OBJECTIVE To evaluate the association between ultrasonographically measured optic nerve sheath diameter (ONSD) and acute increases in intracranial pressure (ICP) as measured by an epidural intracranial pressure monitoring system (EICPMS) in healthy dogs. ANIMALS 6 young healthy dogs. PROCEDURES An EICPMS connected to a pressure monitor was used to generate a continuous pressure waveform in each anesthetized dog. A 22-gauge IV catheter was inserted into the brain parenchyma through the contralateral parietal bone, and 0.5 to 2.0 mL of anticoagulated autologous blood was injected at predetermined intervals. At baseline (immediately after EICPMS placement) and following each injection, the ICP as indicated by EICPMS was recorded, and 3 ultrasonographic images of the optic nerve sheath of each eye were obtained. The ONSD was measured at maximum diameter and at 5 mm caudal to the optic disk. RESULTS In linear models, the maximum ONSD was positively associated with increasing ICP. Specifically, the rate of maximum ONSD increase was greater for pressures ≤ 20 mm Hg above baseline (0.0534 mm/1 mm Hg ICP increase) than for pressures > 40 mm Hg above baseline (0.0087 mm/1 mm Hg ICP increase). The relationship of ICP to maximum ONSD was slightly nonlinear and best explained by comparison of fractional polynomial regression models. CONCLUSIONS AND CLINICAL RELEVANCE ICP was positively and nonlinearly associated with increasing maximum ONSD, especially when ICP was ≤ 20 mm Hg above baseline, supporting the conclusion that ultrasonographic measurement of maximum ONSD may provide a noninvasive monitoring tool for evaluation of ICP in dogs. Further research is needed to assess the utility of these measurements in clinical patients.

OBJECTIVE To test a unique electronic ear tag designed to collect movement data to determine whether physical activity of sick steers differed from that of healthy steers. ANIMALS 206 steers. PROCEDURES Physical activity in 2 groups of steers during November and December of 2010 (101 steers; the tag of 1 steer failed, and thus that steer was removed from the study, which resulted in data for 100 steers) and 2011 (105 steers) was monitored with an electronic ear tag device with an on-board triple-axis accelerometer. The accelerometer recorded motion in all 3 axes in the form of counts per minute. A radio-frequency transmitter on the ear tag delivered serial packets of motion data to a local server. An algorithm was developed to analyze the activity data to determine whether this technique could be used to assess health status with high accuracy. RESULTS Steers that became sick had significantly fewer activity counts (approx 25% fewer), compared with the activity counts of steers that remained healthy the entire time. CONCLUSIONS AND CLINICAL RELEVANCE In this study, automated detection of health status in growing cattle was feasible through remote monitoring of animal activity. Early identification of sick animals should lead to improved health outcomes, increased marketability, and improved animal well-being and help to minimize the use of antimicrobials that could contribute to resistant bacteria.

OBJECTIVE To monitor concentrations of sulfadimidine in the paranasal sinus mucosa (PSM) of unsedated horses following IV administration of trimethoprim-sulfadimidine via in vivo microdialysis. ANIMALS 10 healthy adult horses. PROCEDURES Concentric microdialysis probes were implanted into the subepithelial layers of the frontal sinus mucosa of standing sedated horses. Four hours after implantation, trimethoprim-sulfadimidine (30 mg/kg) was administered IV every 24 hours for 2 days; dialysate and plasma samples were collected at intervals during that 48-hour period and analyzed for concentrations of sulfadimidine. The dialysate concentration and relative loss of sulfadimidine from the perfusate were used to calculate the PSM concentration. RESULTS Microdialysis probe implantation and subsequent in vivo microdialysis were successfully performed for all 10 horses. Following the first and second administration of trimethoprim-sulfadimidine, mean ± SD peak concentrations of sulfadimidine were 55.3 ± 10.3 μg/mL and 51.5 ± 8.7 μg/mL, respectively, in plasma and 9.6 ± 4.5 μg/mL and 7.0 ± 3.3 μg/mL, respectively, in the PSM. Peak sulfadimidine concentrations in the PSM were detected at 5.9 ± 2.7 hours and 5.4 ± 2.3 hours following the first and second drug administrations, respectively. For 12 hours, mean PSM sulfadimidine concentration remained greater than the minimum inhibitory concentration indicative of sulfonamide susceptibility of equine bacterial isolates (4.75 μg/mL). CONCLUSIONS AND CLINICAL RELEVANCE In vivo microdialysis for continuous monitoring of PSM sulfadimidine concentrations in unsedated horses was feasible. Intravenous administration of trimethoprim (5 mg/kg) and sulfadimidine (25 mg/kg) proved likely to be efficient for treating sinusitis caused by highly susceptible pathogens, providing that the dosing interval is 12 hours.

