Extracorporeal+membrane+oxygenation

toc
 * ==What is it?==


 * Outside of body cardiopulmonary support.
 * Cardiac surgery to minimize heart movement.
 * Prolonged use in intensive care units.
 * Hypoxemic respiratory failure (PaO2/FiO2 <100 mmHg) despite optimizing ventilator.
 * Hypercapnic respiratory failure with arterial pH <7.20.
 * Refractory cardiogenic shock.
 * Cardiac arrest.
 * Failure to wean from cardiopulmonary bypass after cardiac surgery.
 * Bridge to either cardiac transplant or placement of VAD.
 * ==How does it work? ==
 * First heparinize patient before cannula placement.
 * IV 300-400u/kg.
 * Adequacy of anticoagulation is confirmed by ACT (activated coagulation time) >450s during CPB and 210-230 during ECMO
 * Aorta cross clamp
 * Between antegrade cardioplegic line and arterial inflow to separate the heart from the circulation.
 * Venous return line
 * Gravity drainage of blood from the vena cava into a reservoir.
 * Improved by raising OR bed or small negative pressure in reservoir.
 * <span style="font-family: Arial,Helvetica,sans-serif;">If competent AV, single venous cannula in the RA or dual catheters in the SVC and IVC.
 * <span style="font-family: Arial,Helvetica,sans-serif;">If AV not competent:
 * <span style="font-family: Arial,Helvetica,sans-serif;">LV vent via pulm vein.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Pulmonary venous drain.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Aspiration from antegrade cardioplegia line.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Reservoir
 * <span style="font-family: Arial,Helvetica,sans-serif;">Priming machine creates a siphon effect.
 * <span style="font-family: Arial,Helvetica,sans-serif;">If reservoir is allowed to empty, air can enter the main pump and cause air embolism.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Bubble detector
 * <span style="font-family: Arial,Helvetica,sans-serif;">Pump
 * <span style="font-family: Arial,Helvetica,sans-serif;">Mechanical pump
 * <span style="font-family: Arial,Helvetica,sans-serif;">Centrifugal pump
 * <span style="font-family: Arial,Helvetica,sans-serif;">3 disks rotating at 3000-4000 rpm that use blood viscosity to pump blood.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Better than roller pumps because less traumatic to blood cells, no air bubbles, and afterload dependent avoiding line rupture with clamping
 * <span style="font-family: Arial,Helvetica,sans-serif;">Placed between reservoir and oxygenator.
 * <span style="font-family: Arial,Helvetica,sans-serif;">No pulsatile flow option.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Roller pump
 * <span style="font-family: Arial,Helvetica,sans-serif;">Rotating pump that peristaltically "massage" the tubing to propel blood forward.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Constant speed of the rollers pumps blood regardless of the resistance encountered.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Placed after the oxygenator.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Pulsatile blood flow possible.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Heat exchanger
 * <span style="font-family: Arial,Helvetica,sans-serif;">Hot or cold water countercurrent flow system.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Traditionally: 18C prior to circulatory arrest, 28C during aortic cross-clamping, and 37C prior to weaning.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Newer protocol: maintain 31-33C throughout.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Gas solubility decreases as blood temp rises àbuilt in filter to prevent bubbles.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Oxygenator
 * <span style="font-family: Arial,Helvetica,sans-serif;">Infuse O2 and remove CO2.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Bubble: blood-gas interface.
 * <span style="font-family: Arial,Helvetica,sans-serif;">Membrane: blood-silicone membrane-gas interface cause less trauma to the blood.
 * <span style="font-family: Arial,Helvetica,sans-serif;">O2 maintained by adjusting O2 concentration.
 * <span style="font-family: Arial,Helvetica,sans-serif;">CO2 maintained 35-45 mmHg by controlling the sweep (total free gas flow via oxygenator).
 * <span style="font-family: Arial,Helvetica,sans-serif;">Circuits are flushed by CO2 to reduce gas emboli (CO2 more easily absorbed than N2).
 * <span style="font-family: Arial,Helvetica,sans-serif;">Filter
 * <span style="font-family: Arial,Helvetica,sans-serif;">i. Remove blood clot, latex, talc, fat, polyethylene, etc. that could act as systemic emboli.
 * <span style="font-family: Arial,Helvetica,sans-serif;">ii. Can be located anywhere in the circuit but a final arterial filter must be present before returning to ascending aorta.
 * <span style="font-family: Arial,Helvetica,sans-serif;">j. Tubing
