Retrospective analysis of detomidine infusion for standing chemical restraint in 51 horses

Objective To assess the effectiveness of a detomidine infusion technique to provide standing chemical restraint in the horse. Design Retrospective study. Animals Fifty‐one adult horses aged 9.5 ± 6.9 years (range 1–23 years) and weighing 575 ± 290.3 kg. Methods Records of horses presented to our clinic over a 3‐year period in which a detomidine infusion was used to provide standing chemical restraint were reviewed. Information relating to the types of procedure performed, duration of infusion, drug dosages and adjunct drugs administered was retrieved. Results Detomidine was administered as an initial bolus loading dose (mean ± SD) of 7.5 ± 1.87 µg kg^?1. The initial infusion rate was 0.6 µg kg^?1 minute^?1, and this was halved every 15 minutes. The duration of the infusion ranged from 20 to 135 minutes. Twenty horses received additional detomidine or butorphanol during the procedure. All horses undergoing surgery received local anesthesia or epidural analgesia in addition to the detomidine infusion. A wide variety of procedures were performed in these horses. Conclusions Detomidine administered by infusion provides prolonged periods of chemical restraint in standing horses. Supplemental sedatives or analgesics may be needed in horses undergoing surgery. Clinical relevance An effective method that provides prolonged periods of chemical restraint in standing horses is described. The infusion alone did not provide sufficient analgesia for surgery and a significant proportion of animals required supplemental sedatives and analgesics.     

DEGENERATIVE CHANGES IN THE VERTEBRAL COLUMN OF THE DOG

A group of 160 Beagles were studied radiographically to determine the pattern of degenerative changes within the vertebral column, especially involving the intervertebral discs. The normal radiographic appearance of both disc and surrounding vertebrae is described. Disc space narrowing and calcification of discal tissues provide radiographic patterns that assist in diagnosis and prognosis. Because of the older age of the dogs, severe degeneration of the endplates with marked instability between vertebral segments was seen.     

Retracted: Effect of Post‐Thaw Storage Time on Motility and Fertility of Cryopreserved Beluga Sturgeon (Huso huso) Sperm

The aim of this study was to test the influence of post ‐ thaw storage time on the duration of sperm motility, percentage of motile sperm, and fertilization and hatching rates of fresh sperm and sperm stored for 0, 30 and 60 min at 4°C post‐thawing. After being frozen in liquid nitrogen and then thawed, the percentage of motile sperm and duration of motility were not affected by 30 min of storage at 4°C, whereas a significant decline in these parameters was observed after 60 min of storage. Similarly, fertilization and hatching rates were significantly affected within 60 min of storage at 4°C, and the fertility of frozen‐thawed sperm was significantly lower than that of fresh sperm. We conclude that cryopreserved sperm of beluga sturgeon could be stored for 30 min without the loss of sperm quality. This described procedure for beluga sturgeon cryopreservation is reliable and efficient and therefore can be recommended for hatchery practice after scaling up this technique.     

QUANTITATIVE ASSESSMENT OF SURGICALLY INDUCED MITRAL REGURGITATION USING RADIONUCLIDE VENTRICULOGRAPHY AND FIRST PASS RADIONUCLIDE ANGIOGRAPHY

Radionuclide ventriculography has been used in humans to evaluate valvular incompetency. The stroke volume ratio, derived from the radionuclide ventriculogram, is used to quantify the severity of mitral regurgitation (MR). Previous studies conducted in humans have shown that left to right stroke volume ratio increases as the severity of MR increases. In this study, we evaluated radionuclide ventriculography as a noninvasive method to detect MR in dogs with surgically created mitral insufficiency. Six male and three female adult, conditioned mongrel dogs were used. Scintigraphic studies were performed prior to and 4 weeks after surgically created MR. Because of the overlap of the left and right ventricles when viewed from a left lateral position, we combined data from a first-pass radionuclide angiocardiogram with the radionuclide ventriculogram to obtain a corrected stroke volume ratio. Blood flow transit parameters were also derived from the first-pass radionuclide angiocardiogram. Standard left ventricular functional indices were also measured from the radionuclide ventriculogram. On the left lateral view of the heart, 25 to 30% of the right ventricular volume overlaps the left ventricle. After correcting for the overlap, the stroke volume ratio of normal dogs was 1.17±0.178 (mean±SD), which increased to 2.06±0.41 (mean±SD) (p<.001) 4 weeks after creation of MR. The was no significant change in left ventricular ejection fraction or peak rate of ejection following MR. The transit times of blood through the left ventricle were measured from the first-pass radionuclide angiocardiogram and were expressed as half-time clearance, peak clearance rate, and time to peak clearance rate. The baseline half-time clearance was 2.07±0.71 s (mean±SD), which increased to 6.70±4.89 s (mean±SD) (p=.02) after creation of MR. The baseline peak clearance rate was 49.75±8.96 cts/s (mean±SD), which decreased to 23.12±6.84 cts/s (mean±SD) (p<.001) after creation of MR. Stroke volume ratios significantly increased following creation of MR. Blood flow transit through the left ventricle slowed following creation of MR. The variability of these parameters were small in the baseline studies, suggesting these techniques may be clinically useful to gauge the severity of MR in dogs.     

