Comparison of tramadol and morphine via subcutaneous PCA following major orthopaedic surgery

Purpose: To compare subcutaneous PCA tramadol with subcutaneous PCA morphine for postoperative pain relief after major orthopaedic surgery and for the incidence of side-effects. Methods: In a double-blind randomised controlled study 40 patients (20 in each group) self-administered either tramadol or morphine for 72 hr after surgery via sc PCA. The following variables were recorded at various time intervals: (I) pain score by means of a visual analogue scale, (ii) drug consumption and total PCA demands, (iii) vital signs (blood pressure and heart rate), (iv) oxygen saturation and respiratory rate, and (v) side-effects (sedation, nausea/vomiting, pruritus, urinary retention and constipation). Results: Both drugs provided effective analgesia. The mean consumption in the first 24 hr was 792 +/- 90 mg tramadol and 42 +/- 4 mg morphine. Thereafter, consumption of both drugs declined markedly Moderate haemodynamic changes were observed in both the tramadol and morphine groups (with a maximum 20% decrease in mean blood pressure and a maximum 17% increase in heart rate) during the 72 hr period. Both tramadol and morphine were associated with a clinically and statistically significant (P < 0.001) decrease in oxygen saturation, but without changes in respiratory rates. Desaturation was less ma-ked with tramadol, Tramadol appeared to cause more nausea and vomiting than morphine, Sedation was mild and only seen during the first few hours after surgery in both groups. Conclusion: Tramadol is an effective analgesic agent for the relief of acute postoperative pain when administered by PCA via the subcutaneous route. Under these conditions tramadol behaves much like morphine with a similar side-effect profile.