Dehydration Management: ORS Formula, Assessment, and Treatment

Why Plain Water Is Not Enough

When the body loses fluid through diarrhea, vomiting, sweat, or insufficient intake, it loses electrolytes alongside water — sodium, potassium, chloride. Replacing the water without the electrolytes causes osmotic imbalance that impairs water absorption across the gut wall.

Plain water given rapidly to a severely dehydrated patient with significant diarrhea can actually worsen the situation temporarily. The gut cannot absorb water efficiently without sodium. The sodium-glucose co-transporter in the small intestine is activated by both sodium and glucose simultaneously, which is why ORS contains both.

This is the mechanism behind ORS — it is not just flavor or caloric supplementation. The glucose-sodium co-transport is a specific physiological pathway that ORS exploits.

Assessing Dehydration Severity

Dehydration is classified by the percentage of body weight lost as fluid. You cannot measure this directly, so you use clinical signs.

Mild Dehydration (Less than 5% body weight)

• Slightly dry mouth
• Thirst
• Darker yellow urine (concentrated but present)
• No other symptoms
• Mental status: normal

Moderate Dehydration (5-10% body weight)

• Dry, sticky mucous membranes (mouth, lips)
• Decreased urine output — less than 0.5ml/kg/hour (for a 70kg adult: less than 35ml/hour, or roughly 250ml/8 hours)
• Urine appears dark yellow to orange-brown
• Headache
• Tachycardia (heart rate elevated 10-20% above baseline)
• Sunken eyes
• Decreased skin turgor (see below)
• Dizziness on standing (orthostatic hypotension)

Severe Dehydration (Greater than 10% body weight)

• Very dry mucous membranes
• No urine output, or very dark minimal urine
• Rapid, weak pulse (thready)
• Low blood pressure (systolic below 90mmHg in adults)
• Sunken fontanelle in infants (soft spot on top of infant's head)
• Extreme thirst or paradoxically, no thirst (confused/obtunded)
• Mental status: confusion, lethargy, obtundation
• Cold, clammy extremities
• Shock

The Skin Turgor Test

Pinch a fold of skin on the back of the hand or the abdomen and release. Normal skin springs back immediately. Dehydrated skin holds the tent shape for a measurable time:

• Returns within 1-2 seconds: mild or no dehydration
• Returns in 2-3 seconds: moderate dehydration
• Returns slowly (>3 seconds): severe dehydration

Note: this test is less reliable in elderly patients (skin loses elasticity with age) and in very thin patients.

Urine Color Guide

| Urine Color | Interpretation | |---|---| | Pale yellow (like lemonade) | Well hydrated | | Yellow (normal) | Adequate hydration | | Dark yellow / amber | Mild to moderate dehydration | | Orange-brown | Moderate to severe dehydration | | Tea / cola color without dehydration | Possible rhabdomyolysis (muscle breakdown) or liver issue |

Oral Rehydration Solution: Formulas

WHO Low-Osmolarity ORS (Standard)

This is the internationally recommended formula, proven in clinical trials to reduce mortality from cholera and other severe diarrheal illnesses.

For 1 liter of clean water:

• 2.5g sodium chloride (approximately 1/2 teaspoon of table salt)
• 1.5g potassium chloride (available as "Nu-Salt" or "NoSalt" potassium salt substitute, 1/3 teaspoon)
• 1.5g trisodium citrate — or substitute 2.5g sodium bicarbonate (1/2 teaspoon baking soda)
• 20g glucose — or substitute 13.5g sucrose (table sugar, approximately 4 teaspoons)

Stir until fully dissolved. Use within 24 hours. Discard after 24 hours and make fresh.

Field Simplified Formula

When you do not have precise measuring:

For 1 liter of clean water:

• 1/2 teaspoon table salt (sodium)
• 6 teaspoons table sugar (glucose substrate)

This simplified formula is less precise than WHO formula but effective for most mild-moderate dehydration. The WHO formula is significantly better for severe dehydration from diarrheal illness.

Sports Drinks as Emergency ORS

Commercial sports drinks (Gatorade, Powerade) are not ideal ORS. They have lower sodium and higher sugar than recommended. In an emergency, they are better than plain water. Dilute 1:1 with water to reduce sugar concentration and improve electrolyte ratio.

Pedialyte and similar oral electrolyte solutions sold for children are closer to WHO ORS and are appropriate for adults and children.

Treatment Protocol

Mild Dehydration

• 500-1000ml ORS over the first 1-2 hours
• Continue with sips of ORS or clear fluids throughout the day
• Address the underlying cause (diarrhea management, heat reduction, rest)

Moderate Dehydration

WHO protocol: 50-100ml per kilogram of body weight over 4 hours.

Example: 70kg adult with moderate dehydration.

• 50ml × 70kg = 3,500ml minimum
• 100ml × 70kg = 7,000ml maximum
• Provide 3.5-7 liters over 4 hours

This is a significant volume. The patient will need to drink continuously. Small sips given frequently are better than large volumes that may cause vomiting. If vomiting occurs, give 1-2 teaspoons every few minutes.

After the initial rehydration phase, maintenance: 100-200ml ORS after each loose stool, 100-200ml after each vomiting episode.

Severe Dehydration

Severe dehydration requires IV fluids. If IV access is available, administer normal saline or Ringer's lactate at 30ml/kg over 30 minutes (shock protocol), then reassess.

Without IV access: push oral fluids as fast as the patient can tolerate, even if it means continuing to vomit some back. Some absorption occurs even with vomiting. Nasogastric tube (if skills and equipment are available) allows fluid delivery bypassing the vomiting reflex.

When to evacuate urgently: a dehydrated patient who cannot keep down ORS, who has altered mental status, or who shows signs of shock requires IV fluid therapy. This is beyond field capability.

Dehydration in Special Populations

Children

Children dehydrate faster than adults. Warning signs move faster. The standard assessment tools (skin turgor, mucous membranes, eyes) apply but signs appear at lower percentage losses.

Weight-based calculation: Children have different requirements. For moderate dehydration: 50-100ml/kg over 3-4 hours as for adults. Pedialyte or WHO ORS both appropriate.

Infants under 6 months: Any significant dehydration in an infant under 6 months warrants immediate medical evaluation.

Elderly

Elderly patients have decreased thirst sensation and may not feel dehydrated until moderate or severe. Kidney function is often reduced, impairing compensation. Skin turgor test is unreliable. Rely on mucous membranes, mental status, and urine output.

Heat-Induced Dehydration

In hot environments or with heavy exertion, sodium losses through sweat are significant. Replacing fluid losses with plain water can cause hyponatremia (dangerously low blood sodium) — a rare but serious condition seen in marathon runners and military personnel who drink excessive plain water.

ORS or electrolyte-supplemented water is always preferred over plain water during high-sweat dehydration.

Diarrheal Illness

Diarrhea causes dehydration through stool water and electrolyte losses. The ORS glucose-sodium co-transport continues to work even in active diarrhea — the gut absorbs more than it loses when ORS is given appropriately.

Feeding during diarrheal illness: Continue feeding. Old advice to "let the gut rest" has been proven wrong. Continuing to eat (appropriate foods) reduces illness duration and maintains gut health.

Monitoring Treatment Response

Good response:

• Urine output improving (patient needs to urinate)
• Urine color lightening
• Heart rate returning toward normal
• Mental status improving
• Skin turgor improving
• Patient feels better

Not responding:

• No urine output after 6-8 hours of ORS
• Mental status worsening
• Heart rate continues to rise
• Vomiting preventing ORS absorption

If treatment is not working after 4-6 hours, escalate to IV fluids or evacuate.