Finally there is a blending of the QRS and T waves (a sinusoidal pattern), hypotension, and either ventricular asystole or fibrillation. Hyperkalemia may also be associated with peripheral muscle weakness, decreased contractility, and weak pulse quality. Hyperkalemia also increases potassium permeability which augments the repolarization phases of the electrocardiograph (tall, tented, narrow T-wave) and diminishes the depolarization phases (small P waves prolonged P-R intervals bradycardia, and widened QRS complexes). Hyperkalemia causes membrane hypopolarization which may result in extrasystoles/fibrillation if the resting membrane potential is slightly more negative than threshold potential or asystole when resting membrane potential is slightly less negative. In-vitro platelet/white cell degeneration (only very severe thrombocytosis or leucocytosis) Rewarming and washout of ischemic tissues Familial periodic hyperkalemic paralysis Metabolic (inorganic)/respiratory acidosis It may also be falsely elevated if the blood sample is not analyzed for a period of time due to hemolysis (only in the Akita dog) or from platelet or white cell degradation (only in severe thrombocytosis or leucocytosis). It may also be caused by rhabdomyolysis, metabolic (inorganic)/respiratory acidosis, periodic familial hyperkalemia. Hyperkalemia is primarily caused by oliguric/anuric renal disease, hypo-adrenocorticism, and iatrogenic causes. Resting membrane potential is determined by the equilibrium between potassium moving out of the cell in response to the intracellular-to-extracellular potassium gradient, and potassium moving back into to the cell in response to the extracellular-to-intracellular electronegativity.
Repolarization of electrically excitable cells is largely attributed to the rapid efflux of potassium. Most of the potassium in the body is located in the intracellular fluid compartment (140 mEq/L 55 mEq/kg) while very little of it is located in the extracellular fluid compartment (4 mEq/L 1 mEq/kg). Potassium concentration is very commonly abnormal in critically ill patients.
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