 * <span style="font-family: Arial,Helvetica,sans-serif;">i. Flushed with CO2 then primed with crystalloid- plasma-lyte.
 * <span style="font-family: Arial,Helvetica,sans-serif;">ii. Additives may include albumin, hetastarch, blood, bicarb, heparin, and ABx.
 * <span style="font-family: Arial,Helvetica,sans-serif;">k. Cardioplegia pump
 * <span style="font-family: Arial,Helvetica,sans-serif;">i. Goal is to decrease myocardial damage introduced by ischemia during CPB.
 * <span style="font-family: Arial,Helvetica,sans-serif;">ii. Cardiopledia solution
 * <span style="font-family: Arial,Helvetica,sans-serif;">1. Potassium: blocks the initial phase of myocardial depolarization.
 * <span style="font-family: Arial,Helvetica,sans-serif;">2. Cold temp: decrease heart muscle O2 consumption.
 * <span style="font-family: Arial,Helvetica,sans-serif;">3. Additives: blood, insulin, glucose, aspartate, glutamate, Ca, Mg, nitroglycerine, etc.
 * <span style="font-family: Arial,Helvetica,sans-serif;">iii. Route of infusion
 * <span style="font-family: Arial,Helvetica,sans-serif;">1. Into the aortic root.
 * <span style="font-family: Arial,Helvetica,sans-serif;">a. With clamp present and competent AV, solution divert into coronary arteries.
 * <span style="font-family: Arial,Helvetica,sans-serif;">2. Alternatively, infuse retrograde into coronary sinus.
 * <span style="font-family: Arial,Helvetica,sans-serif;">3. 2 types (ECMO):
 * <span style="font-family: Arial,Helvetica,sans-serif;">a. Venoarterial- respiratory and hemodrynamic support.
 * <span style="font-family: Arial,Helvetica,sans-serif;">i. Cardiac pulmonary bypass: right atrium extraction and reinfuse into the ascending aorta.
 * <span style="font-family: Arial,Helvetica,sans-serif;">ii. Right common femoral vein for drainage and right femoral artery for infusion.
 * <span style="font-family: Arial,Helvetica,sans-serif;">iii. Alternatively, right common carotid or axillary artery can be used.
 * <span style="font-family: Arial,Helvetica,sans-serif;">b. Venovenous – respiratory support only.
 * <span style="font-family: Arial,Helvetica,sans-serif;">i. Right common femoral vein for drainage and right IJ for infusion.
 * <span style="font-family: Arial,Helvetica,sans-serif;">ii. Alternatively, double lumen cannula large enough to accommodate 4-5L/min blood.
 * <span style="font-family: Arial,Helvetica,sans-serif;">4. Indications for ECMO
 * <span style="font-family: Arial,Helvetica,sans-serif;">a. Acute respiratory failure
 * <span style="font-family: Arial,Helvetica,sans-serif;">i. Conventional ventilator support vs ECMO for severe acute respiratory failure (CESAR) trail
 * <span style="font-family: Arial,Helvetica,sans-serif;">1. 180 patients with severe but potentially reversible ARF.
 * <span style="font-family: Arial,Helvetica,sans-serif;">2. ECMO group had sig. increased survival without disability at 6 months (63 vs 47%).
 * <span style="font-family: Arial,Helvetica,sans-serif;">b. Cardiac failure
 * <span style="font-family: Arial,Helvetica,sans-serif;">i. Less extensively studies than ECMO for ARF.
 * <span style="font-family: Arial,Helvetica,sans-serif;">ii. Observational studies reported survival rates of 20-43% among patients who received VA ECMO for cardiac arrest,
 * <span style="font-family: Arial,Helvetica,sans-serif;">severe cardiogenic shock, or failure to wean from bypass following surgery.
 * <span style="font-family: Arial,Helvetica,sans-serif;">5. Complications
 * <span style="font-family: Arial,Helvetica,sans-serif;">a. Bleeding
 * <span style="font-family: Arial,Helvetica,sans-serif;">i. 2/2 continuous unfractionated heparin infusion and platelet dysfunction (contact and sheer stress associated
 * <span style="font-family: Arial,Helvetica,sans-serif;">activation).
 * <span style="font-family: Arial,Helvetica,sans-serif;">ii. In ICU, heparin can be discontinued for several hours or infuse plasminogen inhibitors àthromboemboli risk!
 * <span style="font-family: Arial,Helvetica,sans-serif;">iii. Last resort is to infuse activated factor VII since mixed results have been reported.
 * <span style="font-family: Arial,Helvetica,sans-serif;">b. Thromboembolism
 * <span style="font-family: Arial,Helvetica,sans-serif;">c. Cannulation-related
 * <span style="font-family: Arial,Helvetica,sans-serif;">i. Vessel perforation, arterial dissection, distal ischemia, incorrect location.
 * <span style="font-family: Arial,Helvetica,sans-serif;">d. Heparin-induced thrombocytopenia
 * <span style="font-family: Arial,Helvetica,sans-serif;">i. Increasingly common.
 * <span style="font-family: Arial,Helvetica,sans-serif;">ii. Replaced by non-heparin anticoagulant àargatroban because of its short half-life and similar
 * <span style="font-family: Arial,Helvetica,sans-serif;">ACT target range.

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