DR. Akash THESIS ETIOLOGY, INCIDENCE AND OUTCOME OF POTASSIUM ABNORMALITIES IN ICU PATIENTS INTRODUCTION: Claude Bernard wrote that ‘the constancy of the internal milieu is the essential condition to a free and independent life’. Potassium is the most abundant cation in the human body, with total body stores amounting to 50 mmol/kg in adults. Less than 2% of K+ is located extracellularly, and kalemia is maintained in the narrow range of 3.5–5.0 mmol/L. Potassium (K+) is an important electrolyte that has been proven essential for normal functioning of the cardiovascular system, skeletal muscle, internal organs, and nervous system. The intracellular proportion of K+, which represents more than 98% of the total body K+, controls cell metabolism and the resting membrane potential. Intracellular K+ is essential for excitability and automaticity of myocardial cells and for the normal functioning of other cells. The normal serum K+ level is 3.5 to 4.5 mEq/L. ¹ ² An abnormal K+ level pr