Effect of transdermally administered fentanyl on the minimum alveolar concentration of isoflurane in cats

Abstract

Objective To determine the e¡ect of two doses of fentanyl, administered transdermally, on the minimum alveolar concentration (MAC) of iso£urane in cats.Study design Prospective, randomized study.Animals Five healthy, spayed, female cats.Methods Each cat was studied thrice with at least 2 weeks between each study. In study 1, the baseline iso£urane MAC was determined in triplicate for each cat. In studies 2 and 3, iso£urane MAC was determined 24 hours after placement of either a 25-or 50-mg hour À1 fentanyl patch. In each MAC study, cats were instrumented to allow collection of arterial blood and measurement of arterial blood pressure. Twenty-four hours prior to studies 2 and 3, a catheter was placed and secured in the jugular vein and either a 25 or 50-mg hour À1 fentanyl patch was placed in random order on the left thorax. Blood samples for plasma fentanyl determination were collected prior to patch placement and at regular intervals up to 144 hours. After determination of MAC in studies 2 and 3, naloxone was administered as a bolus dose (0.1 mg kg À1) followed by an infusion (1 mg kg) and MAC redetermined.Results The baseline iso£urane MAC was 1.51 AE 0.21% (mean AE SD). Fentanyl (25 and 50 mg hour À1 ) administered transdermally signi¢cantly reduced MAC to 1.25 AE 0.26 and 1.22 AE 0.16%, respectively. These MAC reductions were not signi¢cantly di¡er-ent from each other. Iso£urane MAC determined during administration of fentanyl 25 mg hour À1 and naloxone (1.44 AE 0.16%) and fentanyl 50 mg hour À1and naloxone (1.51 AE0.19%) was not signi¢cantly di¡erent from baseline MAC (1.51 AE0.21%).Conclusions and clinical relevance Fentanyl patches are placed to provide long-lasting analgesia. In order to be e¡ective postoperatively, fentanyl patches must be placed prior to surgery. Plasma fentanyl concentrations achieved intraoperatively decrease the need for potent inhalant anesthetics in cats.

Determination of the sevoflurane sparing effect of methadone in cats

“…This e ′SEVO range was selected as a starting place based on results of prior studies evaluating the MAC reducing effect of opioids in cats (Ilkiw et al. 1997, 2002; Yackey et al. 2004; Ko et al.…”

“…In cats, remifentanil, alfentanil, fentanyl, morphine, buprenorphine, and butorphanol decrease the MAC of isoflurane (Ilkiw et al. 1997, 2002; Yackey et al. 2004; Ferreira et al.…”

Pharmacokinetics of fentanyl, alfentanil, and sufentanil in isoflurane‐anesthetized cats

“…Fentanyl and its derivatives, alfentanil and sufentanil, have been used as anesthetic adjuncts in cats (Ilkiw et al ., ; Mendes & Selmi, ; Yackey et al ., ). While the pharmacokinetics of fentanyl (Lee et al ., ) and alfentanil (Pascoe et al ., ) have been reported in cats, to the authors' knowledge, the pharmacokinetics of sufentanil has not been characterized in that species, and the pharmacokinetics of fentanyl, alfentanil, and/or sufentanil have not been compared in a single study in cats.…”

Effect of orally administered tramadol alone or with an intravenously administered opioid on minimum alveolar concentration of sevoflurane in cats

“…Intravenous administration of morphine (1.0 mg/kg [0.45 mg/lb]) or butorphanol (0.08 mg/kg [0.036 mg/lb] or 0.8 mg/kg [0.36 mg/lb]) 11 or transdermal administration of fentanyl (20 and 50 µg/h) 12 Effect of orally administered tramadol alone or with an intravenously administered opioid on minimum alveolar concentration of sevoflurane in cats Abbreviations DBP Diastolic blood pressure HR Heart rate MAC Minimum alveolar concentration MAP Mean arterial blood pressure Petco 2 End-tidal partial pressure of carbon dioxide RR Respiratory rate SBP Systolic blood pressure Spo 2 Oxygen saturation as measured by pulse oximetry significantly decreases the volume percentage of isoflurane required to anesthetize cats. Reduction of MACs of inhalant anesthetics appears to be affected by the dose, route, and class of opioid administered.…”