ANAESTHESIA FOR BEATING HEART SURGERY

ANAESTHESIA FOR BEATING HEART SURGERYMODERATOR- Dr Ajay SoodPRESENTED BY- Dr AnupamINTRODUCTION

OPCAB performed first in 1964CABG with CPBThe revival of OPCAB technique occurred in 1980 with two different approaches:MIDCAB- anastomozing the LIMA to LAD through small ant left thoracotomy.The second approach is multivessel grafting without CPB performed through a standard median sternotomy, which gives access to all coronary vessels, and allows standard techniques of mammary artery harvesting.The challenge in beating heart CABG surgery is that it can be difficult to suture or "sew" on a beating heart. The surgeon must use a "stabilization" system to keep the heart steady.The stabilization system consists of a heart positioner/surgical maneuvers to position heart and a tissue stabilizer. The heart positioner guides and holds the heart in a position that provides the best access to the blocked arteries. The tissue stabilizer holds a small area of the heart ,its placed on epicardium over the arteriotomy site to provide regional immobilisation, while rest of the heart is beating normally.The OctopusTissue Stabilizer. Hs 2 flanged suction devices with cups under the flanges which lift & stabilize the myocardium. Its attached to vacuum of 400-600 mm hg..adv- it lifts than to compress heart.

SURGICAL ASPECT:-

midline sternotomy. the left internal mammary artery is harvested. At the time of harvesting, few surgeons wish to administer half dose of heparin (1mg.kg-1) to the patient. Prior to commencement of grafting i.e. before the placement of ts stabilizers, full heparinization is achieved by administering 2-3mg.kg-1 of heparin intravenously.ACT >240 secs is considered adequate. Repeat evry 30 min n repeat dose of heparin if required.The ascending aorta is exposed. A partial cross clamp is applied onto the aorta and a hole measuring 4 mm is punched in the ascending aorta; the proximal end of the proposed conduit is anastomosed to aorta on this punched hole. Followed by distal anastomosis to coronary artery distal to blockade.Heart ispositioned by placing a few mops underneath it. Then,target artery is stabilized by placing the epicardial stabilization devices Commonly used are Octopus & starfish.Stabilizing the heart to expose LAD artery and other anterior coronary arteries does not cause serious haemodynamic problems; however, positioning for viewing the lateral vessels (obtuse marginals) may cause haemodynamic changes.After completion of grafting, residual heparinization is reversed using protamine sulfate (1 mg for every mg of heparin).Pericardium & sternum closed closure.Keep the perfusionist and CPB machine ready before.

ADVANTAGES OF OPCAB OVER CONVENTIONAL CABG:-Decreased ventilatory support & ICU stay, so economically better.Decrsd mortality from 2.9% to 2.3% in OPCABDecrsd complication rate from 12% to 8%Decreased rate of blood transfusionDecreased coagulopathy & renal dysfxn decreased neurological complicationsIts of more benefit in high risk patients. C/I in presence of intracavitary thrombi -malignant vent arrythmias -deep intramyocardial vessels - procedure combined with valve replacement / ventricular aneurysmectomy

PROCEDURES PERFORMED ON BEATING HEART:-Coronary artery bypass graft surgery(includingThoraCAB, a minimally invasive option performed without cutting the breastbone, as well asopen-chest, beating-heart bypass)Surgery for atrial fibrillationTreatment of somecongenital heart defects, such as closure of atrial septal defectValve repair(mitral, pulmonary, or tricuspid)Valve replacement(mitral or tricuspid)Ventricular reconstruction

