Effects of low dose intrathecal morphine on pulmonary function after major abdominal surgery under Remifentanil/propofol TCI anaesthesia

Olinga A, Joukovsky P, Engelman E, Verleije A, Velghe C-E, Barvais L, Ickx B

Background and goal of study

Respiratory function is markedly affected after major and painful abdominal surgery¹. We tested the hypothesis that under remifentanil/propofol TCI anaesthesia, providing intense analgesia with preoperative intrathecal low dose morphine will decrease the effects on postoperative respiratory function, over a 120-h follow-up period compared to IV morphine exclusively.

Material and methods

32 patients were randomly allocated to receive in a double blind fashion either intrathecal hyperbaric bupivacaine (1mg) alone (control group: CG) or intrathecal hyperbaric bupivacaine (1mg) and morphine 0.3mg (ITM). A TCI remifentanil/propofol anaesthesia was used. 30 minutes before end of surgery the CG received IV morphine 0.2mg/kg   and ITM received placebo. Postoperative management was identical in the two groups-IV patient-controlled analgesia with morphine. During the first 24-h respiratory rate (RR) was assessed and arterial blood gases were sampled and analysed. Measurements of forced expiratory volume in 1s (FEV1), vital capacity (VC), forced vital capacity, peak expiratory flow rate and pulse oxymetry were performed the day before surgery (baselines values) and postoperatively from day 1 until day 5. Morphine consumption was recorded.  Postoperative pain was tested at rest and while breathing deeply using a visual analog scale (VAS). Statistical analysis was performed and P < 0.05 was regarded as significant.

Results and discussions

No difference was found in the measurements of RR, PaCO2, FEV1, VC, FVC and PEFR. In the ITM the PaO2/FiO2 ratio was lower compared to the CG (291.94±86.39 versus 411.92±120.15) during the first 4-h (p<0.05). IV morphine consumption was lower in the ITM (18.5±17.94mg) compared to the CG (35.56±27.54mg) on the first postoperative day only (p<0.05).No difference was found in the VAS pain score.

Conclusions

Under remifentanil/propofol TCI anaesthesia intrathecal morphine (0.3mg) administered just before major abdominal surgery has no beneficial effects on postoperative respiratory function compared to a control group receiving only IV morphine. These results could be explained by the similar analgesia provided by both techniques.

References:1- Siafukas NM Thorax 1999;54: 458-465.