EFFECTS OF FENTANYL, AND THE ANTAGONISM BY NALOXONE, ON REGIONAL BLOOD-FLOW AND BIOCHEMICAL VARIABLES IN CONSCIOUS RABBITS

  • 1 January 1982
    • journal article
    • research article
    • Vol. 260  (1) , 115-129
Abstract
Effects of fentanyl [general anesthetic](cumulative doses: 25, 75 and 125 .mu.g .cntdot. kg-, i.v.) on respiratory, systemic and regional hemodynamic and biochemical variables were studied in the conscious rabbit. The initial dose of fentanyl (25 .mu.g .cntdot. kg-1) produced a rise in blood pressure and a decrease in heart rate but, on subsequent doses, smaller effects were observed. The drug produced changes in arterial blood gases which were due to a severe decrease in respiratory frequency and an increase in muscular rigidity of chest and neck muscles. The blood flow to skin, stomach, mesentery plus pancreas, bones and fat was decreased by fentanyl. These changes resemble those obtained during .alpha.-adrenergic stimulation and may be related to a release of catecholamines during respiratory depression. Hepatic arterial blood flow was increased and this effect may be responsible for the rapid metabolism and a short duration of action of fentanyl. Fentanyl caused an increase in the concentration of glucose, lactate and Pi in the arterial blood. These changes are probaby due to hypoxia. Administraton of naloxone not only reversed the residual effects of previous fentanyl administration but also antagonized the respiratory, hemodynamic and biochemical responses to the morphinomimetic drug.

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