2INTRODUCTIONPotassium is one of the body's major ions.Nearly 98% of the body’s potassium is intracellular.The ratio of intracellular to extracellular potassium is important in determining the cellular membrane potential.Small changes in the extracellular potassium level can have profound effects on the function of the cardiovascular and neuromuscular systems.The kidney determines potassium homeostasis, and excess potassium is excreted in the urine.
3INTRODUCTIONpotassium is necessary for the maintenance of normal charge difference between intracellular and extracellular environments.potassium homeostasis is tightly regulated by specific ion-exchange pumps (primarily by a cellular, membrane-bound, sodium-potassium ATP-ase).Derangements of potassium regulation often lead to neuromuscular, gastrointestinal, and cardiac conduction abnormalities.
5DefinitionHypokalemia is defined as a potassium level less than 3.5 mEq/L.Moderate hypokalemia is a serum level of mEq/L.Severe hypokalemia is defined as a level less than 2.5 mEq/L.The reference range for serum potassium level is mEq/L
6PATHOPHYSIOLOGY Total body deficit of potassium diabetic ketoacidosis, chronic inadequate intake,long-term diuretic or laxative use,chronic diarrhea, hypomagnesemia & hyperhidrosisTotal body deficitof potassiumdiabetic ketoacidosis,severe GI losses : vomiting / diarrhea,dialysis, and diuretic therapyAcute potassiumdepletionpotassium shiftsfrom the ECto IC spaceAlkalosis & hypothermiainsulin,catecholaminesDistal RTA & Bartter syndrome,Periodic hypokalemic paralysis,Hyperaldosteronism & hyperthyroid.Other causes
7Abnormalities of serum potassium are associated with well described clinical features: S. K+ levelClinical features<3.5 mmol/lLassitude < 2.5 mmol/lPossible muscle necrosis<2 mmol/lFlaccid paralysis with respiratory compromiseGennari FJ. Hypokalemia. N Engl J Med 1998; 339:
8Effects of hypokalemia Atrial/ventricular Arrhythmias are more common in patients with underlying heart disease (especially CAD) and in patients taking digoxin.life-threatening Cardiac Arrhythmias can occur when the serum potassium is very low (< 2 meq/L), or when the serum potassium is relatively low (2 - 3 meq/L) in patients with underlying heart disease, or when the patient is digoxin-toxic.
9Effects of hypokalemia severe (or rapidly occurring) hypokalemia can cause muscle weakness and paralysis the paralysis mainly affects the proximal lower extremities => progressing to affect the upper extremities; dysphagia and dysarthria are uncommon and cranial nerve palsies are exceedingly rare)Rhabdomyolysis can occur in severely potassium-depleted patients - especially following vigorous exercise - and muscle necrosis can rarely occur
10Effects of hypokalemia hypokalemia produces a carbohydrate-intolerance (? due to impaired insulin release and ? impaired insulin resistance) => worsening hyperglycemia in diabetics.hypokalemia also produces a metabolic alkalosis (by ? stimulation of bicarb absorption by the proximal tubule and ? renal ammoniagenesis)hypokalemia can contribute to the development, or worsen the symptoms, of hepatic encephalopthy (? due to renal ammoniagenesis)
11InvestigationsAlthough ECG changes may be helpful if present, their absence should not be taken as reassurance of normal cardiac conduction. The ECG in hypokalemia may appear normal or may have only subtle findings immediately prior to clinically significant dysrhythmias.During therapy, monitor for changes associated with over-correction and hyperkalemia including prolonged QRS, peaked T waves, bradyarrhythmia, sinus node dysfunction, and asystole.
12The ECG findings in hypokalemia: Ventricular dysrhythmia, Prolongation of QT interval, ST segment depression, T wave flattening& U waves.
