Filtration, Venting, Suction Cooper University Hospital: School of Perfusion 2014 Michael F. Hancock

Filtration Things that need to be Filtered: Gaseous Emboli Blood Field Microemboli- < 40 micron Macroemboli- > 40 micron Gases- O2, CO2, nitrous oxide, N Blood Clots Fibrin formation Platelet activation Complement activation Agglutination of damaged RBCs Field Fat or bone particulate Foam Heart-Lung Machine Tubing pieces due to spallination of roller pump CPB air

Emboli and Thrombus Thrombus- stationary clot Emboli- mobile clot Coronary artery plaque Emboli- mobile clot Air embolus Broken off pieces of a thrombus Travels upstream and occludes vessels Particulate matter traveling through vessels Bone or fat pieces

Air Emboli Surgical Air- CPB Air- Cannula sites Open atrium or ventricle CPB Air- Emptying or Vortexing of resevoir Excessive VAVD (vacuum assist venous drainage) Rapid rewarming Roller Pump tubing rupture Roller Pump off, cardioplegia pump on Draw air across the oxygenator Injection of air through drug syringes

Air Emboli Air Emboli seen on CPB: Brain Right Coronary Artery Carotid Arteries at the Aortic Arch Air rises to these vessels and causes stroke Trendelenburg position used to put the “head down” to prevent any air emboli from reaching the head Right Coronary Artery Right Coronary Ostia is located on the upper portion of the aorta making it susceptible to air rising into the vessel causing an obstruction

CPB Filters Filters are placed at various spots in the CPB circuit to protect the patient against embolus during surgery Designed to trap air and any substance that could cause obstruction in the patient’s vasculature Must allow adequate blood flow and certain components through > 20 microns to allow adequate blood flow without excessive back pressures RBCs are 5-7 microns, must allow them to pass through Platelets are 2-3 microns Leukocytes are 7-21 microns

Types of Filters Depth Filters- Made of packed fibers of Dacron Wool Work by Impaction and Absorption No defined pore size Lose efficiency as time goes on More hemolysis Less air trapping capability More platelet activation and destruction

Types of Filters Screen Filters- Made of woven polyester mesh or Nylon Work by interception Specific pore size Useful for trapping air and particulate matter without impeding flow or causing much hemolysis and platelet dysfunction

Filter Locations Arterial Line Cardiotomy Resevoir Pre-Bypass Pack Cardioplegia System Gas Line Transfusion Line

Arterial Line Filter Arterial Filter- Located after oxygenator and before patient Air enters the side, swirls and around and exits the bottom, which allows air to rise and be purged out of a line with a one-way valve leading to the cardiotomy resevoir Last point of defense before returning to the patient Can be integrated with the oxygenator Newer oxygenators

Ideal Arterial Filter 20-40 microns Small priming volume Trap emboli and allow adequate flow 40 micron preferred Small priming volume ~ 100cc Easy to de-air Made of polyester NOT Nylon Causes complement activation and hemolysis Have bypass line in case filter clots

Cardiotomy Resevoir Cardiotomy Resevoir Filters all blood returning to CPB circuit From Vents and Suckers Most aggregates caused by suckers Filters venous blood Filters drugs injected into CPB circuit manifold Uses combination of Depth and Screen filters 100 microns

Pre-Bypass Filter Located in sterile tubing pack or before venous resevoir Removes particulate matter generated by manufactoring or priming Spallination, Plastic debris 5 micron size Must remove before CPB Will trap RBCs (5-7 microns) 3/8” Line going in ½” Line going out

Cardioplegia Filter Some places use 20-40 micron filter on their cardioplegia system Cooper does NOT

Gas Line Must filter out bacteria and particulate debris 0.2 micron filter will filter 99% of bacteria Used for O2, CO2, and Nitrous Oxide Hydrophobic membrane removes particulate Bi-directional filter ¼” Lines

