals.
Animals—6 healthy 6- to 10-week-old foals.
Procedure—Azithromycin (10 mg/kg of body weight)
was administered to each foal via IV and intragastric
(IG) routes in a crossover design. After the first IG
dose, 4 additional IG doses were administered at 24-hour intervals. A microbiologic assay was used to
measure azithromycin concentrations in serum, peritoneal
fluid, synovial fluid, pulmonary epithelial lining
fluid (PELF), and bronchoalveolar (BAL) cells.
Results—Azithromycin elimination half-life was 20.3
hours, body clearance was 10.4 ml/min·kg, and apparent
volume of distribution at steady state was 18.6
L/kg. After IG administration, time to peak serum concentration
was 1.8 hours and bioavailability was 56%.
After repeated IG administration, peak serum concentration
was 0.63 ± 0.10 µg/ml. Peritoneal and synovial
fluid concentrations were similar to serum concentrations.
Bronchoalveolar cell and PELF concentrations
were 15- to 170-fold and 1- to 16-fold higher than concurrent
serum concentrations, respectively. No
adverse reactions were detected after repeated IG
Conclusions and Clinical Relevance—On the basis
of pharmacokinetic values, minimum inhibitory concentrations
of Rhodococcus equi isolates, and drug
concentrations in PELF and bronchoalveolar cells, a
single daily oral dose of 10 mg/kg may be appropriate
for treatment of R equi infections in foals. Persistence
of high azithromycin concentrations in PELF and bronchoalveolar
cells 48 hours after discontinuation of
administration suggests that after 5 daily doses, oral
administration at 48-hour intervals may be adequate.
(Am J Vet Res 2001;62:1870–1875)