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Title: Blood loss and thrombus formation during haemodialysis
Author: Lindsay, Robert McGregor
ISNI:       0000 0001 3610 5865
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1973
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Abstract:
The objectives of this thesis are to emphasise the importance of extraneous blood loss to the patient receiving maintenance haemodialysis; to demonstrate the source and magnitude of this blood loss; to define the blood loss caused by some commonly used haemodialysers; and to explore the reasons why blood should remain trapped within them. The anaemia of chronic renal failure is seldom corrected by regular dialysis treatment and may be augmented and complicated by the development of folic acid deficiency, iron deficiency, and considerable blood losses. This anaemia is usually associated with a normochromic, normocytic blood film and is basically due to a decreased rate of erythropoiesis associated with the incomplete correction of the-uraemic syndrome afforded by haemodialysis. Androgen and cobalt therapy have been advocated as a means of increasing the rate of erythropoiesis but results have not been universally satisfactory. Folic acid deficiency is easily dealt with by oral supplements but the achievement of proper iron balance on regular dialysis is a complex problem as the patients tend to have a decreased ability both to absorb oral iron and to incorporate iron into erythrocytes. Furthermore, iron losses attributable to volumes of blood lost during haemodialysis, are high. In previous years haemoglobin levels were maintained by repeated blood transfusions but this policy is no longer acceptable because of the risks of hepatitis. Considering these factors it is obvious that attention must be paid to sources of blood loss. The sources of blood loss during haemodialysis may be enumerated as follows: blood loss from the arteriovenous shunt or fistula during connection and disconnection of the patient to the dialyser; blood samples taken for investigations; blood loss following dialyser rupture; the residual blood volume in the dialyser and its blood lines after use; and other co-incidental losses such as menorrhagia. It soon became apparent to the author that much was unknown about the degree and relative importance of these various potential sources of blood loss. An early necessity was to establish a method for measuring the dialyser blood loss. This was developed and found to be highly accurate. Using this method the magnitude of the blood losses from various commercially available dialysers and their blood lines was estimated as were the volumes of blood lost during routine use of the arteriovenous shunt and fistula. This data made it possible to consider the probable volumes of blood that a patient undergoing thrice weekly haemodialysis would lose per annum. The volumes ranged from 3 to 8 litres of blood depending upon the type of dialyser used. Special consideration was, therefore, given to the reasons why blood would remain trapped in a dialyser and not be returned to the patient. Two factors were found; firstly, the mechanical hold-up of anticoagulated blood due to the design of the blood compartment and secondly, the development of thrombus upon the dialysis membranes. The first source can be minimised by the development of efficient 'wash-back' procedures but the trapping of red blood cells by thrombus is uninfluenced by either the nature or the volume of the 'wash-back' used. Thrombus formation upon dialysis membranes is the factor which differentiates dialysers with high blood losses from those with acceptable losses. The factors responsible for this thrombus formation, which occurs in spite of adequate heparinisation, have been delineated. A study of the changes in haemostatic factors occurring in the blood of patients underoing haemodialysis suggested that platelet retention by dialysis membranes is an important early step in a reaction which may proceed to thrombus formation. This hypothesis is supported by a subsequent investigation in which it was shown that the inhibition of platelet function by aspirin and a dipyridamole compound was associated with a reduction in the numbers of platelets retained by dialysis membranes and in the amount of thrombus formed on the membranes.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (M.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.463307  DOI: Not available
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