Читать книгу Understanding Anatomy and Physiology in Nursing - John Knight - Страница 30

In patients with diabetes the presence of large amounts of sugar (hyperglycaemia) results in the blood becoming too concentrated. Highly concentrated blood is referred to as being hypertonic (too concentrated) to human cells. In hypertonic solutions water will leave the cells of the body by osmosis and move into the blood, and this can lead to progressive dehydration which is a common presenting symptom in patients with undiagnosed or poorly controlled diabetes.

Dehydration caused by not drinking enough fluids or by severe vomiting or diarrhoea will similarly lead to hypertonic blood and loss of water from cells. As cells lose water, their cell membranes become loose and flaccid and may take on a crinkled appearance; this phenomenon is referred to as crenation. Progressive loss of water from the intracellular compartments can lead to tissues of the body such as the skin becoming noticeably looser, and this can be detected in patients using skin-pinch tests. As well as being a sign of shock, prolonged capillary refill time may also indicate dehydration.

Dehydration is also characterised by the mucous membranes of the body drying out which is why many people wake up with a dry mouth after drinking too much alcohol, which is known to cause dehydration by promoting diuresis (increased urination). A common cause of dehydration in hospital patients is infection with norovirus. To help develop your knowledge of this problem, attempt Activity 1.4.