Blood exchange, extracorporeal

The presence of an extracorporeal bypass circuit results in large heat losses from the blood. Thus an integral heat exchanger is essential to regulate the patient s body temperature. To decrease the oxygen demand during surgery, the patient s body temperature is often maintained at 5°C-10°C below normal body temperature. 

Therapeutic plasma exchange (TPE), or plasmapheresis (PP), is an extracorporeal therapy most frequently used in the treatment of hematologic disorders, and autoimmune neuropathies and vasculitides [37]. This modality occasionally is also employed in the treatment of poisoning. The apparatus involves central venous access and a blood circuit between the patient and a pheresis machine. Cytopheresis by centrifugation or filtration then separates the formed elements of blood from plasma. The cells are returned to the patient while the plasma (with the poison) is discarded. Fluid volume is typically replaced with crystalloid, colloid, or fresh frozen plasma (FFP) if clotting factor repletion is necessary. 

Extracorporeal blood gas exchange devices have been used on infants with the respiratory distress syndrome (RDS) (4, 5). Twenty-five thousand newborns are estimated to die from this disease every year in this country (6). Though the causes of this disease are not clearly understood, it is hoped that supporting the infant with the aid of an extracorporeal-gas exchanger will give his own lungs time in which to heal. 

Extracorporeal blood gas exchange is only one method of treating the hypoxic infant. Hypothermia and hyperbaric oxygenation, alone and in conjunction with extracorporeal blood gas exchange, have been used to lower or to meet the metabolic requirements of the infant. 

The extracorporeal gas exchanger should be atraumatic to blood. Ideally, there should be no rise in plasma-free hemoglobin secondary to... 

Wo Implantable, artificial lungs exist at this time hut some research has been done on polymeric membranes that could be used In such a device. Extracorporeal blood oxygenators are, however, used In excess of 100,000 times a year (l) and contain a thin, polymeric membrane thru which O2 and CO2 are exchanged. These oxygenators, which exist in several different styles are widely used In by-pass and other operations. The main polymers used are silicone rubber but poly(alkyIsulfones) and some others show promise (l, 50, 5l). 

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