Intravenous fluid therapy

Published on 01/03/2015 by admin

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Last modified 01/03/2015

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Intravenous fluid therapy

Intravenous (IV) fluid therapy is an integral part of clinical practice in hospitals. Every hospital doctor should be familiar with the principles underlying the appropriate administration of intravenous fluids. Each time fluids are prescribed, the following questions should be addressed:

Does this patient need IV fluids?

Which fluids should be given?

How much fluid should be given?

How quickly should the fluids be given?

How should the fluid therapy be monitored?

Does this patient need IV fluids?

The easiest and best way to give fluids is orally. The use of oral glucose and salt solutions may be life-saving in infective diarrhoea. However, patients may be unable to take fluids orally. Often the reason for this is self-evident, e.g. because the patient is comatose, or has undergone major surgery, or is vomiting. Sometimes the decision is taken to give fluids intravenously even if the patient is able to tolerate oral fluids. This can be because there is clinical evidence of fluid depletion, or biochemical evidence of electrolyte disturbance, that is felt to be severe enough to require rapid correction (more rapid than could easily be achieved orally).

Which IV fluids should be given?

The list of intravenous fluids that is available for prescription in many hospital formularies is long and potentially bewildering. However, with a few exceptions, many of these fluids are variations on the three basic types of fluid shown in Figure 13.1.

Fig 13.1 The three types of fluid usually used in intravenous fluid therapy are shown here with the different contributions they make to the body fluid compartments.

Plasma, whole blood, or plasma expanders. These replace deficits in the vascular compartment only. They are indicated where there is a reduction in the blood volume due to blood loss from whatever cause. Such solutions are sometimes referred to as ‘colloids’ to distinguish them from ‘crystalloids’. Colloidal particles in solution cannot pass through the (semipermeable) capillary membrane, in contrast with crystalloid particles like sodium and chloride ions, which can. This is why they are confined to the vascular compartment, whereas sodium chloride (‘saline’) solutions are distributed throughout the entire ECF.

Isotonic sodium chloride (0.9% NaCl). It is called isotonic because its effective osmolality, or tonicity, is similar to that of the ECF. Once it is administered it is confined to the ECF and is indicated where there is a reduced ECF volume, as, for example, in sodium depletion.

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