Influence of Cholinergic Blockade on the Development of Epinephrine-Induced Ventricular Arrhythmias in Halothane- and Isoflurane-Anesthetized Dogs

The arrhythmogenic effects of anesthetic drugs are assessed using the arrhythmogenic dose of epinephrine (ADE) model. The purpose of this study was to determine the influence of cholinergic blockade (CB) produced by glycopyrrolate (G) on ADE in 1.5 minimum alveolar concentration (MAC) halothane (H)- and isoflurane (I)-anesthetized dogs. Eight dogs (weighing between 12.5 and 21.5 kg) were randomly assigned to four treatment groups (H, HG, I, and IG) and each treatment was replicated three times. Anesthesia was induced and maintained with H (1.31%, end-tidal [ET]) or I (1.95%, ET) in oxygen. Ventilation was controlled (carbon dioxide [PCO₂] 35 to 40 mmHg, ET). G was administered 10 minutes before ADE determination at a dose of 22 μg/kg (11 μg/kg, intravenous [IV] and 11 μg/kg, intramuscular [IM]). The ADE was determined by IV infusion of epinephrine at sequentially increasing rates of 1.0, 2.5, and 5.0 μg/kg/min; and defined as the total dose of epinephrine producing at least four ectopic ventricular contractions (EVCs) within 15 seconds during a 3-minute infusion and up to 1 minute after the end of the infusion. Total dose was calculated as the product of infusion rate and time to arrhythmia. Data were analyzed using a randomized complete block analysis of variance. When significant (P < .05) F values were found a least significant difference test was used to compare group means. Values are reported as means ± standard error. The ADE (μg/kg) for H, HG, I, and IG were 1.53 ± 0.08, 3.37 ± 0.46, 1.61 ± 0.21, and > 15.00, respectively. Heart rates (HRs) (beats/min) and systolic pressures (mmHg) at the time of arrhythmia formation for H, HG, I, and IG were (60.3 ±4.0 and 142.0 ± 7.6), (213.0 ± 13.1 and 239.2 ± 7.1), (62.9 ± 4.5 and 151.9 ± 6.3), and (226.3 ± 6.1 and 323.5 ± 3.4), respectively. The H and I ADE were not different. The HG ADE was significantly less than the IG ADE. The H and I ADE were significantly less than the HG and IG ADE. We conclude the following from the results of this study of epinephrine infusion in halothane- and isoflurane-anesthetized dogs: (1) two distinct mechanisms are responsible for the development of arrhythmias, (2) CB produced by G significantly increases ADE but is associated with higher rate pressure products (RPP) and myocardial work, and (3) ADE methodology could be improved by determining ADE with and without CB.     

Thrombolytic Therapy in Dogs and Cats

Objective: To review the thrombolytic agents most commonly used in humans, their mechanisms of action, potential uses, adverse effects, and reports of their use in dogs and cats.
Human data synthesis: Thrombolytic agents avaliable in human medicine include streptokinase, urokinase, tissueplasminogen activator (t-PA), single-chain urokinase plasma activator (scu-PA) and anisoylated plasminogen-strep-tokinase activator complex (APSAC). These agents were originally used for the management of proximal deep vein thrombosis and severe pulmonary embolism but more recently, use of these drugs has been extended to include the treatment of acute peripheral arterial disease, cerebrovascular disease (stroke) and acute coronary thrombosis. The most predictable side effect associated with the use of thrombolytic therapy is hemorrhage.
Veterinary data synthesis: Clinical experience with thrombolytic agents in small animals is limited to streptokinase and t-PA. It is possible, that as in humans, canine and feline patients with PTE and right ventricular dysfunction may benefit from thrombolytic therapy but there are no veterinary studies to support this theory to date. Successful use of streptokinase has been documented in a small number of canine patients with systemic thromboembolism. ⁶³ Thrombolytic therapy is relatively efficacious in cats with aortic thromboemboli but is associated with a high mortality rate. ^59,60,64 With regard to use of t-PA in veterinary medicine, the small number of animals treated with varying protocols makes it impossible to provide safe and effective dose recommendations at this time.
Conclusions: Future goals for thrombolytic therapy in veterinary medicine include determination of more specific clinical indications, as well as design of effective protocols that minimize mortality and morbidity.     

Effect of Season on Travel Patterns and Hoof Growth of Domestic Horses

Four Morgan mares and five Morgan geldings ranging in age from 5- to 12-years-old were fitted with Global Positioning System units to determine if season has an influence on travel pattern. Body and hoof growth measurements were obtained so that the influence of season on body condition and hoof growth could be determined. Waist and heart circumference, cresty neck score, and body condition score were determined in each season. The ambient temperature and precipitation was recorded for each season. Waist circumference was the greatest (P < .05) in the spring and summer and the least in the fall and winter. Hoof growth was the greatest (P < .05) in the fall and the least in the winter. The front and rear hooves grew at similar rates in all horses. Hoof growth in geldings and mares were also similar. The average distances traveled were similar across seasons; however, the horse did numerically travel more in the spring and summer compared with the fall and winter. The range of the travel pattern was influenced by season with the horses traveling significantly less in the winter, although the average travel distances were similar. In conclusion, season in temperate zones will influence body condition, hoof growth, and pattern of travel, but the total distance traveled will be similar. Further research needs to be conducted to determine the influence of season on hoof growth and travel patterns.