Comparison of Analgesic Efficacy Between Ultrasound Guided Serratus Anterior Plane Block or Thoracic Paravertebral Block Versus Intravenous Fentanyl for On-pump Coronary Artery Bypass Graft Surgery

this group will be given 20 ml of 0.25% bupivacaine hydrochloride bilaterally

In SAPB; the needle is advanced in-plane from caudally cephalad at the midaxillary line at the level of the fourth rib with 45-degree angle, targeting the plane between the latissimus dorsi and serratus muscles. SAPB block will be performed Bilaterally. After confirmation that the needle tip is in the correct plane by injecting 2 ml of saline, 20 ml of 0.25% bupivacaine hydrochloride [Maracine prepared by adding an equal volume (1:1) of normal saline (0.9%) to 0.5% bupivacaine]will be injected, with intermittent aspiration to confirm neither air nor blood in the needle.

this group will be given 20 ml of 0.25% bupivacaine hydrochloride bilaterally

In TPVB; the needle is advanced in parasagittal plane over the transverse processes of the T4 and T5 vertebrae, about 2.5 cm lateral to the spinous processes, just deep to the superior costotransverse ligament but superficial to the parietal pleura. TPVB will be performed bilaterally. After confirmation that the needle tip is in the correct plane by injecting 2 ml of saline, 20 ml of 0.25% bupivacaine [Maracine prepared by adding an equal volume (1:1) of normal saline (0.9%) to 0.5% bupivacaine] will be injected, with intermittent aspiration to confirm no air or blood in the needle.

Intravenous fentanyl infusion 1µg /kg/h

Patient will receive IV fentanyl infusion just before skin incision, which will be stopped when cardiopulmonary bypass (CPB) is on, then resumed after weaning form CPB and continued till the end of the surgery.500µg fentanyl will be mixed with 50 ml 0.9% normal saline in 50 ml syringe (10 µg /ml).Infusion rate will be determined according to a dose of 1µg /kg/h.

Postoperative visual analogue pain score (VAS): It will be recorded every 1 hour after admission to ICU for the first 4 hours ' then every 2 hours for the remaining 8 hours

Total doses of intra , postoperative fentanyl consumption and doses of rescue fentanyl.

Mean blood pressure (mmHg): Baseline, immediately after performing the block, at 30 minutes intervals (except when the patient on CPB) till the end of surgery Mean blood pressure (mmHg): Immediately after ICU admission, at 1 hour intervals in the 1st 6 hours, then at 2 hours intervals till 12 hours

Postoperative extubation time in minutes.

bleeding , hematoma , inflammation , nerve injury , hemodynamic changes

Pulmonary function assessment [forced expiratory volume at one second as % of predicted) using spirometry: Every 6 hours after extubation up to 12 hours

Heart rate (beats/minute): Baseline, immediately after performing the block, at 30 minutes intervals (except when the patient on CPB) till the end of surgery Heart rate (beats/minute): Immediately after ICU admission, at 1 hour intervals in the 1st 6 hours, then at 2 hours intervals till 12 hours