OBJECTIVE To elucidate the relationship between acute volume overload and left atrial phasic function in healthy dogs. ANIMALS 6 healthy Beagles. PROCEDURES Dogs were anesthetized. A Swan-Ganz catheter was placed to measure mean pulmonary capillary wedge pressure (PCWP). Cardiac preload was increased by IV infusion with lactated Ringer solution at 150 mL/kg/h for 90 minutes. Transthoracic echocardiography was performed before (baseline) and at 15, 30, 45, 60, 75, and 90 minutes after volume loading began. At each echocardiographic assessment point, apical 4-chamber images were recorded and analyzed to derive time–left atrial area curves. Left atrial total (for reservoir function), passive (for conduit function), and active (for booster-pump function) fractional area changes were calculated from the curves. RESULTS Volume overload resulted in a significant increase from baseline in PCWP from 15 to 90 minutes after volume loading began. All fractional area changes at 15 to 90 minutes were significantly increased from baseline. In multiple regression analysis, quadratic regression models were better fitted to the relationships between PCWP and each of the total and active fractional area changes than were linear regression models. A linear regression model was better fitted to the relationship between PCWP and passive fractional area change. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that left atrial phasic function assessed on the basis of left atrial phasic areas was enhanced during experimental cardiac volume loading in healthy dogs. The effect of volume load should be considered when evaluating left atrial phasic function by indices derived from left atrial phasic sizes.

OBJECTIVE To evaluate the potential usefulness of epiduroscopy for clinical diagnosis and treatment of vertebral canal and spinal cord lesions in dogs. SAMPLE Cadavers of 6 mixed-breed dogs. PROCEDURES Dogs were positioned in sternal recumbency, and an endoscope was introduced into the lumbosacral epidural space. A fiberscope (diameter, 0.9 mm; length, 30 cm) was used for 3 dogs, and a videoscope (diameter, 2.8 mm; length, 70 cm) was used for the other 3 dogs. Visibility and identities of anatomic structures were recorded, and maneuverability of the endoscopes was assessed. Extent of macroscopic tissue damage was evaluated by manual dissection of the vertebral canal at the end of the procedure. RESULTS Intermittent saline (0.9% NaCl) solution infusion, CO2 insufflation, and endoscope navigation improved visualization by separating the epidural fat from the anatomic structures of interest. Images obtained with the fiberscope were small and of poor quality, making identification of specific structures difficult. Maneuverability of the fiberscope was difficult, and target structures could not be reliably reached or identified. Maneuverability and image quality of the videoscope were superior, and spinal nerve roots, spinal dura mater, epidural fat, and blood vessels could be identified. Subsequent manual dissection of the vertebral canal revealed no gross damage in the spinal cord, nerve roots, or blood vessels. CONCLUSIONS AND CLINICAL RELEVANCE A 2.8-mm videoscope was successfully used to perform epiduroscopy through the lumbosacral space in canine cadavers. Additional refinement and evaluation of the technique in live dogs is necessary before its use can be recommended for clinical situations.

OBJECTIVE To evaluate muscle activity and hand motion in veterinarians performing a standard set of laparoscopic training tasks. SAMPLE 12 veterinarians with experience performing laparoscopic procedures. PROCEDURES Participants were asked to perform peg transfer, coordination, precision cutting, and suturing tasks in a laparoscopic box trainer. Activity of the right biceps brachii, triceps brachii, forearm flexor, forearm extensor, and trapezius muscles was analyzed by means of surface electromyography. Right hand movements and wrist angle data were registered through the use of a data glove, and risk levels for the wrist joint were determined by use of a modified rapid upper limb assessment (RULA) method. One-way repeated-measures ANOVA with a Bonferroni post hoc test was performed to compare values between tasks. RESULTS Activity in the biceps muscle did not differ significantly among the 4 tasks. Activity in the triceps, forearm flexor, and forearm extensor muscles was significantly higher during precision cutting than during the coordination task. Activity in the trapezius muscle was highest during the suturing task and did not differ significantly among the other 3 tasks. The RULA score was unacceptable (score, 3) for the coordination, peg transfer, and precision cutting tasks but was acceptable (score, 2) for the suturing task. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that the ergonomics of laparoscopic training depended on the tasks performed and the design of the instruments used. Precision cutting and suturing tasks were associated with the highest muscle activity. Acceptable wrist position, as determined with the RULA method, was found with the suturing task, which was performed with an axial-handled instrument.

