Are Routine Chest X-Rays Needed After Cardiac Surgery?
ABSTRACT & COMMENTARY
Synopsis: While the results of this study do not settle the issue of whether chest x-rays are always necessary after cardiac operations, recent studies have identified other ICU patient populations and circumstances in which routine chest x-rays are definitely indicated.
Source: O’Brien W, et al. J Thorac Cardiovasc Surg 1997;113:130-134.
The authors of this study from the university of Toronto studied 423 patients admitted to their cardiothoracic ICU following cardiac operations. On admission, an evaluation form was completed by an anesthesia fellow who clinically assessed the positioning of the endotracheal and nasogastric tubes and the pulmonary artery catheter, and noted the results of arterial blood gases and pulse oximetry. This investigator then attempted to predict whether an abnormality would be present on chest x-ray, which the investigator also read.
Eighteen (4.5%) of 404 patients evaluated had abnormalities on the initial chest x-ray that were unsuspected clinically but required intervention. Unexpected abnormalities included abnormally placed endotracheal tubes in five patients, distal migration of the pulmonary artery catheter in eight, and pulmonary edema in one. A number of other abnormalities (lobar atelectasis, pulmonary edema, pleural effusions) were also present on the chest x-rays. The authors state that their "results clearly indicate that there is no need to perform routine chest roentgenography on patient admission to the cardiovascular ICU after heart operations."
COMMENT BY DAVID J. PIERSON, MD
Several flaws in the design of this study interfere with the confident acceptance of its results. It is unclear how patients were selected for inclusion. The statement that they represented "423 random patients (when an anesthesia fellow was on call)" is unclear, and if this is not either an inclusive, consecutive series or a randomly selected subset of all admitted patients, then the generalizability of the results becomes difficult. Were these only the uncomplicated cardiac surgery patients? The authors state that all patients were extubated within 4-6 hours of admission: Were those who could not be weaned and extubated within this period excluded or managed in a different unit?
In addition, having the same individual predict radiographic abnormalities and then read the chest x-ray introduces the possibility of bias in the results; it is unclear how the reported findings would compare to those by a trained radiologist uninvolved in the study. More importantly, considering that 4.5% of the patients had unexpected radiographic findings that led to prompt changes in management, and could have been associated with serious morbidity, the conclusion that routine chest x-rays are unnecessary in this setting seems open to challenge.
This study does not completely settle the question of whether a plain frontal chest radiograph should be obtained on all patients admitted to the ICU following heart operations, particularly if the surgery was uncomplicated. However, there are two other settings in which related questions have been addressed:
Daily chest x-rays in intubated, ventilated patients in the ICUIt has been controversial whether the "routine" daily chest radiograph is clinically useful and justifiable in terms of cost. Several studies have addressed this issue, including one by Hall et al (Crit Care Med 1991;19:689-693). These investigators compared daily bedside clinical assessments to detect complications or other changes with the results of daily chest radiographs in 74 intubated, ventilated ICU patients, for a total of 538 x-rays. Not surprisingly, two-thirds of the films showed no new findings. However, 30% of them had new findings considered to be of relatively minor importance (i.e., not requiring immediate intervention), most of which had not been suspected clinically. More importantly, there were 13 patients (18%) in whom a new major finding requiring immediate intervention was present on a routine daily chest x-ray that was not suspected clinically.
Routine chest x-rays following ICU proceduresGray et al (Crit Care Med 1992;20:1513-1518) studied 316 consecutive adult ICU patients who required central line placement or endotracheal intubation. The patients’ physicians filled out clinical evaluation forms immediately after each procedure and attempted to predict the likelihood that a new abnormality would be present on the film. A negative chest x-ray was correctly predicted in 151 of 152 cases of cordis catheter placement via subclavian or internal jugular route and also in 110 of 111 cases of pulmonary artery catheter placement. However, of 24 complications following multiple-lumen catheter placement, three were clinically unsuspected; also, 28 of 32 complications post-intubation were detected only on the radiographs. The authors of this study concluded that, with proper clinical assessment, it was not necessary to obtain a chest x-ray following subclavian, internal jugular, or pulmonary artery catheter placement unless a complication was suspected by the operator; they advised that chest x-rays be obtained after endotracheal intubations and multi-lumen catheter placement.
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