Plasma Concentrations and Cardiovascular Influence of Lidocaine Infusions During Isoflurane Anesthesia in Healthy Dogs and Dogs With Subaortic Stenosis

Objective—To determine the plasma concentrations and cardiovascular changes that occur in healthy dogs and dogs with aortic stenosis that are given an infusion of lidocaine during isoflurane anesthesia. Study Design—Phase 1, controlled randomized cross-over trial; Phase 2, before and after trial Animals—Phase 1, 6 healthy dogs (4 female, 2 male) weighing 23.8 ± 7.4 kg; Phase 2, 7 dogs (4 female, 3 male) with moderate to severe subaortic stenosis (confirmed by Doppler echocardiography) weighing 31.1 ± 14.5 kg. Methods—After mask induction, intubation, and institution of positive pressure ventilation, instrumentation was performed to measure hemodynamic variables. After baseline, measurement at an end-tidal isoflurane concentration of 1.9% (phase 1) or 1.85% (phase 2), a loading dose infusion of lidocaine at 400 μg/kg/min was given. Phase 1: Maintenance doses of lidocaine were administered consecutively (40, 120, and 200 μg/kg/min) after the loading dose (given for 10, 10, and 5 minutes, respectively) in advance of each maintenance concentrations. Measurements were taken at the end of each loading dose and at 25 and 35 minutes during each maintenance level. The same animals on a different day were given dextrose 5% and acted as the control. Phase 2: Dogs were studied on a single occasion during an infusion of lidocaine at 120 μg/kg/ min given after the loading dose (10 minutes). Measurements occurred after the loading dose and at 25 and 35 minutes. A blood sample for lidocaine concentration was taken at 70 minutes. Data were compared using a one-way ANOVA for phase 1, and between phase 1 and 2. Statistical analysis for phase 2 was performed using a paired r-test with a Bonferroni correction. A P value ± .05 was considered significant. Results—Phase 1: Plasma lidocaine concentrations achieved with 40, 120, and 200 μg of lidocaine/kg/min were 2.70, 5.27, and 7.17 μg/mL, respectively. A significant increase in heart rate (HR) (all concentrations), central venous pressure (CVP), mean pulmonary areterial pressure (PAP), and a decrease in stroke index (SI) (200 μg/kg/min) were observed. An increase in systemic vascular resistance (SVR) and mean PAP, and a decrease in SI also followed the loading dose given before the 200 μg/kg/min infusion. No other significant differences from the control measurements, during dextrose 5% infusion alone, were detected. Phase 2: Plasma lidocaine concentrations achieved were 5.35, 4.23, 4.23, and 5.60 μg/mL at 10, 25, 35, and 70 minutes, respectively. They were not significantly different from concentrations found in our healthy dogs at the same infusions. A significant but small increase in CVP compared with baseline was noted after the loading dose. There were no significant differences from baseline shown in all other cardiovascular data. There were no statistically significant differences in any measurements taken during the lidocaine infusion between the dogs in phase 1 and phase 2. Dogs with aortic stenosis tended to have a lower cardiac index than healthy dogs at baseline (88 v 121 mL/kg/min) and during lidocaine infusion (81 v 111 mL/kg/min). A small, statistically significant difference in systolic PAP was present at baseline. Conclusions—There does not appear to be any detrimental cardiovascular effects related to an infusion of lidocaine at 120 μg/kg/min during isoflurane anesthesia in healthy dogs or dogs with aortic stenosis. The technique used in this study resulted in therapeutic plasma concentrations of lidocaine. Clinical Relevance—Methods shown in the study can be used in clinical cases to achieve therapeutic lidocaine levels without significant cardiovascular depression during isoflurane anesthesia.     

Omasal Anatomy in New Zealand Red and Fallow Deer: An Exploratory Multivariate Analysis

We measured the weight and volume of omasae, and the number, weight and area of omasal laminae from wild fallow (Cervus dama), and wild and farmed red deer (Cervus elaphus) whose diet, as indicated by rumen content, was known. A multivariate analysis yielded two principal components, interpreted as indices of overall omasal size and laminar leafiness. The second component showed significantly greater variance in wild red deer than in farmed red or wild fallow deer. Deer feeding on a mixed diet of browse and grasses may have greater variability of omasal form than those feeding on grass alone. A relationship is derived by which the laminar area can be estimated from counts of laminae in different size classes.     

Survival in Dogs with Nasal Adenocarcinoma: 64 Cases (1981–1995)

Case records of 64 dogs with nasal adenocarcinoma were reviewed. The effects of age, gender, tumor stage, presence of metastatic lesions, and treatment method on survival time were examined. Surgery groups included rhinotomy (n = 9), transnasal curettage (n = 29), and no surgery (n = 26). Chemotherapy groups included fluorouracil-cyclophosphamide combination therapy (n = 15), mitoxantrone (n = 7), and no chemotherapy (n = 42). Fifty-three dogs received fractionated cobalt 60 radiation therapy. Surgical procedure, chemotherapy group, and stage of primary tumor were not significantly associated with survival time ( P > .05). Dogs that received radiation therapy had a significantly longer median survival time (424 days) than dogs that did not (126 days) ( P = .0001). The presence of either regional lymph node or pulmonary metastasis was associated with significantly shorter median survival time (109 days) when compared to dogs without metastases (393 days) ( P = .0125). When only dogs that had received radiation therapy were considered, neither surgical treatment nor chemotherapy group was associated with significant changes in median survival time. An alternate staging system emphasizing the presence or absence of metastases is proposed. Key words: Chemotherapy; Metastasis; Radiotherapy.     

氮、磷添加对青藏高寒草甸土壤碳氮磷化学计量特征影响的Meta分析

为了解青藏高原高寒草甸土壤碳(Carbon,C)、氮(Nitrogen,N)、磷(Phosphorus,P)化学计量特征对氮、磷添加的响应,提高养分管理水平及草地生态系统的养分平衡。本研究严格筛选出21篇文章(612项数据)进行Meta分析,通过亚组分析分析了不同施肥方式(氮添加、磷添加、氮磷添加)、不同施肥强度(轻度、中度、重度)对青藏高原草地土壤C,N,P化学计量特征的影响。研究结果表明：养分添加显著增加了青藏高原草地土壤C,N,P含量;氮添加对土壤的增加效应随施肥强度增加而增加,磷轻度施肥(20g·m^-2以下)处理、氮磷添加轻度施肥处理下的土壤C,N,P含量及化学计量比增加效果最好。本研究结果总体反映出氮、磷添加对青藏高原高寒草甸土壤产生积极影响,研究结果可为青藏高原草地生态系统的保护提供科学依据。