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Comparison of Neurologic Responses to the Use of Medetomidine as a Sole Agent or Preanesthetic in Laboratory Beagles

Jämförelse av neurologiska responser vid användning av medetomidin för sedering och preanestesering av försöks beaglar

Acta Veterinaria Scandinavica volume 33, pages 77–88 (1992)Cite this article

Abstract

Different dose regimens of medetomidine (a potent α2-adrenergic agonist), adding up to a combined dose of 80 µg/kg, were administered to laboratory beagles to determine physiologic responses including neurologic. The study was intended to determine EEG responses where sufficient sedative and analgesic effects are reached with medetomidine and in contrast its effects when used with ketamine or halothane.

Cardiopulmonary responses were very similar in each dose regimen, showing the characteristic properties of single doses of 80 µg/kg of medetomidine. Effective sedative and analgesic duration seemed to be a function of when the largest dose was administered. Adequate additional sedative and analgesic could be gained from injections at doses of half of the initial one.

The potent sedative and analgesic effects of medetomidine confirmed by neurologic evaluation supports its potential use as a premedication to general anesthesia in dogs. In this study, 2 different doses of medetomidine were also tested as premedication to both ketamine HCl and halothane anesthesia. Neorologic responses were determined at the same time cardiopulmonary parameters, anesthetic quality, and dose requirements were recorded.

Medetomidine was found to have favorable qualities in conjunction with these anesthetics. Cardiopulmonary parameters remained satisfactory in both groups as preanesthetic medication prior to halothane, but no additional benefits could be seen from doses of 40 µg/kg medetomidine compared to 20 µg/kg, except a significant 30% reduction in halothane requirement.

The positive chronotropic and inotropic properties of ketamine restored the medeto-midine-induced bradycardia and produced a short anesthetic period of 15 to 30 min depending on the dose of medetomidine. The quality of anesthesia was better when 40 µg/kg medetomidine was used, but recorvery was quicker with 20 µg/kg medetomidine.

Medetomidine significantly reduced cerebral activity as demonstrated by recordings of total amplitude and frequency evaluation of the EEG with compressed spectral analysis. This analytical method was effective in confirming clinical signs of sedation, analgesia, and anesthesia in canine subjects.

Sammandrag

Medetomidin (en effektiv α2- adrenergisk agonist) doserades enligt olika program, alla med en sammanlagd kombinerad dos av 80 µg/kg, åt försöks beaglar för att fastslå fysilogisk, inkluderande neurologisk, respons. Syftet med experimentei var att fastslå EEG-respons då tillräcklig sedativ och analgetisk effekt nås med medetomidin allena samt dess effekt i samband med ketamin eller halotan.

Verkningarna på cirkulations- och andningsorganen var liknande i alla 3 Programmen, uppvisande samma karakteristiska egenskaper, som kunde förväntas vid en enda dos på 80 µg/kg medetomidin. Längden på den effektiva sedativa och analgetiska verkningen tycktes vara i förhållande till när den största dosen gavs. Tillräcklig ytterligare sedativ och analgetisk effekt kunde uppnås med doser nähten mindre än den ursprungliga.

Den starka sedativa och analgetiska effekten av medetomidin, bekräftad via den neurologiska värderingen, ger indikation för dess använding hos hundar som premedisinering före allmän anestesi. I detta arbete uppskattades även effekten av 2 olika doser av medetomidin som premedisinering till både ketamin HCL och halotan anestesi. Den neurologiska värderingen gjordes samtidigt som cirkulations- och respirationsparametrar, anestetisk kvalitet och doseringsbehov antecknades.

Det konstaterades att medetomidin har fördelaktiga egenskaper i kombination med dessa anestetikum. Cirkulations- och respirationsparametrarna förblev på tillfredsställande nivå i bägge grupper av premedisinering före halotan anestesi, men ytterligare fördelar av en förhöjd dos om 40 µg/kg framom en dos på 20µg/kg kunde ej uptäckas, förutom en signifikant 30% nedgång i mängden förbrukat halotan.

Ketaminets positiva kronotropiska och inotropiska egenskaper normaliserade den medetomidinförorsakade bradykardin och framkallade en kort 15 till 30 min period av anestesi, beroende på dosen medetomidine. Den anestetiska kvaliteten var bättre med 40 µg/kg medetomidine, men uppvakningsperioden var kortare med 20 µg/kg.

Registrering av EEG - totalamplituder och frekvenser med komprimerad spektral analys visade en signifikant medetomidinorsakad nedgång i hjärnaktiviteten. Denna analysmetod visade sig effektivt bekräfta kliniska tecken på sedering, analgesi och anestesi hos hundar.

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Authors and Affiliations

  1. New York State College of Veterinary Medicine, Cornell University, 14853, Ithaca, New York, USA

    Charles E. Short, Jan E. Räihä, Maija P. Räihä & Klaus Otto

  2. Department of Clinical Sciences, and Veterinary Clinic Mevet, College of Veterinary Medicine, Helsinki, Finland

    Charles E. Short, Jan E. Räihä, Maija P. Räihä & Klaus Otto

  3. Chirurgische Tierklinik der Universität München, Germany

    Charles E. Short, Jan E. Räihä, Maija P. Räihä & Klaus Otto

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Short, C.E., Räihä, J.E., Räihä, M.P. et al. Comparison of Neurologic Responses to the Use of Medetomidine as a Sole Agent or Preanesthetic in Laboratory Beagles. Acta Vet Scand 33, 77–88 (1992). https://doi.org/10.1186/BF03546938

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Acta Veterinaria Scandinavica

ISSN: 1751-0147