Use of Oral Pregabalin as Preemptive Analgesia in Abdominal Hysterectomy: Evaluation of Postoperative Pain and Opioid Consumption
Phase: PHASE4
Conditions: Pain, Postoperative, Analgesia, Gabapentin Adverse Reaction, Opioid Abuse
Sponsor: Universidade Federal de Alfenas

 
Use of oral pregabalina as preemptive analgesia in abdominal 
hysterectomy: evaluation of postoperative pain in a 
randomized clinical trial. 
 
 
 
Register Clinical Trials (clinicaltrials.gov): NCT04495374 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
January, 20, 2021 
 

METHODS 
Study design 
This study is revealed to be an experimental, randomized, double-blind, controlled 
placebo controlled clinical trial. The trial included only female patients, who would 
undergo abdominal hysterectomy surgery under spinal anesthesia, where after 
randomization as patients they were allocated into two groups, the placebo controlled 
group (P0) and the pregabalin 300 mg group (P1).  
The entire study had been carried out a research protocol in accordance with the 
recommendations of the Consolidated Standards of Reporting Trials (CONSORT). The 
revised CONSORT statement in 2010, consists of a list of 25 items in a table that 
configure a checklist with guidelines for the development of randomized clinical trials 
with parallel groups, this statement also contains a flowchart to guide the experimental 
design of the study.  
Study location and period  
All procedures, procedures and data collections for this study were carried out at 
Santa Casa de Alfenas - MG (Casa de Caridade Nossa Senhora do Perpétuo Socorro). 
The inclusion of patients in the study and the collection of data from September 2019 to 
September 2020.  
Sample population  
Initially the sample size was out of base from a pilot study carried out with 10 
patients, where establishing a 95% confidence level and a power above 80% using non-
parametric tests (Mann-Whitney test) for primary study outcomes, to decide to make an 
initial allocation of 51 patients in each study group, totaling 102 patients. These 10 
patients in the pilot study were also included in the final version of the study.  
Prepared to an atypical health scenario issued by the pandemic of COVID-19, 
during the year of 2020, in the month of September of that same year to choose to carry 
out new statistical analyzes with a population included so far in the study. From these 
new analyzes, the results obtained were statistic for the primary outcomes and due to 
difficulties imposed by the pandemic caused by the coronavirus, it was decided to 
interrupt the data collection at this time, totaling a total of 55 patients included in the 
study.  

The inclusion criteria are detailed below, where all are mandatory, and also the 
criteria and exclusion used to define the sample population.  
Inclusion criteria: (1) Female patients; (2) Age between 20 and 65 years; (3) 
Patients who will undergo elective abdominal hysterectomy surgery due to benign 
pathologies; (4) Be classified as physical status by the Society of Anesthesiologists (ASA) 
as ASA I (healthy individual) or ASA II (patient with mild and controlled systemic 
disease);  
Exclusion criteria: (1) Allergy or known intolerance to pregabalin or opioids; (2) 
Patients with chronic pain or fibromyalgia; (3) Patients on chronic use of opioids; (4) 
carriers of malignant neoplasms; (5) Pregnant women; (6) People with active 
uncontrolled cardiovascular disease; (7) Patients with kidney and / or liver disease; (8) 
Patients who have spinal deformities that make spinal anesthesia impossible; (9) Presence 
of coagulation disorders or anticoagulant therapy that cannot be suspended for surgery; 
(10) Presence of active sepsis;  
After accepting to participate in the study and signing the informed consent form, 
the sociodemographic data of all patients were collected through a questionnaire, for 
further analysis. 
Groups and interventions  
As this is a randomized clinical trial, this study was made up of two groups. The 
group P0, the group designated as placebo controlled, and the group P1, consisted of 
patients participating in the intervention group.  
Group P0: Received two placebo tablets composed of starch and aerosil (colloidal 
silicon dioxide).  
Group P1: They received two tablets identical to the tablets in group P0, but in 
this case, the tablets were each composed of pregabalin in the 150mg dosage, totaling a 
total dosage of 300mg of pregabalin.  
All tablets were made in the same pharmacy handling, under conditions provided 
for in good manufacturing practices, to avoid bias.  
 
