Conditions: Pain, Phantom Pain, Neuropathic
Keywords: Amputation Post-amputation Pain Neuropathic pain Valproic Acid Anesthesia, Conduction Neuralgia, stump
Allocation: RANDOMIZED | Intervention model: PARALLEL
Enrollment: 128
Healthy volunteers: no

Brief summary:
The objectives of this study are, to test the effectiveness of Valproic Acid (VPA) in the prevention of chronic neuropathic and post-amputation pain, as well as to further define the underlying inflammatory and epigenetic mechanisms that lead to the development of such chronic pain.

HYPOTHESES AND QUESTIONS

Hypothesis 1: The use of oral valproic acid in combination with regional anesthesia in surgical limb-injury patients will decrease the incidence of chronic nerve injury and post-amputation pain.

Goal 1: In a blinded, randomized placebo-controlled, multi-center clinical trial, investigators will determine if oral VPA added to regional anesthesia and standard perioperative management will reduce the incidence of nerve injury and post-amputation pain when compared with regional anesthesia alone.

Hypothesis 2: The transition from acute to chronic pain is mediated via epigenetic mechanisms (differential DNA methylation) in genes involved in nociception.

Goal 2: Investigators will analyze the DNA methylation patterns of patients with different types of neuropathic and post-amputation pain and determine if they are altered by VPA.

Detailed description:
RESEARCH DESIGN

This study will be a prospective, randomized, double-blinded, placebo-controlled trial to test the efficacy of valproic acid (VPA) in reducing the incidence of chronic neuropathic and post-amputation pain following amputation, stump revision, and surgery for limb injury with neurologic damage. Patients randomized to the "Control arm" of the trial, will receive standard regional anesthesia catheters (either peripheral nerve or epidural catheter), anesthetic management and a placebo. Patients randomized to the "Intervention arm" of the trial will receive standard regional anesthesia catheters (either peripheral nerve or epidural catheter), anesthetic management, and valproic acid 250mg preoperatively, and then three times per day for either 6 days post-operatively or until the time of discharge.

METHODOLOGY

The enrollment goal for the study (from all sites) will be 224 patients. Subjects will be recruited from the surgical clinics and the anesthesia pre-operative clinic. Outcomes for patients in the intervention arm will be compared with those managed with the current institutional standards of care including regional anesthesia catheter infusions. The study team anticipates a 10% drop-out rate at 3 months secondary to death and loss to follow up. Thus 202 evaluable patients (101 patients in each arm) at 3 months after surgery will be included in this study.

After screening and enrollment, the study medication (VPA or placebo) will be administered. Research blood samples will be collected preoperatively, postoperatively (at the completion of study drug administration, and at the Amputation Clinic follow-up for expression analysis. The third and final blood draw will be taken at the 3 month follow up. If patient is unavailable the research team will make accommodations to collect blood sample at the 6 month follow up or at a time of maximal patient convenience, not to exceed 18 months from study enrollment. All samples will be de-identified and subsequently studied in our laboratory and core facilities at Duke. Study specific questionnaires will be administered during the hospital stay, at 1 month (via mail), at 3 months (in clinic) and at 6 months (in clinic when possible).

RANDOMIZATION AND TREATMENT

Randomization will be stratified by site and by surgical etiology. At the time of enrollment, subjects will be assigned to one of three surgical categories on the randomization assignment log: amputation, stump revision, or surgery for limb injury with neurologic damage. Prior to surgery, the Investigational Drug Pharmacist will dispense the study medication in liquid form and the container will be labeled "study drug" with no indication of the liquid contents. The pharmacist will be the only person aware of the treatment allocation. At the end of the trial, once endpoint adjudication has been completed for all study subjects, the study data and treatment allocation will be un-blinded. Initial drug administration will be performed prior to induction of anesthesia on the day of surgery. Subsequent doses will be administered at the bedside by the ICU or floor nurse depending on patient location. Participants will complete study drug administration unless they withdraw their consent or either their treating physician or the principal investigator believes it would be dangerous to continue valproic acid. If the subject withdraws during the administration of VPA, they will continue with their current medical regimen without alteration.

