Efficacy and side effects of small versus large bolus size morphine patient controlled analgesia combined with paracetamol

Introduction
Patient controlled analgesia (PCA) provides a better analgesia over conventional opioid treatment. The reduction of bolus size and its efficacy on pain relief and associated side effects were not enormously studied. This study was constructed to evaluate small versus traditional bolus size PCA, including pain relief, and side effects of both regimens.
Methods
Seventy-seven patients were included in the study. All patients received general anesthesia. Patients were randomly distributed between two groups; traditional group (M1) received a bolus dose of Morphine as 0.02 mg/kg body weight to a maximum of 1.5 mg, and group (M2) where 0.01 mg/kg body weight to a maximum of 0.75 mg is the bolus dose. PCA machines were set up at 6 min lockout interval and a maximum dose of 0.15 mg/kg/h to a maximum of 10 mg/h. Rescue doses were given according to pain scores and reported. 1000 mg Paracetamol every 6 h were given. Morphine consumption at 24 and 48 h, VAS at 1, 2 then every 4 h for 48 h were measured. Reported complications as respiratory depression, over sedation, constipation, pruritus, nausea and vomiting were analyzed.
Results
Morphine consumption in small bolus size group M2 during the first (36.38 ± 17.75) and second 24 h (30.22 ± 17.15) were less when compared to large bolus size group M1 (39.20 ± 17.97 and 36.38 ± 17.75), the change was insignificant. In spite of using small bolus size Morphine in group M2, pain scores were close to group M1 and statistically insignificant. The frequency of occurrence of side effects was statistically insignificant when comparing the two groups.
Conclusions
Small bolus size of Morphine PCA produces efficient pain relief but does not reduce total morphine consumption nor did morphine associate side effects.