A proposed rescue transesophageal echocardiographic protocol for anesthetized dogs

OBJECTIVE

To describe the acquisition and pitfalls of a 3-view transesophageal echocardiography (TEE) protocol in anesthetized, dorsally recumbent dogs.

ANIMALS

8 beagles, 1 to 2 years old, 7.4 to 11.2 kg.

METHODS

Dogs were anesthetized, mechanically ventilated, and placed in dorsal recumbency. A TEE probe was advanced, and 3 views were performed: midesophageal 4-chamber and long axis (ME 4C and ME LAX) and caudal esophageal short axis (CE SAX) at the level of the papillary muscles. Probe insertion depth, flexion, omniplane angle, and image acquisition time were recorded. Two observers assessed 24 video clips each and identified anatomical structures.

RESULTS

The ME 4C and ME LAX were obtained at 35 (30 to 40) cm insertion depth, omniplane at 0° and 103° (90 to 116), respectively. Views were obtained in ≤30 seconds once the TEE was in the cervical esophagus. Left-sided structures were identified in all cases, whereas right-sided structures were not always simultaneously obtained in the ME 4C, requiring further probe manipulation. All structures were identified on ME LAX. CE SAX was obtained at 40 (35 to 45) cm, omniplane at 0°, and in 15 (10 to 90) seconds. A true SAX view (circular left ventricle at the level of papillary muscles) could not be obtained in all dogs.

CLINICAL RELEVANCE

A 3-view TEE protocol using core views as those described in humans may be applicable to dogs under general anesthesia and in dorsal recumbency. The CE SAX view at the level of the papillary muscles appears more difficult to obtain with consistency than midesophageal views.

Quantitative assessment of left ventricular volume and function by transthoracic and transesophageal echocardiography, ultrasound velocity dilution, and gated magnetic resonance imaging in healthy foals

OBJECTIVE

To compare measurements of left ventricular volume and function derived from 2-D transthoracic echocardiography (2DE), transesophageal echocardiography (TEE), and the ultrasound velocity dilution cardiac output method (UDCO) with those derived from cardiac MRI (cMRI) in healthy neonatal foals.

ANIMALS

6 healthy 1-week-old Standardbred foals.

PROCEDURES

Foals were anesthetized and underwent 2DE, TEE, and cMRI; UDCO was performed simultaneously with 2DE. Images acquired by 2DE included the right parasternal 4-chamber (R4CH), left apical 4- and 2-chamber (biplane), and right parasternal short-axis M-mode (M-mode) views. The longitudinal 4-chamber view was obtained by TEE. Measurements assessed included left ventricular end-diastolic volume (LVEDV), end-systolic volume (LVESV), ejection fraction, stroke volume (LVSV), cardiac output (CO), and cardiac index (CI). Bland-Altman analyses were used to compare measurements derived from biplane, R4CH, and M-mode images and UDCO with cMRI-derived measurements. Repeatability of measurements calculated by 3 independent reviewers was assessed by the intraclass correlation coefficient.

RESULTS

Compared with cMRI, all 2DE and TEE modalities underestimated LVEDV and LVESV and overestimated ejection fraction, CO, and CI. The LVSV was underestimated by the biplane, R4CH, and TEE modalities and overestimated by UDCO and M-mode methods. However, the R4CH-derived LVSV, CO, and CI were clinically comparable to cMRI-derived measures. Repeatability was good to excellent for measures derived from the biplane, R4CH, M-mode, UDCO, and cMRI methods and poor for TEE-derived measures.

CONCLUSIONS AND CLINICAL RELEVANCE

All assessed modalities yielded clinically acceptable measurements of LVEDV, LVESV, and function, but those measurements should not be used interchangeably when monitoring patient progress.

Double-outlet right ventricle in a Vietnamese potbellied pig

A 6-month-old, neutered male, Vietnamese potbellied pig presented for evaluation of exercise intolerance and intermittent episodes of exertional cyanosis. Initial diagnostic evaluation revealed arterial hypoxemia. Transthoracic echocardiogram revealed double-outlet right ventricle (DORV) and a subaortic ventricular septal defect. Agitated saline contrast study confirmed the entry of saline contrast from the right ventricle into both pulmonary artery and aorta. Due to deterioration of clinical status, the patient was euthanized 3 months later. Gross necropsy examination was performed confirming the congenital cardiac defects noted on the echocardiogram. To the authors knowledge, this is the first case report of DORV in a Vietnamese potbellied pig.

Transesophageal Echocardiography Examination in Ailuropoda melanoleuca

OBJECTIVE

Cardiac function analysis for Ailuropoda melanoleuca, also called giant panda, with transthoracic echocardiography has several limitations, such as limited probe position area and poor echo window. We want to determine the feasibility of transesophageal echocardiography (TEE) for cardiac examination in Ailuropoda melanoleuca.

