Potassium Flashcards
What is the most abundant intracellular cation?
Potassium
What is the daily requirement of K+ needed to maintain a normal serum concentration?
40-80 mEq
What is the normal range for potassium?
3.5-5
How is potassium excreted?
90% renal excretion
True or false. The potassium level is affected by acid-base disorders. Why or why not?
True. Because of the H-K exchange (when H+ increases, K+ is pulled from the cell and into the blood stream and when H+ decreases K+ is pulled into the cell)
Acidosis can cause _______kalemia.
HYPERkalemia
Alkalosis can cause _______kalemia
hypokalemia
What are 3 hormones that can affect potassium balance?
insulin
catecholamines
aldosterone
How does insulin affect potassium?
When insulin is secreted, K+ is pulled INTO the cells and serum K+ levels decrease
How is hypokalemia classified?
K+ < 3.5 mEq/L
What is mild hypokalemia?
K+ between 3.1-3.4
What is moderate hypokalemia?
K+ between 2.5-3.0
What is severe hypokalemia?
K+ < 2.5
What are some causes of hypokalemia?
- poor dietary intake
- large renal or GI loss (diuretics, especially Loops)
- Intracellular shift (alkalosis, insulin admin, glucose admin, beta agonists)
- Low Magnesium
Why can low magnesium cause low potassium?
Mg2+ is the cofactor for the exchange of K+ in the body so if Mg2+ is low, K+ won’t be able to stay stored intracellularly and will be renally excreted more rapidly.
What are types of drugs that can cause hypokalemia?
Drugs that cause a transcellular shift
Drugs that enhance renal excretion of K+
Drugs that enhance fecal elimination of K+
What are some examples of drugs that can cause a transcellular shift of K+ resulting in hypokalemia?
- B2-receptor agonists (albuterol)
- Tocolytic agents (ritodrine, nylidrin)
- Theophylline
- Caffeine
- Insulin overdose
What are some examples of drugs that can enhance renal excretion of K+?
- Diuretics
- High dose penicillins
- Mineralcorticoids
- Aminoglycosides
- Amphotericin B
- Cisplatin
What are some examples of drugs that can enhance fecal excretion of K+?
Laxatives (sugar is also a laxative)
• sodium polystyrene sulfonate
• phenolphthalein
• sorbitol
What is the clinical presentation of moderate hypokalemia?
Cramps
Muscle weakness
Malaise
What is the clinical presentation of sever hypokalemia?
EKG changes • flattened T waves • ST segment depression • PR prolongation Bradycardia Heart block Arrhythmias: atrial flutter, PVCs, V fib
What drug do you need to watch or monitor if a patient has hypokalemia?
Hypokalemia can cause DIGOXIN toxicity
(b/c K+ and Dig share the same receptor and if K+ is low, more dig binds to the receptor which increases its activity and can cause toxicity)
What are some non-drug therapies that you can do to treat hypokalemia?
- dietary replacement of K+
- D’C the offending agent
- Correct the underlying cause
What electrolyte may you need to correct if K+ is low and not increasing even with treatment?
Magnesium
If the K+ < 3.5, a 1 mEq/L drop is equal to a loss of ____ mEq
200 mEq
If the K+ < 3, a 1 mEq/L drop is equal to a loss of ____ mEq
200-400 mEq
What equation helps you know how many mEq of K+ need to be replaced?
(4 - K+serum) x 100
How do you treat mild to moderate hypokalemia?
with ORAL preps
If a pt is on diuretic and has low K, how many mEq/day are needed to replace their K+?
40-100 mEq/day
Which of the following disintegrates better in GI tract and has fewer erosions?
A. Wax-matrix ER tablets
B. Controlled-release micro encapsulated tablets
C. Potassium chloride elixer
B
Which of the following is inexpensive, has poor compliance, poor taste and immediate effect?
A. Controlled-release micro encapsulated tablets
B. Potassium chloride elixir
C. Wax-matrix ER tablets
D. Potassium chloride effervescent tablets for solution
B. potassium chloride elixir
Which of the following is more expensive but convenient for people who have trouble swallowing?
