Pediatrics
Fluid and Electrolyte Balance
Pediatric fluids and electrolytes for MBBS: Holliday-Segar maintenance, deficit calculation, hyperkalaemia and hyponatraemia management and WHO diarrhoea plans, mapped to NMC codes PE15.1 to PE15.7.
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Fluid and Electrolyte Balance
Pediatric fluids and electrolytes for MBBS: Holliday-Segar maintenance, deficit calculation, hyperkalaemia and hyponatraemia management and WHO diarrhoea plans, mapped to NMC codes PE15.1 to PE15.7.
This chapter covers fluid and electrolyte requirements in health and disease, the calculation of maintenance and deficit fluids, interpretation of electrolyte reports, and the emergency management of dyselectrolytaemias. It also covers WHO diarrhoea plans and the technique of intravenous cannulation.
High-yield: Fluid and Electrolyte Balance
- The Holliday-Segar formula gives maintenance fluid as 100/50/20 millilitres per kilogram per day, or 4/2/1 millilitres per kilogram per hour.
- Daily electrolyte maintenance needs are roughly sodium 2 to 3 mmol per kilogram and potassium 1 to 2 mmol per kilogram.
- Isotonic maintenance fluids are preferred to prevent SIADH-driven hospital-acquired hyponatraemia.
- The ECG is the most important investigation in both hypokalaemia and hyperkalaemia.
- Symptomatic hyponatraemia with seizures is treated with 3 percent saline 2 to 3 millilitres per kilogram.
- In hyperkalaemia with ECG changes, calcium gluconate is given first to protect the heart, then insulin with dextrose to shift potassium into cells.
- The fluid deficit in millilitres equals the percent dehydration divided by 100, multiplied by weight in kilograms, multiplied by 1000.
- Maintenance fluid must be added to the deficit, and ongoing losses are replaced separately.
- Hypertonic dehydration must be corrected slowly to avoid cerebral oedema.
- The anion gap is sodium minus the sum of chloride and bicarbonate, with a normal value of 8 to 12.
- IV cannula gauge is chosen by age: 24G for a neonate, 22G for an infant or toddler, 20G for a school-age child and 18G for an adolescent or resuscitation.
- An IV cannula is inserted at an angle of about 10 to 25 degrees, and the needle is disposed of immediately in a sharps container.
- WHO diarrhoea Plan B gives 75 millilitres per kilogram of oral rehydration solution over 4 hours, while Plan C gives 100 millilitres per kilogram of intravenous fluid.
- Oral rehydration solution works through sodium-glucose cotransport (SGLT1), and zinc given with ORS reduces the duration of diarrhoea.
Fluid and electrolyte essentials
- **Maintenance (Holliday-Segar):** 100/50/20 mL/kg/day or 4/2/1 mL/kg/hour.
- **Deficit:** (% dehydration / 100) x weight (kg) x 1000; add to maintenance.
- **Hyperkalaemia with ECG changes:** Calcium gluconate first, then insulin-dextrose to shift potassium.
- **WHO diarrhoea plans:** Plan B = 75 mL/kg ORS over 4 hours; Plan C = 100 mL/kg IV fluid.
NMC competencies in this chapter
- **PE15.1:** Fluid and electrolyte requirement in health and disease
- **PE15.2:** Clinical features, complications and management of fluid and electrolyte imbalance
- **PE15.3:** Calculate fluid and electrolyte requirement in health
- **PE15.4:** Interpret an electrolyte report
- **PE15.5:** Calculate fluid and electrolyte imbalance
- **PE15.6:** Demonstrate steps of inserting an intravenous cannula in a model
- **PE15.7:** Discuss fluid management including type, amount and rate in various conditions
Frequently Asked Questions
What is the Holliday-Segar maintenance fluid formula?
The Holliday-Segar formula gives daily maintenance fluid as 100 millilitres per kilogram for the first 10 kilograms, 50 for the next 10 kilograms and 20 for each kilogram above 20, equivalent to the 4/2/1 millilitres per kilogram per hour rule.
How is hyperkalaemia with ECG changes managed?
When hyperkalaemia produces ECG changes, calcium gluconate is given first to stabilise and protect the myocardium, followed by insulin with dextrose to shift potassium into cells, with further measures to remove potassium from the body.
How is fluid deficit calculated in dehydration?
The fluid deficit in millilitres equals the percent dehydration divided by 100, multiplied by the weight in kilograms, multiplied by 1000. This deficit is added to maintenance fluids, and ongoing losses are replaced separately.
What are WHO diarrhoea Plans B and C?
Plan B treats some dehydration with 75 millilitres per kilogram of oral rehydration solution over 4 hours, while Plan C treats severe dehydration with about 100 millilitres per kilogram of intravenous fluid given in staged doses.
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