Keep close watch on volume depletion and here’s why

January 17, 2019

The term “volume depletion” may not ring a bell to most of us. Sharing a few similar symptoms with dehydration, they seem to be identical, but not quite. Volume depletion refers to the reduction of the volume of water in the blood vessels of our body, much more likely than dehydration, which is the loss of water from both the blood vessels and the body’s cells.

It is known that adequate hydration is required for the body to function normally. Water maintains our body temperature and lubricates our joints. Our body’s cells rely on water as does the various bodily systems. Thus, severe cases of volume depletion can lead to shock and collapse. Without resuscitation with fluids, the consequences may be devastating.

The total water volume of a regular person – water in both the blood vessels and the body’s cells – is remarkably constant, given the large variation in how much water is taken in and lost each day. The daily variation of water intake is regulated by the kidney; this in turn alters your urine output.

When you drink large volumes of fluid, your body can afford to get rid of increased amounts of dilute urine. But when you drink a minimal amount of fluid, your urine is instead concentrated, and you pass only a small volume. Other small losses of water can be through sweat, lung activity or through stools.

Fluid is lost as in cases of diarrhea, vomiting or bleeding, and you can develop the symptoms of volume depletion including:

Thirst/dry mouth
Dizziness – a consequence of low blood pressure and volume loss
Confusion – a consequence of inadequate oxygen to the brain
Skin turgor – reduced, as it takes longer for skin to bounce back when pinched

It is also noted that volume depletion, causing low blood pressure and an increased heart rate – in an attempt to maintain blood pressure – also causes reduced weight, as fluid makes up two-thirds of body weight. So, a loss of 1litre of fluid will read as a drop in 1 kilogram on the scales.

Blood testing will often reveal a degree of kidney impairment, because the kidneys require a large blood flow to work normally. In cases of volume depletion and reduction in blood pressure, blood flow to the kidneys is compromised, and they go into “shock”. This is mostly reversible through fluid and blood pressure restoration, though doctors will still order a combination of blood and urine tests for an accurate volume depletion diagnosis.

Certain groups are more susceptible to volume depletion:

The elderly – reduced total body water volume; reduced sensation of thirst; impacted ability to concentrate urine from various health problems due to age
Babies – require more fluids, but are unable to articulate when thirsty
Active patients – having to take medications that promote water loss – diuretics, etc.
People with impaired thirst mechanisms – brain injuries, etc.

These groups must be aware of the increased risk, recognize symptoms if affected, and seek prompt treatment, including going to hospital if necessary.

Dehydration is distinct from volume depletion, but has many overlapping symptoms, such as thirst, low blood pressure, and confusion. Dehydration can happen with prolonged blood sugar levels, as in the case of a diabetic. Water is pulled from within cellular compartments to counter the high sugar levels in the blood. You will also pass more urine. Since there is greater loss of fluid, monitoring blood sugar levels is important, and perhaps medical attention is required to prevent dehydration.

Volume depletion can occur anytime of the year, and especially in summer; it is important to keep fluids up, and to know symptoms in case of emergencies. Talk to your doctor if medications need adjusting, and be mindful of your family, friends and neighbours.

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