“Preoperative oral duloxetine: does it affect duration of spinal anesthesia and early postoperative pain after arthroscopic ACL repair?” A prospective, randomized, double-blind controlled trial

Study design and ethics

A parallel-group, prospective, randomized, nonfunded, and single-institute study was conducted after obtaining approval from Ethics committee and registration at ClinicalTrials.gov according to the Consolidated Standards of Reporting Trials (CONSORT) guidelines. Written informed consent was signed by all participants.

Study setting, patients’ recruitment, randomization, and control of potential bias

Study settings:

Recruitment between March 2021 and July 2021.

A computer-generated codes placed in opaque sealed envelopes with a 1:1 allocation ratio by an anesthesiologist not directly involved in the trial or patient care.

Follow-up was done by a researcher unaware of the group allocation. So, the patient, anesthesiologist, and follow-up researcher were blinded to group allocation.

Study population

Seventy patients (ASA-PS class I and II, both sexes, 18 to 50 years old, 60–80 kg weight, 155–180cm height) undergoing arthroscopic ACL repair under spinal anesthesia were included in the study.

Patients who declined to sign written informed consent; patients with a history of allergy to duloxetine, patients on sedatives or opioid drugs, patients with alcohol or drug addiction, patients with an inability to communicate to evaluate the postoperative pain, patients with a need for postoperative ICU hospitalization, patients with a history of taking duloxetine or any SSRIs, patients with contraindications for spinal anesthesia, and patients with psychiatric illness (tricyclic or MAOIs) or hepatic or renal failure were excluded.

Study groups

Patients undergoing arthroscopic ACL repair under spinal anesthesia were randomly assigned into one of the following groups:

Group D (duloxetine group): Two hours before the operation, duloxetine patients received 60mg of duloxetine tablets orally in the ward and then transferred to OR to receive spinal anesthesia before surgery.

Group C (control group): The patients received placebo tablets in the ward and then transferred to OR to receive spinal anesthesia before surgery.

Anesthesia

All patients were clinically assessed, and routine preoperative investigations were done, including CBC, coagulation profile, liver function tests, kidney function tests, fasting blood sugar, and ECG.

Intraoperative setting

Standard monitoring (ECG, pulse oximetry, and NIBP) were connected to all patients in the operating room, and baseline vital data (HR, SpO2, systolic, diastolic, and mean arterial blood pressure) were recorded, and subsequently, every 5 min, an intravenous (IV) line was inserted.

For both groups, after administration of 6 mL/kg intravenous crystalloid, and under complete aseptic conditions, Tuffier’s (intercristal) line as L4–L5 level was defined, 5ml of 2% lidocaine infiltrated at L3–L4 midline level as local anesthesia in the sitting position, through 25 Gauge Quincke spinal needle 3.5 mL of 0.5% hyperbaric bupivacaine intrathecally injected, then patients positioned supine for 20 min. Patients were operated on by the same team and techniques. When systolic blood pressure decreased more than 30% or mean arterial blood pressure below 60 mmHg, intravenous 3mg incremental ephedrine was given, whereas intravenous 0.5mg atropine was given when HR was below 50bpm.

Pinprick test was used to assess sensory block every 1 min till peak sensory level, then every 5 min for the next 30 min after that assessments were performed by the surgeon every 15 min intraoperatively, and a trained nurse continued the assessment during the postoperative period till regression to the L2 segment level, with recording the time to T10 sensory level as the onset of sensory block, time to peak sensory level.

Two-dermatome regression from the peak sensory level defined the sensory recovery time.

The motor block was assessed by a modified Bromage scale (grade 3 no movement, grade 2 unable to flex knees, can flex ankle, grade 1 unable to raise an extended leg but able to move the knees and ankles, grade 0 no paralysis) (Bromage et al., 1964), time to Bromage 1 defined as the onset of motor block whereas return to Bromage 2 defined motor recovery and motor block duration.

Patients were taught before the surgery to scale their pain by visual analog scale (VAS score) where 0 = no pain and 10 = worst possible pain every 4 h for the first 24 h after the operation.

Regular intravenous paracetamol, 1 g every 8 h, and ondansetron 4mg (at the end of surgery) were given (Hetta et al., 2020) to all patients, where postoperative rescue analgesics were given by hospital nursing staff to VAS score of ≥ 4 in the form of intravenous 3mg morphine and not repeated within 4 h limited to 12 mg morphine per 24 h after operation (Hetta et al., 2020; Stanley et al., 1996); the first rescue analgesic need, frequency, and total morphine consumption timing were recorded. Adverse effects were recorded as HR less than 50 bpm (intravenous 0.5mg atropine was given), arrhythmia, systolic blood pressure less than 90 mmHg (20ml/kg ringer was infused), dry mouth, PONV (ondansetron 4mg), and seizures.

Outcome measurements

Primary outcome:

Our primary outcome is to assess the onset of spinal anesthesia.

Secondary outcome:

Duration of spinal anesthesia (two-dermatome regression for sensory recovery and return to Bromage 2 for motor recovery).

Visual analog scale (VAS score) where 0= no pain and 10= worst possible pain every 4 h for the first 24 h after the operation.

Time for first postoperative rescue analgesia request, frequency, and total morphine consumption.

Sample size calculation

Using G power software for sample size calculation, setting power at 90% and alpha error at 0.05, and assuming a large effect size difference between study groups regarding the time of spinal anesthesia (D=0.8), a sample size of 35 patients per group will be needed (total 70 patients).

Data management and analysis

The statistical analysis was performed using a standard SPSS software package version 23 (Chicago, IL). Normally distributed numerical data are presented as mean ± SD and differences between groups were compared using the independent Student’s t-test; data not normally distributed were compared using the Mann-Whitney test and are presented as median (IQR) and categorical variables were analyzed using the χ2 test or Fisher’s exact test and are presented as number (%). All P values are two-sided. P <0.05 is considered statistically significant.

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