Thoracotomy is one of the most painful surgical procedures. Post-thoracotomy pain can adversely affect coughing and deep breathing, resulting in respiratory complication such as hypoxia, atelectasis, chest infection and respiratory failure that may delay recovery and if severe, could be life-threatening. It may also contribute to the development of chronic pain syndrome.⁶

                   Serratus anterior plane block is one such technique, providing paraesthesia for the ipsilateral hemithorax⁴. This block has been used for breast surgery, thoracoscopy, rib fracture analgesia and shoulder surgery^7-11. Serratus anterior plane block was originally described by Blanco et al⁴.

Regional anaesthesia by ultrasound guided serratus anterior plane block (SAPB) is one of the efficacious and safe technique that provide good postoperative analgesia in post thoracotomy pain,

                   Intercostal nerve block (ICNB) also is a well-known regional anaesthesia technique for post-operative analgesia in thoracotomy, there is no study in literature regarding comparison between SAPB, ICNB and PECS 1 Block for postoperative analgesia in Adult cardiac surgical patients undergoing thoracotomy.

HYPOTHESIS

                   After looking at the previous studies and understanding the various regional anaesthetic techniques for postoperative analgesia after thoracotomy, use of Ultrasound guided blocks increase the accuracy of blocks. we hypothesize that Ultrasound guided serratus anterior plane block and Pectoral nerves (PECS) 1 block may have predictive value in providing analgesia and faster recovery in Adult patients undergoing cardiac surgery requiring thoracotomy.

 Study design:      The study will be a Prospective randomize control open label comparative clinical study.  In our study the study groups are identified by the decrease or abolition in pain severity and duration in patients with cardiac surgery undergoing thoracotomy.

100 patients will be recruited in the study and will be randomized into three groups by using computer generated simple random number table. The sample size estimated statistically to detect a difference in MAP of 5.0 mmHg after 1 hour of the block with a pooled standard deviation of 3.8 between the three groups, with an alpha error of 0.1 and power of 90%. A minimum of 30 patients per group was needed to detect the difference, and is based on the previous study^5,12.

Definitions. Criteria for Pain Assessment: The postoperative thoracotomy pain as judge by the Visual Analog score (VAS) of 10 points with score 0 having no pain at all to score Face 10 having pain as much as you can imagine. The patients will be monitor till 12 hrs postoperatively after extubation with 2 hours interval using bed side VAS score. Rescue analgesia given by injection Fentanyl for VAS >4 will be also recorded.

Anaesthesia Technique: All preoperative cardiac medication will be continue until the morning of surgery. Premedication will consist of 0.1 mg/kg morphine and 0.5 mg/kg promethazine intramuscularly 1 hour before the surgery. After coming to operative room, initial monitoring will include a 5-lead electrocardiogram, Noninvasive blood pressure, and pulse oxymetry. After peripheral venous line and arterial line cannulation under local anaesthesia, anaesthetic induction will performed with Propofol 2 mg/kg, fentanyl 2 mcg/kg and rocuronium 1 mg/kg. The maintenance of anesthesia will be achieved with inhaled isoflurane in an air-oxygen mixture with 50% fraction of inspired oxygen concentration and muscle relaxation with intravenous infusion of atracurium at the rate of 0.5 mg/kg/h. Patients will ventilate to normocapnea by an anesthesia ventilator.

After completion of surgery and skin closure, Ultrasound guided SAP Block will be performed while patient still in lateral position with the thoracotomy side up. A linear Ultrasound Transducer (10-12 MHz) will be placed in a sagittal plane over the mid clavicular region of the thoracic cage, then the ribs were counted down until the fifth rib identify in the mid axillary line. The following muscle will be identify overlying the fifth rib: The Latissimus dorsi (superficial and posterior), Teres major (superior), and Serratus muscles (deep and inferior). A 22 gauge, 50 mm, stimuplex needle will introduce in place with respect to the ultrasound probe, targeting the plane superficial to the serratus anterior muscle. Under continuous ultrasound guidance 2.5 mg/kg Ropivacaine 0.5% will be injected in this plane.

Intercostal nerve block: intercostal nerve block will be perform after skin closure and in lateral position with thoracotomy side up palpating the rib in the mid axillary line. A 25 gauge needle is introduce perpendicularly through the skin onto the rib and gently walked down the rib to its caudad edge. At this point, the needle is angled posteriorly and advanced slightly medially and posteriorly so that it is almost parallel to the rib, until the tip of the needle lies 1-2 mm beneath the edge of the rib. The bevel of the needle faces cephalad. A loss of resistance is frequently experienced and the needle felt to slide into the subcostal space. After aspirating if no blood or air is withdrawn 2 ml of 0,5% Ropivacaine is injected in each space (2 space above and 3 space below the thoracotomy incision).

Pectoral Nerves (PECS) 1 Block: After sterile preparation of the chest wall in the infraclavicular and axillary areas, an initial scan was performed with a high-frequency (12 MHz) linear array ultrasound transducer (UST) to note the baseline anatomy. The UST was held transversely below the lateral third of the clavicle. Pectoralis major (PMm), pectoralis minor (Pmm), and the vessels lying in between were identified. After identifying the clavicle and the second rib, the UST was moved caudally and laterally to the third rib where lateral margin of Pmm and serratus anterior (SA) (lying beneath the pectoralis minor and above the ribs) could be seen. It is important to identify the pleura as a shining white line and the rib as a hyperechoic bar just above it. The ultrasound field is centered over the rib so that the needle advancing in plane can easily hit the rib. After visualizing the 2 muscle planes, superficially between the 2 pectorals and deep between Pmm and SA, we introduced a 22G stimuplex needle in plane of the ultrasound beam from medial to lateral direction toward the anterior axillary line. The needle was advanced in plane until it reached the rib and then it was withdrawn so that the tip lies in the plane between SA and Pmm. Placement of the needle tip was confirmed by injecting 2-mL saline and visualizing the spread of the saline in the intended plane. After confirming negative aspiration, 2.5mg/kg of 0.5% Ropivacaine (half dose) was injected. After this, the needle was carefully withdrawn so the tip lies between the 2 pectorals, and again after careful aspiration and hydrodissection, 2.5 mg/kg of 0.5% Ropivacaine (rest half dose) was injected.

Data Collection Worksheet.            

The complete data would be recorded in a worksheet as per the annexure. The worksheet would be separate for all the patients and would contain all the information of the patient from hospital no. to diagnosis to surgery performed as per the Performa. The same would also have the values of all the findings for any future reference. Each worksheet would be kept confidential.