Mannitol diuresis is generally provided by injecting a 10% or 20% solution of mannitol at a dose of 0.5-1.5 g / kg body weight. A patient weighs 180 lbs and we wish to give a dose of 1. 0 g /kg.
Plasma creatinine is 1.1 mg %. The ECF is 15 L in this person. The formula weight of mannitol is 182.17 g/mol.
a. How much 20% mannitol should we infuse?
b. Urine flow before administration of mannitol was 1.0 mL/min with a creatine concentration of 1.09 mg/mL. What is the GFR?
c. Suppose that the person is at maximum antidiuresis, with a urine flow of 0.5 mL/min prior to mannitol injection, with a urine osmolarity of 1200 mOsM. What is the increase in urinary flow rate caused by mannitol infusion?
d. How does (mechanism) mannitol increase urine flow?