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SUMMARY

Intracranial pressure (icp) and cerebral perfusion pressure (cpp) were determined in 8 clinically normal neonatal foals. After the foals oriented themselves and nursed the mares, they were sedated as necessary, and local anesthesia was provided for making the skin incisions. Using a technique similar to that used in human beings, an indwelling subdural catheter was placed to measure icp. Carotid artery catheterization was used to measure arterial blood pressure. Cerebral perfusion pressure was calculated as the difference between mean arterial blood pressure and icp.

Intracranial pressure and cpp readings were taken twice during each 24-hour period, starting at 6 hours of age and continuing through 72 hours of age. Mean (± sd) icp were 5.83 ± 1.82, 8.81 ± 2.06, and 9.55 ± 1.55 mm of Hg (range, 2 to 15 mm of Hg), and mean cpp were 80.19 ± 10.34, 75.30 ± 10.86, and 76.80 ± 12.59 mm of Hg (range, 50 to 109 mm of Hg) for each of the first three 24-hour periods after birth, respectively. All 8 foals had physical and neurologic examinations, csf analysis, and computerized axial tomography evaluations. The foals manifested normal behavior during the interval of measurements, and adverse effects of the procedure were not detected during the monitoring period. Establishment of normal values for icp and cpp are important to clinicians who have the opportunity to apply this technique for monitoring and evaluating neonatal foals with signs of cns dysfunction.

Free access
in American Journal of Veterinary Research

Summary

Polymyxin B and an antiserum against an Re mutant Salmonella typhimurium were evaluated for protective effect in an equine model of endotoxemia. Six 3- to 5-month-old foals were given endotoxin (0.25 μg/kg of body weight) iv after no pretreatment, or pretreatment with polymyxin B (6,000 U/kg, iv) or S typhimurium antiserum (1.5 ml/kg, iv). When given without pretreatment, endotoxin caused transient recumbency and increases in rectal temperature, and heart and respiratory rates. In addition, leukopenia and increases in circulating tumor necrosis factor (tnf) and interleukin 6 (il-6) activities were detected. Compared with results obtained when endotoxin was given alone, pretreatment with polymyxin B resulted in significantly (P < 0.05) lower maximal plasma tnf and il-6 activities, and significantly lower rectal temperature and respiratory rate. In contrast, compared with effects of endotoxin given without pretreatment, use of antiserum was associated with significantly (P < 0.05) higher respiratory rate, maximal plasma il-6 activity, and total tnf response (as determined by areas under curves of plasma tnf vs time). These results indicate that polymyxin B may have potential as a treatment for equine endotoxemia. Salmonella typhimurium antiserum had no positive effect in this model, and, under certain conditions, may exacerbate the actions of endotoxin.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To compare cardiac output (CO) obtained by the lithium dilution method (LiDCO) with CO calculated from the Fick principle (FickCO), in horses maximally exercising on a high-speed treadmill.

Animals—13 Thoroughbreds.

Procedures—In part 1 of the study, 5 horses performed a warm-up (walk, trot, and canter) and exercise test (walk, trot, canter, and gallop [90% to 100% maximum oxygen consumption [{O2max}]) with measurements of LiDCO and FickCO obtained simultaneously after 60 seconds at each exercise level, for a total of 7 measurements. In part 2 of the study, 8 horses performed a warm-up (walk, trot, and canter) followed by an exercise test (walk and gallop [90% to 100% O2max], repeated twice). Measurements of LiDCO and FickCO were obtained 60 seconds into the first walk and each gallop of the exercise tests, for a total of 3 measurements.

Results—Cardiac output increased significantly with increasing speeds by use of both methods. In part 1, lithium dilution significantly overestimated CO, compared with the Fick principle, during the exercise test (as both injection number and exercise intensity increased). Mean ± SD bias was 246 ± 264 mL of blood/min/kg in part 1 and 67 ± 100mLof blood/kg/min in part 2. Three injections of lithium (part 2) did not result in the same degree of overestimation of LiDCO that was observed with 7 injections (part 1).

Conclusions and Clinical Relevance—Lithium dilution may be an acceptable substitute for the Fick principle as a means to measure CO in maximally exercising client-owned horses.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether echocardiographic variables differed between successful (elite) and less successful (nonelite) Arabian endurance horses.

Animals—34 Arabian horses that competed in endurance racing.

Procedures—Horses were assigned to either an elite or nonelite group on the basis of results of a previous competition, and a standardized echocardiographic examination was performed on each horse within 1 to 4 weeks after that competition. Multivariable logistic regression with backward stepwise elimination was used to create a prediction model for the determination of horse status (elite or nonelite) as a function of the measured echocardiographic variables.

Results—The elite and nonelite groups consisted of 23 and 11 horses, respectively. One horse in the nonelite group had a frequent ventricular dysrhythmia that could have negatively affected its performance and rider's safety, whereas none of the horses in the elite group had remarkable cardiac abnormalities. The left ventricular internal diameter during systole and diastole and left ventricular mass and stroke volume were significantly greater for horses in the elite group, compared with those for horses in the nonelite group. The final logistic regression model correctly predicted the horse status for all of the horses in the elite group and 8 of 11 horses in the nonelite group.

Conclusions and Clinical Relevance—Results indicated that heart size was significantly associated with performance for Arabian endurance horses in a manner similar to findings for Thoroughbred and Standardbred racehorses in active competition.

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

Abstract

Objective—To determine prevalence of myocardial injury in horses with colic on the basis of high concentrations of cardiac troponin I (cTnI), frequency of cardiac arrhythmias within the first 24 to 48 hours after hospital admission or surgery because of colic, and associations between high cTnI concentrations and cardiac arrhythmias, clinical course, and outcome (survival to discharge from hospital vs nonsurvival [death or euthanasia]).

Design—Prospective observational study.

Animals—111 horses with colic.

Procedures—Blood was drawn at admission and 12 and 24 hours after admission if horses were treated medically or 12 and 24 hours after surgery if treated surgically. A 24-hour ambulatory ECG was recorded beginning the morning after admission in medically treated cases or after surgery and evaluated for arrhythmias. Clinical and clinicopathologic data and outcome were obtained. Associations between cTnI concentrations and other variables were determined.

Results—An abnormal cTnI concentration (≥ 0.10 ng/mL) at admission was significantly associated with the occurrence of ventricular arrhythmias, outcome, and surgical treatment.

Conclusions and Clinical Relevance—The data suggested that horses with colic and high cTnI concentrations at admission were more likely to have ventricular arrhythmias and have a less favorable prognosis for recovery. High cTnI concentrations in horses with colic were suggestive of myocardial damage.

Full access
in Journal of the American Veterinary Medical Association