Equine general anaesthesia and its relatively high mortality rate : An investigation of some pharmacological options to reduce the cardiovascular side effects of routinely used sedative and anaesthetic agents.

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http://urn.fi/URN:ISBN:978-951-51-4545-1
Julkaisun nimi: Equine general anaesthesia and its relatively high mortality rate : An investigation of some pharmacological options to reduce the cardiovascular side effects of routinely used sedative and anaesthetic agents.
Tekijä: de Vries, Annemarie
Muu tekijä: Helsingin yliopisto, eläinlääketieteellinen tiedekunta
Kliinisen eläinlääketieteen tohtoriohjelma
Opinnäytteen taso: Väitöskirja (artikkeli)
Tiivistelmä: This thesis includes studies investigating several options to minimize the undesirable cardiovascular side effects commonly seen with some of the routinely used sedative and anaesthetic agents in horses, under both clinical and research conditions. In the first study, the effect of dobutamine on arterial blood pressure and cardiac output was investigated in horses anaesthetised with isoflurane for routine clinical procedures. In these horses, dobutamine was infused when mean arterial blood pressure was below 70 mmHg. An improvement in arterial blood pressure and cardiac output, measured by the lithium dilution technique, was observed after the start of dobutamine infusion, although an increase in sympathetic tone induced by surgical stimulus likely also contributed. In two studies involving ponies anaesthetised for minor surgical procedures, total intravenous anaesthetic techniques were evaluated. In one, the combined infusion of propofol with ketamine was examined; in the other, involving colts undergoing castration, a continuous intravenous infusion of alfaxalone was compared to intermittent intravenous injections of the same agent. In both studies, good quality of anaesthesia and surgical conditions were achieved with no apparent cardiovascular depression. Two studies investigated the influence of vatinoxan on alpha-2 adrenoceptor-induced cardiovascular side effects. The effects of the intravenous co-administration of vatinoxan with romifidine on the cardiopulmonary system were investigated in one study. The peripheral antagonist successfully attenuated the effects of romifidine on the cardiovascular system, without affecting the level of sedation. In a further research study, vatinoxan was combined with detomidine for pre-anaesthetic medication in horses anaesthetised with isoflurane for arthroscopy, and resulted in improved cardiac function and oxygen delivery compared to the same horses anaesthetised with an identical protocol but without vatinoxan. However, arterial blood pressure was unacceptably low during the initial anaesthetic phase in horses receiving vatinoxan. The optimal dose ratio of vatinoxan and the respective alpha-2 adrenoceptor agonists romifidine and detomidine, needs to be further investigated, especially when these drugs are part of volatile agent-based anaesthetic protocols, in order to optimize peripheral perfusion without unacceptable decreases in arterial blood pressure.Miss de Vries’ PhD research investigated several options to minimize the undesirable cardiovascular side effects commonly seen with some of the routinely used sedative and anaesthetic agents in horses. Inhalational agents, such as isoflurane, are often used for maintenance of general anaesthesia in horses, but are known for their marked cardiovascular depressant effects. The positive inotropic (i.e. increasing myocardial contraction force) agent dobutamine is commonly used to treat hypotension in horses during isoflurane-maintained anaesthesia. Yet, limited information is available on the actual effect dobutamine has on cardiac output (i.e. the amount of blood pumped by the heart per minute) under these circumstances. In the first study, Miss de Vries investigated the effect of dobutamine on arterial blood pressure and cardiac output in horses anaesthetised with isoflurane for routine clinical procedures. In these horses, dobutamine was infused when mean arterial blood pressure was below 70 mmHg. An improvement in arterial blood pressure and cardiac output, measured by the lithium dilution technique, was observed after the start of dobutamine infusion, although an increase in sympathetic tone induced by surgical stimulus likely also contributed. Anaesthetic protocols based on total intravenous techniques cause a minimal stress response in the horse, and are often characterized by an absence of cardiovascular depression, making these techniques suitable alternatives to volatile agent-based (i.e. isoflurane-based) anaesthesia in horses. Miss de Vries evaluated two total intravenous anaesthetic techniques in two studies involving ponies anaesthetised for minor surgical procedures. In one, the combined infusion of propofol with ketamine was examined; in the other, a continuous intravenous infusion of alfaxalone was compared to intermittent intravenous injections of the same agent. In both studies, good quality of anaesthesia and surgical conditions were achieved with no apparent cardiovascular depression. Alpha-2 adrenoceptor agonists such as detomidine and romifidine are commonly used in equine clinical anaesthesia practice for their profound sedative and analgesia effects, which result from an action within the central nervous system (brain and spinal cord). Unfortunately, these agents also result in profound peripherally-induced (i.e. outside the central nervous system) cardiovascular side effects. Vatinoxan (also formerly known as MK-467) is a peripherally acting α2-adrenoceptor antagonist which, when combined with an alpha-2 adrenoceptor agonist, may prevent the unwanted side effects of the agonist without affecting its centrally-induced effects of sedation and analgesia. Miss de Vries investigated the influence of vatinoxan on detomidine- and romifidine-induced cardiovascular side effects in two studies. In one study, the effect of the intravenous co-administration of vatinoxan with romifidine on the cardiopulmonary system was investigated. The peripheral antagonist successfully attenuated the effects of romifidine on the cardiovascular system, without affecting the level of sedation. In a further research study, vatinoxan was combined with detomidine for pre-anaesthetic medication in horses anaesthetised with isoflurane for arthroscopy, and resulted in improved cardiac function and oxygen delivery compared to the same horses anaesthetised with an identical protocol but without vatinoxan. However, arterial blood pressure was unacceptably low during the initial anaesthetic phase in horses receiving vatinoxan.
URI: URN:ISBN:978-951-51-4545-1
http://hdl.handle.net/10138/247814
Päiväys: 2018-11-02
Avainsanat:
Tekijänoikeustiedot: Julkaisu on tekijänoikeussäännösten alainen. Teosta voi lukea ja tulostaa henkilökohtaista käyttöä varten. Käyttö kaupallisiin tarkoituksiin on kielletty.


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