Opioid-based Versus Opioid-free Anaesthesia for Laparoscopic Cholecystectomy

Opioid-based (OA) Versus Opioid-free Anaesthesia (OFA) for General Surgical procedures in a developing country.

Introduction:

Opioids and their synthetic derivatives were first used in anesthesia in 1962. They are now routinely dispensed via different routes of administration including oral, subcutaneous, intravenous, intramuscular, transdermal, epidural or intrathecal. In the last 20 years, the world has witnessed a substantial increase in the consumption of opioids. Opioids over prescription is one of the causative factors of opioid crisis in North America. The current global opioid crisis has multifactorial reasons, and this is gradually worsened due to the different waves of liberal opioid use. The ongoing opioid crisis has led to the development of alternative techniques like opioid sparing and opioid-free anaesthesia strategies. Owing to the well-researched and recognized opioid-based anaesthesia adverse effects, it is essential to develop alternative therapies to achieve the main benefits of opioids like analgesia and haemodynamic stability, while limiting the opioid related adverse effects. A sensible use of opioids in the perioperative period is important since vulnerable patients undergoing common general surgical procedures become chronic opioid users postoperatively. High doses of perioperative opioids can be associated with increased post-operative complications including respiratory depression, paralytic ileus, nausea and vomiting, difficulty voiding, pruritus, hyperalgesia and opioid tolerance. These can atypically increases the length of hospital stay (LOS) due to delayed patient recovery, prolonged PACU stay, delayed discharge and unanticipated hospitalization; thus overall compromising the quality of recovery (QoR) and putting unnecessary burden on both the patients' and hospital resources.

Opioid-free anesthesia(OFA) is a method that entirely eliminates the use of systemic, neuraxial, or intracavitary opioids. A less restrictive practice is opioid-sparing anesthesia (OSA), where small amounts of opioids are used. Patients suffering from chronic postsurgical pain, complex regional pain syndrome, cancer-related pain, and other opioid-tolerant patients may also benefit from OFA and OSA approaches.

OFA involves multimodal non-opioid analgesia, which uses sympatholytic drugs and non-opioid analgesics. These drugs can reduce or avoid the use of opioids in the postoperative period. A non-opioid multimodal analgesic method is intended at enhancing adjunctive options that is applying anesthetic techniques aiming different neuro-anatomical circuits and several neurophysiological mechanisms. Non-opioid analgesics include: alpha-2agonists (clonidine and dexmedetomidine), beta-blockers (esmolol), gabapentinoids (gabapentinand pregabalin), lidocaine (lidocaine hydrochloride), magnesium (magnesium sulfate), ketamine and dexamethasone. These drugs when used in combination acts synergistically and change the pathophysiology of nociception thus causes effective analgesia with minimal side effects.

OFA is an efficacious mode of anaesthetic for general surgical procedures when compared to conventional opioid-based anaesthesia (OA). However, the evidence on OFA is still debatable. Therefore there is still a feasibility issue of OFA for common general surgical procedures, which needed to be established.

The quality of recovery after anaesthesia and surgery does not only include pain control but it also involves patient's overall generalised health status in the postoperative period including return of self-care, household and work activities, and mobility compared to preoperative period. Patient-reported outcome measures (PROMs) are considered as the benchmark tools for measuring global health state and post-surgical recovery after any procedure. The QoR-15 is a validated PROM, which is derived from QoR-40 and provides an effective assessment of post-operative recovery. It consists of a total of 15-items, grading each recovery item on a 10 - point numerical Likert scale with total QoR-15 score ranging from 0 (extremely poor recovery)to 150 (excellent recovery).

Aim:

The aim of our study is to explore and compare the effects of OFA using dexmedetomidine vs conventional OA on the quality of recovery and perioperative clinical outcomes for all the patients undergoing laparoscopic cholecystectomies, which is one of the most common abdominal general surgical procedures. The hypothesis is that the patients receiving OFA using dexmedetomidine will have better quality of recovery and perioperative outcomes than patients receiving standard OA.

