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Pediatric Fluids and Electrolytes

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1 Pediatric Fluids and Electrolytes
Katinka Kersten

2 Learning Objectives Recognize that fluid and electrolyte homeostasis is different in infants, children and adults Know contents of different fluid compartments in body Know how to estimate maintenance fluid and electrolyte needs Know fluid management for patients with Isonatremic dehydration Hyponatremic dehydration Hypernatremic dehydration Know contents of different intravenous and oral rehydration solutions

3 ECF and ICF Body has two fluid compartments
Extracellular fluid (ECF) space makes up 1/3 of our body fluids Intracellular fluid (ICF) space makes up 2/3 of our body fluids Extracellular space refers to fluids outside our cells which may be interstitial fluid or plasma or CSF Total body water = 0.6 X weight (kg) for children and adults and 0.78 X weight (kg) for neonates and infants


5 Developmental Differences in Children
Increased fluid intake and output relative to size. Total body fluid of infants is 20% more than adults Greater surface area relative to size and therefore more water loss through skin Increased metabolic rate Immature kidney function that requires more fluid to excrete waste

6 ECF and ICF Composition
ICF (mEq/L) ECF (mEq/L) Sodium Potassium Chloride Bicarbonate Phosphate Protein

7 Approach to Fluid Calculations
1. Maintenance: Determined by a ‘system’: a. Caloric expenditure method b. Holliday-Segar method c. Surface area method LOW AMOUNT OF ELECTROLYTES IN FLUID 2. Deficit: Determined by acute weight change or clinical estimate HIGH AMOUNT OF ELECTROLYTES IN FLUID 3. Ongoing losses: Determined by measuring

8 Basal Metabolism Daily fluid and electrolyte need is related to daily average energy requirement. Daily energy requirement is determined by Resting Energy Expenditure (REE) plus correction factor for activity, fever, trauma, injury and growth. When compared to body weight the Resting Energy Expenditure (REE) is high in the newborn, and lower in adults

9 Maintenance Fluid Simplification
It’s impossible to know Resting Energy Expenditure and average daily energy needs for different ages and sizes and most people rely on existing tables. Two systems have been proposed to relate maintenance fluid and electrolyte needs to the body weight. Surface area method Holliday-Segar method

10 Holliday-Segar Method
Most widely used method Landmark paper by Holliday and Segar in 1957 Studies done on healthy infants and children Assumes that for each 100 calories metabolized, 100 ml H2O will be required (50 ml/100 calories for insensible loss, 67 ml/100 calories for urine and 17 ml/100 calories gained from metabolism) Not suitable for newborns

For first 10 kg 100 ml/kg/day (4ml/kg/hr) For second 10 kg 50 ml/kg/day (2ml/kg/hr) Each additional kg 20 ml/kg/day (1ml/kg/hr) ElECTROLYTE REQUIREMENTS Na+ 3 mEq/100ml Cl- 4 mEq/100ml K+ 2 mEq/100ml


13 ECF and ICF Contributions to Loss
If losses occur over very short period most of the loss is from ECF If losses occur over long period of time losses are about 50/50 ICF and ECF

14 Clinical signs of Dehydration
Type Percent Symptoms Very mild <3 Thirst may be present Mild Dry mucous membranes and conjunctiva Moderate Sunken eyes, decreased fontanelle Severe Tenting of skin Very severe >12 Shock

15 Oral Rehydration Therapy
Safest way to rehydrate patient is by the enteral route Best to use ORS as this is least hyponatremic. However many patients don’t take this because salty. Pedialyte decent as well and thirdly Gatorate Can not do this in patients with Severe altered mental status Persistent severe vomiting Intestinal obstruction

16 Electrolytes in Popular Drinks
Na (mEq/L) K (mEq/L) Apple juice Coke Gatorade Milk OJ Pedialyte WHO ORS

17 Isotonic dehydration (Na 130-145 mEq/L)
A 2 year old has a 6-day history of gastroenteritis, poor fluid intake and infrequent urination. On exam you find dryness of the mucous membranes, sunken eyes with mild tenting of the skin. The serum sodium is 137 mEq/L. The weight is 10 kg. You determine the child is suffering from about 10% dehydration. What are the fluid and electrolyte requirements?

18 Isotonic Dehydration Example
H2O Na K (ml) (mEq) (mEq) Maintenance (Holiday/Segar) Total deficit = 1000 ml Extracellular fluid deficit (50% of total) Intracellular fluid deficit Total

19 Hypertonic Dehydration (Na+ > 145 mEq/L)
Mortality can be high Often iatrogenic The intravascular volume (extracellular space) is preserved at the expense of the intracellular volume The patient looks better than you would expect based on fluid loss Always assume total fluid deficit of at least 10%

20 Free Water Deficit Use 4 ml/kg of body weight for each mEq of Na+
above 145 mEq/L as the Free Water Deficit (Serum Na mEq/) x weight x 4 = total amount of free water needed to dilute the serum to get a normal concentration Na+ Only correct half of total Free Water Deficit in first 24 hours if Na+ < 175 mEq/L For Na+ > 175 mEq/L you do not want to correct faster than 1 mEq/L/hr

21 Hypertonic Dehydration Example
6-month-old suffering for 3 days from severe diarrhea. Mucous membranes are dry, skin feels doughy and the child is somnolent and lethargic. The serum Na+ is 165 mEq/L. The child weighs 5 kg and you assume the fluid deficit is at least 10%. What are the fluid and electrolyte requirements?

22 Hypertonic Dehydration Example
H2O Na K (ml) (mEq) (mEq) Maintenance (Holiday/Segar) Total deficit = 500 ml ½ of Free Water Deficit {( )x5x4x½} Remainder of deficit {( ) = 300 ml} Extracellular (60%) Intracellular (40%) Total 200

23 Hypotonic Dehydration (Na+ < 135 mEq/L)
Children with vomiting and diarrhea who have received hypotonic fluids as oral replacement Shock is an early symptom. Physical exam findings usually exaggerate amount of dehydration.

24 Additional Na+ needed To calculate the Na+ Deficit, multiply 0.6 mEq/kg of body weight for each mEq of Na+ below 135 mEq/L.

25 Hypotonic Dehydration Example
A 3-year-old has had diarrhea and vomiting for 1 day. Examination shows sunken eyes and marked tenting of the skin but the child is not in shock. The serum Na+ is 120 mEq/L. The weight 14 kg. You estimate the deficit as 7%. What are the fluid and electrolyte requirements for this patient?

26 Hypotonic Dehydration Example
H2O Na K (ml) (mEq) (mEq) Maintenance (Holliday/Segar) Deficit (7% of 14 kg) Extracellular fluid (80%) Intracellular fluid (20%) Additional sodium {( ) x 0.6 x 14} Total 126

27 Electrolytes in Body Fluids (mEq/L)
Na K Cl HCO3 Gastric juice Small-intestinal juice Diarrhea Sweat

28 Composition of Parenteral Fluids
Fluid cal/L Na K CL HCO3 D5W D10W NS 1/2 NS D5 1/4 NS LR Alb. 25% <120

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