Potassium Flashcards
Normal range of potassium in the ECF
3.5–5.0 mmol/L.
Most of the body’s potassium is in the:
ICF
What regulates potassium in and out of cells?
The sodium-potassium pump
The ratio of ECF to ICF potassium is critical for:
Resting membrane potential of neurons and muscle cells.
Transmission and conduction of nerve impulses.
Maintenance of normal cardiac rhythms.
Skeletal and smooth muscle contraction.
What is the primary source of potassium intake:
Diet
Main route for potassium excretion:
Kidneys
Factors influencing potassium excretion
Sodium retention, increasing potassium loss
Large urine volume, can cause excessive potassium excretion
Kidney dysfunction
Factors causing K+ to move from ECF → ICF (resulting in hypokalemia)
Insulin - promotes potassium uptake by cells
Alkalosis - H+ ions leave cells, and potassium enters to maintain charge balance
B-adrenergic stimulation (e.g. catecholamine release in stress) - activates sodium-potassium
Factors causing K+ to move from ICF → ECF (resulting in hyperkalemia)
Acidosis - H+ ions enter cells and potassium exists to maintain charge balance
Trauma to cells - releases intracellular potassium
Exercise - causes temporary potassium release from muscle cells.
What is the most common cause of hyperkalemia?
Renal failure
Why is hyperkalemia common in patients with massive cell destruction (e.g., burn or crush injury, tumour lysis)
Cells rupture and potassium is leaked into the bloodstream
Adrenal insufficiency leads to which imbalance of K+?
hyperkalemia
What may be the first symptoms of hyperkalemia?
Leg cramping
Three broad categories of causes of hyperkalemia
Excessive potassium intake
- Excessive/rapid parenteral administration
- Potassium-containing drugs
- Potassium-containing salt substitutes
Shift of potassium out of the cells
- Acidosis
- Tissue catabolism (e.g. sepsis, burns)
- Crush injury
Failure to eliminate potassium
- Renal disease
- Potassium-sparing diuretics
- Adrenal insufficiency
- ACE inhibitors
Three broad categories of causes of hypokalemia
Potassium loss
- GI losses
- Renal losses
- Skin losses
- Dialysis
Shift of potassium into cells
- Increased insulin
- Alkalosis
- ↑ epinephrine
Lack of potassium intake
- Starvation
- Diet with low K+
- Failure to include K+ in NPO patient
Clinical manifestations of hyperkalemia
Irritability
Anxiety
Abdominal cramping + diarrhea
Weakness of lower extremities
Paresthesias “pins & needles”
Irregular pulse
Cardiac standstill if hyperkalemia is sudden/severe
High & tight
Clinical manifestations of hypokalemia
Fatigue
Muscle weakness
Leg cramps
N+V
Flabby muscles
Decreased reflexes
Weak, irregular pulse
Polyuria
Hyperglycemia
Low & slow
Treatment of hyperkalemia
Eliminate oral and parenteral potassium intake
Increase elimination of potassium
- Diuretics
- Dialysis
- Increased fluid intake can enhance renal potassium elimination
Forcing potassium from the ECF → ICF
- Administration of IV insulin (along with glucose so the patient doesn’t go hypoglycemic)
- Administration of IV sodium bicarbonate in the correction of acidosis
Reversing the membrane effects of the elevated ECF potassium by administering calcium gluconate IV
- Calcium ions can immediately reverse the effect of the depolarization of cell excitability
Most common cause of hypokalemia
Abnormal losses of potassium via either the kidneys or the Gi tract
Hypokalemia; losses through kidneys and GI tract
Kidneys
- elevated diuresis; elevated aldosterone levels
GI tract
- Diarrhea
- Laxative abuse
- Vomiting
- Ileostomy drainage
Treatment of hypokalemia
Treat the underlying cause
Examples of underlying cause of hypokalemia
Vomiting, chronic diarrhea, or both
Certain medications
Excessive sweating (Does the pt have CF?)
Undereating or malnutrition
Kidney disease, diabetic ketoacidosis
When restoring K+ in hypokalemia, we can use __ or __
IV medication or increase dietary intake
Safety Alert for KCl IV
Must always be diluted
Never give KCl via IV push or in a concentrated bag
IV bags should be inverted several times to ensure even distribution in the bag
Never give KCl to a hanging bag, to prevent bolus dose
