Mechanical ventilation commonly is associated with patient agitation requiring sedation to alleviate discomfort and reduce excessive central respiratory drive. Upon recovery from acute respiratory failure, sedation is reduced to facilitate the withdrawal of ventilatory support. In some patients, abrupt reduction in sedation provokes severe agitation that causes catecholamine release resulting in severe hypertension, tachycardia and tachypnea. This requires increased sedation to bring hemodynamic and respiratory function under control.

Dexmedetomidine is an alpha-2 receptor agonist with both sedative and analgesic properties that allows for the reduction in the anesthetic and analgesic requirements in the perioperative setting. In addition to its sedative effects, alpha-2 receptor stimulation in the central nervous system inhibits sympathetic activity and reduces plasma epinephrine and norepinephrine levels, thereby lowering both arterial blood pressure and heart rate. Because alpha-2 receptor stimulation does not cause respiratory depression, dexmedetomidine may facilitate the transition to unassisted breathing in profoundly agitated patients. The investigators will prospectively evaluate dexmedetomidine in 30 patients who could not be extubated because of agitation with hemodynamic instability and tachypnea.

The purpose of this study is to test if a larger prospective randomized controlled pilot study can show that dexmedetomidine facilitates weaning and extubation in patients who have failed previous attempts because of agitation and hyperdynamic cardiopulmonary response.