METHODS

Eight-year-old male Ailuropoda melanoleuca was anesthetized by intramuscular ketamine and followed by inhalation isofl urane with spontaneous respiration. TEE probe was inserted through mouth. Comprehensive examinations were done by two-dimensional (2D), Doppler method, 3D zoom and 3D full volume mode for their cardiac evaluation.

RESULTS

The structure of heart was similar to human. We found mild mitral regurgitation. Right ventricle and pulmonary artery were free of any organic lesions. We did comprehensive multiplane examination by American Society of Echocardiography/Society of Cardiovascular Anesthesia guideline, but transgastric (TG) and deep TG view were not approachable. 3D reconstruction offered high quality image and quantitative calculations. Complete examinations took less than 30 minutes. There was no significant hemodynamic change during probe insertion, and no oropharyngeal trauma certifi ed by dentist.

CONCLUSIONS

TEE is a reasonable semi-invasive tool for cardiac function evaluation. Though some anatomical limitations prohibited comprehensive 2D views, improvements such as 3D images help to give detailed cardiac examination.

Clinical, echocardiographic and advanced imaging characteristics of 13 dogs with systemic-to-pulmonary arteriovenous fistulas

OBJECTIVES

The objective is to describe the clinical, radiographic, echocardiographic and angiographic findings in dogs with systemic-to-pulmonary arteriovenous fistula (SPAVF).

ANIMALS

Thirteen medical records of client-owned dogs with a diagnosis of SPAVF were reviewed/analysed.

METHODS

This is a retrospective study of case records. Thoracic radiography, transthoracic echocardiography (TTE), transesophageal echocardiography (TEE), three-dimensional TEE, intracardiac echocardiography, fluoroscopy-guided or computed tomography (CT) angiography were carried out.

RESULTS

Based on the TTE, SPAVF was identified in seven of the included dogs. In eight cases, TEE and angiography were both performed and confirmed the diagnosis. Computed tomography angiography was performed in three dogs. A case was diagnosed by TEE alone, another one by three-dimensional TEE and the latter by intracardiac echocardiography.

CONCLUSIONS

Transthoracic echocardiography identified seven cases of SPAVF, while definitive diagnosis in the remaining dogs required selective angiography or computed tomography angiography.

Bovine tricuspid endocarditis as a cause of increased serum concentration of cardiac troponins

A Holstein cow presented for weight loss and anorexia had tachycardia, heart murmur, and a chronic inflammatory process. Serum cardiac troponin I was increased at 3.52 ng/mL. Transthoracic echocardiography revealed a thickened tricuspid valve and comet-tail artifacts compatible with gas in the affected area. This report suggests that serum cardiac troponin I may be increased in bacterial endocarditis in cattle.

Minimally Invasive Determination of Cardiac Output by Transthoracic Bioimpedance, Partial Carbon Dioxide Rebreathing, and Transesophageal Doppler Echocardiography in Beagle Dogs

Minimally invasive cardiac output was determined using transthoracic bioimpedance (BICO), partial carbon dioxide rebreathing (NICO) and transesophageal Doppler echocardiography (TEECO) and compared to thermodilution (TDCO) in 6 beagle dogs. The dogs were 2 years old, weigh between 9.1-13.0 kg and were anesthetized with nitrous oxide-oxygen-sevoflurane. All dogs were administered a neuromuscular blocking drug and artificially ventilated during anesthesia. Thirty paired measurements of TDCO and each non-invasive method were collected during low, intermediate, and high values of cardiac output achieved by varying the depth of anesthesia and the administration of dobutamine. Cardiac output values ranged from 1.10-2.50 L/min for BICO compared to 0.81-4.88 L/min for TDCO; 0.70-2.60 L/min for NICO compared to 0.89-4.45 L/min for TDCO; and 0.59-4.37 L/min for TEECO compared to 0.57-4.15 L/min for TDCO. The limits of agreement and percentage error were -0.58 +/- 1.56 L/min and +/- 75.4% for BICO, -1.04 +/- 1.08 L/min and +/- 56.0% for NICO, and 0.03 +/- 0.26 L/min and +/- 12.3% for TEECO compared to TDCO. In conclusion, TEECO provided the best agreement to TDCO in sevoflurane anesthetized beagle dogs.

TRANSESOPHAGEAL ECHOCARDIOGRAPHY OF THE LEFT VENTRICULAR OUTFLOW TRACT, AORTIC VALVE AND ASCENDING AORTA IN BOXER DOGS WITH HEART MURMURS

The study was aimed at evaluating the anatomy of the left ventricular outflow tract, aortic valve, and ascending aorta by means of multiplane transesophageal echocardiography in Boxer dogs with left basilar heart murmurs and at comparing two-dimensional (2D) transthoracic to transesophageal echocardiography for the diagnosis of subaortic stenosis in this breed. Twenty-eight Boxers were included in the study and allocated to four groups according to physical and routine transthoracic 2D and Doppler echocardiography findings: group A--dogs with low grade (I-II/VI) heart murmurs without overt evidence of aortic stenosis (14 dogs); group B--dogs with type 1 subaortic stenosis (seven dogs); group C--dogs with type 2 subaortic stenosis (five dogs); group D--dogs with type 3 subaortic stenosis (two dogs). Anatomic lesions were not discovered by transesophageal echocardiography in dogs belonging to group A. Transesophageal imaging confirmed the type of subaortic stenosis, as graded by transthoracic echocardiography, in diseased animals (groups BCD). Morphologic information obtained by transesophageal echocardiography in Boxer dogs was similar to that obtained by transthoracic echocardiography.