Methods:

This is a prospective, randomized, parallel-group, double-blinded clinical trial that will commence from February 2024 and the recruitment time will be for three to six months at department of Anaesthesia, Dow university hospital (DUH), Dow International medical college (DIMC), Dow university of health sciences (DUHS). The study will be approved by the DUHS institutional review board (IRB). The participants of the study will be invited once they receive full trial information from the surgeons or the anaesthetists during their pre-assessment visits. The study participants will join only for up to one day after the surgery (Post-operative day-1).

Intervention:

Before the study commences the participants will be taught to measure their pain status via visual analog scale (VAS; where 0 cm = no pain and 10 cm = worst pain), with 'sad' or 'happy' pictures at each end. The participants will be advised to ask for analgesia proactively, once the VAS pain score is >4. All the eligible patients will undergo general anaesthesia for their elective surgeries. In the operating theatre the standard of monitoring will include body temperature, ECG, non-invasive blood pressure, pulse oximetry, neuromuscular monitoring using train-of-four (TOF) stimulation and bispectral index (BIS) for measuring the depth of anaesthesia.

The induction and maintenance of anaesthesia for both OFA vs OA treatment groups will be administered. Once the surgery is completed and after extubation and emergence from anaesthesia, all the participants will be transferred to PACU from where they will be in turn discharged to the ward once they will fulfil the recovery discharge criteria. A multi-modal analgesia regimen along with a prophylactic antiemetic medication is prescribed postoperatively in the ward according to the standard protocol of the department.

For each participant, the mean and total QoR-15 scores will be computed pre-operatively (at baseline) and at24 h (+/- 2 hours) post-operatively. The mean change of QoR-15 scores will be evaluated to establish the difference between the baseline and post-operative day-1 scores. In addition to that the secondary perioperative clinical outcomes will also be recorded in PACU and at 24 hrs postoperatively.

Randomisation:

The participants will be randomized in a 1:1 ratio, using computer-generated random numbers to receive either a standard opioid-based (OA) or opioid-free anaesthesia (OFA) treatment protocols. After obtaining consent, the participants will be assigned a study identification number (ID).

Blinding:

Just before surgery, a concealed envelope containing the study ID will be opened by the anaesthetist, which contains the random allocation of OA or OFA treatment protocols. The participants will be blinded with the treatment groups during the whole study period. The staff members including the recovery and ward nurses providing postoperative care and assessing outcomes in the PACU and the ward will also be kept blinded of the study groups. The anaesthetist administering general anaesthesia could not be blinded due to pragmatic reasons but will not contribute to the care or outcomes assessments during the post-operative period.

Sample size:

According to a previous study the mean QoR-15 score was 106.05 with a standard deviation of 15.73 at 24 hrs post-surgery. An absolute mean change of ≥12 QoR-15 score is deemed clinically significant improvement. An estimated sample size of 27 participants in each group is required to achieve a power of 80% with type-1error of 0.05. A maximum of 10 % increase in the number of participants will be added to compensate the loss of the participants due to cancellations or follow-up losses. Therefore, the total sample size will include 60 participants (n=30 OFA and n=30 OA).

Statistical Analysis:

All participants randomized will be incorporated in the analyses on an intention-to-treat basis. The Kolmogorov-Smirnov test will be used to assess the distribution of the quantitative variables. For continuous data: mean ± standard deviation, median (IQR), and for categorical data: frequencies or percentages will be measured. Mean and total QoR-15 scores will be calculated for each participant at baseline and on postoperative day-1. To find out the difference between postoperative day-1 and baseline score, a change of QoR-15 change scores will be documented. Quantitative variables will be analysed using an Independent-sample t-test or Mann-Whitney U-test and Chi-square or Fisher's exact test will be applied to investigate the qualitative variables.

To adjust for the effect of baseline preoperative scores, ANCOVA (Analysis of Covariance) will be used to study the relationship between QOR-15 and one or more independent variables. A two tailed p value of <0.05 will be considered significant. All statistical analysis will be performed using Stata/IC for Mac Version 16.1 (StataCorp, College Station, TX, USA).