Electrolytes Flashcards
what does PANIC stand for
positive anode negative is cathode
osmotic pressure
governs movement of water across semi-permeable membranes in response to solute concentration
Glomeruli in kidneys, capillary vessels
osmosis
movement of water through a selectively permeable membrane in order to equalize solute concentration
Moves from area of low concentration to area of high concentration
Osmolality
A physical property of a solution that is based on the concentration of solutes per kilogram solvent
Sodium is
primary cation in extracellular fluid
sodium reference interval urine and serum
135-145 mmol/L serum
40-220 urine
Hyponatremia
serum sodium less than 135mmol/L caused by increased loss, increased water retention or water imbalance
hyponatremia symptoms
125-130 is primarily GI
<125 is more severe neuropsychiatric symptoms like nausea, vomiting, lethargy and ataxia
hypernatremia
increased serum Na. Excess water loss, decreased intake and increase Na intake
hypernatremia symptoms
CNS, altered mental status, lethargy, irritability, restlessness, seizures, muscle twitching, nausea and vomiting
Measurement of urine osmolality to determine hypernatremia cause
Renal water loss = low osmolality
Extrarenal water loss = osmolality is increased
Potassium
Primary intracellular cation. Concentration is maintained by ATPase pumps. Has major effects on skeletal and heart muscle
Potassium reference interval
3.5-5.1 mmol/L (serum)
Is there a difference between serum and plasma/whole blood potassium?
yes, serum is 0.2-0.5mmol/L higher. because of hemolysis
Hypokalemia
decreased K+ concentration caused by diuretics, GI loss, renal loss
hypokalemia symptoms
weakness, fatigue, muscle weakness
Hyperkalemia
increased K+ concentration, usually in people with an underlying condition like renal insufficiency, diabetes or metabolic acidosis
hyperkalemia symptoms and treatment
Symptoms: muscle weakness, tingling, numbness and mental confusion, cardiac arrythmias and possible cardiac arrest.
Treatment: IV K+ solution
Ion selective electrode
membrane permeability only to select anions/cations. Potential is produced proportional to ion concentration
Chloride
primary extracellular anion excreted at kidneys
chlorine reference interval
98-107mmol/L
common measurement of chloride
ISEs
Chloride sweat analysis
differential diagnosis for cystic fibrosis. It is usually done with newborn screening.
Steps:
1. sweat stimulation
2. sweat collection (30 min)
3. sweat analysis
Bicarbonate HCO3 measurement
measure via production of carbon dioxide following acidification (ISE) or alkalinization
Bicarbonate reference range
23-29mmol/L
Anion gap
difference between the sum of the measured cations and the sum of the measured anions
anion gap reference range
7-16mmol/L
Elevated AG causes
uremia/renal failure, ketoacidosis, methanol, ethanol, ethylene glycol, salicylate poisoning, lactic acidosis, instrument error
low AG
rare but seen in hypoalbuminemia and severe hypercalcemia
Plasma/urine osmolality equation
mOsmol/kg = 1.86 [Na+] + glucose/18 + urea/2.8 + 9
Osmolal gap reference interval
5-10 mOsm/kg
osmolal gap equation
measured osmolality – calculated osmolality
What does the osmolal gap tell us
tells us about the presence of exogenous osmotic substances, and measures osmolality with freezing point depression or vapor pressure
what causes increased osmolal gap
ethylene glycol, methanol, isopropanol, lactate, beta hydroxybutyrate
