[Hemodilution and tissue oxygenation]

[Therapeutic erythrocytapheresis: technical aspects and clinical applications]

PURPOSE

Therapeutic erythrocytapheresis is a selective red cell-depletion aphaeresis technique.

CURRENT KNOWLEDGE AND KEY POINT

Using a discontinuous or continuous flow blood cell separator, the technique safely allows quickly and automatically collecting a large volume of red cells. The main obstacle of implementation is a poor peripheral venous access. The procedure is well-tolerated. Polycythemia vera, hereditary hemochromatosis, complicated sickle-cell-disease and retinal venous occlusion are the main clinical applications.

PROSPECT AND PROJECT

Therapeutic erythrocytapheresis is a more modern and more effective method than the classic patient-bleeding. It has to be preferred in the early treatment of patients with polycythemia vera and hereditary hemochromatosis.

[Initial shock from burns. Physiopathology: therapeutic principles]

Widespread destruction of the skin induces a large necrotic mass and a break of the skin barrier. It also leads to an intense inflammatory reaction. This activates keratinocytes, endothelial cells and neutrophils. Certain mediators (e.g. endothelin, histamine, bradykinin, serotonin, catecholamines, vasopressin, prostaglandins, cytokines and nitrogen monoxide) are thus released in large quantities and act both at the site of the burns and at a distance. The abnormally high level of albumin in the capillary wall and the increased capacity of absorption of the interstitial areas around the burns are the main abnormalities observed. This results in a hypovolemia associated with a hemoconcentration, hyponatremia, hypoalbuminemia, systemic vasoconstriction and myocardial malfunction, which is difficult to evidence. During the initial phase, the major risk is the appearance of hypovolemic shock, which is rapidly irreversible if early treatment is not administered. Vascular filling with iso- or hyper-osmolar sodium crystalloids, associated with buffer solutions, is the first line. There is still debate regarding the best moment at which to give albumin. A hyperkinetic shock may occur after several hours and despite the filling. The symptoms are tachycardia, increased heart rate and a dramatic decrease in systemic vascular resistance. This may lead to metabolic acidosis and multi-organ failure. Study of the hemodynamic profile of the patient allows the rational use of pressor amines and haemodialysis.

[Do corticotherapy and hemodilution decrease postoperative inflammation after maxillofacial surgery?]

OBJECTIVE

To assess the efficiency of corticosteroids and preoperative acute normovolaemic haemodilution (PANHD) in reducing postoperative inflammation after maxillofacial surgery.

STUDY DESIGN

Randomized clinical trial.

PATIENTS

Thirty-two patients scheduled to undergo maxillary osteotomy for facial dysmorphia were randomized into four groups of eight (PANHD or not; corticosteroids or not).

METHODS

PANHD decreased haematocrit to 30%. In the corticosteroid groups, methylprednisolone 1.5 mg.kg-1 was given intravenously at the beginning of surgery (after PANHD in haemodiluted group), and after surgery, 1.5 mg.kg-1 iv daily for three days. Postoperative inflammation was assessed with an X-Ray technique (radiotelemetry) providing data on tissue thickness (extent of facial oedema), and by measurement of plasma concentrations of four acute phase proteins during the first postoperative week.

RESULTS

No change in facial oedema and in acute phase proteins occurred with PANHD. Corticosteroids decreased postoperative oedema and acute phase proteins.

CONCLUSION

Corticosteroids decrease postoperative inflammation after maxillofacial surgery but not PANHD.

Acute normovolaemic haemodilution does not reduce the inflammatory process induced by facial surgery

The place of preoperative acute normovolaemic haemodilution (haematocrit = 28%-32%) in reducing postoperative inflammation was evaluated after facial surgery. Thirty-two patients scheduled for mandibular osteotomy were randomized to a nonhaemodiluted group or to a haemodiluted group. The degree of postoperative inflammation was evaluated: first by an x-ray technique (radiotelemetry) providing measurements of the tissue thickness (quantitation of facial oedema), and second by the measurement of four acute phase protein plasma concentrations during the first postoperative week. Throughout the study, no changes in facial oedema or in variation of acute phase proteins were detected after haemodilution. It is concluded that acute normovolaemic haemodilution has no effect on the intensity of facial oedema and the biological inflammation process after facial surgery.

[Original technic for preoperative hemodilution permitting deferred autologous transfusion (apropos of 106 cases)]

To carry out normovolemic haemodilution in the best security conditions we elaborate a new method of preoperative haemodilution. Collection of red cell concentrates and adequate compensation are made either in the blood bank or at the patient's bed side. There are two ways of proceeding: *manual plasmapheresis technic is used for the collection of less than 450 ml packed red cells; *collection of more than 450 ml packed red cells is carried out on a PCS Haemonetics cell separator. CPD autologous red cells concentrates prepared in that way can be stored to meet the patient's need during and after the operation. The patient is identified as donor and receiver as regards laboratory analysis and computer treatment as well. Information's transmission between blood bank hospital and clinics is secured with the same document. This method enables homologues transfusion save and completes autologous transfusion in 68% cases among 106 patients. It is to be noticed that none of the 98 haemodiluted patients suffered from thrombosis.