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Abstract

Objective

To examine temporal patterns of core body temperatures in adult horses during general anesthesia and to determine the efficacy of forced-air warming blankets in attenuating decreases in core body temperatures.

Animals

5 clinically normal adult horses.

Procedure

Horses were assigned to each of 2 trials, warmer and no-warmer, in a randomized crossover design. Horses were instrumented with a thermistor-tipped pulmonary arterial catheter to measure core body temperature. Induction and maintenance of and recovery from general anesthesia were performed in an air-conditioned surgical suite where room temperature and relative humidity were maintained at approximately 21 C and 40%, respectively. Core body temperature measurements were recorded every 5 minutes during 2.5 hours of anesthesia and during recovery until horses could stand. Data were analyzed, using ANOVA for repeated measures.

Results

Without warming, mean core body temperature decreased steadily (0.37 ± 0.18 C/h). Forced-air warming significantly decreased that rate to 0.19 ± 0.09 C/h. In both trials, there was an additional, rapid, significant decrease in core body temperature when horses were moved to the recovery area, which was apparently the result of conductive heat loss to the cold floor. Recovery time and time required for core body temperature to return to baseline were unaffected by forced-air warming during anesthesia and recovery.

Conclusions and Clinical Relevance

Core body temperature decreases steadily in adult horses anesthetized in a cool, dry environment. Forced-air warming devices can attenuate this decrease. Additional body heat can be lost rapidly when anesthetized horses are positioned on cold surfaces during recovery. (Am J Vet Res 1999;60:556–562)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To examine temporal patterns of rectal, nasal, groin, and skin temperatures measured in adult horses undergoing general anesthesia and to determine accuracy and precision of temperatures at these sites, compared with core temperature.

Animals

5 healthy adult horses.

Procedure

Induction, maintenance of, and recovery from general anesthesia were performed in an air-conditioned surgical suite. Room temperature and relative humidity were approximately 21 C and 40%, respectively. Anesthesia was maintained for 2.5 hours, and body temperatures were measured and recorded every 5 minutes. Mean values were compared by use of ANOVA for repeated measures. Correlation coefficients for linear regressions of site temperature versus core temperature at 30-minute intervals were used to evaluate precision.

Results

Rectal temperature decreased in a linear manner, similar to core temperature. Nasal, groin, and skin temperatures followed a biphasic pattern; they sharply increased initially, peaked, then decreased at a rate similar to that of core temperatures. Rectal temperature always accurately reflected core temperature. Initial significant differences between core temperature and nasal, groin, or skin temperature disappeared as peripheral site temperatures approached peak values. Precision of core temperature estimation was generally poor for rectal, groin, and skin temperatures but was high (r > 0.90) after the first hour of anesthesia.

Conclusion

Anesthesia-induced core heat redistribution develops with minimal effect on core temperature. Rectal temperature can accurately reflect core temperature. (Am J Vet Res 1999;60:648–651)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To evaluate the accuracy of 3 automated methods of determining Hct and hemoglobin (Hb) concentration, compared with manual methods.

Animals

22 clinically normal adult horses of various breeds.

Procedure

A blood sample was obtained from each horse. Six dilutions (representing Hct of 0, 10, 20, 40, 60, or 70%) were prepared from each sample and analyzed, using 1 of 2 blood gas analyzers or a hemoximeter (for automated determinations) or the Wintrobe macrohematocrit and cyanmethemoglobin methods (for manual determinations). Regression analysis was used to determine mean slope relationships between Hct and Hb measurements obtained by use of manual versus automated methods. Slopes were compared, using Student's t-test.

Results

Of the 3 automated methods examined, only 1 blood gas analyzer reported Hct and Hb values that were not significantly different from those determined by use of manual methods; however, this analyzer could not report Hb concentrations below 2.5 g/dl. The other blood gas analyzer reported values for Hct and Hb concentrations that were consistently higher than those obtained by use of manual methods at Hct ≤ 20% and Hb ≤ 6.6 g/dl. The hemoximeter yielded more accurate results if the Hb concentration was between 6.6 and 20 g/dl.

Conclusion

Although there were some limitations in measuring at low Hb concentrations, the method of determining Hb concentration and Hct with blood gas analyzer 2 was more accurate than that with blood gas analyzer 1 (Hct and Hb concentration) or the hemoximeter (Hb only). (Am J Vet Res 1998; 59:1519-1522)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To evaluate the oncotic, hemodilutional, and hemostatic effects of IV infusions of a large volume of isotonic saline solution and 2 doses of 6% hydroxyethyl starch (HES) in clinically normal ponies.

Animals

12 adult ponies.

