*Oral Rehydration*
A simple, cheap method of Rehydrating patients
By: Kingpin
22 September 2004


Diarrhoea and dehydration is a common childhood complaint. In addition, when people perform heavy exercise without adequate access to, or usage of fluid, they run the risk of dehydration.

The classic approach to dehydration among the medical profession is to put up an IV line and replace the fluids. IV fluids can be chosen to give the right concentration of fluids, the fluids enter the circulation immediately, and there is no risk of vomiting, because the fluids bypass the gatrointestinal tract.

There are however disadvantages to the use of IV rehydration. Firstly there is the issue of expertise. Putting up a drip in a severly dehydrated person can be difficult, and this is exacerbated in children who have a lower blood volume to begin with. For people without practice in putting up lines, it can be just about impossible. Coupled to this is the risk of infection with an IV line. Good IV technique reduces the risk of an infection to the site, but poor technique or unhygienic conditions can lead to an infection that may be difficult to treat in an already unwell person.

The third, and possibly most important problem is cost. IV lines are not cheap. Particularly when hospitals and medical suppliers are non-operational or out of stock, IV’s are a scarce resource, and can only be used for life-or-death situations.

If an isolated retreat community has a limited stock of IV tubes and bags, and no means of resupply, then the use of this equipment must be restricted to cases where there is no other option.

Oral rehydration can be a highly effective, inexpensive, and uncomplicated treatment for most forms of dehydration. It requires no specialised skills or equipment, uses ingredients that are ubiquitous and have a long shelf-life, and has a very low risk of complications. This article will discuss the circumstances of use and preparation of Oral Rehydration Solution.



Circumstance of Use

Oral Rehydration Solution (ORS) can be used to treat most forms of dehydration and hypovolemia.

It relies on the Gastro-Intestinal Tract (GIT) for absorption, and so is not helpful in conditions where the GIT is non-functional for some reason. In these circumstances IV rehydration may be the only option.

For the majority of conditions where fluid loss occurs, such as diarrhoea, vomiting, excessive sweating/ inadequate fluid intake, or blood loss, Oral Rehydration Therapy (ORT) can replenish the body’s fluids adequately.


Blood Loss

While ORS is not a substitute for blood or other IV blood replacement media, it can assist in replacing lost volume. When a person loses a large volume of blood, there are two separate factors that cause symptoms.

Firstly, the loss of red blood corpuscles (RBCs) reduces the oxygen carrying capacity of blood. Oxygen is held in the RBC’s, and the reduction in the quantity of these cells reduces the ability of the circulatory system to transport oxygen to the cells. The body stores a small quantity of RBC’s in the spleen, and in conditions of blood loss this reserve is released into the general circulation.

Secondly, the loss of fluid volume leads to a reduction in the volume of blood circulating around the body. This reduces the blood pressure, and makes it more difficult for the heart to circulate an adequate volume of blood to the tissues.


Other Fluid Loss

In dehydration other than that caused by blood loss, the issue is generally the loss of water. This leaves to a lowering of the volume of the blood, without lowering the number of RBC’s in the blood. This causes the blood to become more viscous. As a result the heart has to work harder, to pump a smaller quantity of more viscous blood around the body.

The objective therefore of rehydration therapy is to restore this lost volume.

In blood loss this will increase the available blood volume, but not the oxygen carrying capacity. This can still help if it stabilises the blood pressure, and makes it easier for the heart to transport the remaining RBC’s around the body.

In other forms of dehydration, the replacement of fluid volume will reverse the major symptoms of dehydration, and enable the person to recover.


Why Not Just Water?

Plain old water is a good agent to prevent dehydration. Dehydration is the loss of water, so in order to reverse this, water should be added.

The complication of this is that water is not actively absorbed from the gut. Water flows by osmosis into the cells lining the gut, and this can take a while.

If someone is dehydrated, we want to restore the lost fluids as soon as possible.

IV fluids do this by placing the fluid directly into the circulation, but unless dehydration is severe, ORS will also do the job at a fraction of the cost.

ORS is composed of Water, Salt and Sugar. For those who are more particular: Water, Sodium Chloride, and Sucrose.

The reasons for this composition are as follows:

Sodium is rapidly absorbed from the gut. The sodium in the solution quickly enters the cells of the gut, because there is a lower concentration of Sodium in the cells.

Glucose (which is what Sucrose is broken down to) is linked to Sodium absorption. When the sodium flows across into the cell, it pulls the glucose molecules with it.

This means that having the glucose in solution with the sodium will result in the glucose being pulled faster into the cells than it would if there was just plain glucose. The glucose in the cells is osmotically active and likes to have water around it. As a result it pulls the water into the cell far more rapidly than it would enter by itself.

