Introduction

Epidural Analgesia is recognized as gold standard in postoperative analgesia. However Erector spinae block is a relatively new Truncal Fascial plane block, with its mechanism of action near neuraxial axis, hence offering potentially similar potent analgesia as epidural block.  We hypothesized that that analgesia offered by a catheter based continuous Erector spinae block  will have an equivalent effect as catheter based continuous epidural analgesia.

Thus, we designed this study to test the above hypothesis.

Research design:

Randomized, open label, non-inferiority trial.

Aims and objective:

Primary objective: Comparisons between the total fentanyl consumption via IVPCA as rescue analgesic in 48 hr. period post Renal transplant surgery in recipients receiving postoperative analgesia via erector spinae plane catheter vs epidural catheter.

Secondary objectives:

·       Static and Dynamic pain assessment using the NRS of 0 to 10 at 30 min., 2, 24- and 48-hours’ time point.

·       Recipient satisfaction with analgesia.

·       Amount of Noradrenaline consumed during surgery.

·       Time for ambulation.

·       Incidence of PONV.

METHODOLGY

After approval from IEC and CTRI and getting written and informed consent from all the patients prior to enrollment, a randomized, open label, non-inferiority trial would be conducted.

Inclusion criteria: Renal transplant Recipients (18-60 years) of American Society of Anaesthesiology (ASA) physical status of III of either sex, planned for renal transplant surgery under general anaesthesia will be included in the study.

Exclusion criteria: Patient’s refusal, difficult sonoanatomy, BMI greater than 25, allergy, heart failure, ejection fraction less than 50%, RV/LV dysfunction, coagulation abnormalities, anticoagulant drugs intake, inability to understand the working of Patient Controlled Analgesia pump and NRS pain scale will be excluded.

 Group allocation and study intervention

Preoperatively, a night before surgery all recipients and caretakers will be acquainted with the NRS scale of pain. They will be informed regarding options of rescue analgesia available to them in case they feel pain in spite of block. They will be explained the dosage protocol of the rescue analgesic.  Patient monitoring will include a lead II/V5 electrocardiogram, heart rate, pulse oximetry, Bi-spectral index monitoring, core temperature monitoring along with invasive blood pressure and CVP monitoring.

All patients will be anaesthetized following similar anaesthetic management. Induction will be done with Propofol(2mg/kg), fentanyl (2mcg/kg), and muscle relaxation with Atracurium (0.5mg/kg). Muscle relaxation will be maintained with atracurium 10 mg boluses as and when required. Anaesthesia will be maintained with desflurane, air and oxygen titrated to BIS monitoring (40 to 60). After tracheal intubation, mechanical ventilation will be started with volume- controlled mode and positive end- expiratory pressure (PEEP 5 cm H2O) using a low flow circuit with 40-50% oxygen in air, adjusting the tidal volume (8 ml/kg) and respiratory rate to maintain normocapnia and arterial oxygen saturation >95%. A warming blanket will be used to maintain normothermia. All patients will receive 1-gram paracetamol i.v. before incision.

Group I (Epidural group): Before anaesthesia induction an Epidural catheter will be place at T10 level, under strict aseptic precautions with Recipient in the sitting position. Epidural catheter will be fixed with transparent dressing after negative test dose. After anaesthesia induction, patient will receive 3 mg morphine diluted in 8 ml 0.2% ropivacaine. Patient will receive epidural infusion of Ropivacaine 0.2% (Ropin, Neon Laboratories Ltd., India) at 5 ml per hour till the end of the surgery.

