Faculty of Allied Health Sciences > Nutrition and Food Engineering

Water-electrolyte Imbalance

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nfe fouzia:
Electrolytes play a vital role in maintaining homeostasis within the body. They help to regulate myocardial and neurological function, fluid balance, oxygen delivery, acid-base balance and much more. Electrolyte imbalances can develop by the following mechanisms: excessive ingestion; diminished elimination of an electrolyte; diminished ingestion or excessive elimination of an electrolyte. The most common cause of electrolyte disturbances is renal failure.

The most serious electrolyte disturbances involve abnormalities in the levels of sodium, potassium, and/or calcium. Other electrolyte imbalances are less common, and often occur in conjunction with major electrolyte changes. Chronic laxative abuse or severe diarrhoea or vomiting (Gastroenteritis) can lead to electrolyte disturbances along with dehydration. People suffering from bulimia or anorexia nervosa are at especially high risk for an electrolyte imbalance.

nfe fouzia:
Electrolytes are important because they are what cells (especially nerve, heart, muscle) use to maintain voltages across their cell membranes and to carry electrical impulses (nerve impulses, muscle contractions) across themselves and to other cells. Kidneys work to keep the electrolyte concentrations in blood constant despite changes in your body. For example, during heavy exercise, electrolytes are lost in sweat, particularly sodium and potassium. These electrolytes must be replaced to keep the electrolyte concentrations of the body fluids constant.

nfe fouzia:
We also need to learn about the following terms a little---

- Acidosis
- Alkalosis
- Dehydration
- Malnutrition
- Starvation

nfe fouzia:
Acidosis is an increased acidity in the blood and other body tissue (i.e. an increased hydrogen ion concentration). If not further qualified, it usually refers to acidity of the blood plasma.

Acidosis is said to occur when arterial pH falls below 7.35 (except in the fetus - see below), while its counterpart (alkalosis) occurs at a pH over 7.45. Arterial blood gas analysis and other tests are required to separate the main causes.

The term acidemia describes the state of low blood pH, while acidosis is used to describe the processes leading to these states. Nevertheless, the terms are sometimes used interchangeably. The distinction may be relevant where a patient has factors causing both acidosis and alkalosis, wherein the relative severity of both determines whether the result is a high or a low pH.

The rate of cellular metabolic activity affects and, at the same time, is affected by the pH of the body fluids. In mammals, the normal pH of arterial blood lies between 7.35 and 7.50 depending on the species (e.g. healthy human-arterial blood pH varies between 7.35 and 7.45). Blood pH values compatible with life in mammals are limited to a pH range between 6.8 and 7.8. Changes in the pH of arterial blood (and therefore the extracellular fluid) outside this range result in irreversible cell damage.

nfe fouzia:
Alkalosis refers to a condition reducing hydrogen ion concentration of arterial blood plasma (alkalemia). Generally, alkalosis is said to occur when pH of the blood exceeds 7.45. The opposite condition is acidosis (when pH falls below 7.35).

Causes

The main cause of respiratory alkalosis is hyperventilation, resulting in a loss of carbon dioxide. Compensatory mechanisms for this would include increased dissociation of the carbonic acid buffering intermediate into hydrogen ions, and the related excretion of bicarbonate, both of which lower blood pH.

Metabolic alkalosis can be caused by prolonged vomiting, resulting in a loss of hydrochloric acid with the stomach content. Severe dehydration, and the consumption of alkali are other causes. It can also be caused by administration of diuretics and endocrine disorders such as Cushing's syndrome. Compensatory mechanism for metabolic alkalosis involve slowed breathing by the lungs to increase serum carbon dioxide, a condition leaning toward respiratory acidosis. As respiratory acidosis often accompanies the compensation for metabolic alkalosis, and viceversa, a delicate balance is created between these two conditions.

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