HypokalemiaHypokalemia

Potassium 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.

INTRODUCTION

potassium 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.

INTRODUCTION

DefinitionDefinition

HypokalemiaHypokalemia is defined as a potassium level is defined as a potassium level less than 3.5 mEq/L.less than 3.5 mEq/L.

Moderate hypokalemiaModerate hypokalemia is a serum level of 2.5-3 is a serum level of 2.5-3 mEq/L. mEq/L.

Severe hypokalemiaSevere hypokalemia is defined as a level less than is defined as a level less than 2.5 mEq/L.2.5 mEq/L.

The reference range for serum potassium level is 3.5-5 The reference range for serum potassium level is 3.5-5 mEq/LmEq/L

PATHOPHYSIOLOGYPATHOPHYSIOLOGYTotal body deficit

of potassium

Acute potassium depletion

potassium shifts from the ECto IC space

Other causes

chronic inadequate intake,long-term diuretic or laxative use, chronic diarrhea, hypomagnesemia & hyperhidrosis

diabetic ketoacidosis, severe GI losses : vomiting / diarrhea, dialysis, and diuretic therapy

Alkalosis & hypothermiainsulin, catecholamines

Distal RTA & Bartter syndrome, Periodic hypokalemic paralysis,Hyperaldosteronism & hyperthyroid.

Abnormalities of serum potassium are associated Abnormalities of serum potassium are associated

with well described clinical featureswith well described clinical features::

S. K+ levelS. K+ level Clinical featuresClinical features

<3.5 mmol/l<3.5 mmol/l LassitudeLassitude

  < 2.5 mmol/l< 2.5 mmol/l Possible muscle necrosis Possible muscle necrosis

<2 mmol/l<2 mmol/l Flaccid paralysisFlaccid paralysis with with respiratory compromise respiratory compromise

Gennari FJ. Hypokalemia. N Engl J Med 1998; 339: 451-458

Effects of hypokalemiaEffects of hypokalemia

Atrial/ventricular ArrhythmiasAtrial/ventricular Arrhythmias are more are more common in patients with underlying common in patients with underlying heart disease (especially CAD) and in heart disease (especially CAD) and in patients taking digoxin. patients taking digoxin.

life-threatening Cardiac Arrhythmiaslife-threatening Cardiac Arrhythmias can can occur when the serum potassium is very occur when the serum potassium is very low (< 2 meq/L), or when the serum low (< 2 meq/L), or when the serum potassium is relatively low (2 - 3 meq/L) potassium is relatively low (2 - 3 meq/L) in patients with underlying heart disease, in patients with underlying heart disease, or when the patient is digoxin-toxic. or when the patient is digoxin-toxic.

severe (or rapidly occurring) hypokalemia severe (or rapidly occurring) hypokalemia can cause can cause muscle weakness and muscle weakness and paralysisparalysis the paralysis mainly affects the the paralysis mainly affects the proximal lower extremities => proximal lower extremities => progressing to affect the upper progressing to affect the upper extremities; dysphagia and dysarthria are extremities; dysphagia and dysarthria are uncommon and cranial nerve palsies are uncommon and cranial nerve palsies are exceedingly rare) exceedingly rare)

RhabdomyolysisRhabdomyolysis can occur in severely can occur in severely potassium-depleted patients - especially potassium-depleted patients - especially following vigorous exercise - and following vigorous exercise - and muscle muscle necrosisnecrosis can rarely occur can rarely occur

Effects of hypokalemiaEffects of hypokalemia

hypokalemia produces a hypokalemia produces a carbohydrate-carbohydrate-intoleranceintolerance (? due to impaired insulin release (? due to impaired insulin release and ? impaired insulin resistance) => and ? impaired insulin resistance) => worsening hyperglycemia in diabetics.worsening hyperglycemia in diabetics.

hypokalemia also produces hypokalemia also produces a metabolic a metabolic alkalosisalkalosis (by ? stimulation of bicarb absorption (by ? stimulation of bicarb absorption by the proximal tubule and ? renal by the proximal tubule and ? renal ammoniagenesis) ammoniagenesis)

hypokalemia can contribute to the hypokalemia can contribute to the development, or worsen the symptoms, of development, or worsen the symptoms, of hepatic encephalopthyhepatic encephalopthy (? due to renal (? due to renal ammoniagenesis) ammoniagenesis)

Effects of hypokalemiaEffects of hypokalemia

Although Although ECGECG changes may be helpful if changes may be helpful if present, their absence should not be taken as present, their absence should not be taken as reassurance of normal cardiac conduction. reassurance of normal cardiac conduction. The ECG in hypokalemia may appear normal The ECG in hypokalemia may appear normal or may have only subtle findings immediately or may have only subtle findings immediately prior to clinically significant dysrhythmias. prior to clinically significant dysrhythmias.