 

Blinding  
In order to avoid measurement bias, after elaboration, the tablets were placed in 
opaque and sealed envelopes, being identified only as formula A or formula B. An 
external researcher, who was not involved in randomization or data collection, was 
responsible by blinding, being the only researcher to know the composition of each 
formula. At the end of the study, this researcher informed the rest of the team of the 
composition of each formula, with Formula A consisting of two tablets of 150 mg of 
pregabalin each, and Formula B consisting of two placebo tablets.  
Since the patients included in the study, the researcher responsible for medication 
randomization and administration, and also the researcher responsible for monitoring and 
collecting data, did not have knowledge about the composition of the interventions 
(formula A and formula B).  
Randomization  
After determining the sample population and preparing interventions in sealed and 
opaque envelopes, the randomization procedure had been carried out. To carry out the 
random allocation process, an external researcher was responsible for administering to 
the patient a sealed, opaque envelope containing the intervention (placebo or pregabalin 
300mg) over a period of 02 hours prior to the start of the anesthetic-surgical procedure, 
with randomization it was simple, carried out by entering the study, where the first patient 
to be admitted to the study received formula A intervention, and the second received 
formula B, and so on. Another researcher was responsible for the patient's perioperative 
follow-up and data collection. 
Experimental draw  
A total of 58 patients were selected for the research. After randomization, 30 
patients were allocated to the P0 group (placebo), but during the follow-up two were 
excluded, one due to the use of subarachnoid morphine and the other due to the use of 
analgesic medications (tramadol) in the immediate postoperative period, which was not 
included in the study protocol. In the P1 group (pregabalin 300mg), 28 patients were 
allocated, in which one patient had to be excluded due to the use of subarachnoid 
morphine during anesthesia. Thus, the analyzes were performed with a total of 28 patients 
in the P0 group and a total of 27 patients in the P1 group. 

Evaluation procedures and measures  
After the patient inclusion process, blinding and random allocation to groups were 
carried out. The patients participating in the P0 group received a sealed envelope 
containing two placebo tablets, while patients belonging to the P1 group received an 
identical envelope containing two tablets of 150mg pregabalin each, all tablets were 
administered within two hours prior to the start of surgery. , in the nursing room where 
the patients were hospitalized. 
 In the operating room, venoclysis was performed with jelco No. 18 or No. 20, and 
an infusion of 08 ml.kg-1 of crystalloid solution (lactated ringer). The patients were 
properly monitored with pulse oximetry, cardioscope, and non-invasive blood pressure 
monitor. After monitoring, patients were premedicated with intravenous (IV) midazolam 
at a dosage of 0.03 mg.kg-1  
To perform spinal anesthesia, the patients were seated on the surgical stretcher by 
the nursing team. Asepsis and antisepsis were performed at the puncture site with 
alcoholic chlorhexidine solution. After placement of sterile drapes, local anesthesia was 
performed with 2.0% lidocaine without vasoconstrictor. The first attempt at subarachnoid 
puncture was performed, using the median technique, between the intervertebral levels 
L3-L4 or L4-L5 or L5-S1, with a 25G Quincke needle for subarachnoid anesthesia. In 
case of technical difficulty in the puncture, the paramedian puncture technique was 
chosen. The confirmation of the correct puncture was based on the aspiration of 
cerebrospinal fluid. Anesthesia was performed with the local anesthetic 0.5% bupivacaine 
at a dosage of 0.3 mg.kg-1, injected from a 5 ml disposable syringe. After anesthesia, the 
patients were placed in the supine position, and the correct level of anesthesia was proven 
with thermal sensitivity tests using cotton soaked with alcoholic solution. After the 
anesthesia reached the sensory level of the T4 thoracic vertebra, the surgical team was 
allowed to start the procedure. Prior to the beginning of the surgical incision, a delayed 
bladder probe was performed in all patients according to the surgeon's indication. All 
surgeries were performed by the same team of surgeons.  
Hemodynamic changes in blood pressure were controlled with the use of 
vasoactive medications such as ephedrine or metaraminol. For prophylaxis of 
postoperative nausea and vomiting (PONV) ondansetron was administered at a dosage of 
4 mg intravenously (IV) 30 minutes before the end of surgery. It was prescribed for all 

