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Ann Thorac Surg 1995;59:1153-1154
© 1995 The Society of Thoracic Surgeons
Greater Victoria Hospital Society Victoria, British Columbia Canada
Hornick and associates have questioned the usefulness of the immediate postoperative chest radiograph after adult cardiac operations, a routine that has been followed faithfully in most postsurgical care units since their inception. The proposal to abolish this early postoperative radiograph, in the absence of specific clinical indications, is very attractive in today's economic climate. In another setting, Silverstein and associates [1] reported an extremely low yield of clinically significant and unsuspected new cardiopulmonary findings or device malpositions in a prospective evaluation of 525 routine morning chest radiographs in two surgical intensive care units and concluded that the need for a routine daily chest radiograph should be based on clinical necessity. It does seem rational to expect that shorter-acting anesthetic agents, better intraoperative myocardial preservation, improved surgical technique, and shorter bypass times should lead to fewer postoperative complications and the need for fewer assessments. This assumes that these advances in care are not offset by increased age and poorer ventricular function of the patient population and the increase in number and complexity of grafts done.
There are a few specific situations relevant to cardiac surgery and the postoperative radiograph that should be considered. Bilateral internal mammary artery grafts have been shown to be associated with a higher incidence of respiratory complications including clinically significant diaphragmatic dysfunction [2]. Gastroepiploic artery grafting can be associated with air under the diaphragm, which could confuse subsequent diagnosis in the (albeit rare) instance of an abdominal crisis. Physical examination cannot identify invariably an expanding pneumothorax (the post–chest tube removal radiograph, another routine, is done for this very purpose). Some surgical staff may not make a point of communicating all their intraoperative difficulties and anticipated postoperative complications (eg, possible pneumothorax) to the staff in the postoperative unit. Chest radiographs may be needed to check positions of central venous catheters unless pressure-guided pulmonary artery catheters always are used. The mediastinum in the post–open heart radiograph is 35% wider on average than in the preoperative radiograph [3] and thus provides a better comparison with subsequent chest radiographs to help confirm postoperative bleeding (recognizing that the echocardiogram has replaced the chest radiograph in the diagnosis of pericardial tamponade).
Although the residents involved in this study did not interpret correctly (according to the radiologist and staff surgeon) 11% of the radiographs, including two of patients with lobar collapse and four of patients with pleural effusion, the clinical management followed by the resident was deemed to be correct by the consultant cardiac surgeon in all cases. It has long been recognized that post–cardiac surgical patients have a high incidence of atelectasis, effusion, and consolidation (and, to a lesser extent, pulmonary congestion), as demonstrated by an early marked fall in arterial oxygen tension [4]. Consequently, most centers have an established postoperative respiratory management regimen to address these anticipated changes, as was undoubtedly the case in Hornick and associates' unit.
It is fallacious to argue that a chest radiograph should be done to confirm the presence or extent of an abnormality if nothing more can be done to improve it beyond the usual regimen, but is this always the case? Light's group [5] found that the combination of atelectasis and pleural changes on the chest radiograph correlated with more significant gas exchange abnormalities than either finding alone. Valta's group [6] showed that the application of 10 cm H2O or more of positive end-expiratory pressure caused significant and lasting recruitment of atelectatic lung units. The application of increased positive end-expiratory pressure might be particularly important to improve postextubation arterial oxygen tension, in units where early extubation is practiced.
We are indebted to Hornick and associates for reminding us that all routine screening procedures should be assessed regularly for usefulness. I agree that the immediate postoperative chest radiograph may not always be useful and may even be a threat to the patient's hemodynamic stability if elevating the patient's thorax to position the film is required. Although much can be determined on the basis of clinical examination of the patient and the blood gas results, each cardiac surgical unit should first examine its own practices and review its own protocols before eliminating the routine immediate postoperative chest radiograph on the basis of this relatively small study.
References
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