During therapy, monitor for changes During therapy, monitor for changes associated with over-correction and associated with over-correction and hyperkalemia including prolonged QRS, hyperkalemia including prolonged QRS, peaked T waves, bradyarrhythmia, sinus peaked T waves, bradyarrhythmia, sinus node dysfunction, and asystole.node dysfunction, and asystole.

InvestigationsInvestigations

The ECG findings in hypokalemia:

Ventricular dysrhythmia, Prolongation of QT interval, ST segment depression, T wave flattening& U waves.

Drug screen (serum or Drug screen (serum or urine):urine):– AmphetaminesAmphetamines and and

other sympathomimetic other sympathomimetic stimulants can cause stimulants can cause hypokalemia. hypokalemia.

– Other drugs includeOther drugs include» verapamil overdose.verapamil overdose.» Theophylline.Theophylline.» amphotericin B.amphotericin B.» Aminoglycosides.Aminoglycosides.» cisplatin.cisplatin.

InvestigationsInvestigations

Hormonal assay:Hormonal assay:

• Serum ACTH,Serum ACTH,

• Cortisol,Cortisol,

• Renin activity,Renin activity,

• AldosteroneAldosterone

left adrenal adenoma

Conn syndrome

2. Replenishing potassium stores2. 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 ~ 200 - 400 meq of potassium for every 1 meq/L the serum potassium is below 4 meq/L

consider the possibility of associated magnesium deficiency

Replenishing potassium storesReplenishing potassium stores

cardiac monitoringcardiac monitoring is necessary in patients with is necessary in patients with profound hypokalemia (< 2.5 meq/L), or profound hypokalemia (< 2.5 meq/L), or if cardiac arrhythmias are present, or if cardiac arrhythmias are present, or if IV potassium is going to be rapidly administered.if IV potassium is going to be rapidly administered.

IV potassiumIV potassium should normally be diluted in should normally be diluted in saline solution so that the maximum saline solution so that the maximum concentration is 40 meq/L (peripheral lines) or 60 concentration is 40 meq/L (peripheral lines) or 60 meq/L (central lines) and IV potassium. meq/L (central lines) and IV potassium.

IV infusion rate for IV infusion rate for severe or symptomaticsevere or symptomatic hypokalemia hypokalemia

..

Standard IV replacement rateStandard IV replacement rate 10 - 20 meq/h10 - 20 meq/h

Serum potassium < 2.5 meq/L, orSerum potassium < 2.5 meq/L, or Moderate-severe symptomsModerate-severe symptoms

20 - 40 meq/h20 - 40 meq/h

Serum potassium < 2.0 Meq/L, orSerum potassium < 2.0 Meq/L, or Life-threatening symptomsLife-threatening symptoms

> 40 meq/h> 40 meq/h

If heart block, or If heart block, or Renal insufficiency existsRenal insufficiency exists

5 - 10 meq/h5 - 10 meq/h

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), or

If the hypokalemia is causing muscle paralysis, or

Malignant cardiac arrhythmias .

Medical Decision-Making and TreatmentMedical Decision-Making and Treatment

Medical Decision-Making and TreatmentMedical Decision-Making and Treatment

Outpatient therapyOutpatient therapy and follow-up in 48 - 72 and follow-up in 48 - 72 hours may be acceptable for mild hours may be acceptable for mild hypokalemia patients with no underlying hypokalemia patients with no underlying heart disease. heart disease.

The patient should be The patient should be transferred to ICUtransferred to ICU for for severe or symptomaticsevere or symptomatic hypokalemia hypokalemia for:for:

IV potassium supplementation.IV potassium supplementation.Continuous cardiac monitoring.Continuous cardiac monitoring.

Medical Decision-Making and TreatmentMedical Decision-Making and Treatment

Magnesium Replacement TherapyMagnesium Replacement Therapy

Magnesium replacement therapy is often necessary in Magnesium replacement therapy is often necessary in malnourished malnourished alcoholicsalcoholics with hypokalemia. with hypokalemia.

Hypomagnesemia should be suspected if the serum Hypomagnesemia should be suspected if the serum potassium does not increase within potassium does not increase within ~ 96~ 96 hours of the hours of the

commencement of potassium suppcommencement of potassium supplelementation therapy.mentation therapy.

Magnesium can be given orally (Magnesium can be given orally (3g x 4 doses3g x 4 doses).).

The cause of hypokalemia

Certain simple combinations of Certain simple combinations of clinical features and abnormal clinical features and abnormal laboratory values could suggest laboratory values could suggest a particular diagnosisa particular diagnosis

1. Renin secreting tumor or

2. Bilateral renal artery stenosis or

3. Malignant hypertension

Q.1. Hypertension + High Serum Renin + High Serum Aldosterone.

Q.2. Hypertension + Low Serum Renin + High Serum Aldosterone.

Primary Hyperaldosteronism

Q.3. Hypertension + Low Serum

Renin  + Low Serum Aldosterone.

