analgesic effects of transversus thoracic plane (ttp) block in cardiac surgery

Conditions: Postoperative Pain; Nerve Block; Cardiac Surgery

Summary: the ttp block is a novel regional anesthetic technique that shows promise in providing analgesia for anterior chest wall incisions and median sternotomy. the investigators hope to show that by providing the ttp block, there will be reduced early postoperative pain, reduced sedation and shallow breathing, reduced time on breathing machine, leading to an increase in patient comfort and satisfaction. the investigators also hope the decreased need for pain medication and reduced time on the breathing machine will translate into decreased nursing workload.

in february 2015, ueshima et al published an article regarding ultrasound guided transversus thoracic muscle plane (ttp) block for breast cancer resection. in this article, he showed that branches of the intercostal nerves (th2-6) dominate the region of the internal mammary area. by administering local anesthetics between the internal intercostal and transversus thoracic muscle, analgesia in the anterior chest and sternum can be obtained. a cadaveric study shows injectate spread from the second to fifth intercostal spaces with a single 15ml injection between the third and fourth ribs next to the sternum. they further published a case series of two patients who successfully underwent median sternotomy for aortic valve replacement and thymoma resection using only the ttp block for analgesia. fast- track cardiac surgery is now widely practiced, and evidence for its safety and efficacy has spurred its adoption. with the increased demand for health care resources including nursing manpower and icu beds, postoperative patients are returning to the cardiac surgery intensive care unit (csicu) on shorter acting anesthetic agents so that they can be awakened, following commands and spontaneously ventilating earlier. the ttp block fits in well with the fast- track paradigm. by providing adequate analgesia for median sternotomy, the ttp block may reduce narcotic requirements and consequent sedation and respiratory depression, hypercapnia and respiratory acidosis, prolonged mechanical ventilation and need for emergency advanced airway interventions.

Eligibility criteria:
inclusion criteria: * patients undergoing cardiac surgical procedures performed by a single conventional median sternotomy, and first case of the day patient because early postoperative pain scores are difficult to obtain overnight for patients admitted to the icu in the evening. exclusion criteria: * patients undergoing non-median sternotomy access, surgeries involving saphenous vein or radial artery harvests, emergency cases, lvef (left ventricular efection fraction) \<30%, asaps (american society of anesthesiologists physical status)=5, known local anesthetic allergy, allergy to any study medications, pre-existing major organ dysfunction including hepatic and renal failure, egfr (estimated glomerular filtration rate) \<60ml/min/1.73m2, coagulopathy, hematological disorders, infection at the site of injection, significant psychiatric illnesses (schizophrenia, bipolar, uncontrolled anxiety or depression), narcotic dependency (chronic opioid use of greater than 15mg oral morphine equivalents daily), peripheral neuropathy, pregnancy, patient refusal, lack of informed consent, moderate cognitive impairment, and language or reading barrier.