After initial use of plasma expanders, major acute blood loss requires rapid blood transfusion. While it is vital to restore blood volume and oxygen-carrying capacity, rapid transfusion may produce problems over and above those which can occur with any administration of blood products (such as group incomparability and risk of infection).
Urgent provision by the transfusion laboratory and quick checking of multiple units of blood in an emergency inevitably enhances the chances of omission or error. However urgent the situation, unless one has resorted to giving uncross-matched or universal donor blood, safety standards must be maintained, if necessary by one member of staff dedicated to the checking and recording of blood units.
Other unwanted side effects result from the differences between fresh and stored blood. Some occur as a result of changes with time, and some relate to additives or extraction of plasma components. Blood is stored at 40C and rapid transfusion has caused arrhythmias and worsened intraoperative hypothermia. Newer warming devices are able to raise the temperature satisfactorily even at very fast transfusion rates, but may require considerable pressure to force the blood through tortuous or narrow tubes. Cellular metabolism, membrane ion pump failure and haemolysis during storage lead to hypokalaemia and acidaemia with rapid transfusion, compounding the effects of reperfusing ischaemic areas and again may impair cardiac performance.
Anticoagulant (usually citrate to chelate calcium) and early loss of clotting factors and active platelets result in dilutional coagulopathy during massive transfusion. Ideally clotting should be monitored (such as by thromboelastography in theatre, or in the laboratory), and specific defects identified and treated. However, the situation is often too fraught and rapidly changing, and it may be necessary to administer fresh frozen plasma and/or platelets on an empirical basis (per 6—10 units of blood transfused). Calcium is usually maintained by mobilisation from bone, except in severe circulatory failure; however, it too should be measured or empirical administration considered if clotting appears clinically inadequate.
Parenteral fluid therapy
The solutions mainly in use are given below and summarised in Table 4.3.
• Plasma, albumin 4.5 per cent;
• dextrose 5 per cent is an isotonic solution that supplies calories without electrolytes. It is useful in the postoperative period when sodium excretion is reduced. It is also valuable when the salt requirements of a patient needing much fluid have been satisfied on a particular day. Prolonged administration of 5 per cent dextrose solution alone is liable to result in hyponatraemia, and may cause thrombosis of the vein used;
• isotonic (0.9 per cent) saline solution is required to replace the normal sodium requirement (500 ml isotonic saline/day) and additional volume is required when a large amount of sodium has been lost by vomiting, or by gastric, duodenal or intestinal aspiration, or through an alimentary fistula. Possibly, on occasions, excessive sweating may justify its use;
• dextrose 4.3 per cent with saline 0.18 per cent (one-fifth isotonic saline) — this solution is isotonic. Usually it is referred to as dextrose—saline. It must not be confused with S per cent dextrose in saline, which is hypertonic;
• Ringer’s lactate solution contains sodium, potassium and chloride in almost the same concentrations as they are in the plasma. It also contains some calcium and some lactate. This solution can be used in hypovolaemic shock while awaiting blood. It is also suitable for replacing lost intestinal secretions.
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