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Diverse Causes of Prolonged Mechanical Ventilation Following CABG

Doctor's Guide

Prolonged mechanical ventilation (PMV) arises from diverse causes that vary over time and in their impact on ventilation duration following coronary artery bypass grafting (CABG).

Researchers from the Physician Research Network, Methodist Healthcare University Hospital, Memphis, Tennessee, United States, enrolled 400 patients undergoing CABG. Using their standardized post-operative respiratory protocol, 41.8 percent of patients could not be extubated at eight hours. The authors designated these patients as “failure to be extubated” (FTE).

Depressed consciousness was the most common reason for FTE, accounting for 34.7 percent of cases. In 30.5 percent of the FTE cases overall, prolonged sedation from the anaesthetic accounted for the depressed consciousness. Tachypnea induced by acid-base disturbances accounted for 16.2 percent of FTE cases. On the other hand, cardiovascular instability rarely cased FTE. Four patients had multiple reasons for FTE at eight, 24 and 48 hours.

Another 6.8 percent of the cohort could not be extubated at 24 hours, and another 5.3 percent could not be extubated at 48 hours. These were designated as requiring PMV greater than 24 hours and PMV greater than 48 hours, respectively.

Hypoxemia accounted for 55.6 and 61.9 percent of PMV cases after 24 and 48 hours respectively and arose from a variety of causes including cardiogenic and non-cardiogenic pulmonary oedema, as well as pneumonia. However, there were also cases of “hypoxemia of unknown aetiology.”

Tachypnea induced by acid-base disturbances accounted for 11.1 of cases of PMV for greater than 24 hours. Finally, postoperative bleeding accounted for PMV in 18 of the 48 (37.5 percent) patients.

The authors concluded that PMV arises from a variety of causes. These causes vary over time and in their impact on ventilation duration following CABG.

Chest 2002;122:245-52.

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