Abstract
The clinical and cardiorespiratory effects of premedication with acepromazine, butorphanol or diazepam in addition to romifidine before induction of anaesthesia with ketamine were studied in 6 horses on 4 random occasions. Administration of romifidine alone or in combination with butorphanol resulted in an increase in arterial blood pressure, accompanied by a significant decrease in heart rate with second-degree atrio-ventricular heart block. Induction of anaesthesia with ketamine returned the heart rate to baseline value, but the arterial blood pressure was significantly increased compared to baseline. Including acepromazine in the premedication prevented the hypertension and bradycardia induced by romifidine. The respiratory rate was slightly decreased after premedication in all groups, but returned to the baseline value after induction of anaesthesia. Mild hypercapnia and significant hypoxaemia were observed during sedation and anaesthesia, reflecting an impairment of pulmonary function. Premedication with acepromazine before sedation with romifidine resulted in a fast induction and good anaesthesia. Inclusion of butorphanol in the premedication resulted in individual variation in the quality of induction and anaesthesia. Addition of diazepam to the sedation with romifidine resulted in good muscle relaxation with a smooth induction and maintenance of anaesthesia and an increased time before the horses responded to noxious stimuli, compared with romifidine and ketamine anaesthesia. All horses reached a standing position at the first attempt, but horses premedicated with diazepam in combination with romifidine showed mild ataxia after recovery.
Keywords: acepromazine, butorphanol, diazepam
Sammanfattning
Kliniska och kardiorespiratoriska effekter av sedering med romifidin enbart eller i kombination med kompletterande premedicinering med acepromazin, butorphanol eller diazepam inför induktion av dissociativ anestesi med ketamin studerades hos 6 hästar vid fyra olika tillfallen. Vid samtliga tillfällen sederades hästarna med romifidin 0.1 mg/kg intravenöst (iv) och när kompletterande premedicinering gavs utgjordes denna av acepromazin 0.025 mg/kg (im) 23 min före romifidin, butorphanol 0.025 mg/kg (iv) 2 min efter romifidin eller diazepam 0.05 mg/kg (iv) 7 min efter romifidin omedelbart före ketamin. Sederingskombinationerna gavs i slumpmässig ordning och hästarna placerades i sidoläge under anestesin. Administrering av romifidin enbart eller i kombination med butorphanol resulterade i en stegring av det arteriella blodtrycket, åtföljt av bradykardi med förekomst av andra gradens atrioventrikulära hjärtblock. Efter induktion av dissociativ anestesi med ketamin 2.2 mg/kg (iv) steg hjärtfrekvensen till referensvärdets nivå, men det arteriella blodtrycket ökade signifikantjämfört med referensvärdet som registrerats på stående, osederad häst. När acepromazin inkluderades i premedicineringen registrerades varken hypertension eller bradykardi efter sedering. Minskad andningsfrekvens registrerades efter samtliga premedicineringar men andningsfrekvensen ökade till referensvärdets nivå efter induktion av anestesin. Mild hypercapni och signifikant hypoxemi observerades under både sedering och anestesi vilket speglar den försämrade lungfunktionen. Anestesin bedömdes som bra med kombinationen av romifidin och ketamin. Kompletterande premedicinering med acepromazin resulterade i en snabb induktion och bra anestesi. Kompletterande premedicineringen med butorphanol resulterade i den största individuella variationen beträffande induktionens och anestesins duration och kvalitet. Kompletterande premedicinering med diazepam resulterade i god muskelrelaxering och en smidig induktion och underhåll av anestesin. Reaktionen på kanylstick i form viljemässiga awärjningsrörelser återkom senare när diazepam var inkluderad i premedicineringen jämfört med sedering enbart med romifidin. Alla hästar inkluderade i studien reste sig på första försöket oavsett premedicinering, men hästarna visade lindrig ataxi efter resningen när diazepam varit inkluderad i premedicineringen.
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Acknowledgment
The authors gratefully acknowledge the expert technical assistance of Ann-Marie Löfgren, Pia Funk- quist and Karin Morgan. This work was supported by BI-vet, Malmö, Sweden.
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