Cardiopulmonary Bypass ( CPB )

Steps in CPB จดั ทาํ โดย จารุณี บัวกลม ณัฐตยิ า คาํ สอน กง่ิ นภา ฤาชัยราม อาจารยท์ ่ีปรกึ ษา อาจารยณ์ ัชฎา ศุภกจิ เจริญ

Care of Cardiac Surgery Patient • Cardiac surgery,effects of CPB risk to Myocardial infarction → inadequate myocardial protection and emboli The Goal of Myocardial Protection 1. Induced Hypothermia → reduces metabolic rate 2. Cardioplegia solution is cooled to lower temperature for intracardiac cooling as a method of myocardial protection 3. Vents → ↓ heart distension,↓myocardial ischemia exposure surgery filed

Cardiopulmonary Bypass CPB circuit 4 major function • Oxygenation & CO2 elimination • Circulation of blood • Diversion of blood from Heart to provide blood less & stable surgical field • System cooling and rewarming

Open sternotomy Lung down

Exposure the heart and check aorta

Components of CPB • Aortic cannula • Venous cannula • Left ventricular venting (LV vent) • Venous reservoir • Roller pump • Heat Exchanger • Oxygenator • Filter air bubbles

CPB circuit



Anticoagulation HEPARIN • is given after open chest and pericardium • loading dose 300 IU /Kg through central venous line • After 3 min → ACT > 400-480 s normal 80-120 s

Arterial cannula • Arterial before venous due to in case of “emergency volume resuscitation • Prefer site = ascending aorta • Alternative site ex femoral,iliac artery • During aortotomy and insert cannula keep MAP ˂ 70 mmHg (beware dissection)systolic pressure 90-100 mmHg

Arterial cannula • Complication embolization of air or atheromatous debris inadvertent cannulate to aortic arch vv,aortic dissection,other vessel wall injury • Check cannula position, pressure and flow

Venous cannulation • Venous blood enters the circuit by gravity into a reservoir • The amount blood drained determined by CVP,resistance in cannula,tubing,and connectors & absence of air with in the system

Single Venous cannula technique two –stage venous cannula • Insert RA then point inferior • Multistage cannula • Drainage hole both RA and IVC • Used for closed heart surgery (CABG)

Bicaval cannula technique two-single stage cannula • Separate cannulation of SVC and IVC • Right atrial access for operation • Malposition of IVC/SVC cannula • Used for open heart surgery

Venous cannulation

LV Venting • LV venting done to keep the operative field clear \" avoid LV filling and distention during CPB to prevent myocardial rewarming, LV distention and decrease oxygen demand“ • Remove air from cardiac chamber • Blood from LV gose to reservoir bag • Placed vent: Rt superior pulmonary vein, LV, PA, aortic root, direct LV from apex

Other preparation • Check all vascular access • Check all monitoring device • Freeze TEE with unlock and neutral position • Check adequate depth anesthesia and muscle relaxant • Baseline for anesthetic state → anesthetic drug from hemodilution

Initiation and discontinuation of bypass support • Initiation of CPB • During bypass • Preparation of separation • Separation from bypass

Initiation of CPB • anticoagulation • arterial cannulate check arterial line pressure and position • Venous clamp off • On CPB • Full flow • Turn off ventilator • After full flow: CVP to near zero

Initiation of CPB • Hypotension with onset of CPB • At initiation CPB -> MAP 30-40 mmHg • Mechanism: hemodilution from nonblood priming volume-> decrease blood viscosity • Hypothermia effect • After full flow, A line non pulsatile • On CPB state = on CPB beating heart • Aortic cross clamp



Cardioplegia • Separate circuit for infusing a solution into the heart to produce cardioplegia to stop the heart from beating • Provide myocardial protection to prevent death of heart tissue

Cardioplegia • Cardioplegia - crystalloid-based solution (cold) ↑K+ 20- 40mEq/L ↓Ca etc Na,Cl,magnesium chloride - Cardioplegia adult 30 ml/kg q 20-30 min

