Impact of preanaesthetic echocardiography on the planned anaesthetic management of cats

ObjectiveTo assess the impact of preanaesthetic echocardiography on the subsequent intended anaesthetic management plan in cats with incidental clinical findings that may indicate cardiac disease.Study designClinical study involving cats undergoing echocardiography and subsequent anaesthesia.AnimalsA total of 40 client-owned cats.MethodsEchocardiography was performed in conscious cats and the information was used to plan anaesthesia or sedation. An information sheet including relevant history, temperament, body condition score, clinical examination findings, current medication and results of any relevant tests such as haematology, biochemistry or Doppler blood pressure measurement was sent to three specialist anaesthetists and virtual case management plans were designed for each cat in two steps: step 1) anaesthetists were unaware of echocardiography results; and step 2) anaesthetists were aware of echocardiography results. In the second step the anaesthetists documented any changes to their original management plan, as either ‘step-up’ or ‘step-down’.ResultsOf the 40 cats, 26 had murmurs, four had a gallop rhythm, four had both findings and six had other findings. Pathology of potential haemodynamic significance was found on echocardiography in 23 cats, 17 of which anaesthetists had correctly identified as having disease before echocardiography. A proportion of cats with murmurs were subsequently deemed to have no significant pathology after echocardiography. Echocardiography findings in these cases were: dynamic left ventricular outflow tract obstruction (DLVOTO) without hypertrophy; DLVOTO without hypertrophy + dynamic right ventricular outflow tract obstruction (DRVOTO); DRVOTO; valvular dysplasia; normal. In a median of 26/40 (range 16–38) of cases, the anaesthetic plan was changed after provision of further information; in 15/40 (8–20) cases, this was a ‘step-up’ in care and in eight/40 (6–23) it was a ‘step-down’ in care. In cases with atrial enlargement (left atrium to aortic ratio of >1.6) and deemed at risk of cardiac failure, alpha-2 agonist use changed considerably with availability of echocardiography findings.Conclusionand clinical relevance Where there are abnormal cardiac findings on clinical examination in cats, echocardiography is required to accurately assess anaesthetic risk . The availability of echocardiographic information positively influences anaesthetic management.     

线粒体动力学平衡对心脏结构与功能的影响

心脏是一个高耗能、高耗氧的器官,其正常收缩及电信号的正常传导也需大量能量供应,因此心肌细胞含有大量线粒体。正常生理状态下,线粒体在细胞内的数量、形态和功能是相对稳定的。当机体内细胞能量产生不足或两个独立的线粒体存在不同的缺陷时,线粒体会受到Mfn1/2和OPA1的调控而发生融合,发生融合后线粒体基质含量相互混合形成一个功能完善的新的线粒体,此过程即为线粒体融合。为维持线粒体DNA及线粒体膜电位的稳定,线粒体受到Drp1及其受体的调控而发生分裂,分裂可使受损的线粒体DNA及去极化的线粒体膜在分裂时聚集到一个子线粒体中,并通过泛素化-蛋白酶系统或自噬作用消除,从而维持线粒体的正常功能。线粒体融合与分裂是一个连续波动的过程,被认为是维持线粒体和细胞正常功能和形态的关键过程。近年来研究发现,心肌细胞线粒体的融合与分裂失衡会引起自身形态和功能的紊乱,进而损害心脏结构和功能。因此,维持心肌细胞的稳态需要线粒体分裂和融合之间的动态平衡,而维持线粒体的动态平衡则需要介导线粒体融合与分裂相关的动力蛋白。作者对参与线粒体融合及分裂过程的关键蛋白的功能进行了综述,同时讨论了线粒体动力学平衡对心脏结构与功能的影响,以期为后期的研究提供一定理论参考。     

Effects of dobutamine on cardiovascular function and oxygen delivery in standing horses

Dobutamine is routinely used to improve cardiovascular function in anaesthetized horses. However, dobutamine in conscious horses is insufficiently investigated. Ten research horses that were already instrumented for a preceding trial were included into the study. Cardiovascular variables were recorded and blood samples taken after instrumentation (Baseline), before starting dobutamine and after 10 min of dobutamine infusion (2 µg kg⁻¹ min⁻¹). A significant increase in systemic blood pressure, mean pulmonary artery pressure and right atrial pressure, and a decrease in heart rate were observed with dobutamine compared with baseline measurements. Arterial and mixed venous haemoglobin and oxygen content, as well as mixed venous partial pressure of oxygen increased. No significant changes in cardiac output, stroke volume, systemic vascular resistance, arterial partial pressure of oxygen, or oxygen consumption, delivery and extraction ratio were detected. Concluding, dobutamine increased systemic blood pressure without detectable changes in stroke volume, cardiac output or systemic vascular resistance in conscious horses.     

Evaluation of platelet function in dogs with cardiac disease using the PFA‐100 platelet function analyzer

