PROSPECTIVE EVALUATION BY COMPUTED-TOMOGRAPHY AND PULMONARY-FUNCTION TESTS OF CHILDREN WITH MEDIASTINAL MASSES

Background. Our ability to predict respiratory compromise during gener al anesthesia in a child with an anterior mediastinal mass is limited. Two prior reports have found a correlation between adequacy of ventil ation during general anesthesia and the tracheal cross-sectional area obtained from computed tomograms (computed tomography [CT] scans). The se and other reports have suggested that pulmonary function tests may provide additional information regarding anesthetic risks, but no stud ies have evaluated the extent of respiratory compromise in children wi th an anterior mediastinal mass. Methods. We prospectively evaluated 3 1 children with mediastinal masses before 34 surgical procedures. At e ach evaluation the tracheal area (as a percent of the predicted area o n the basis of age and gender) was determined by CT. Pulmonary functio n tests were performed in the sitting and supine positions. The eleven children with either a tracheal area or peak expiratory flow rate (PE FR) of less than 50% of predicted received only a local anesthetic; th e majority of children above these levels (17 of 22) received a genera l anesthetic. Results. Eleven of 31 patients had significant pulmonary restriction as defined by total lung capacity of less than 75% of pre dicted. Eight patients had a PEFR in the supine position of less than 50% of predicted. PEFR was lower in the supine than the upright positi on in all patients (median value of decrease, 12%). In 28 of 34 evalua tions the child had a tracheal area greater than 50% of predicted, a c riterion proposed for safe uttilization of general anesthesia. This la tter guideline, however, did not identify all patients with significan t impairment of pulmonary function; five patients had a PEFR of less t han 50% of predicted but tracheal areas of greater than 50% of predict ed. All children were administered anesthetics uneventfully with these guidelines. Conclusions. Although the tracheal area can be accurately measured with the CT scan, this does not identify all children with m ediastinal masses and abnormal pulmonary function. A large mass may pr oduce significant restrictive impairment and hence reduction in PEFR b y the intrathoracic volume it occupies and yet not cause tracheal comp ression. It may also reduce the PEFR by narrowing the bronchi distal t o the carina. Currently no CT standards exist for measuring bronchial areas in children. Our study did not evaluate whether impaired pulmona ry function as measured by PEFR would be predictive of respiratory col lapse during general anesthesia because all were excluded and operated on under local anesthesia. General anesthesia was well tolerated in c hildren with tracheal area and PEFR greater than 50% of predicted. Pul monary function tests in children with anterior mediastinal masses may add valuable information to the anatomic evaluation obtained by CT sc an.