Α 60 kg male (80 years) was admitted to the Internal Medicine Clinic with serum sodium 168 mEq/L. Laboratory investigation showed serum glucose 120 mg/dL, urea 110 mg/dL, creatinine 1.8 mg/dL and potassium 4.2 mEq/L; V urine 1.2 L, urine sodium 25 mEq/L, urine potassium 40 mEq/L. Which of the following treatment schedules should be used for the appropriate patient's management? a. Normal saline 0.9%, 80 mL/h b. Half normal saline 0.45%, 260 mL/h c. Glucose solution 5%, 250 mL/h d. Ringer

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... solution, 120 mL/h The patient exhibited hypovolemic hypernatremia. Increased urea/creatinine ratio and low urine sodium suggest extracellular volume depletion. Thus, half-normal saline (0.45%) solution should be used. The calculated water deficit is: TBW = (Serum sodium-1) 140 = 0.5 × body weight (60 kg) × (168 140-1) = 6 L Taking into account that a decrease of serum sodium by 8 mEq/L should be achieved within the next 24 hours, 1.7 L of water should be given (at a rate of 70 mL/h). Additionally, the insensible water losses (40 mL/h), as well as the renal water losses should be taken into account. The latter can be estimated by the determination of electrolyte-free water clearance: C e H2O = V urine × (Urine sodium + potassium Serum sodium) = 480 mL (20 mL/h) Thus, the infusion rate of free water is: 70+40+20=130 mL/h 1 L of hypotonic (N/2) saline solution is a combination of 500 mL of free water and 500 mL of isotonic saline. Thus, about 260 mL/h of this solution must be administered to provide 130 mL/h of free water.