Effects of fentanyl on cardiovascular and plasma catecholamine responses in surgical patients.
OBJECTIVE
Whether opioids administered before skin incision, under inhalational anesthesia, improve cardiovascular and plasma catecholamine responses to surgical stimulation compared with those administered after skin incision remains unclear. We compared the effects of fentanyl injected before and after skin incision on these responses.


METHODS
We studied 50 healthy female patients [American Society of Anesthesiologist (ASA) physical status 1] who underwent elective total abdominal hysterectomy through an infraumbilical incision (midline incision) under nitrous oxide (60%)-oxygen-isoflurane (1.2%) anesthesia. Fentanyl (2.0 or 4.0 microg.kg(-1)) was administered i.v. 5 min before (pretreatment group) or 5 min after (posttreatment group) skin incision. Control patients received a saline injection. Heart rate (HR) and mean arterial blood pressure (MAP) were recorded 1 min before incision and serially for 30 min afterward. Plasma levels of norepinephrine (Nor) and epinephrine (Epi) were determined 1 min before incision and serially up to 20 min after skin incision.


RESULTS
The MAP response to incision had decreased after 10 min in posttreatment fentanyl (2 microg.kg(-1)) (P < 0.05) and after 8, 10, 15, and 20 min in posttreatment fentanyl (4 microg.kg(-1)) ( P < 0.05). At the same doses, fentanyl administered before skin incision attenuated MAP response to incision after 1 min with the smaller dose (P < 0.05) and after 1, 3, 5, 6, 8, 10, 15, and 20 min with the higher dose (P < 0.05). Fentanyl suppressed Epi response to surgery 8 and 20 min after skin incision (P < 0.05) at both doses, except for 8 min after incision in pretreatment fentanyl (2 microg.kg(-1)). Overall, the hemodynamic and sympathoadrenergic responses after skin incision were attenuated, with the exception of plasma Nor after fentanyl irrespective of time and dose.


CONCLUSIONS
Our results indicated that fentanyl depressed cardiovascular and plasma catecholamine responses irrespective of the time of administration, and that the higher dose of fentanyl produced a greater suppression of MAP and HR responses. In addition, the depressant effects on MAP of high-dose fentanyl administered 5 min before skin incision lasted longer than when injected 5 min after incision. At both doses, the opioid attenuated the rise in plasma Epi, but not Nor.