Pain Control in Pediatric Posterior Spine Fusion Patients: The Effect of Gabapentin on Post-operative Opioid Use and Patient Satisfaction
Phase: PHASE4
Conditions: Pain, Postoperative
Sponsor: Oregon Health and Science University

 
 
 
Protocol Title: Pain Control in Pediatric Posterior Spine 
Fusion Patients: The Effect of Gabapentin on Post-
operative Opioid Use and Patient Satisfaction 
 
 
 
 
 
 
 
 
 
Principle Investigator: Matthew F. Halsey, MD 
Document Approval Date: July 18, 2018 
NCT#: 01977937 

Project Title: Pain Control in Pediatric Posterior Spine Fusion Patients: The Effect of Gabapentin on Post-
operative Opioid Use and Patient Satisfaction. 
Primary Investigator: Matthew F. Halsey, MD  
Primary Aims:  
To evaluate the pain control efficacy of gabapentin when added to a standard postoperative protocol in 
pediatric patients undergoing posterior spinal fusion for idiopathic or neurogenic scoliosis, using the 
visual analog scale (VAS - Appendix 1) and total dose/kg of opioid used during the postoperative period 
to determine differences in pain. 
Secondary Aims: 
To evaluate the effects of adding gabapentin on instances of opiate related side effects, duration of 
hospitalization, the amount of narcotics used postoperatively and overall family satisfaction with efforts 
to control postoperative pain. 
Introduction:  
Surgery for the correction of pediatric spine deformity results in significant post-operative pain 
that is challenging to the patients, their families and the staff caring for them. Numerous studies have 
tried to identify the best methods to control this pain including the use of opioid PCA, intravenous 
acetaminophen, epidural morphine, intravenous ketorolac and multimodal therapies. 1,2,3,4,5 These 
efforts have produced some successes yet there remain problems with poorly controlled pain and 
substantial adverse effects associated with each of these modalities. 
Recently, attention has turned to the use of gabapentin as a potential agent to improve peri-
operative pain control and to decrease the use of opioids.6 Originally used as an anticonvulsant 
medication, gabapentin is now commonly used to treat chronic, centrally-mediated neuropathic pain 
syndromes.8 It’s mechanism of action is to suppress spontaneous central neuronal firing thereby 
decreasing the pain associated with the central sensitization brought about by the peripheral tissue 
injury.7 
The impetus for this study is to re-evaluate the effectiveness of gabapentin in a randomized, 
double-blinded, controlled fashion similar to that used by Rusy et al8 but in the context of a more robust 
multi-modal postoperative pain management milieu.   
Methods: 
This will be a prospective, randomized, controlled and double-blinded study. Study candidates 
will be identified in clinical encounters which evaluate or diagnose idiopathic or neurogenic scoliosis in 
patients aged 10-19. Written, informed assent from each patient and consent from parents will be 
obtained at pre-operative visits in which posterior spinal fusion is the planned procedure. Inclusion 
criteria will be patients of age 10-19 with an ASA patient classification of I to III. Patients will be excluded 

from the study if they have a body mass index greater than or equal to 35.0,  will 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. Patients who cannot effectively use the PCA alone will be included in the study 
for analysis but will not be counted towards the calculated number of patients per study arm due to 
difficulty comparing their hydromorphone use with that of other patients. Many of these patients are 
projected to be neuromuscular patients, and to build on a relative parity of literature about post-
operative pain control in neuromuscular scoliosis RNCA will be used and all data recorded as with 
patients who can communicate their pain level.  
If patients choose to participate in the study, they will be randomized into either the 
experimental or control group using the following computer randomization applet: 
<www1.assumption.edu/users/avadum/applets/applets.html> 
Patients, caretakers and providers will be blinded to the group assignments. An electronic copy of the 
group assignments will be retained by researchers uninvolved in patient care, and patients will be 
known by an alphanumeric code in research files to maintain privacy of information. 
 
Medications and Patient Care Protocols: 
 
Following pre-operative hospital admission, all patients will be asked to record their initial pain 
level with the VAS tool prior to receiving standardized pre-operative medications. The VAS has been well 
verified in pediatric patients as a valid pain measure patients are capable of understanding and using 
reliably. Patients in both groups will receive one 12.5 mg/kg dose of IV acetaminophen. Additionally, 
patients in the experimental group will receive one 15 mg/kg dose of gabapentin while the control 
group will receive a placebo. Each time the gabapentin or placebo is administered it will be prepared by 
the OHSU research pharmacists so that providers will remain blinded to treatment assignment. These 
medications will be administered on a regimen so that each group and patient receive them 
approximately the same amount of time prior to surgery.  The placebo will be compounded by the 
research pharmacy and both the gabapentin and placebo will be in liquid form.   
 
