Hypokalamia/Hyperkalemia

Question 1

potassium predominantes in what fluid compartment?

Answer 1

• most common cation in the ICF (whereas sodium is the most common cation in the in the ECF)

Question 2

what is the effect of insulin on [K+] in the ICF/ECF?

Answer 2

insulin directly pumps K+ into cells, maintaining the high intracellular [K+]. this in turn stimulates the Na+/H+ antirpoter, promoting H+ secretion

Question 3

which patients should regularly have their potassium checked?

Answer 3

• patients with cardiac disease
  
  • both hypo/hyper - kalemia could have significant effects on cardiac conduction
  • K+ levels are critically important in patients with an MI, dysthrythmias, or receiving digoxin therapy
• patients receiving drugs that may effect K+ level
  
  • risk of hypokalemia - by loop diuretics
  • risk of hyperkalemia, with
    
    • k+ sparing diuretics
    • ACE inhibitors
    • NSAIDS
• patients with diabetes mellitus
  
  • acute DKA
  • type IV renal tubular acidosis
• patients with major fluid/electrolytice imbalances
  
  • those on IV fliuds
  • those receiving parenteral nutrition
  • tthose w/ severe diarhea
• patients with renal impairments

Question 4

what serum [K+] levels constitute hyperkalemia?

Answer 4

a serum [K+] > 5.5 mEq/L

Question 5

what to look out for during a physical exam a possibly hyperkalemic patient?

Answer 5

• exam will usually be negative
• otherwise, you may see
  
  • bradycardia
  • weakness, fatigue
  • dyspnea
  • arrthymias
  • parethesias
  • nausea and vomitting
  • muscle tenderness/weakness/paralysis
  • depressed or absent deep tendon reflexes

Question 6

discuss the pathophsyiology (common causes) of hyperkalemia?

Answer 6

• excessive intake of K+ (rare)
• decreased excretion of K+ (almost all of these causes involved decrease in aldosterone)
  
  • kidney disease (chronic or acute)
  • Addison’s disease:
    
    • characterized by a decrease in aldosterone production: less Na+ absorbed, less K+ secreted at collecting ducts –> K+ retention
  • Type IV RTA (Renal Tubular Acidosis)
    
    • ​this variation of RTA is due to an aldosterone deficiency.
    • K+ retention drives K+ out of the plasma in the cell. this promotes uptake reabsoprtion of H+ in “exchange for” the K+ we’re trying to get rid of
  • drugs:
    
    • diuretics that lower K+ secretion:
      
      • potassium sparing diruetics
      • ACEs/ARBS
        
        • (these lower inhibit Ang II and thus aldosterone production)
    • renin inhibitors
      
      • ​RAAS decrease –> aldosterone decrease –> K+ retention
• a shift of K+ from intracellular to the extracellular space
  
  • rhabdomyolsis - muscle breakdown
  • hemolysis - breakdown of RBCs
  • metabolic acidosis
  • drugs: beta blockers and alpha antagonists

Question 7

clinical presentation of rhabdomyolysis

Answer 7

• rhabdomyolysis = muscle breakdown that causes a causes a shift of K+ from the ICF to the ECF
• presentation:
  
  • myalgias
  • dark urine
  • possible compartment syndrome

Question 8

discuss the EKG changes seen in hyperkalemia

Answer 8

different EKG changes are seen dependent on the level of hyperkalemia (serum K+ > 5 mEq/L)

Question 9

how to check renal function for a hyperkalemic patient?

Answer 9

• determine the BUN and Creatinine
  
  • creatinine clearance = used to estimate GFR
    
    • can estimate creatinine clearance using the Cockcroft- Gault Formula (utilizes patient’s age and body weight)

Question 10

what can urine potassium levels you with regards to hyperkalemia?

how to obtain these urine levels?

Answer 10

• A urine K+ level <20 mEq/L suggests impaired renal excretion
• A urine K+ level > 40 mEq/L suggests intact renal excretory mechanisms
  
  • means that hyperkalemia is likely nonrenal

a spot urine K+ measurement is easiest to obtain

Question 11

outline the diagnosis of hyperkalemia based on serum [K+], luekocyte/platelet levels, and urine [K+]

Answer 11

Question 12

general treatment of hyperkalemia?

Answer 12

• Discontinue all drugs causing hyperkalemia (K+ sparing diruetics -spironlactone, eplernone, triamterine, amiloride - and trimethoprim)
• Discontinue any dietary potassium
• If pt on digoxin, check for digitalis toxicity—Hyperkalemia
  
  • In severe (potassium >7.0 mEq/L) OR if pt is symptomatic
    
    • Start treatment first!
    • Then look for underlying cause

in pharm, digoxin is contraindicated with loop/thiazide diuretics because it can “worsen hypokalemia” idk what to do about this.

Question 13

after intitial treatment for hyperkalamia (discotinuing K+ retaining drugs, ect.) what is the next step?

