Healthy Living

Pneumonia: What is Oral Rehydration Therapy?

Pneumonia: What is Oral Rehydration Therapy?

Key Takeaways

  • How oral rehydration therapy works
  • Benefits of oral rehydration therapy
  • Precautions

Pneumonia: What is Oral Rehydration Therapy?

Oral rehydration therapy, also known as fluid replacement, is a special type of therapy that aims to treat dehydration as a result of uncontrolled body water loss. Oral rehydration therapy involves taking water with a specific amount of dissolved salts and sugars.

Pneumonia is one of the leading fatal diseases in children around the world. Pneumonia is an infection which is accompanied by loss of body fluid as a result of diarrhea, and vomiting. Other ways pneumonia may lead to dehydration are:

  • Excessive sweating
  • Fever caused by pneumonia
  • Pneumonia causing bacteria accumulation in the stomach leading to diarrhea
  • Medications used to treat pneumonia may shift the body's osmotic balance e.g. by reduction of ADH leading to water loss through urine
  • Brain disorders caused by pneumonia can affect the osmotic hormones such as ADH and aldosterone leading to abnormal water loss
  • Lack of appetite caused by pneumonia can lead to low intake of fluids
  • Difficulty swallowing can result in low intake of fluids leading to dehydration

How does Oral Rehydration therapy work?

You may ask yourself how oral rehydration works? This is a question which can be easily answered by first considering the simple physiology of healthy intestines. Then consider the changes that take place in the event of diarrhea, or diarrhea-inducing diseases.

In healthy intestines, there is a continued exchange of water across the intestinal wall. About 20 liters of water is diffused across the intestinal wall every 24 hours. Similar volumes of water are reabsorbed in the kidney tubules every 24 hours. This mechanism of water exchange allows some soluble metabolites of digested food to be absorbed.

In a state of diarrhea, the balance of water and metabolites is disturbed and much more water is secreted than absorbed. This causes a net loss of several liters of water daily. Apart from water loss, sodium is lost as well. The body stores sodium in the interstitial fluids in the form of Na+.

Na+ concentration in the extracellular fluid must be maintained and kept at limits of close to 135-150 Mmol/L for proper body function. Normal sodium ion concentrations are controlled by the kidneys. In the case of dehydration, water is conserved by the anuria. Making sodium regulation ineffective. This means that continuous diarrhea can lead to water and sodium depletion. This is what is referred to as “dehydration”. According to scientific research, death can occur if more than 10% of body fluid is lost.

If you happen to take saline water containing Na+ orally, it would have no benefit. Since the normal Na+ absorption mechanism, by the intestinal wall, is impaired during the diarrhea state. If sodium cannot be absorbed, water will not be absorbed. As a matter of fact, excess sodium on your intestines can increase water secretion, causing the diarrhea to worsen. If you add glucose to the sodium solution, the absorption mechanism will work far better. This is because glucose particles diffuse across the intestinal wall unaffected by diarrhea. During glucose absorption, sodium is carried across by a co-transporter. Sodium and glucose absorption occurs in the ratio of 1:1. This means that one molecule of glucose co-transports one molecule of sodium ion.

This knowledge has led to the discovery of oral rehydration therapy. It should be noted that glucose does not co-transport water. It is the increase in the level of Na+ across the intestinal wall that pulls water in turn. Some other molecules can be used instead of glucose for co-transportation of Na+. They include:

  • Dipeptides
  • Amino acids like glycine
  • Tripeptides
  • Starch is converted into glucose in the intestines by enzyme action

Absorption of the above molecules sometimes occur independent of each other and at different sizes, cause the development of an addiction.

What is the composition of Oral Rehydration Therapy?

The following are factors and components to consider when preparing a perfect ORT.


Loss of sodium in stools during diarrhea can go to an extreme of 100 Mmol/L. For this reason, sodium should be a part of the rehydration formula. Sodium should be mixed with glucose in 1:1 ratio when measured in terms of molarity.


Glucose is also another component which should not be missed in the ORT. Glucose is always mixed with sodium to enable its co-transportation. Excessive glucose on ORT can cause more diarrhea since it facilitates the re-absorption of water in the intestines.


Electrolytic imbalances due to fluid loss can lead to metabolic acidosis. Acidosis is very critical when it comes to children, as it leads to the malfunctioning of the renal system. Metabolic acidosis is corrected by including bicarbonate in the ORT formula.

Electrolyte imbalance and fluid loss also cause metabolic acidosis. These effects are more critical in the case of infants, as their renal function is not fully developed and they have a large surface area ratio.


Potassium is another important ion which should not be eliminated from the ORT formula. Although most potassium is found in the body's cells, continuous and prolonged diarrhea can lead to chronic loss of potassium. When a large amount of potassium is lost, one is likely to develop lethargy, anorexia, and muscle weakness. Potassium is not involved in the sodium-glucose co-transport mechanism, instead it is absorbed passively.

Precautions to be taken during Oral Rehydration Therapy

  • There should be ORT protocols available for both patients and staff
  • Children with gastroenteritis should be given a maintenance solution to avoid dehydration. Day cares and parents are advised to always have maintenance fluid in case of diarrhea caused by pneumonia
  • Children with gastroenteritis should be treated with early oral rehydration
  • ORT instructions and maintenance solutions should be available in shops at a low cost
  • Children with severe pneumonia and dehydration should be treated with intravenous rehydration
  • Oral rehydration solutions made at home should be discouraged since they may have errors in formula creation
  • Infants who are breastfeeding should be given oral rehydration therapy with continued breastfeeding
  • Soon after vomiting one should consider re-feeding within 6-12 hours

Bottom line

Oral rehydration therapy is a type of therapy which is mainly used to treat dehydration, as a result of uncontrolled fluid loss. Oral rehydration therapy involves taking water with a specific amount of dissolved salts and sugars. With this therapy, people with dehydration attributed to pneumonia can receive the proper treatment they need.