Electrolytes
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Anions move toward anode or cathode?
Anode
Cations move toward anode or cathode?
Cathode
Na, Cl, K are important for which processes?
Volume + osmotic regulation
K, Mg, and Ca are important for which processes?
Mycocardial rhythm and contractility
Mg, Ca, and Zn are important cofactors for what?
Enzyme activation
Ca and Mg are important for which process?
Blood coagulation
Water Percent body wt? How much in intra/extracellular compartments? How is it controlled?
• 40-75% of human body wt • 2/3 intracellular and 1/3 extracellular • Controlled by maintaining electrolyte/protein concentration in compartments
Osmolality Definition?
• Physical property of solution based on concentration of solute (mmol) per kg solvent (w/w) • Related to changes in properties of solution relative to pure water (decrease in fp and vapor pressure)
Osmolality Clinical significance?
• Hypothalamus responds to it • Affects plasma sodium conc. • Regulation of sodium + water controls blood volume
From which specimen(s) do we measure osmolality?
Serum or urine
Anti-diuretic hormone (ADH) is now called _____ Function?
• Arginine vasopressin (AVP) hormone • Functions to promote water reabsorption in renal tubule of kidneys (aka stimulates thirst)
Diabetes insipidus General mechanism? Symptom?
• Pituitary gland produces insufficient AVP, meaning body can’t reabsorb water, so that water gets excreted into lots of urine • Symptom: constant thirst
Function of Renin-Angiotensin-Aldostorone System?
Helps control blood pressure
Other factors affecting blood volume
• Atrial natriuretic peptide released by myocardial atria in response to vol expansion->promotes Na and water excretion • Volume receptors independent of osmolality stimulate AVP release • GFR increases with overhydration (vol expansion) and decreases with dehydration (vol depletion) • Increase in plasma sodium increases urine sodium and water excretion, and vice versa (ceterus paribus)
How to calculate osmolality?
• Uses glucose, BUN, and Na values • (2 X Na) + (glucose/20) + (BUN/3)
How to calculate osmolal gap?
• Gap= Measured osmolality - calculated osmolality • Gap should be less than 5-10
Define osmolal gap
Difference between calculated and lab-determined osmolality
Sodium ion Percent of extracellular fluid (ECF)? Determines what parameter of plasma? Conc. in ECF compared to intracellular? How to prevent sodium equilibrium?
• 90% ECF • Largely determines plasma osmolality • ECF Na+ > Intracellular Na+ • ATPase ion pumps (active transport) prevents sodium equilibrium
How is sodium ion regulated?
• Intake of water in response to thirst • Water excretion • Blood volume status
Sodium Reference Range
135-145 mmol/L
Serum sodium levels in hyponatremia
Sodium < 135 mmol/L Sodium < 120 mmol/L clinicaly sig
Serum sodium levels in hypernatremia
Sodium > 145 mmol/L Sodium > 160 mmol/L leads to death
Specimens for sodium measurment?
• Serum • Plasma • Whole blood • Urine • Sweat
Common symptoms in hyponatremia Na+ btwn 120-135 mmol/L?
• Headache • Nausea • Vomiting • Fatigue • Confusion • Muscle cramps