What are the safety and efficacy outcomes of dexmedetomidine compared to propofol for conscious sedation for arthroscopic shoulder surgery under interscalene block in beach chair position?

Study setting The study will be set in the Teaching Hospital Anuradhapura, Sri Lanka. Surgical operations theatre.

Randomization A computer-generated randomization list was created through Microsoft Excel 2019 with 1:1 allocation in to 2 arms (Dexmedetomidine and Propofol arm) using block sizes 2 and 4 by an independent doctor who marked the questionnaire Dexmedetomidine or Propofol and put into the corresponding numbered sealed envelope. Allocation sequence was concealed from the investigator. All consenting patients are numbered consecutively and assigned the matching envelope

Arm 1 Propofol group- received Intravenous Propofol infusion through a cannula inserted to the non-operating hand. It is started after successful interscalene block and is continued till wound closure. Infusion is started at 1- 4 mg/kg/hour titrated to achieve a Modified Observer Assessment of Alertness/Sedation score of 3 or 4 (the MOAA/S ranges from 0 to 5, with a score of 5 defined as awake or minimally sedated, and a score of 0 defined as general anaesthesia with 4 being lethargic response to name spoken and 3 - responds after name called loudly/repeatedly).

Arm 2 Dexmedetomidine group- received intravenous Dexmedetomidine infusion through a cannula inserted to the non-operating hand, which started after successful interscalene block and is continued till wound closure. Started at 1 micrograms/kg loading dose over 10 minutes, followed by an infusion of 0.2- 0.7 micrograms /kg/hour titrated to achieve a Modified Observer Assessment of Alertness/Sedation score (MOAA/S) of 3 or 4 (the MOAA/S ranges from 0 to 5, with a score of 5 defined as awake or minimally sedated, and a score of 0 defined as general anaesthesia with 4 being lethargic response to name spoken and 3 - responds after name called loudly/repeatedly).

