3. Potassium & Sodium

Majority of K+ is...

Intracellular

Hypokalemia can result in...

- Arrhythmia / death

- Weakness/paralysis

- Myopathy

Hyperkalemia can result in...

- Arrhythmia / death

- Weakness/paralysis

- Renal tubular acidosis

Effect of RAAS on K+ concentrations

Causes excretion of K+

Hypokalemia (value)

Mild hypokalemia (value)

3-3.4 mEq/L

Severe hypokalemia (value)

Causes of hypokalemia

- Decreased intake

- Intracellular shift

- GI/urinary loss (diuretics)

Causes of intracellular shift of K+

- Alkalosis

- Increased insulin

- Hypokalemic periodic paralysis

Hypokalemic periodic paralysis

Autosomal dominant causing hypokalemia triggered by exercise/cold/cards

Hypokalemia with acidosis indicates...

Severe K+ deficiency

Causes of increased urinary loss of K+

- Loop/thiazide diuretics

- Mineralcorticoid excess

- Hypomagensemia

- Licorice

S/S of hypokalemia

- Muscle weakness → rhabdo

- Cardiac arrhythmias

Diagnostic workup of hypokalemia

- EKG

- Muscle strength

- BMP to assess Na, bicarb, creatinine

- Ca and magnesium

Indication for transtubular K+ gradient

Cause of hypokalemia unclear

Transtubular K+ gradient values (TTKG)

ECG changes associated with hypokalemia

- Flat T waves

- U wave

- Depressed ST segment

**Progressively increasing severity of hypokalemia moving down list

Treatment of hypokalemia

PO or IV K+

Treatment of mild hypokalemia (3-3.4) — Acute & chronic

20 mEq PO 1-3x/day

Acute: Evaluate doses per day with labs

Chronic: Stable dose

Treatment of severe hypokalemia OR symptomatic (

40 mEq PO 2-4x/day

General rule with administration of K+ with hypokalemia

Every 10 mEq of KCl raises K+ level by 0.1mEq/L; ASSUMING normal renal function, no ongoing loss or intracellular shift

Indications of IV management of K+ for hypokalemia

- Life-threatening: Paralysis, dig tox

- ECG abnormalities

Order "runs" of KCl

Central line and infusion pump with 10-20 mEq/hr

FYI with IV administration of K+

Phlebitis and extravasation common — Transition to PO ASAP

Hyperkalemia (value)

>5.2 mEq/L

Causes of hyperkalemia

- Increased intake

- Shift OUT of cells

- Decreased urinary excretion

- Pseudohyperkalemia

Causes of K+ shift out of cells

- Metabolic acidosis

- Hyperglycemia/insulin deficiency

- Tissue destruction

- Digi overdose

Demographic associated with hypoaldosteronism & hyperkalemia

Diabetics with mild-mod renal failure

Type 4 RTA

Tubular dysfunction & kidneys DO NOT respond to aldosterone → tubules cannot remove K+ from blood

Medications that can impair aldosterone release

NSAID, ACEI, ARB, heparin

S/S & labs associated with hypoaldosteronism & hyperkalemia

- Hypotension

- Hyperkalemia & mild metabolic acidosis (type 4 RTA), hyponatremia

Diagnostic workup of hypoaldosteronism & hyperkalemia

Assess for other adrenal insufficiency

- Serum cortisol

- Renin

- Aldosterone level

- BMP

Management of hypoaldosteronism & hyperkalemia

Fludrocortisone (with glucocorticoid deficiency → add steroid)

Cause of pseudohyperkalemia

Hemolysis of blood sample — fist clench, small bore needle

Pseudohyperkalemia

Platelets release K+ during coagulation/hemolysis

Common medications causing hyperkalemia

- BB, digoxin

- Bactrim → decreased tubular secretion of K+

FYI with salt substitutes

Generally KCl → can cause hyperkalemia

S/S of hyperkalemia

- Impaired NMJ function → weakness/paralysis

- Decreased cardiac conduction & arrhythmias

Foods high in K+

Bananas, potatoes, tomato sauce, KCl salt substitute

ECG changes associated with hyperkalemia

- Peaked T waves

- QRS prolongation

- P wave flattening

**Progressively increasing severity of hyperkalemia moving down list

FYI of ECG with hyperkalemia

ECG changes NOT always present & changes are unpredictable

Diagnostic workup of hyperkalemia

- ECG & tele

- Ca, Mag, Na

Why is it important to assess Ca, Mg, Na with hyperkalemia patients?

Low levels potentiate cardiac toxicity

If suspicion of pseudohyperkalemia...

Check plasma K+ to ensure actual elevation

Diagnostic workup of hyperkalemia with suspected adrenal insufficiency

Serum aldosterone/cortisol

Hyperkalemia value indicating rapid lowering

>6.5

Indications for rapid lowering of hyperkalemia levels

- EKG changes

- Muscle S/S

- K+ >6.5

- K+ >5 AND either: renal impairment, tissue breakdown

Management of hyperkalemia with rapid lowering

Stabilize cardiac membrane: Ca gluconate 1g IV

Redistribute to intracellular: 10 units of insulin IV with 25 g of dextrose IV

Enhance excretion: Loop diuretic (or

GI cation exchange resins)

What GI cation resin is 1st choice for enhanced excretion of hyperkalemia management?

