Cardiovascular responses and changes in plasma cation levels associated with infusion of hyperosmolar urea solutions

In four patients, infusion of a hyperosmolar solution of urea to decrease brain volume was associated with hypotension and a decreasing of plasma levels of ionized calcium. This prompted a further study into the effects of intravenous hyperosmolar urea solutions on cardiovascular function and plasma levels of cations in the anesthetized dog. Using an infusion rate of 250 mg/kg/min, significant (p less than 0.05) reductions in mean arterial pressure, systemic vascular resistance, hematocrit, and levels of plasma sodium and ionized calcium were found. These changes were associated with significant (p less than 0.05) increases in cardiac output, right atrial pressure, arterial PO2 and PCO2, and levels of plasma potassium. It is concluded that rapid infusions of hyperosmolar urea may have important effects of hemodynamic status and plasma cation concentrations.