Myocardial Sparing Effect of Fentanyl During Halothane Anaesthesia in Dogs

Abstract

The cardiovascular effects of fentanyl (Sublimaze) were studied in seven mongrel dogs. A constant infusion of the drug was used to produce an apnoeic end-point while concomitant cardiovascular changes were monitored. After one hour the infusion was repeated while ventilation was controlled and atropine was given to eliminate the haemodynamic effect of changes in PaCO2 and heart rate. When PaCO2 was allowed to increase fentanyl reduced heart rate and mean arterial pressure markedly while left ventricular dp/dt was depressed moderately at the time of respiratory arrest. When heart rate and PaCO2 were kept constant there was little variation in the cardiovascular measurements during fentanyl infusion. We conclude that fentanyl allows relative myocardial sparing in dogs when used at clinically effective concentrations.

Total Intravenous Anesthesia in Greyhounds: Pharmacokinetics of Propofol and Fentanyl—MA Preliminary Study

“…In this study 40 μg/kg atropine IV failed to inhibit the decrease in heart rate completely. This is not unexpected as Eisele et al reported that the effects of atropine (1 mg/kg IV) lasted only 30 minutes in dogs anesthetized with fentanyl infusion, halothane and nitrous oxide 13 . The combination of propofol and fentanyl may predispose to bradycardia because propofol alone may induce bradycardia.…”

“…Fentanyl, like alfentanil, is a potent opioid analgesic, which has previously been given to dogs by infusion 12–14 . A fentanyl infusion (0.5 μg/kg/min) has been used to supplement nitrous oxide and halothane anesthesia in large breed dogs undergoing surgical therapy of end‐stage, dilated cardiomyopathy 12 .…”

“…This technique provided safe anesthesia, conserved cardiac function and had extremely good analgesic properties. Further studies in mixed breed dogs anesthetized with halothane and nitrous oxide concluded that fentanyl infusion (0.4 to 0.8 μg/kg/min) causes a significant decrease in mean arterial pressure and heart rate, but not of left ventricular function 13 . In a study designed to examine whether an opioid anesthetic technique induced less cardiovascular depression than standard inhalational anesthesia, Ilkiw and colleagues used a fentanyl infusion (15.9 μg/kg/min for 20 minutes followed by 1.065 μg/kg/min) in combination with enflurane, in healthy mixed breed dogs 14 .…”

Sedation of the Critically Ill Patient

“…Diazepam and midazolam have similar effects and are given at similar dosages (0.1 to 0.5 mg/kg IV or IM), although midazolam is preferred for intramuscular use since it is water soluble and readily absorbed. 5,6 Vagally mediated bradycardia or second-degree atrioventricular block is often seen after opioid administration and can be treated with anticholinergics (atropine, glycopyrrolate) as indicated. In blood pressure, is well maintained.…”

The use of intraoperative fentanyl in spontaneously breathing dogs undergoing orthopaedic surgery

“…On average atropine was administered 78 mins before fentanyl, by which time its effects may have waned, although Kantelip, Alatienne, Gueorguiev and Duchenne-Marullaz (1985) reported that the effects of 25 pg/kg bwt atropine on vagal activity lasted at least 120 mins in conscious dogs. We consider it likely that atropine administered iv immediately before fentanyl injection would have attenuated the bradycardia, although according to Eisele, Reitan, Torten and Miller (1975), injecting 1 mg/kg bwt iv immediately prior to the onset of a fentanyl infusion in dogs did not completely abolish the associated bradycardia.…”