Albumin Extravasation During Surgery
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This thesis is concerned with the measurement of changes in the circulation during the period of surgery. A loss of albumin from the circulation is to be expected from observations and experiments made in the postoperative period. In this thesis a sensitive measurement technique is described which allows extravasation of albumin to be studied in patients undergoing elective surgery. Radio-isotope labelled albumin and radio-isotope labelled red cells are injected; the ratio between the two is not affected by blood loss or infusion and the ratio is therefore used as a measure of albumin extravasation. To measure the relative loss of albumin from the circulation the isotopes were administered some days prior to surgery to allow distribution and equilibration of the albumin. To measure the rate of loss of albumin (capillary permeability) the isotopes were administered at the time of surgery. The results indicate that major surgery under general anaesthesia is accompanied by a loss of albumin from the circulation, an increased capillary permeability to albumin and a fall in plasma volume that is greater than can be explained on the basis of blood loss and greater than would be expected on the basis of the reduction in red cell volume. The results suggest that patients who receive only glucose and salt solutions intravenously during major surgery will usually suffer a contraction in their blood volumes unless unacceptably large volumes of fluid are infused.
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