An initial application of transesophageal Doppler echocardiography in experimental small animal models

This study examined whether an intracardiac echocardiography catheter could be used for transesophageal echocardiography (TEE) examinations in normal rats, and intraoperative TEE in small animal models of disease. The study used 30 Sprague-Dawley normal rats, 10 rats undergoing coronary artery ligation, and 10 rats with experimentally induced mitral regurgitation. The rats were anesthetized with isoflurane and intubated. An intracardiac echocardiographic catheter was inserted into the esophagus. M-mode, 2-dimensional, and Doppler studies were performed in multiple views. TEE probe insertions were successful in all animals. Intraoperative TEE was safely performed in the rat models of myocardial infarction or mitral regurgitation. Mitral regurgitation was well assessed using color Doppler and pulmonary venous flow. This study demonstrates that TEE (including intraoperative TEE) can be safely performed in rats using an intracardiac echocardiographic catheter. It provides a new approach to the assessment of cardiac function and valvular regurgitation in small animals.

The effects of halothane and isoflurane on cardiovascular function in laterally recumbent horses

BACKGROUND

Experimental studies in adult horses have shown that general anaesthesia maintained with isoflurane is associated with less depression of cardiovascular function compared with halothane anaesthesia. Adverse effects of intermittent positive-pressure ventilation (IPPV) have also been demonstrated. Nevertheless, the haemodynamic effects of these agents and the effects of differing modes of ventilation have not been assessed during clinical anaesthesia in horses undergoing surgery.

METHODS

The haemodynamic effects of isoflurane or halothane anaesthesia during spontaneous or IPPV were studied non-invasively in 32 laterally recumbent horses undergoing elective surgery. Indices of cardiac function and measurements of femoral arterial blood flow and resistance were recorded using transoesophageal and transcutaneous Doppler echocardiography, respectively. Arterial pressure was measured directly using a facial artery catheter.

RESULTS

Cardiac index (CI) was significantly higher during isoflurane anaesthesia than during halothane anaesthesia and was also higher during spontaneous ventilation with isoflurane. CI decreased significantly over time and an inverse relationship was observed between CI and mean arterial pressure (MAP). Horses with higher MAP had a significantly lower CI. During isoflurane anaesthesia, femoral arterial blood flow was significantly higher in both pelvic limbs compared with halothane anaesthesia, and flow in the lower limb was significantly higher during spontaneous ventilation than during IPPV. No significant change in femoral blood flow was observed over time.

CONCLUSION

The effects of anaesthetics and mode of ventilation on cardiovascular function recorded under surgical conditions in horses are similar to those reported under experimental conditions. However, in contrast with previous experimental studies, CI progressively decreased over time regardless of agent used or mode of ventilation employed.

[Transesophageal echocardiography: principles, technique and potential indications in veterinary medicine]

Transesophageal echocardiography (TEE) is a recent ultrasound technique using an endoscopic transducer to image the heart from within the esophagus. TEE avoids the anatomical structures that may affect the quality of the conventional transthoracic echocardiography. The quality of cardiovascular images obtained with TEE is therefore superior to transthoracic views. The potential indications of TEE in veterinary medicine include analysis of specific abnormalities (thrombosis, aneurism, cardiac tumors), cardiac monitoring during anesthesia or catheterization, and evaluation of cardiovascular surgical procedures.

Observer-dependent variability of quantitative clinical endpoints: the example of canine echocardiography

The objective of this study was to determine the intra- and inter-observer variability of echocardiographic measurements in dogs. Four observers with different levels of experience in echocardiography performed 192 echocardiographic examinations of six dogs on four different days. The lowest within- and between-day coefficients of variation (CV) (%) were 13.8 and 5.2 for the right ventricle in diastole, 8.9 and 4.5 for the interventricular septal thickness in diastole (6.3 and 7.0 in systole), 7.7 and 9.4 for the left ventricular free-wall thickness in diastole (8.1 and 5.2 in systole), 3.1 and 5.0 for the left ventricular end-diastolic diameter (6.2 and 7.0 for end-systolic diameter), 10.2 and 10.8 for the left ventricular shortening fraction, and 8.2 and 9.8 for the left atrium/aorta ratio, respectively. Most of these lowest CVs were observed by the two most experienced observers. Conversely, all maximum values were obtained with the two less experienced observers. These differences in observer-dependent variability may considerably influence the minimum number of animals required to detect a treatment-associated change in echocardiographic variables.

