Dehydration and oral or intravenous rehydration: Case

This 16-month-old presents with severe dehydration and a threatened circulation complicating acute gastroenteritis. The weight has fallen by about 11 percent, which is in the severe band above 10 percent, and his clinical dehydration scale is in the severe range with an irritable general appearance, very sunken eyes, dry mucous membranes, and absent tears. The capillary refill of 4 seconds, the tachycardia, and the oliguria for 14 hours indicate that the circulation is failing, and the serum sodium of 158 mmol per litre confirms hypernatraemic dehydration, which makes the speed of correction the dominant concern. The metabolic acidosis reflects poor perfusion and diarrhoeal bicarbonate loss. ^[11]

The immediate priority is to assess and support the circulation. I would manage him in a high-dependency or resuscitation area with continuous monitoring. His capillary refill of 4 seconds and oliguria indicate shock rather than simple dehydration, so I would give 10 to 20 mL per kg boluses of isotonic crystalloid, either 0.9 percent sodium chloride or a balanced crystalloid such as Hartmann solution, over 5 to 10 minutes, reassessing the perfusion after each bolus and repeating up to a total of 60 mL per kg before escalating to inotropes and intensive care. The bolus is reserved for the child whose perfusion has failed, which this child has. ^[11]

Once the circulation is restored, I would manage the hypernatraemia carefully. The brain has accumulated idiogenic osmoles to defend its volume, so a rapid fall in serum sodium draws water into the brain and causes cerebral oedema, seizures, and potentially death. I would use isotonic crystalloid rather than a hypotonic solution, and I would aim to lower the sodium no faster than 0.5 mmol per litre per hour, with a daily ceiling of 8 to 12 mmol per litre, rechecking the sodium every 2 to 4 hours initially and titrating the fluid to the rate of fall. Free water and rapid correction are avoided at all costs. I would monitor his conscious level for the early signs of cerebral oedema, which are headache, vomiting, drowsiness, and seizures. ^[10]