Table 7.5 Framework for managing the preoperative patient to minimise the need for allogeneic red cell transfusion
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|Time period||Manage haemoglobin level||Manage haemostasis||Blood salvage and transfusion|
|Preoperative Preadmission clinic||Assess for anaemia: diagnose and treat with haematinics and epoetin if indicated||Detect and manage haemostatic defects. Stop anti-coagulants and anti-platelet drugs if safe to do so.||Arrange for intraoperative blood salvage to be available if it is appropriate for the planned operation.|
|During surgery Surgical and anaesthetic techniques||Monitor haemoglobin, haematocrit or blood loss as a guide to red cell replacement||Keep the patient warm, as cold impairs blood clotting. Rapid haemostasis testing to guide blood component replacement. Consider use of tranexamic acid where large blood loss is expected.||Use intraoperative blood salvage|
|Post-operative Control Hb concentration, manage blood loss||SOP for post-op check of Hb when haemoglobin should be checked. Minimise blood taken for laboratory samples||SOP specifying blood transfusion thresholds and targets. SOP to trigger surgical re-exploration at specified level of blood loss. Post-operative blood salvage|
Table 7.5 provides a simple framework managing the patient waiting planned surgery so as to minimise the need for perioperative transfusion.
The following techniques have all been developed as means of reducing transfusion requirements. While some have been shown to achieve this result there is relatively little knowledge about potential risks. A recent randomised clinical trial comparing three antifibrinolytic agents has demonstrated the importance of obtaining such evidence. (See Aprotinin, below)
Preoperative autologous blood deposit (PABD)
The patient donates one or more units of his own blood which is stored till the time of surgery. May be useful for patients for whom it is very difficult to obtain compatible red cells. May reduce use of allogeneic red cells but does not reduce total red cell use when reinfused units are taken into account.
Acute normovolaemic haemodilution (ANH)
Blood is collected from the patient immediately before surgery and reinfused during or after the procedure. Evidence indicates that the procedure does not reduce transfusion requirements.
Intraoperative blood salvage
Blood lost during surgery is collected, washed to remove plasma and debris, and reinfused.
Blood from wound drains is reinfused with or without washing.
Inhibitors of fibrinolysis
Those currently available are tranexamic acid and in some countries epsilon-aminocaproic acid. Aprotinin, the antifibrinolytic that had been extensively used for many years has recently been withdrawn because in a large randomised trial there was excess mortality in patients receiving this drug compared with those receiving tranexamic acid or EACA (PMID 18480196, 19050037).
Erythropoietin (EPO, epoietin)
EPO is a potent stimulator of red cell production. The drug is made by genetically engineered expression of the human erythropoetin gene. It is highly effective in the anaemia of chronic renal failure. Studies in patients with malignant disease have shown an increase in cancer recurrence and mortality. The risk of hypertension and thrombosis increases if the dose raises the patient’s Hb concentration to near normal levels. Parenteral iron preparations are often used with EPO to deliver the iron required for rapid erythropoiesis (PMID 16999756).
Do these technologies reduce the need for donor blood transfusion?
Clinical trials to answer this question have been subject to systematic reviews with meta-analysis. These methods reduce the use of allogeneic transfusion but may have other consequences. For example, predeposit autologous transfusion usually increases the total amount of red cell units transfused when both autologous and allogeneic units are counted.