Familial aortic aneurysm in Leonberg dogs

A thoracic aortic aneurysm was diagnosed in a 6-month-old male Leonberg dog by use of radiography, transthoracic and transesophageal echocardiography, and magnetic resonance imaging. The aneurysm was associated with a twisted ascending aorta and dilatation of several other thoracic arteries (pulmonary trunk, brachiocephalic trunk, and left subclavian artery). Histologic examination of the aorta revealed cystic medial necrosis, with disruption of the elastic network, collagen fibers, and the muscle glycoprotein fibrillin-1. The dam and sire of the dog and 8 littermates were examined by use of transthoracic echocardiography. The sire and 1 male littermate also had an aneurysm of the ascending aorta. To the authors' knowledge, this is the first report of familial aortic aneurysm in dogs.

Comparison of the incidence of residual shunting between two surgical techniques used for ligation of patent ductus arteriosus in the dog

OBJECTIVE

To compare the incidence of residual patent ductus arteriosus (PDA) flow after ligation using 2 different dissection techniques: a standard dissection and a method described by Jackson and Henderson.

STUDY DESIGN

A randomized, prospective study.

ANIMALS

Thirty-five dogs admitted for surgical correction of a left to right shunting PDA.

METHODS

Dogs were randomly assigned: 19 to a standard dissection technique (group S) and 16 to the Jackson and Henderson dissection group (group JH).

RESULTS

Gender ratio, age at surgery, and diameter of the ductus were not statistically different between groups. Breed distribution was also similar. Because 1 dog had fatal intraoperative hemorrhage, only 34 dogs were available for residual flow comparisons. Twenty-one percent of group S dogs had residual flow compared with 53% in group JH. Whereas no intraoperative complications occurred in group S, 3 were encountered in group JH.

CONCLUSIONS

The incidence of residual flow was higher when the Jackson and Henderson dissection was used for PDA ligation compared with a standard method of dissection. This was probably because of entrapment of loose connective tissue within the medial aspect of the ligature, impeding complete closure of the ductus.

CLINICAL RELEVANCE

Ideal PDA closure should result in no residual ductal flow to prevent possible adverse long-term sequelae, such as recanalization and infective endocarditis.

Comparison of canine heartworm removal rates using flexible alligator forceps guided by transesophageal echocardiography and fluoroscopy

Fluoroscopy (FS)- or transesophageal echocardiography (TEE)-guided heartworm removal was carried out using flexible alligator forceps to compare the rate of worm removal. As a result, the worm removal rates were similar between the two procedures. However, the TEE-guided procedure does not involve radiation exposure, and facilitates observation of worms in the cardiac chamber and pulmonary artery. Therefore, the TEE-guided procedure is thought to be more useful than the FS-guided procedure in clinical setting.

Left ventricular, systemic arterial, and baroreflex responses to ketamine and TEE in chronically instrumented monkeys

Effects of prescribed doses of ketamine five minutes after application and influences of transesophageal echocardiography (TEE) on left ventricular, systemic arterial, and baroreflex responses were investigated to test the hypothesis that ketamine and/or TEE probe insertion alter cardiovascular function. Seven rhesus monkeys were tested under each of four randomly selected experimental conditions: (1) intravenous bolus dose of ketamine (0.5 ml), (2) continuous infusion of ketamine (500 mg/kg/min), (3) continuous infusion of ketamine (500 mg/kg/min) with TEE, and (4) control (no ketamine or TEE). Monkeys were chronically instrumented with a high fidelity, dual-sensor micromanometer to measure left ventricular and aortic pressure and a transit-time ultrasound probe to measure aortic flow. These measures were used to calculate left ventricular function. A 4-element Windkessel lumped-parameter model was used to estimate total peripheral resistance and systemic arterial compliance. Baroreflex response was calculated as the change in R-R interval divided by the change in mean aortic pressure measured during administration of graded concentrations of nitroprusside. The results indicated that five minutes after ketamine application heart rate and left ventricular diastolic compliance decreased while TEE increased aortic systolic and diastolic pressure. We conclude that ketamine may be administered as either a bolus or continuous infusion without affecting cardiovascular function 5 minutes after application while the insertion of a TEE probe will increase aortic pressure. The results for both ketamine and TEE illustrate the classic "Hawthorne Effect," where the observed values are partly a function of the measurement process. Measures of aortic pressure, heart rate, and left ventricular diastolic pressure should be viewed as relative, as opposed to absolute, when organisms are sedated with ketamine or instrumented with a TEE probe.

