The very hot weather Australia is currently experiencing brings a high risk of dehydration, writes Karalyn Huxhagen

The very young and older people are more prone to dehydration in hot conditions. The elderly are particularly susceptible to dehydration because of diuretic use, the practice of limiting fluid intake to avoid getting up at night to urinate, decreased thirst that occurs with age, and age-related changes in the body.

The most vulnerable are those who are confused or depressed and those with poor appetites.

The thirst sensation is less pronounced in older people, hormonal responses to hypertonicity are less effective and renal concentrating ability is diminished.

Heat-regulating responses are lessened in the elderly, and lower cardiac outputs limit their ability to maintain adequate skin flow.

The decrease in body weight during the eight decade of life is mostly related to a decreasing amount of body water, especially extracellular water. The elderly are susceptible to renal impairment due to dehydration.


Symptoms of early or mild dehydration include:

  • flushed face;
  • extreme thirst, more than normal or unable to drink;
  • dry, warm skin;
  • cannot pass urine or reduced amounts are being passed and the urine is dark yellow;
  • dizziness made worse when you are standing;
  • weakness;
  • cramping in the arms and legs;
  • crying with no or few tears;
  • sleepy or irritable;
  • unwell;
  • headaches; and
  • dry mouth, dry tongue, with thick saliva.


Symptoms of moderate to severe dehydration include:

  • low blood pressure;
  • fainting, confusion, lethargy, difficult to arouse;
  • severe muscle contractions in the arms, legs, stomach and back;
  • convulsions;
  • a bloated stomach;
  • heart failure;
  • sunken dry eyes with few or no tears;
  • skin loses its firmness and looks wrinkled;
  • lack of elasticity of the skin;
  • rapid and deep breathing – faster than normal;
  • fast, weak pulse;
  • very dry mouth membranes, blue lips; and
  • cold hands and feet.


Untreated dehydration can lead to:

  • electrolyte imbalance;
  • shock;
  • renal failure;
  • coma;
  • convulsions; and
  • death.


Causes of Dehydration

Factors that place the elderly at an increased risk for dehydration include:

  • limited access to water due to restricted mobility, poor vision and altered mental status;
  • decreased food or fluid intake;
  • administration of drugs, especially diuretics;
  • administration of high protein enteral feedings causing osmotic diuresis;
  • excess loss of water due to vomiting or diarrhoea;
  • acute illness (such as pneumonia and urinary tract infections) with increased insensible water loss from fever;
  • chronic renal disease;
  • hyperparathyroidism;
  • diabetes mellitus or diabetes insipudis; and
  • limiting fluid intake to avoid urinary incontinence.


Drugs that contribute to dehydration include:

  • antipsychotic drugs;
  • diuretics;
  • ethacrynic acid;
  • thiazide diuretics;
  • laxatives; and
  • frequent enemas.


Drugs with anticholinergic properties may cause a dry mouth, which makes chewing and eating difficult eg. Antipsychotics, antidepressants, antihistamines, opiates, antiparkinsonian drugs, antispasmodics, antidiarrhoeals and decongestant combinations.

Digoxin can further decrease thirst perception in elderly persons.



Treatment will depend on the underlying condition. Replacement should take place slowly over 72 hours.

However, the associated mental status changes may persist for two weeks or longer. Mild dehydration (volume depletion of one to two litres) can be treated by increasing your fluid intake to replace the fluids.

If there has been a loss of fluid and electrolytes as in vomiting and diarrhoea, you will have to administer an oral dehydration solution. It is important to start drinking the solutions as soon as the mild symptoms appear, do not wait until dehydration becomes severe as loss of consciousness may occur.

Oral rehydration solutions do not stop diarrhoea or vomiting, but they do replace the fluids and electrolytes more efficiently, thus they prevent or treat the dehydration and reduce the risk of severe complications.

The glucose in the solution enables the intestine to absorb the fluid and salts more efficiently. A positive fluid balance is usually achieved within eight hours of treatment.

The sports drinks are designed as energy and salt replacement in healthy, high performance athletes and these drinks can aggravate vomitting and diarrhoea and limit intestinal water absorption.

A record should be kept of input and output of fluid with volume measurements in case further treatment is needed. If the volume depletion is significant than IV fluids will need to be administered, preferably with isotonic fluid (0.9% sodium chloride), provided the patient is not hypernatraemic from dehydration.

If the patient is hypernatraemic, hypotonic fluid (0.45% sodium chloride) should be used. The administration should be such that once orthostatic hypotension and tachycardia have been resolved; the remaining deficit will be corrected over two to three days to avoid precipitating heart failure.


Clinical indicators of a return of fluid balance include

  • increase in skin elasticity and colour;
  • urine output is increasing;
  • decrease in heart rate;
  • decrease in orthostatic blood pressure; and
  • BUN and creatinine clearance levels return to normal.


The patient should be evaluated for other deficits (including hypokalaemia, hypomagnesemia, hypophospataemia, and metabolic acidosis) and treated as necessary.

While I have focused on the elderly in this article much of what I have written applies to all age groups. For the very young dehydration occurs easily as they are unable to obtain their own fluid intake nor are they able to easily communicate what they require in terms of nutrition and fluids.

Small children who do not have wet nappies, are flaccid to touch, who stop sweating and are dry to touch need urgent medical attention. There is a high risk of severe damage to their internal organs or even death.

Dehydration is usually preventable by ensuring adequate intake of nutrition and fluids.

Prevention is always preferable to treatment.


Karalyn Huxhagen is a community pharmacist and was 2010 Pharmaceutical Society of Australia Pharmacist of the Year. She has been named winner of the 2015 PSA Award for Quality Use of Medicines in Pain Management and is group facilitator of the Mackay Pain Support Group.