Discuss Oral Rehydration Therapy (ORT) & ORS — its causes, clinical features and management.

Definition

• Oral Rehydration Therapy (ORT) is the administration of fluid by mouth to prevent or correct the dehydration caused by diarrhoea.
• Oral Rehydration Solution (ORS) is the specially formulated glucose-electrolyte solution used for this purpose.
• ORT has been described as 'potentially the most important medical advance of the 20th century' for its impact on child survival.

Scientific Basis — Sodium-glucose Co-transport

• The intestinal mucosa has a sodium-glucose co-transporter (SGLT-1) that absorbs sodium and glucose together in a 1:1 ratio, dragging water with them.
• This transporter remains intact even in secretory diarrhoea (e.g. Cholera), which is why oral glucose-salt solutions can rehydrate a child whose gut is actively secreting fluid.

Composition of WHO Low-osmolarity ORS (2002)

How to Give ORS

• Dissolve one packet in 1 litre of clean water; discard after 24 hours.
• Give frequently in small sips by spoon or cup (not by bottle); if the child vomits, wait 10 minutes and continue more slowly.
• Amounts follow the WHO plans — Plan A (after each stool) or Plan B (75 mL/kg over 4 hours).
• Continue breastfeeding and feeding alongside ORS.

Home-available Fluids (when ORS Packets Are Unavailable)

• Salt-and-sugar solution (a pinch of salt + a fistful/scoop of sugar in a glass of water), rice-based ORS (kanji), buttermilk, coconut water, soups.
• Cereal-based ORS (rice-ORS) is especially useful in cholera as it further reduces stool volume.

Advantages of Ort

• Simple, cheap, safe and effective; can be given at home by mothers.
• Avoids the risks, cost and skill needs of IV therapy; can be scaled up in the community.
• Physiological — corrects dehydration, acidosis and potassium loss together.

Failure / Limitations of Ort

• Contraindications: severe dehydration with shock, altered sensorium / inability to drink, ileus/abdominal distension, and very high purging (stool > 10 mL/kg/hr).
• Persistent vomiting despite slow administration → consider nasogastric ORS or IV fluids.
• These situations require initial IV therapy (Plan C), switching to ORS once the child can drink.

Evolution of ORS

• The original WHO ORS (1975) had an osmolarity of 311 mOsm/L and was designed mainly for cholera in adults.
• Because it caused a slightly high stool output in children with non-cholera diarrhoea, it was replaced in 2002 by the reduced (low)-osmolarity ORS (245 mOsm/L), which is now the universal standard for all ages.

Standard VS Low-osmolarity ORS

Use in Special Situations

• Cholera — ORS works well; a rice/cereal-based ORS further reduces stool volume.
• Severe acute malnutrition — use ReSoMal (lower sodium, higher potassium) instead of standard ORS.
• Hypernatraemic dehydration — ORS is safe and preferred, as it corrects sodium gradually.

'super ORS' (cereal / Amino-acid Based)

Polymer (rice/cereal)-based ORS provides glucose polymers that are digested gradually, adding more co-transport substrate without raising osmolarity — reducing stool output, especially in cholera.

Monitoring the Response

• Reassess hydration, urine output and ongoing stool losses regularly.
• Watch for signs of over-hydration (puffy eyelids) → pause ORS and give plain water/breast milk.
• Escalate to IV fluids if there is persistent vomiting, worsening dehydration, or the child cannot drink.

WHY Low-osmolarity ORS Is Better

• A refinement worth understanding is why the original ORS formulation was replaced by a lower-osmolarity one — and why less sodium and glucose works better.
• The original solution had an osmolarity (311 mOsm/L) roughly equal to that of plasma.
• But research showed a problem: in the upper small intestine, the luminal contents are already hypertonic during diarrhoea — and a solution of that osmolarity could, in some children, draw water into the lumen (an osmotic effect), transiently increasing the stool output and risking hypernatraemia.
• Reducing the sodium (to 75 mmol/L) and glucose (to 75 mmol/L), giving a total osmolarity of 245 mOsm/L — HYPOtonic relative to plasma — turned the gradient the right way.
• Trials showed that this reduced stool output, reduced vomiting, and reduced the need for unscheduled intravenous fluid — all by about 20–30% — without any increase in hyponatraemia.
• Hence low-osmolarity ORS is now the global standard for all causes of diarrhoea in children.
• It also contains potassium (20 mmol/L — replacing the large potassium losses of childhood diarrhoea) and citrate (correcting the metabolic acidosis).