Efficacy and safety of tramadol and morphine in patients with extremely severe postoperative pain

Tramadol is used for postoperative pain management. However, it is unknown whether tramadol has the same analgesic efficacy as morphine in patients with extremely severe pain. Respiratory depression and sedation by the applied drugs is of special interest.This prospective, randomised, double-blind study was performed as a pilot study. After standardised general anaesthesia, 20 patients with extremely severe postoperative pain — visual analogue scale ≥8 (VAS) — were allocated to intravenous pain treatment with either tramadol or morphine. The goal was to reduce pain intensity to VAS ≤1 during a four hour period. Pain intensities, vital parameters and side effects were recorded every 15 minutes. Sedation (four-point scale) and blood gases were controlled every 30 minutes. Oxygen saturation was continuously monitored by pulse oximetry. An oxygen saturation below 90% without oxygen supply was taken as respiratory depression. Statistical analysis was performed with the t-test for most of the numerical parameters. A p-value <0.05 was considered significant.Both drugs reduced pain intensities to VAS ≤1 within 135 minutes (median). Median dosages were 292.5 mg for tramadol (160–460 mg) and 27 mg for morphine (20–45.1 mg). Tramadol patients experienced significantly fewer severe side effects: two morphine patients had to be excluded from the efficacy analysis of the study: one for extreme sedation, the other because of severe respiratory depression. Minor side effects had a similar incidence.In conclusion, successful treatment of extremely severe postoperative pain was achieved with both tramadol and morphine. Drug dosages were significantly higher than usually administered. Tramadol patients experienced fewer severe side effects than morphine patients.