Pediatric Fluids and Pediatric Fluids and ElectrolytesElectrolytesKatinka KerstenKatinka Kersten

Learning ObjectivesLearning Objectives

Recognize that fluid and electrolyte homeostasis is Recognize that fluid and electrolyte homeostasis is different in infants, children and adults different in infants, children and adults

Know contents of different fluid compartments in Know contents of different fluid compartments in bodybody

Know how to estimate maintenance fluid and Know how to estimate maintenance fluid and electrolyte needselectrolyte needs

Know fluid management for patients withKnow fluid management for patients with Isonatremic dehydrationIsonatremic dehydration Hyponatremic dehydrationHyponatremic dehydration Hypernatremic dehydrationHypernatremic dehydration

Know contents of different intravenous and oral Know contents of different intravenous and oral rehydration solutionsrehydration solutions

ECF and ICFECF and ICF

Body has two fluid compartmentsBody has two fluid compartments Extracellular fluid (ECF) space makes up 1/3 of our body Extracellular fluid (ECF) space makes up 1/3 of our body

fluidsfluids Intracellular fluid (ICF) space makes up 2/3 of our body Intracellular fluid (ICF) space makes up 2/3 of our body

fluidsfluids Extracellular space refers to fluids outside our cells Extracellular space refers to fluids outside our cells

which may be interstitial fluid or plasma orwhich may be interstitial fluid or plasma orCSFCSF

Total body water = 0.6 X weight (kg) for children and Total body water = 0.6 X weight (kg) for children and adults and 0.78 X weight (kg) for neonates and adults and 0.78 X weight (kg) for neonates and infantsinfants

Developmental Differences in Developmental Differences in ChildrenChildren

Increased fluid intake and output relative to Increased fluid intake and output relative to size. Total body fluid of infants is 20% more size. Total body fluid of infants is 20% more than adultsthan adults

Greater surface area relative to size and Greater surface area relative to size and therefore more water loss through skintherefore more water loss through skin

Increased metabolic rateIncreased metabolic rate Immature kidney function that requires more Immature kidney function that requires more

fluid to excrete wastefluid to excrete waste

ICF (mEq/L) ECF (mEq/L)Sodium 20 135-145Potassium 150 3-5 Chloride --- 98-110Bicarbonate 10 20-25Phosphate 110-115 5Protein 75 10

ECF and ICF Composition

Approach to Fluid CalculationsApproach to Fluid Calculations

1. Maintenance: Determined by a ‘system’: a. Caloric expenditure method b. Holliday-Segar method

c. Surface area methodLOW AMOUNT OF ELECTROLYTES IN FLUID

2. Deficit: Determined by acute weight change or clinical estimate

HIGH AMOUNT OF ELECTROLYTES IN FLUID3. Ongoing losses: Determined by measuring

Basal MetabolismBasal Metabolism Daily fluid and electrolyte need is related to daily Daily fluid and electrolyte need is related to daily

average energy requirement.average energy requirement. Daily energy requirement is determined by Resting Daily energy requirement is determined by Resting

Energy Expenditure (REE) plus correction factor for Energy Expenditure (REE) plus correction factor for activity, fever, trauma, injury and growth.activity, fever, trauma, injury and growth.

When compared to body weight the Resting When compared to body weight the Resting Energy Expenditure (REE) is high in the newborn, Energy Expenditure (REE) is high in the newborn, and lower in adultsand lower in adults

Maintenance Fluid Maintenance Fluid SimplificationSimplification

It’s impossible to know Resting Energy It’s impossible to know Resting Energy Expenditure and average daily energy needs Expenditure and average daily energy needs for different ages and sizes and most people for different ages and sizes and most people rely on existing tables.rely on existing tables.

Two systems have been proposed to relate Two systems have been proposed to relate maintenance fluid and electrolyte needs to maintenance fluid and electrolyte needs to the body weight.the body weight. Surface area methodSurface area method Holliday-Segar methodHolliday-Segar method

Most widely used method Landmark paper by Holliday and Segar in 1957Studies done on healthy infants and childrenAssumes 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

Holliday-Segar Method

Holliday-SegarHolliday-Segar

FLUID REQUIREMENTSFLUID REQUIREMENTS For first 10 kg 100 ml/kg/day (4ml/kg/hr)For first 10 kg 100 ml/kg/day (4ml/kg/hr) For second 10 kg 50 ml/kg/day For second 10 kg 50 ml/kg/day (2ml/kg/hr)(2ml/kg/hr) Each additional kg 20 ml/kg/dayEach additional kg 20 ml/kg/day (1ml/kg/hr)(1ml/kg/hr)

