Ventricular Arrhythmias in Dogs With Splenic Masses

The records of 73 dogs with splenic masses were evaluated retrospectively to determine whether ventricular arrhythmias, in the absence of clinically apparent underlying heart disease, were a common clinical finding. Associated clinical, laboratory, and pathologic findings were evaluated to search for clinical predictors of ventricular arrhythmias. Age, breed, weight, sex, coagulation abnormalities, electrolyte abnormalities, and hemoabdomen were unrelated to the development of arrhythmias (p > 0.05). Anemia was associated with the presence of arrhythmias (p = 0.005). Myocardial necrosis (10/18) and metastatic hemangiosarcoma (3/18) were common myocardial histopathologic findings. Proposed causes for arrhythmias in dogs with splenic masses include myocardial metastases, tissue hypoxia secondary to anemia or hypovolemia, and local or systemic catecholamine release.     

Temporal Variability of Ventricular Arrhythmias in Boxer Dogs with Arrhythmogenic Right Ventricular Cardiomyopathy

Background: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is prevalent in the Boxer. There is little information on the temporal variability of ventricular arrhythmias within affected dogs.
Objective: To evaluate ambulatory electrocardiograms (AECG) from Boxers with ARVC for hourly variation in premature ventricular complexes (PVC) and heart rate (HR).
Animals: One hundred and sixty-two Boxer dogs with ARVC.
Methods: Retrospective, observational study of 1,181 AECGs collected from Boxer dogs at The Ohio State University from 1997 to 2004 was evaluated. The proportion of depolarizations that were PVCs was compared across each hour of the day, during six 4-hour periods of day, to the time after AECG application, and to the maximum and minimum HR.
Results: A lower proportion of PVCs was noted during early morning (midnight to 0400 hours) as compared with the morning (0800–1200 hours) and late (1600–2000 hours) afternoon ( P = .012). There was no increase in PVC proportion in the 1st hour after AECG application as compared with all other hours of the day ( P = .06). There was poor correlation between maximum (ρ= 0.19) and minimum (ρ= 0.12) HR and PVC proportion.
Conclusions and Clinical Importance: The likelihood of PVC occurrence in Boxer dogs with ARVC was relatively constant throughout the day, although slightly greater during the hours of 0800–1200 and 1600–2000. A biologically important correlation with HR was not apparent. The role of autonomic activity in the modulation of electrical instability in the Boxer with ARVC requires further study.     

Ventricular Arrhythmias in Dogs Undergoing Splenectomy: A Prospective Study

Fifty dogs undergoing splenectomy for splenic masses (n = 40), torsion of the splenic pedicle (n = 5), and immune-mediated disease (n = 5) were evaluated preoperatively and postoperatively for ventricular arrhythmias and the relationship between ventricular arrythmia and splenic disease. The ability of 1 -minute electrocardiograms recorded every 6 hours (ECGs/q6hr) to detect ventricular arrythmia was compared with continuous 48-hour Holter monitoring. Based on continuous Holter monitoring, splenectomized dogs had a high incidence (22 of 50) of rapid ventricular tachycardia. The incidence of rapid ventricular tachycardia was significantly higher in dogs with ruptured splenic masses (16 of 23) than without rupture (1 of 17) ( P < .001). When the results of ECG/q6hr were compared with the results of continuous Holter monitoring, ECG/q6hr was normal in 29% (4 of 14) of dogs with rapid ventricular tachycardia at > 3,000 ventricular extrasystoles (VE)/hr; 50% (4 of 8) of dogs with rapid ventricular tachycardia at 1,000 to 3,000 VE/hr and 100% (6 of 6) of dogs with 10 to 300 VE/hr without rapid ventricular tachycardia. Although dogs undergoing splenectomy had a high incidence of ventricular arrythmias, one-minute ECGs/q6h were unreliable for detection of ventricular arrythmias even when high-frequency extrasystoles occurred.     

