Block 4: K+ and Mg2+ Flashcards
What is the most abundant IC electrolyte?
Potassium
What are the functions of K+?
- Regulates osmolarity of ICF (balanced with H+)
- Maintains action potential
- Buffers blood pH
- Facilitates glycogen storage in liver and skeletal muscle cell
How does inulin affect K?
- Insulin shifts K into the cell
- Low K affects insulin production
- Insulin enable the cell to uptake glucose and glycogenesis
What does K/H exchanger do?
Shift H into the cell and K outward
What are the normal values of K?
3.5-5 mEq/L
What is the relationship between serum K and aldosterone?
Indirect, aldosterone increases K excretion and Na intracellularly
What should you check if serum K is low?
Mg2+
What causes hyperkalemia?
- Increased intake
- Decreased excretion
- Renal dysfunction
- Cellular shifts
- Insulin def
- Tissue catabolism
What kind of drugs cause hyperkalemia?
- K sparing
- ACEi/ARBs
- NSAIDs
- B blockers
- Digoxin
- Cyclosporine
- Tacrolimus
- Bactrim
- Heparin
What are the presentations of hyperK?
- EKG changes
- Cardiac arrhythmias
- Heart palpitations or skipped heartbeats
What are the levels of hyperkalemia?
Mild: 5.1-5.9 (asymptomatic)
Moderate: 6-7
Severe: >7 (palpitations)
What are the treatment for hyperkalemia?
- Dietary mod
- Adjustment of contributing med
- Furosemide 40-80 mg IV (↑ excretion)
- Potassium binders
What are the K binders?
SPS (Kayexalate)
Patiromer calcium (Veltassa)
Sodium zirconium cyclosillicate (Lokelma)
What K binders are used for emergency?
SPS and Sodium zirconium cyclosilicate (Lokelma)
What K binders exchange sodium for K+?
SPS and Lokelma
What are the MOA for K binders?
↑ fecal K elimination
What are the similarities of all K binders?
Treat chronic hyperK
What K binders must be separtared from other meds 3 hr before and after admin?
Veltassa and SPS
What are the ADRs of SPS? Indication?
Intestinal necrosis with rectal admin
For acute hyperK
How does patiromer differ from other K binders?
Exchanges Ca for K
Delayed onset of 48 hr
How should you take Lokelma?
Separate other meds by 2 hours pre and post
What are the steps of acute and symptomatic hyperK?
- Check if EKG is abnormal
- Redistribution and intracellular K+ shift
- Eliminate K+ from body
What do you do about the ECG in hyperK?
Abnormal: 1g IV calcium gluconate
If normal don’t give IV calcium
How do you redistribute K?
- Regular insulin 10 u IV + 25 g dextrose unless BG >250
- 50-100mEq IV sodium bicarbonate if pH <7.3
- Albuterol nebulizer 10-20 mg over 10 min if no IV access
- Just use insulin if hyperglycemic
How should you eliminate K from the body?
- SPS 15-30 g PO
- IV loop diuretic if making urine
- Hemodialysis for CKD or life-threatening
When would albuterol be used for hyperkalemia?
- Tachycardia present
- Not effective
What is hypokalemia?
<3,5
What causes hypoK?
- GI/renal losses
- Intracellular shifts (metabolic alkalosis)
- Hypomagnesemia
What drugs cause hypokalemia?
- Loops
- Thiazides
- Beta blockers
- Laxatives
- Insulin
- Sodium bicard
- K binders
What are the presentations and tx of mild hypoK?
3.1-3.5
Asymptomatic
↑ dietary intake
What are the presentations and tx of moderate hypoK?
2.5-3
Cramping, weakness, malaise, myalgia
PO K
What are the presentations and tx of severe hypoK?
<2.5
ECG changes and arrhythmias
When do you start chronic supplementation of hypoK?
- underlying conditions
- Arrhythmia risk
- Concomitant meds
What is the treatment goalsof hypoK?
K<3 mEq/L requires treatment with goal K 4-4.5 mEq/L
What are the IV K salts?
