Fluids and Electrolytes in Pediatrics

1. Fluids and Electrolytes in Pediatrics Dr S Deepak RDH

2. Objectives • To review basics of maintenance fluid and electrolyte requirements • To enable to prescribe iv fluids appropriately • To perform case-based practice!

3. Back to Basics….Fluid compartments • Total body water= ICF + ECF • Total body water = 60-75 % of Body weight

4. Maintenance Electrolyte Requirements • Na and K are the primary electrolytes that govern ECF and ICF osmolality. [Na] in ECF = 135-145 mEq/L, negligible in ICF [K] in ICF = 150 mEq/L, negligible in ECF • Maintenance Electrolyte Requirements: Na: 2-3 mEq/100ml water /day OR 2-3 mEq/kg/day K: 1-2 mEq/100ml of water/day OR 1-2mEq/kg/day Chloride: 2 mEq/100ml of water /day

5. Concepts • Maintenance: Normal ongoing losses of fluids and electrolytes • Deficit: Losses of fluids and electrolytes resulting from an illness e.g Diarrhoea • On-going Losses: Requirement of fluids and electrolytes to replace ongoing losses eg stoma losses

6. Goal of Fluid Therapy • To prevent dehydration • To prevent electrolyte abnormalities • To prevent acidosis and circulatory collapse

7. KEY • Whenever possible use enteral route for hydration. • If the child needs iv fluids – do baseline UE during cannulation. • Use the appropriate type and rate of fluid.

8. Calculation of Maintenance Fluid Requirements…the Holliday-Segar Method Example: A 30-kg child would require (100 × 10) + (50 × 10) + (20 × 10) = 1,700 cc/day or (4 × 10) + (2 × 10) + (1 × 10) = 70 cc/h.

9. Choosing the Appropriate fluid

10. Guidelines • All children the recommended maintenance fluids is 0.45% sodium chloride and 5% glucose with added potassium • For children<20 kg- 10mmol KCl/500 ml bag • For children>20 kg- 20mmol KCl/500 ml bag

11. DEHYDRATION….Calculating Deficits

12. Concepts in Dehydration • Initial loss of fluid from the body depletes the extracellular fluid (ECF). • Gradually, water shifts from the intracellular space to maintain the ECF, and this fluid is lost if dehydration persists. • Acute Illness (<3 days ): 80% of the fluid loss is from the ECF and 20% is from the intracellular fluid (ICF). • Prolonged Illness (> 3 days): 60% fluid loss from ECF and 40% loss from ICF.

14. Pre-Illness Weight Estimate of Dehydration • Need to accurately monitor patient weights frequently Fluid deficit (L) = PIW (kg) – IW (kg) PIW = Pre-illness weight IW = Illness weight % Dehydration = PIW (kg) – IW (kg) x 100% PIW (kg)

16. Hyponatremic dehydration

17. Assesement • Mild to moderate hyponatraemia is usually asymptomatic. • The symptoms and signs of severe hyponatraemia are mainly neurological: Headache, nausea, vomiting, lethargy, irritability, hyporeflexia and decreased GCS Seizures • Assess hydration • If [Na+] <130mmol/L, check remainder of U&Es and glucose • Measurement of urinary sodium and osmolality may be useful

18. Management • Ideal rate of sodium correction depends on the presence and severity of symptoms • Too rapid correction (>8mmol/L Na+/day) can result in cerebral demyelination; this is particularly a concern if the hyponatraemia has been present for >5 days. • For symptomatic hyponatremia- contact senior immediately, refer to guidelines

19. Hypernatremic dehydration

20. Assesement • Clinical signs occur more severely with acutely developing hypernatraemia • Severe symptoms mainly occur when [Na+] >160mmol/L( Lethargy , Irritability , “Doughy” skin, ataxia/tremor, hyperreflexia, seizures • True degree of dehydration is often underestimated • Shock occurs late because of preserved intravascular volume

21. Management • Always inform the seniors and seek advice • Causing the serum sodium to fall too rapidly can precipitate cerebral oedema and death • Aim to lower the sodium by no more than 12mmol/L/day (this will need to be even slower in hypernatraemia present for >5 days)

22. Monitoring of children on IV fluids • Strict fluid balance, including oral intake and urine output, must be recorded in any child receiving IV fluids • Daily weight measurements should be recorded in all children • Plasma urea and electrolytes should be measured at the time of cannulation in all children who are likely to receive IV fluids • Plasma urea and electrolytes must be measured daily in all children receiving full IV fluids. Consider measuring every 4-6 hours if an abnormal result is obtained.

23. Let’sPractice

24. Take Home Message • Oral rehydration is a safe and effective intervention in patients with mild-to-moderate dehydration who are able to tolerate oral regimen. • Fluid calculations are “best estimates.” Always monitor the effects of your interventions. • Act on abnormal results. • Slow correction of both hyponatremia and hypernatremia. DO NOT HESITATE TO ASK IF IN DOUBT

25. References • www.nice.org.uk/CG84 • Fleisher, G. et al. (2005). Renal and Electrolyte Emergencies. In Cronan, K. & Kost (Eds), Textbook of Pediatric Emergency Medicine. • Kleigman, R. et al. Nelson Essentials of Pediatrics. Chapter 32: Fluids and Electrolytes. 5th edition. pp.157-163. • Trust Guidelines ,Royal Derby Hospital(updated 2012) • Haycock GB. Hyponatraemia: Diagnosis and Management. Arc Dis Child EducPract Ed 2006;91:ep37-ep41.