OBJECTIVE To determine the predominant thromboxane (TX) metabolite in urine of healthy cats, evaluate whether the method of sample collection would impact concentration of that metabolite, and propose a reference interval for that metabolite in urine of healthy cats. ANIMALS 17 cats (11 purpose-bred domestic shorthair cats, 5 client-owned domestic shorthair cats, and 1 client-owned Persian cat). PROCEDURES All cats were deemed healthy on the basis of results for physical examination, a CBC, serum biochemical analysis, urinalysis, and measurement of prothrombin time and activated partial thromboplastin time. Voided and cystocentesis urine samples (or both) were collected. Aliquots of urine were stored at −80°C until analysis. Concentrations of TXB2, 11-dehydroTXB2, and 2,3 dinorTXB2 were measured with commercially available ELISA kits. Urinary creatinine concentration was also measured. RESULTS 11-dehydroTXB2 was the most abundant compound, representing (mean ± SD) 59 ± 18% of the total amount of TX detected. In all samples, the concentration of 11-dehydroTXB2 was greater than that of 2,3 dinorTXB2 (mean, 4.2 ± 2.7-fold as high). Mean concentration of 11-dehydroTXB2 for the 17 cats was 0.57 ± 0.47 ng/mg of creatinine. A reference interval (based on the 5% to 95% confidence interval) of 0.10 to 2.1 ng of 11-dehydroTXB2/mg of creatinine was proposed for healthy cats. CONCLUSIONS AND CLINICAL RELEVANCE In this study, 11-dehydroTXB2 was the major TX metabolite in feline urine. Measurement of this metabolite may represent a noninvasive, convenient method for monitoring in vivo platelet activation in cats at risk for thromboembolism.

OBJECTIVE To evaluate the effects of successive large-segment tracheal resection and anastomosis on tracheal diameter and position of lobar bronchi in dogs. ANIMALS 5 adult Beagles. PROCEDURES Right lateral radiographs were obtained for all dogs and used to measure tracheal length. Dogs were then euthanized, and successive segmental tracheal resections (intervals of 10% from 20% to 50% of the tracheal length), each of which was followed by anastomosis, were performed in each cadaver. Tracheobronchoscopy was performed before the first tracheal resection and after each of the anastomoses to evaluate tracheal diameter and changes in position of lobar bronchi. RESULTS Tracheal diameter was minimally affected by resections up to 50% of the tracheal length. Diameter of the trachea and position of bronchi were not affected by resection of 20% of the tracheal length. Changes in the position of various lobar bronchi were detected after resection of 30% of the tracheal length. CONCLUSIONS AND CLINCIAL RELEVANCE In this study, tracheal resections of 20% of the tracheal length were accommodated, possibly as a result of stretching of the annular ligament. Resections of ≥ 30% of the tracheal length altered the position of lobar bronchi. Clinical effects, if any, attributable to these changes in bronchial position remain to be elucidated.

OBJECTIVE To evaluate the closure rate and completeness of closure for a silicone–polyacrylic acid gradual venous occlusion device placed around an intra-abdominal vein to simulate gradual occlusion of an extrahepatic portosystemic shunt. ANIMALS 3 purpose-bred cats and 2 purpose-bred dogs. PROCEDURES The device was surgically placed around an external (cats) or internal (dogs) iliac vein. Computed tomographic angiography was performed at the time of surgery and 2, 4, and 6 weeks after surgery. Ultrasonographic examinations of blood flow through the vein within the device were performed at the time of surgery and at weekly intervals thereafter. Dogs were euthanized 6 weeks after surgery, and the external iliac veins were harvested for histologic examination. RESULTS The prototype gradual venous occlusion device was successfully placed in all animals, and all animals recovered without complications following the placement procedure. The vessel was completely occluded in 2 cats by 6 weeks after surgery, as determined on the basis of results of CT and ultrasonography; there was incomplete occlusion with a luminal diameter of 1.5 mm in the other cat by 6 weeks after surgery. The vessel was completely occluded in both dogs by 6 weeks after surgery. Histologic examination of the external iliac veins obtained from the dogs revealed minimal inflammation of the vessel wall and no thrombus formation. CONCLUSIONS AND CLINICAL RELEVANCE The prototype device induced gradual attenuation of an intra-abdominal vessel over a 6-week period. This device may provide another option for gradual occlusion of extrahepatic portosystemic shunts.

OBJECTIVE To determine the effects of racetrack surface and shoe characteristics on formation of wear grooves in the horseshoes of racehorses. SAMPLES 1,121 horseshoes from 242 Thoroughbred racehorses collected during routine horseshoeing procedures at 4 racetracks with dirt or synthetic surfaces. PROCEDURES Data for 1,014 horseshoes from 233 racehorses were analyzed. Horseshoes were photographed, and length and width of grooves formed at the heels of the solar surface of horseshoes were measured on the photographs. Effects of racetrack, racetrack surface, and shoe characteristics (eg, shoe size, clips, and nails) on length and width of grooves were assessed by use of a mixed-model anova. RESULTS Length and width of wear grooves differed significantly on the basis of racetrack, nail placement, and limb side (left vs right). Differences in groove dimensions between types of racetrack surface (dirt vs synthetic) were less apparent than differences among racetracks. CONCLUSIONS AND CLINICAL RELEVANCE Measurements of the length and width of wear grooves in the horseshoes of racehorses may be useful for understanding some aspects of hoof interactions with various racetrack surfaces. Interpretation of differences in wear grooves for various racetrack surfaces will likely require quantitation of the mechanical behavior of the surfaces.

