title: The dose-dependent effects of fentanyl on rat skeletal muscle microcirculation in vivo.
abstract: Determining the effects of analgesia on the microcirculation is difficult because the surgery needed to allow in vivo observation often requires anesthesia. In this study, we used the dorsal microcirculatory chamber (DMC) to determine the effects of large (LF) and small (SF) dose IV fentanyl on the microcirculation compared with a conscious control. Male Wistar rats (130 g, n = 5) were implanted with the DMC to enclose a single layer of striated muscle. Animals were allowed 3 wk to recover from surgery and then, over the following 2 wk (1 infusion/wk) using intravital microscopy, the microcirculation was viewed in conscious animals (t = 0-30 min), followed by an induction bolus dose (t = 40-45 min), then a "step-up" maintenance infusion of one of the following, LF (40-90 microg x kg(-1) x h(-1)), SF (10-60 microg x kg(-1) x h(-1)), or saline (5-10 microg x kg(-1) x h(-1)) (t = 45-105 min). Small arterioles (<30 micro m) dilated (23.6% +/- 7.1%) after induction with LF, but constricted (-21.3% +/- 7.1%) with SF (P < 0.05). During maintenance, constriction increased with increasing dose of LF (-21.9% +/- 4.0%) and SF (-16.7% +/- 9.1%) (t = 105 min, P < 0.05). Similar patterns were observed in all arterioles (10-120 microm) and venules (15-250 microm). We conclude that the DMC provides an excellent technique for observing microcirculatory responses to fentanyl, and in rat skeletal muscle in vivo, an i.v. infusion of fentanyl produces significant constriction of arterioles.
authors.affiliation: Section of Surgical and Anesthetic Sciences, Division of Clinical Sciences, University of Sheffield, Royal Hallamshire Hospital, Sheffield, United Kingdom.
authors.forename: Zoë L S
authors.initials: ZL
authors.lastname: Brookes
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Brown
authors.forename: Charles S
authors.initials: CS
authors.lastname: Reilly
mesh_terms: D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D001160:Arterioles / Q000033:anatomy & histology / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005283:Fentanyl / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D008833:Microcirculation / Q000187:drug effects; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000187:drug effects; D010147:Pain Measurement / Q000187:drug effects; D010805:Physical Conditioning, Animal / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D012039:Regional Blood Flow / Q000187:drug effects; D012149:Restraint, Physical; D014699:Venules / Q000033:anatomy & histology / Q000187:drug effects
chemical_list: D000701:Analgesics, Opioid; D005283:Fentanyl