Electrolyte Disorders

What electrolytes are not included on a BMP?

Magnesium and Phosphorus

How much of water makes up total body weight?

60% with 2/3 being intracellular where as 1/3 is extracellular

What is osmolarity?

total solute concentration in a fluid compartment

what solutes determine the calculated osmolality of the ECF?

Sodium, Glucose, and Urea

What substances contribute to an elevated osmolal gap?

Mannitol and Ethanol

What is tonicity?

the ability of solutes to generate an osmotic driving force that causes water movement from one compartment to another

How is tonicity increased?

a solute must be confined to the ECF compartment i.e increased Na+ will increase tonicity causing cells to shrink

What determines the size of extracellular fluid volume (ECFV)?

total amount of Na+ in the ECF and volume status of the patient

What does an abnormal serum Na+ indicate?

sign of a disorder of water regulation

What are the causes of hypovolemia?

GI losses, Renal losses, Skin losses, Fluid sequestration, Hemorrhage

What are the signs of hypovolemia?

Increased thirst, decreased turgor, dry mucous membranes, oliguria, tachycardia, postural hypotension

What are the causes of hypervolemia?

Liver disease, Heart Failure, and Kidney Failure

What are the signs of hypervolemia?

SOB, Orthopnea, PND, Crackles, JVD, peripheral edema

What influences water retention?

Thirst and ADH (vasopressin or arginine vasopressin)

What influences salt retention?

Renin-Angiotensin system

What are the functions of aldosterone?

1. Increase renal Na+ retention (in effect, ↑ECFV)

2. Increase renal K+ excretion

What is the most common electrolyte abnormality in hospitalized patients?

Hyponatremia

What are the severity levels for hyponatremia?

Mild: 125-135

Mod: 120-125

Severe: <120

Lethal: <120 with seizures

What are the symptoms of hyponatremia?

HA, dizziness, N/V, lethargy, weakness, confusion, seizures, delirium, coma (cerebral edema!)

What are the causes of hyponatremia?

Pseudohyponatremia and Redistributive hyponatremia

What is Pseudohyponatremia?

Serum Na < 135 but NORMAL osmolality (iso-osmolar) seen in hyperlipidemia and hyperproteinemia

What causes Redistributive hyponatremia?

osmotically active solutes in the ECF, that draw H2O from cell, diluting serum sodium concentration seen in hyperglycemia

What are the causes of Hypovolemic Hyponatremia?

Renal Loss (Na+ >20): Diuretics, renal tubular acidosis, diuresis, Addison's

Extra-renal Loss (Na+ <20): GI loss, cuteanous loss, pancreatitis, obstruction, peritonitis

What is the treatment for Hypovolemic Hyponatremia?

replace fluid losses (with isotonic fluid, ie. NS), and treat the underlying cause

What causes hypervolemic hyponatremia?

Hepatic cirrhosis, CHF, renal failure

What is the treatment for hypervolemic hyponatremia?

diuretics, dialysis, fluid restriction

What causes Euvolemic Hyponatremia?

SIADH, polydipsia, hypothyroidism, adrenal insufficiency, glucocorticoid excess

What are the hallmark findings for SIADH?

Low serum osmolarity with concentrated urine and euvolemia (urine Na+ >40, osmolarity >100)

What is the treatment for Euvolemic Hyponatremia?

fluid restriction (1.5 L/day), treat underlying cause.

What is the rate that hyponatermia should be corrected?

Acute: ≤10 mEq/L in the first 24 hours and ≤18 mEq/L in 48 hours

Chronic: ≤8 mEq/L in the first 24 hours

What can a rapid increase in serum sodium cause?

cerebral pontine myelinolysis (CPM) or osmotic demyelination syndrome (ODS)

What is hypernatremia?

A hypertonic disorder due to serum sodium >145mEq/L leading to brain cell shrinkage secondary to increased ECF osmolarity

What causes hypernatremia?

GI losses, skin loss, diuretics, lithium

What are the symptoms of hypernatremia?

thirst, AMS, neuromuscular irritability, focal neuro deficits, seizures, arginine vasopressin disorder

What is arginine vasopressin disorder (diabetes insipidus)?

either caused by AVP deficiency or resistance

What is the characteristic finding of arginine vasopressin disorder?

Urine is dilute with low osmolarity and sodium (<250) with polyuria (50-60 ml/kg/day)

How to differentiate between AVP-D and AVP-R?