Standard care available to both groups

Patients were subjected to fasting according to guidelines as per general anaesthesia (fasting for solids and semisolids for 6 hours prior to surgery, fasting for clear fluids for 2 hours prior to surgery). On arrival to the operation theatre, standard monitoring, including, electrocardiography (ECG), non-invasive blood pressure (NIBP), and pulse oximetry were applied and baseline mean arterial pressure (MAP), heart rate (HR), peripheral oxygen saturation (SpO2), Respiratory rate (RR) and diaphragmatic excursion measured by ultrasound scan (Diaphragm excursion was measured using a phased array probe, with the probe positioned in the subcostal margin in the mid-clavicular line, with the aim of imaging the posterior third of the diaphragm and with the use of M-mode, accurate measurement of diaphragmatic displacement over a respiratory cycle was recorded). The interscalene block (ISB) was performed by the investigators themselves who are experienced with attending regional nerve block workshops and performing more than 100 interscalene brachial plexus blocks. All nerve blocks were performed adhering to the standard guidelines and following the universal precautions. Following successful block patients were subjected to full standard monitoring during surgery. Patient’s vitals (Respiratory rate-RR, Heart rate-HR, Systolic blood pressure-SBP, Mean arterial blood pressure-MAP) were monitored every 15 minutes by the anaesthetist taking care of the patient. Patients were monitored for hypotension (MAP decrease by 20% from baseline) or bradycardia (HR decrease by 20% from baseline). If severe symptomatic hypotension is found intraoperatively, it is treated with 5 to 10 mg IV ephedrine or fluid bolus (30ml/Kg 0.9% saline) and severe bradycardia with 0.5 mg IV atropine. Patients are observed for apnoea and need for airway maneuvers (chin lift, jaw thrust and head extension) and the need for oropharyngeal/ nasopharyngeal airway insertions. The acute complications that are looked for are, signs of local anaesthetic systemic toxicity (LAST), accidental vascular puncture during procedure, accidental intravascular injection of anaesthetic solution, pneumothorax (detected by a post-operative ultrasound scan of chest with absent lung sliding, absence of comet tail and Barcode sign in the M mode), phrenic nerve paralysis (ultrasound appearance of paradoxical movement, through diaphragmatic excursion of less than 4 mm, and a difference >50% between the excursion of one hemidiaphragm compared to the other), hoarseness (due to recurrent laryngeal nerve involvement), post-operative nausea and vomiting (PONV) and any other complications (e.g. Horner’s syndrome). Patients are asked about the discomfort or pain felt during the block procedure and the during the surgery via a visual analogue scale (VAS) (0 to 10 with 0= no pain/discomfort and 10=severe pain). Following surgery, patient is taken to the Post anaesthesia care unit (PACU) where according to the modified Aldrete scoring system; a score of >9 permits Phase I discharge from the PACU to ward. The time spent in the PACU is documented by nursing officer blinded to the sedation used. Patients are followed up during their hospital stay by a trained pain management nursing officer blinded to the sedation used, to determine the duration of post-block analgesia time which is defined as the duration from block onset time to when they first registered pain. During the hospital stay, the patient’s post-operative pain will be assessed using a Visual analog scale (VAS- 0- no pain and 10- severe pain) and the type of analgesia used (opioid- Subcutaneous Morphine, non-opioid- paracetamol, diclofenac sodium) and the amounts (mg) used if opioids are used at post-op 1, 6, 12 and 24 hours. They are also observed for adverse side effects of opioid use (nausea, vomiting, constipation). All patients who receive Inter scalnae block (ISB) for anesthesia are followed up for four weeks, weekly, then monthly up to 3 months for potential neurologic complications and to assess the patients’ satisfaction towards the supraclavicular nerve block via a telephone interview by the trained pain management nurse. To detect potential neurological complications, patients are asked a standardized set of questions in relation to the operative limb; do you have any numbness? Do you have any tingling? Do you have any abnormal sensations? Do you have any pain? Do you have any weakness? If the patient complains of any neurological complications, then further queries are to be made taking into account the anatomy relevant to the surgery and the peripheral nerve/plexus block. Symptoms that are immediately adjacent to the wound, consistent with normal tissue healing or the initial trauma are not considered relevant in terms of ISB being a causal factor. For patients with ambiguous symptoms or complaints, repeat contact is made with the patient in another 2 weeks. Triggers for referral to a neurologist are, new onset of motor and/or sensory deficit, non-resolving paraesthesia, pain and allodynia, or dysesthesia. If such neurological referral is done the patient is followed up for their neurological diagnosis/findings.

Blinding Patients are blinded to the sedative used. Investigators are blinded to sedative use as after block placement the anaesthetist looking after the patient collects the data. Anaesthetist who is observing the patient is not blinded as propofol has a distinctive white colour and will collect the intraoperative data . Post anaesthesia care unit nurse is blinded to sedative use. Pain assessment nurse was blinded to group allocation

All consenting patients males and females, with the American Society Anaesthesiologist (ASA) physical status of I or II awaiting arthroscopic shoulder surgery under regional anaesthesia in beach chair position at Teaching Hospital Anuradhapura. Minimum age of patients is 18 years with a maximum of 80 years.

• Patients with significant coagulopathy: Patients with a platelet count of less than 100,000, an international normalizing ratio(INR) more than 1.5 and patients on anticoagulants such as warfarin, heparin and clopidogrel.

• Infection at the injection site • Known allergy to local anaesthetics and sedatives (Propofol & Dexmedomidine) • Inability to cooperate during block placement or surgery • A body mass index more than 35 Kg/m2 • Pre-existing loss of force or sensation in the operative limb • Significant organ dysfunction (cardiac- patients with heart block, bradycardia, severe ventricular dysfunction, hypovolaemia, or chronic uncontrolled hypertension, pulmonary, renal, hepatic impairment and uncontrolled diabetes mellitus) • Failed interscalene block during the present intervention and converted to general anaesthesia.