Depending on the patient, the type of surgery, and local practices, most patients are mechanically ven-tilated for 1–12 h postoperatively. Sedation may be maintained by a propofol or dexmedetomidine infusion. The emphasis in the first few postoperative hours should be on maintaining hemodynamic sta-bility and monitoring for excessive postoperativebleeding. Chest tube drainage in the first 2 h of more than 250–300 mL/h (10 mL/kg/h)—inthe absence of a hemostatic defect—is excessive and may require surgical reexploration. Subsequent drainage that exceeds 100 mL/h is also worrisome. Intrathoracic bleeding at a site not adequately drained may cause cardiac tamponade, requiring immediate reopening of the chest.
Hypertension despite analgesia and sedation is a common postoperative problem and should gen-erally be treated promptly so as not to exacerbate bleeding or myocardial ischemia. Nitroprusside, nitroglycerin, clevidipine, or nicardipine is gener-ally used. β Blockade may be particularly useful for patients recovering from coronary artery surgery.
Fluid replacement may be guided by fill-ing pressures, echocardiography, or by responses to treatment. Most patients present with relative hypovolemia for several hours following operation. Hypokalemia (from intraoperative diuretics) often develops and requires replacement. Postoperative hypomagnesemia is common in patients who receive no magnesium supplementation intraoperatively.
Extubation should be considered only when muscle paralysis has worn off (or been reversed) and the patient is hemodynamically stable. Caution should be exercised in obese and elderly patients and those with underlying pulmonary disease. Cardiothoracic procedures are typically associated with marked decreases in functional residual capac-ity and postoperative diaphragmatic dysfunction.