WHAT FLUIDS TO GIVE?


See also The Clinical Use of Blood (WHO, 2001).

The initial resuscitating fluid should be either normal saline (0.9% sodium chloride) or Ringer’s lactate (also called Hartmann’s solution). These fluids are sometimes referred to as crystalloids.
Alternatives are the so-called plasma expanders or colloids. These are starch, gelatin or macro-sugar based solutes dissolved in saline with other electrolytes. They have the osmotic effect of increasing fluid shift from the extravascular into the vascular space (circulating volume), causing a rise in blood pressure. Colloids also remain in the circulation longer than electrolytes alone and are widely used in the management of hypovolaemic shock, after initial crystalloid infusion.

5% glucose (dextrose) is widely used as a maintenance fluid (a substitute for patients unable to drink water). It has no place in the restoration of circulating volume because it is rapidly distributed throughout the entire body water component of about 40 litres.

HOW MUCH FLUID?

For detailed fluid maintenance regimens, see The Clinical Use of Blood (WHO, 2001).

Opinions differ on the volume of crystalloids and colloids that are needed to correct blood and other volume losses from the blood circulation. There are no absolute rules but most authorities agree that you should give about three times the estimated circulation loss as crystalloid fluid. It is far more common for a shocked or dehydrated patient to receive too little intravenous fluid than to receive too much.

More important than any rule on the volume of replacement fluids is to observe the patient’s response to volume infusion. The signs that you have given adequate IV fluids and can slow the infusion are:

Every patient responds differently to fluid therapy. Look for the difference. Avoid fluids containing dextrose during resuscitation.

If, in an adult, the blood pressure has not responded to fluid therapy, or if blood loss is continuing after three or four litres of crystalloid, you may consider changing to a colloid infusion. These solutions usually come in 500 ml polythene containers and up to three (total 1500 ml) are usually given. Give equal volumes of colloid to the estimated blood loss.
After the above fluid therapy the patient will have been haemodiluted and, depending on any continuing blood loss, may also still be in shock. Blood transfusion is an urgent consideration at this stage.

Recent research and experience has shown that a shocked patient with severe anaemia can still have a favourable outcome, provided blood pressure and circulating volume are maintained. Opinion has therefore moved towards giving volume first as crystalloid/colloid and blood transfusion later. In the case of extreme haemodilution (Hb <4 g/dl), there is a risk of heart failure which might then result in a low blood pressure and/or pulmonary congestion with lung crepitations. Using the WHO haemoglobin colour scale will inform you when critically low haemoglobin levels exist.

Whole blood transfusion is the ultimate life saving treatment for haemorrhagic shock.

PAEDIATRIC FLUIDS

In emergency paediatric resuscitation, it is customary to give a fluid bolus of normal saline (20 ml/kg body weight and repeat if needed) as initial therapy as soon as the drip is in place. Meanwhile, make a rapid assessment of the actual deficit based on body weight, dehydration and continuing circulating volume losses. A 3 kg neonate should have 250 ml circulating blood volume, so the initial intravenous fluid load is about 20% of circulating volume.

Subsequent treatment depends on the clinical response. Recent studies of outcome in paediatric emergencies, especially where sepsis is present, have shown that generous fluid regimes giving up to 80 ml/kg in the first 12 hours, using a mixed crystalloid/colloid regimen, have given the best figures for patient survival.

Never use an adult giving set to attach a large bag of IV fluid to a child. If the fluid runs too fast, the whole bag will be given, leading to a fatal overload. Always use a burette giving set; if you do not have a burette, use a syringe to inject measured volumes.

Finally, closely watch the neck veins and the eyes, looking for signs of over- transfusion. If the child was dehydrated with reduced skin turgor, this should have been corrected by fluid therapy. If hourly urine output is needed, insert a urinary catheter or, if there is no catheter, make sure you take account of urinary bladder filling by palpating and percussing the bladder before deciding on further fluid therapy.

When giving blood for replacement in paediatric anaesthesia, the rate of flow is often less than you want, even with a pressure infuser, because the cannula is so small. In this case, a 20 ml syringe and 3-way tap is very useful to draw the blood from the giving set and push it through the small IV cannula. Be careful that all the connections are tight.

Events happen quickly in babies. Monitor closely. See also Unit 3.2: The Paediatric Patient.

SPEED OF INTRAVENOUS FLUID THERAPY

As with inadequate volumes of infusion, it is common that shocked patients receive their fluids too slowly.

A slow running drip overnight is the commonest reason for a dead patient in the morning.

A general rule for adults is to correct half the estimated deficit in about 30 minutes, then to reassess. If the patient is in shock, you should give fluids as fast as the drip will run until the blood pressure responds, then reassess the rate of flow. If the drip runs too slowly, either a pressure infuser bag may be needed to push it in, or a second drip.

If you are supervising a fast running drip, with a continuous stream through the chamber, you must stay beside the patient until the flow rate can be slowed to a rate that is more usual on a ward with normal nursing supervision. A patient on the ward with a drip will usually be given 3 litres per day as a standard regime. Assume this will happen and make it absolutely clear to ward staff if you want some other regime. Check later that your instructions are being followed.

WHAT BLOOD PRESSURE SHOULD YOU AIME FOR?
Depending on circumstances (such as if the patient is chronically dehydrated or debilitated), it may be preferable to get the blood pressure up to about 90 mmHg systolic over an hour or so before going into the operating room.

On the other hand, an actively bleeding patient (for example, from a ruptured uterus, bleeding peptic ulcer, oesophageal varices, ruptured ectopic pregnancy, severed artery or other severe trauma) should have volume replacement, ketamine anaesthesia, tracheal intubation and surgery all at the same time.

In severe haemorrhage, control of bleeding is the first priority, whatever the blood pressure or haemoglobin.

If blood is haemorrhaging from one end of a patient, there is little point in pouring fluids in at the other end in the expectation that the blood pressure will come up. The only option is to rush the patient to the operating room and get surgical haemostasis.