Dexmedetomidine and Fentanyl as Adjuvants to Thoracic Epidural

Following approval from Research Committee of Anesthesia Department and the Ethics Committee of the Faculty of Medicine, Cairo University, 50 patients will be included in the study (25 patients per group). After obtaining written informed consents, all patients will be subjected to systematic preoperative assessment including history taking, physical examination, and review of the results of routine investigations. Upon arrival to the preparation room, a 20G IV cannula will be inserted into a peripheral vein and midazolam 2-3 mg will be administered unless contraindicated. A 20G arterial catheter will be inserted into the radial artery of the dependent (non-operative) side, after local infiltration with lidocaine 2%. Patients will be transferred to the operating room where routine monitoring is applied, including electrocardiography (ECG), invasive Blood Pressure (IBP) and pulse oximetry are attached. Baseline heart rate, blood pressure, oxygen saturation and respiratory rate will be recorded.

A thoracic epidural catheter will be inserted at the T6- T7 intervertebral space, with the patient in the sitting position with standard aseptic precautions using an 18-G Touhy needle via a midline or paramedian approach with a loss of resistance method. A test dose of 3 ml of 2% lignocaine with adrenaline 5 µ/ml will be administered.

For thoracic surgery the sensory dermatome blockade needs to cover the incision and intercostal drains and may extend from T4 to T8.

The epidural drug will be administered according to the group allocation over a period of 10 minutes as follows:

Group A:

Patients will receive 50 μg dexmedetomidine with 10 ml of 0.125% bupivacaine followed by a continuous infusion of (10 ml bupivacaine + 25 μg dexmedetomidine + 39 ml saline with rate of 5 ml per hour).

Group B:

Patients will receive 50 μg fentanyl in addition to 10 ml 0.125% bupivacaine followed by a continuous infusion (10 ml bupivacaine + 100 μg fentanyl + 38 ml saline with rate of 5 ml per hour).

After documenting the sensory blockade by using a piece of ice or cold object, If sensory level fail to be achieved, patient will be out of the study. Anesthesia will be induced with Propofol 2-3 mg/kg, together with fentanyl 2 mg/kg until loss of verbal response. Muscle relaxation will be achieved with atracurium 0.5 mg/kg and the patient's trachea will be intubated using a single or double-lumen tube, as indicated by the surgical procedure. Anesthesia will be maintained by isoflurane, and muscle relaxation will be maintained with atracurium 0.3 - 0.5 mg/kg/hr.

The lungs will be ventilated with positive pressure ventilation to maintain end-tidal carbon dioxide (EtCO2) between 32 and 36 mmHg.

Patients' heart rate, blood pressure will be monitored continuously and recorded at ten-minute intervals until the end of surgery. Any attack of hypotension, defined as a drop of > 20% of baseline blood pressure, will be managed by ephedrine 0.2 mg/kg IV, and administering I.V. fluids. On the other hand, hypertension, defined as an increase of > 20 % of baseline blood pressure, will be managed by increasing the depth of anesthesia and administering bolus doses of fentanyl 1 mic/kg (up to 3 mic/kg maximum dose).

Bradycardia (heart rate < 50 beats/min) will be managed by atropine 0.02 mg/ kg IV

At the end of surgery residual neuromuscular blockade will be reversed and the endotracheal tube will be removed. Patients will be transferred to the ICU and will be monitored for 24 hours. Patients' heart rate, blood pressure, oxygen saturation and respiratory rate will be monitored at regular intervals and the pain score and sedation level as well.

Epidural infusion will be continued with the same infusion rate. A fixed dose of paracetamol (10 - 15 mg/kg) every 8 hours and NASID (0.5 - 2/kg/ day divided in 2 doses will be administered I.V.

Pain will be assessed using the numerical rating scale (NRS) and if the pain score is more than 3, 3mg morphine I.V. will be administrated intra venous as rescue analgesia (up to .4 mg/kg morphine maximum dose every 24 Hours).

Inclusion criteria

• Age 18 - 60 years old
• ASA physical status I-II-III
• Good mental function.
• Patient scheduled for thoracic surgery with posterolateral thoracotomy.
• BMI of patient (18 - 30).

Exclusion criteria

• Age less than 18 or more than 60 years old
• Any contraindications to epidural injection (patient refusal, local infection at the site of injection, coagulopathy, patients on anticoagulant or antiplatelet drugs, known allergy to local anesthetics, significant spine deformity)
• Inability to provide informed consent or pain score