Several intraoperative anesthetic medications will be protocolized including IV ketamine at 
5mcg/kg/min for 120 minutes and IV Ketorolac 0.5mg/kg up to 15mg(at the conclusion of the case), 
while propofol infusions and IV hydromorphone are titrated to desired effect.   Two surgeons, Dr. 
Matthew Halsey MD and Dr. Ronald Turker MD will perform all of the surgeries in this study, and all 
patients considered in this study will undergo a posterior spinal fusion procedure.  
 
Post-operative medication administration will also be protocolized.  Ketorolac will be continued at 
0.5mg/kg up to 15mg IV q6 for twelve total doses (including the intraoperative dose).  Once the 
Ketorolac doses are complete, the patient will receive Ibuprofen 10mg/kg up to 600mg PO q6 
scheduled. Hydromorphone PCA will be set at a basal dose of 0.002mg/kg/hr and demand dose of 
0.004mg/kg with an 8 minute lockout; the basal PCA dose will be administered for 24 hours. Once basal 
PCA is discontinued, administration of oxycodone 0.1-0.2mg/kg PO up to 15mg PO q4h as needed will be 

used in conjunction with the PCA demand dose. If the patient is able to tolerate PO oxycodone without 
emesis, after 24 hours the PCA will be completely removed but a rescue dose of Hydromorphone 
0.002mg IV q4 prn will remain.  Other as needed medications will include Valium 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 q6 hours 
will be administered after the patient’s IV is removed. All patients will receive 1 Senokot-S tablet and 
Miralax 0.8 g/kg up to 17g daily for bowel regimen.   
 
 
The dosing for Gabapentin, the study medication, is 10mg/kg PO q8h, beginning when the patient is 
admitted to his or her floor bed postoperatively.  This will be administered through postoperative day 
four.  Patients in the control group will receive equivolume doses of a placebo medication at the same 
administration intervals.   
 
For the entirety of hospitalization, nursing staff will regularly assess and monitor vital signs and 
POSS sedation using current protocols to ensure patient comfort and safety (POSS tool- Appendix 2).9 
Any POSS score of 3 or greater will be considered unacceptable and require specific actions including but 
not limited to closely monitoring respiratory status, sedation level, decreasing opioid dose, and 
administering naloxone. All rounding residents and doctors will have a checklist of the most common 
and most adverse gabapentin drug reactions when assessing patients. The most common reactions 
include peripheral edema, nausea/vomiting, viral disease, ataxia, dizziness, nystagmus, somnolence, 
hostile behavior, fatigue and fever. The most adverse reactions include Stevens-Johnson syndrome, drug 
hypersensitivity reactions, drug induced coma/seizure, and suicidal thoughts. These reactions will result 
in the gabapentin or placebo being stopped at the clinicians’ discretion. Nursing staff will also assess 
patient pain using the VAS, instructing patients to mark the laminated scale with a vertical line using a 
dry-erase market at the point which best corresponds to their pain level at that time. Nursing staff will 
be instructed on proper measurement, in millimeters from 0, or “no pain,” and will record the measured 
pain score in the patient’s electronic medical record. The VAS scale used in this study is a 10 cm line with 
anchors of “no pain” and “worst pain imaginable.”  The use of a VAS scale in pediatric pain management 
has been well verified.10,11,12,13 The assessment of pain level will be performed a minimum of once per 4 
hour period from 06:00 until 22:00 for the duration of hospitalization and recorded as the highest VAS 
score during each 4 hour period (6-10, 10-14, 14-18, 18-22). A minimum of 4 daily VAS score values will 
be recorded per patient.  
Patients will be discharged from the hospital upon meeting the following criteria: adequate PO 
intake, Foley catheter removal without urinary retention, ability to perform independent bed to toilet 
transfer and adequate pain control on oral medications defined as acceptable to the patient and family. 
(Upon discharge patients will be prescribed oral narcotics which will be counted at their first follow up 
appointment two weeks later.) 
Data Recording: 
 

 
VAS scores will be collected by nursing staff as described above. These laminated sheets will be 
kept with the patients’ charts. A nurse or doctor will also provide the parent or primary caregiver of 
each patient with a pain control satisfaction survey (Appendix 3) on the day of discharge to assess their 
overall understanding and satisfaction with the pain control efforts and efficacy in the hospital. These 
surveys will be collected prior to discharge and also kept with the patient chart. Documents will be 
collected daily by researchers and stored in a secure office on OHSU campus, in a building separate from 
any in which study patients will be receiving care. Upon discharge, all paper documents will be scanned 
into an electronic file. 
 