Transfusion Filter All blood added to CPB circuit or to the patient should be transfused through a filter Pall Filter Reduction in leukocytes, fat globules, C3a, and microaggregates 40 micron filter

Bubble Point Pressure The pressure required for an undissolved air bubble to be pushed across a filter pore Determines when a bubble will get through your filter Calculation- BBP= (4)(surface tension)(cos. Wetting angle) Diameter

CO2 Flushing Rid the circuit of O2 and N CO2 is 20x more soluble than O2 We would rather have CO2 in our circuit because any remaining air bubbles would have a greater chance to dissolve in blood Most important to CO2 flush the arterial filter

Ultrafiltration (Hemoconcentration) Ultrafiltration- the process of removing plasma free water and solutes from the blood Uses: Hemoconcentration- remove plasma free water and raise the hemoglobin Remove excess fluid in lieu of diuretics Zero-Balance Ultrafiltration- used to reduce high Potassium levels (Hyperkalemia) Pull off plasma water and solutes, such as K+, then replacing the fluid taken off with 0.9% normal saline

Hemoconcentrator Semi-permeable hollow fiber device Inflow line comes from the arterial port out of the oxygenator Outflow line goes into a port on the cardiotomy resevoir Water and solute extraction occurs through a separate port

Hemoconcentrator Flow through a hemoconcetrator can be as great as 500 cc/min Fluid removal can go up to a rate of 180 cc/min but is usually 30-50 cc/min Suction may be applied to water extraction line to facilitate water takeoff Transmembrane pressure can be increased by partially clamping hemoconcentrator outflow line Increases the amount of solute and water extracted Flow remains the same Max. transmembrane pressure is 500 mm Hg Can increase flow to hemoconcentrator by increasing pump flow

Hemoconcentrator Filter size is 15,000-55,000 daltons Solutes removed: Some Heparin will be removed Heparin mean molecular mass is 15,000 daltons Solutes removed: K (39 da) Na (22 da) Cl (23 da) Insulin (~6,000 da) Glucose (180 da) Urea (60 da) Creatinine (113 da) like dialysis? Bicarbonate (84 da)

Hemoconcentrator Potential Problems Generation of Plasma free Hemoglobin due to hemolysis Can precipitate iron and cause renal artery vasoconstriction

Venting the Heart on CPB Cardiac Vents- Allow for continuous venting of the heart Maintains an empty heart Prevents fluid distension in the heart Starling’s Law Prevents pooling of warm blood in the LV Could get into coronaries and interrupt asystole Prevents ejection of air Vent Tubing- placed in a roller head to direct blood into cardiotomy resevoir LV Vent should always contain a One-Way valve to prevent pumping air into the LV

Causes of LV Distension Inadequate drainage of venous cannulas Bronchial and Thebessian vein return Bronchial veins drain into the pulmonary veins which drain into the Left Atrium Aortic insufficiency Congenital or aquired heart defects ASD, VSD, PDA

Vent Sites Left Ventricle Aortic Root Pulmonary Artery Apex- direct Right Superior Pulmonary Vein- most common Aortic Root Attached to an antegrade cardioplegia cannula through a Y Commonly used in CABG cases to vent the heart Cardioplegia delivery must be interrupted if LV distension occurs Separate Root vent for de-airing before left heart is closed during valve surgery Pulmonary Artery

RSPV Vent Insertion Incision made in the RSPV Vent inserted Must have volume in the heart to insert vent….WHY?

RSPV Vent Insertion Fingers checking correct position of LV Vent

RSPV Vent Insertion LV vent inserted and advanced across the Mitral Valve Vent sits in the LV

Vent Types A- B- C- D- 1- 2-

Suckers Sucker cannulas are used at the field to suck back any blood in or around the chest cavity Primary source of particulate entering the CPB circuit Blood/air interface causes hemolysis Excessive suction pressure causes hemolysis Be aware of sucker occlusion at the field Will see collapse and chugging of your sucker tubing