A comparison of the haemodynamic effects of isoflurane and halothane anaesthesia in horses

The purpose of this study was to compare the haemodynamic effects of equipotent isoflurane and halothane anaesthesia. Six adult horses were investigated on two separate occasions at least 4 weeks apart. On both occasions anaesthesia was induced by ketamine 2.2 mg/kg bwt given 5 min after i.v. administration 100 microg/kg bwt romifidine. Anaesthesia was maintained either by halothane or isoflurane (end-tidal concentrations 0.9-1.0% and 1.3-1.4%, respectively). Horses were ventilated by intermittent positive pressure to maintain PaCO2 between 40-50 mmHg. Haemodynamic variables were measured using catheter-mounted strain gauge transducers in the left and right ventricle, aorta, and right atrium. Cardiac output (CO), velocity time integral (VTI), maximal aortic blood flow velocity (Vmax) and acceleration (dv/dt(max)), left ventricular pre-ejection period (PEP) and ejection time (ET) were measured from aortic blood flow velocity waveforms obtained by transoesophageal Doppler echocardiography. Flow velocity waveforms were recorded from the femoral arteries and veins using low pulse repetition frequency Doppler ultrasound. Time-averaged mean velocity (TAV), velocity of component a (TaVa), velocity of component b (TaVb) and early diastolic deceleration slope (EDDS) were measured. Pulsatility index (PI) and volumetric flow were calculated. Microvascular blood flow was measured in the left and right semimembranosus muscles by laser Doppler flowmetry. Maximal rate of rise of LV pressure (LVdp/dt(max)), CO, Vmax, dv/dt(max), ET, VTI were significantly higher at all time points during isoflurane anaesthesia compared to halothane anaesthesia. Pre-ejection period and diastolic aortic blood pressure were significantly less throughout isoflurane anaesthesia compared to halothane. Isoflurane anaesthesia was associated with significantly lower systemic vascular resistance than halothane anaesthesia. Femoral arterial and venous blood flow were significantly higher and EDDS and PI were significantly lower during isoflurane anaesthesia compared to halothane anaesthesia. In addition during both halothane and isoflurane anaesthesia, femoral arterial flow was higher and EDDS and PI lower in the left (dependent) artery compared to the right (nondependent) artery. This study supports previous work demonstrating improved left ventricular systolic function during isoflurane compared to halothane anaesthesia. This improvement was still evident after premedication with a potent-long acting alpha2-adrenoreceptor agonist, romifidine, and induction of anaesthesia with ketamine. There was also evidence of increased hindlimb blood flow during isoflurane anaesthesia. However, there were differences observed in flow between the left and right hindlimb during maintenance of anaesthesia with each agent, suggesting that there were differences in regional perfusion in anaesthetised horses caused by factors unrelated to agents administered.

Cardiac output measured by lithium dilution, thermodilution, and transesophageal Doppler echocardiography in anesthetized horses

OBJECTIVE

To assess the suitability of lithium dilution as a method for measuring cardiac output in anesthetized horses, compared with thermodilution and transesophageal Doppler echocardiography.

ANIMALS

6 horses (3 Thoroughbreds, 3 crossbreeds).

PROCEDURE

Cardiac output was measured in 6 anesthetized horses as lithium dilution cardiac output (LiDCO), thermodilution cardiac output (TDCO), and transesophageal Doppler echocardiographic cardiac output (DopplerCO). For the LiDCO measurements, lithium chloride was administered i.v., and cardiac output was derived from the arterial lithium dilution curve. Sodium nitroprusside, phenylephrine hydrochloride, and dobutamine hydrochloride were used to alter cardiac output. Experiments were divided into 4 periods. During each period, 3 LiDCO measurements, 3 DopplerCO measurements, and 3 sets of 3 TDCO measurements were obtained.

RESULTS

70 comparisons were made between LiDCO, DopplerCO, and triplicate TDCO measurements over a range of 10 to 43 L/min. The mean (+/- SD) of the differences of LiDCO - TDCO was -0.86 +/- 2.80 L/min; LiDCO = -1.90 + 1.05 TDCO (r = 0.94). The mean of the differences of DopplerCO - TDCO was 1.82 +/- 2.67 L/min; DopplerCO = 2.36 + 0.98 TDCO (r = 0.94). The mean of the differences of LiDCO - DopplerCO was -2.68 +/- 3.01 L/min; LiDCO = -2.53 + 0.99 DopplerCO (r = 0.93).

CONCLUSIONS AND CLINICAL RELEVANCE

These results indicate that lithium dilution is a suitable method for measuring cardiac output in horses. As well as being accurate, it avoids the need for pulmonary artery catheterization and is quick and safe to use. Monitoring cardiac output during anesthesia in horses may help reduce the high anesthetic mortality in this species.

