Hypokalemia

Hypokalemia is a american english word Hypokalaemia in British english.It is also known as also hypopotassemia or hypopotassaemia

Hypokalemia is the condition in which the concentration of potassium (K⁺) in the blood is low.The prefix hypo- means under,kal– refers to kalium, the Neo-Latin for potassium, and -emia means “condition of the blood”.

Normal Plasma Potassium Levels

Normal plasma potassium levels are between 3.5 to 5.0 mEq/L at least 95% of the body’s potassium is found inside cells, with the remainder in the blood. Alternately, the NIH denotes 3.7-5.2 meq/L as a normal range. This concentration gradient is maintained principally by the Na+/K+ pump.

Causes of Hypokalemia

Hypokalemia without body potassium depletion (ECF-ICF shifts) Hypokalemic periodic palsy, alkalosis, insulin and Vit B12 therapy

Potassium depletion and normal acid base equilibrium L- Reduced potassiumintake, osmotic diuresis, leukemias, penicillin and carbenicillin therapy,magnesium deficiency.

Potassium depletion and metabolic acidosis: Diarrhoea, renal tubular acidosis, diabetic ketoacidosis.

Potassium depletion and alkalosis :

Chloride responsive alkalosis: Vomiting, diuretic therapy, adenoma, ureterosigmoidostomy.

Chloride resistant alkalosis : Mineral corticoid excess, Bartter’s syndrome.

Potassium is the major intracellular cation and any reduction in plasma potassium leads to shift intracellular potassium of ECF. Serum K+ of 3 mEq / L corresponds to a total body deficit of 100-200 mEq and for serum K⁺ below 3 mEq. Urinary potassium estimation is valuable in assessing the extent of potassium deficit and its route of loss. When urinary excretion is less than 10-20 mEq/day it indicates that the depletion is severe, long standing and the route of loss is extrarenal. A high urinary excertion (40-80 mEq/day ) indicates that the patient has failed to conserve potassium as a result of renal tubular disease, or hormonal, osmotic or diuretic influences.

Diagnosis of Hypokalemia

Besides serum estimation the clinical manifestation and ECG changes also aid in the diagnosis in suspected cases. Prominent u wave, T wave flattering and sagging S-T segment are characteristic. However ECG changes do not always parallel with the degree of hypokalemia. Hypertension and hypokalemia suggest excess mineral corticoid.

Management of Hypokalemia

Treatment depends upon the aetiology, duration and severity of symptoms. It is important to remember that all administrated potassium must traverse the extracellular compartment before it reaches the depleted cells. Even in presence of large intracellular deficit, small changes in ECF potassium concentration can cause large changes in neuromuscular excitability hence it is usually advised for oral supplement at a rate of 0.5-1 mEq / kg / day. When situation demands immediate therapy as in adynamic ileus infusion rate of 10-20 mEq/L is usually safe provided there is no renal insufficiency. When serum potassium is below 2 mEq / L, infusion rate can be enhanced to 40 mEq/L under close monitoring. Potassium administration is mandatory to all patients with serum potassium below 2.5 mEq / L even if they are asymptomatic.