The authors present their comprehensive approach to evaluation of water and electrolyte dysbalances based upon synthesis of Siggard-Andersen model (Sodium-Potassium Double Chart), Shoker’s clearance approach [evaluation of ADH-kidney axis using electrolyte free water clearance (EWC)] and clinical evaluation of necessary input parameters (hydratation state, estimation of potassium stores). The addition of own algorithms enables the prediction of patient condition after water and salt supplementation. Comprehensive approach has a priority, while based on feasible models. Educational aspects have a capacity to be applied in real clinical situations.

        Key words: sodium cation – potassium cation – ADH – kidneys – electrolyte-free water clearance