Neuromuscular Effects of Doxacurium Chloride in Isoflurane-Anesthetized Dogs

Objective—To determine the neuromuscular effects of doxacurium chloride and to construct a dose-response curve for the drug in isoflurane-anesthetized dogs. Design—Randomized, controlled trial. Animals—Six healthy, adult, mixed-breed dogs (five female, one male) weighing 24.8 ° 2.8 kg. Methods—Anesthesia was induced with isoflurane in oxygen and maintained with 1.9% to 2.3% end-tidal isoflurane concentration. Paco₂ was maintained between 35 and 45 mm Hg with mechanical ventilation. Mechanomyography was used to quantitate the evoked twitch response of the paw after supramaximal train-of-four stimulation of the superficial peroneal nerve. After baseline values were recorded, the dogs received one of three doses of doxacurium (2.0, 3.5, 4.5 μg/kg of body weight) or a saline placebo intravenously in random order. All dogs received all treatments with at least 7 days between studies. After drug administration, the degree of maximal first twitch depression compared with baseline (T,%) was recorded. Dose-response relations of doxacurium were plotted in log dose-probit format and analyzed by linear regression to determine effective dose (ED₅₀ and ED₉₀) values for doxacurium. Results—The median log dose-probit response curve showed good data correlation (r= .999) with estimates of the ED₅₀ (2.1 μg/kg) and ED₉₀ (3.5 μg/kg) for doxacurium in isoflurane-anesthetized dogs. Mean ± SD values for T₁% (first twitch tension compared with baseline) at maximal depression after drug administration, onset (time from drug administration to maximal depression of T₁%), duration (time from maximal depression of T₁% to 25% recovery of T₁%), and recovery (time from 25% to 75% recovery of T₁%) times were 92%± 4%, 40 ± 5 minutes, 108 ± 31 minutes, and 42 ± 11 minutes for dogs treated with 3.5 μg/kg of doxacurium and 94%± 7%, 41 ± 8 minutes, 111 ± 33 minutes, and 37 ± 10 minutes for dogs treated with 4.5 μg/kg of doxacurium. Conclusion and Clinical Relevance—We conclude that doxacurium is a long-acting neuromuscular blocking agent with a slow onset of action. Doxacurium can be used to provide muscle relaxation for long surgical procedures in isoflurane-anesthetized dogs. Interpatient variability, particularly of duration of drug action, may exist in the neuromuscular response to the administration of doxacurium in dogs.     

Hemodynamic Effects of Epidural Ketamine in Isoflurane-Anesthetized Dogs

Objective —The purpose of this study was to determine the hemodynamic effects of epidural ketamine administered during isoflurane anesthesia in dogs. Study Design —Prospective, single-dose trial. Animals —Six healthy dogs (five males, one female) weighing 25.3 ± 3.88 kg. Methods —Once anesthesia was induced, dogs were maintained at 1.5 times the predetermined, individual minimum alveolar concentration (MAC) of isoflurane. Dogs were instrumented and allowed to stabilize for 30 minutes before baseline measurements were recorded. Injection of 2 mg/kg of ketamine in 1 mL saline/4.5 kg body weight was then performed at the lumbosacral epidural space. Hemodynamic data were recorded at 5, 10, 15, 20, 30, 45, 60, and 75 minutes after epidural ketamine injection. Statistical analysis included an analysis of variance (ANOVA) for repeated measures over time. All data were compared with baseline values. A P < .05 was considered significant. Results —Baseline values ±standard error of the mean (X ± SEM) for heart rate, mean arterial pressure, mean pulmonary artery pressure, central venous pressure, pulmonary capillary wedge pressure, cardiac index, stroke index, systemic vascular resistance, pulmonary vascular resistance, and rate-pressure product were 108 ± 6 beats/min, 85 ± 10 mm Hg, 10 ± 2 mm Hg, 3 ± 1 mm Hg, 5 ± 2 mm Hg, 2.3 ± 0.3 L/min/m², 21.4 ± 1.9 mL/beat/m², 3386 ± 350 dynes/sec/cm⁵, 240 ± 37 dynes/sec/cm⁵, and 12376 ± 1988 beats/min±mm Hg. No significant differences were detected from baseline values at any time after ketamine injection. Conclusions —The epidural injection of 2 mg/kg of ketamine is associated with minimal hemodynamic effects during isoflurane anesthesia. Clinical Relevance —These results suggest that if epidural ketamine is used for analgesia in dogs, it will induce minimal changes in cardiovascular function.     