OBJECTIVE To generate reference intervals for ECG variables in clinically normal chimpanzees (Pan troglodytes). ANIMALS 100 clinically normal (51 young [< 10 years old] and 49 adult [≥ 10 years old]) wild-born chimpanzees. PROCEDURES Electrocardiograms collected between 2009 and 2013 at the Tchimpounga Chimpanzee Rehabilitation Centre were assessed to determine heart rate, PR interval, QRS duration, QT interval, QRS axis, P axis, and T axis. Electrocardiographic characteristics for left ventricular hypertrophy (LVH) and morphology of the ST segment, T wave, and QRS complex were identified. Reference intervals for young and old animals were calculated as mean ± 1.96•SD for normally distributed data and as 5th to 95th percentiles for data not normally distributed. Differences between age groups were assessed by use of unpaired Student t tests. RESULTS Reference intervals were generated for young and adult wild-born chimpanzees. Most animals had sinus rhythm with small or normal P wave morphology; 24 of 51 (47%) young chimpanzees and 30 of 49 (61%) adult chimpanzees had evidence of LVH as determined on the basis of criteria for humans. CONCLUSIONS AND CLINICAL RELEVANCE Cardiac disease has been implicated as the major cause of death in captive chimpanzees. Species-specific ECG reference intervals for chimpanzees may aid in the diagnosis and treatment of animals with, or at risk of developing, heart disease. Chimpanzees with ECG characteristics outside of these intervals should be considered for follow-up assessment and regular cardiac monitoring.

OBJECTIVE To use CT-derived measurements to create a ferret-specific formula for body surface area (BSA) to improve chemotherapeutic dosing. ANIMALS 25 adult ferrets (19 live and 6 cadavers). PROCEDURES Live subjects were weighed, and body measurements were obtained by each of 3 observers while ferrets were awake and anesthetized. Computed tomography was performed, and a 3-D surface model was constructed with open-source imaging software, from which BSA was estimated. The CT-derived values were compared with BSA calculated on the basis of the traditional tape method for 6 cadavers. To further validate CT analysis software, 11 geometric shapes were scanned and their CT-derived values compared with those calculated directly via geometric formulas. Agreement between methods of surface area estimation was assessed with linear regression. Ferret-specific formulas for BSA were determined with nonlinear regression models. RESULTS Repeatability among the 3 observers was good for all measurements, but some measurements differed significantly between awake and anesthetized ferrets. Excellent agreement was found between measured versus CT-derived surface area of shapes, traditional tape– versus CT-derived BSA of ferret cadavers, and CT-derived BSA of cadavers with and without monitoring equipment. All surface area formulas performed relatively similarly. CONCLUSIONS AND CLINICAL RELEVANCE CT-derived BSA measurements of ferrets obtained via open-source imaging software were reliable. On the basis of study results, the recommended formula for BSA in ferrets would be 9.94 × (body weight)2/3; however, this represented a relatively minor difference from the feline-derived formula currently used by most practitioners and would result in little practical change in drug doses.

OBJECTIVE To describe the ultrasonographic changes in the cricoarytenoideus dorsalis (CAD) and cricoarytenoideus lateralis (CAL) muscles of horses before and at various times during the 32 weeks after unilateral neurectomy of the right recurrent laryngeal nerve. ANIMALS 28 healthy Standardbreds. PROCEDURES For each horse, the appearance of the CAD and CAL muscles on the right (neurectomized) and left (control) sides was serially monitored ultrasonographically by percutaneous (CAD and CAL) and transesophageal (CAD) approaches. The ultrasonographic images were assessed to determine the mean pixel intensity, muscle thickness, and appearance grade, and comparisons were made between the muscles of the neurectomized and control sides. RESULTS The muscle appearance grade and mean pixel intensity for the CAL and CAD muscles on the neurectomized side were significantly increased by 2 and 4 weeks, respectively, after the neurectomy. The transesophageal approach enhanced the ultrasonographic visibility of the CAD muscle and allowed us to detect a significant decrease in the thickness of the CAD muscle on the neurectomized side over time, compared with thickness of the CAD muscle on the control side. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested ultrasonography can be used to successfully assess the CAL and CAD muscles of horses. A qualitative grading scheme was sufficient for successful detection and monitoring of muscle atrophy and reduced the need for image standardization. The transesophageal approach described for assessment of the CAD muscle warrants further investigation.

OBJECTIVE To evaluate the tear film osmolality and electrolyte composition in healthy horses. ANIMALS 15 healthy adult horses. PROCEDURES Each horse was manually restrained, and an ophthalmic examination, which included slit-lamp biomicroscopy, indirect ophthalmoscopy, and a Schirmer tear test, was performed. Tear samples were collected from both eyes with microcapillary tubes 3 times at 5-minute intervals. The tear samples for each horse were pooled, and the osmolality and electrolyte concentrations were measured. The mean (SD) was calculated for each variable to establish preliminary guidelines for tear film osmolality and electrolyte composition in healthy horses. RESULTS The mean (SD) tear film osmolality was 283.51 (9.33) mmol/kg, and the mean (SD) sodium, potassium, magnesium, and calcium concentrations were 134.75 (10), 16.3 (5.77), 3.48 (1.97), and 1.06 (0.42) mmol/L, respectively. The sodium concentration in the tear film was similar to that in serum, whereas the potassium concentration in the tear film was approximately 4.75 times that of serum. CONCLUSIONS AND CLINICAL RELEVANCE Results provided preliminary guidelines with which tear samples obtained from horses with keratopathies can be compared. Measurement of tear film osmolality in these horses was easy and noninvasive. The tear film concentration of divalent cations was greater than expected and was higher than the divalent cation concentrations in the tear films of rabbits and humans. These data may be clinically useful for the diagnosis and monitoring of hyperosmolar ocular surface disease in horses.