13Investigations Drug screen (serum or urine): Hormonal assay: Amphetamines and other sympathomimetic stimulants can cause hypokalemia.Other drugs includeverapamil overdose.Theophylline.amphotericin B.Aminoglycosides.cisplatin.Hormonal assay:Serum ACTH,Cortisol,Renin activity,Aldosterone
172. Replenishing potassium stores There is no direct correlation between the serum potassium and the total body potassium deficit, but a rough estimate is to assume a total body deficit of ~ meq of potassium for every 1 meq/L the serum potassium is below 4 meq/Lconsider the possibility of associated magnesium deficiency
18Replenishing potassium stores cardiac monitoring is necessary in patients withprofound hypokalemia (< 2.5 meq/L), orif cardiac arrhythmias are present, orif IV potassium is going to be rapidly administered.IV potassium should normally be diluted in saline solution so that the maximum concentration is 40 meq/L (peripheral lines) or 60 meq/L (central lines) and IV potassium.
19IV infusion rate for severe or symptomatic hypokalemia Standard IV replacement ratemeq/hSerum potassium < 2.5 meq/L, orModerate-severe symptomsmeq/hSerum potassium < 2.0 Meq/L, orLife-threatening symptoms> 40 meq/hIf heart block, orRenal insufficiency existsmeq/h.
20Medical Decision-Making and Treatment Transient, asymptomatic, or mild hypokalemia may resolve spontaneously or may be treated with enteral potassium supplements.Potassium replacement therapy is immediately indicated for:Severe hypokalemia (< 2.5 meq/L), orIf the hypokalemia is causing muscle paralysis, orMalignant cardiac arrhythmias .
21Medical Decision-Making and Treatment Outpatient therapy and follow-up in hours may be acceptable for mild hypokalemia patients with no underlying heart disease.
22Medical Decision-Making and Treatment The patient should be transferred to ICU for severe or symptomatic hypokalemia for:IV potassium supplementation.Continuous cardiac monitoring.
23Magnesium Replacement Therapy Magnesium replacement therapy is often necessary in malnourished alcoholics with hypokalemia.Hypomagnesemia should be suspected if the serum potassium does not increase within ~ 96 hours of the commencement of potassium supplementation therapy.Magnesium can be given orally (3g x 4 doses).
24The cause of hypokalemia what is the next step?The cause of hypokalemia
25Certain simple combinations of clinical features and abnormal laboratory values could suggest a particular diagnosis
26Q.1. Hypertension + High Serum Renin + High Serum Aldosterone. Renin secreting tumor orBilateral renal artery stenosis orMalignant hypertension
33Q.8. Normotension/hypotension + metabolic alkalosis + low urinary chloride Surreptitious vomiting orProlonged naso-gastric suction and excessive gastric fluid loss
34Surgical CareSurgical intervention is required only after determining that the etiology requires it.Etiologies that may require surgery include the following:Renal artery stenosis.Adrenal adenoma.Intestinal obstruction producing massive vomiting.Villous adenoma.
35ConsultationsThe following consultations may be appropriate, depending on the clinical findings:Nephrologist for evaluation of unexplained urinary potassium losses suggested to be secondary to a tubular disorder.Endocrinologist if Cushing syndrome, primary hyperaldosteronism, glucocorticoid-remediable hypertension, or congenital adrenal hyperplasia is suggested.Psychiatrist for alcoholism or eating disordersSurgeon.
36Diet: ‟low-sodium and high-potassium” The low-sodium diet limits the amount of sodium reabsorbed at the cortical collecting tubule, thus limiting the amount of potassium secreted.
37Further Inpatient Care Matching potassium intake to losses.Monitoring for Hypokalemia or Hyperkalemia Due to Therapy By:periodic testing of serum potassium levelsEKG.Alleviation of aggravating conditions.
38Further Outpatient Care Patients should receive follow-up medical care for home management if the condition is expected to persist beyond inpatient care.Additional medical follow-up must be obtained for associated medical conditions.
39Patient EducationPatients should be educated in terms of predisposing conditions.The importance and risks involved with potassium supplementation andThe warning signs of hypokalemia or over-treatment must be emphasized in discharge teaching.Knowledge of cardiopulmonary resuscitation and education on timely access to emergency medical services may prevent morbidity or mortality.Ongoing communication is essential in reducing the risks and therapy, especially in patients with chronic conditions associated with hypokalemia.
40Medical/Legal Pitfalls Failure to adequately communicate the risks of treatmentFailure to appropriately monitor patients receiving potassium supplementation for complications,Failure to follow serum potassium and other electrolyte concentrations during or after therapyTreating a patient based on a falsely low serum potassium value due to sampling or lab error