Intravenous injection of fentanyl in adult awake goats increases arterial blood pressure and reduces heart rate without affecting metabolic rate or temperature

At high doses, synthetic opioids are thought to slow heart rate and reduce mean arterial blood pressures in humans and rodents and could create a life-threatening situation. Herein, we report dose-dependent effects of intravenous (IV) injection of fentanyl on systolic (SYS), diastolic (DIA), and mean (MAP) arterial blood pressure, heart rate (HR) metabolic rate and body temperatures in adult female goats (n=7). Variables were measured 30 min before, during and up to 90 min after IV injection of vehicle (saline) or 25, 50, 75, 100, and 125 mcg/kg fentanyl. Baseline averages for SYS, DIA, MAP was 102, 73, 83 mmHg, respectively, and HR was 84 beats/minute (bpm). There were no significant changes in these values over 90 minutes when saline was injected. Between 8 and 10 minutes after fentanyl injection, SYS, DIA, and MAP increased substantially from control by about 40, 25, and 30 mmHg, respectively. These increases did not appear dose independent, but by 90 minutes post-injection SYS, DIA, and MAP decreased toward control at the lowest dose (25 mcg/kg). The fentanyl induced arterial hypertension was partially compensated by a ~15 bpm decrease in heart rate which changed minimally between 10 and 90 minutes after fentanyl injection. The sustained increase in arterial blood pressure indicates a sustained excitatory effect of fentanyl consistent with the excitatory effect of fentanyl on tidal volume and respiratory muscle activity (see additional abstracts from our group). This excitatory effect is not due to changes in metabolic rate and/or body temperature as we found no consistent effect of fentanyl injections on these variables. This excitatory effect of fentanyl appears species-dependent as opioid agonists injected into rats and humans typically induces arterial hypotension. Species dependency of fentanyl may reflect species variation in effects of fentanyl on vagal nerve endings, brainstem control centers, and/or cardiac receptors (J. Car.Pharm, 1985), or alternatively may reflect differences in fentanyl metabolism whereby metabolites may have differential effects on blood pressure among these species. NIH DA050571 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.