This is why ORS is superior to Sugar-water or plain old water for rehydration. The salt speeds up the absorption of glucose, and the glucose speeds up the absorption of the water. This puts a lot more water into the body quickly.


The other important aspect to note with ORS is that it is optimised for putting water back into the body. In acute dehydration, water is the most important constituent to be lost, and replacing it will resolve the patient’s symptoms.

In contrast, chronic diarrhoea or vomiting, or other forms of fluid loss, will result in electrolytes such as potassium being depleted. This can lead to serious symptoms, and in order to prevent this occurring, and to find the cause of the chronic illness, a medical professional should be consulted.

The vast majority of short term diarrhoea or vomiting episodes resolve themselves rapidly, needing only supportive ORS. Diarrhoea that lasts for more than a week, or has other complicating symptoms, should be referred for treatment


A brief word about sports drinks:

Many sports drinks advertise themselves as being ‘isotonic’. This means that they have the same concentration as body fluids under normal circumstances.

In many cases this is an out-and-out lie. The concentration of a number of commercial solutions is far higher than the normal body osmolarity of 290-300 mosmol.

The other fact to be borne in mind is that the other solutions that do have the right concentration have very little salt.

This is because salt interferes with the taste, and sweet solutions are more palatable. As any marketer knows, if they don’t like the taste, they won’t buy it, no matter how ‘good’ it is.



Making ORS

ORS is an incredibly simple recipe.

8 Teaspoons of Sugar

½ Teaspoon of Salt (or ¼ Teaspoon of salt for children/babies)

1 Litre of Water


Mix. Drink.

ORS can also be made up according to whatever units, bottle size, or quantity is convenient for you.

As you can see it is cheap and uses ingredients that are almost always available.

Give it a taste. You will see why most commercial soft-drinks use minimal salt. Salt does not make it taste good. However, just by adding a little salt, you greatly increase the speed with which the solution in absorbed.


Giving ORS


ORS is very commonly recommended for children with diarrhoea, and pregnant women with morning sickness. It is also appropriate for other people with moderate dehydration.

Severe rehydration is generally treated with IV fluids, because of the need to get fluids in rapidly.

If you have IV fluids available, and you are worried about the patient, then use the IV. If however the patient is not severely dehydrated, ORS is an excellent first step, and IV fluids can be added later if the patient’s condition doesn’t stabilise.


ORS should be given when babies or small children develop diarrhoea. It is given in addition to normal feeding, as the child still needs the milk or food for normal body growth. ORS helps to replace the increased fluid loss due to the diarrhoea.

ORS can be given in whatever quantities the child is willing to take. It can also be given to a baby in a bottle. Care should be taken to ensure that the bottle is clean and the water boiled or treated, as diarrhoea is often caused by contaminated foods or bottles.

ORS is safe if given in excess, except in the case of heart failure or kidney failure, as any excess fluids given will simply be urinated out. As a result it is generally best to give as much as the child will take, especially if you do not have a higher level of medical care available to treat the child.

ORS should be given after each bout of diarrhoea, as this will assist in replacing the lost fluids. Anti-diarrhoea medication should be avoided in the majority of cases of diarrhoea where there is no blood in the stool, as diarrhoea is often the body’s way of eliminating irritants or getting rid of contaminated food. If you block off this mechanism, you can make the patient worse. Of course there are circumstances where diarrhoea should be stopped, but it is seldom necessary to treat a simple short case of diarrhoea with medication.


Adults are more able to regulate their own intake of ORS. In most cases, dehydration can be avoided simply by matching fluid loss with fluid intake. If however dehydration does occur, ORS can be useful to rapidly rehydrate them, and they can then be maintained by drinking more palatable substances such as juices.

ORS can be made up in litre quantities, and drunk by the patient whenever they are able. A patient who is severely dehydrated enough to be only partially conscious should receive IV fluids, as they are both in severe need of fluids, and may be unable to control their own airway, and hence may breathe in ORS by mistake.





Oral Rehydration Therapy, while not having the glamour associated with IV drips and complex medical interventions, can prevent many of the complications of dehydration secondary to diarrhoea, vomiting, or other sources of fluid loss.

The Oral Rehydration Solution is a simple and inexpensive solution, consisting of 8 teaspoons of sugar, half a teaspoon of salt, and a litre of water, that can be used to rapidly rehydrate a patient.

ORS is especially effective because it contains both salt and sugar, which contribute to its rapid absorption by the gut.

ORS is not a universal cure-all, and in cases of prolonged fluid loss, such as chronic diarrhoea, should be referred to medical care, both to determine the cause, and to replace lost electrolytes.

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