AVP-D: low or undetectable plasma copeptin and increase in osmolarity after desmopressin

AVP-R: minimal or no response to desmopressin administration

What is the treatment for AVP-R?

Ensure adequate free water intake to match urinary losses and add Thiazide diuretic if needed

What is the treatment for generalized hypernatermia?

stop water loss and replace water deficit (orally, NG, IV)

What occurs if water is replaced too rapidly?

seizures, brain damage, and CPM

How is water deficit calculated?

Normal TBW - Current TBW

What is hypokalemia?

< 3.5 mEq/L

What causes hypokalemia?

diuretics (MC), insulin, caffeine, GI losses, burns, magnesium deficiency

What is the clinical presentation of hypokalemia?

weakness, fatigue, cramps, arrhythmia, hyporeflexia, flaccid paralysis, hypercapnia

What ECG findings are consistent with hypokalemia?

Flattened T waves, prominent U waves, PVCs, depressed ST segments

What is the treatment for hypokalemia?

Potassium replacement orally or IV if needed (Must be given slowly) +/- Magnesium replacement and Digoxin

What is the replacement rate for hypokalemia?

For every 0.1 mEq/L below 4mEq/L, Give 10 mEq/L

What is hyperkalemia?

K > 5 mEq/L and severe > 6.5 mEq/L

What are the symptoms of hyperkalemia?

asymptomatic, muscle weakness

What ECG findings are seen with hyperkalemia?

Peaked T waves, widened QRS, junctional rhythm, V-fib

What are causes of hyperkalemia?

Hemolysis, Renal Failure (#1), Metabolic Acidosis, Spironolactone, ACE/ARB, NSAIDs, increased dietary/medication intake

What is the emergent management of Hyperkalemia?

1) IV Calcium

2) Sodium bicarbonate, Insulin IV + D50W, Nebulized albuterol

3) IV Lasix, PO potassium binders, emergent dialysis

What is the less emergent management of Hyperkalemia?

Potassium binders (Lokelma), Diuretics, and correct underlying cause

How is total calcium measured?

free (ionized) + protein-bound

What is ionized calcium?

Physiological active form, unaffected by serum albumin level

What is complexed calcium?

calcium bound to small anions (citrate, lactate, etc.) to prevent clotting

What is protein-bound calcium?

bound to albumin

What is hypercalcemia?

Calcium >10.1

What is the symptoms of hypercalcemia?

Stones, Bones, Abdominal Moans, and Psychiatric Groans

What are the causes of hypercalcemia?

Malignancy (>13), primary hyperparathyroidism, thiazides, lithium, antacids, vitamin A anaogs (accutane)

What is the equation for corrected calicum?

measured total calcium + [0.8x (4-albumin)]

What is the treatment for hypercalcemia?

IV fluids, calcitonin, bisphosphonates, dialysis

What causes hypocalcemia?

hypoparathyroidism, vitamin D deficiency, renal disease, bisphosphonates, cinacalcet

What are the symptoms of hypocalcemia?

hyperreflexia, spontaneous twitching, muscle cramps, tingling, numbness

Chvostek's and Trousseau's Sign

How is hypocalcemia managed?

IV calcium gluconate

What causes hypophosphatemia?

inadequate intake (supply or absorption), urinary losses, vitamin D deficiency, malabsorption, refeeding syndrome

What is the clinical presentation of hypophosphatemia?

metabolic encephalopathy and hypoventilation

What causes hyperphosphatemia?

CKD or phosphate-containing laxatives

What is the treatment for hyperphosphatemia?

oral phosphate binders and calicum carbonate

What is hypermagnesemia?

> 2.2

What are some signs of hypermagnesemia?

weakness, hypotension, N/V

What ECG changes are seen with hypermagnesemia?

widened QRS, prolonged PR interval, prolonged QT interval

What is the treatment of hypermagnesemia?

IV calcium gluconate, IV fluids, IV lasix, dialysis

What is hypomagnesemia?

Mg < 1.8

What causes hypomagnesemia?

chronic alcoholism, chronic diarrhea, diuretics, nutritional deficiency, long term PPI use

What are the symptoms of hypomagnesemia?

lethargy, anorexia, N/V, weakness, tetany, seizures, arrhythmias

What is the treatment for hypomagnesemia?

IV or IM magnesium sulfate