Assessing hydration
Ill patients may be dehydrated, and this is an important condition to recognise since it requires urgent correction.
Dehydration may be recognised as follows:
- By subjective complaints of thirst, dry mouth and reduced urine flow. Ask your patient if necessary.
- By evidence of reduced urine output. If urine volumes have been charted by nursing staff, inspect these.
- By evidence of reduced saliva and sweat. The inside of the mouth may appear dry, the tongue furred and the axilla dry rather than moist and sweaty.
By evidence of intravascular volume depletion. There are two signs of this:
- Tachycardia
- Postural drop in blood pressure. This is described below:
By signs of reduced skin turgor. The eyes may be sunken. When a fold of skin is pinched up, it feels thin, dry and inelastic, and does not collapse back to its normal shape immediately when released.
In severe dehydration, the eyes may appear sunken in their sockets.
Assessing a postural drop in blood pressure
(Measurement of blood pressure is described in the programme Examination of the cardiovascular system and not in detail here.)
To detect a postural drop, the blood pressure is carefully measured with the patient lying flat. The patient is then placed in a fully sitting position and the pressure immediately measured again.
If hypovolaemic, systolic blood pressure cannot be maintained and there is a drop in systolic pressure in excess of 10 mmHg.
Measuring the temperature
When appropriate, measure the temperature. Clean a thermometer with an alcohol wipe. Shake down the mercury to below 35?C, place the thermometer under the tongue. Wait 2 minutes, then remove and read.