Cardiovascular Effects After Epidural Injection of Xylazine in Isoflurane-Anesthetized Dogs

The cardiovascular effects following epidural injection of xylazine or isotonic saline during isoflurane anesthesia were assessed in six healthy dogs. Dogs were anesthetized with isoflurane in O₂ and maintained at 2.0% end-tidal concentration. Ventilation was controlled to maintain PaCO₂ at 35 to 45 mm Hg. The dorsal pedal artery was cannulated for measurement of arterial blood pressure (AP)(systolic AP, mean AP, diastolic AP) and for blood sample collection. Arterial pH and blood gas tensions (PaO₂ and PaCO₂) were determined. Cardiac output was measured by thermodilution. The electrocardiogram (ECG), heart rate (HR), core body temperature, central venous pressure (CVP), mean pulmonary AP, and end-tidal isoflurane concentration (ETISO) and CO₂ tension (ETCO₂) were monitored. Systemic vascular resistance (SVR), arterial HCO₂ concentration, base balance, and cardiac index (CI) were calculated. After baseline measurements were taken, either xylazine (0.2 mg/kg) in 5 mL isotonic saline or 5 mL of isotonic saline was injected into the lumbosacral epidural space. Data were then recorded at 5, 15, 30, 45, 60, 75, 90, 105, and 120 minutes after epidural injection. Data were analyzed by two-way analysis of variance (ANOVA) for repeated measures. When significant differences were encountered, mean values were compared using Bonferroni's test. The level of significance was set at P <.05. Mean values for diastolic AP decreased at 90 and 120 minutes compared with the mean value at 15 minutes after epidural injection of xylazine. No differences were detected at any time or between treatments for HR, systolic AP, mean AP, CVP, CI, SVR, mean pulmonary AP, temperature, ETCO₂, ETISO, arterial pH, PaCO₂, PaO₂, plasma bicarbonate concentration, or base balance. Results of this study indicate that epidural injection of xylazine (0.2 mg/kg) is associated with minimal cardiovascular side effects during isoflurane anesthesia in mechanically ventilated dogs.     

Association of Tricuspid Annular Plane Systolic Excursion with Survival Time in Boxer Dogs with Ventricular Arrhythmias

Background

Tricuspid annular plane systolic excursion (TAPSE) is a useful estimate of right ventricular function in humans. Reference intervals for dogs have been generated, but the value of measuring TAPSE in other diseases, or investigating the association between TAPSE and outcome, is unknown.

Hypothesis

TAPSE is lower in Boxer dogs with ≥50 VPCs/24 h on Holter than in dogs with fewer ventricular ectopics, and lower TAPSE is associated with a shorter survival time.

Animals

Fifty Boxer dogs that presented for investigation of syncope or suspected arrhythmogenic right ventricular cardiomyopathy (ARVC) at a veterinary teaching hospital (2004–2011).

Methods

Retrospective study. Clinical records, Holter, and echocardiographic data were reviewed. TAPSE was measured in a blinded manner on stored echocardiographic cine‐loops using anatomic M‐mode. Outcome information was obtained and death was classified as cardiac or noncardiac. Survival analysis was performed using Kaplan‐Meier curves and Cox proportional hazards models.

Results

TAPSE was lower in Boxers with ≥50 VPCs/24 h (13.9 ± 4.04 mm) than Boxers with <50 VPCs/24 h (16.8 ± 3.21 mm; P < .001). TAPSE <15.1 mm was associated with shorter cardiac survival time in all dogs (P = .004) and also in dogs without left ventricular dysfunction (P = .035). When controlling for other variables, including ventricular tachycardia on Holter and left ventricular systolic dysfunction, multivariable analysis showed that TAPSE remained an independent predictor of time to cardiac death (HR >4.09, 95%CI 1.15–16.9, P < .029).

Conclusions and Clinical Importance

TAPSE offers prognostic value for Boxer dogs, including those with apparently normal systolic function and ≥50 VPCs/24 h on Holter analysis.     