DATA ANALYSIS PLAN

The primary endpoint is the incidence of chronic pain at the 3 months or time of final adjudication evaluation point, and the chronic pain will be defined as an S-LANSS average pain score of 3 points or greater. Secondary endpoints will include the numeric scores from forms BPI, S-LANSS, and DVPRS and the change in these scores from baseline to 3 months or time of final adjudication, as well as the incidence of neuropathic limb or post-amputation pain at enrollment and 3 months or time of final adjudication. Frequency and percentage of the categorical variables in above endpoints will be reported by treatment arm and by assessed time. Mean, standard deviation and range of the mean scales of the above forms, as well as the changes of mean scales from baseline will be computed by arm and by assessed time. Two-sample chi-square tests will be used to assess the treatment difference of the primary endpoint and post-amputation pain (or neuropathic pain) at each time. Logistic regression will be applied to investigate the treatment difference on the primary endpoint and post-amputation pain by adjusting for potential prognostic variables including baseline pain level, study site, type of surgery, diabetes, and intervening therapies. Similar analyses will be carried out in study sub-groups of site, surgery type, and diabetic status. Two sample t-tests will be used to assess treatment difference in changes of mean scales from baseline. In addition, linear regression will be used to assess the treatment difference on changes of mean scales from baseline by adjusting for covariants. P values of less than 0.05 will be considered to indicate statistical significance. Intent-to-treat analysis will be performed. Sensitivity analyses will also be carried out by excluding patients who drop out before 3 month post-surgery. If the dropout rate is larger than 10% and if there is evidence that the missing mechanism is not MCAR (missing completely at random) but MAR (missing at random), multiple imputation will be conducted. RASS will be used during hospitalization to define any changes in sedation between study groups during drug administration.

Analysis of clinical study data will be carried out with a de-identified download from REDCap. All of these data shared with the Duke Center for Human Genetics (CHG) will be fully stripped of all 18 Health Insurance Portability and Accountability Act (HIPAA)identifiers (ID). Private health information of study participants will be respected and all data analysis will be done in blinded fashion, such that individuals will not be identifiable from the final analysis dataset. Each patient will be allocated a study ID number when they sign a consent form, and thereafter will be referred to by that number. Investigators will have secure password protected access to REDCap in order to enter data. The dataset and biorepository will be fully de-identified once the dataset is complete and locked.

Research blood samples are tracked and stored within our existing Laboratory Inventory Management System. All specimens are identified by barcode and are not identifiable except via a coding table held securely at Duke University Medical Center (DUMC), Durham Veterans Administration Medical Center (VAMC) and Walter Reed National Military Medical Center (WRNMMC) respectively.

Arms:
arm 1: Cherry Syrup: Patients randomized to the "Control arm" of the trial will receive standard regional anesthesia catheters (either peripheral nerve or epidural catheter), anesthetic management and the placebo. arm 2: "Intervention arm" patients will receive standard regional anesthesia catheters (either peripheral nerve or epidural catheter), anesthetic management, and valproic acid.

Interventions: intervention 1: Valproic Acid intervention 2: Cherry Syrup
Intervention descriptions: intervention 1: "Intervention" patients will receive standard regional anesthesia catheters (either peripheral nerve or epidural catheter), anesthetic management and oral valproic acid 250mg preoperatively, then three times per day for either 6 days post-operatively or until discharge from the hospital. intervention 2: Intervention arm patients will receive standard regional anesthesia catheters (either peripheral nerve or epidural catheter), anesthetic management, and valproic acid 250mg preoperatively, and then three times per day for 6 days post-operatively.