Group II (ES block): After induction before surgery, recipients will be maneuvered to lateral epidural position. Under strict aseptic precautions ultrasound high frequency (Sonosite Edge II, Fujifilm Sonosite Inc., USA) (6-13hz) will be placed in a longitudinal sagittal orientation at T9/T10 vertebra. After identification of spinous process, probe will be gently moved laterally till flat, square acoustic shadows of the transverse processes is seen. Running longitudinally just above the transverse processes erector spinae muscle is identified. Probe is gently rocked till fascial plane just above the transverse process become prominent. After correct TP identification, a 20-gauge 10cm echogenic needle (Contiplex Ultra 360^®, B. Braun Medical Inc., USA) will be inserted using an in-plane, cranial to caudal approach to contact the bony shadow of the TP with the tip deep to the fascial plane of the erector spinae muscle. The correct location of the needle tip will be confirmed by injecting 0.5–1 cc of normal saline 0.9% and observing linear fluid spread lifting the erector spinae muscle off the tip of the TP. Once the fascial plane is recognized, 30 ml of ropivacaine 0.2% (Ropin^®, Neon Laboratories Ltd., India) will be injected and spread of local anesthetic will be visualized. Once the plane is hydro-dissected, 20g catheter will be threaded in the plane with USG guidance for confirmation.  Again, 10ml of saline will be injected to see the injectate spread to confirm the position of catheter. Once satisfactory position is confirmed, needle will be withdrawn and catheter will be fixed via tunneling in skin. The insertion site of catheter will be covered with transparent dressing.

Surgery will be performed in supine position. A perinephric drain will be placed after completion of surgery. Recipients in group 1 (Epidural) will receive epidural block and Recipient in group 2 (ES) will receive ES block.  After completion of procedure, neuromuscular blockade will be adequately reversed and trachea extubated once they start following commands.

Both group patients will receive continuous infusion of 0.1 % Ropivacaine at rate of 6ml/hr. through the catheter till 48 hours post-surgery.  Fentanyl IV PCA will be constituted for all recipients, with zero basal rate and demand doses of 20 mcg Fentanyl with maximum 4 demand doses per hour with Lock out interval of ten minutes.

Post operatively recipients of both the group will receive 1-gram i.v. paracetamol eight hourly for first 24 hours. During next 24 hours they will receive tab paracetamol 500 mg qid per oral.

 Patients who complain of static NRS greater than 8 at 2hr time point will be dropped from analysis and these patients will receive basal infusion rate of 50 mcg/hr. through Fentanyl IV PCA in addition to routine demand doses.

Randomization: All eligible patients will be randomized between the either group using computer generated block randomization method where block size will be 10.

Outcome Assessment:

All outcomes will be assessed by an anaesthesia registrar, blind to the group allocation.

The primary outcome will be Total fentanyl consumption as rescue analgesia in 48-hours period.

The secondary outcomes will be

1. Static and Dynamic pain scores. Comparison of static and dynamic pain scores at 30 mins, 2, 24 and 48 hours post operatively will be done. Pain will be assessed on Numeric Rating Scale (NRS) of 0 to 10 where 0 is no pain and 10 is worst imaginable pain.  The dynamic pain will be the pain, patient choses on NRS scale on flexion of lower limbs.
2. Amount of Noradrenaline consumed during surgery.
3. Recipient satisfaction with analgesia: At the end of 48 hours, recipient will be asked to answer in yes or no whether the pain he/she experienced after surgery was more or less than their preconceived notion.
4.  Time for ambulation: defined as time at which patient gets off the bed

5.     Postoperative nausea and vomiting (PONV). Assessed on a 3-point score.

           i=no nausea vomiting.

           ii= vomiting responding to intravenous 4mg ondansetron.

           iii=vomiting not responding to ondansetron.

Sample size:

Taking a non-inferiority margin of 300 mcg in IV PCA Fentanyl consumption between two study groups where pooled standard deviation was 40 mcg. At minimum one-sided 95% confidence interval (alpha =0.025) and 80% power of the study, estimated sample size was 29 in each of the two groups. After taking drop out in the estimated sample size, finally we have decided to include 35 patients in each of the two groups. Sample size was estimated using software power analysis and sample size version-16 (PASS-16).

Statistical analysis:

Normality of the continuous variables will be assessed. Descriptive statistics of the continuous variables will be presented as mean± standard deviation /median (interquartile range) as appropriate while categorical data in frequency and percentage. Students t test or its non- parametric method to be used to compare the means or medians whereas Chi square test/ Fisher exact test will be used to compare the proportions between two groups. Two-way Repeated measures ANOVA or Liner mixed model to be used to test the association of the interventions (study groups) and change in the Measurements (VAS Score etc.). A p value < 0.025 will be considered statistically significant.