Electrolyte 1: Hypokalemia

What is the normal range of sodium?

• 135-145 mEq/L

What is the normal range of Chloride?

• 98-107 mEq/L

What is the normal range of potassium?

• 3.5-5 mEq/L

What is the normal range of phosphorous?

• 2.7-4.5 mg/dL

What is the normal range of magnesium?

• 1.6-2.4 mg/dL

What is the normal range of calcium?

• 8.4-10.2

The intracellular compartment is how much TBW? What is it determined by?

• ICF (intracellular fluid), 60% of TBW

• ICF osmolarity is determined by concentration of potassium and its anions (mostly organic and inorganic phosphates)

The extracellular compartment is how much TBW? What is it determined by?

• 40% of TBW

• Sodium and its accompanying anions (chloride and bicarbonate) comprise more than 90% of the total osmolarity of the ECF

What is the most abundant cation in the body?

• Potassium

What is responsible for the compartmentalization of potassium?

• Sodium-potassium adenosine triphosphate (Na+/K=/ATPase) pump

  • The pump is an active transport system that maintains increased intracellular stores of potassium by transporting sodium out of the cell and potassium in the cell w/ ratio 3:2

What is hypokalemia?

• <3.5 mEq/L

How do beta receptor agonists+catecholamines (epinephrine, albuterol, terbutaline, pseudoephedrine) induce hypokalemia?

• Intracellular shift

How does insulin induce hypokalemia?

• Intracellular shift

How do Thiazides induce hypokalemia?

• Renal loss

How does Loop diuretics induce hypokalemia?

• Renal loss

How does Penicillin induce hypokalemia?

• Renal loss

How do laxatives induce hypokalemia?

• GI loss

How does Alkalosis induce hypokalemia?

• Intracellular shift and renal loss

In Hypokalemia, what causes GI tract loss?

• Vomiting

• Diarrhea

In Hypokalemia, what drugs cause it?

• Thiazide

• Loop diuretics

• Osmotic diuretics

• Penicillin

In hypokalemia, what causes intracellular shift?

• Alkalosis

• Excess catecholamine, beta-2 receptor agonists

• Insulin overdose

Does beta receptor agonist change the concentration of potassium inside the TBW?

• TBW is intracellular+extracellular

• NO

When aldosterone is activated, what is the effect on Sodium and Potassium?

• Reabsorption of sodium goes up

• Potassium gets wasted

• **Loop and thiazide diuretics cause this

When aldosterone is inhibited, what is the effect on Sodium and Potassium?

• Reabsorption of sodium goes down

• Potassium gets spared

When you workout/sweat, what electrolytes do you lose?

• Potassium

• Sodium

• Calcium

• Magnesium

Where is hypokalemia seen and not seen?

• Hypokalemia is nonexistent in healthy adults

• Seen in 20% hospitalized pts, 40% pts taking thiazide diuretics

Hypokalemia increases mortality in what?

• Pts with chronic heart failure or CKD

What are the functions of potassium?

• Cellular metabolism and growth

• Protein and glycogen synthesis

• Regulation electrical gradient across myocardium

  • Cardiac conduction

What is mild hypokalemia and the sx?

• 3.1-3.49

• May be asymptomatic, N/V, muscle weakness

What is moderate, severe hypokalemia? What are the sx?

• Mod: 2.5-3.0

• Severe: <2.5

• Sx: Paralysis, respiratory compromise, EKG changes, cardiac arrhythmias, death

What are some sx with hypokalemia in general?

• Abnormal heart rhythms

  • U wave, ST depression, shallow t wave

• Muscular dysfunction

  • Muscle cramps, fasiculations, hypoventilation, hypotension, paralytic ileus, rhabdomyolysis

• Impaired renal concentrating ability

  • Polyuria

  • Polydipsia

What medications can cause hypokalemia?

• Diuretics (thiazide and loop), insulin, beta agonists (albuterol)

What is metabolic alkalosis?

• Increased pH and decreased K+

What is refeeding syndrome?

• Severely malnourished patients (nutrition depleted for 7-10 days) receive aggressive nutritional supplementation → cause severe/rapid DECREASES in phosphate, potassium, magnesium

What can cause hypokalemia (treat underlying cause)?

• Medications

  • Diuretics, insulin, B agonists

• Metabolic alkalosis

• Hemodialysis

• Magnesium deficiency

• Refeeding syndrome

In hypokalemia, what is potassium repletion?

• Diet

• Oral supplements

• IV therapy

If a patient needs to be on diuretic therapy, what can you consider in hypokalemia?

