الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Thyroid surgery is a common and painful surgery that requires analgesia. Although it is done through a relatively small incision, thyroidectomy elicits pain through multiple mechanisms, which delays early discharge from hospital and places a significant burden on both the patient and the healthcare team.
High-quality pain management after thyroid surgery remains major challenge. Although opioids still to play an important role in management of postoperative pain, they have many adverse effects. Multimodal approaches have been proposed to improve postoperative pain management and to decrease the opioid-related adverse effects.
The term “preemptive analgesia” proposes that an antinociceptive intervention, performed preoperatively, could prevent or alleviate postoperative pain, because of its capacity to block the central sensitization, so most likely lowering postoperative analgesic requirements and their related adverse reactions, and thus promoting their safety and efficacy.
CPB has been applied in different head and neck procedures to provide sufficient analgesia. Since 2004, when intermediate CPB was suggested beside superficial and deep CPBs, some argument in nomenclature and definitions of CPBs has been found, especially for the intermediate. In addition, the expanded role of US in the head and neck regional anaesthesia, allows CPB to be carried out more accurately and safely under US guidance.
Dexmedetomidine is a highly selective agonist for the α2 adrenergic receptors. It acts mainly in the locus coeruleus in the brainstem. When used as a sedative for patients, it has served as a central anti-sympathetic, and it may maintain physiological sleep better than other sedatives while also producing analgesic and anxiolytic impacts. It is a new adjunct for regional anaesthesia providing more prolonged duration of anaesthesia and analgesia.
Aim of the present work was to evaluate the effect of adding dexmedetomidine to bupivacaine in superficial and US-guided intermediate CPB for patients undergoing total thyroidectomy under general anaesthesia.
After approval of local ethics committee and obtaining a written informed consent from each patient, the current study was carried out in Alexandria Main University Hospital on 50 ASA I or II patients aged between 20-60 years old, of either sex, scheduled for elective total thyroidectomy for benign lesions.
Using sealed envelope technique, patients were divided at random into two equal groups, with 25 patients for each group:
1. group I: Cervical plexus block was conducted with 20 ml of bupivacaine 0.25% + 0.5 ml (50 μg) dexmedetomidine for each side.
2. group II: Cervical plexus block was conducted with 20 ml of bupivacaine 0.25% + 0.5 ml normal saline for each side.
Evaluation of patients was performed through proper history taking, clinical examination and all needed lab investigations ( including a CBC and a coagulation profile).
All patients were fasting for 8 hours before surgery. On arrival to the operative theater, a peripheral cannula (20G) was inserted. Standard monitoring was established using a multichannel monitor (Drager Infinity vista XL) connected to the patient to show continuous lead II ECG monitoring for heart rate (beats/min) and rhythm, noninvasive arterial blood pressure (NIBP), peripheral arterial oxygen saturation (SpO2). Premedication was done using 0.05 mg/kg midazolam IV. Induction of general anaesthesia was carried out in the two groups as following: Patients were positioned supine and pre-oxygenated with 100% oxygen by a face-mask for three minutes, induction of anaesthesia was done with intravenous fentanyl 2.0 mcg/kg, propofol 2 mg /kg injected slowly till loss of verbal communication and atracurium 0.5 mg/kg for endotracheal intubation. Anaesthesia was maintained with 1.2% isoflurane in 100% oxygen and intermittent boluses of atracurium 0.1 mg/kg guided by nerve stimulator.
While the patient is in supine position and the head turned to either side, Us-guided intermediate CPB was done bilaterally under complete aseptic technique, followed by block to the superficial cervical plexus.
At the end of surgery, isoflurane was discontinued; neuromuscular blockade was countered by injection of neostigmine 0.04 mg/kg with atropine 0.01 mg/kg. Trachea was extubated and the patient was transferred to the post-anaesthesia care unit (PACU) where HR, oxygen saturation (SpO2) and arterial blood pressure (MAP) were measured. Paracetamol 15 mg/kg every 6 hours and ketorolac 30 mg every 12h were given to both groups. Rescue analgesia (nalbuphine) was given in incremental doses of 0.15 mg/kg if VAS is > 3 till pain is relieved.
Measurements
A. Demographic data
B. Duration of surgery (in minutes)
C. Haemodynamic parameters: Continuous monitoring of heart rate and rhythm, mean arterial blood pressure and oxygen saturation by multichannel monitor.
All previous parameters were recorded preoperative, intraoperative (after induction and every 15min) and postoperatively (every 15min for 1 hour then every 4h for the next 24 hours).
D. Visual analogue scale
• Pain was assessed by direct marking on the visual analogue scale (VAS).
• It was measured postoperatively at PACU admission and every 4 hours for the next 24 hours.
• Rescue analgesia was given in the form of IV nalbuphine (0.15 mg/kg) when VAS score was > 3 at any time postoperatively during the first 24 hours with a maximum single dose of 20 mg and the following was measured:
Time of first analgesic requirement (hours).
The total postoperative analgesic consumption in the first 24 hours postoperative (milligrams).
E. Postoperative complications
Any postoperative related complication occurring at any time during the study period was spotted, recorded and treated accordingly.
F. Assessment of Post Anaesthesia Recovery (PAR)
Using Modified Aldrete Score (MAS) at 0 min., then every minute for the next five minutes and then at a 5-minutes interval till a median score of 9 or more is achieved as standard of recovery from anaesthesia and discharge from PACU.
The results of the current study show that, comparing the two groups, there was an insignificant difference in age, weight, sex and ASA classification as well as preoperative HR and MAP. While the heart rate of both groups showed significant decrease after induction and throughout all intraoperative and most postoperative times, there was significant difference between both groups as group I showed lower readings than group II. At the same time, there was significant decrease in MAP of both groups throughout all intraoperative and most postoperative times of measurements with no significant difference between the two groups. VAS score was significantly lower in group I compared to group II up to 24 hours postoperatively. Time to first rescue analgesia was significantly shorter and 24 h nalbuphine consumption was significantly higher in group II compared to dexmedetomidine group. There was no significant difference regarding the incidence of complications such as postoperative nausea and vomiting, nerve injury and hematoma at the injection site. The results of present study not only reported better analgesia, longer time to first rescue analgesia, less postoperative nalbuphine consumption in dexmedetomidine group, but also supported higher modified Aldrete score (MAS) and earlier recovery in that group