Presentation on theme: "Oral Rehydration Therapy. What is the main danger of diarrhoea and sickness? Dehydration Can be treated by ORT – a mixture of glucose and salts in water."— Presentation transcript:
What is the main danger of diarrhoea and sickness? Dehydration Can be treated by ORT – a mixture of glucose and salts in water Severe cases of dehydration – intravenous drip may be necessary.
What causes vomiting? Bacterial toxins that irritate the gut lining. In the intestine, the frequency of peristalsis increases and the contents move along the gut more rapidly than normal. This doesn’t give the large intestine enough time to absorb water the result is diarrhoea.
Why is vomiting and diarrhoea deadly if severe or prolonged. The body loses water quicker than it gains it – i.e. quicker than it can be replaced. How much fluid does the average person consume in a day? 2-3 litres
Where else does fluid come from in our intestines? About 8 litres of digestive juices Diarrhoea does not allow these fluids to be reabsorbed.
What is lost along with the fluids? Vital ions such as sodium, potassium and chloride – collectively known as electrolytes.
What happens if left untreated? Muscle spasms, cramps, coma and heart failure.
What is ORT? A mixture of salts and water If a person cannot keep anything down – it can be given in a drip This simple treatment has saved millions of lives in places where dysentery and cholera are very common.
GLOSSARY OF SOME OF THE TERMS USED METABOLITE Simple components into which food is broken down by digestion and which are subsequently built up into complex materials of body tissues e.g. proteins which are broken down into their component amino-acids by digestion and then metabolized back into further proteins in the body.
GLOSSARY OF SOME OF THE TERMS USED ION A single electrically charged particle into which the atoms or molecules of some substances dissociate when in solution, e.g. sodium chloride in the solid state consists of molecules containing one atom of sodium Na and one atom of chlorine Cl bound together NaCl - in solution in water the molecule splits into two ions (Na+) and (Cl-) each of which tends to be loosely bound to three or four molecules of water e.g. (H8O4Na) + and (H6O3Cl)- although for practical purposes they can be thought of as single ions Na+ and Cl- Positively charged ions e.g. Na+ are called CATIONS and Negatively charged ions e.g. Cl- are called ANIONS. The substances which show this dissociation into electrically charged ions are called ELECTROLYTES.
GLOSSARY OF SOME OF THE TERMS USED SOLUTE A dissolved substance e.g. sodium chloride (the solute) dissolved in water (the solvent) to give a solution. MOLARITY If two different substances are in a solution they are said to be equal in molarity (equimolar) if they have equal numbers of molecules per litre of solution. The mass or weight of each solute is then proportionate to their respective molecular weights.
GLOSSARY OF SOME OF THE TERMS USED HYPERNATRAEMIA The presence of an excess amount of sodium Na+ in the blood plasma (i.e. over 140 mmol/l.) NORMONATRAEMIC - is the presence of a normal level of sodium and HYPONATRAEMIC - lower than normal sodium level in the plasma. UNICEF/WHO O.R.S Sodium Chloride 3.5 grams Sodium Bicarbonate 2.5 grams Potassium Chloride 1.5 grams Glucose 20 grams to be dissolved in one litre of clean drinking water
THE PHYSIOLOGICAL PROCESS very nearly as much is reabsorbed every 24 hours - this mechanism allows the absorption into the bloodstream of soluble metabolites from digested food.
Simply giving a saline solution (water plus Na+) by mouth has no beneficial effect because the normal mechanism by which Na+ is absorbed by the healthy intestinal wall is impaired in the diarrhoeal state and if the Na+ is not absorbed neither can the water be absorbed. In fact, excess Na+ in the lumen of the intestine causes increased secretion of water and the diarrhoea worsens.
Sodium Glucose Transport If glucose (also called dextrose) is added to a saline solution a new mechanism comes into play. The glucose molecules are absorbed through the intestinal wall - unaffected by the diarrhoeal disease state - and in conjunction sodium is carried through by a co-transport coupling mechanism. This occurs in a 1:1 ratio, one molecule of glucose co- transporting one sodium ion (Na+).
It was the discovery of this mechanism of co-transport of sodium and glucose which the Lancet described as "potentially the most important medical advance this century" ( ORT is in fact the practical realization of this potential). It should be noted that glucose does not co-transport water - rather it is the now increased relative concentration of Na+ across the intestinal wall which pulls water through after it.
Several other molecules apart from glucose have a similar capacity to co-transport Na+ including: aminoacids (e.g. glycine) dipeptides tripeptides and the absorption of these molecules may occur independently of each other at different sites - thus their effect can be additive. Research is currently being carried on to utilize these additive effects to develop a multi-component "Super ORS".
Starch is metabolized in the intestine to glucose and therefore it has the same properties of enhancing sodium absorption, however it has an added advantage that it has less osmotic effect, which would act to pull water back into the lumen of the intestine.