The objective of this study was to determine the effects of propofol on the minimum alveolar concentration of sevoflurane needed to prevent motor movement (MACNM) in dogs subjected to a noxious stimulus using randomized crossover design. Six, healthy, adult beagles (9.2 ± 1.3 kg) were used. Dogs were anesthetized with sevoflurane on 3 occasions, at weekly intervals, and baseline MACNM (MACNM-B) was determined on each occasion. Propofol treatments were administered as loading dose (LD) and constant rate infusion (CRI) as follows: Treatment 1 (T1) was 2 mg/kg body weight (BW) and 4.5 mg/kg BW per hour; T2 was 4 mg/kg BW and 9 mg/kg BW per hour; T3 was 8 mg/kg BW and 18 mg/kg BW per hour, respectively. Treatment MACNM (MACNM-T) determination was initiated 60 min after the start of the CRI. Two venous blood samples were collected and combined at each MACNM-T determination for measurement of blood propofol concentration using high-performance liquid chromatography method (HPLC). Data were analyzed using a mixed-model ANOVA and are presented as least square means (LSM) ± standard error of means (SEM). Propofol infusions in the range of 4.5 to 18 mg/kg BW per hour resulted in mean blood concentrations between 1.3 and 4.4 μg/mL, and decreased (P < 0.05) sevoflurane MACNM in a concentration-dependent manner. The percentage decrease in MACNM was 20.5%, 43.0%, and 68.3%, with corresponding blood propofol concentrations of 1.3 ± 0.3 μg/mL, 2.5 ± 0.3 μg/mL, and 4.4 ± 0.3 μg/mL, for T1, T2, and T3, respectively. Venous blood propofol concentrations were strongly correlated (r = 0.855, P < 0.0001) with the decrease in MACNM. In dogs, propofol decreased the sevoflurane MACNM in a concentration-dependent manner.

Objective—To describe findings of 3.0-T multivoxel proton magnetic resonance spectroscopy (1H-MRS) in dogs with inflammatory and neoplastic intracranial disease and to determine the applicability of 1H-MRS for differentiating between inflammatory and neoplastic lesions and between meningiomas and gliomas. Animals—33 dogs with intracranial disease (19 neoplastic [10 meningioma, 7 glioma, and 2 other] and 14 inflammatory). Procedures—3.0-T multivoxel 1H-MRS was performed on neoplastic or inflammatory intracranial lesions identified with conventional MRI. N-acetylaspartate (NAA), choline, and creatine concentrations were obtained retrospectively, and metabolite ratios were calculated. Values were compared for metabolites separately, between lesion categories (neoplastic or inflammatory), and between neoplastic lesion types (meningioma or glioma) by means of discriminant analysis and 1-way ANOVA. Results—The NAA-to-choline ratio was 82.7% (62/75) accurate for differentiating neoplastic from inflammatory intracranial lesions. Adding the NAA-to-creatine ratio or choline-to-creatine ratio did not affect the accuracy of differentiation. Neoplastic lesions had lower NAA concentrations and higher choline concentrations than inflammatory lesions, resulting in a lower NAA-to-choline ratio, lower NAA-to-creatine ratio, and higher choline-to-creatine ratio for neoplasia relative to inflammation. No significant metabolite differences between meningiomas and gliomas were detected. Conclusions and Clinical Relevance—1H-MRS was effective for differentiating inflammatory lesions from neoplastic lesions. Metabolite alterations for 1H-MRS in neoplasia and inflammation in dogs were similar to changes described for humans. Use of 1H-MRS provided no additional information for differentiating between meningiomas and gliomas. Proton MRS may be a beneficial adjunct to conventional MRI in patients with high clinical suspicion of inflammatory or neoplastic intracranial lesions.

