Dehydration — Recognition and Field Treatment

Dehydration occurs when the body loses more fluid than it takes in. In emergency situations, the risk of dehydration is significantly elevated — physical exertion during evacuation, illness causing fluid loss, reduced access to clean water, and heat exposure all accelerate dehydration. Understanding how to recognise it, how to treat it, and critically, how to make an effective oral rehydration solution from basic supplies, can be lifesaving.

Dehydration kills. In extreme heat, severe illness, or prolonged water deprivation, it kills within hours. In moderate form, it impairs decision-making, physical performance, and immune function — all of which are critical in an emergency scenario.

How the Body Loses Water

Route	Normal Loss	Increased By
Urine	1–1.5L/day	Alcohol, caffeine, cold weather
Breathing (respiration)	0.3–0.5L/day	Exercise, dry air, altitude
Sweating	0.5–1L/day baseline	Heat, exercise, fever
Faeces	0.1–0.2L/day	Diarrhoea (dramatically increases loss)

In hot conditions with physical exertion, sweat loss alone can reach 1–2L/hour. A person carrying a heavy pack through summer heat can require 6–8L of water per day to remain adequately hydrated.

Signs of Dehydration — Severity Classification

Severity	% Body Weight Loss	Signs
Mild	1–2%	Thirst; slightly reduced urine output; urine darker than usual
Moderate	3–5%	Dry mouth; headache; dizziness; reduced urine (concentrated, dark)
Severe	6–9%	Very dark or no urine; rapid heartbeat; confusion; dry skin with poor elasticity
Critical	> 10%	Extreme confusion or unconsciousness; rapid weak pulse; cannot take oral fluids

Urine colour is a reliable field indicator:

Urine Colour	Hydration Status
Pale yellow (like lemonade)	Well hydrated
Yellow (like apple juice)	Mildly dehydrated
Dark yellow / amber	Moderately dehydrated
Brown	Severely dehydrated; seek help
No urine for > 8 hours	Critical dehydration

⚠️ Thirst is an unreliable indicator of hydration status. By the time you feel thirsty, you are already mildly dehydrated. In elderly people, the thirst mechanism is often impaired — they may not feel thirst even when significantly dehydrated. This is why scheduled fluid intake (not waiting to feel thirsty) is important in heat and during exertion.

Treating Mild to Moderate Dehydration

For conscious adults who can drink:

1. Drink cool water at a rate of approximately 150–200ml every 10–15 minutes — sipping steadily rather than drinking large volumes all at once (large volumes may cause nausea and vomiting).
2. Replace electrolytes — pure water is not sufficient for significant dehydration because electrolytes (sodium, potassium) are lost with sweat and must be replaced for proper cellular function.
3. Rest — reduce the cause of fluid loss by stopping exertion; find shade.

Do not: drink very cold water rapidly — this can cause stomach cramps; and do not drink only water without electrolytes if you have been sweating heavily — hyponatraemia (dangerously low sodium) can result.

Oral Rehydration Solution (ORS)

Oral rehydration solution is the standard treatment for dehydration — it is the treatment recommended by the WHO for diarrhoea-related dehydration globally and is equally effective for dehydration from any cause. Commercial ORS sachets (Dioralyte in UK) should be in every emergency kit.

If You Have No Commercial ORS

Improvised ORS from basic supplies:

WHO Standard ORS (1 litre):

• 1 litre of clean water (boiled and cooled)
• 6 level teaspoons of sugar (glucose preferred but sucrose works)
• ½ level teaspoon of salt (sodium chloride)
• Optional: a small amount of fruit juice for potassium and flavour

Mix until dissolved. This solution provides the right balance of sodium and glucose to maximise intestinal absorption of water.

Commercial alternatives: Sports drinks (Lucozade, Gatorade, Powerade) provide electrolytes and can be used in mild to moderate dehydration — they contain more sugar than optimal ORS but are effective. Dilute 50/50 with water in hot weather.

ORS Dose

Age Group	Dose for Mild-Moderate Dehydration
Adult	750–1000ml per hour for 3–4 hours; then maintenance
Child 2–10	500ml per hour for 2 hours; then maintenance
Infant	100–200ml per kg over 3–4 hours; medical supervision preferred

ORS for diarrhoea: Give 150–200ml after every loose stool or vomiting episode in addition to normal intake.

Treating Severe Dehydration

Severe dehydration with confusion, inability to drink, or shock requires intravenous fluids — this is beyond field capability.

Field management while seeking emergency care:

1. If the person can swallow: continue small sips of ORS.
2. Do not force fluids if the person is vomiting — this causes more electrolyte loss.
3. Recovery position if consciousness is impaired.
4. Keep cool — reduce metabolic demand; reduce heat-related fluid loss.
5. Call 999 — severe dehydration with altered consciousness is a medical emergency.

Special Circumstances

Situation	Fluid Need
Fever	Add 10% per degree above 37.5°C
Diarrhoea and vomiting	Replace all lost volume with ORS
Heat and physical exertion	Up to 1L/hour during heavy work in heat
Altitude	Increased insensible losses; 3–4L/day at altitude
Pregnancy	Baseline need increased; dehydration triggers contractions
Elderly	Impaired thirst; actively schedule fluid intake

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Quick Reference

Severity	Signs	Treatment
Mild	Thirst; darker urine	Water + electrolytes; rest
Moderate	Headache; dizziness; dark urine	ORS — 750–1000ml over 2–4 hours
Severe	Confusion; no urine; rapid pulse	Small ORS sips; recovery position; call 999
ORS recipe	1L water + 6 tsp sugar + ½ tsp salt	Dissolve fully; offer in sips
Prevention	Schedule fluid intake; don't wait for thirst	Pale yellow urine = adequate
Red flag	No urine for 8+ hours; confusion	Emergency medical care