<prompt> A 68-year-old hypeensive man undergoes successful repair of a ruptured abdominal aoic aneurysm. He receives 9 L Ringer lactate solution and 4 units of whole blood during the operation. Two hours after transfer to the surgical intensive care unit, the following hemodynamic parameters are obtained: systemic blood pressure BP 9060 mm Hg, pulse 110 beats per minute, central venous pressure CVP 7 mm Hg, pulmonary aery pressure 2810 mm Hg, pulmonary capillary wedge pressure PCWP 8 mm Hg, cardiac output 1.9 Lmin, systemic vascular resistance 1400 dynescm5 normal is 900-1300, PaO2 140 mm Hg FiO2 : 0.45, urine output 15 mLh specific gravity: 1.029, and hematocrit 35. Given this data, which of the following is the most appropriate next step in management?Administration of a diuretic to increase urine outputAdministration of a vasopressor agent to increase systemic blood pressureAdministration of a fluid challenge to increase urine outputAdministration of a vasodilating agent to decrease elevated systemic vascular resistance  <response>: A ruptured abdominal aneurysm is a surgical emergency often accompanied by serious hypotension and vascular collapse before surgery and massive fluid shifts with renal failure after surgery. In this case, all the hemodynamic parameters indicate inadequate intravascular volume, and the patient is therefore suffering from hypovolemic shock. The low urine output indicates poor renal perfusion, while the high urine-specific gravity indicates adequate renal function with compensatory free-water conservation. The administration of a vasopressor agent would ceainly raise the blood pressure, but it would do so by increasing peripheral vascular resistance and thereby fuher decrease tissue perfusion. The deleterious effects of shock would be increased. A vasodilating agent to lower the systemic vascular resistance would lead to profound hypotension and possibly complete vascular collapse because of pooling of an already depleted vascular volume. This patients blood pressure is critically dependent on an elevated systemic vascular resistance. A diuretic would exacerbate the patients existing volume depletion. To properly treat this patient, rapid fluid infusion and expansion of the intravascular volume must be undeaken. This can be easily done with lactated Ringer solution or blood or both until improvements in such parameters as the PCWP, urine output, and blood pressure are noted. 