Assessment of Myocardial Function in the Horse 1. Theoretical and Technical Considerations

Brown, Christopher M.; Holmes, J. R.

doi:10.1111/j.2042-3306.1979.tb01356.x

Cited by 8 publications

(3 citation statements)

References 33 publications

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“…Maximal rate of rise of LV pressure is the index most frequently used to reflect myocardial contractility in horses (Brown and Holmes 1979). In this study, isoflurane was also associated with a higher LVdp/dt max than during halothane anaesthesia, also suggesting that myocardial contractility was better maintained during isoflurane anaesthesia.…”

Section: Discussionsupporting

confidence: 54%

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

Raisis

Young

Blissitt

et al. 2000

Equine Veterinary Journal

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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.

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Section: Discussionsupporting

confidence: 54%

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

Raisis

Young

Blissitt

et al. 2000

Equine Veterinary Journal

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“…Peak aortic velocity, acceleration and LVdp/dh, were demonstrated to have similar inotropic sensitivity to dobutamine infusions in a study in thoracotomised dogs (Lambert et al 1983). LVdp/dt, is the most frequently used index for assessment of myocardial contractility in horses (Brown and Holmes 1979;Muir, 1992;Wagner et al 1990). In the present study dobutamine infusion caused significant increases in dv/d&, Vm, and LVdp/d&.…”

Section: Discussionmentioning

confidence: 99%

“…Steffey and Howland (1978) showed that the equine cardiovascular system is more susceptible to the depressant effects of halothane than that of other species. The assessment of cardiac performance in horses has been restricted to measurement of cardiac output (Muir et al 1976) or intracardiac and arterial pressures (Brown and Holmes 1979). However, use of these techniques is limited to research applications due to risks associated with cardiac catheterisation (Cournand 1975;Schlipf et al 1994).…”

Section: Introductionmentioning

confidence: 99%

Feasibility of transoesophageal echocardiography for evaluation of left ventricular performance in anaesthetised horses

Young

Blissitt

Clutton

et al. 1995

Equine Veterinary Journal

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Summary Transoesophageal Doppler echocardiography was performed in 7 Thoroughbred horses anaesthetised with halothane. The procedure was performed on 4 occasions under standard conditions. On one occasion dobutamine hydrochloride was infused at 4 μg/kg/min for 20 min. Recordings of aortic blood velocity, obtained using high pulsed repetition frequency Doppler echocardiography (HPRF), were used to derive maximum acceleration (dv/dtmax), maximum velocity (Vmax), left ventricular ejection time (ET), pre‐ejection period (PEP), velocity time integral (VTI) and cardiac output (CO). The coefficient of variation and 95% confidence intervals were narrower for the Doppler variables than for those obtained from cardiac catheterisation. For each horse the anaesthetic to anaesthetic repeatability of the Doppler indices of left ventricular function, exceeded that of maximum rate of rise of left ventricular pressure (LVdp/dtmax). The horse to horse variability was significant for heart rates Vmax, dv/dtmax, and VTI. After dobutamine infusion there were significant changes in all measured variables except heart rate, VTI and CO. The % change that occurred exceeded the predicted 95% confidence intervals for single measurements in all significantly affected variables. This suggests Doppler indices of cardiac performance may be useful to assess changes in haemodynamic function. Passage of the probe into the oesophagus was not associated with serious adverse effects. Mild serous nasal discharge was visible for up to 24 h after the horses recovered from anaesthesia. Mild nasal haemorrhage occurred on 5 occasions during probe insertion. It is concluded that transoesophageal Doppler echocardiography provides a minimally invasive, continuous method for monitoring left ventricular systolic performance in anaesthetised horses.

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Disorders of the Cardiovascular System

Bonagura¹,

Reef²

2004

Equine Internal Medicine

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Assessment of Myocardial Function in the Horse 1. Theoretical and Technical Considerations

Cited by 8 publications

References 33 publications

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

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

Feasibility of transoesophageal echocardiography for evaluation of left ventricular performance in anaesthetised horses

Disorders of the Cardiovascular System

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