[PCL] Hyperkalemia
Physiology of Potassium
Major intracellular cation
98% of potassium found in the body is in the cell
2% found in extracellular fluid
All cells maintain a negative voltage in the cell interior (-40 to -80 mV) which creates membrane potential
Difference in electric potential between the interior and the exterior of the cell
Membrane potential functions
Provides power to the molecular devices within the cells
Helps transmit signals to another part of the cell
Action potential in nerve cells
Depolarization
Ion channels open and allows electricity to flow (cell interior becomes less negative quickly)
Sodium/Potassium Pump maintains the balance of negative ions (aka potassium) inside the cell compared to outside the cell
Too much extracellular potassium leads to less of a membrane potential (cell exterior and interior match more closely)
Makes it easier for depolarization to happen
Causes cardiac cells to be more excitable and leads to potentially lethal arrhythmias
Causes of Hyperkalemia
Shifting of Potassium Out of the Cell
Acidosis
Diabetes Mellitus
Acute Cell Tissue Breakdown (rhabdo, hemolysis, massive transfusion)
Drugs: Digoxin, Beta Blockers (especially non selective ones)
Impaired renal elimination of potassium
Renal insufficiency
Hypoaldosteronism
Medications that interfere with potassium excretion
K sparing diuretics (spironolactone, NSAIDs, and ACEI/ARBs)
Congestive heart failure (or the drugs associated with them: BB, ACEI)
Constipation
Increased intake of potassium
With normal renal function it takes large amounts
With impaired renal function a smaller increase in potassium can cause severe hyperkalemia
Signs and Symptoms of Hyperkalemia
Rarely associated with symptoms
Some patients can complain of nausea, muscle pain, or parathesias
If patients are symptomatic; always check an EKG
EKG Changes in Hyperkalemia
First: Tall, peaked T waves
Second: Flattening of the p wave and prolongation of PR interval
Can see bradycardia and AV block
Third: Broad QRS Complexes
Eventually becomes a sine wave; cardiac arrest and Vfib are imminent
Treatment of Hyperkalemia: Emergency
How urgent do you need therapy?
Treat it urgently if you have EKG changes or the patient is symptomatic
Calcium is your mainstay treatment in emergent hyperkalemia
Calcium makes outside the cell more positive and increases the gradient of electrical charge so cells aren’t able to depolarize as easily
1-3 minutes to take effect
Only lasts 30-60 minutes
Which type of Calcium?
Calcium Gluconate preferred because calcium chloride has a higher concentration of calcium and you want to avoid calcium toxicity
Calcium gluconate is safe to give peripherally
Calcium chloride can cause tissue necrosis and can be irritating to peripheral veins
Calcium is in; now what?
Rapidly remove potassium from the body
Hemodiaylsis
Treatment of Hyperkalemia: Non-emergent
Shift Potassium into the cells (don’t affect total body potassium)
Fluids
Dilutes total body volume and treats pre-renal AKI
D50 + Insulin
Insulin shifts potassium out of the vascular space and into the cells
D50 given to prevent hypoglycemia
Sodium Bicarbonate
Reversing acidosis which shifts potassium out of the cells (only works if the patient is acidotic)
Albuterol
Shifts potassium back into cells
Additive to insulin
Takes about 15-30 minutes to work, lasts 2-3 hours
10 mg continuous neb (not the usual 2.5 mg)
Remove potassium from the body
Loop diuretic
Increases renal excretion of potassium (only effective if kidneys are working)
Kayexelate (sodium polystyrene sulfonate)
Removes potassium from the gut in exchange for sodium
Takes 1-2 hours to work
Lasts 4-6 hours
Associated with bowel necrosis and sodium retention
Summary
Hyperkalemia is defined as a potassium > 5.5 outside the cell
caused either by intracellular shift of potassium outside the cell, decreased renal excretion of potassium or increased exogenous intake of potassium
patients are typically asymptomatic but when it’s not, it’s usually life threatening and associated with EKG changes
Calcium is used to stabilize the heart by making the outside of the cell more positive and shifting the membrane potential closer to normal
For life threatening hyperkalemia, stabilize the myocardial membrane potential with calcium then rapidly remove potassium with a measure such as dialysis
In a patient with hyperkalemic arrest you can use albuterol with insulin/d50 to rapidly shift potassium inside the cell
To remove potassium from the body more slowly you can use Lasix (a loop diuretic) in patients with good renal function or kayexlate to remove potassium via bowel excretion – but both take longer to work
Attribution
“Fantasy", "Chimera", "Charmed”, “Skepto”, “Sunday Afternoon”, “Trader Ho Hey”, “Love Sprouts” and “Lucky Charms” by Podington Bear is licensed under CC BY-NC 3.0 / Song has been decreased in length from original form