Protocol document:
Prot_SAP_000.pdf: 
 
 
 
Study Protocol and Statistical Analysis Plan 
Regional Anesthesia and Valproate Sodium for the Prevention of 
Chronic Post-Amputation Pain  
NCT01928849 
Document date 09/25/2018 
 
 
 
 
 
 
 
 
 
 
 
 
 


This randomized controlled trial was conducted as part of an ongoing collaborative 
research initiative (Veterans Integrated Pain Evaluation Research (VIPER)) between 
Duke University Medical Center, Walter Reed National Military Medical Center 
(WRNMMC) and the Durham Veterans Affairs Medical Center (VAMC). The trial was 
designed to determine the extent to which the addition of oral valproic acid to regional 
anesthetic blockade (either peripheral nerve or epidural) and multimodal perioperative 
care decreases the incidence of chronic pain 3 months after amputation or amputation 
revision surgery. We also analyzed the trajectory of pain and functional recovery after 
surgery as well as epigenetic mechanisms associated with the development of chronic 
pain after nerve injury. Findings from the epigenetic analysis will be reported separately.  
 
Patient Recruitment: 
Prior to enrollment, the clinical trial was approved by the respective institutional review 
boards at WRNMMC, Durham VAMC, and Duke University Medical Center and the trial 
was registered at ClinicalTrials.gov (NCT01928849). Patients scheduled for surgical 
amputation or revision were screened for trial participation at the three Medical Centers 
from 2013 to 2017. 
 
Among those who were screened, a significant number had been added to the surgical 
schedules in a non-elective fashion at the Durham VAMC and Duke University Medical 
Center, and were not able to be approached for consent in a non-pressured 
environment given the short interim period between scheduling and surgery.  Similarly, 


patients scheduled for amputations following trauma were often excluded because of 
the urgency of surgery. 
 
Inclusion/Exclusion: 
Criteria for inclusion were individuals, age 18 years and older presenting for amputation, 
stump revision, or surgery for mangled limb (defined as limb injury with sensory or 
motor deficits consistent with injury to a major nerve). 
 
Criteria for exclusion were severe traumatic brain injury, significant cognitive deficits or 
dementia of any cause, substantial hearing loss without alternative means of 
communication, spinal cord injury with permanent deficits, current pregnancy or 
lactation, end-stage liver disease or hepatic encephalopathy, current therapy with 
valproic acid or other valproates, coumadin, chlorpromazine, olanzapine, zidovudine, or 
monoamine oxide inhibitors (medications affected by valproic acid metabolism), 
diagnosis of seizure disorder requiring anti-epileptic medication, current therapy with 
tricyclic antidepressants doses greater than 50mg/day, current diagnosis of malaria 
requiring anti-malaria medication, or allergy to valproates or valproic acid.  
 
Randomization: 
After enrollment, randomization was performed within the respective investigational 
drug pharmacy according to the schedule provided by our statistician. Randomization 
was stratified by site and surgical intervention, ie, amputation, amputation revision, or 
surgery for mangled limb with equal probability of assignment to the valproic acid group 


or the controlled placebo group. Patients, investigators, treating medical/surgical team, 
and study personnel were blinded to the assignment.  
At each of the study sites, following randomization, an order was placed to the 
Investigational Drug Service (IDS). The IDS pharmacist then assigned treatment class 
according to the randomization schedule previously provided by the statistician. The 
pharmacist then dispensed the study medication (cherry-flavored liquid or similar 
flavored valproic acid liquid) in single-dose containers labeled with the patient ID# and 
no indication of the liquid contents. At the time of surgery, the labeled study medication 
was transported by the research coordinator to the patient in the pre-operative area 
where the first dose of medication was administered by the anesthesia team. 
Subsequent doses were delivered to the nurse on the patient ward or intensive care unit 
(depending on patient disposition). The IDS retained records of study drug inventory, 
dispensing records, and intervention allocation. Study drug reconciliation was closely 
monitored for compliance in the medication administration record. The Investigational 
Drug Pharmacist was the only person aware of treatment allocation until the close and 
unblinding of the study data for analysis. 
 