A clinical study on velocity patterns of pulmonary venous flow in canine heartworm disease

In this study, we evaluated methods of determining the velocity patterns of pulmonary venous flow (PVF) in dogs and then investigated the relationship of the patterns to cardiac functions in heartworm disease (HD) by transthoracic echocardiography (TTE). The results revealed that there was a good correlation between PVF patterns determined by transesophageal echocardiography (TEE) and TTE in animals lying on their left sides. The measurement of S and D wave velocities (PVS and PVD) by TTE was shown to allow clinical determination of the velocity patterns of PVF in dogs. The HD groups showed significant increases in PVS and PVD, and S and D wave time-velocity integrals (S-TVI and D-TVI) of the right cranial lobe PVF, when compared with the normal group, as determined by TTE (P<0.05). In contrast, the HD groups produced significant decreases in PVD and D-TVI of the right caudal lobe PVF compared with the normal group (P<0.05), and a significant increase in the ratio of S-TVI to (S-TVI + D-TVI) (P<0.05). It is, therefore, suggested that measurement of the velocity patterns of the right cranial and caudal lobe PVF could be one method of assessing the stages of obstructive lesions in the pulmonary artery.

Surgical repair of an atrial septal defect in a juvenile Sumatran orangutan (Pongo pygmaeus sumatraensis)

A systolic heart murmur was auscultated in a 2-yr-old female Sumatran orangutan (Pongo pygmaeus sumatraensis) with a slower than expected growth rate. Cardiac ultrasound revealed an 11-mm atrial septal defect. Cardiac catheterization confirmed the diagnosis. Surgical repair was performed during cardiopulmonary bypass using a pericardial patch. The bypass pump was primed with human albumin and donor orangutan whole blood of a compatible type. Hematuria occurred shortly after the initiation of cardiopulmonary bypass. Successful repair was immediately confirmed with transesophageal ultrasonography. The animal was extubated shortly after returning to spontaneous ventilation but had to be reintubated 4 hr later due to tachypnea and decreased SpO2. Additional extubation attempts failed, necessitating continuous positive pressure ventilation, monitoring, and intensive care environment. Thoracic radiographs suggested adult respiratory distress syndrome. The animal required 14 days of intensive care before extubation of the trachea was successful. After 4 wk of isolation, the orangutan was successfully reintroduced to its family group.

Effects of respiratory cycle on pulmonary venous flow and cardiac cycle on pulmonary venous diameter of dogs: a transesophageal echocardiography study

We investigated 12 anesthetized normal dogs using transesophageal echocardiography to understand the effects of respiration on the pulmonary venous flow. Additionally, we observed whether the diameter of the pulmonary vein changes with the heart beat. The pulsed Doppler wave form of pulmonary venous flow predominantly demonstrated two backward flows, with one peak occurring during ventricular systole and another during ventricular diastole. Sometimes a small forward flow occurred during left atrial contraction. In comparison with expiration, the peak velocity and velocity-time integral of the flow wave under inspiration occurred during both systole and diastole were significantly smaller. The diameter of the pulmonary vein decreased during left atrial contraction and increased during left ventricular systole and diastole.

Temporal effects of an infusion of dobutamine hydrochloride in horses anesthetized with halothane

OBJECTIVE

To evaluate temporal hemodynamic effects of dobutamine in horses anesthetized with halothane.

ANIMALS

8 adult Thoroughbreds.

PROCEDURE

Anesthesia was induced by i.v. administration of romifidine and ketamine and maintained using halothane in oxygen. After 60 minutes, dobutamine was administered i.v. for 60 minutes at 4 micrograms/kg of body weight/min. Measurements of left ventricular function were obtained by transesophageal echocardiography and cardiac catheterization.

RESULTS

Mean, systolic, diastolic, aortic, pulmonary arterial, and left and right ventricular end-diastolic and systolic pressures, maximal rate of increase of intraventricular pressure (LVdp/dtmax), maximum acceleration (dv/dtmax) and velocity (Vmax) of aortic blood flow, cardiac output, and left ventricular velocity time integral were significantly increased, whereas left ventricular pre-ejection period and ejection time significantly decreased. Cardiac output, LVdp/dtmax, Vmax, and dv/dtmax increased throughout infusion. Heart rate was significantly less after 10 minutes and significantly greater at 60 minutes than before infusion. Supraventricular tachycardia developed in 2 horses. Cardiac output, LVdp/dtmax, Vmax, dv/dtmax, left ventricular and aortic systolic pressures, and mean aortic pressure had not returned to control values 30 minutes after infusion was discontinued.

CONCLUSIONS

At this dosage, dobutamine did not achieve peak effect on many hemodynamic variables within 40 minutes of commencing infusion, and effects of 60-minute infusion persisted after infusion was discontinued.

CLINICAL RELEVANCE

Dobutamine has a hemodynamic profile suited to treatment of low cardiac output in anesthetized horses; however, sustained administration may be associated with supraventricular tachycardia and a protracted time to peak effect.