Familial Ventricular Arrhythmias in Boxers

The purposes of this study were to evaluate families of Boxers with ventricular arrhythmias to determine whether this disorder is a familial trait and, if so, to determine the mode of inheritance. Eighty-two Boxers were evaluated by physical examination, electrocardiogram, echocardiogram, and 24-hour ambulatory electrocardiogram. Dogs were considered affected if at least 50 premature ventricular complexes (PVCs) were observed during a 24-hour period. All dogs were at least 6 years of age at evaluation. Complete cardiovascular examinations were performed on dogs from 6 extended families. The 2 most complete pedigrees were used to determine the pattern of inheritance. The number of PVCs observed during a 24-hour period in affected dogs ranged from 112 to 4,894 (mean +/- SD, median; 1,309 +/- 2,609, 1,017). The number of PVCs observed during a 24-hour period in the unaffected dogs ranged from 0 to 16 (7 +/- 10, 12). Pedigree evaluation was performed to determine pattern of inheritance. An autosomal dominant pattern was determined to be most likely because a sex predisposition was not observed, affected individuals were observed in every generation, and 2 affected individuals produced unaffected offspring. We conclude that familial ventricular arrhythmias is inherited as an autosomal dominant trait in some Boxers.     

Anatomy and Cholinergic Innervation of the Sinus paranalis in Dogs

Conventional methods have been used to study the general configuration of the wall of the Sinus paranalis in dogs. Apocrine tubular glands, elastic fibres and smooth-muscle fibres are the more significant elements of the wall, together with the epithelium and connective tissue. By means of the immunohistochemical method described in this paper, the results provide histochemical evidence for the presence of an AChE-positive reaction, and supposedly cholinergic nerve fibres in the wall of the dog anal sacs, mainly associated with subepithelial smooth muscle, vessels, and glands.     

Respiratory Depressant and Skeletal Muscle Relaxant Effects of Low-Dose Pancuronium Bromide in Spontaneously Breathing, Isoflurane-Anesthetized Dogs

Objective—To assess and compare the respiratory depressant and skeletal muscle relaxant effects of two low doses of a nondepolarizing neuromuscular blocker, pancuronium bromide. To determine if a “low dose” of pancuronium bromide can produce selective skeletal muscle relaxation in extraocular muscles sufficient to perform intraocular surgery while sparing or minimizing depression of muscles of ventilation. Study Design—Blinded, randomized crossover, placebo controlled study. Animals—Six healthy, adult mongrel dogs weighing 20.8 ±1.9 kg. Methods—Spontaneously breathing, isoflurane-anesthetized dogs received 0.02 mg/kg pancuronium bromide, intravenously (IV), (high dose [HD]), 0.01 mg/kg pancuronium bromide, IV, (low dose [LD]), or saline placebo IV in a blinded, randomized crossover study. Indices of patient ventilation including tidal volume (Vt), respiratory rate (RR), and minute ventilation (V_E) were recorded throughout the study period. Serial arterial blood gas analyses were performed at timed intervals. Neuromuscular blockade of skeletal muscle was assessed at timed intervals with train-of-four stimulus/response ratios. Eye position scores, based on the degree of ocular rotation from a neutral gaze axis, were assigned by an ophthalmologist who was blinded to the treatment given. Results—Vt and V_E in HD dogs decreased by 82% from baseline after administration of pancuronium bromide. Similarly, Vt and V_E in LD dogs decreased 40% and 55%, respectively. Decreased ventilation in HD dogs corresponded with significant (P< .05) neuromuscular blockade, as indicated by train-of-four ratio less than 75% between 0 and 60 minutes. Eye position scores in HD and LD dogs were suitable for intraocular surgery between 0 and 60 minutes. Eye position scores in five of six control dogs were unsuitable for intraocular surgery at any time period. Conclusions—LD dogs experienced only transient, mild to moderate respiratory depression compared with HD dogs, which experienced prolonged, moderate to severe respiratory depression. Both LD and HD dogs acquired and maintained eye position scores suitable for intraocular surgery between 0 to 60 minutes. A “low dose” of pancuronium bromide, which would provide adequate extraocular muscle relaxation while minimizing ventilatory depression, was not identified. Clinical Relevance—All patients receiving any dose of neuromuscular blocking agents should be closely monitored and receive ventilatory assistance as needed.     

