Hypokalemia: Clinical Findings

Yu, Yan – Hypokalemia clinical findings – FINAL.pptx
Production of Na+/ K+ transporters in cell membranes ? over timeHypokalemia: Clinical FindingsAuthor: Yan YuReviewers:David WaldnerSean SpenceAndrew Wade** MD at time of publicationLegend:Published May 21, 2013 on www.thecalgaryguide.comMechanismPathophysiologySign/Symptom/Lab FindingComplicationsPalpitationsExcitable cells (muscle cells, neurons) depolarize less readilyK+ efflux out of all cells in the body, down its concentration gradientCardiac myocytes experience electrical conduction defects? muscle impulse conductionECG shows characteristic changes:? skeletal muscle contractile abilityRMP now more negative; myocytes take longer to repolarize to RMP(“stretches out” the T-wave)! Long QT interval (>0.5 of R-R interval)?Flatter T-Waves ?Inverted T-waves (with more severe hypokalemia)Purkinje fibers repolarize after the rest of the myocardium has done soU-waves (upward ECG deviations after the T-wave)Cells become hyperpolarized: Inside of cells are more negative relative to outside, ? Resting Membrane Potential (RMP)In the Kidney:Generalized Muscle weaknessK+ diffuse out of Proximal Convoluted Tubule & Collecting Duct cells ? cells retain acidic H+ inside (maintains electrical neutrality)? pH within PCT cells ? glutaminase activity, ? glutamine breakdown, producing HCO3-, which enters the blood? blood pH, [HCO3-], & pCO2 (respiratory compensation)Low Plasma [K+]Abnormally long diastole means that ventricles are overfilled. Contraction takes greater force; sensed by patientsDyspnea, fatigue, dizziness, syncope? cardiac output ? perfusion of tissues, i.e. lungs & brainCardiac arrhythmias: PACs, PVCs, Sinus Bradycardia, paroxysmal atrial/junctional tachycardia, VT (i.e. Torsades de pointes), V-Fib? smooth muscle contractile abilityBowel ileus (bloating, anorexia, nausea/vomiting, absent bowel sounds)? pH in collecting duct intercalated cells ? H+ secretion into the tubuleMetabolic alkalosisParalysis, muscle cramps (in severe hypokalemia)Respiratory muscle failure (? tidal volume, ? pCO2, ? pO2), may even cause death!? depolarizations ? adenyl cyclase activity ? ? sensitivity of collecting duct cells to ADH? ability of nephron to concentrate urineNephrogenic Diabetes Insipidus? urine osmolality, Hypernatremia, Polyuria, Polydipsia? # of aquaporins in the collecting duct membrane”Insulin Resistance”: ? ability to import K+ from the blood in response to insulinIn skeletal muscle:
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