 
Intervention / Treatment 
The study medication (valproic acid oral solution 250 mg per 5 mL or placebo (similar 
tasting flavored syrup) was then administered in single-dispense units. The initial dose 
was given by the perioperative anesthesia team. Subsequent doses were stored on the 
hospital ward or in the ICU with the patient’s other medications and administered by the 


nurse every 8 hours, up to 7 days or until time of patient discharge from the hospital, 
whichever came first. Blinding was kept intact throughout the study for all patients. 
 
Patients in both the placebo and intervention study arms received regional anesthesia 
(either peripheral nerve or epidural), with multimodal perioperative management 
according to the standard of care at each of the three institutions. Research blood 
samples were collected preoperatively, postoperatively (at the end of treatment with 
study drug or placebo), and at clinic follow-up (3 months or at time of adjudication). 
Valproic acid levels were measured at the completion of drug administration to confirm 
study compliance.  
 
Clinical Assessment Tools: 
Clinical assessments were performed at enrollment, daily during hospitalization, and at 
clinic follow-up (3 months). If a patient was not available at 3 months to collect 
adjudication data, the study outcome was determined at the 6-month research visit. 
Assessment tools for pain and function included the Numeric Rating Scale (NRS), a 0-
10 integer scale of pain intensity where 0/10 represents no pain and 10/10 represents 
the worst imaginable pain, the Brief Pain inventory, short form(BPI) (1) and the Defense 
and Veterans Pain Rating Scale (DVPRS) (2). Phantom and/or residual limb pain was 
assessed using the Groningen Questionnaire Problems Leg Amputation (GQPLA) 
questions (3). Neuropathic pain was measured using the Self-Reported Leeds 
Assessment of Neuropathic Symptoms and Signs (S-LANSS) tool (4,5). The presence 
of complex regional pain syndrome was determined using the Budapest Clinical Criteria 


(6). Opioid and medication use was evaluated preoperatively, during hospitalization, 
and at the final outcome determination. 
 
Physical Exam: 
A physical exam of the surgical site was performed when possible, ie, without wound 
dressing). If a prosthesis was present, it was removed for the exam. If the site was not 
accessible at the 3-month follow-up visit, the exam was attempted again at 6 months. 
The exam included visual inspection for asymmetry of sweating, color, skin changes, 
and hair growth. Allodynia was tested with cotton wool brushing. The presence of a 
Tinel’s sign was assessed by tapping on the most painful area and asking the patient if 
(s)he experienced any “sensations of pins and needles”. Sensory and motor deficits 
were also noted. 
 
Adjudication of Clinical Endpoint: 
An adjudication committee consisting of Drs Buchheit, Van de Ven and Hsia met for 8 
sessions between March 2014 and November 2017. All 3 members were required to be 
present for a quorum and a majority vote determined the phenotypic endpoint. At these 
meetings, the post-amputation pain subtypes were adjudicated using the Duke Post-
Amputation Pain Algorithm (7). 
 
 
 
 


STATISTICAL ANALYSIS: 
Patient data were collected from patients at all study sites and entered into Research 
Electronic Data Capture (REDCap)TM. Data were analyzed using SAS version 9.4 (SAS 
Inc., Cary, NC).  
 
Patient characteristics were summarized by treatment group using mean (SD) or 
median [Q1, Q3] for numeric variables and count (%) for categorical variables to assess 
randomization and ensure balance between treatment groups. We also compared the 
patient characteristics between those who did and did not return for follow-up to 
evaluate the possibility of response bias. Finally, plasma levels of valproic acid (VPA) 
were monitored to verify treatment adherence, and to determine the concentrations of 
VPA among treated patients. 
 
The incidence of chronic pain, the primary endpoint, was reported by treatment arm and 
compared using a two-sample chi-square test and multivariable logistic regression 
adjusting for baseline pain severity, type of surgery (amputation, revision, other), and 
surgical indication (medical vs. trauma). We also investigated possible differences in 
treatment effect within patient sub-groups based on study site, surgery type, and reason 
for surgery.  
 
