update of potassium homeostasis in critically ill patients and their management

The chronic increased work of breathing in COPD results in anaerobic metabolism of the ventilatory muscles and overproduction of lactic acid; the eventually coexisting profound tissue hypoxia; and the decreased lactate clearance by the liver because of hypoperfusion. Metabolic acidosis results in hyperkalaemia.Respiratory alkalosis plays a minor role in the hypokalemic state found in severe asthma. The major causes are diuretics and β2- agonists which are taken by patients with cardiovascular diseases which accompany severe asthma.Excessive use of diuretics and β2-agonists decreases serum levels of potassium, magnesium, and phosphate.Preoperative hypokalaemia predisposes to potentially life-threatening arrhythmias during general anesthesia. Arrhythmias are related to severity of heart disease, chronic digoxin therapy, diuretic therapy and preoperative potassium levels, especially when potassium levels < 3.0mEq/L. All these data recommend postponing of the operations to correct plasma potassium levels.Following open heart surgery, a decreased potassium concentration is usually found and this may be caused by receiving preoperative therapy with digitalis and diruretics. In addition to the diluted perfusate, however, other factors such as respiratory alkalosis, and steady postoperative urinary excretion are contributing factors to hypokalemia. Cardiac arrhythmias are prone to occur which may terminate in irreversible myocardial dysfunction.Microvascular endothelial dysfunction and altered vascular reactivity often occur after ischemic arrest and cardiopulmonary bypass, although cardioplegia has been routinely used for the protection of the myocardium against ischemic injury during cardiac surgery. Recent studies found that KCa channel activation has agreat role in cardioplegic arrest (CP) and reperfusion-related microvascular dysfunction in human coronary resistance arterioles and regulatory properties in this vascular bed.Studies have shown that altering the intracellular concentration of potassium hasa dramatic effect on the apoptotic process. Enhancing the efflux of potassium has been shown to augment apoptosis. In a separate study, apoptotic nuclease and caspase enzymes activity was shown in vitro to be prevented by increasing concentrations of potassium.