Intravenous fluids in pediatrics

Intravenous Fluids In Pediatrics

Dr. Adeel AshiqHouse Surgeon

PSW SHL

Objectives

• Physiology of Fluid Distribution• Different types of IV fluids• Distribution of IV Fluids in Body

Compartments• Maintenance Fluid Calculation• Calculation of Deficits• Phases of Resuscitation• Special circumstances

Water Composition by Age

Distribution of Fluid in Body

Total Body Water

ECF(1/3rd)

Interstitial (2/3rd)

Intravascular (1/3rd)

ICF(2/3rd)

Diff. In ICF & ECF

Component ECF ICF

Sodium 142 14

Potassium 4.2 140

Chloride 108 4

Bicarbonate 24 10

Magnesium 0.8

Nutrient O2, Amino acid, Fatty acid Proteins

Physiology of fluid compartments

Capillary membrane• Between plasma and interstitium• Allows free passage of electrolytes• Restricts passage of protein molecules• Colloid osmotic pressure draws fluid in

capillary• Hydrostatic fluid pushes fluid out

Physiology of fluid compartments

Cell membrane• Barrier between ICF and ECF• Freely permeable to water but not to sodium• Water moves in either direction depending

upon osmolarity

Types Of Fluids

CRYSTALLOIDS:• Contain Na as major osmotically active particle• Will cross a semi-permeable membrane• E.g. Normal Saline, Ringer Lactate

COLLOIDS:• Contain high molecular weight substancces• Are largely unable to cross a semi-permeable membrane• Albumin, Dextran, Gelatin

Composition of Different Fluids

0.9% Normal Saline(‘Salt and water’)

• Iso-osmolar (compared to normal plasma)• Contains: 154 mmol/l of sodium and chloride • Stays almost entirely in the extracellular space,

so for 100ml blood loss – need to give 400ml normal saline (only 25% remains intravascular)

• Principal fluid used for intravascular resuscitation and replacement of salt loss e.g diarrhoea and vomiting

Distribution of N/S & R/L

Distribution of N/S & R/L

Cell Interstitium Vessel

750ml

250m

l

5% Dextrose (D5W)“Sugar and Water”

• Commonly used ‘maintenance’ fluid in conjuction with normal saline

• Provides some calories (approximately 10% of daily requirements)• Regarded as ‘electrolyte free’• Distribution: <10% Intravascular; > 66% intracellular• When infused is rapidly redistributed into the intracellular space;

Less than 10% stays in the intravascular space therefore it is of limited use in fluid resuscitation.

• For every 100ml blood loss – need 1000ml dextrose replacement [10% retained in intravascular space

Distribution of Dextrose Water

Distribution of Dextrose Water

666 ml 250ml

83m

l

InterstitiumCell Vessel

Albumin

• natural protein• t1/2 = 20 days in the body but t1/2 = 1.6 hours inplasma• 10% leaves the vascular space within 2 hours,

95% within 2 days• causes 80-90% of our natural oncotic pressure• stays within the intravascular space unless thecapillary permeability is abnormal

Albumin

• 5% solution- isooncotic; 10% and 25% solutions -hyperoncotic• expands volume 5x its own volume in 30 minutes• effect lasts about 24-48 hours• Side Effects- volume overload, fever (pyrogens inalbumin), defects of hemostasis

Types of Fluid Replacement

• Maintenance: Normal ongoing losses of fluids and electrolytes

• Deficit: Losses of fluids and electrolytes resulting from an illness

• On-going Losses: Requirement of fluids and electrolytes to replace ongoing losses

Maintenance Fluid Replacement

Holliday-Segar Method

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

Factors Increasing Maintenance Fluid Requirements

• Fever-each 1 degree Celcius over 38 degrees increases maintenance fluid requirements by 12%

• Hyperventilation• Increased temperature of the environment• Burns• Ongoing losses-diarrhea, vomiting, NG tube

output

Factors Decreasing Maintenance Fluid Requirements

• Skin: Mist tent, incubator (premature infants)• Lungs: Humidified ventilator• Mist tent• Renal: Oliguria, anuria• Misc: Hypothyroidism

Deficit Calculation

Sodium Deficit:

0.6x Body Weight x (Desired conc. – Current conc.)

• Do not replace Na faster than 10-12 meq/L per 24hrs. Why?Central pontine myelinosis: rapid brain cell shrinkage with rapid increase in ECF Na

Deficit Calculation

Potassium Deficit:

0.4x Body weight x ( Desierd conc – Current Conc. )

• Maximum rate of infusion < 0.5 mEq/L

Deficit Calculation

Bicarbonate Deficit :

mEq =Base deficit x 0.3 x weight in Kg

Dehydration and ResucitationConcepts

• 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.

Phases of Resuscitation

Phase I: Resuscitation :• Goal: Restore circulation, re-perfuse brain, kidneys• Mild-Moderate 20 mL/kg bolus given over 30 – 60 minutes

• SevereMay repeat bolus as needed (ideally up to 60ml/kg)

• Fluids – something isotonic such as NS or lactated ringers (LR)

Phases of Resuscitation

• Phase II: Replacement Phase• Phase III: Stabilization Phase

Goal: Replace deficit of fluids and electrolytes

Special Circumstances

Burn :

• The Parkland formula for the total fluid requirement in 24 hours is as follows:

• 4ml x TBSA (%) x body weight (kg);• 50% given in first eight hours;• 50% given in next 16 hours

Special Circumstances

Term Neonates :• Day 1: 50ml/kg/day• Day 2: 70-80ml/kg/day• Day3 : 80-100ml/kg/day• Day4: 100-120ml/kg/day• Day5: 120-150ml/kg/day

Important Guide Lines

• Measure serum electrolyte and blood glucose when starting IV fluids and at least every 24 hours thereafter.

• If Term neonate need IV Fluid for routine maintenance give isotonic crystalloid containing sodium 131-154mmol/L with 5-10% Glucose.