Volume replacement

If hyperkalaemia is not an issue, give balanced crystalloid solutions such as Hartmann’s solution or Ringer’s lactate.

If hyperkalaemia is present, then use 0.9% saline 500 ml bags and after 1.5 L consider 500 ml isotonic bicarbonate (1.26%/1.4%).

In case of haemorrhage, give blood products. Note: blood products contain a lot of potassium.

Avoid giving a patient all 0.9% saline as this causes an iatrogenic hyperchloraemic acidosis which will exacerbate hyperkalaemia.

Maintenance fluid replacement

Fluids should be calculated according to:

• Total = Oral and IV

Calculate sensible and insensible losses:

• Sensible: e.g. drains, vomiting, diarrhoea, estimated urine output
• Insensible: e.g. respiration, perspiration about 500 ml per day

Note that insensible losses are increased by tachypnoea/pyrexia.

Excess fluid can only be removed from anuric/oliguric patient by dialysis.

If a patient is euvolaemic with established acute tubular necrosis, giving more IV fluids will not make the patient pass more urine.