• Use potassium sparing diuretic

  • Aldosterone antagonists

    • Spirinolactone

    • Eplerenone

  • Sodium channel blockers

    • Amiloride

    • Triamterene

What do aldosterone antagonists (spironolactone and eplerenone) and inhibition of aldosterone sensitive sodium channels (amiloride and triamterene) do? AKA the potassium sparing diuretics

• Inhibit aldosterone SO reabsorption of Na goes down and potassium gets spared

What pharm treatment can you give to PREVENT and TREAT hypokalemia? What helps with GI tolerance?

• Prevent: 20 mEq/day potassium

• Treat: 40-100 mEq/day potassium

• *Microencapsulated products have better GI tolerance and no bitter smell/aftertaste

How is K+ repletion therapy best administered?

• Orally in divided doses over several days to achieve full repletion

  • Use compliance enhancing regimens; divided doses can help with tolerance; make regimens as simple to follow as possible

K+ repletion therapy is recommended for patients who are what?

• Sodium-sensitive

• Hypertensive

• Subject to vomiting or diarrhea

• Taking diuretics

• Subject to laxative abuse

What is the typical dosing for hypokalemia prevention?

• 1-2 mEq/kg/day orally in 1-2 divided doses

What is the dosing for mild-mod hypokalemia? Severe hypokalemia?

• 2-5 mEq/kg/day in divided doses (oral over IV)

  • Mild to mod

• 10-20 mEq/hour and adjust according to levels

  • Oral monotherapy or adjunct with IV

  • Severe

Use caution in repleting potassium in patients with what? What should you do?

• Caution in repleting potassium in patients with RENAL dysfunction

  • Reduce by 50% in renal insufficiency

What route is preferred in treating hypokalemia?

• ORAL route preferred if pt can tolerate PO and is asymptomatic

  • If patient has severe hypokalemia, might need both PO and IV

  • If patient is in ICU, IV may be preferred

  • If pt is NPO, IV preferred

If a patient has concomitant hypomagnesemia, what do you do?

• Replete magnesium FIRST if it is low because of the ROMK channel

What are the oral potassium formulations to treat hypokalemia? (in order of most to least)

• Potassium chloride: rx, both PO and IV, 52% potassium

• Potassium Bicarbonate: rx/otc, PO

• Potassium citrate: rx/otc, PO

• Potassium gluconate: otc, PO

• Potassium phosphate: rx, both PO and IV

Who is K-Phos products for? What do they contain?

• Used for pts with hypophosphatemia AND hypokalemia

• Different products contain SAME amount of phosphorous and VARIABLE amounts of potassium (and sodium)

How can you minimize GI damage using K-Phos products?

• Dissolve tablets in 6-9 oz H2O for at least 2-5 min (can crush tablet particles that remained undissolved, stir vigorously)

What are common SE for oral K+ products?

• GI side effects (N/V, diarrhea, flatuence)

  • If dose >40 mEq, it should be given in divided dose

What are serious S/E in oral K+ products?

• Abdominal pain, GI ulcer

• Cardiac arrest, arrhythmias

• Hyperkalemia

What are the different formulations of potassium supplements?

• Controlled release micro encapsulated tablet: disintegrates better in GI tract, fewer GI erosions vs wax-matrix tablets

• Wax-matrix extended release tablets: easier to swallow, more GI erosions vs other therapies

What are the 3 potassium IV products? What is known about each product!?

• Potassium chloride

  • Most common, most efficient (raises K+ at FASTER rate)

  • FOR EVERY ~10 mEQ of K+ administered, SERUM K+ WILL INCREASE by 0.1 mEq/L

• Potassium acetate

  • USE if pt has METABOLIC acidosis

• Potassium phosphate

  • Use if pt also has hypophosphatemia

What is a common AE in IV potassium?

• Phlebitis (inflammation of the vein), injection site pain (burning), extravasation (can lead to tissue necrosis)

What are serious AE of IV potassium?

• Cardiac arrest, arrythmias

• Hyperkalemia

What is the central line vs peripheral cannula?

• Central

  • Deep under vein

  • Large vein

  • Good, rapid dilution of the drug

  • Requires higher level skill

• Peripheral cannula

  • Superficial, smaller veins

  • Size of device

  • Movement from limbs/joints

  • Risk of mechanical or chemical phlebitis

What is the max rate IV admin in central and peripheral line for hypokalemia (risk of hyperkalemia)?

• KCl 20 mEq IV/hour

  • Central

• KCl 10 mEq IV/hour

  • Peripheral

What is the max IVPB concentration (risk of infusion site phlebitis)?

• Central: 0.2 mEq/mL

• Peripheral: 0.1 mEq/mL

What should you monitor while IV potassium administration?

• Cardiac function (tele monitoring, ECGs)

• K+ levels

  • Within 2-8 hours after replacement (sooner if symptomatic)

  • Daily with morning labs

• Signs of phlebitis, extravasation

What is the difference between IV piggyback and IV push?

• IVPB= administered as infusion

• IV push= administered via syringe

Why should you never give potassium as IV Push?

• Cause cardiac arrest