Effect OF Bilateral Superficial Cervical Plexus Block On Postoperative Analgesic Consumption In Patients Undergoing Thyroid Surgery: A Double Blind Randomized Control Study

INTRODUCTION: The thyroid gland surgery is a common painful procedure requiring analgesia. Pain after thyroid surgery is considered of moderate intensity and duration which has been traditionally managed with NSAIDs, and occasionally with opioids. However, recently nerve blocks have become popular as part of multimodal analgesic regimens in thyroid surgery patients. Superficial cervical plexus is a sensory neural plexus formed from the ventral rami of the first four cervical nerves (C1-C4). Two nerve loops, which are formed by the union of the adjacent anterior spinal nerves from C2 to C4, give off four superficial sensory branches, listed in cranio-caudal order as follows: lesser occipital (C2, C3), great auricular (C2, C3), transverse cervical (C2, C3), and supraclavicular nerves (C3, C4). These nerve roots provide sensation to the skin, and superficial structures of the ear auricle, acromioclavicular joint, clavicle and anterolateral neck. It emerges behind the posterior border of sternomastoid muscle. The cervical plexus also includes deep branches to the neck muscles and the phrenic nerve (C3,C4, and C5) in addition to communicating branches to the superior cervical sympathetic ganglion, hypoglossal, and spinal accessory nerves. Regional techniques are applied for anterior neck surgeries mostly in relation to the involved cervical fascia. A subcutaneous infiltration of LA under the skin superficial to the investing fascia is called superficial block. Injection deep into the investing fascia is the intermediate cervical block. In the intermediate block,  the injection is between the superficial and deep (prevertebral) fascia while the deep block is under the deep cervical fascia. Bilateral deep cervical plexus block (PB) carries the risk of phrenic nerve block causing diaphragm paralysis. Regional nerve blockade has been reported to decrease mechanical hyperalgesia caused by inflammation. Superficial cervical plexus block (SCPB can be employed as a component of multimodal analgesia following thyroid surgery. SCPB consists of a bilateral injection of local anaesthetic behind the lateral border of the sternocleidomastoid muscle, which induces surface anaesthesia to the neck. A two- or three-point injection technique can be adopted. Unlike the two-point technique, the three-point technique supplies blockade of the transverse cervical branches of the plexus. The complications of SCPB include hoarseness, hematoma, and local anaesthetic toxicity. Bilateral superficial cervical plexus block (BSCPB) provides an adjuvant technique as a part of multimodal analgesia thus reducing the requirement of postoperative analgesics.

AIM

To assess the analgesic efficacy of bilateral superficial plexus block for thyroid surgery under general anaesthesia using bilateral superficial cervical plexus block.

OBJECTIVE

1. To observe the pattern of immediate postoperative pain and analgesic consumption.

2. To assess analgesic effect of bilateral superficial plexus block for thyroid surgery

MATERIAL & METHODS

Study Setting

Operation theatre of a tertiary care hospital in India.

Study Population :All adult (18 - 65 yrs) ASA I - III patients who are undergoing thyroidectomy in a tertiary care hospital.

Study design: A Double Blind Randomized Control Study

Sample size

The minimum required sample is 18 in each group.

Hence we would study 30 in each group (n=60).

Inclusion Criteria

1. Age: Between 18 to 65 years.

2. ASA status: I - III

3. Patients undergoing Thyroid surgery.

Exclusion Criteria

1. Patient’s refusal to give consent, unwilling to participate in the study

2. Allergy to local anaesthetics

3. Retro-sternal goitre

4. Altered anatomical landmarks

5. Other contra-indications to peripheral neural blockade (eg. Coagulation abnormalities)

Study Methodology

Study will commence post approval of Institutional Ethical Committee. All patients scheduled for elective thyroidectomy will be enrolled in the study. Cases will be randomized according to a computer generated randomization chart. Based on serial number of the cases, patients will be assigned to one of the two treatment groups i.e. group B receiving Bilateral SCPB(BSCPB) and group C receiving traditional analgesia. A thorough preoperative evaluation will be performed. The patient will be subiected to a complete general and systemic examination and will be investigated as follows: complete blood picture, bleeding time, clotting time, chest X-ray, ECG, RFT, random blood sugar level and ultrasonography/CT neck. Identified eligible patients will be informed about the nature of study and procedure, and informed written consent will be taken. On the day of surgery, fasting status of the patient will be confirmed. Once wheeled into the OR, the patient will be connected to ASA standard monitoring, and baseline vital parameters will be noted. An intravenous access will be secured in non-dominant hand. Intravenous ringer lactate will be started as per fluid requirement calculated using institutional practice. Patient will be premedicated with Inj Midazolam 0.05 - 0.15 mg/kg and Inj Fentanyl 2 mcg/Kg. Patient will be induced with Inj Propofol in doses titrated to effect. Post confirmation of adequate bag and mask ventilation, Inj Atracurium 0.5-0.6 mg/kg will be administered and preoxygenated with oxygen at 5 litre per minute for 3 minutes. After preoxygenation, patient will be intubated with appropriate size ET Tube and connected to ventilator and depth of anaesthesia shall be maintained with Sevoflurane with minimum alveolar concentration (MAC) of 0.8 to 1.0, with end tidal CO2 of 35-40 mm Hg, with Inj Atracurium 0.1mg/kg being be administered on noticing spontaneous breath efforts. Following this, the patients under Group ’B" will receive BSCPB using under mentioned technique. Position: Supine position with the head turned opposite to the side to be blocked Procedure: Part preparation would be done following strict asepsis. Superficial Cervical plexus would be identified using a linear transducer of US probe, which appears as hyperechoic bundle below posterior border of sternocleidomastoid. A hypodermic needle of 26G and 38mm length will be introduced in-plane along the posterior border of the sternocleidomastoid, between sternocleidomastoid muscle and superficial to the investing laver of deep cervical fascia. 5mL of 0.25% Bupivacaine will be administered using hydro-dissection, and spread of drug around the cervical plexus will be visualized as separation of two layers of sternocleidomastoid and investing layer of deep cervical plexus - which would be considered as end point of the block. Same procedure is repeated on the opposite side of neck. A successful block is considered if the drug could be infiltrated on the both sides using designated technique and post-procedure visualisation of drug around cervical plexus is possible. Patients under Group ’C’ and Group ’B’ will receive Intra op Inj Paracetamol 15mg/kg 30mins after skin incision. Post-operatively both will receive Inj Paracetamol 15 mg/kg IV 8th hourly + Inj Diclofenac 50mg IM 12th hourly and Inj Tramadol 50mg IV SOS as rescue analgesia. Patients will be analysed post-op by noting pain based on the 10-point VAS score, Heart Rate and Blood Pressure at PACU when patient starts to fully respond to verbal command and also at 6th hour, 12th hour, and 24th hour postop. VAS score <3 was considered as adequate analgesia. When patient reports pain voluntarily, VAS will be reassessed and if VAS > 3 at any time rescue analgesia with Inj Tramadol 50mg IV will be given and noted along with time in minutes from the end of surgery. Total analgesics consumed in the first 24 hours will be noted. In addition, the incidence of postoperative nausea and vomiting will be documented if reported within 24 hours.