Objective: To determine whether body lean angle could be predicted from circle radius and speed in horses during lunging and whether an increase in that angle would decrease the degree of movement symmetry (MS). Animals: 11 medium- to high-level dressage horses in competition training. Procedures: Body lean angle, head MS, and trunk MS were quantified during trotting while horses were instrumented with a 5-sensor global positioning system–enhanced inertial sensor system and lunged on a soft surface. Speed and circle radius were varied and used to calculate predicted body lean angle. Agreement between observed and predicted values was assessed, and the association between lean angle and MS was determined via least squares linear regression. Results: 162 trials totaling 3,368 strides (mean, 21 strides/trial) representing trotting speeds of 1.5 to 4.7 m/s and circle radii of 1.8 to 11.2 m were conducted in both lunging directions. Differences between observed and predicted lean angles were small (mean ± SD difference, −1.2 ± 2.4°) but significantly greater for circling to the right versus left. Movement symmetry values had a larger spread for the head than for the pelvis, and values of all but 1 MS variable changed with body lean angle. Conclusions and Clinical Relevance: Body lean angle agreed well with predictions from gravitational and centripetal forces, but differences observed between lunging directions emphasize the need to investigate other factors that might influence this variable. For a fair comparison of MS between directions, body lean angle needs to be controlled for or corrected with the regression equations. Whether the regression equations need to be adapted for lame horses requires additional investigation.

Objective: To determine the effects of exercise on the distribution and pharmacokinetics of technetium Tc 99m medronate (99mTc-MDP) following intra-articular (IA) injection in horses. Animals: 5 horses. Procedures: 1 antebrachiocarpal joint (ACJ)/horse was assigned to the exercised group (n = 5), and the contralateral ACJ was evaluated in the nonexercised group (5) after a minimum washout period of 7 days. Following IA injection of 99mTc-MDP (148 MBq), blood and scintigraphic images of the carpus were obtained at 5, 10, 15, 20, 25, 30, 45, 60, 90, 120, 240, 360, 480, 600, 720, and 1,440 minutes. Plasma and scintigraphic radioactivity were determined over time, and pharmacokinetic parameters were generated via noncompartmental and compartmental analyses. Each horse was monitored via physical and lameness examination and ACJ synovial fluid analysis before injection and at days 1, 2, 3, and 7. Results: Lameness was not observed. Mean ± SD synovial fluid WBC count increased at day 1 (exercised, 721 ± 234 cells/μL; nonexercised, 948 ± 223 cells/μL), but returned to baseline at days 3 and 7 Mean time to maximum plasma radioactivity was earlier in the exercised group (16.00 ± 2.35 minutes) than the nonexercised group (43.75 ± 3.64 minutes). Linear regression of the scintigraphic radioactivity-time curves revealed a greater negative slope in the exercised group within the first 25 minutes. There was no difference in absorption or elimination rate constants in a 2-compartment model. Conclusions and Clinical Relevance: IA injection of 99mTc-MDP was safe and effective for evaluating synovial solute distribution. Exercise significantly increased early transfer of 99mTc-MDP from the ACJ into plasma, although absorption and elimination rate constants were not affected. Exercise may affect synovial clearance and withdrawal times of medications administered IA.

The effects of 2 different continuous rate infusions (CRIs) of medetomidine over an 8-hour period on sedation score, selected cardiopulmonary parameters, and serum levels of medetomidine were evaluated in 6 healthy, conscious dogs using a crossover study design. The treatment groups were: CONTROL = saline bolus followed by saline CRI; MED1 = 2 μg/kg body weight (BW) medetomidine loading dose followed by 1 μg/kg BW per hour CRI; and MED2 = 4 μg/kg BW medetomidine loading dose followed by 2 μg/kg BW per hour CRI. Sedation score (SS), heart rate (HR), respiratory rate (RR), temperature (TEMP), systolic arterial pressure (SAP), mean arterial pressure (MAP), and diastolic arterial pressure (DAP), arterial and mixed venous blood gas analyses, lactate, and plasma levels of medetomidine were evaluated at baseline, at various intervals during the infusion, and 2 h after terminating the infusion. Statistical analysis involved a repeated measures linear model. Both infusion rates of medetomidine-induced dose-dependent increases in SS and dose-dependent decreases in HR, SAP, MAP, and DAP were measured. Respiratory rate (RR), TEMP, central venous pH, central venous oxygen tension, and oxygen extraction ratio also decreased significantly in the MED2 group at certain time points. Arterial oxygen and carbon dioxide tensions were not significantly affected by either infusion rate. In healthy dogs, both infusion rates of medetomidine-induced clinically relevant sedative effects, accompanied by typical alpha2 agonist-induced hemodynamic effects, which plateaued during the infusion and subsequently returned to baseline. While additional studies in unhealthy animals are required, the results presented here suggest that medetomidine infusions at the doses studied may be useful in canine patients requiring sedation for extended periods.

Objective: To evaluate the use of the oxygen content–based index, Fshunt, as an indicator of venous admixture (Qs/Qt) at various fractions of inspired oxygen (Fio2s) in anesthetized sheep undergoing Flung or 2-lung ventilation. Animals: 6 healthy adult female sheep. Procedures: Sheep were anesthetized and administered 5 different Fio2s (0.21, 0.40, 0.60, 0.80, and 1.00) in random order during 2-lung mechanical ventilation. Arterial and mixed venous blood samples were obtained at each Fio2 after a 15-minute stabilization period. Vital capacity alveolar recruitment maneuvers were performed after blood collection. The previously used Fio2 sequence was reversed for sample collection during Flung ventilation. Blood samples were analyzed for arterial, pulmonary end-capillary, and mixed venous oxygen content and partial pressure and for hemoglobin concentration. Oxygen hemoglobin saturation, Qs/Qt, Fshunt, and oxygen tension–based indices (OTIs; including Pao2:Fio2, alveolar-arterial difference in partial pressure of oxygen [Pao2 – Pao2], [Pao2 – Pao2]:Fio2, [Pao2 – Pao2]:Pao2, and Pao2:Pao2) were calculated at each Fio2; associations were evaluated with linear regression analysis, concordance, and correlation tests. Intermethod agreement between Qs/Qt and Fshunt was tested via Bland-Altman analysis. Results: Strong and significant associations and substantial agreement were detected between Fshunt and Qs/Qt. Relationships between OTIs and Qs/Qt varied, but overall correlations were weak. Conclusions and Clinical Relevance: Whereas OTIs were generally poor indicators of Qs/Qt, Fshunt was a good indicator of Qs/Qt at various Fio2s, regardless of the magnitude of Qs/Qt and could be potentially used as a surrogate for Qs/Qt measurements in healthy sheep.