- Chloride (for alkalosis)
2, Acetate (for acidosis) - Phosphate (for low P)
What are PO K salts?
- Chloride (for alkalosis)
- Phosphate (for low P)
- Bicarbonate (for acidosis)
What are the the K-sparing diuretics?
- Spironolacotone
- Triamterene
- Amiloride
Use add on with loops or thiazides
How do you dose IV/PO K?
1.Each 10 mEq od K will ↑ Serum K bu 0.1
2. ((4-K)/sCr)x100
Round to the nearest 10 mEq
How should IV K be given?
Diluted in NS is preferred
Administer via central line if >20mEq/100mL
Cardiac monitoring is admin >10 mEq/hr
What are the infusion rate of IV K?
Peripheral: 10 mEq/hr
Central: 20 mEq/hr
ADRs of IV K?
Burning (reduce rate)
What is the reasons for poor adherence of PO K?
Large tablets and GI intolerance
How do you administer PO K?
Lower and more frequent doses
Microencapsulated tablets
What are the KCl dosage forms?
- CR microencapsulated tabs (Kdur)
- Elixer
- Effervescent tabs
- Wax-matrix ER tabs (Klor-Con)
What KCl has the best GI tolerability?
CR microencapsulated tabs (Kdur)
What Kcl is rapid acting?
Elixer
What KCl is easy to swallow however cause more GI erosion?
Wax-matrix ER tabs (Klor-Con)
What KCl is more expensive?
Effervescent tabs
What are K bicarb and citrate used for?
Acid/base disorders
How do you manage K when taking other drugs?
Daily supplant for thiazides and loops to prevent hypokalemia
K-sparing can be added to counteract depletion
What is the most common K formulation?
Chloride
What is the 2nd most abundant electrolyte in ICF?
Mg
What is most Mg found? How is it eliminated?
bone
Renal
What are the functions of Mg?
- Mg helps K absorption
- Helps Ca absorption, however, Ca inhibits Mg absorption
- Cofactor in reactions dependent on ATP
- Regulate PTH
- Regulates glucose metabolism
What is hypermagnesiem?
> 2.4 mg/dL
What causes hyperMg?
- Renal failure
- Drugs (Mg citrate and supplements)
What are the presentations of hyperMg?
- Muscle weakness
- Shallow respirations
- Arrhythmias
- Symptoms rare when <4.9
What are primary treatments for hyperMg?
- Reduce intake
- Enhance elimination
- Antagonize physiologic effects
What are the treatment options for hyperK?
- IV potassium
- PO potassium
- K sparing diuretics
What do we use to treat hyperMg?
- Calcium gluconate 2g IVP until symptoms abate
- 0.45% NaCl + Loop diuretic
- hemodialysis
What are the characteristic of calcium gluconate with hyperMg?
- May repeat Q1H prn
- Antagonizes effects
- PO calcium has porr F and slow onset
Why is 0.45% NaCl + Loop diuretic used as a combo for hyperMg?
- Enhances elimination
- In patients with normal renal function or CKD 1-3
- Onset 6-12H
When is hemodialysis used for hyperMg?
- Enhances elimination
- Onset 4H
What are the causes of hypomagnesemia?
- Impaired absorption
- Increased excretion
- Alcoholism
- Diuretics, laxatives, PPIs
What are the presentations of hypoMg?
<1.5
1. Muscle weakness, paralysis
2. QT prolongation/arrhythmias
3. Hypokalemia
4. Hypocalcemia
Symptoms until <1 mg/dL
How and when do you dose IV Mg sulfate?
If Mg <1.2 mg/dL OR s/s present
Diluted in IVF
Dosing: 4-6 grams in 2-3 divided doses (Max infusion rate < 150 mg/min )
1g=8mEq
ADRs of IV mag?
Hypocalcemia
How and when do you dose PO Mg sulfate?
If Mg >1.2 mg/dL and asymptomatic
1-2 tabs PO BID-TID
What are the salt forms of PO mg?
Oxide, gluconate, chloride
ADR of PO Mg?
Diarrhea
SR products improve compliance and reduce GI effects
Describe PO Mg replacements?