Answer 13

• next step is achieving membrane stabilization
  
  • ​calcium is key in stabilizing membrane stability (use either calcium chloride or calcium gluconate)
• next, want to drive K+ intracellullary:
  
  • this is often done with insulin, which drives K+ into cells.
    
    • if insulin is give, also administer glucose so pt doesnt beome hypoglycemic.
  • this can also be done with:
    
    • bicarbonate (especially if the patient is also acidotic)
    • magnesium
    • sympathonimetic agents (eg beta-agonists)
• we can also remove K+ from the body entirely:
  
  • hemodialysis
  • normal saline
  • furosemide (loop diuretic)
    
    • remember that loop diuretics increase the tubular Na+ load that arrives to the collecting ducts, which then drives Na+ reabsorption/K+ secretion
      
      • this promotes excretion of K+

Question 14

what blood serum is considered hypokalemia?

Answer 14

serum level < 3.5 mEq/L

Question 15

general causes of hypokalemia

Answer 15

• inadequate potassium intake
• increased potassium excretion (most common)
• shft of potassium from ECF to ICF

Question 16

clinical presentation of hypokalemia

Answer 16

• is identical to that of hyperkalemia. thus, clinical presentation alone is not enough to diagnose hypokalemia
  
  • generally, is asympotomatic
  • if symptomatic
    
    • weakness and fatigue*
    • muscle cramps
    • palpitations
    • worsening polyuria
    • psychosis, hallucinations

Question 17

what labs/serum levels should you obtain to diagnose hypokalemia?

Answer 17

• BMP/CMP
• magnesium assay
• ECG
• urine potassium

Question 18

what should we check to determine if a patient’s hypokelemia is due to extrerenal vs renal causes?

Answer 18

check urine K+

• if urine K+ is <20mEq/L, consider extrarenal causes
• if urine K+ is >20mEq/L, consider renal losses

Question 19

what are the common extrenal causes of hypokalemia?

Answer 19

• GI causes: diarrhea
• Use of laxatives, insulin, etc
• Low potassium intake (uncommon)

Question 20

what renal losses would cause hypokalemia?

Answer 20

HTN + alkalosis—-check aldosterone (check aldosterone b/c increased aldosterone would cause both HTN & K+ loss:

• Low aldo/ low renin: issue is increased cortisol: Cushing’s syndrome, Liddle’ ssyndrome
• High aldo/low renin: Primary aldosteronism
• High aldo/high renin: Secondary hyperaldosteronism

Normal/low BP or low—check acid-base

• Acidosis: Renal tubular acidosis 1 or 2
• Alkalosis: diuretics ,vomiting, Bartters yndrome, Gitelman syndrome

Question 21

• bartter syndrome causes what kind of hypokelmia?
• how does it present?

Answer 21

• causes hypokelamia via renal losses: (Uk > 20 mEq/L)
  
  • _​_urinary loss oss of Na+, Cl+, K+
  • presents with metabolic alkalosis WITHOUT HTN**
  • other things: hypochloremia, hyoreninemia

Question 22

gitelman syndrome

• what kind of hypokelemia does it cause?
• how does it present?

Answer 22

• causes hypokalemia due to renal losses (Uk > 20 mEq/L)
• presents with meatbolic alkalosis WITHOUT HTN - normal or low BP
• other things: hypokalmia, hypomagnesia, hypocalciuria

Question 23

what ECG changes are seen with hypokalemia?

Answer 23

• ST depression
• prominent U wave

Question 24

what arrythmias can result from hypokalemia?

Answer 24

• ventricular arrythmias
  
  • torsades de point
    
    • in this case, hypokalmia will be seen along with hypomagnesemia
  • ventricular tachycardia

Question 25

what are the three general steps we want to take when treating hypokalemia?

Answer 25

• reduce K+ losses
• replenish K+ stores
• correct Mg++

Question 26

how do we reduce K+ losses when treating hypokalemia?

Answer 26

• discontinue
  
  • loop/thiazide diruetics
    
    • if pt needs a diuretic, put them on a K+ sparing diuretic
  • laxatives
• treat diarrhea/vomitting if needed

Question 27

how do we replenish K+ stores when treating hypokalemia?

Answer 27

by supplying K+

• if K+ level 2.5-3.5 mEq/L: may only need oral potassium replacement
• if K+ level <2.5 mEq/L: they need IV potassium
  
  • for these patients, continuously monitor ECG

Question 28

when treating hypokalemia: after reducing K+ losses and replenishing K+ stores, what must we do next?

Answer 28

correct Mg+. bring Mg+ back to a normal level

Question 29

discuss the relationship between Mg+ levels and hypokalemia. what does this mean clinically?

Answer 29

• Mg depletion can cause potassium depletion
  
  • mechanism poorly understood: something to do with Mg+ loss impairing the ability of cell to maintain K+ (normally ECF [K+] very high)
• this means that repletion of cell potassium requires correction of magnesium deficit

Question 30

outline steps for determining cause of hypokalemia

Answer 30