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SUMMARY

Objective

To evaluate the effect of pentoxifylline on response of horses to in vivo challenge exposure with endotoxin.

Animals

24 healthy horses in 3 treatment groups: pentoxifylline, endotoxin, or endotoxin and pentoxifylline.

Procedure

Horses of the pentoxifylline group were given a bolus of pentoxifylline (7.5 mg/kg of body weight, IV), followed by an infusion (3 mg/kg/h) over 3 hours, and those of the endotoxin group were given 20 ng of endotoxin/kg IV over 30 minutes. Those of the combination group were given both of the aforementioned compounds; pentoxifylline was administered immediately after endotoxin. Clinical (rectal temperature, heart and respiratory rates, blood pressure) and hematologic (WBC count; whole blood recalcification time; plasma fibrinogen, thromboxane B2, and 6-keto-prostaglandin F, concentrations; plasma plasminogen activator inhibitor activity; and serum tumor necrosis factor and interleukin 6 activities) variables were evaluated over 24 hours.

Results

Compared with baseline values, there were no significant changes in any variable over time in the horses receiving only pentoxifylline, with the exception of a significant increase in WBC count. Rectal temperature, heart rate, mean blood pressure, WBC count, whole blood recalcification time, fibrinogen concentration, plasminogen activator inhibitor activity, tumor necrosis factor and interleukin 6 activities, and plasma thromboxane B2 concentration changed significantly over time in horses of the endotoxin and endotoxin-pentoxifylline combination groups. Respiratory rate and plasma 6-keto-prostaglandin F concentration changed significantly over time only in horses of the endotoxin group. Compared with values for the endotoxin group, rectal temperature and respiratory rate were significantly lower, and whole blood recalcification time was longer for the endotoxin/pentoxifylline group.

Conclusion

Beneficial effects of pentoxifylline are limited when it is administered IV to horses after in vivo challenge exposure with endotoxin. (Am J Vet Res 1997;58:1300–1307)

Free access
in American Journal of Veterinary Research

SUMMARY

Objective

To compare effects of a single dose of pentoxifylline (PTX), flunixin meglumine (FM), and their combination (FM/PTX) in a model of equine endotoxemia.

Animals

24 healthy horses, aged 2 to 15 years.

Procedure

4 groups (n = 6/group) received 30 ng of Escherichia coli O55:B5 endotoxin/kg of body weight, IV, over 30 minutes, and 1 of the following preparations 15 minutes before and 8 hours after endotoxin infusion: FM, 1.1 mg/kg; PTX, 8 mg/kg; FM/PTX, 1.1 mg of FM and 8 mg of PTX/kg; and saline solution bolus (ENDO). Clinical and hematologic variables were measured over 24 hours.

Results

Compared with ENDO, FM given before endotoxin significantly reduced TxB2, and 6-keto-PGF1 concentrations, pulse, rectal temperature, and attitude score. Pentoxifylline given before endotoxin resulted in significantly higher 6-keto-PGF1 concentration at 1.5 hours and significantly lower PAI-1 activity at 12 hours. Tumor necrosis factor and IL-6 activities in horses given PTX alone were not significantly different from values in those given the saline bolus. FM/PTX induced effects similar to those of FM alone on endotoxin-induced changes in temperature and TxB2 concentration, and 6-keto-PGF1 concentration was significantly lower than that in horses of the ENDO group at 1 hour. In horses of the FM group, 6-keto-PGF1 concentration was significantly lower than that in horses of the ENDO group, from 0.5 hour to 2 hours. Horses of the FM and FM/PTX groups had significantly higher IL-6 activity at 1.5 and 2 hours than did horses of the PTX and ENDO groups; those of the FM and FM/PTX groups had significantly lower WBC count than did those of the PTX and ENDO groups.

Conclusions

FM/PTX may help offset deleterious hemodynamic effects of endotoxin more effectively than does either FM or PTX alone. (Am J Vet Res 1997;58:1291–1299)

Free access
in American Journal of Veterinary Research

Abstract

OBJECTIVE

To investigate pseudohyperkalemia occurring in horses experiencing rhabdomyolysis when serum chemistry profiles are run on an VetScan VS2 analyzer (Abaxis).

ANIMALS

18 horses with rhabdomyolysis (creatine kinase [CK] > 1,000 U/L).

METHODS

In 3 horses with serum CK activities > 5,800 U/L and persistent serum potassium concentrations of > 8.5 mmol/L (VetScan VS2), potassium concentrations were reevaluated with either i-STAT Alinity Base Station (Abbott), Catalyst (Idexx), or Cobas c501 (Roche) ion-specific analyzers. Paired serum samples from 15 additional horses (median serum CK activity, 7,601 U/L; range, 1,134 to 192,447 U/L) were analyzed on both VetScan VS2 and Cobas c501 machines. Serum potassium concentrations were compared between the VetScan VS2 and ion-specific analyzers by Bland-Altman and Wilcoxon ranked tests and correlated to log10 CK activity via Pearson correlation.

RESULTS

Serum potassium concentrations were significantly higher on the VetScan VS2 (6.7 ± 1.6 mmol/L) versus the ion-specific analyzers (4.0 ± 1.1 mmol/L; P < .0001), with high bias shown in Bland-Altman analysis (43.1 ± 27.9). Potassium concentrations positively correlated with log10 CK activity with the VetScan VS2 (R2 = 0.51; P = .003) but not the Cobas (R2 = 0.09; P = .3) analyzer.

CLINICAL RELEVANCE

An alternate analyzer to the VetScan VS2 should be used to evaluate serum potassium concentrations in horses with rhabdomyolysis because the VetScan VS2 methodology uses lactate dehydrogenase, which increases in serum with rhabdomyolysis and falsely elevates potassium concentrations.

Open access
in Journal of the American Veterinary Medical Association