Acute diarrhoea and dehydration

Manage now— do this, in order

• Severe dehydration or shock is treated intravenously, immediately: 100 mL/kg of balanced crystalloid over 3 hours, given as 30 mL/kg over the first 30 minutes then 70 mL/kg over the next 2½ hours; in infants under 12 months the same 100 mL/kg goes in more slowly — 30 mL/kg over 1 hour, then 70 mL/kg over 5 hours. Ringer's lactate (Hartmann's) is the fluid of choice, because lactate is metabolised to bicarbonate. Reassess the radial pulse at 15 and 30 minutes, and if it remains weak or absent at 30 minutes, repeat the 30 mL/kg bolus. In a frankly shocked child give 20 mL/kg as a rapid bolus, reassess, and repeat once.Doctor / Nurse
• Begin oral rehydration solution alongside the infusion as soon as the patient can drink safely — running both is correct, because the gut absorbs glucose-coupled sodium even while secreting. Never rehydrate a drowsy or persistently vomiting patient orally — aspiration of vomitus is a rapid cause of death in profuse gastroenteritis.
• Some (moderate) dehydration: ORS 75 mL/kg orally over 4 hours in small volumes given often, plus continuing losses, reassessed at 4 hours. Cannulation is not required because the patient looks unwell — if they can drink, ORS is as effective and safer. If vomiting defeats oral intake, ORS by nasogastric tube at 20 mL/kg/hour is preferable to intravenous fluid in a patient who is not shocked.
• No or mild dehydration: give ORS for ongoing losses only — about 200 mL after every diarrhoeal stool in an adult (children 50–100 mL under 2 years, 100–200 mL from 2 to 10 years) — and continue normal food, with oral fluids overall at 50–100 mL/kg over 24 hours. Prescribe ongoing losses explicitly, not as encourage fluids: the order should read maintenance fluid plus 200 mL ORS (or an equal volume of Ringer's lactate) for every subsequent diarrhoeal stool and vomit.
• Use the reduced-osmolarity WHO/UNICEF formula, 245 mOsm/L: sodium 75 mmol/L, chloride 65 mmol/L, anhydrous glucose 75 mmol/L, potassium 20 mmol/L, citrate 10 mmol/L, which outperforms the older 311 mOsm/L formula. Where sachets are unavailable, an acceptable improvised solution is ½ teaspoon (3.5 g) of salt, 1 teaspoon (2.5 g) of sodium bicarbonate, 8 teaspoons (40 g) of sugar and 8 oz of orange juice, made up to 1 litre with clean water. Water, tea and fizzy drinks alone are inadequate — they lack the sodium and glucose for cotransport.
• Assume hypokalaemia and replace it actively: a severely depleted adult may need at least 4 litres of isotonic fluid and 80 mmol of potassium in the first 24 hours. Do not add potassium to the resuscitation bolus; add it once urine flows. Peripheral administration should not exceed 40 mmol/L in the bag or 10 mmol/hour; faster replacement needs a central line and cardiac monitoring. Most of the acidosis corrects with volume alone, and sodium bicarbonate is not routinely indicated — consider it only in persisting acidaemia (pH below 7.1) despite adequate filling. Correct hypernatraemia at no more than about 10 mmol/L per 24 hours.Doctor / NurseNot available at your setup — Serum electrolytes.
• Do not starve the gut. Soft, low-fibre, low-fat, temporarily low-lactose foods — soups, rice, bananas, toast — are better tolerated; avoid caffeine and alcohol. In infants, breastfeeding must continue uninterrupted; do not dilute formula, and bowel rest has no place. Give zinc to every child under 5: 10 mg orally daily for 10–14 days under 6 months; 20 mg daily for 10–14 days from 6 months to 5 years.
• Most patients should receive no antibiotic — empirical treatment of community-acquired watery diarrhoea is not indicated and may prolong carriage. Consider antibiotics for bloody or mucoid stool; severe, prolonged (more than 5 days) or worsening illness; sepsis; extremes of age; immunocompromise; significant dehydration; or complications — and take a stool sample before the first dose. Dysentery or shigellosis: ciprofloxacin 500 mg orally twice daily for 3–5 days, or azithromycin 500 mg orally daily for 3 days, or ceftriaxone 2 g IV daily if septic (children ciprofloxacin 15 mg/kg orally twice daily, max 500 mg/dose; azithromycin 10–20 mg/kg daily, max 500 mg, for 3 days; ceftriaxone 50–80 mg/kg IV daily, max 2 g). Cholera with moderate or severe dehydration: doxycycline 300 mg orally as a single dose, or azithromycin 1 g, or ciprofloxacin 1 g single dose (children azithromycin 20 mg/kg single dose) — in cholera, fluids come first, always. *C. difficile*: fidaxomicin 200 mg orally twice daily or vancomycin 125 mg orally four times daily, both for 10 days. Amoebic dysentery: metronidazole 800 mg orally three times daily for 5–10 days, then a luminal agent (paromomycin 25–35 mg/kg/day in 3 doses for 7 days, or diloxanide furoate 500 mg three times daily for 10 days) — the luminal agent is not optional.Doctor
• Never give an antibiotic for suspected STEC or haemolytic uraemic syndrome — antibiotics may increase Shiga toxin release and precipitate HUS; and once haemoglobin and platelets are falling with a rising creatinine, established HUS reverses the fluid strategy to water restriction, discontinuation of ORS and avoidance of potassium-rich fluids and feeds. Loperamide is contraindicated in bloody diarrhoea, fever above 38.5 °C, systemic toxicity, suspected shigellosis or *C. difficile*, and suspected toxic megacolon, and antimotility drugs should not be given to children at all; where appropriate in an immunocompetent adult with watery non-bloody diarrhoea the dose is 4 mg orally initially, then 2 mg after each loose stool, maximum 16 mg in 24 hours (bismuth subsalicylate 524 mg orally four times daily is a safer adult alternative). A severely wasted or oedematous child must not receive the standard 100 mL/kg rapid rehydration — give 10 mL/kg slowly, reassessing after each aliquot, with a low-sodium ReSoMal-type solution, treating hypoglycaemia and hypothermia concurrently.