Background: Cardiac disease has the potential to alter platelet function in dogs. Evaluation of platelet function using the PFA‐100 analyzer in dogs of multiple breeds and with a broad range of cardiac conditions would help clarify the effect of cardiac disease on platelets. Objectives: The objective of this study was to assess differences in closure time (CT) in dogs with cardiac disease associated with murmurs, when compared with that of healthy dogs. Methods: Thirty‐nine dogs with cardiac murmurs and turbulent blood flow as determined echocardiographically were included in the study. The dogs represented 23 different breeds. Dogs with murmurs were further divided into those with atrioventricular valvular insufficiency (n=23) and subaortic stenosis (n=9). Fifty‐eight clinically healthy dogs were used as controls. CTs were determined in duplicate on a PFA‐100 analyzer using collagen/ADP cartridges. Results: Compared with CTs in the control group (mean±SD, 57.6±5.9 seconds; median, 56.5 seconds; reference interval, 48.0–77.0 seconds), dogs with valvular insufficiency (mean±SD, 81.9±26.3 seconds; median, 78.0 seconds; range, 52.5–187 seconds), subaortic stenosis (71.4±16.5 seconds; median, 66.0 seconds; range, 51.5–95.0 seconds), and all dogs with murmurs combined (79.6±24.1 seconds; median, 74.0 seconds; range, 48.0–187 seconds) had significantly prolonged CTs (P<.01). Conclusions: The PFA‐100 analyzer is useful in detecting platelet function defects in dogs with cardiac murmurs, most notably those caused by mitral and/or tricuspid valvular insufficiency or subaortic stenosis. The form of turbulent blood flow does not appear to be an important factor in platelet hypofunction in these forms of cardiac disease.     

M-MODE AND DOPPLER ECHOCARDIOGRAPHIC FINDINGS IN NORMAL FERRETS SEDATED WITH KETAMINE HYDROCHLORIDE AND MIDAZOLAM

M-mode and Doppler echocardiographic values were obtained from 30 normal adult ferrets (14 neutered females, 13 neutered males, 3 intact males) sedated with an intramuscular combination of ketamine hydrochloride and midazolam. Routine M-mode measurements of the left and right ventricle, left atrium (LA) and aorta (AO) and Doppler measurements of aortic and pulmonic outflow, and mitral inflow were recorded. The following values were calculated: LA:AO diameter, ratio of peak E: peak A wave velocity (E:A ratio) for mitral inflow, and stroke volume (SV), cardiac output (CO) and cardiac index (CI) for both pulmonary and aortic outflow tracts. Maximal aortic velocities (AOmax) and velocity-time integral values (AO VTI) were significantly less than corresponding pulmonary outflow tract values (PAmax, PA VTI) but there was no difference in calculated values for SV, CO or CI. Calculated CO values were in the range expected based on the size of the species. Difficulties in aligning the aortic outflow tract for Doppler imaging may make pulmonary outflow Doppler values more consistent for use in estimating volume flow in ferrets.     

THE EFFECTS OF ROTATION ON THE RADIOGRAPHIC APPEARANCE OF THE CANINE CARDIAC SILHOUETTE IN DORSAL RECUMBENCY

Cardiac mensuration was done on thoracic radiographs of Beagles to determine the effects of rotation on the cardiac silhouette in dorsal recumbency. As the thorax became more rotated, surfaces of the heart not normally seen were projected, making interpretation of cardiac changes unreliable. A positioning standard based on the relationship of the dorsal spinous processes to the vertebral body was developed. If the tips of the dorsal spinous processes were within the bounds of the vertebral bodies, the radiographs were suitable for cardiac interpretation. If the tips of the dorsal spinous processes were outside the bounds of the vertebral bodies, there was enough rotation to make interpretation unreliable. A microcomputer, digitizer pad, and a BASIC language program were used to input, store, and calculate the various cardiac mensuration parameters.     

USE OF FIRST-PASS NUCLEAR ANGIOCARDIOGRAPHY TO DETECT LEFT-TO-RIGHT CARDIAC SHUNTS IN THE HORSE

First-pass nuclear angiocardiography was performed on 13 normal horses and 5 horses with confirmed left-to-right ventricular septal defects. Two methods of analyzing the ensuing pulmonary time-activity histograms for shunt recirculation through the lungs were evaluated: (1) pulmonary-to-systemic blood flow ratio (QP:QS), based on gamma variate modeling of the lung histogram, and (2) a simple count-ratio method (C2:C1). Normal values were QP:QS=1.17±0.04 and C2:C1=0.40±0.07. Values for the five horses with left-to-right shunts were QP:QS=2.94±0.13 and C2:C1=0.76±0.11. Both parameters showed significant differences (unpaired t -test; p <0.005) between the two groups, although separation was better with QP:QS.     

The efficacy and safety of external biphasic defibrillation in toy breed dogs

Objective: To evaluate the efficacy and safety of biphasic (BP) defibrillation in toy breed dogs (<5 kg of body weight).
Design: Prospective, clinical experimental study.
Setting: Veterinary teaching hospital.
Animals: Five dogs (pilot study) and 10 dogs (comparison study of biphasic versus monophasic defibrillation).
Measurements and main results: The efficacy of defibrillation was compared by estimating E80 (80% probability of successful defibrillation) after biphasic (BP) and monophasic (MP) defibrillations. The E80 for BP defibrillation was 7.24±1.33 J (2.24±0.41 J/kg) and 10.24±1.34 J (3.18±0.12 J/kg) for MP defibrillation. BP waveform required 30% less shock energy for a successful defibrillation. In order to compare the safety of defibrillation, we evaluated changes in cardiac biomarkers, electrocardiogram, echocardiographical left ventricular index, and aortic pressure during and after BP and MP defibrillation. All dogs treated by either BP or MP defibrillation survived. Pulseless electrical activity occurred in 2 of 5 dogs during MP defibrillation. The levels of cardiac biomarkers were elevated and sustained for longer periods in the MP defibrillation group. Electrocardiographic changes (e.g., QT prolongation, the time to return to an isoelectric ST segment after shocks) were more severe and longer in the MP defibrillation group. In addition, overall left ventricular cardiac performance was severely depressed in the MP group compared with the BP group.
Conclusion: Our findings suggest that BP defibrillation is more effective and safer than MP defibrillation. We determined the acceptable shock energy to be 2–4 J/kg for toy breed dogs.