Haemodynamic effects of a sixty minute infusion of dopamine hydrochloride in horses anaesthetised with halothane

To describe the haemodynamic effects of a 60 min infusion of dopamine 4 microg/kg bwt/min during halothane anaesthesia, 7 mature Thoroughbred horses were studied. The infusion began 1 h after induction of anaesthesia by romifidine (100 microg/kg) and ketamine (2.2 mg/kg bwt). Throughout the period of dopamine infusion and for 30 min after its discontinuation, the horses were ventilated by intermittent positive pressure to maintain PaCO2 between 4.6-5.4 KPa. Inspired halothane concentration was adjusted to maintain an end tidal halothane concentration of 0.9%. Haemodynamic variables were measured using intracardiac strain gauge transducers sited in the left and right ventricle, aorta, and pulmonary artery. Left ventricular pressure was differentiated to obtain maximal rate of increase of intraventricular pressure (LVdp/dtmax). Transoesophageal Doppler echocardiography was performed to measure maximum aortic blood flow velocity (vmax) and acceleration (dv/dtmax), left ventricular velocity time integral (vTI) and cardiac output (CO), and left ventricular pre-ejection period (PEP) and ejection time (ET). Measurements were made during the 60 min infusion, and for 30 min after the infusion was discontinued. Infusion of dopamine 4 microg/kg/min significantly decreased mean aortic pressure, while left and right ventricular end-diastolic pressure and mean pulmonary artery pressure remained unchanged. There was a small, but significant, increase in heart rate during dopamine infusion. Maximum acceleration of aortic blood flow, CO and vTI were also significantly increased by dopamine infusion. Maximal rate of increase of intraventricular pressure (LVdp/dtmax) was significantly decreased 10 min after commencing infusion, but then returned to baseline for the remainder of the study. Left ventricular pre-ejection period (PEP) decreased during dopamine infusion whilst ejection time (ET) significantly increased. All measured variables except LVET had returned to baseline values within 30 min of discontinuing the infusion. This study demonstrated beneficial effects of dopamine infusion upon left ventricular systolic function. However, the therapeutic value of the drug is likely to be limited in clinical anaesthesia due to the simultaneous falls in arterial blood pressure which accompany its administration.

Transesophageal ultrasonography of the normal canine mediastinum

The mediastinum of eight normal research dogs was examined by transesophageal ultrasonography with a 5 MHz frequency transducer to establish a baseline for future use of this new imaging modality as a diagnostic tool. Each examination consisted of 360 degree scans in both transverse and sagittal planes from the thoracic inlet to the esophageal hiatus. Dissections of four of these research dogs were then performed to confirm transesophageal ultrasonography findings. Transesophageal ultrasonography of the mediastinum was a good imaging modality for the evaluation of the heartbase, the major cranial mediastinal vessels, the descending aorta, and occasionally part of the azygos vein. Anatomic orientation was best obtained by beginning the examination at the heart base. Lymph nodes and smaller caliber vessels could not be distinguished from surrounding tissues; however, Doppler ultrasound was useful for identifying the smaller vessels. Although a 5 MHz frequency transducer is preferred for transesophageal echocardiography, a higher frequency transducer would improve the resolution of the images of small near-field structures and may be more appropriate for mediastinal imaging.

Cardiovascular evaluation of lowland gorillas

OBJECTIVE

To design a diagnostic protocol that uses appropriate techniques, including ultrasonography, to assess cardiovascular health and detect primary cardiac diseases in gorillas and to establish a database of reference values for cardiac measurements in clinically normal gorillas.

DESIGN

Prospective study.

ANIMALS

5 adult male lowland gorillas from 11 to 18 years old.

PROCEDURE

A complete cardiac evaluation was performed on anesthetized gorillas, including physical examination, thoracic radiography, electrocardiography, echocardiography, blood pressure determination, CBC, serum biochemical analyses, and serologic assay for viral diseases. Standard cardiac measurements were made from images collected during ultrasonography.

RESULTS

Cardiac measurements derived from ultrasonographic images were consistent with those considered normal in human beings. Results of other diagnostic tests were also considered normal.

CLINICAL IMPLICATIONS

Cardiac disease is the primary cause of mortality in old captive gorillas. The technique used here provided excellent evaluation of cardiac function. Use of these techniques will allow early detection of cardiac disease, making treatment or medical management possible.

Biplane transesophageal echocardiography in the normal cat

Eight healthy, adult cats were examined with biplane transesophageal echocardiography (TEE). Cats were sedated with a combination of diazepam and propofol and were examined using a 5 mm x 80 cm pediatric biplane TEE probe. Consistent images were obtained at three imaging depths within the esophagus. The caudal position provided satisfactory short-axis images of the left ventricle and heart base. The middle position provided the best long-axis views of the left atrium, left ventricle, and aorta and allowed Doppler examination of transmitral left ventricular inflow. The cranial position provided satisfactory imaging of the aorta and pulmonary artery and allowed Doppler examination of right ventricular and left ventricular outflow. Biplane TEE provides an additional method of imaging the feline heart which is complimentary to other imaging techniques and the images obtained were similar to those reported for dogs. Although TEE offers a slight advantage over transthorcic imaging for Doppler examination, the quality of the images of heart base structures was not as consistently superior to transthoracic images in cats as reported in dogs.

