EXTRACORPOREAL CIRCULATION

Dana Noureddine,MD Rayyan Wazzi Mkahal,MD (medical students)

A procedure in which blood is taken from a patient's circulation to have a process applied to it before it is returned to the circulation

All of the apparatus carrying the blood outside the body is termed extracorporeal circuit

Definition:

Cardiopulmonary bypass during open heart surgery

Autotransfusion Hemodialysis Hemofiltration Apheresis Plasmapheresis Extracorporeal membrane oxygenation (ECMO)

Extra corporeal circulation

Is a method that is used to achieve the extracorporeal removal of waste products such as creatinine, urea and free water from the blood when the kidneys are in a state of renal failure. 

Hemodialysis:

Is a similar treatment to hemodialysis, but it makes use of a different principle

Pressure gradient rather than conc. gradient

Convection not diffusion

Hemofiltration:

Is a medical technology in which the blood of a donor or patient is passed through an apparatus that separates out one particular constituent and returns the remainder to the circulation

Apheresis:

Whole blood enters the centrifuge (1) and separates into: plasma (2)leukocytes (3)erythrocytes (4).

Is the removal, treatment, and return of blood plasma from blood circulation.

It is used when a substance in the plasma, such as immunoglobulin, is acutely toxic and can be efficiently removed

Plasmapheresis:

Plasma exchange offers the quickest

short-term treatment to removing harmful

auto-antibodies

It provides both cardiac and respiratory support to patients whose heart and lungs are so severely diseased or damaged

Extracorporeal membrane oxygination:

Guidelines that describe the indications and practice of ECMO are published by the Extracorporeal Life Support Organization (ELSO).

Criteria for the initiation of ECMO include acute severe cardiac or pulmonary failure that is potentially reversible and unresponsive to conventional management

Performed under local anesthesia

Used for long term support ranges 3-10 days

Aim:to allow time for intrinsic recovery of the lungs and heart

ECMO

I’m almost done!

Also known as autologous transfusion

Defined as the collection and reinfusion of patients own blood/ blood compartments.

Safest form of blood transfusion

Autotransfusion:

Advantages

No acute or delayed hemolytic rxn dt ABO incompetability.

No allergic or febrile reactions

No transfusion trasmitted infectious diseases like HIV, HepB, HepC, EBV,CMV and malaria

Conservation of blood resources

Patients with rare blood phenotypes are benefited

Availability – Instantly avialable and requires no cross matching

Clerical error Pre-operative anemia Costlier Unnecessary wastage of blood Risk of bacterial contamination Increased complexity of procedure

Disadvantages

Pre-operative autologous blood donation

Acute normo-volemic hemodilution

Intra operative and post operative

blood selvage

3 types of autotransfusion:

Patient selectivity:1. Hb not<11g/dl2. Hct not<33%Last transfusion 72 hrs before surgery

Contraindication1. Bacteriemia/septicemia2. Unstable angina, CHF, MI within

previous 6 months

Pre-operative Autologous Blood Donation:

It is collecting a patient’s blood (2-4 units) into anticoagulant-containing storage bags at the outset of surgery, accompanied by intravenous replacement with crystalloids or colloids to maintain normovolemia and later reinfusion of blood.

Acute normovolemic hemodilution:

Is an effective method of transfusion avoidance

Shed blood is collected from the operative field and mixed with an anticoagulant.

It is concentrated and washed or filtered, then returned to the patient

Intra-operative blood donation: “ Cell Salvage”

Collection from drains but is rarely used

To be used within 6 hrsBlood collection is diluted and partially hemolysed.

Post-operative blood donation:

Cardiopulmonary bypass:

Heart - Lung - Machine (HLM)/ cardiopulmonary bypass(CPB)

The innovation of the machine for extracorporeal circulation (ECC) was in 1950. The first successful application of this machine was made by Dr. John Gibbon on the 20th May 1953, on a young patient with ASD

With the help of the ECC the heart is emptied, arrested (stopped), opened at the needed chamber, and thus a safe surgical intervention can be made without any consequences to the patient, allowing surgeons to operate about 90 min Price:10-45 thousand $

To provide a stilled bloodless heart with blood flow temporarily diverted to an extra corporeal circuit that functionally replaces the heart and lungs

Respiration◦ Ventilation◦ Oxygenation

Circulation Temperature regulation

Goals of CPB

Surgical correction of congenital, ischemic or valvular heart diseases

Coronary artery bypass Valve replacement Correction of septal defects

Indications:

Basic CPB Circuit

Venous Cannulas

Venous Reservoir

Pump

Heat Exchanger

Oxygenator

Filters

Filters

Filters

Aortic cannulas

The rewarming should be gradual & is done over a 30 minute period

A gradient of I0°c is maintained between patient & perfusate to prevent formation of gas bubbles due to their increased solubility as blood gets warmed

Rewarming

Balanced electrolyte solutionSometimes mannitol is added to stimulate diuresis so to prevent post-op renal dysfunction

Addition of glucose/lactate is avoided because it showed neurological deficits

Priming

As bypass circuits are thrombogenic

Heparin 2-3 mg/kg given into the central vein / directly into the right atrium

Supplemental dose of heparin given every hourly at the dose of 1/3 of initial dose

Anticoagulation

The primary goal of this period is to obtain-

desired levels of hypothermia

maintain adequate systemic perfusion

tissue oxygenation

Maintenance of bypass

To maintain normal myocardial cellular integrity and function during CPB, the available high energy phosphate compounds have to be spared

This is accomplished by◦Hypothermia ◦Cardioplegia

Maintenance of bypass

inserted into the aortic rootIt’s a solution of dextrose, sodium, potassium and chloride..

It is administrated periodically to inhibit myocardial contraction

cardioplegia

Increased extracellular potassium↓

Decrease in transmembrane potential↓

Impairment of Na+ transport↓

Abolition of action potential generation↓

Cardiac arrest in diastole

MOA:

Weaning from CPB Reversal of anticoagulation done with

protamine Dose - 1 to 1.3ml (10mg/ml) for every

1000U of heparin or dose is calculated based on the heparin dose response curve

Arterial cannulas remain in place for continued transfusion of pump contents

When this is completed & bleeding is controlled, arterial cannula is removed & chest is closed

Physiologic CNS –amnesia, Intracranial Haemorrhage (14%),seizures

Respiratory - Pulmonary oedema, pulmonary haemorrhage

Renal-Decreased tubular function, Renal blood flow dt diminshed flow rate

Hematologic - Anemia, leukopenia, thrombocytopenia

Infections

Complications

The absence of significant organ dysfunction probably is the best indicator of successful CPB. Post-CPB organ dysfunction constitutes a spectrum ranging from mild dysfunction in one or more organ systems to death resulting from multiorgan failure.

The probability of significant morbidity increases with duration of CPB and decreasing age of the patient within the pediatric age group

The impact of preexisting organ dysfunction on post-CPB morbidity is not well defined, but it seems likely that poor overall condition before CPB results in greater morbidity after CPB.

For unexplained reasons, women seem to have greater morbidity and mortality after cardiac surgery

MechanicalFailure of pumpRupture of tubing Difficulties with cannulas

Complications