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PE15.1-4 | Fluids and Electrolytes — PBL Case

CLINICAL SETTING

Government district hospital, paediatric ward, North India. A 2-year-old boy, Aryan, weighing 11 kg, is brought in by his mother at 3 PM in July. The ward is busy; the ceiling fan is working but the temperature outside is 42°C. His mother says he has had watery diarrhoea about 10–12 times and vomited 4 times in the last 18 hours. He has not passed urine since this morning. She has been giving him rice water at home but he is refusing to drink much. You are the house officer on duty.

Trigger 1: First Assessment — The Crying, Restless Child

On examination: Aryan is irritable and crying. HR 148/min, RR 34/min, temperature 37.8°C. His eyes appear sunken. When you offer him water, he drinks eagerly. Skin pinch over the abdomen returns in 1.5 seconds (slow). Anterior fontanelle is not bulging. Mucous membranes are dry. His weight today is 11 kg (mother says it was 12 kg three weeks ago at the immunisation visit). CRT is 2 seconds. No signs of blood in the stool described by the mother.

DISCUSSION POINTS

  • Using IMNCI criteria, classify Aryan's degree of dehydration and identify each sign that supports your classification.
  • Which IMNCI treatment Plan (A, B, or C) should you initiate, and why? What is the key clinical feature that determines this plan?
  • Calculate Aryan's Holliday-Segar maintenance fluid requirement (mL/day and mL/hr). Then calculate his estimated deficit volume based on the weight change and degree of dehydration. What is the total 24-hour fluid requirement?
Click to reveal Trigger 2: ORS and the First Hour — Then a Problem with the Drip (discuss previous trigger first!)

Trigger 2: ORS and the First Hour — Then a Problem with the Drip

You initiate Plan B. The nurse brings reduced-osmolarity ORS sachets and mixes them correctly. Aryan accepts ORS reluctantly — he has taken about 180 mL in the first hour. At this point, his mother reports he has had two more watery stools. You decide he also needs an IV cannula for a slow dextrose-saline drip as a precaution. The nurse attempts IV cannulation at the right dorsum of hand — unsuccessful. She asks you to try. You locate a small vein at the left antecubital fossa, insert a 24G cannula, but when you flush with normal saline you notice mild swelling. You remove the cannula. The vein at the right foot is also fragile and collapses. Two IV attempts have now failed.

DISCUSSION POINTS

  • Describe how you would confirm correct intravascular placement of a peripheral IV cannula in a young child. What does flashback in the chamber, free aspiration, and a clean saline flush confirm?
  • After two failed IV attempts in a child who, while not yet in severe dehydration, is deteriorating and unable to maintain ORS intake, is there a role for intraosseous (IO) access? When is IO access indicated and what is the standard site?
  • What are the steps to insert an IO needle at the proximal tibia? How do you confirm correct IO placement before beginning fluid infusion?
Click to reveal Trigger 3: Lab Results Arrive — A Sodium Surprise (discuss previous trigger first!)

Trigger 3: Lab Results Arrive — A Sodium Surprise

The ward nurse manages to insert a 22G cannula in the right saphenous vein after repositioning. Blood samples sent earlier now return: - Serum Na: 126 mmol/L - Serum K: 3.1 mmol/L - Serum urea: 9.8 mmol/L - Blood glucose: 4.2 mmol/L - Blood gas: pH 7.28, HCO3 14 mmol/L (metabolic acidosis) The junior registrar suggests rapidly correcting the sodium with half-normal saline over 4 hours to get Na above 130 before dinner. You are unsure this is correct.

DISCUSSION POINTS

  • Interpret Aryan's electrolyte panel. What type of hyponatraemia is most likely in acute diarrhoea and vomiting — hypovolaemic, isovolaemic, or hypervolaemic? How does this affect your fluid choice?
  • What is the maximum safe rate of sodium correction over 24 hours and why? What neurological complication can occur with overcorrection, and what is the mechanism (think: idiogenic osmoles / brain adaptation)?
  • Does K of 3.1 mmol/L require IV potassium supplementation at this stage? If IV potassium is needed, what is the maximum safe infusion rate and concentration? Why must it never be given as a bolus?
Click to reveal Trigger 4: Aryan at 6 Hours — Reassessment and Plan (discuss previous trigger first!)

Trigger 4: Aryan at 6 Hours — Reassessment and Plan

Six hours after admission, Aryan has received 600 mL of ORS and 250 mL of IV normal saline with 20 mmol/L KCl at the calculated rate. He is now calmer, eyes appear less sunken, skin turgor has improved, and he accepts a small feed. HR is 122/min. A repeat serum Na is 129 mmol/L — it has risen by 3 mmol/L over 6 hours. His mother is reassured and asks whether he can go home tomorrow if he stays well overnight.

DISCUSSION POINTS

  • You check the sodium correction: Na rose from 126 to 129 mmol/L in 6 hours (3 mmol/L). Project what the total rise will be over 24 hours if this rate continues. Is this within the safe ceiling of 10–12 mmol/L/24 h? What adjustments, if any, are needed?
  • Aryan is improving. When would you transition him from IV/facility ORS (Plan B) to home ORS (Plan A)? What instructions would you give the mother about ORS preparation, volumes, and danger signs requiring return?
  • Reflecting on this case: which aspects of fluid and electrolyte management carry the highest risk of error in clinical practice? What safeguards (rate calculations, regular electrolyte monitoring, rate limits) prevent those errors?

Group Task Assignments

Group 1: Collaborative Task

Group 2: Collaborative Task

Group 3: Collaborative Task

Learning Issues

Research these questions and bring your findings to the discussion.

  1. [PE15.1] How do you calculate maintenance fluid requirements using the Holliday-Segar formula, and how do you integrate deficit correction into the 24-hour fluid plan for a dehydrated child?
  2. [PE15.1] What are the IMNCI criteria for classifying degrees of dehydration, and how do Plans A, B, and C differ in fluid type, route, volume, and setting?
  3. [PE15.2] What is the maximum safe rate of sodium correction in hyponatraemia, what is the risk of overcorrection, and how does the management differ for hypovolaemic versus isovolaemic hyponatraemia?
  4. [PE15.2] What are the indications and sequence of interventions for hyperkalaemia with ECG changes, and what are the safety limits for IV potassium supplementation?
  5. [PE15.3] What are the steps and confirmation signs for peripheral IV cannula insertion in a child, and what are the common failure points in small paediatric veins?
  6. [PE15.4] When is intraosseous access indicated in a paediatric emergency, and what is the technique for proximal tibial IO insertion including confirmation of placement?