Fluids and Electrolytes Flashcards
What proportion of body weight is water?
45-65%
____________ ________ comprises two-thirds of water weight.
Intracellular fluid
Extracellular fluid makes up ____-______ of water weight.
One-third
_________ is one quarter, and interstitial fluid is three quarters of the extracellular fluid.
Plasma
Extracellular fluid loss may be due to acute ______ _____, vomiting, and diarrhoea.
Blood loss
State two ways by which extracellular fluid can be gained.
IV fluid overload and heart failure
What is the homeostatic response of changes in extracellular fluid?
Changes in plasma volume, or osmotic concentrations
The concentration of solutes per kilogram of solvent (mOsm/kg H2O) is ____________.
Osmolality
‘Normal’ plasma osmolality is 2__ - 295 mOsm/kg.
85
__________ osmolality is from 300 - 900 mOsm/kg.
Urine
_________, and its associated anions, account for most of the osmotic activity of plasma.
Sodium
___________ is regulated by changes in water balance.
Sodium
___________ is regulated by changes in sodium balance.
Volume
Measurement of osmolality is done by osmometer, and based on freezing point or ___________ ______________.
Vapour depression
State the formula for calculated osmolality.
2 x [Na+] + [urea] + [glucose]
__________ _____ are caused by the difference between measured and calculated osmolality.
Osmolal gaps
Osmolality - ___________ ___________ = osmolal gap
Calculated osmolality
GFR Increases with volume expansion, and decreases with volume ___________.
Depletion
What is the role of atrial natriuretic peptide?
Promotes sodium excretion by the kidney
True or false: in water excess, ADH secretion and thirst are suppressed.
True
Hypernatraemia occurs during _______ ___________.
Water depletion
___________ dehydration can be caused by GI losses, inadequate fluid intake, etc..
Isotonic
___________ dehydration results from diuretic drugs, osmotic diuresis, etc..
Hypertonic
__________ dehydration can be derived from GI losses, and high-sodium sweat (as seen in cystic fibrosis).
Hypotonic
Give two causes of high osmolality.
Hyperglycaemia and increased urea
______________ are ions that are capable of carrying an electric charge, and may be positive or negative.
Electrolytes
List four functions of electrolytes.
Volume and osmotic regulation (Na, K, and Cl)
Acid-base balance (HCO3, K, Cl)
Neuromuscular excitability (K, Ca, and Mg)
Myocardial rhythm and contractility (K, Mg, and Ca)
True or false: electrolytes are often measured in conjunction with sodium and urea.
True
What is the plasma reference range for sodium?
135 - 145 mmol/L
Hyponatraemia is decreased plasma _________.
Sodium
Increased sodium loss may be due to _______________, potassium deficiency, diuretic use, ketonuria, prolonged D&V, or salt-losing nephropathy.
Hypoadrenalism
__________________ may be due to hyperlipidaemia, or hyperproteinaemia.
Pseudohyponatraemia