ALTERATION OF BLOOD DURING ACUTE HYPOTENSION: EFFECT OF CONTINUOUS GLASS WOOL FILTRATION

The present status of blood filtration

The history of the development of blood transfusion and blood filtration is outlined. Clinical and experimental evidence for the efficacy of microfiltration in both small and large volume transfusions is evaluated. Though microfilters do remove the micro-aggregates from stored blood, the results of clinical studies suggest that both the debris from septic processes in the body and the formation of micro-aggregates in the blood stream triggered by processes such as complement activation play a far more important role in the pathogenesis of adult respiratory distress syndrome. If this is so the enhancement of the reticulo-endothelial system by fibronectin therapy may be indicated. It also follows that the use of microfilters is probably an unnecessary expense and, where exsanguination is a risk, may be positively dangerous. Microfilters have been found useful in the preparation of granulocyte-free transfusions after centrifugation of the blood, but their routine use for transfusions, small or large, remains to be justified.

The effect of shear, specific surface, and air interface on the development of blood emboli and hemolysis

Heparinized dog blood was exposed to shear and foreign surfaces in conicylindrical test cells. The cells were injection molded from polycarbonate and were filled using a technique that avoided contact of the blood with air. Particulate-matter formation was measured and was found to be dominated by the surface-to-blood-volume ratio and to be independent of shear rate. Hemolysis was also measured and was found to vary linearly with shear rate and to increase with increasing surface-to-blood volume ratio. Thus, at low shear rates and high specific surface conditions, the degree of hemolysis was found to be minimal while particulate-matter formation was high. The results suggest that the safety of extracoporeal perfusion procedures cannot be inferred from hemolysis measurements alone. In one series of tests, a gas-blood interface was generated at a rate equivalent to the rate of surface renewal in conventional disc oxygenators. The gas-blood interface failed to contribute significantly to the damage indices, which suggests that the apparent superiority of membrane oxygenators may be a result of factors other than the absence of a blood-gas interface.

Blood microfiltration. A review

The factors which contribute to the formation of microaggregates in stored blood for transfusion have been discussed and their significance assessed. The history of the development of blood microfiltration is described. The advantages and disadvantages of screen microfilters in comparison with depth filters are considered. Screen filters with a pore diameter of about 40 micron would appear to have definite advantages.

Banked blood microfiltration. II. Dacron-wool microfilter

It is well established that debris tends to accumulate in banked blood, the amount of debris increasing with storage time. If such a blood is transfused to a patient, it will be filtered by the capillary network of the lungs and could cause various intensities of microemboli. These can be prevented by microfiltration--the Swank IL200 transfusion filter made of Dacron wool is perfectly suitable. It removes more than 70% of the debris 29-100 mum size from four blood units and its efficiency for particle removal is greatly increased by lactate priming.

Dacron wool filtration and hypotensive shock: an electron microscopical study

Images

Pulmonary microembolism after blood transfusion: an electron microscopic study

Images

Screen filtration pressure in combat casualties

Images