The study objective was to determine the effects of 70% nitrous oxide (N2O) and fentanyl on the end-tidal concentration of sevoflurane necessary to prevent movement (MACNM) in response to noxious stimulation in dogs. Six healthy, adult, intact male, mixed-breed dogs were used on 3 occasions in a randomized crossover design. After induction of anesthesia with sevoflurane, each of the following treatments was randomly administered: fentanyl loading dose (Ld) of 15 μg/kg and infusion of 6 μg/kg per hour [treatment 1 (T1)], 70% N2O (T2), or fentanyl (Ld of 15 μg/kg and infusion of 6 μg/kg per hour) combined with 70% N2O (T3). Each dog received each of the 3 treatments once during the 3-week period. Determination of MACNM was initiated 90 min after the start of each treatment. The values were compared using the baseline MACNM, which had been determined in a previous study on the same group of dogs. Data were analyzed using a mixed-model analysis of variance (ANOVA) and Tukey-Kramer tests, and expressed as least squares mean ± SEM. The baseline MACNM decreased by 36.6 ± 4.0%, 15.0 ± 4.0%, and 46.0 ± 4.0% for T1, T2, and T3, respectively (P < 0.05), and differed (P < 0.05) among treatments. Mean fentanyl plasma concentrations did not differ (P ≥ 0.05) between T1 (3.70 ± 0.56 ng/mL) and T3 (3.50 ± 0.56 ng/mL). The combination of fentanyl and N2O resulted in a greater sevoflurane MACNM sparing effect than either treatment alone.

Objective-To determine the effect of dexmedetomidine, morphine-lidocaine-ketamine (MLK), and dexmedetomidine-morphine-lidocaine-ketamine (DMLK) constant rate infusions on the minimum alveolar concentration (MAC) of isoflurane and bispectral index (BIS) in dogs. Animals-6 healthy adult dogs. Procedures-Each dog was anesthetized 4 times with a 7-day washout period between anesthetic episodes. During the first anesthetic episode, the MAC of isoflurane (baseline) was established. During the 3 subsequent anesthetic episodes, the MAC of isoflurane was determined following constant rate infusion of dexmedetomidine (0.5 μg/kg/h), MLK (morphine, 0.2 mg/kg/h; lidocaine, 3 mg/kg/h; and ketamine, 0.6 mg/kg/h), or DMLK (dexmedetomidine, 0.5 μg/kg/h; morphine, 0.2 mg/kg/h; lidocaine, 3 mg/kg/h; and ketamine 0.6 mg/kg/h). Among treatments, MAC of isoflurane was compared by means of a Friedman test with Conover posttest comparisons, and heart rate, direct arterial pressures, cardiac output, body temperature, inspired and expired gas concentrations, arterial blood gas values, and BIS were compared with repeated-measures ANOVA and a Dunn test for multiple comparisons. Results-Infusion of dexmedetomidine, MLK, and DMLK decreased the MAC of isoflurane from baseline by 30%, 55%, and 90%, respectively. Mean heart rates during dexmedetomidine and DMLK treatments was lower than that during MLK treatment. Compared with baseline values, mean heart rate decreased for all treatments, arterial pressure increased for the DMLK treatment, cardiac output decreased for the dexmedetomidine treatment, and BIS increased for the MLK and DMLK treatments. Time to extubation and sternal recumbency did not differ among treatments. Conclusions and Clinical Relevance-Infusion of dexmedetomidine, MLK, or DMLK reduced the MAC of isoflurane in dogs.

