Anaesthesia with ketamine/medetomidine in the rabbit: influence of route of administration and the effect of combination with butorphanol

Objective To compare the characteristics of anaesthesia induced with ketamine/medetomidine administered by the subcutaneous and intramuscular routes and to assess the effects of the addition of butorphanol to this combination. Study design Prospective randomised study. Animals Six female New Zealand White rabbits. Methods Rabbits were given one of four combinations of ketamine and medetomidine (K/M) either subcutaneously (SC) or intramuscularly (IM) on four successive occasions with a 7‐day interval between treatments. The dose combinations were; 15/0.25 mg kg^?1 SC; 15/0.25 mg kg^?1 IM; 15/0.5 mg kg^?1 SC, and 15/0.25 mg kg^?1 together with 0.4 mg kg^?1 butorphanol (K/M/B) SC. The effects of anaesthesia on arterial blood gas values and cardiovascular variables were recorded at predetermined time points. Toe and ear pinch reflexes were judged to determine the duration of surgical anaesthesia. Loss of the righting reflex was used to measure the duration of sleep time. Analyses used repeated measures analysis of variance. Results All groups lost the righting reflex and ear pinch response. Three animals in the groups that received K/M alone lost their toe pinch reflex, whereas four lost this reflex when given K/M/B. Time of onset of loss of the righting, toe and ear pinch reflexes did not differ significantly among the groups. The higher dose combination of medetomidine with ketamine and the combination of K/M/B produced a greater duration of loss of the ear pinch response than the lower dose of K/M administered by either route. No significant differences were found among the groups in the duration of loss of the toe pinch reflex. All animals developed a moderate bradycardia (mean heart rate <166 beats minute^?1) and moderate hypoxaemia (mean P_aO₂ < 6.0 kPa). Animals given butorphanol showed the greatest reduction in respiratory rate (31 ± 13 breaths minute^?1, p < 0.05) but this was not reflected in any significant differences in arterial PCO₂, PO₂ or pH among the groups. Conclusions Administration of K/M by the SC route produced equivalent effects in comparison to intramuscular administration. The addition of butorphanol increased the duration of anaesthesia, but produced a slight increase in the degree of respiratory depression. All dose rates resulted in hypoxaemia so oxygen should be administered when these combinations are used in rabbits. Clinical relevance Subcutaneous administration is both technically simpler and may cause less discomfort to the animal than IM injection, and so is preferred. The combination of K/M with butorphanol has relatively minor effects on the depth and duration of anaesthesia, so offers little advantage to the use of K/M alone.     

Retrospective Study: Incidence of transfusion reactions to commercial equine plasma

Objective – To report on the incidence of transfusion reactions to commercial equine plasma in a hospital‐based population of horses, to characterize these reactions and report on outcome. Design – Retrospective study. Setting – University teaching hospital. Animals – Client‐owned horses referred to the University of Wisconsin. Interventions – Intravenous administration of 2 commercial equine plasma products when clinically indicated. Measurements and Main Results – Medical records of 107 horses that received plasma transfusions between 2003 and 2008 were evaluated. Transfusion reactions were recorded in 6 of 107 transfusions. All individuals were administered plasma from 1 commercial source. Foals <30 days of age received a hypergammaglobulinemic product and all adults received a lower IgG concentration product. No reactions were recorded in adults. In foals (<30 d) reactions were recorded in 6 of 69 cases (8.7%), all of which occurred in neonates <7 days of age (6/62; [9.7%]). The most frequent reactions were fever (4/6), tachycardia (2/6), tachypnea (2/6), and colic (2/6). All affected foals survived the reaction. There were no statistically significant differences (P<0.05) in any of the variables examined between those foals that did and those that did not experience transfusion reactions. Conclusion – The incidence of transfusion reactions was 8.7% in foals and 0% in adult horses in our referral population. Five of 6 foals responded to medical therapy and eventually received the clinically indicated transfusion. No transfusion related mortality occurred.     

ASSESSMENT OF BARIUM IMPREGNATED POLYETHYLENE SPHERES (BIPS®) AS A MEASURE OF SOLID-PHASE GASTRIC EMPTYING IN NORMAL DOGS-COMPARISON TO SCINTIGRAPHY

Barium impregnated polyethylene spheres (BIPS) are radiopaque markers used for investigation of a variety of gastrointestinal disorders. One proposed use of the small (1.5 mm) marker is quantitative assessment of solid-phase gastric emptying, which may offer a simple, inexpensive alternative to nuclear medicine studies. In this study the rate and pattern of gastric emptying of a radiolabeled meal containing 30 small BIPS was evaluated in normal dogs by simultaneous comparison of the radiopaque marker method and a scintigraphic method. Serial scintigraphic images and radiographs were obtained for 8 hours or until 95% of the markers had left the stomach. Emptying curves were constructed and statistical analyses performed. There were significant differences in gastric emptying times and lag phase characteristics between the BIPS and scintigraphic studies. These results indicate that in normal dogs there are differences in both the rate and the pattern of solid-phase gastric emptying of a radiolabeled meal as assessed by scintigraphy and the gastric emptying of small BIPS.     

Effect of three shoe types on the duration of breakover in sound trotting horses

In a controlled experimental study, eight sound horses were shod with a plain steel shoe on one forelimb (control limb) and with four different shoe types on the other forelimb (treated limb). The four shoe types used on the treated limb were a plain steel shoe, a rocker-toe shoe, a rolled-toe shoe, and a square-toe shoe. The selection of the treatment limb (left or right) was randomized between the horses and a replicated Latin square design was used to determine the order of application of the shoes to the treatment limb. High speed cinematography (200 frames/s) was used to film the horses trotting in hand on a concrete surface. Eight strides were analyzed for each shoeing treatment. The breakover times of both forelimbs were measured, and the breakover ratio was computed as the ratio between the breakover time of the treated limb to the breakover time of the control limb. The results of an analysis of variance, using a probability of 0.05 alpha, showed that the breakover ratio did not differ significantly between the four types of shoes (p=0.10). It is concluded that, in sound horses trotting at a slow speed on a hard surface, the application of a rocker-toe shoe, a rolled-toe shoe or a square- toe shoe did not shorten forelimb breakover duration significantly compared with a plain steel shoe.