Pain Control in Pediatric Posterior Spine Fusion Patients: The Effect of Gabapentin

Patients aged 10-19 years with idiopathic scoliosis, and classified as American Society of
Anesthesiology (ASA) class I to III who intended to undergo posterior spinal fusion for
deformity correction were enrolled. Prior to surgery, subjects were randomized into either
the experimental or control group by the OHSU research pharmacy using an online randomization
tool, which utilized block randomization upon patient enrollment to result in equal sized
groups at study completion. Patients, caretakers and providers remained blinded to the group
assignments.

Patients filled out the Scoliosis Research Society, SRS-22 standardized form at a
pre-operative clinic appointment. Following hospital admission, patients recorded initial
pain level with the Visual Analog Scale (VAS) prior to receiving standardized pre-operative
medications. The VAS scale used in this study was a 10 cm line with anchors of "no pain" at
the left and "worst pain imaginable" at the right; each point was measured to the nearest
millimeter. In the post-operative period, nursing staff assessed patient pain using the VAS
at 4-hour intervals from 06:00 until 22:00 for the duration of hospitalization for a minimum
of 4 daily scores recorded per patient. After the third post-operative day, but before
discharge, the parent or guardian of each subject was asked to complete an IRB-approved
survey to measure parent demographics and parental satisfaction with the patient's
hospitalization and pain control.

Each patient received standardized medications according to our multimodal pain protocol.
Following hospital admission, patients in both groups received one 12.5 mg/kg dose of
intravenous (IV) acetaminophen. Patients in the experimental group received one 15 mg/kg dose
of liquid gabapentin while the control group received a placebo, formulated to match the
volume, color, taste, and smell of the experimental medication. The gabapentin or placebo was
prepared by the OHSU research pharmacists so that providers and investigators remained
blinded to treatment assignment. Several intraoperative anesthetic medications were given to
subjects in both groups including: IV ketamine at 5mcg/kg/min for 120 minutes and IV
Ketorolac 0.5mg/kg up to 15mg. Intra-operative IV propofol and IV hydromorphone were titrated
to desired effect.In the post-operative period, gabapentin was administered to the
experimental group at 10mg/kg PO q8h, beginning at Phase II and continued through
postoperative day four. The control group received equivalent volume doses of placebo at the
same intervals. Post-operative medication was administered according to the following
protocol for both groups: ketorolac continued at 0.5mg/kg up to 15mg IV q6h for 12 total
doses. Once ketorolac doses were complete, the patient may have received Ibuprofen 10mg/kg up
to 600mg PO as needed. Hydromorphone was given through patient-controlled analgesia (PCA) at
a basal dose of 0.002mg/kg/hr for 24 hours and demand dose of 0.004mg/kg with an 8-minute
lockout. Once basal PCA was discontinued, administration of oxycodone 0.1-0.2mg/kg PO up to
15mg PO q4h as needed supplemented the PCA demand dose. If the patient tolerated PO oxycodone
without emesis, the PCA hydromorphone was discontinued after 24 hours, but a rescue dose of
hydromorphone 0.002mg IV q4 was available if needed. Other as needed medications included
diazepam 0.15mg/kg up to 5mg PO q6h for muscle spasms, ondansetron 0.1mg/kg up to 4mg IV q12h
for nausea, and IV acetaminophen 12.5mg/kg up to 1000mg q6h. Acetaminophen 12.5mg/kg up to
650mg PO q6h hours was administered after the IV was removed. All patients received one
Senokot-S tablet and Miralax 0.8 g/kg up to 17g daily for bowel regimen.

For the entire hospitalization, nursing staff monitored vital signs and assessed sedation
using the standardized Pasero Opioid-induced Sedation Scale (POSS) protocols at 4-hour
intervals.16 Any POSS score of 3 or greater resulted in more frequent monitoring of
respiratory status and sedation level, decreased opioid dosing, and administration of
naloxone as needed. All patients were routinely monitored for known adverse gabapentin drug
reactions including: peripheral edema, nausea/emesis, viral disease, ataxia, dizziness,
nystagmus, somnolence, hostile behavior, fatigue and fever, Stevens-Johnson syndrome, drug
hypersensitivity reactions, drug induced coma/seizure, and suicidal thoughts. Any perceived
adverse reaction would have resulted in the gabapentin or placebo being stopped at the
clinicians' discretion

Inclusion Criteria:

- Patients of age 10-19 with an American Society of Anesthesiologists patient
classification of I to III undergoing surgery to correct idiopathic or neurogenic
scoliosis.

Exclusion Criteria:

- Patients who require a surgical approach or technique differing from posterior spinal
fusion and/or have allergies to any of the standardized or experimental study
medications: acetaminophen, gabapentin, hydromorphone, ketorolac or oxycodone.