tailieunhanh - Mollison’s Blood Transfusion in Clinical Medicine - part 5

Một tế bào màu đỏ của con người, trẻ sơ sinh và phát hành vào lưu thông, có tuổi thọ khoảng 120 ngày. Tế bào màu đỏ truyền cũng tồn tại trong thời gian dài trong lưu thông của người nhận. Tuy nhiên, các tế bào ở các độ tuổi khác nhau cùng tồn tại trong các bộ sưu tập túi, vì vậy sự tồn tại và tuổi thọ không phải là các điều khoản hoán đổi cho nhau | 9 The transfusion of red cells The survival of transfused red cells A human red cell newborn and released into the circulation has a lifespan of about 120 days. Transfused red cells also survive for long periods in the recipient s circulation. However cells of different ages co-exist in the collection bag so survival and lifespan are not interchangeable terms. Less than 1 of the red cells transfused are destroyed each day which explains why red cell transfusion is so effective. Most cells are removed from circulation by the natural course of ageing others meet a premature end as the result of chance destruction disease-related debility or in the case of transfusion attack by alloantibodies. Estimates of red cell survival are not often needed in clinical practice. However they can be helpful when a compatibility problem arises for example when serologically compatible red cells have been involved in a haemolytic transfusion reaction. In contrast red cell recovery and survival studies continue to be essential in establishing the value of new methods of red cell preservation and modification. Studies of red cell survival depend upon techniques for labelling cells either by injecting some isotopic precursor that will be taken up by a cohort of developing cells or more often by withdrawing an aliquot of cells of mixed age and applying some traceable marker. An ideal marker would label only the red cell adhere tightly and unchanged for the duration of the study prove non-toxic to the cell and the recipient lack immunogenicity after repeated injections and if radioactive provide sufficient energy for detection and imaging without measurable risk to the patient. The labelling method should be easy and inexpensive. No such label has been found. Instead a variety of labels are available depending upon the requirements of the study. For most purposes 51Cr an isotope with relatively low emission energy and a long half-life days has become the preferred red cell label. .