Bilateral Pecto Intercostal Fascial Plane Block After Open Heart Surgeries

Pain following cardiac surgery is caused by many factors; sternotomy, chest wall retraction, opening of the pericardium, internal mammarian artery harvesting, saphenous vein harvesting, surgical manipulation of the parietal pleura, chest tube insertion and other musculoskeletal trauma occurring during surgery.

The pain following cardiac surgery is mainly attributed to sternotomy, with its peak during the first two days after the operation. Poststernotomy pain is not well tolerated by patients and may be accompanied by adverse postoperative events including delirium, hypertension, tachycardia, arrhythmia, respiratory complications, and persistent postsurgical pain.

Commonly pain management after cardiac surgery has been achieved using opiate analgesics. However, opiates have some dose-related side-effects such as nausea, constipation, vomiting, dizziness, mental confusion and respiratory depression, which may influence patient recovery and may delay discharge after surgery.

The pecto-intercostal fascial block (PIFB) was recently introduced by de la Torre et al for anesthesia during breast surgery. Local anesthetic is infiltrated into the interfascial plane separating pectoralis major and the intercostal muscles lateral to the sternum to anesthetize the anterior cutaneous branches of the intercostal nerves.

The pecto-intercostal fascial plane block can cover anterior branches of the intercostal nerves from the 2nd to 6th dermatomes with a single injection bilaterally, same as the transversus thoracic muscle plane block .

anesthetic management: All patients will be preoperatively examined and investigated by complete blood count, coagulation profile, renal and kidney functions and electrolytes. Electrocardiography, chest x ray and echocardiography will be routinely done. Coronary angiography and carotid arterial duplex will be requested in patients prepared for CABG.

Patient will be premedicated by intramuscular injection of 10mg morphine in the morning of the operation. Before induction of anesthesia, a five-lead electrocardiography system will be applied to monitor heart rate, rhythm, and ST segments (leads II and V5). A pulse oximeter probe will be attached, and a peripheral venous cannula will be placed. For measurement of arterial pressure and blood sampling, a 20 G cannula will be inserted into either right or left radial artery under local anesthesia. General anesthesia will be induced by midazolam 2-5 mg, fentanyl (10 μg/kg), propofol (3-4mg/Kg), followed by atracurium (0.5 mg/kg).

Trachea will be intubated, patients will be mechanically ventilated with oxygen in air so as to achieve normocarbia. This will be confirmed by radial arterial blood gas analysis. An esophageal temperature probe and a Foley catheter will also be placed.

For drug infusion, a triple-lumen central venous catheter will be inserted via the right internal jugular vein.

Anesthesia will be maintained by inhaled Isoflurane 0.4 to 1% and atracurium infusion at a rate of 0.5 mg/kg/h for continued muscle relaxation. During extracorporeal circulation, patients will receive propofol infusion at a rate of 100-200 mg/h in addition to atracurium infusion.

Before initiation of cardiopulmonary bypass (CPB), the patients will receive intravenously tranexamic acid (2 g) and heparin (300-500 units/kg body weight) to achieve an activated clotting time > 480 s. CPB will be instituted via an ascending aortic cannula and a two-stage right atrial cannula. Before, during, and after CPB (pump blood flow: 2.4 l/min/m2), mean arterial pressure will be adjusted to exceed 60 mmHg. Cardiac arrest will be induced with cold antegrade blood cardioplegia or warm intermittent antegrade crystalloid cardioplegia. Lactate-enriched Ringer's solution will be added to the CPB circuit to maintain reservoir volume when needed, and packed red blood cells will be added when hemoglobin concentration decrease to less than 7 g/dl.

After rewarming the patient to 37°C and separation from CPB, reversal of heparin by protamine sulfate (1:1), and sternal closure will be achieved.

All patients then will be shifted to the intensive care unit (ICU) after the surgery and managed with the institution's ICU protocol for postoperative pain management and ventilation. The postoperative analgesia protocol involves the use of intravenous morphine or morphine equivalent dose of 5to 10 mg/kg bolus as required. Criteria for administration will be signs of sympathetic stimulation in the form of undue tachycardia, a rise in mean arterial pressure (rise of >20% from the baseline).

Tracheal extubation will be performed when the patient met the following criteria: awake/arousable, hemodynamically stable, no active bleeding, warm peripheries, and satisfactory arterial blood gas with an FiO2 < 0.5,pressure support on ventilator reduced to 10 Cm H2O,Positive End Expiratory Pressure 5-7 CmH2O, no electrolyte abnormalities, minimal inotropic support, or no escalation in inotropic support.

Statistical analysis Sample size was calculated using (G power version 3). Minimal sample size of patients was 31 in each group needed to get power level 0.90, alpha level 0.05 and 30% as a difference between the two groups in the morphine consumption after the intervention. To overcome problem of loss of follow up, calculated sample size was increased by 10% to reach 35 in each group.