General Medical Information

Postoperative Hypotension

David M. Barrs

As in hypertension, precipitating factors for hypotension must be found and treated. Hypovolemia secondary to inadequate fluid replacement or hemorrhage is the most likely cause of postoperative hypotension. Others include preoperative and intraoperative anesthetic agents and medications, pain, sepsis, cardiac dysfunction (e.g., arrhythmias, infarction, failure), pulmonary problems (e.g., inadequate ventilation, emboli, pneumothorax), and electrolyte abnormalities. If a central venous line is not available to monitor intravascular volume, a fluid challenge consisting of 250 to 500 mL of normal saline can be given over 10 to 15 minutes. Clinical examination of the jugular venous pressure can guide replacement, and the infusion may be repeated once or twice. If no improvement is evident, a complete cardiac and pulmonary evaluation is indicated. The patient should have a chest radiograph, ECG, arterial blood gas sample, blood cultures if febrile, and insertion of monitoring catheters (e.g., central venous, arterial, and pulmonary artery lines). Vasopressor medication is indicated if significant hypotension is present (i.e., systolic pressure less than 100 mm Hg) and the patient manifests symptoms of decreased profusion, such as obtundation, cardiac insufficiency, or decreased urinary output.