Does Saline Injection Around Phrenic Nerve Reduce Incidence of Diaphragmatic Paresis Following Interscalene Block?

Patients will be randomised to either group S (saline group) or group C (conventional group) by computer generated random numbers and allocation will be enclosed in sealed envelope. Anaesthetist performing and/or supervising the block will be the only personnel who will be aware of the randomisation. Patients will be blinded to the study group. Intraoperative management of the case will be done by an anaesthetist blinded to the study group. Outcome measurements will be recorded by study observers blinded to the group allocation.

ISB protocol Following written informed consent, the patient will have routine monitors attached (ECG, Pulse oximeter and non-invasive blood pressure). Intravenous access will be secured and patients will be placed in 45 degree head-up position for the block with head turned to the non-operative side. Intravenous sedation with Midazolam (2 mg) and fentanyl (50 to 100 microgram) will be administered to all patients prior to the block. The ultrasound machine will be positioned on the side opposite to the block. Skin will be prepped with 2% Chlorhexidine (Chloraprep) following which the block will be performed under strict aseptic precautions with the anesthetist wearing a mask and sterile gloves. The high frequency linear probe (sonosite) will be aligned transversely across the neck at the interscalene level to identify C5 and C6 nerve roots. 2% lidocaine will be used for skin infiltration and "stop before block" performed prior to insertion of block needle. In plane posterior approach will be used with a 50 mm short bevel block needle (Braun) advanced through middle scalene muscle. Following this, the technique differs between the two groups.

In group C, the needle tip will then be positioned between C5 and C6 nerve roots. At this location, 15 ml of 0.25% levobupivacaine will be injected in 5 ml increments with intermittent aspiration. The needle tip will not be repositioned unless the patient complaints of paraesthesia.

In group S, at the same level chosen for interscalene block, needle tip will be positioned anterior to anterior scalene muscle. At this location 10 ml 0.9% saline will be injected. This will then be followed by repositioning of needle between roots of C5 and C6 where 15 ml of 0.25% levobupivacaine will be injected in 5 ml increments with intermittent aspiration. The needle tip will not be repositioned unless the patient complaints of paraesthesia.

Intra-operative procedure

Following performance of the block, all patients will receive protocolised general anaesthetic. Anaesthesia will be induced with 2-3 mg per kg of propofol, followed by rocuronium 0.6mg/kg for muscle relaxation. Anaesthesia will be maintained with inhaled sevoflurane (MAC 1 end tidal concentration) along with air and oxygen mixture to deliver an inspired oxygen concentration of 40%. Antibiotics will be given as per hospital protocol prior to incision. In the absence of contraindications, all patients will receive intravenous paracetamol 1g and parecoxib 40 mg as a part of multimodal analgesia regimen. All patients will also receive intravenous dexamethasone 8 mg and ondansetron 4mg for post-operative nausea and vomiting prophylaxis. Further doses of fentanyl in 25 microgram increments will be administered by the anaesthetist if the heart rate increases by more than 15% of baseline values obtained prior to induction. Patients will be reversed by suggamadex. If at least two twitches are present during TOF measurement 2 mg/kg dose will be administered. If less than 2 twitches are present, 4 mg/kg dose will be administered.

Post-operative procedure:

Following transfer to recovery unit, if patient reported pain score by numerical rating score was >3, morphine 2 mg increments will be given intravenously by the recovery staff. This will be repeated every 5 minutes till the pain score is \<4. In patients needing more than 10 mg of morphine in the recovery, anaesthetist will be requested to review the patient. Post-operatively, in the absence of contraindications, all patients will be prescribed regular paracetamol 1g, 6 hourly and celecoxib 200 mg, 12 hourly. For breakthrough pain, oxynorm 10 mg as needed once every 4 hours will be prescribed. Anti-emetics (ondansetron 4 mg, 8 hourly and Cyclizine 50 mg, 8 hourly) will be prescribed for all patients to be administered as required. Patient will also be asked about presence or absence of subjective feeling of dypnoea and report satisfaction of overall anaesthetic management (numerical rating scale 0-10) prior to discharge from recovery.

Diaphragm palsy and PFT assessment Diaphragm assessment and bed side spirometry will be done at two time points. First measurement (time point 1) will be done at the baseline as soon as the patient arrives in the induction room. This will be done prior to administration of any sedative agents or regional block. Second assessment (time point 2) will be done post-operatively once the patients are deemed to be ready for discharge from recovery back to the ward.

For diaphragmatic paresis assessment, patients will be placed in supine position and curvilinear ultrasound probe (2-5 MHz) will be used. Diaphragm will be identified as hyperechoic line by subcostal approach using liver and spleen as acoustic windows. Patients will be requested to take deep breaths and M mode will be used to measure the excursion of diaphragm. Diaphragmatic paresis will be documented when there is more than 75% reduction in the excursion compared to baseline or if there was paradoxical movement of the diapragm. Bedside assessment will be done by radiologist blinded to the study group.

Bedside spirometry assessments will be done with patients sitting up. They will be requested to make maximum inspiratory effort and blow as hard and fast in to the device. Best reading from three repeated measurements will be recorded.