利多卡因、布吡卡因行犬硬膜外阻滞时的药代动力学

为研究利多卡因(lidocaine)和布吡卡因(bupivacaine)行硬膜外阻滞时的药代动力学特征,将16只健康犬随机分成2组(n=8),硬膜外阻滞时按体质量分别注入2%利多卡因6mg/kg和0.5%布吡卡因2mg/kg,在注药后的3、5、8、10、15、20、30、40、50、60、75、90、120、150、180min分别采取股动脉血,用气相色谱法测定血药浓度,比较2组药代动力学指标。结果表明,利多卡因和布吡卡因的药-时曲线均符合一室开放模型,t1/2ka分别为(3.55±0.73)min和(7.76±0.38)min,tpeak分别为(18.8±2.2)min和(35.6±1.5)min,Cmax分别为(4.67±0.37)mg/L和(1.38±0.08)mg/L,AUC分别为(739±73)μg.mL-1.min和(366±45)μg.mL-1.min,CL分别为(12.2±4.6)mL/min和(5.5±0.67)mL/min。     

Effect of Ketorolac Tromethamine on Atracurium-Induced Neuromuscular Blockade in Anesthetized Dogs

Objective —The purpose of this study was to determine the effect of ketorolac tromethamine or placebo on the neuromuscular blockade induced by an infusion of atracurium in isoflurane-anesthetized dogs. Design —Randomized, controlled trial. Animals —Six healthy, adult mixed-breed dogs (five female, one male) weighing 24.8 ± 2.8 kg. Methods —Dogs were studied on two occasions with a minimum of 7 days between studies. Dogs were induced with 5% isoflurane in oxygen and maintained with 1.6 ± minimum alveolar concentration (MAC) end-tidal isoflurane. Neuromuscular blockade was assessed using the train of-four response. Once 50% depression of the first twitch (T₁) was achieved, the atracurium infusion rate was held constant for 30 minutes. Then ketorolac, 0.5 mg/kg, or the same volume of placebo (0.9% sodium chloride solution) was administered intravenously and the atracurium infusion maintained for an additional 60 minutes. Before and at 2, 5, 10, 15, 30, and 60 minutes after ketorolac or placebo, the percent depression of T₁ and the fourth twitch to the first twitch (T₄/T₁) ratio were recorded. The atracurium infusion was discontinued and the time for T₁ to recover from 50% to 75% of its original value was recorded. At 75% T₁, edrophonium, 0.5 mg/kg intravenously, was administered to antagonize the residual blockade. Results —There was no significant difference in T₁%, T₄/T₁ ratio, or recovery time after ketorolac administration compared with placebo. Conclusions —Ketorolac, 0.5 mg/kg intravenously, has no significant effect on either atracuriuminduced neuromuscular blockade or recovery time for T₁ in isoflurane-anesthetized dogs. Clinical Relevance —The concurrent use of atracurium should not be a contraindication for the administration of ketorolac for intraoperative or postoperative analgesia.     

Ventricular Arrhythmias during Race Recovery in Standardbred Racehorses and Associations with Autonomic Activity

Background: A lack of information on normal heart rhythm at maximal effort hampers investigation of poor performance and sudden death in Standardbred racing. Hypothesis/Objective: To characterize rhythm variations during scheduled racing in clinically normal Standardbred horses. Animals: Two hundred and eighty‐eight Standardbred horses competing in 40 scheduled races at a Southern Ontario racetrack. Methods: Observational study, convenience sampling: Heart rhythm was monitored by ECG from harnessing to postrace recovery and assessed visually and by examining heart rate intervals. Rhythm variations were used as response variables in multivariate analysis of race records detailing signalment, race, and race outcome. Results: Monitoring involved 345 individual horse or race events. Occasional, isolated premature cycles, only, occurred during the race. Postrace, sudden cardiac slowing (punctuated deceleration [PD]) appeared in 42 events (12.2%). Only premature ventricular complexes were exhibited in 40 events postrace (11.6%), whereas 55 (15.9%) exhibited complex ventricular arrhythmias (CVA) including torsades‐like polymorphic ventricular tachycardia, 34.5% of these being closely associated with PD (odds ratio = 8). Predispositions to CVA were found for horses parked at the 1/2 mile (odds ratio = 3), and trotters breaking in the stretch (odds ratio = 38). Horses spontaneously reverted to sinus rhythm and no sudden death events were encountered. Conclusions and Clinical Importance: Arrhythmias occur frequently in racing Standardbreds during cardiac deceleration, often associated with sudden, rapid increases in vagal tone. Circumstances imposing unusual demand and racing at the trot appear to predispose. Findings provide insight into possible mechanisms of sudden death.     

