Hypotension is one of the most common findings in the intensive care unit (ICU) patient and requires prompt attention in order to avoid poor clinical outcomes. This chapter presents a case study of a 42-year-old morbidly obese female who was transferred to the ICU after being diagnosed with a subarachnoid hemorrhage due to a ruptured aneurysm of the right middle cerebral artery. The patient's hypotensive condition was corrected by fluid boluses to increase her filling pressure, guided by pulmonary capillary occlusion pressure (PCOP) and by starting the patient on norepinephrine infusion to increase her cardiac output and maintain her perfusion pressure as well. Cardiac output itself is determined by several interrelated factors: mainly preload, pump function, and afterload. Basic principles of physiology help with the differential diagnosis of hypotension. Prompt management of hypotension often requires invasive monitoring, fluid resuscitation, and the use of vasopressor or inotropic therapy.