Objective: To evaluate the effect of test dose fentanyl on predictingpostoperative analgesia and respiratory depression. Methods: Preoperatively the lowest pulseoximeter saturation (SpO_2) under room air breathing was measured after 2 μg/kg of fentanyl givenintravenously in 35 patients who were scheduled with continuous intravenous morphine analgesia (12μg·kg^(-1)·h^(-1)) postoperatively. Results: The test dose fentanyl resulted in respiratorydepression in 19 of 35 cases, while 8 (42.1%) of the 19 cases developed respiratory depressionpostoperatively. However in the rest 16 patients, no patient (0) developed respiratory depression (P< 0.01). The fentanyl-induced lowest SpO_2 significantly correlated with the lowest SpO_2postoperatively (P < 0.01). The analgesia effect in terms of verbal analogue scale was correlatedneither with the fentanyl-induced lowest SpO_2 nor with the lowest SpO_2 postoperatively (P > 0.05).Conclusion: The patient who was sensitive to fentanyl-induced respiratory depression would take ahigh risk to develop postoperative respiratory depression with intravenous morphine analgesia andthe patient with respiratory depression does not always go with satisfactory analgesia.