Genetic Analysis of Ventricular Arrhythmia in Young German Shepherd Dogs

Background: Ventricular arrhythmias (VA) and sudden death are inherited in German Shepherd Dogs (GSDs).
Objectives: To estimate the genetic parameters (heritabilities and correlations) of 3 traits of VA (single premature ventricular complexes (PVCs), 2 consecutive PVCs (couplets), and 3 or more consecutive PVCs—ventricular tachycardia [VT]).
Animals: Three hundred and ninety-eight GSDs.
Methods: Prospective, observational, case control study. Dogs were phenotyped by 24-hour ambulatory ECG from 6 to 45 weeks of age. Edited ECG records included the number of incidents of (1) single PVCs, (2) couplets, and (3) VT.
Results: A data set of 1,239 Holter records from 398 GSDs was used to estimate genetic variables. Phenotypic correlations for affectedness (binarily coded 0/1) of the 3 traits ranged from 0.55 to 0.74, whereas correlations for severity (continuous values of 24-hour VA counts) ranged from 0.26 to 0.39. Estimates of genetic correlation among the severity traits were 0.06 to 0.27. Estimated heritabilities were 0.54, 0.54, and 0.46 for affectedness and 0.33, 0.69, and 0.69 for severity of PVCs, couplets, and VT, respectively. Month and year of birth and age at ECG recording had significant effects on all 3 traits. Season of ECG recording had a significant effect on the number of single PVCs, but not couplets or incidents of VT. Age of onset differed, with single PVCs appearing an average of 4 days earlier than couplets and VT.
Conclusion: These results imply a strong genetic component for this disease but suggest that differences in the 3 traits should be taken into consideration in studies to identify the underlying genes.     

Magnetic Resonance Imaging of Right Ventricular Morphology and Function in Boxer Dogs with Arrhythmogenic Right Ventricular Cardiomyopathy

Background: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a myocardial disease characterized by fibrofatty replacement of the right ventricle and ventricular tachyarrhythmias, reported most commonly in the Boxer dog. Although ARVC is characterized as a myocardial disease, the impact of the disease on the function of the right ventricle has not been well studied.
Objective: To noninvasively evaluate the function and anatomy of the right ventricle in Boxer dogs with ARVC.
Animals: Five adult Boxer dogs with ARVC and 5 healthy size-matched hound dogs.
Methods: Magnetic resonance imaging was performed on an ECG-gated conventional 1.5-T scanner using dark blood imaging and cine acquisitions. Images were evaluated by delineation of endocardial right and left ventricular contours in the end-diastolic and end-systolic phases of each slice. Right and left end-systolic and end-diastolic volumes were generated using Simpson's rule and ejection fraction was calculated. Images were evaluated for right ventricular (RV) aneurysms and wall motion abnormalities. Spin echo images were reviewed for the presence of RV myocardial fatty replacement or scar.
Results: RV ejection fraction was significantly lower in Boxers with ARVC compared with the controls (ARVC 34%± 11 control 53%± 10, P < .01). There was an RV aneurysm in 1 dog with ARVC but not in any of the controls. RV myocardial gross fatty changes were not observed in dogs of either group.
Conclusions and Clinical Importance: These findings could be interpreted to suggest that arrhythmias and myocardial dysfunction precede the development of morphological abnormalities in dogs with ARVC.     

