A patient presents with sudden onset severe watery diarrhoea described as 'rice-water stools,' rapid dehydration, and no fever. Stool dark-field microscopy shows 'shooting star motility.' The MOST appropriate electrolyte replacement solution for adults with severe cholera is:

• A Ringer's lactate solution IV at 30 mL/kg over 30 minutes then 70 mL/kg over 2.5 hours ✓
• B Normal saline 0.9% IV at 20 mL/kg bolus, repeated as needed
• C ORS alone (low-osmolarity WHO formula 245 mOsm/L) — IV fluids not required
• D 5% dextrose in 0.45% saline at 150 mL/hour

Explanation

WHO Plan C for severe cholera (dehydration >10%) uses Ringer's lactate (Hartmann's solution) as the preferred IV fluid — 30 mL/kg over 30 minutes then 70 mL/kg over 2.5 hours (adults). Ringer's lactate more closely approximates the electrolyte composition of cholera stool (sodium, potassium, bicarbonate losses). Normal saline does not replace bicarbonate and can worsen metabolic acidosis. ORS is used for moderate dehydration once vomiting is controlled. Dextrose solutions do not provide the necessary sodium. Antibiotics (doxycycline or azithromycin) are used adjunctively to reduce stool volume.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

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Written and medically reviewed by the StethoPrep medical team.