Procedure

Ponies were assigned to 3 treatment groups and received the following IV infusions: 80 ml of 0.9% sodium chloride/kg; 10 ml of 6% HES (in 0.9% sodium chloride)/kg; or 20 ml of 6% HES (in 0.9% sodium chloride)/kg. Blood samples were collected for determination of colloid oncotic pressure (COP), PCV, plasma total protein concentration, platelet count, von Willebrand factor antigen (vWf:Ag) activity, fibrinogen concentration, prothrombin time, activated partial thromboplastin time (APTT), and factor VIII coagulant (FVIII:C) activity. A rocket immunoelectrophoretic procedure was used for determination of vWf:Ag activity. A modification of the APTT assay was used for determination of FVIII:C activity. Cutaneous bleeding time was determined, using a template method.

Results

Mean COP was persistently increased over baseline values in the face of hemodilution in HES-treated ponies. Prothrombin time, APTT, and fibrinogen concentrations decreased after infusions and vWf:Ag and FVIII:C activities were decreased in dosedependent manner in HES-treated ponies. Though cutaneous bleeding time was not significantly affected in ponies of any group, a trend toward prolongation of bleeding time was evident in ponies receiving 20 ml of HES/kg. This trend appeared to be associated with marked decrement in vWf:Ag activity at this dosage.

Conclusions and Clinical Relevance

Infusion of HES in clinically normal ponies increases COP, and exerts dose-dependent hemodilutional effects and dose-dependent effects on specific hemostatic variables. Thus, HES may be useful for resuscitative fluid treatment of horses. (Am J Vet Res 1997;58:541–548)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine the effects of endotracheal intubation on respiratory mechanics during xylazine sedation and xylazine-diazepam-ketamine anesthesia in adult horses.

Animals

5 healthy adult horses.

Procedure

Measurements were derived from recordings of respiratory gas flow, and transpulmonary and transtracheal pressures. Total pulmonary resistance (RT) was partitioned into upper airway resistance (extrathoracic portion of trachea, larynx, pharynx, nasal cavity, nares; RUA) and lower airway resistance (intrathoracic portion of trachea, bronchi, bronchioles). Baseline measurements were obtained in unsedated horses, after xylazine administration, and following nasotracheal intubation (ID, 18 mm). Measurements were obtained following induction of xylazine-diazepam-ketamine anesthesia and subsequent to endotracheal intubations (ID, 22, 20, and 16 mm). During recovery, horses were nasotracheally intubated (ID, 18 mm). Measurements were obtained upon standing, and repeated after extubation. Data were examined by use of ANOVA with repeated measures.

Results

Significant increases in mean work of breathing (W), RT, and RUA observed with xylazine sedation were variably attenuated by nasotracheal intubation. During xylazine-diazepam-ketamine anesthesia, the highest mean values for W, RT, RUA, transpulmonary and transtracheal pressures developed during nonintubation periods. The magnitudes of resistance and pressure values were inversely proportional to the internal diameter of the endotracheal tube. At recovery, values of the W and all measurements of resistances and pressures were significantly increased, compared with presedation values. Extubation resulted in further increases in these measurements.

Conclusions

Work of breathing in horses is substantially increased when RUA is increased during xylazine sedation and xylazine-diazepam-ketamine anesthesia. Endotracheal intubation reduces W by reducing RUA. (Am J Vet Res 1997;58:641–646)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether use of electrostimuluated acupuncture (ESA) would result in significant improvements in ground reaction forces and lameness scores in dogs with chronic elbow joint osteoarthritis secondary to elbow joint dysplasia.

Design—Randomized, controlled, crossover clinical trial.

Animals—9 dogs with chronic forelimb lameness and radiographic evidence of elbow joint osteoarthritis.

Procedures—All dogs had a 3-week control acclimation period during which gait analysis was performed weekly. Dogs then received ESA once weekly for 3 weeks followed by a sham treatment once weekly for 3 weeks or received the sham treatment followed by ESA. Gait analysis was repeated prior to each treatment, and owners were asked to provide pain scores by use of a visual analog scale method.

Results—Treatment (control, acupuncture, or sham) did not have a significant effect on ground reaction forces for any limb. Owners of 8 of the 9 dogs were able to correctly guess the time period when ESA was delivered.

Conclusions and Clinical Relevance—Results suggested that ESA did not have any significant effects on severity of lameness, as determined by measurement of ground reaction forces, or severity of pain, as determined by visual analog scale pain scores, in dogs with chronic elbow joint osteoarthritis secondary to elbow joint dysplasia.

Full access
in Journal of the American Veterinary Medical Association