CHECK-UP:The capillary nail refill test can help in assessing dehydration
When my 80-year-old aunt became unwell recently we asked her GP to visit. As well as the usual heart and blood pressure tests I noticed that he examined her hands and pressed on the base of her nails. Why did he do this and what would it have told him?
It sound like he used the capillary nail refill test, a quick and painless test which can help in the assessment of dehydration and to monitor the amount of blood flow to the tissues. All tissues throughout the body require oxygen to survive and the oxygen is carried to these tissues in various parts of the body by the blood (vascular) system. This test measures how well the vascular system works in your hands and feet – the parts of your body that are farthest from the heart. The hand may be placed slightly higher than the level of the heart and gentle pressure applied to the nail bed until it turns white. This is called blanching and means that blood has been forced from the tissue. Once the tissue has blanched, pressure is removed and the doctor monitors the time it takes for blood to return to the tissue, indicated by a pink colour returning to the nail.
What’s a normal result?
If there is good blood flow to the nail bed, the usual pink colour should return in less than two seconds after pressure is removed. If blanching times are greater than two seconds, then it may indicate there is a problem. A number of illnesses such as dehydration, shock, peripheral vascular disease or hypothermia may result in a delayed capillary nail refill test. However, the test results can be highly variable between different patients, and it is therefore not used as the only method of diagnosis of an illness. It is, however, useful as supporting evidence of poor perfusion to the extremities.
She was eventually diagnosed with dehydration. Prior to this she had a tummy upset. Could this have caused the dehydration?
Dehydration means your body does not have as much water and fluids as it needs. This can be caused by not drinking enough fluids, losing too much fluid, or a combination of both. Vomiting and diarrhoea are common causes. Babies, young children, older people and those with other illnesses are susceptible to developing dehydration. When severe, dehydration can be a life-threatening emergency.