 
Each patient will have their own individual file kept on OHSU campus computers in the OHSU 
secured network with password permissions applied so that only study researchers have access to the 
information. All medication data will be obtained post-discharge by a review of the electronic 
medication administration report (MAR). PCA hydromorphone syringes used and syringes wasted will be 
counted and recorded. Patient weight, date of transition to oral pain medications, dates of admission, 
operation and discharge, episodes of documented nausea/emesis, instances of urinary retention 
requiring replacement of a catheter after removal or POSS ≥3 recorded in flow sheets will all also be 
retrieved from patients’ electronic medical records by study researchers uninvolved in patient care. VAS 
scores measured in millimeters from the start point and uploaded into electronic medical records by 
nursing staff will be collected. Furthermore, patients will be asked to bring their prescribed 
postoperative outpatient narcotics to their first follow up appointment after discharge for a pill count to 
determine the amount of medication used, and that count will conclude their participation in the study. 
Further follow up appointment data will not be collected. A data collection tool (Appendix 4) has been 
created to record study data in each patient’s electronic study file, and as mentioned above all patients 
will have an alphanumeric code assigned to their information instead of name for data analysis. 
 
Statistical Considerations and Analysis: 
 
Sample size (n) was calculated using a two-sided continuous outcome superiority trial model; n 
= f(α/2, β) × 2 × σ2 / (μ1 − μ2)2 where μ1 and μ2 are the mean outcome in the control and experimental 
group respectively, σ is the standard deviation; f(α, β) = [Φ-1(α) + Φ-1(β)]2; Φ-1 is the cumulative 
distribution function of a standardized normal deviation. Data will be collected for a minimum of a total 
of 50 total patients, with an equal number of patients in both the control and trial groups. Based on past 
history at OHSU Doernbecher Children’s Hospital and the number of annual operative scoliosis cases of 
the two participating surgeons it is estimated that it will take approximately 2 years to accumulate this 
number of study subjects. This n was reached by calculating a statistical study power β of 0.8 and α of 
0.05. The study has been powered to compare VAS scores, mg/kg of opiate use, and duration of 
hospitalization post-operatively.  
 
Calculations were designed to detect a difference in mean VAS score (μ1 − μ2)2 of 2 between 
study groups with a standard deviation σ of 2.5, which was calculated from the standard deviations in 
VAS score reported by Rusy et al.8 These values were chosen to reflect a clinically significant difference 

in pain. Prior studies have stated that variability of 12mm or less constitutes no clinical difference in 
patient pain, and that reduction in pain level of 20% correlates with mild improvement or minimal 
clinically important difference and 30% with notable improvement of patient pain. 12,14 It has also been 
documented that requests and use of additional analgesia increase as patients move through different 
stratifications of pain scores, with those having a score under 30mm rarely requesting additional 
medication and those with a score above 70mm requesting additional pain medication frequently.15 
Instances of severe pain, defined as a pain score of greater than 70mm will be recorded and compared 
between groups as well.  
 
The sample size of 55  patients was confirmed as a valid choice for this study using a continuous 
equivalence calculation to exclude a difference of VAS means of greater than 2.1 with a standard 
deviation of 2.5, β of 0.8 and α of 0.05. Additionally, calculations were performed to power the study for 
amount of opiate used. Provided a sample size of 25 patients per group, β of 0.8, α of 0.05, and standard 
deviation of .0046 mg/kg/h of hydromorphone used based on morphine equivalents using a conversion 
factor of 6.67 as in a prior study by Dampier et al16 this study will be able to detect a significant 
difference in hydromorphone use of .0037 mg/kg/h. Standard deviation estimates were used based on 
data from Rusy et al8 and Turan et al17 and morphine equivalents used to compare to those studies’ 
findings regarding the total daily opioid sparing effects of gabapentin and the significance of a 
cumulative decrease in morphine use after spinal surgery.   
 
