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.
The solutions mainly in use are given below and summarised in Table 4.3.
• 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
• 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.