Chapter 5 - Water balance

Question 1

what is the composition of total body water?

Answer 1

Non water = 40%
Intracellular fluid = 40%
Interstital fluid = 15%
Plasma volume = 5%

TBW = ICF (2/3) + ECF ( 1/3)
ECF = interstitial + intravascular ( plasma fluid)it

Question 2

What are the effectors of volume regulation?

Answer 2

1 - Renin Angiotensin Aldosterone system
2 - Atrial Natriuretic Peptide
3 - Others –> Vasopressin, prostaglandins, doperminergic receptors, alpha adrenergic receptors, thirst mechanism, intrinsic renal properties.

Question 3

Electrolyte composition of ICF

Answer 3

High in Potassium, organic Phosphates and proteins

Question 4

Electrolyte composition of ECF

Answer 4

High on Sodium, Chloride and Bicarbonate

Question 5

Permeability of ions varies in different organs. which organ is highest and lowest permeable?

Answer 5

Highest permeability: Liver

Lowest permeability: Brain

Question 6

What is osmolality?

Answer 6

It is the solute concentration in a fluid.

Measured in milli osmoles per kilogram of water ( mOsm/Kg)

Question 7

What is the osmolality of Plasma?

Answer 7

• Measured using Plasma sodium concentration, which is normally 285 - 295 mOsm/Kg

Question 8

Formula to calculate plasma osmolality

Answer 8

plasma osmolality = 2(Na) + glucose/18 + BUN/ 2.8

• it can be measured directly using osmometers
• measured value is higher than calculated by 10mOsm/kg

Question 9

maintenance fluid requirement in healthy children

Answer 9

0-10Kg –> 100ml/kg/day = 4ml/kg/hour
10-20Kg –> 1000ml + 50ml/kg/day = 40ml + 2ml/kg/hour
>20kg –> 1500ml + 20ml/kg/day = 60ml + 1ml/kg/hour

Question 10

signs of No dehydration

Answer 10

Decrease in body weight – < 5% in infants
< 3% in children
Mental status –> Normal
Thirst –> Normal
Skin color and elasticity (turgor) –> Normal
Sunken eyes –> normal
Mucous membrane –> Normal
Pulse rate –> Normal
CRT –>2-3 seconds
Blood pressure –> normal
Urine output –> slightly decreased.

Question 11

Signs of Some Dehydration

Answer 11

Decrease in body weight – < 5-10% in infants
< 3 - 6% in children
Mental status –> Irritable
Thirst –> Increased
Skin color and elasticity (turgor) –> Cool, pale, mild delay in turgor
Sunken eyes –> sunken
Mucous membrane –> Dry
Pulse rate –> Slightly Increased
CRT –> 3 - 4 seconds
Blood pressure –> normal
Urine output –> decreased.

Question 12

Signs of Severe Dehydration

Answer 12

Decrease in body weight – >10% in infants
>6% in children
Mental status –> Lethargic to Comatose
Thirst –> Unable to drink
Skin color and elasticity (turgor) –> cold, mottled, tenting
Sunken eyes –> very sunken
Mucous membrane –> very Dry
Pulse rate –> Tachycardia
CRT –> >4 seconds
Blood pressure –> normal or low
Urine output –> oliguria, anuria

Question 13

Correction of water deficit

Answer 13

1 - In shock , compensated shock or severe dehydration –> Rapid infusion of isotonic fluids of 1-3 boluses at 20ml/kg (Isotonic saline or Ringer lactate )
2 - Fluid to replace calculated / observed volume deficit
Fluid required = 10ml for each percentage weight loss
If pre-dehydration weight known = 1 litre for every Kg weight loss
3 - Provide fluid and electrolyte to replace the amount lost in normal daily metabolism ( maintenance fluid)
4 - Provide enough fluid to replace ongoing losses of various body fluids

Question 14

Electrolyte composition of body fluids : Gastric

Answer 14

Na = 60-100 mEq/l
K = 5-20 
Cl = 90-130
HCO3 = 0

Question 15

Electrolyte composition of body fluids : Small Intestine

Answer 15

Na = 80-140 mEq/l
K = 5-15 
Cl = 90-140
HCO3 = 40

Question 16

Electrolyte composition of body fluids : Colon

Answer 16

Na = 60 mEq/l
K = 30 
Cl = 40
HCO3 = 15

Question 17

Electrolyte composition of body fluids : Pancreas

Answer 17

Na = 135 - 145mEq/l
K = 5-10
Cl = 70-90
HCO3 = 95-120

Question 18

Electrolyte composition of body fluids : Diarrhea

Answer 18

Na = 10-90mEq/l
K = 10-80
Cl = 90-130
HCO3 = 40