The following previously developed and tested study power calculators were used:  
<http://www.sealedenvelope.com/power/continuous-superiority/>  
<http://www.sealedenvelope.com/power/continuous-equivalence/>  
 
Paired T-tests will be used to evaluate the study outcomes and hypotheses. The null hypotheses are as 
follows:  
1. There is no significant difference in pain control when adding gabapentin to a multimodal 
pain management protocol in pediatric post-operative posterior spinal fusion patients. 
 
2. There is no significant difference in the amount of opiate medication required for pain 
control in pediatric post-operative posterior spinal fusion patients.  
 
 
 
 
 
 
 
 
 
 
 

 
 
 
 
 
 
 
 
 
Appendix 1: VAS 
Visual Analog Pain Scale 
 
 
 
 
 
 
 
 
 
 
What does your pain feel like? 
 
                  No Pain                            
 
 
 
 
 
       Worst Pain 
 
 
 
 
 
 
 
 
 
 
       Imaginable 
 
 
 
 
 
 
 
 
 
 
 
 

 
 
 
Appendix 2: POSS 
Pasero Opioid‐induced Sedation Scale (POSS) 
S = Sleep, easy to arouse 
Acceptable; no action necessary; may increase opioid dose if needed 
 
1. Awake and alert 
Acceptable; no action necessary; may increase opioid dose if needed 
 
2. Slightly drowsy, easily aroused 
Acceptable; no action necessary; may increase opioid dose if needed 
 
3. Frequently drowsy, arousable, drifts off to sleep during conversation 
Unacceptable; monitor respiratory status and sedation level closely until sedation level is stable 
at less than 3 and respiratory status is satisfactory; decrease opioid dose 25% to 50% or notify 
prescriber or anesthesiologist for orders; consider administering a non‐sedating, opioid‐sparing 
non-opioid, such as acetaminophen or an NSAID, if not contraindicated. 
 
4. Somnolent, minimal or no response to verbal or physical stimulation 
Unacceptable; stop opioid; consider administering naloxone; notify prescriber or 
anesthesiologist; monitor respiratory status and sedation level closely until sedation level is 
stable at less than 3 and respiratory status is satisfactory. 
 
*Appropriate action is given in italics at each level of sedation. 
1Opioid analgesic orders or a hospital protocol should include the expectation that a nurse will 
decrease the opioid dose if a patient is excessively sedated. 
2For example, the physician, nurse practitioner, advanced practice nurse, or physician 
assistant responsible for the pain management prescription. 
3Mix 0.4 mg of naloxone and 10 mL of normal saline in syringe and administer this dilute 
solution very slowly (0.5 mL over 2 minutes) while observing the patient’s response (titrate to 
effect) (Source for naloxone administration: Pasero, Portenoy, McCaffery M. Opioid 
analgesics, in Pain: Clinical Manual [ed 2]. St. Louis, MO, Mosby 1999, p. 267; American Pain 
Society [APS]. Principles of Analgesic Use in the Treatment of Acute Pain and Chronic 
Cancer Pain [ed 5], Glenview, IL, APS, 2003.) 
4Hospital protocols should include the expectation that a nurse will administer naloxone to any 
patient suspected of having life-threatening opioid-induced sedation and respiratory 
depression. 
 
 
 
 
 
 
 
 
 

 
 
 
 
 
 
Appendix 3:   Parental Pain Perception Assessment Survey 
Study #____________  
Interview Date____________ 
 
Surgery Date____________ 
PARENT INFORMATION 
Sex:          Male □     Female □                      Age in years: 16-25 □   26-30 □   31-39 □ 
                                                                               40-49 □   50-59 □   60-69 □ 
Race/Ethnicity: Black □   White □   Hispanic □   Other □ 
Highest Level of Education:   Less than high school □   High school/GED □   Some college  □                         
College graduate □   Advanced Degree □ 
Marital Status:   Single □   Married □   Divorced □   Partnered □   Widowed □  
Relationship to Child:   Mother □   Father □   Stepmother □   Stepfather □   Grandparent □    
                                          Foster parent □   Other □ 
Child’s Health Status:   Excellent □   Very Good □   Good □   Fair □   Poor □ 
Does your child have any disabilities? 
 
