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Fluid & Electrolyte
Balance
Dr. Deepaka Weerasekara
Objectives
Understand the physiology of fluid
distribution throughout the body.
Assessment of hypovolaemia
Managing fluid balance
Managing electrolyte balance
Basic Physiology
TOTAL BODY WATER
B.W X 0.6 600 ml/Kg(42 L)
ICF ECF
BW X 0.4 BW X 0.2
400ml/Kg 200 ml/Kg (14L)
(28 L )
Interstitial Fluid Plasma
BW X 0.15 BW X 0.05
150 ml/kg(11L) 50 ml/kg (3L)
Water Balance
Input ( Thirst )
Total Body water 600 ml/Kg
Output
Faeces
100ml/24hr
Insensible Loss
15ml/Kg/24Hr
(Skin, Respiration)
Urine Output
1ml/Kg/hr
1500ml/24hrs
OSMOLALITY
Normal plasma osmolality -290 mOsm/kg
Osmolality = 2( Na+ +k+ ) + glucose +
(mOsm/kg) urea (mmol/l)
Compartments from which fluids are lost
depends on the cause of fluid loss.
In which compartments fluid will end up
when administered to the patient depends
on the type of fluid administered.
Fluid replacement
Maintenance - basic needs
Prior deficits - Fasting , vomiting ,diarrhoea,
NG suction etc.
Continuing abnormal losses - Blood loss,
NG suction, Third space loss, fever etc.
Maintenance
Normal water requirement-30/35ml/kg/day
Sodium-2mmol/kg/day
Potassium-1mmol/kg/day
Continuing loss
Eg- Bowel obstruction
- By normal saline with added [k+]
- Keep a fluid balance chart
- Monitor input and output
- Replace 24 hour all fluid out + insensible (urine, drainage, vomitus) loss.
Any patient on IV fluids should have a daily
fluid balance, daily electrolyte measurement,
new regimen prescribed.
Repeat should NOT be used.
Pre existing losses
To identify which compartment / compartments
the fluid has been lost from.
To assess the extent of dehydration.
Which compartment?
Bowel losses - ECF
Pure water losses - total body water
Protein loss - plasma
Water and electrolyte
replacement
ECF losses - normal saline , Hartmanns with added (K+)
Acute hypovolaemia - Gelofusin
Plasma losses
Continuing losses- Hetastarch Dextran
Assessment of fluid loss
Clinical
Thirst
Reduced urine output
Loss of skin turgor
Rapid low volume pulse
Low BP
Low CVP
MILD MODERATE SEVERE
Thirst + + ++
Tongue ( Buccal sulcus) + ++
Skin and sunken eyes + ++
Urine output (kg/hr) <1 <0.5 <0.5
Pulse ( beats/min) Normal Normal 100-200
Blood pressure (mmHg) Normal Normal 80-100
Respiratory rate Normal Normal Normal
Clinical Assessment of Dehydration
Investigations
Blood urea
Serum electrolytes
Urine specific gravity & osmolality
Haematocrit - Unreliable in acute blood loss
Quantification of plasma and
ECF loss
Using changes in haematocrit and serum Albumin levels
In ECF depletion P1 - Initial Albumin [ ]
P2 - [ ] after dehydration
% fall in ECF volume=(1-p1/p2)x100
Also % fall in plasma volume=100[1-Hct1/100-Hct1 x100- Hct2
/Hct2]
Three questions???
WHAT to give?
HOW MUCH to give?
HOW fast?
What Fluids?
Depends on the compartment affected.
Gastric loss-N saline
Intestinal loss- Hartmanns
NG aspirate- N.S. + Hartmanns
Third space-(5-15 ml/kg/hr)-N.S.
HOW MUCH OF FLUID?
Calculated in litres as a percentage of
body weight in kg.
mild moderate severe
Adults 4% 6% 8%
(40ml/kg) (60ml/kg) (80ml/kg)
Children 5% 10% 15%
(this is a guide only .Should be tailored to individual needs.)
HOW FAST?
Give half the requirement in 12 hours and
other half in the next 48 hours.
In severe depletion 20 ml/kg for the 1st
hour. (caution-elderly)
MONITORING
Pulse ,blood pressure ,JVP ,Lung bases
Urine output/hour, serial PCV
Adequacy-urine output of 1ml/kg/hr
Over hydration-jugular venous engorgement ,
lung crepitations ,hypertension
Post-op Fluid Management
Normal maintenance fluid
If blood or serum is lost
If GI loss continued
* Normally K is not given during 1st 24Hr.
* After major surgery assessment of fluid should
be according to ;
Fluid balance , Clinical signs / symptoms , CVP monitoring
Replace
Potassium Balance
Adult Requirement -- 0.6 – 1mg / kg / day
Normal serum potassium – 3.5 - 5.3 meq / l
90% total body potassium is in the ICF
K+ < 3.5 mmol/l
How would you correct it?
Hypokalaemia
Hyperkalaemia
K+ > 5.5mmol/l
K+ >7 mmol/l symptomatic
Treatment of hyperkalaemia
10 ml of 10% calcium gluconate i.v. over 10 min.(why ?)
10 U of Insulin in 50ml of 50% dextrose i.v. over 30min.
NaHCO3 50 mmol
Beta 2 agonist
What is the purpose of dextrose infusion?
What is the best guide to adequate fluid
replacement?
What do you understand by the term
“Third space loss”?
Questions ?????
Following are True or False
Excessive sweating increases the haematocrit.
Infusion of normal saline increases the serum Na+
Infusion of 5% Glucose decreases the haematocrit
Diarrhoea causes decrease in the intracellular fluid
Hypertonic saline infusion causes no change
F
F
F
F
F
In the intracellular fluid
Thank You !