1. Liddle syndrome or

2. congenital adrenal hyperplasia or

3. chronic ingestion of licorice-compounds containing glycyrrhizin or

4. ingestion of other exogenous mineralocorticoids

Q.4.Hypertension + Normal/high Serum Renin + Normal Serum Aldosterone

Cushing’s Syndrome

Q.5. Hypotension/normotension + High Serum Renin + High

Serum Aldosterone.

“Secondary Hyperaldosteronism”

Q.6. Normotension + metabolic acidosis + hyperchloremia + urine ph > 6.

Distal RTA

Bartter's syndrome Bartter's syndrome

Q.7.Q.7.Normotension/hypotension Normotension/hypotension Increased serum renin Increased serum renin Metabolic aklalosis Metabolic aklalosis Hypomagnesemia Hypomagnesemia Hypercalciuria Hypercalciuria Increased urinary chloride (> 100 meq/l)Increased urinary chloride (> 100 meq/l)

Q.8. Normotension/hypotension + metabolic alkalosis + low urinary chloride

1. Surreptitious vomiting or

2. Prolonged naso-gastric suction and

excessive gastric fluid loss

Surgical CareSurgical Care

Surgical intervention is required only Surgical intervention is required only after determining that the etiology after determining that the etiology requires it. requires it.

Etiologies that may require surgery Etiologies that may require surgery include the following: include the following:

1.1. Renal artery stenosis.Renal artery stenosis.2.2. Adrenal adenoma.Adrenal adenoma.3.3. Intestinal obstruction producing massive Intestinal obstruction producing massive

vomiting.vomiting.4.4. Villous adenoma.Villous adenoma.

ConsultationsConsultations

The following consultations may be appropriate, The following consultations may be appropriate, depending on the clinical findings:depending on the clinical findings:

NephrologistNephrologist for evaluation of unexplained urinary for evaluation of unexplained urinary potassium losses suggested to be secondary to a potassium losses suggested to be secondary to a tubular disorder.tubular disorder.

EndocrinologistEndocrinologist if Cushing syndrome, primary if Cushing syndrome, primary hyperaldosteronism, glucocorticoid-remediable hyperaldosteronism, glucocorticoid-remediable hypertension, or congenital adrenal hyperplasia is hypertension, or congenital adrenal hyperplasia is suggested.suggested.

PsychiatristPsychiatrist for alcoholism or eating disorders for alcoholism or eating disorders Surgeon.Surgeon.

Diet: Diet: ‟‟low-sodium and high-low-sodium and high-potassiumpotassium””

The low-sodium diet limits the The low-sodium diet limits the amount of sodium reabsorbed at the amount of sodium reabsorbed at the cortical collecting tubule, thus cortical collecting tubule, thus limiting the amount of potassium limiting the amount of potassium secreted. secreted.

Further Inpatient Care Further Inpatient Care

Matching potassium intake to losses. Matching potassium intake to losses. Monitoring for Hypokalemia or Monitoring for Hypokalemia or

Hyperkalemia Due to Therapy By:Hyperkalemia Due to Therapy By:» periodic testing of serum potassium levelsperiodic testing of serum potassium levels» EKG. EKG.

Alleviation of aggravating conditions. Alleviation of aggravating conditions.

Further Outpatient Care Further Outpatient Care

Patients should receive follow-up Patients should receive follow-up medical care for home management if medical care for home management if the condition is expected to persist the condition is expected to persist beyond inpatient care. beyond inpatient care.

Additional medical follow-up must be Additional medical follow-up must be obtained for associated medical obtained for associated medical conditions.conditions.

Patient Education Patient Education Patients should be educated in terms of predisposing Patients should be educated in terms of predisposing

conditions. conditions. The importance and risks involved with potassium The importance and risks involved with potassium

supplementation andsupplementation and The warning signs of hypokalemia or over-treatment must The warning signs of hypokalemia or over-treatment must

be emphasized in discharge teaching.be emphasized in discharge teaching. Knowledge of cardiopulmonary resuscitation and education Knowledge of cardiopulmonary resuscitation and education

on timely access to emergency medical services may on timely access to emergency medical services may prevent morbidity or mortality. prevent morbidity or mortality.

Ongoing communication is essential in reducing the risks Ongoing communication is essential in reducing the risks and therapy, especially in patients with chronic conditions and therapy, especially in patients with chronic conditions associated with hypokalemia.associated with hypokalemia.

Medical/Legal PitfallsMedical/Legal Pitfalls

Failure to adequately communicate the risks of Failure to adequately communicate the risks of treatmenttreatment

Failure to appropriately monitor patients Failure to appropriately monitor patients receiving potassium supplementation for receiving potassium supplementation for complications, complications,

Failure to follow serum potassium and other Failure to follow serum potassium and other electrolyte concentrations during or after therapyelectrolyte concentrations during or after therapy

Treating a patient based on a falsely low serum Treating a patient based on a falsely low serum potassium value due to sampling or lab errorpotassium value due to sampling or lab error