 
ADMISSION 
 
The following questions apply to when your child was admitted to the hospital 
Was your child in pain when admitted to the hospital?   Yes □     No □ 
On admission, did your nurse ask you or a family member about how your child shows pain?    
                                                                                                    Yes □     No □ 
Does your child have a history of chronic pain?   Yes □     No □ 
PAIN HISTORY 
 
The following questions apply to previous hospitalizations 
Has your child been hospitalized before?   Yes □     No □ 
If yes, did your child experience pain during the hospitalization?   Yes □     No □ 
     Was the pain related to a procedure?   Yes □     No □ 
     Was the pain following surgery?   Yes □     No □ 
     During that hospitalization, how satisfied were you with your child’s pain control? 
     Very dissatisfied □     Somewhat dissatisfied □     Somewhat satisfied □     Very satisfied □ 
PARENTAL PRESENCE 
 
The following questions apply to this hospitalization 
During the past 24 hours, have you been able to be with your child… 
None of the time □   Some of the time □   Half of the time □   Most of the time □   All of the time □ 

During the past 24 hours, if you were able to be with your child was it… 
During the day □    During the evening □   During the night □   All □ 
 
 
CURRENT PAIN HISTORY 
 
The following questions are general questions related to pain during the hospitalization. 
How often did your child have pain in the past 24 hours? 
     None of the time □    Some of the time □    Most of the time □    All of the time □ 
On a scale of 0-10, zero meaning no pain and 10 meaning the worst pain imaginable, how often did your 
child experience a pain score of 4 or greater (this is considered moderate to severe pain)? 
     None of the time □    Some of the time □    Most of the time □    All of the time □ 
How often did the nurse promptly identify that your child was in pain? 
     None of the time □    Some of the time □    Most of the time □    All of the time □ 
How often did your child receive pain medication? 
     None of the time □    Some of the time □    Most of the time □    All of the time □ 
From your perspective, what type of pain medication did your child receive? 
                Pain Pump □        IV Medication □     Oral Medication □      Other  □ 
How often was the pain relieved with the medication? 
     None of the time □    Some of the time □    Most of the time □    All of the time □ 
How often did someone discuss different options to treat the pain when your child had pain? 
     None of the time □    Some of the time □    Most of the time □    All of the time □ 
How often did you receive enough information to understand the pain treatment plan? 
     None of the time □    Some of the time □    Most of the time □    All of the time □ 
How often were you or a family member included in decisions to change treatment of your child’s pain? 
     None of the time □    Some of the time □    Most of the time □    All of the time □ 
How often was there a prompt response to your worries or concerns regarding your child’s pain? 
     None of the time □    Some of the time □    Most of the time □    All of the time □ 
How often was there prompt treatment of your child’s pain? 
     None of the time □    Some of the time □    Most of the time □    All of the time □ 
How often did the nurse help calm and soothe your child using methods other than pain medication or 
involve child services? 
     None of the time □    Some of the time □    Most of the time □    All of the time □ 
How often did the nurse demonstrate caring behaviors to help you and your child with their pain? 
     None of the time □    Some of the time □    Most of the time □    All of the time □ 
How often did the nurse show they had adequate knowledge and skills to help your child with their 
pain? 
     None of the time □    Some of the time □    Most of the time □    All of the time □ 
How often did someone explain the pain relief plan when your child had pain? 
     None of the time □    Some of the time □    Most of the time □    All of the time □ 
How often did someone take the time to answer all your questions about treating pain? 
     None of the time □    Some of the time □    Most of the time □    All of the time □ 

 
What information would you have liked to receive or not receive? 
 
 
 
 
How often were you or a family member included in decisions on how best to treat your child’s pain? 
     None of the time □    Some of the time □    Most of the time □    All of the time □ 
How often was management of your child’s pain to your satisfaction? 
     None of the time □    Some of the time □    Most of the time □    All of the time □ 
SATISFACTION 
 
The following questions relate to your level of satisfaction with pain management and any 
recommendations for improvement.  
In the past 24 hours, how often were you satisfied with the providers’ communication with you? 
     None of the time □    Some of the time □    Most of the time □    All of the time □ 
For the past 24 hours, how satisfied are you with the overall management of your child’s pain? 
     Very dissatisfied □    Somewhat dissatisfied □   Somewhat satisfied □    Very satisfied □ 
Overall, how satisfied were you with pain control in the hospital?  
     Very dissatisfied □    Somewhat dissatisfied □   Somewhat satisfied □    Very satisfied □ 
Is there something we could have done differently to better manage your child’s pain? 
 
 
 
 
 
Other comments: 
 
 
 
 
 
 
 
 
 
Thank you for your participation! 
 
 
 
 
 
 
 
 

 
 
 
 
 
 
Appendix 4: Data Collection Tool 
 
 
 
 
 
 

 
                                                          
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