AUCArea under the curve SEMLS Single-event multilevel surgery AIM To compare diazepam use, muscle spasm, analgesia, and side effects when clonidine or fentanyl are added to epidural bupivacaine in children with cerebral palsy after multilevel orthopaedic surgery.METHOD Fifty children were prospectively randomized to receive clonidine (n=24, mean age 10y 10mo [SD 2y 11mo]) or fentanyl (n=26, mean age 10y 11mo [SD 2y 10mo]).RESULTS There was no difference in primary outcome measures: median diazepam use (fentanyl 0, interquartile range [IQR] 0-0; clonidine 0, IQR 0-0; p=0.46), any muscle spasm (no muscle spasms in: fentanyl, 36%; clonidine, 62%; p=0.11), painful muscle spasm (fentanyl 40%; clonidine 25%; p=0.46), or pain score ≥6 (none: fentanyl 44%; clonidine 42%; p=0.29). There were differences in secondary outcome measures: no vomiting (clonidine 63%; fentanyl 20%); vomiting occurred more frequently with fentanyl (32% vomited more than three times; clonidine none; p=0.001). Fentanyl resulted in more oxygen desaturation (at least two episodes: fentanyl 20%; clonidine 0; p<0.001). Clonidine resulted in lower mean (SD) area under the curve for systolic blood pressure (fentanyl 106.5 [11.0]; clonidine 95.7mmHg [7.9]) and heart rate (fentanyl 104.9 beats per minute [13.6]; clonidine 85.3 [11.5]; p<0.001).INTERPRETATION Clonidine and fentanyl provide adequate analgesia with low rates of muscle spasm, resulting in low diazepam use. The choice of epidural additive should be based upon the most tolerable side-effect profile.Cerebral palsy (CP) by definition is a disorder of movement and posture, caused by a non-progressive brain injury or lesion. 1 However, although the causative brain lesion is defined as a static encephalopathy, the musculoskeletal pathology in the limbs is progressive during the child's growth and maturation, with the development of contractures, bony torsion, and joint instability. Children with CP may undergo extensive orthopaedic surgery of the lower extremities to correct deformity and improve function. Single-event multilevel surgery (SEMLS), defined as at least one surgical procedure, performed on two different anatomical levels (hip, knee, or ankles), has been shown to result in dramatic improvements in gait and functioning, which are sustained at 5-year follow-up and reduce the need for serial surgeries and periods of rehabilitation. 2,3 Good pain control is important for patient comfort and facilitates early rehabilitation and discharge. Effective pain management is challenging because of multiple surgical incisions, associated comorbidities (chronic lung disease, risk of aspiration, epilepsy, gastro-oesophageal reflux), and impairments in communication and/or cognition that may make pain assessment difficult. In addition, the surgical nociceptive input is likely to lead to wind-up of spinal reflexes and worsening of muscle spasm 4 and possibly to an escalating pain-spasm cycle. Epidural analgesia is the preferred modality of regional anaesthesia in our institution but there are limited data...