FLUIDS AND ELECTROLYTES Flashcards
At birth, TBW constitutes about ??, thereafter, it declines to about ?? by the end of infancy
75-80% of body weight,
about 60% and remains so
The total body water (TBW) in early fetal life is
about 90%
Intracellular compartment contains what percent of TBW
(2/3rd of TBW, 30-40%)
Extracellular compartment contains what percent of TBW
(1/3rd of TBW,20-25%)
The extracellular fluid (ECF) is further distributed into ?
intravascular space as plasma water (5%) and also into the extravascular (interstitial) space (15%)
TBW in males remains at 60%, but TBW in females decreases to approximately ?? WHY?
in females decreases to approximately 50% of body weight.
Because, At puberty, there is increased muscle mass of males and more body fat in females, fat has very low water content and muscle has high water content.
Is difference in the ECF volume between post-pubertal females and males.?
There is no significant difference in the ECF volume between post-pubertal females and males.
what forces are responsible for the MAINTENANCE OF FLUID BALANCE?
The equilibrium between the intravascular fluid and the interstitial fluid is a product of the balance of hydrostatic, osmotic and oncotic forces, this is necessary for proper tissue perfusion
Q
describe Hydrostatic pressure and what happens in Decreased HP?
The hydrostatic pressure (HP)of the intravascular space is due to the pumping action of the heart
HP drives fluid out of the intravascular space into the interstitial space at the arterial ends of the capillaries.
Decreased HP e.g in heart failure causes movement of fluid into the venous ends of the capillaries.
what force determines the distribution of water between the compartments
Osmotic forces due to electrolytes in body fluid is important in determining the distribution of water between the compartments
Each compartment has one major solute, which because of its restriction within the compartment acts to hold water within it
Water moves along osmotic gradient from compartment of ?? to that of ?? until an equilibrium is reached.
of low osmolality
of high osmolality until an equilibrium is reached
describe WATER BALANCE
In the steady state, water intake must equal water output
Maintenance fluid is the fluid required to keep an individual in homeostasis or steady state
Water loss is usually via evaporation from the skin and respiratory tract (insensible loss) , sweat, urine and stool
Net water intake is derived from ingested water, from food and water produced from oxidation
Plasma osmolality and water balance;
Plasma osmolality is determined by?? and is normally maintained within a narrow limit of??
by plasma sodium ion conc
and is normally maintained within a narrow limit of (285-295mOsm/kg)
Plasma osmolality and water balance;
The regulatory system is governed by ?? which influence??
by osmo-receptors in the hypothalamus
which influence both thirst and secretion of anti diuretic hormone (ADH)
how can Plasma osmolality be measured??
Plasma osmolality can be measured directly using osmometers as well as indirectly by estimation by calculation.
whats the formula to measure Plasma osmolality??
Plasma osmolality=2(Na+) +glucose/18 + BUN/2.8
what is osmolal gap and Increase osmolal gap may occur due to?? examples of condition with Increase osmolal gap??
Measured values are generally greater than calculated value by 10mOsm/kg, this is osmolal gap
Increase osmolal gap may occur due to increased unmeasured osmoles e.g Hyperglycaemia, mannitol , ethanol
In children with hypoalbuminemia, the decreased oncotic pressure of the intravascular fluid contributes to
the development of edema
Six (6) Disease states that disrupt the body water balance include;
Hypoalbuminaemia
heart failure
renal impairment
Sequestration of fluid in third space/ interstitial space
Burns
Haemorrhage
Whats an electrolyte?? list examples, and general function?
An electrolyte is a substance that dissociates into ions in solution and acquire the capacity to conduct electricity
Sodium, potassium, bicarbonates, chloride, calcium, magnesium and phosphates are examples of electrolytes
The blood electrolytes—sodium, potassium, chloride, and bicarbonate—help regulate and maintain acid-base balance and water balance
what are the dominant cation and anion in the ECF??
the most abundant cation in the ICF??
the most abundant anions in the ICF??
Sodium and chloride are the dominant cation and anion, respectively, in the ECF.
Potassium is the most abundant cation in the ICF.
Proteins, organic anions, and phosphate are the most abundant anions in the ICF
Electrolyte balance
The amount of fluid in a compartment depends on ?? If the electrolyte concentration is high,?? if the electrolyte concentration is low??
The amount of fluid in a compartment depends on concentration of electrolytes in it. If the electrolyte concentration is high, fluid moves into that compartment (osmosis). Likewise, if the electrolyte concentration is low, fluid moves out of that compartment.
How does The kidneys help maintain electrolyte concentrations??
The kidneys help maintain electrolyte concentrations by filtering electrolytes and water from blood, returning some to the blood, and excreting any excess into the urine.
hyponatremia definition
The normal blood level of Na varies between 135-145mmol/l
Hyponatremia is defined as Na conc below 135mmol/l.
Etiology of hyponatremia? depends on?
The etiology of hyponatremia depends on the volume status of the patient;
VOLUME DEPLETION (CCF, Diarrhoea, diuretics) —–>
Decrease in effective circulating volume —–>
Reduced GFR and increase in salt and water reabsorption by the proximal convoluted tubule+ secretion of ADH —–>
Increased water reabsorption from the collecting tubules and subsequent hyponatremia
