A comparison of the haemodynamic effects of isoflurane and halothane anaesthesia in horses.
Abstract: 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.
Publication Date: 2000-08-22 PubMed ID: 10952381DOI: 10.2746/042516400777032282Google Scholar: Lookup
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- Comparative Study
- Journal Article
Summary
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This study examines the differences in haemodynamic effects on adult horses when using two different types of anaesthesia, isoflurane and halothane. The findings show that isoflurane anaesthesia produced an overall improvement in left ventricular systolic function and increased hindlimb blood flow when compared to halothane anaesthesia.
Research Methodology
- The study involved six adult horses each undergoing two separate anaesthesia sessions with a gap of at least four weeks in between to avoid any possible overlap effects.
- Both anaesthesia sessions were induced using a combination of ketamine and romifidine, with the difference being the substance used for maintaining anaesthesia. In one session halothane was used, in the other isoflurane.
- Horses were given controlled ventilation to keep the arterial carbon dioxide pressure within a certain range.
- A number of haemodynamic parameters were measured through various methods such as Doppler echocardiography, Doppler ultrasound, and laser Doppler flowmetry. The parameters included factors like cardiac output, blood flow velocity, pulsatility index, and microvascular blood flow among others.
Key Findings
- The study found several haemodynamic effects were significantly enhanced during isoflurane anaesthesia compared to halothane anaesthesia. Cardiac output, blood flow velocity, ejection time, and other factors were all substantially higher under isoflurane.
- Furthermore, the pre-ejection period and diastolic aortic blood pressure were significantly lower under isoflurane compared to halothane.
- Isoflurane was also associated with lower systemic vascular resistance and higher femoral arterial and venous blood flow, compared to halothane.
- However, it was also observed that there were differences in blood flow between the left and right hindlimbs during both types of anaesthesia, indicating differences in regional perfusion possibly caused by factors unrelated to the anaesthetic agents.
Significance of the Study
- The study presents evidence that isoflurane anaesthesia leads to improved left ventricular systolic function compared to halothane anaesthesia, even after administering a potent long-acting alpha2-adrenoreceptor agonist such as romifidine.
- These findings can have implications on the choice of anaesthesia for surgeries on horses, where maintaining optimal haemodynamic conditions is crucial for the well-being of the animal during and after the procedure.
- The study also raises new questions on the differences in regional blood flow during anaesthesia that need to be investigated further for a better understanding of this phenomenon.
Cite This Article
APA
Raisis AL, Young LE, Blissitt KJ, Brearley JC, Meire HB, Taylor PM, Lekeux P.
(2000).
A comparison of the haemodynamic effects of isoflurane and halothane anaesthesia in horses.
Equine Vet J, 32(4), 318-326.
https://doi.org/10.2746/042516400777032282 Publication
Researcher Affiliations
- Centre for Equine Studies, Animal Health Trust, Newmarket, Suffolk, UK.
MeSH Terms
- Anesthetics, Inhalation / pharmacology
- Animals
- Aorta
- Blood Pressure / drug effects
- Cardiac Output / drug effects
- Echocardiography, Transesophageal / veterinary
- Halothane / pharmacology
- Heart Rate / drug effects
- Hemodynamics / drug effects
- Horses / physiology
- Imidazoles / pharmacology
- Isoflurane / pharmacology
- Regional Blood Flow / drug effects
Citations
This article has been cited 5 times.- Garcia Filho SG, de Andrade FSRM, Dos Santos RST, Gonçalves LA, Pereira MAA, de Souza AF, Ambrósio AM, Fantoni DT. Comparison of Hemodynamic Effects of Dobutamine and Ephedrine Infusions in Isoflurane-Anesthetized Horses. Vet Sci 2023 Apr 6;10(4).
- Pequito M, Amory H, de Moffarts B, Busoni V, Serteyn D, Sandersen C. Evaluation of acepromazine-induced hemodynamic alterations and reversal with norepinephrine infusion in standing horses. Can Vet J 2013 Feb;54(2):150-6.
- Williams CL, Meir JU, Ponganis PJ. What triggers the aerobic dive limit? Patterns of muscle oxygen depletion during dives of emperor penguins. J Exp Biol 2011 Jun 1;214(Pt 11):1802-12.
- Ayala I, Rodríguez MJ, Aguirre C, Buendía AJ, Belda E, Laredo FG. Postanesthetic brachial triceps myonecrosis in a Spanish-bred horse. Can Vet J 2009 Feb;50(2):189-93.
- Bergh A, Nyman G, Lundeberg T, Drevemo S. Effect of defocused CO2 laser on equine tissue perfusion. Acta Vet Scand 2006;47(1):33-42.
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