Cardioplegia • Cannula are placed in the aortic root Antegrade perfuses coronary arteries,solution infused into aortic root where the left main and right coronary arteries above aortic valve’s leaflets • Retrograde infused through a cannula in the coronary sinus the common venous drainage • Direct cardioplegia • If work cardiac arrest

Monitor During Bypass • MAP should be maintained between 50-70 mmHg for organ perfusion • CVP should be low,high CVP poor venous return ( kink,airlock ), facial engorgement • Temperature hypothermia due to operation normal 32-34 C,organ protection,inhibit clotting factors and platelets

Monitor During Bypass • Hb,Hct,Electrolytes,ABG,ACT q 30-40 MIN • Glucose is maintained between 120-180 mg/d • Urine out put • Anesthetic drug or volatile agent on bypass machine • ยาท่ีตอ้ งการการออกฤทธิ์เรว็ ควรให้ ทาง CPB • ยาท่ีไมต่ อ้ งการความรวดเรว็ ในการออกฤทธิ์ให้ ทาง CVP

Problem during bypass • Poor Urine out put ,Mean↓ → mean 60 ,Hct 20-25% volume in reservoir ถา้ ประเมนิ ทกุ อยา่ งแลว้ อาจ ให้ vasopressors (Mean ต่าํ ) diuretic small dose (urineไมอ่ อก)

Monitoring during Bypass

Preparation for separation • Rewarming → blood component FFP platelet • temperature↑ 32-33-34-37 c • Anesthetic drug • Warm blood-based solution (warm or cold) → befor aortic clamp off ( Hot shot ) → myocardial contraction • Head down • Release aortic cross clamp → reperfusion injury - MgSO4 30-50 mg/kg - lidocaine 1-1.5 mg/kg - ยากระตนุ้ การทาํ งานของหวั ใจ

Preparation for separation • Defibrillation • Restoration ventilation • Correction of metabolic abnormality and arterial oxygen saturation • Oxygen-carrying capacity • Arterial PH • Electrolyte • Other final preparation

Defibrillation

Defibrillation • Before discontinue CPB , organized rhythm • Common seen VF after ACC release and rewarm • 1. Compromised subendocardial perfusion • 2. Increase myocardial oxygen consumption • 3. Distend LV • Bolus lidocaine 100 mg before ACC release • Defibrilator adult 10-20 j,child 5-10 j

Restoration of systemic arterial pressure to normothermic value • Discrepency of radial artery pressure and central aorta pressure • May be underestimate 10-40 mmHg, MAP 5-15 mmHg ถา้ ไมแ่ น่ใจ ใหค้ ลาํ aorta , direct central aortic pressure, ทาํ central aortic pressure ท่ีอ่ืน เชน่ femoral artery • Disappear after 20-90 min after discontinute CPB

Removal of intracardiac air • Vary surgical technique • Before ACC release --> head down • Occlude carotid at ACC release-- dangerous • ACC release , vent cannula in aorta • CO2 gas insufflation • Close heart surgery, air 10-30%

Restoration of ventilation • Increase dead space after CPB • Before discontinue CPB re inflate lung with positive pressure 20-40 mmHg • Open area of atelectasis especially LLL • Increase ventilation rate 10-20% • Ventilate with 100% oxygen then adjust FIO2

Separation from bypass • Slow clamp venous line • Flow to patient via aortic inflow-clamp aortic inflow • Evaluate oxygenation, ventilation,myocardial performance -100% O2 • Warm 37 c,Hct > 20% • Normal acid-base status • HR 70-100 /min • Start inotropes if inadequate cardiac out put • Restart volatile opioid • Separate bypass

Protamine • Once bypass is terminated, and after removal of venous cannula,protamine is given to reverse heparin,usually during a 10-15 min period • The reversing dose is approximately 1-1.3 mg of protamine for 100 U of heparin • Heparin-protamine complex activates complement pathway and lead to hypotension • Neutralization of heparin must be confirmed by an ACT

Severe Protamine Reaction • pulmonary vasoconstriction →PHT • systemic vasodilation - hypotension • anaphylactic,edema Rx 100%O2,iv fluid,steriod,antihistamine, bronchodilator,vasoconstrictors

Transfer • Oxygen transfer • Monitor transfer • Resuscitation drugs

Transfer

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