Possible Late Potentials in 4 Dogs with Sustained Ventricular Tachycardia

Signal-averaged electrocardiograms (SAEKGs) were performed on 4 dogs with sustained ventricular tachycardia. Quantitative and qualitative analyses of SAEKGs were consistent with the presence of late potentials. Two of the 4 dogs subsequently died suddenly, and ventricular tachycardia and ventricular fibrillation were observed in 1 dog. High-frequency QRS durations (75–90 milliseconds), duration of low amplitude (less than 40 μV) signals during the terminal QRS complex (LAS₄₀) (28–40 milliseconds), root mean square voltages of the terminal 40 milliseconds of the QRS complex (RMS₄₀) (124–6.5 μV), and root mean square voltages of the terminal 30 milliseconds of the QRS complex (RMS₃₀) (13–2.1 μV) differed from results obtained in 68 of 70 control dogs. Echocardiographic data suggested dilated cardiomyopathy in 2 dogs and the cause of the arrhythmia in 2 dogs was not determined. The SAEKG may be a useful adjunct in identifying a subset of dogs with ventricular tachyarrhythmias that are at high risk for sustained ventricular tachycardia and sudden death. The sensitivity, specificity, and predictive accuracies of the technique remain to be determined.     

药物对不同品种犬的影响

伊(阿)维菌素是属于新型大环内酯类高效生物抗生素类杀虫、杀螨剂,其中B la为主要活性成分。伊(阿)维菌素通过剌激神经传递介质y-氨基丁酸的释放,干扰节肢动物正常的神经生理活动起到杀虫作用,而人和其他哺乳动物外周神经传递过程无此物质参与,因而对人及哺乳动物很安全。伊(阿)维菌素是大分子药物,一般不能通过血脑屏障进入脑细胞中,但柯利犬或幼犬因为血脑屏障发育不完善,药物得以进入脑细胞,从而造成中毒(这也是柯利犬容易对其他药物产生过敏中毒的原因)。虽然伊维菌素驱绦虫效果非常好,但副作用也比较大,仅限于成犬严格按照剂量使用,柯利牧羊犬禁用。     

Influence of Veterinary Care on the Urinary Corticoid: Creatinine Ratio in Dogs

Physical and emotional stresses are known to increase the production and secretion of glucocorticoids by the adrenal cortex in both humans and experimental animals. The urinary corticoid: creatinine (C:C) ratio is increasingly used as a measure of adrenocortical function. In this study we investigated whether a visit to a veterinary practice for vaccination, a visit to a referral clinic for orthopedic examination, or hospitalization in a referral clinic for 1.5 days resulted in increases of the urinary C: C ratio in pet dogs. In experiment 1, owners collected voided urine samples from 19 healthy pet dogs at specified times before and after taking the dogs to a veterinary practice for yearly vaccination. In experiment 2, 12 pet dogs were evaluated in a similar way before and after an orthopedic examination at a referral clinic. In experiment 3, 9 healthy pet dogs were hospitalized for 1.5 days and urine samples were collected before, during, and after this stay. Basal urinary C:C ratios in all experiments ranged from 0.8 to 8.3 × 10^-6. In experiment 1, the urinary C:C ratio after the visit to the veterinary practice ranged from 0.9 to 22.0 × 10^-6. Six dogs had a significantly increased urinary C:C ratio (responders), but in 5 of these dogs the ratio was ≤10 × 10^-6 In experiment 2. 8 of 12 dogs responded significantly with urinary C:C ratios ranging from 3.1 to 27.0 × 10^-6. In experiment 3, 8 of 9 dogs had significantly increased urinary C:C ratios, ranging from 2.4 to 24.0 × 10^-6, in some or all urine samples collected during hospitalization. In 4 dogs urinary C:C ratios 12 hours after hospitalization were still significantly higher than the initial values. Thus, a visit to a veterinary practice, an orthopedic examination in a referral clinic, and hospitalization can be considered stressful conditions for dogs. A large variation occurs in response, and in individual dogs the increases in urinary C:C ratios can exceed the cutoff level for the diagnosis of hyperadrenocorticism. Therefore, urine samples for measurement of the C: C ratio in the diagnosis of hyperadrenocorticism should be collected in the dog's home environment, to avoid the influence of stress on glucocorticoid secretion.