Objective-To determine kinematic changes to the hoof of horses at a walk after induction of unilateral, weight-bearing forelimb lameness and to determine whether hoof kinematics return to prelameness (baseline) values after perineural anesthesia. Animals-6 clinically normal Quarter Horses. Procedures-For each horse, a sole-pressure model was used to induce 3 grades of lameness in the right forelimb, after which perineural anesthesia was administered to eliminate lameness. Optical kinematics were obtained for both forelimbs with the horse walking before (baseline) and after induction of each grade of lameness and after perineural anesthesia. Linear acceleration profiles were used to identify hoof events, and each stride was divided into hoof-contact, break-over, initial-swing, terminal-swing, and total-swing segments. Kinematic variables were compared within and between limbs for each segment by use of mixed repeated-measures ANOVA. Results-During the hoof-contact and terminal-swing segments, the hoof of the left (nonlame) forelimb had greater sagittal-plane orientation than did the hoof of the right (lame) forelimb. For the lame limb following lameness induction, the break-over duration and maximum cranial acceleration were increased from baseline. After perineural anesthesia, break-over duration for the lame limb returned to a value similar to that at baseline, and orientation of the hoof during the terminal-swing segment did not differ between the lame and nonlame limbs. Conclusions and Clinical Relevance-Subclinical unilateral forelimb lameness resulted in significant alterations to hoof kinematics in horses that are walking, and the use of hoof kinematics may be beneficial for the detection of subclinical lameness in horses.

Objective: To determine the accuracy of 3-D and 2-D ultrasonography for quantification of tumor volume in dogs with transitional cell carcinoma (TCC) of the urinary bladder. Animals: 10 dogs with biopsy-confirmed TCC. Procedures: The urinary bladder of each dog was distended with saline (0.9% NaCl) solution (5.0 mL/kg), and masses were measured via 3-D and 2-D ultrasonography. Masses were also measured via 3-D ultrasonography after bladders were distended with 2.5 and 1.0 mL of saline solution/kg. Subsequently, the bladder was deflated and distended with CO2 (5.0 mL/kg); CT was performed after IV contrast medium administration. Tumor volumes were calculated via 3-D ultrasonography, 2-D ultrasonography, and CT (reference method) and compared via ANOVA, Deming regression, and Bland-Altman plots. Repeated-measures ANOVA was used to assess effects of bladder distension on 3-D tumor volume measurements. Repeatability of measurements was estimated via the coefficient of variation for each method. Results: Repeatability was considered good for all 3 methods. There was no significant difference in tumor volume measurements obtained via 3-D ultrasonography at different degrees of urinary bladder distension. Results of Deming regression and Bland-Altman plots indicated excellent agreement between tumor volume measurement with 3-D ultrasonography and CT, but not between 2-D ultrasonography and CT. Conclusions and Clinical Relevance: Tumor volume in dogs with TCC of the urinary bladder was accurately measured via 3-D ultrasonography. Use of 3-D ultrasonography can provide a less expensive and more practical method for monitoring response to treatment than CT and was more accurate than 2-D ultrasonography.

Objective--To refine and test construct validity and reliability of a composite pain scale for use in assessing acute postoperative pain in cats undergoing ovariohysterectomy. Sample Population--40 cats that underwent ovariohysterectomy in a previous study. Procedures--In a previous randomized, double-blind, placebo-controlled study, a composite pain scale was developed to assess postoperative pain in cats that received a placebo or an analgesic (tramadol, vedaprofen, or tramadol-vedaprofen combination). In the present study, the scale was refined via item analysis (distribution frequency and occurrence), a nonparametric ANOVA, and item-to-total score correlation. Construct validity was assessed via factor analysis and known-groups discrimination, and reliability was measured by assessing internal consistency. Results--Respiratory rate and respiratory pattern were rejected after item analysis. Factor analysis resulted in 5 dimensions (F1 [psychomotor change], posture, comfort, activity, mental status, and miscellaneous behaviors; F2 [protection of wound area], reaction to palpation of the surgical wound and palpation of the abdomen and flank; F3 [physiologic variables], systolic arterial blood pressure and appetite; F4 [vocal expression of pain], vocalization; and F5 [heart rate]). Internal consistency was excellent for the overall scale and for F1, F2, and F3; very good for F4; and unacceptable for F5. Except for heart rate, the identified factors and scale total score could be used to detect differences between the analgesic and placebo groups and differences among the analgesic treatments. Conclusions and Clinical Relevance--Results provided initial evidence of construct validity and reliability of a multidimensional composite tool for use in assessing acute postoperative pain in cats undergoing ovariohysterectomy.

