Abstract:Object: To evaluate the effect, safety and availability of Intravenous PCA (ivPCA) and Subcutaneous PCA (scPCA) with morphine. Method: Sixty three patients undergoing cardiac surgery (ASA I to III) were assigned randomly into two groups: Group scPCA (n=31) and group ivPCA (n=32).The mixture of morphine 1mg/ml and lidocaine 10mg/ml was administered in both groups. PCA setting: Loading dose of 2ml, bolus dose of 1ml, hour limit of 10ml/h,and lock out time of 3min were set. The following indexes were recorded respectively at 24,48 and 72 hours after the PCA pumps were used:the VAS scores of pain; sedation score; demanded delivery and effective delivery; MAP, HR, RR, SPO 2, and side effects. Results: There was significant difference between Group ivPCA and Group scPCA in onset of analgesia ( P <0.05). No significant difference was found between the two groups in the VAS scores of the pain and side effects. Equipment accidents in Group scPCA were significantly less than that in Group ivPCA (5 equipment accidents in Group ivPCA were found)( P <0.05).Conclusion: No significant difference was found between the two groups in theraputic and side effects. Morphine scPCA excels morphine ivPCA in its simple operation, low accident rate, and longer possible application time.