Temporal effects of an infusion of dopexamine hydrochloride in horses anesthetized with halothane

OBJECTIVE

To evaluate the hemodynamic effects of a 60-minute infusion of dopexamine in horses anesthetized with halothane.

ANIMALS

7 adult Thoroughbreds.

PROCEDURE

Measurements of left ventricular function obtained by transesophageal Doppler echocardiography and cardiac catheterization.

RESULTS

Infusion of dopexamine (4 micrograms/kg of body weight/min) significantly increased heart rate, cardiac output, maximal rates of increase and decrease of left ventricular pressure, and maximal acceleration and maximal velocity of aortic blood flow. Left ventricular ejection time significantly increased, and pre-ejection period decreased during the infusion. Cardiac output, maximal rate of increase of left ventricular pressure, and maximal acceleration continued to increase as the infusion progressed. Right ventricular end-diastolic pressure was significantly decreased after 20 minutes of infusion and decreased progressively throughout the remaining time of infusion. Many hemodynamic variables, including right ventricular end-diastolic pressure, had not returned to control values 30 minutes after the infusion was discontinued. A number of undesirable adverse effects were observed in horses receiving dopexamine infusion; during administration, profuse sweating occurred in every horse. In 6 horses, recovery from anesthesia was associated with excitement and violent shivering. Colic developed in 2 horses within 3 hours of recovery.

CONCLUSIONS

Dopexamine (4 micrograms/kg/min) does not achieve a peak effect on many hemodynamic variables within a short period of commencing administration, and the effects of infusion may persist for extended periods after drug administration is discontinued.

CLINICAL RELEVANCE

Dopexamine has a hemodynamic profile suited to treatment of low cardiac output in anesthetized horses; however, at the dosage rate studied (4 micrograms/kg/min), its administration was associated with a number of undesirable adverse effects which could preclude its clinical use.

Effects of isoflurane versus halothane on myocardial contractility in rabbits: assessment with transthoracic two-dimensional echocardiography

The effects of isoflurane versus halothane on cardiac contractility were evaluated by two-dimensional (2D) transthoracic echocardiography in rabbits. The relationship between the left ventricular end-systolic wall stress (LVESWS) and the velocity of heart rate corrected circumferential fibre shortening (Vcfc) was used. Arterial blood pressure, heart rate, left ventricular pressure and transthoracic 2D echocardiogrphic data were determined at 1 MAC (minimum alveolar concentration) of halothane or isoflurane, both with 50% nitrous oxide. Drug-induced changes in pre- and afterload were performed in all study animals to assess the left ventricular contractile response over a wide range. LVESWS and Vcfc were calculated on videotape recorded M-mode tracings. Mean heart rate and arterial blood pressure were not significantly different between the two groups. Myocardial contractility under isoflurane/nitrous oxide anaesthesia was significantly higher than under halothane/nitrous oxide anaesthesia at 1 MAC. The results of the present study confirm data obtained from humans and other animal species and suggest that, in rabbits, myocardial contractility is best preserved by inhalation of isoflurane. Isoflurane should therefore be preferred over halothane, especially in cases of prolonged anaesthetic procedures.

Changes in cardiopulmonary variables and platelet count during anesthesia for total hip replacement in dogs

Changes in cardiopulmonary function and platelet count were determined in 22 dogs of various breeds that underwent total hip replacement with cemented femoral prostheses. In 11 dogs (group I) polymethylmethacrylate (PMMA) was inserted without venting the reamed and lavaged femoral canal. In a second group of 11 dogs (group II) a urethral catheter (ID: approximately 2.7 mm) was placed into the medullary cavity before the insertion of PMMA. The application of PMMA resulted in a decrease in end-tidal carbon dioxide tension (PETCO2) until 5 minutes after insertion of bone cement. Increases in arterial to end-tidal pCO2 gradient [P(a-ET)CO2] and physiological dead space (VD/VT) were recorded between 2 minutes before and 5 minutes after insertion of PMMA in 12 dogs. A significant decrease in platelet count occurred in both groups of dogs. Decreases in arterial pO2 (PaO2), arterial/alveolar oxygen tension ratio (PaO2/PAO2), and percent O2 saturation of hemoglobin in arterial blood (SaO2) were not statistically significant. No significant differences could be detected between data obtained from both groups of dogs. An increase in femoral intramedullary pressure caused by the insertion of PMMA and subsequent pulmonary microembolism by medullary contents has been considered the most likely cause for changes in pulmonary function. The lack of statistically significant differences in cardiopulmonary variables and platelet count between the two groups of dogs could have been related to inefficient pressure reduction by the method used.