PROBLEMS ASSOC WITH OPCAB:-

surgeon faces two main problems: First, to obtain an adequate exposure of anastomosis site with restrained cardiac motion; and second, to protect the myocardium from ischemia during coronary artery flow interruption. For this purpose, he must displace the heart, compress the ventricular wall, and if possible use a technique to allow coronary perfusion while performing the anastomosis.the anaesthetist must be prepared to handle severe hemodynamic alterations, transient deterioration of cardiac pump function, and acute intra-operative myocardial ischemia. The team must be prepared for conversion to CPB in case of sustained ventricular fibrillation or cardiovascular collapseGOALS OF ANESTHETIC MANAGEMENTProvision of safe anesthesia using a technique that offers max cardiac protection and stability.Maintaining hemodynamics through out intra-operative period.Allowing early extubation, ambulation.Providing adequate pain relief.MONITORING:

ECG: most imp monitoring. Stick ECG leads on the back of the pt thus decreasing the dislodgement of them in midst of surgery, as well as disturbance during handling of chest.must ensure well visualized P & QRS complexes b4 start of d surgery. its common to notice sudden disappearence of QRS in the midst of surgery due 2 change in cardiac axis caused by positioning of heart. hrt manipulations modify the positional relationship btwn the heart and surface electrodes thus shape of it is altered as well as amplitude is reduced.. Impiaring its diagnostic accuracy.On monitors Use diagnostic mode with ST segment trending ..filtering off done.

Pulse oximetery & capnography : - decrease in ETCO2 during heart manpulation is early sign of decrease in COIntra arterial access-rt femoral preferred-coz 1st, it permits access to the central tree(less suceptible to abnrml values during alterations in BP/hypotension)..2ndly quick access to insertion of intra-aortic balloon pump.Rt radial preffered over left..after allens testcoz with left internal mammary artery harvesting left radial ar pulsations affected. After artery access- take ABG & ACT samplesVenous access & CVP- although rt atrial pressures and PCWP may b distorted wid d verticalization of heart.SvO2 < 50% assoc with bowel ischaemia.

Indications 4 PAC insertion- -LVEF 18 mmHg at rest -recent MI & UA - post MI complications like VSD, LV aneurysm,MR, CCF - emergency surgery -combined procedure - reoperationBIS for awareness monitoring.( 70 mmHg )ask surgeon to reposition cotton packs/ epicardial stabilizersIntra aortic balloon pump supportLook for arrythmias and its causes & treat them

Fig 3 Modification of mitral shape with heart manipulation reconstructed in its threedimensional aspect, as viewed from above (from reference 49, with permission).

Chassot P et al. Br. J. Anaesth. 2004;92:400-413The Board of Management and Trustees of the British Journal of AnaesthesiaFig 3 Modification of mitral shape with heart manipulation reconstructed in its threedimensional aspect, as viewed from above (from reference 49, with permission). (a) Normal saddle shape of the mitral ring when the heart is in its normal position. (b) When the heart is moved to the vertical position, the mitral ring is severely distorted. (c) When the lifted heart is rotated to gain access to the lateral wall, the ring is further folded and twisted. Intra-operative MI :- SIGNS : increase in PCWP or appearance of new v waves .( less sensitive) :SWMA on TEE This can be avoided by :Maintaining MAP of at least 70mmHg.A mixed venous oxygen saturation of at least 60% or more is suggestive of adequate tissue perfusion.Reduction in myocardial oxygen consumption: by avoiding tachycardia using intraoperative beta-blockers, TEA or calcium channel blockers.Bradycardia may decrease cardiac output. It may be easier and faster to correct bradycardia by electrically pacing the patient.A certain degree of ischemia will occur during distal anastomosis and can be prevented by using intraluminal coronary shunts.

PRECONDITIONING- volatile anesthetics such as isoflurane or sevoflurane protect the myocardium against ischemia by activation of a preconditioning- like mechanism when administered at 2 minimum alveolar concentration (MAC) at least 30 min before the ischemic insult. intraop Arrhythmias- cardiac displacement increases the risk..especially reperfusion arrhythmiasmaintain potassium>4.5 , magnesium given after induction.

INDICATIONS FOR CONVERSION TO CPB :-Persistence of the followings for >15 min despite aggressive therapy:Cardiac index