The aim of this study was to evaluate the effects of respiratory depression of IV-PCA using morphine which has potent respiratory depression or nalbuphine which has less potent respiratory depression among opioids.

Forty patients were divided into two groups; Group M was used morphine, and Group N was used nalbuphine as a drug for IV-PCA. When patient emerges from general anesthesia, Group M was given initial bolus of 0.1 ml/kg of 0.1% morphine solution and connected Basal Bolus PCA infusor R containing morphine 50 mg per 40 ml in normal saline. Group N, similarly Group M, was given initial bolus of 0.1 ml/kg of 0.1% nalbuphine solution, and connected PCA infusor containing nalbuphine 50 mg per 40 ml in normal saline. To compare respiratory depression, arterial blood gas analyses were done preoperatively and at 1, 6 and 12 hour after IV-PCA. Simultaneously, analgesic and side effects were evaluated.

There were no remarkable respiratory depression such as hypercarbia(PaCO2 > 50 mmHg), hypoxemia(PaO2 < 60 mmHg) and slow respiratory rate in both groups. Analgesic and side effects were similar in both groups.

We conclude that IV-PCA using morphine or nalbuphine is relatively effective and safe method for the postoperative pain control. Ordinarily, IV-PCA dose not induce respiratory depression unless overdose in careless or mistaken mishaps are developed.