The objective of this study was to evaluate the stability of 3 distinct preparations of ketamine and xylazine, with or without acepromazine, stored at room temperature or at 4°C for 1, 2, and 3 mo. Drug concentrations were compared to fresh solutions, using a high performance liquid chromatography-mass spectrometry/selected-ion monitoring (HPLC-MS/SIM) assay. The concentrations of ketamine and xylazine, diluted in physiological saline, did not change over time at room temperature or at 4°C. However, acepromazine concentrations decreased over time when stored at room temperature. In contrast, undiluted ketamine-xylazine preparations gradually decreased in concentration when stored at room temperature. All of the drug concentrations remained above 90% of their original concentration when stored at 4°C. In conclusion, when diluted in physiological saline, ketamine-xylazine cocktails can be stored for 3 mo, whereas undiluted cocktails can lose efficacy over 3 mo at room temperature. Storage at 4°C could preserve drug stability.

OBJECTIVE To measure thrombin generation by high and low tissue factor (TF)–expressing canine cancer cell lines. SAMPLE Canine cell lines CMT25 (high TF–expressing mammary gland tumor cell line) and HMPOS (low TF–expressing osteosarcoma cell line). PROCEDURES Thrombin generation by cancer cells was measured in pooled normal canine plasma by use of calibrated automated thrombography without added trigger reagents. Results were expressed as lag time, time to peak thrombin concentration, peak thrombin concentration, and total thrombin concentration or thrombin generation potential. Corn trypsin inhibitor, hirudin, and annexin V were used to inhibit contact activation, thrombin formation, and phosphatidylserine activity, respectively. Pooled normal human plasma deficient in coagulation factors VII, VIII, IX, X, XI, or XII was used to assess the role of individual coagulation factors on thrombin generation. RESULTS CMT25 generated significantly more thrombin than did HMPOS (mean ± SD, 3,555 ± 604nM thrombin•min and 636 ± 440nM thrombin•min, respectively). Thrombin generation of CMT25 was dependent on factor VII and phosphatidylserine and was independent of contact activation. In contrast, thrombin generation of HMPOS was attributed to contact activation. CONCLUSIONS AND CLINICAL RELEVANCE High TF-expressing canine mammary cancer cells generated thrombin in a plasma milieu in vitro in a factor VII- and phosphatidylserine-dependent manner. These findings support a role for TF in hypercoagulability detected in dogs with mammary gland tumors and potentially for other tumors that strongly express TF.

OBJECTIVE To evaluate the effects of treatment of horses with standard platelet inhibitors on ex vivo inhibition of platelet activation by equine herpesvirus type I (EHV-I). ANIMALS II healthy adult horses. PROCEDURES In a double-blinded, placebo-controlled crossover study, horses were treated orally for 5 days with theophylline (5 mg/kg, q 12 h), pentoxifylline (10 mg/kg, q 12 h), clopidogrel bisulfate (4 mg/kg, q 24 h), acetylsalicylic acid (20 mg/kg, q 24 h), or placebo. Horses received all treatments, each separated by a 3-week washout period. Platelet-rich plasma was prepared from citrated blood samples obtained before each treatment session and 4 hours after each final drug dose. Platelets were exposed to 2 EHV-I strains (at I plaque forming units/cell) or positive (thrombin-convulxin) and negative control substances for 10 minutes, then platelet activation was assessed by determining the percentages of P-selectin–positive platelets and platelet-derived microparticles (PDMPs; small events positive for annexin V) with flow cytometry. Platelet aggregation in response to 10μM ADP was also assessed. RESULTS No significant differences in median percentages of P-selectin–positive platelets and PDMPs in EHV-I-exposed platelets were identified between measurement points (before and after treatment) for all drugs, nor were differences identified among drugs at each measurement point. Only clopidogrel significantly inhibited platelet aggregation in response to ADP in platelet-rich plasma samples obtained after that treatment session. CONCLUSIONS AND CLINICAL RELEVANCE Treatment of horses with standard platelet inhibitors had no effect on EHV-I-induced platelet α-granule exteriorization or microvesiculation and release of PDMPs ex vivo, suggesting these drugs will not prevent platelet activation induced directly by EHV-I in vivo.