The impact of a multimodal approach to pre-emptive analgesia on postoperative pain and analgesic requirements for patients undergoing orthopaedic lower limb surgery at The Aga Khan University Hospital, Nairobi: a single blind randomised controlled trial

Study Objective: The aim of this study was to evaluate the postoperative morphine-sparing and pain reducing effects of a preemptive, multimodal, perioperative analgesic regimen incorporating the use of preincisional intrathecal blockade plus parenteral anti-inflammatory agents, in patients undergoing lower limb orthopaedic surgery. Study design: Prospective Single blinded Randomized Controlled Trial. Study setting: The Aga Khan Hospital, Nairobi, Kenya. Methods: 44 ASA physical status 1 and 2 patients undergoing lower limb orthopaedic surgery were randomly allocated into two groups of 22 patients each. Patients in the Intervention group were given a preincisional subarachnoid injection of 15mg hyperbaric Bupivacaine and 25mcg Fentanyl, plus, parenteral Paracetamol 20mg/kg and Diclofenac 1mg/kg. Patients in the Control group received a standardized general anaesthetic protocol consisting of Midazolam and Propofol, Oxygen, N2O, Isoflurane and cis-atracurium. Analgesia intraoperatively was maintained by remifentanil 0.1-0.3mcg/kg/min with Paracetamol 20mg/kg and Diclofenac 1mg/kg given at the end of surgery. PCA morphine 2mg/ml was instituted once the patient complained of pain. Intramuscular rescue doses of 10mg morphine were administered on patient request. Visual analog score (VAS) was used to assess pain over 48 hours, the cumulative PCA morphine dose and the total number of morphine rescue doses requested were calculated and compared for both groups. Results: 44 consecutive patients undergoing lower limb orthopaedic surgery completed the study (Intervention group, n=22; Control group n=22). The cumulative PCA morphine consumption at 2, 24 and 48 hours following patient first request for the control and intervention groups were 6.72 ± 6.33mg versus 5.72 ± 7.62mg ( P=0.6383), 19.682 ± 16.50mg versus 24.09 ± 17.83mg (P=0.3995), 34.409 ± 32.99mg versus 34.818 ± 23.11mg (P=0.9622) respectively. The mean difference in the number of Intramuscular 10mg morphine rescue doses requested by the patients between the control and intervention groups at 48 hours was 8.1818 ± 19.673 versus 3.2727 ± 9.228 (P=0.295). The median VAS at 2 hours was significantly lower in the intervention than control group, 5 ± 2.17 versus 3 ± 2.37 (P=0.0068). VAS at 6, 12, 24, 48 and 72 hours postoperatively were not significantly different between the two groups. The McGill pain questionnaire present pain intensity showed a significant difference between the control and intervention group, 2.31 ± 0.70 versus 1.81 ± 0.65 (P=0.00001). There was no significant difference in the pain rating index between the control and intervention group, 8.681 ± 2.46 versus 8.59 ± 2.30 (P= 0.8998). Conclusion: A non-statistically significant trend towards a 2.7 fold increase in the number of morphine rescue doses requested was seen in the Control group, suggesting that these patients experienced more pain than those in the Intervention group. These results suggest that a comprehensive pre-emptive multimodal analgesic intervention comprising of intrathecal neuraxial blockade and pre- and postincisional parenteral anti-inflammatory agents may reduce the hyperalgesic component of postsurgical pain