tenoxicam patients at a dosage of 20 mg IV at regular intervals every 12 hours for the 
purpose of anti-inflammatory and analgesic action. For analgesic relief, dipyrone IV was 
also prescribed at a dosage of 50 mg.kg-1 at regular intervals every 6 hours. During the 
surgery, and also at the end of the surgery, the patients were evaluated for the degree of 
sedation using the Ramsay sedation scale as a basis.  
At the end of the surgery, the patients were referred to the PACU, where they were 
monitored again, and went through the pain assessment process using the visual analog 
scale (VAS) in relation to pain at rest and “movement” (the patient was asked to perform 
the forced cough movement), through a direct question with scale demonstration. Pain 
characterized as mild (0 - 2 VAS) received no medication, in addition to those already 
prescribed; pain characterized as moderate (3 - 7 EVA) received IV morphine at a dosage 
of 0.025 mg.kg-1; and severe pain (8 - 10 VAS) received IV morphine at a dosage of 0.05 
mg.kg-1 every 01 h until analgesic control. To be considered able to be discharged from 
the PACU for clinical follow-up in wards, patients should reach a score ≥ 9 on the 
modified Aldrete Scale (Table 3) and have VAS pain scores ≤ 2. 
Upon arriving at the infirmary, patients were periodically evaluated at regular 
intervals in relation to the intensity of pain, with the help of a team of properly trained 
and qualified nurses. For patients who presented moderate-intensity pain (VAS ≥ 2 <8) 
or pain classified as severe (VAS ≥ 8), IV morphine was administered at a dose of 1 mg 
and 2 mg, respectively, according to a medical prescription. All analgesic medications 
used were recorded in the patient's medical record. 24 h after discharge from the PACU, 
in the ward, the patient was evaluated by the same examiner who performed the 
evaluation in the PACU, who again performed the stratification of pain by VAS and an 
evaluation with the McGill questionnaire.  
During the entire hospitalization period of the study patients, the use of CNS 
depressant drugs (example: ketamine, droperidol, promethazine) and / or analgesic drugs 
that are not included in the study protocol was avoided. If any of the patients were 
medicated with such drugs, they would be excluded from the study to avoid bias in the 
statistical analysis. The data related to surgery (pre, trans and postoperative) were 
collected for statistical analysis, according to Annex II, in which, for example, the total 
duration of surgery in minutes was described; the total of intravenous fluids infused; the 
values of mean arterial pressure and heart rate in the pre, intra and postoperative period; 

the presence or not, as well as the quantity, of PONV in the PACU and after 24h; presence 
or not of dizziness as a possible side effect, among others. 
Outcomes  
The primary outcome was the assessment of postoperative pain using two 
different scales, the traditional visual analog scale (VAS) and the McGill Pain 
Questionnaire. The secondary outcome was the comparative analysis between the groups 
of opioid consumption in the postoperative period, evaluating both the total dosage of 
opioids used, as well as the time between the end of surgery and the request for the first 
analgesic rescue dose.  
Other outcomes that were analyzed, apart from the variation in patients' 
hemodynamic data during the surgical times (pre, intra and immediate postoperative 
period), the degree of sedation was also evaluated using the Ramsay scale, and the 
presence of side effects such as nausea and vomiting, itching and dizziness. Other 
independent variables were analyzed, such as age, weight, body mass index, education 
level, profession, family income.  
Ethical aspects and records  
This study with the objective of preserving the patients' physical and 
psychological integrity followed the statements enunciated by the Declaration of 
Helsinki. All patients previously admitted to the study were clarified about the 
methodological process, the randomization and blinding process, the guarantee of 
confidentiality, about possible side effects of the interventions and also about the risks 
and benefits of participating in the study and the consent costs for participation in it. After 
clarifying any doubts and consenting to the patients' participation, the free and informed 
consent form (ICF) was signed, to which one of the copies was delivered to the patient 
and another copy was filed with the study researchers.  
According to Resolution No. 466 of December 12, 2012, of the National Health 
Council, which addresses the guidelines and regulatory standards for research involving 
human beings, this study was approved by the Research Ethics Committee (CEP) of 
UNIFAL- MG under opinion number 3,334,050 on June 17, 2019 (ANNEX IV). This 
research was also recorded in the North American database for the registration of clinical 
trials, Clinical Trials (clinicaltrials.gov), under the protocol NCT04495374.  

Statistical analysis  
Descriptive analysis (median, mean and standard deviation) was performed for 
continuous variables that followed a standard distribution, and these were expressed in a 
table.  
When analyzing parametric variables, the t test was used, and in comparisons 
between groups, the t test was used for independent samples, and in the analysis of data 
at different points in time between patients in the same group, we chose to use the test. t 
paired.  
When evaluating non-parametric variables, the Mann-Whitney test was chosen. 
To compare numerical measurements between the times in each group, the Wilcoxon test 
was used for the related samples. To assess qualitative variables, Pearson's chi-square test 
or Fisher's exact test was chosen.  
All data obtained were digitized and analyzed using the Statistic® 7.0 software, 
with a significance level of 5% (p <0.05). For the elaboration of statistical graphs, the 
program used was the GraphPad Prism version 5.00 (Trial) of 2007.