ElECTROLYTE REQUIREMENTSElECTROLYTE REQUIREMENTS NaNa++ 3 mEq/100ml 3 mEq/100ml ClCl- - 4 mEq/100ml4 mEq/100ml KK++ 2 mEq/100ml 2 mEq/100ml

REPLACEMENT REPLACEMENT OF DEFICITOF DEFICIT

ECF and ICF Contributions to LossECF 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

Type Percent Symptoms

Very mild <3 Thirst may be presentMild 3-5 Dry mucous membranes

and conjunctivaModerate 5-7 Sunken eyes, decreased

fontanelleSevere 7-12 Tenting of skinVery severe >12 Shock

Clinical signs of Dehydration

Oral Rehydration TherapyOral Rehydration Therapy

Safest way to rehydrate patient is by the Safest way to rehydrate patient is by the enteral routeenteral route

Best to use ORS as this is least hyponatremic. Best to use ORS as this is least hyponatremic. However many patients don’t take this However many patients don’t take this because salty. Pedialyte decent as well and because salty. Pedialyte decent as well and thirdly Gatoratethirdly Gatorate

Can not do this in patients withCan not do this in patients with Severe altered mental statusSevere altered mental status Persistent severe vomitingPersistent severe vomiting Intestinal obstructionIntestinal obstruction

Electrolytes in Popular Electrolytes in Popular DrinksDrinks

Na (mEq/L) K (mEq/L)Apple juice 0.4 26Coke 4.3 0.1Gatorade 21 2.5Milk 22 36OJ 0.2 49Pedialyte 45 20WHO ORS 90 20

A 2 year old has a 6-day history of gastroenteritis, poor fluid intake and infrequent urination. On exam youfind dryness of the mucous membranes, sunken eyeswith mild tenting of the skin. The serum sodiumis 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?

Isotonic dehydration (Na 130-145 mEq/L)

H2O Na K (ml) (mEq) (mEq)

Maintenance (Holiday/Segar)

Total deficit = 1000 ml Extracellular fluid deficit(50% of total)Intracellular fluid deficit(50% of total)Total

Isotonic Dehydration Example

1000 30 20

500 70

500 75

2000 100 95

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 expectbased on fluid loss•Always assume total fluid deficit of at least 10%

Free Water DeficitUse 4 ml/kg of body weight for each mEq of Na+

above 145 mEq/L as the Free Water Deficit

(Serum Na+ -145 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/LFor Na+ > 175 mEq/L you do not want to correctfaster than 1 mEq/L/hr

Hypertonic Dehydration Example

6-month-old suffering for 3 days from severediarrhea.Mucous membranes are dry, skin feels doughyand the child is somnolent and lethargic.The serum Na+ is 165 mEq/L.The child weighs 5 kg and you assume the fluid deficitis at least 10%.

What are the fluid and electrolyte requirements?

Hypertonic Dehydration Example

H2O Na K (ml) (mEq) (mEq)

Maintenance (Holiday/Segar)

Total deficit = 500 ml½ of Free Water Deficit {(165-145)x5x4x½}Remainder of deficit {(500-200) = 300 ml} Extracellular (60%) Intracellular (40%)Total

500 15 10

200

180 25 120 18

1000 40 28

Hypotonic Dehydration (Na+ < 135 mEq/L)

•Children with vomiting and diarrhea who have receivedhypotonic fluids as oral replacement•Shock is an early symptom.•Physical exam findings usually exaggerateamount of dehydration.

Additional NaAdditional Na++ needed needed

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

Hypotonic Dehydration Example

A 3-year-old has had diarrhea and vomiting for1 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?

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 {(135-120) x 0.6 x 14}Total

1200 36 24

800 112 200 30

126

2200 274 54

Na K Cl HCO3Gastric juice 140 15 155 0Small-intestinal juice 140 15 155 40Diarrhea 40 40 40 40Sweat 70 15 60 0

Electrolytes in Body Fluids (mEq/L)

Fluid cal/L Na K CL HCO3

D5W 170 0 0D10W 340 0 0NS 0 154 1541/2 NS 0 77 77D5 1/4 NS 170 34 34LR 0 130 4 109 28Alb. 25% 1000100-160 <120

Composition of Parenteral Fluids