There may be clues in the history. E.g.:
- Look around the bed for clues. E.g. fluid restriction signs, catheter bag, nutritional supplements
- Look at the face for sunken orbits – this is a sign of moderate to severe dehydration
- Look inside the mouth – look at the tongue and mucous membranes for signs of moisture. Dehydration will cause these surfaces to appear dry
Check the skin turgor. Gently pinch a fold of skin on the forearm, hold it for a few seconds, then let go.
- Normal hydration – the skin will promptly return to its original position
- Dehydration – the skin will take longer to return to its original position
- This sign is unreliable in elderly patients – as these people tend to have lost their natural skin elasticity anyway
- Capillary refill – raise the patient’s hand to the level of the heart, then press down hard on the nail for 5 seconds. Note the time taken for the normal pink colour to refill. If this takes longer than 2 seconds it indicates poor peripheral blood supply – there could be many causes for this, one of which could be low blood volume
- Pulse – there may be a compensatory tachycardia in both dehydration and fluid overload
- Blood pressure – check both lying and standing BP. Low standing BP indicates dehydration
- JVP – check the height of the JVP. This is one of the most sensitive ways of judging intravascular volume. JVP will be low in dehydration and high in fluid overload. Fluid overload also commonly causes basal crepitations as a result of pulmonary oedema – so if you suspect fluid overload you should listen to the lung bases.
- Oedema – check both sacral and ankle for signs of fluid overload. Common causes of this are heart failure, hypoalbuminaemia (liver failure), pericarditis.
- Urine specific gravity is a slightly more accurate way of measuring hydration. It basically measures the concentration of solutes in the urine. The greater the concentration, the greater the degree of dehydration.
- Remember – when looking at urine sample, you want an MSU – always discard the first part of the stream