[Effects of different doses of fentanyl on the stress response in patients undergoing valve replacement]

To investigate the effects of different doses of fentanyl on the stress response in valve replacement surgery during cardiopulmonary bypass (CPB).

Thirty ASA II-III adult patients scheduled for cardial valve replacement were randomly divided into 3 groups: Group A (fentanyl 30 microg/kg), Group B (fentanyl 60 microg/kg), and Group C (fentanyl 100 microg/kg). Anesthesia was induced with medazalam 0.1 mg/kg, fentanyl 10 microg/kg and vecuronium 0.1 mg/kg; And were maintained with fentanyl and propofol infusion. Remained dose of fentanyl was used before the CPB. MAP, CVP, HR, P(ET)CO2, SpO2, nasal and rectal temperature were monitored continuously. Blood samples were taken before the operation (T1), before the CPB (T2), 30 min after the aortic declamping (T3), 2 h after the aortic declamping (T4), 24 h (T5) after the operation to determine the plasma levels of glucose, adrenocorticotropic hormone (ACTH), angiotensin II (AT II) and cortisol.

Levels of glucose, ACTH, AT II and cortisol after the CPB (T3, T4 and T5) in 3 groups were significantly increased compared with that of T1 (P < 0.05 or P < 0.01). After CPB, at the same time point, among the 3 groups, the levels of the above index of Group A were the most highest, that of Group C were the most lowest. Glucose, ACTH, AT II and cortisol levels at T3 and T4 were significantly lower in Group B and C than those in Group A ( P < 0.05); But there was no significant difference between Group B and C. The duration of stay in the ICU and time of endotracheal extubation were significantly longer in patients of Group C than Group A and B (P < 0.05).

Fentanyl (30-100 microg/kg) can completely suppress the stress response induced by intubation and intense surgical stimulus before CPB. Different doses of fentanyl seemed to be effective in reducing CPB-induced stress response. But the effect was not dependent on dose. So 60 microg/kg fentanyl seemed to be an ideal dose.