Hyperkalemia and hypokalemia Notes

NOTES NOTES HYPERKALEMIA & HYPOKALEMIA GENERALLY, WHAT ARE THEY? PATHOLOGY & CAUSES ▪ Imbalances of potassium levels in blood ▪ Etiologies influence potassium intake, excretion, transcellular shift SIGNS & SYMPTOMS ▪ Mild variations usually asymptomatic, severe imbalances may be fatal TREATMENT MEDICATIONS ▪ Discontinue medication that aggravates potassium homeostasis ▪ Low serum K+ ▫ Oral K+ can be supplemented ▪ High serum K+ ▫ Agents/procedures that remove extracellular K+, into cells/↑ secretion from body DIAGNOSIS LAB RESULTS ▪ Blood potassium levels; further tests useful to establish underlying cause HYPERKALEMIA osms.it/hyperkalemia PATHOLOGY & CAUSES ▪ High potassium levels in blood > 5.5 milliequivalents/liter (mEq/L) CAUSES Decreased kidney excretion ▪ Decreased glomerular filtration rate in acute/chronic kidney disease ▪ Adrenal insufficiency → primary hypoaldosteronism ▫ Principal cells secrete less potassium ▪ Drugs 800 OSMOSIS.ORG ▫ Renin inhibitors, angiotensin converting enzyme (ACE) inhibitors, angiotensin II receptor antagonists, potassium-sparing diuretics, nonsteroidal anti-inflammatory drugs (NSAIDs), cyclosporine, trimethoprim-sulfamethoxazole Transcellular shift ▪ Uncontrolled Type I diabetes ▫ Lack of insulin → decreases sodium/ potassium pump action ▪ Acidosis ▫ Excess hydrogen ions move into cells via ion transporters that exchange hydrogen ions for potassium ions ▫ Respiratory acidosis; metabolic acidosis

Chapter 112 Hyperkalemia & Hypokalemia ▪ ▪ ▪ ▪ from organic acids are two exceptions Hyperosmolarity ▫ Gradient pulls water out of cells → intracellular concentration potassium goes up → potassium pushed out Massive cell lysis ▫ E.g. tumor lysis syndrome, rhabdomyolysis, massive hemolysis ▫ Intracellular potassium released into bloodstream (98% of K+ found within cells) Drugs ▫ Beta2-adrenergic antagonists, digoxin toxicity Exercise ▫ Cellular ATP consumed → potassium channels open ▫ Shift usually small, can exacerbate condition in individuals with hyperkalemia Increased intake ▪ Excessive potassium oral intake ▫ Unusual, can exacerbate condition in individuals with hyperkalemia ▪ Rapid, excessive potassium infusion (rare) MNEMONIC: MURDER Signs & symptoms of Hyperkalemia Muscle weakness Urine: oliguria, anuria Respiratory distress Decreased cardiac contractility EKG changes: peaked T waves; QRS widening Reflexes: hyperreflexia or areflexia (flaccid) DIAGNOSIS LAB RESULTS ▪ Potassium levels in blood > 5.5mEq/L OTHER DIAGNOSTICS ECG ▪ Prolonged PR interval, tall, peaked T-waves with narrow base, shortened QT interval, depressed ST segment ▪ Severe ▫ Small/indiscernible P wave, widened QRS complex → strip mimics sine wave SIGNS & SYMPTOMS ▪ Mostly asymptomatic ▪ Severe/rapid-onset hyperkalemia ▫ Muscle weakness, flaccid paralysis (starts in lower extremities, moves upward) → respiratory failure ▫ Decreased deep tendon reflexes ▫ Arrhythmias, cardiac arrest ▫ Nausea, vomiting, intestinal colic, diarrhea Figure 112.1 An ECG demonstrating the changes of hyperkalemia, including elevated T waves, bizarre, broad QRS complexes and a prolonged QT interval. OSMOSIS.ORG 801

TREATMENT MEDICATIONS ▪ Initial treatment (individuals with ECG changes) ▫ Calcium to stabilize myocardial cell membranes MNEMONIC: C BIG K DROP Treatment of Hyperkalemia Calcium gluconate Beta 2 agonist Insulin + Glucose Kayexalate Diuretics/Dialysis ▪ Insulin with dextrose + beta2-adrenergic agonists ▫ Increase potassium shift into cells ▪ Kayexalate ▫ Bind potassium → decrease potassium absorbed from gastrointestinal (GI) tract ▪ Loop diuretics ▫ Increase potassium excretion in kidneys OTHER INTERVENTIONS ▪ Severe hyperkalemia/renal failure ▫ Hemodialysis (most rapid, effective way to lower serum K+) Figure 112.2 The ECG features found in hyperkalemia. 802 OSMOSIS.ORG

Chapter 112 Hyperkalemia & Hypokalemia HYPOKALEMIA osms.it/hypokalemia PATHOLOGY & CAUSES ▪ Low potassium levels in the blood < 3.5mEq/L CAUSES ▪ Increased kidney excretion ▫ Hyperaldosteronism; drugs (e.g. loop, thiazide diuretics, amphotericin B, cisplatin); renal tubular defects (e.g. Bartter syndrome); hypomagnesemia ▪ Increased gastrointestinal excretion ▫ Vomiting (direct loses minimal, causes metabolic alkalosis); diarrhea ▪ Increased sweat production ▫ Relevant for individuals who exercise in hot climate ▪ Shift from extracellular to intracellular space ▫ Insulin overdose in Type I diabetes; excess insulin → increases sodium/ potassium pump action ▪ Alkalosis ▫ Hydrogens move out of cells using ion transporter that exchanges with potassium ions ▫ Respiratory alkalosis an exception ▪ Drugs ▫ Beta2-adrenergic agonists Other causes ▪ Low dietary intake (e.g. prolonged fasting, anorexia, ketogenic diet) ▪ Insulin administration ▪ Antibiotics (TMP-SMX/amphotericin B) ▪ Epinephrine (beta 2-agonists) ▫ Slightly more than half of trauma cases present with hypokalemia (increased epinephrine levels) SIGNS & SYMPTOMS ▪ Mostly asymptomatic ▪ Severe/rapid-onset hypokalemia ▫ Constipation, paralytic ileus ▫ Muscle weakness, cramps, flaccid paralysis ▫ Decreased deep tendon reflexes ▫ Arrhythmias (prolong cardiac conduction), cardiac arrest ▫ Polyuria, polydipsia, nausea, vomiting ▫ Exacerbates digitalis toxicity DIAGNOSIS LAB RESULTS ▪ Blood potassium level < 3.5mEq/L OTHER DIAGNOSTICS ECG ▪ Flattened/inverted T waves, U waves, ST depression, prolonged PR interval ▫ Prominent U waves fused to T waves, mimic prolonged QT ▪ Atrial, ventricular tachyarrhythmias TREATMENT MEDICATIONS ▪ Replenish potassium with supplementation ▫ In acute coronary ischemia, active arrhythmias ▪ Oral KCl administration (safest) ▪ IV administration for individuals taking nil per os ▫ 10mEq KCl increases K+ by 0.1MEq/L ▪ Magnesium replacement ▪ If diuretic therapy needed ▫ Potassium-sparing diuretic OSMOSIS.ORG 803