A. Controlled-release micro encapsulated tablets
B. Potassium chloride elixir
C. Wax-matrix ER tablets
D. Potassium chloride effervescent tablets for solution
D. Potassium chloride effervescent tablets for solution
Which of the following has fewer erosions than wax-matrix tablets?
A. Controlled-release microencapsulated tablets
B. Potassium chloride elixir
C. Encapsulated CR microencapsulated particles
D. Wax-matrix ER tablets
C. Encapsulated CR microencapsulated particles
If a patient has acidosis and hypokalemia, what are the treatment options?
potassium acetate (IV) potassium bicarb (IV or PO)
If a patient has alkalosis and hypokalemia, what are the treatment options?
potassium chloride (IV or PO)
If a patient has low phosphorus and hypokalemia, what are the treatment options?
potassium phosphate (IV or PO)
How do you treat severe hypokalemia?
with IV potassium in a SALINE prep
Why do you not give K+ in a D5W solution?
D5W has sugar in it and sugar increases insulin release and pulls more K+ inside the cells and out of the blood stream which worsens the hypokalemia
What is the max concentration for K+ in an IV bag?
80 mEq/L
What is the max rate you can run IV K+ at in a peripheral line?
10 mEq/h
What is the max rate you can run IV K+ at in a central line?
40 mEq/h
Why do we care about max rate of admin?
it can be damaging or irritating to peripheral veins
How is hyperkalemia classified?
K+ > 5 mEq/L
How is mild hyperkalemia classified?
K+: 5.1 - 5.9
How is moderate hyperkalemia classified?
K+: 6-6.9
How is severe hyperkalemia classified?
K+ > 7 mEq/L
What are some causes of HYPERkalemia?
increased intake • dietary potassium (salt substitutes) • drug-induced pseudohyperkalemia • lab error • hemolysis of the sample
What are some drugs that can cause HYPERkalemia?
IV fluids K-sparing diuretics ACEI/ARBs NSAIDs Heparin Bactrim
What is the clinical presentation of HYPERkalemia?
Muscle weakness Paresthesias Hypotension EKG changes • peak T waves with level > 6 mEq/L • widened PR interval • widened QRS complex Arrhythmias Acidosis
What are some treatment goals for HYPERkalemia?
- antagonize adverse cardiac effects
- reverse symptoms present
- return serum K+ to normal
- return total body stores to normal
- identify underlying cause and correct
What are some non-drug treatments for HYPERkalemia?
D’C the offending agent
Hemodialysis if nothing else works
If the pt has HYPERkalemia with EKG changes what meds do you give them first?
Calcium Gluconate 1 g IV in D5W over 5-10 minutes to stabilize the heart and prevent arrhythmias
What is the onset and duration of action for calcium gluconate?
1-2 min/30 min
What do you need to look out for when giving a patient Calcium gluconate?
iatrogenic hypercalcemia (make sure to check for ionized calcium with the equation from the total calcium lab)
What is the equation to find out ionized calcium?
…
What does iatrogenic mean?
“we (the healthcare providers) did it to the patient”
What is ionized Ca2+?
the free number of Ca2+ in the bloodstream NOT bound to albumin
Why do you give regular insulin to combat hyperkalemia?
it is a temporary fix that shifts K+ INTO the cell and out of the plasma
How many units do you give of regular insulin to treat hyperkalemia?
5-10 units IV bolus
*usually 10 units are given
(if the patient has metabolic acidosis, they may need an insulin infusion) Why?
Why do you give dextrose IV push or infusion with regular insulin?
The dextrose stimulates insulin secretion and helps offset hypoglycemia caused by the insulin given.
What percentage of dextrose do you give with insulin?
10-50%
What is the onset and duration of action for the insulin/dextrose combo?
onset: 30 min
duration: 2-6 h
Why do you give albuterol for hyperkalemia?
to shift K+ into the cell
What is the dose for albuterol given for hyperkalemia?
10-20 mg nebulized over 10 min
What are the side effects of albuterol?
tachycardia, jittery, irritable
What should you monitor when a patient is given albuterol?
monitor HR
What is the problem with giving albuterol for hyperkalemia?
it doesn’t have a predictable response and many people have a poor response to it
What is the dose of Na bicarbonate used for hyperkalemia?
50-100 mEq IV over 2-5 min