Secondary endpoints and analysis of functional trajectory were planned including the 
change in BPI (pain and interference scores), DVPRS (pain and supplemental scores), 
opioid use, and neuropathic pain subtypes from baseline to time of adjudication 


endpoint.  Median [Q1, Q3] of the changes of mean scales from baseline was computed 
by arm and by assessed time between the two treatment groups via Wilcoxon rank sum 
test, and overall by the Wilcoxon signed rank test. Frequency and percentage of the 
categorical variables in above endpoints was reported overall, by treatment arm, and by 
assessed time.  Total opioid consumption during the first and second postoperative day 
was summarized via median [Q1, Q3], and compared between groups via Wilcoxon 
rank sum test. Rates of mortalities, liver disorders, and infections was summarized by 
group and compared by Fisher exact or chi-square tests as appropriate to evaluate 
safety of valproic acid administration. 
 
Sample size was calculated for the primary endpoint based on the assumption that 65% 
of the non-treatment arm patients will experience significant chronic pain (NRS ≥3/10, 
averaged over previous week). We believed these estimates to be conservative, based 
on this group’s prior research cohort (7) and prior literature demonstrating a phantom 
pain incidence as high as 79% in amputees from various causes Ephraim, 2005. With a 
12% drop-out rate at 3 months secondary to death and loss to follow up, and a type 1 
error rate of 0.05, the planned study of 224 patients would have 83% power to detect a 
difference in the incidence of chronic pain of 20% (45% vs 65%) between two arms 
using a two-sided chi-square test. Due to difficulties in enrollment the study was 
stopped early after 107 patients completed the primary endpoint evaluation. 
 
 
 
 
 
 


References 
1. 
Keller S, Bann CM, Dodd SL, Schein J, Mendoza TR, Cleeland CS. Validity of the 
brief pain inventory for use in documenting the outcomes of patients with 
noncancer pain. Clin J Pain. 2004 ed. 2004 Sep-Oct;20(5):309–18.  
2. 
Buckenmaier CC, Galloway KT, Polomano RC, McDuffie M, Kwon N, Gallagher 
RM. Preliminary validation of the Defense and Veterans Pain Rating Scale 
(DVPRS) in a military population. Pain medicine (Malden, Mass). The Oxford 
University Press; 2013 Jan;14(1):110–23.  
3. 
van der Schans CP, Geertzen JH, Schoppen T, Dijkstra PU. Phantom pain and 
health-related quality of life in lower limb amputees. J Pain Symptom Manage. 
2002nd ed. 2002 Oct;24(4):429–36.  
4. 
Bennett MI, Smith BH, Torrance N, Potter J. The S-LANSS score for identifying 
pain of predominantly neuropathic origin: validation for use in clinical and postal 
research. J Pain. 2005 ed. 2005 Mar;6(3):149–58.  
5. 
Clarke C, Lindsay DR, Pyati S, Buchheit T. Residual Limb Pain Is Not a 
Diagnosis: A Proposed Algorithm to Classify Postamputation Pain. Clin J Pain. 
2013 ed. 2013 Jan 16.  
6. 
Harden RN, Bruehl S, Perez RSGM, Birklein F, Marinus J, Maihofner C, et al. 
Validation of proposed diagnostic criteria (the “Budapest Criteria”) for Complex 
Regional Pain Syndrome. Pain. 2010 ed. 2010 Aug;150(2):268–74.  
7. 
Buchheit T, Van de Ven T, John Hsia H-L, McDuffie M, MacLeod DB, White W, et 
al. Pain Phenotypes and Associated Clinical Risk Factors Following Traumatic 
Amputation: Results from Veterans Integrated Pain Evaluation Research (VIPER). 
Pain medicine (Malden, Mass). 2015 Jul 14;17(1):149–61.