“…a combination of morphine and fentanyl could potentially shorten the onset of analgesia and enhance the analgesic effect. 1,8,9 In general, because opioids are considered to not induce significant sympathetic blockade following epidural adminsitration, 6,7 one would expect epidural administration of a combination of morphine and fentanyl to have few clinically important cardiovascular effects. However, decreases in mean arterial blood pressure and heart rate (HR) and an increase in PaCO 2 have been observed following epidural administration of fentanyl in cats anesthetized with isoflurane.…”