To test the hypothesis that the pulmonary vascular pressures of Thoroughbred and Standardbred horses behave similarly during exertion. Measurements were made on 5 Thoroughbred and 5 Standardbred horses on a treadmill at rest and during 3-minute exercise intervals at speeds predicted to produce 75%, 90%, and 100% maximal heart rate. Left forelimb acceleration, heart rate, esophageal pressure, and pulmonary artery pressure were measured continuously. Pulmonary capillary and wedge pressures were measured during intermittent occlusion of the pulmonary artery. Breathing rate and gait frequency were the fundamental frequencies of the esophageal pressure and limb acceleration signals respectively. The ratio of speed:gait frequency gave stride length. The effects of exertion and breed were evaluated using two-way analysis of variance. Exertion produced significant increases in pulmonary artery (P = 0.001), capillary (P= 0.002), and wedge (P= 0.005) pressures. No significant effect of breed was detected on pulmonary artery pressure, but at exertion pulmonary capillary and wedge pressures were 15% (P= 0.03) and 23% (P= 0.04) greater in Thoroughbreds, respectively. Treadmill speed was ~12% greater (P= 0.04), stride length was ~25% greater (P= 0.0003), gait frequency was ~10% less (P= 0.006), breathing rate was ~10% less (P= 0.001), and heart rate was ~6% less (P= 0.06) for Thoroughbreds. There was no effect of breed on inspiratory or expiratory esophageal pressure although mean esophageal pressure was ~2 mmHg greater (P= 0.03) in exercising Standardbreds. In conclusion, pulmonary capillary and wedge pressures are greater in Thoroughbreds than in Standardbreds at similar fractions of maximal heart rate. This is compatible with the higher incidence of exercise-induced pulmonary hemorrhage observed in Thoroughbreds.

Serum alpha-mannosidase activity and swainsonine concentration were determined in 4 cattle and 15 sheep (3 groups of 5 each) that were administered ground locoweed (Oxytropis sericea or Astragalus lentiginosus) containing swainsonine at dosages of approximately 0.8 mg/kg of body weight/d (cows, 30 days each) and 0, 1.0, and 1.5 mg/kg/d (sheep, 11 days each). The cattle developed mild clinical signs of locoism, including signs of depression, lethargy, and slight intention tremors. Clinical signs of toxicosis were not observed in the sheep. Within 24 hours of initial treatment, serum alpha-mannosidase activity in cows and sheep, measured by the release of 4-methylumbelliferone from an artificial substrate, was markedly decreased to 28 and 40 micromoles of 4-methylumbelliferone/L, respectively. Mean serum alpha-mannosidase activity of control cows and sheep was 400 +/- 94 and 422 +/- 42 (mean +/- SD), respectively. In the treated animals, decreased serum alpha-mannosidase activities returned to normal or higher activities within 6 days after treatment was discontinued. Using a jack bean alpha-mannosidase assay, increased swainsonine activity (153, 209, and 381 ng/ml, respectively) was detected in the serum of cattle and of sheep in the high- and low-dose groups within 24 hours after treatment with locoweed. Swainsonine concentration remained high, with mean concentrations of 204, 432, and 395 ng/ml (cows and 2 sheep groups, respectively) during the treatment period. After treatment, swainsonine was rapidly cleared, with estimated serum half-life of 16.4, 17.6, and 20.3 hours (cows, and high- and low-dose sheep groups, respectively). Significant differences in either alpha-mannosidase activity or swainsonine concentration were not detected between the 2 groups of treated sheep. These results suggest that serum alpha-mannosidase and swainsonine values are sensitive indicators of locoweed intoxication in cattle and sheep. Furthermore, it suggests that swainsonine is rapidly absorbed, resulting in rapid inhibition of serum alpha-mannosidase activity, leading to high serum swainsonine concentration. After exposure is eliminated, swainsonine is rapidly cleared from the serum, with serum alpha-mannosidase activity returning to normal values shortly thereafter.