Fluid maintenance and deficit replacement — OSCE

Candidate brief

You are the paediatric registrar. A 3-year-old girl, 14 kg, is admitted with gastroenteritis and assessed as about 7 percent dehydrated. She is not in shock and is passing urine. The team has started intravenous fluid. The parents want to understand how the doctors decided how much fluid to give, why the bag has salt and sugar and potassium in it rather than just water, why their daughter is weighed every morning, and what signs should bring them back in future. Explain clearly, check understanding, and agree a plan. [8]

Marking domains

Clinical knowledge and accuracy (3). Explains that the daily fluid is worked out from her weight by a standard rule, roughly 1000 plus 200 mL a day for her 14 kg; that the drip bag contains salt at body strength with sugar for energy and a little potassium because her blood tests showed these were needed; and that using salt at body strength rather than plain water protects her brain from a dangerous drop in salt levels while she is unwell. [1][2]

Communication and plain language (3). Avoids jargon or defines it; uses an analogy (the body is like a system that needs the right amount of water and salt each day, and being sick upsets the balance); paces the information; pauses to check understanding; invites questions. Conveys that the bag was chosen specifically for her and will be reviewed every day. [2]

Management plan and safety-net (3). Explains the daily weigh as the simplest way to see whether the balance is right, the plan to step down to drinking as she improves, and the monitoring of her salt levels on blood tests. Gives a clear safety-net: seek help if she becomes drowsy or unusually irritable, has a seizure, cannot keep any fluid down, or passes little or no urine; and explains that oral rehydration solution at home is the first step if mild illness recurs. [8]

Empathy and partnership (1). Acknowledges the parents' anxiety, validates that dehydration is frightening to watch, and frames the plan as a shared one they are part of, with the daily weigh as something they can follow along with. [2]

Examiner notes

Strong candidates explain the WHY of the saline bag in plain terms (plain water would be unsafe because being unwell makes the body hold onto water and could drop her salt), name the daily weight as the key bedside check, and give a concrete safety-net of drowsiness, seizure, no urine and failure to drink. Weak candidates call it just a drip, cannot say why the bag is saline rather than water, or offer vague reassurance without a safety-net. [2][8]