Sodium zirconium cyclosilicate

What medication is used if patient is acidotic when managing hyperkalemia?

Sodium bicarbonate

Indications for dialysis for enhanced excretion for rapid lowering of K+ levels with hyperkalemia

- ESRD

- Advanced CKD/AKI

- Refractory/severe K+

What is considered mild hyperkalemia?

Up to 5.5 with no concerning S/S

Gradual management of hyperkalemia (mild)

Loop diuretic +/- normal saline

Management of chronic hyperkalemia

- Limit diet K+

- Chronic bicarb if chronic acidosis

- Avoid NSAID, hypovolemia

- SGLT2 can help

Depressed ST segments on ECG is associated with...

Hypokalemia

Peaked T waves on ECG is associated with...

Hyperkalemia

QRS prolongation on ECG is associated with...

Hyperkalemia

Flat T waves on ECG is associated with...

Hypokalemia

U wave on ECG is associated with...

Hypokalemia

P wave flattening on ECG is associated with...

Hyperkalemia

MC electrolyte abnormality with hospitalized patients

Sodim

Hyponatremia value

What does hyponatremia represent?

Excess WATER retention relative to sodium

Normal sodium volume in urine

>20 meq/L with normal volume states and no mediations

**Only measured if systemic hyponatremia

Osmolality depends on...

Presence of ADH

Water/plasma distributions throughout body

Extracellular: 14 L

Intracellular: 28 L

Total: 42 L

Atrial naturetic peptide

Hormone release from atrial monocytes d/t distention of atria to inhibit Na reabsorption by collecting duct

What part of nephron is responsible for majority of H2O reabsorption?

Collecting duct via V2 receptors & aquaporins

Does the body prioritize volume status or osmolality?

Volume status

What primarily determines distribution of body H2O?

Osmotic forces to maintain osmolality within narrow range

How are derangements in plasma osmolality (Posm) reflected?

Abnormalities in serum Na+

Hypernatremia is associated with... (osmolality)

ONLY hyperosmolality

Hyponatremia is associated with... (osmolality)

Low, normal OR high osmolality

**Usually low

Regulation of plasma osmolality (Posm)

Changes sensed by osmoreceptors in hypothalamus to increase thirst & regular H2O intake → ADH release

Dysnatremias

Disruption of normal regulation of Posm

General causes of dysnatremias

- Renal disorders

- Appropriate or inappropriateon non-osmolar stimulus for ADH release (volume depletion, pain, meds)

Hyponatremia is usually due to hypo-osmolality EXCEPT...

- Pseudohyponatremia

- High concentration of solutes other than Na+ — Glucose, mannitol

Pseudohyponatremia

Elevation of plasma lipids OR proteins are isotonic

When is it required to correct Na to determine actual levels?

Hyperglycemia with hyponatremia (when glucose is corrected, H2O moves back into cells)

General rule with glucose & sodium levels

Rise in glucose of 100 above 100 → serum Na+ drops by 1.6 mg/dl

Calculation for corrected serum sodium

G = (pt. glucose - 100)/100

(1.6 mEq/L x G) + (serum sodium)

Initial steps for assessing hyponatremia

Determine osmolality & volume status

Typical S/S of hyponatremia

HA, irritability, confusion, ataxia, delirium, seizure

Acute hyponatremia can cause...

Cerebral edema and intracranial HTN

S/S of chronic hyponatremia

Asymptomatic

Diagnostic workup of hyponatremia

- Assess serum osmolality & volume status

- Urine osmolarity and Na+

**MUST assess serum osmolality and volume status first

What conditions should be r/o for workup of hyponatremia?

Renal failure, adrenal insufficiency, hypothyroidism

General causes of hypovolemia

- Non-renal volume loss

- Renal volume loss

Non-renal volume loss (hypovolemic state)

Increase H2O reabsorption with appropriate ADH secretion & response

Causes of hypovolemia d/t non-renal loss

GI loss

Skin loss

Sequestration

Volume depletion

Causes of hypovolemia d/t renal volume loss

Diuretics

Salt-wasting states

Labs associated with non-renal volume loss vs. renal volume loss (hypovolemic states)

Both: UOsm >400

Non-renal: UNa

General causes of hypervolemia

- Edematous states

- Renal failure

Causes of hypervolemia d/t edematous states

- Cirrhosis

- Nephrotic syndrome

- HF

Renal failure (hypervolemic state)

Inability to dilute urine appropriately

What causes the high UOsm in hypervolemic states?

ADH released d/t renal hypoperfusion & low effective circulating volume

Labs associated with edematous states vs. renal failure

Both: UOsm >350

Edematous: UNa

What volume status & release of ADH is abnormal?

Euvolemia

Common cause of euvolemic hyponatremia

SIADH

Disorders that cause inappropriate secretion/action of ADH

Malignancy: Small cell lung CA

CNS: Head trauma, seizure, stroke

Drug: NSAID, narcotics, thiazides

Other: Uncontrolled pain