Haemodynamic changes during sedation in ponies

Abstract

The cardiovascular changes induced by several sedatives were investigated in five ponies with a subcutaneously transposed carotid artery by means of cardiac output determinations (thermodilution technique), systemic and pulmonary artery pressure measurements (direct intravascular method) and arterial blood analysis (blood gases and packed cell volume). The cardiovascular depression (decrease in systemic blood pressure and cardiac output) was long lasting (greater than 90 min) after administration of propionylpromazine (0.08 mg/kg intravenous (i.v.)) together with promethazine (0.08 mg/kg i.v.). The phenothiazine-induced sedation was not optimal. alpha 2-Agonists (xylazine (0.60 mg/kg i.v.) and detomidine (20 micrograms/kg i.v.)) induced initial but transient cardiovascular effects with an increase in systemic blood pressure and a decrease in cardiac output for about 15 min. Second degree atrioventricular blocks and bradycardia were seen during this period. The cardiovascular depression was more pronounced during detomidine sedation. Atropine (0.01 mg/kg i.v.) induced a tachycardia with a decrease in stroke volume but did not alter the cardiac output or other cardiovascular parameters. It prevented the occurrence of the bradycardia and heart blocks normally induced by xylazine or detomidine. Atropine potentiated the initial hypertension induced by the alpha 2-agonistic sedatives (especially detomidine). The decrease in cardiac output induced by xylazine, and to a lesser extent by detomidine, was partially counteracted when atropine was given in advance. The atropine-xylazine combination seemed the best premedication protocol before general anaesthesia as it only resulted in minor and transient cardiovascular changes.

Comparative study between atropine and hyoscine-N-butylbromide for reversal of detomidine induced bradycardia in horses

“…Detomidine was used in the present study as an experimental model to induce vagally mediated bradycardia and to allow the comparison of the positive chronotropic actions of hyoscine and atropine. Alpha‐2 agonist drugs induce vagally mediated bradycardia that may be followed by up to 55% decreases in CI values (Gasthuys et al . 1990a; Wagner et al .…”

Stereoselective pharmacokinetics of ketamine and norketamine after constant rate infusion of a subanesthetic dose of racemic ketamine or S-ketamine in Shetland ponies

“…11 Ponies were judged to be healthy on the basis of results of physical examination, a CBC, and serum biochemical analysis. The ponies were conventionally housed as a group at the horse clinic of the Vetsuisse Faculty in Bern and were not included in any other experiment for at least 8 months preceding this study.…”

Non-invasive blood pressure measurement in ferrets ( Mustela putorius furo ) using high definition oscillometry

“…Fixation or sedation is therefore required, although these techniques influence BP (Gasthuys et al, 1990;Farah et al, 2004). In ferrets, 'scruffing' (a method of restraint whereby the loose skin around the neck of the ferret is grasped and held firmly) results in a certain state of relaxation (Ball, 2006), but the applicability of this technique for BP measurement is unknown.…”