Paediatric fluid management in the dehydrated child

(a) Classification and deficit. Weight loss is 1 kg from a usual 10 kg, a 10 per cent deficit (1000 mL). On the RCH percentage table this is severe (≥10%); NICE NG29/CG84 would call it clinical dehydration rather than shock. He is irritable with sunken eyes and fontanelle and reduced skin turgor, but blood pressure is held and he is not hypotensive, so he is not in shock. Biochemistry: hypernatraemic dehydration (sodium 158 mmol/L) with a normal-anion-gap (hyperchloraemic) metabolic acidosis; glucose 5.2 excludes DKA and hypoglycaemia.^[2]

(b) Fluid plan for the first 24 hours. No shock bolus — a 10 to 20 mL/kg isotonic bolus is for shock, and bolusing the non-shocked hypernatraemic child drops osmolality too fast. Isotonic intravenous fluid (0.9% saline, with glucose once potassium is known). RCH first 24 hours: replace a maximum of 5 per cent of body weight as deficit (500 mL) plus Holliday-Segar maintenance (1000 mL for 10 kg) = 1500 mL over 24 hours (about 62.5 mL/h), then reassess before replacing the remaining deficit. Replace ongoing stool losses millilitre for millilitre; NICE CG84 considers 5 mL/kg of ORS after each large watery stool in children at increased risk of recurrent dehydration — do not teach 10 mL/kg per stool as the NICE figure.^[3] Composition: 0.9% saline in 5% dextrose with potassium chloride 10 mmol per 500 mL (RCH 20 mmol/L) once potassium is confirmed. Do not use a free-water-deficit formula of 4 mL/kg per mmol above 145 — that number is not in the sources fetched for this topic.^[1][2]

(c) The hypernatraemic modification. NICE NG29: calculate the water deficit and replace it over 48 hours, initially with 0.9% saline; the fall in plasma sodium must not exceed 12 mmol/L in 24 hours. Recheck sodium every 4 to 6 hours for the first 24 hours and slow the rate if the fall is too fast. In neonates, Bolat associated a fall faster than 0.5 mmol/L per hour with death or convulsion — that hourly figure is a neonatal association, not the NICE paediatric ceiling. Cerebral oedema is the feared complication of over-rapid correction. Admit; treat the cause.^[2]