Infant Thoracic Surgery: Procedure-Dependent Pulmonary Response By Jay S. Greenspan, Deborah A. Davis, Pierantonio Russo, Geovanni Speziali, Michael J. Antunes, Alan R. Spitzer, and Thomas H. Shaffer Philadephia, Pennsylvania l Respiratory insufficiency is a common complication of thoracic surgery in infants. To better define this dysfunction, pulmonary compliance (CL) and resistance (R) were mea- sured for 17 infants who underwent common thoracic proce- dures: Blalock-Taussig shunting (n = 7) repair of congenital coarctation of the aorta (n = 10). Measurements were ob- tained preoperatively and 0, 1, and 3 days postoperatively. Preoperatively, CL was lower and R was similar for the two groups. Both groups had decreased CL and increased R on postoperative day 0; infants with coarctation had recovery to preoperative values by postoperative day 1 for CL, and day 3 for R. CL and R did not return to the preoperative values by postoperative day 3 in infants with a shunt procedure. The changes in R were greater than those in CL for both groups in the postoperative period. These data indicate that such thoracic procedures are associated with pulmonary morbid- ity that is airway-predominant, and that the degree of compromise and the time until recovery are, in part, proce- dure-specific. Copyright o 1996 by W.B. Saunders Company INDEX WORDS: Pulmonary compliance, pulmonary resis- tance, Blalock-Taussig shunt, coarctation of aorta. ESPIRATORY R INSUFFICIENCY is common among infants who have undergone thoracic surgery; up to 40% of infants require prolonged ventilator support after cardiac procedures.la2 This dysfunction may be related to perioperative alter- ations in lung airway or parenchymal function, which can be differentiated and quantified by measures of pulmonary mechanics. Pulmonary compliance (CL) measures predominantly lung parenchymal function, and pulmonary resistance (R) assesses airway func- tion.3-5 An understanding of the postoperative change in pulmonary mechanics would be useful in determin- ing the etiology of the dysfunction and in guiding appropriate therapy for compromised infants. In addition, a detailed assessment of subtle changes in lung function after simple thoracic procedures may alert clinicians to potential complications in these From the Department of Pediatrics, Thomas Jefferson Medical College; the Departments of Anesthesiology and Physiology, Temple University School of Medicine; and the Department of Cardiothoracic Surgery The Medical College of Pennsylvania and Hahnemann Universily School of Medicine, Philadelphia, PA. Address reprint requests to Jay S. Greenspan, MD, Division of Neonatology, Thomas Jefferson University Hospital, College Building Suite 700, 1025 Walnut St, Philadelphia, PA 19107. Copyright o 1996 by KB. Saunders Company 0022-3468/96/3107-0002$03.OOlO 878 infants and may help predict areas of compromise after more complicated procedures. We hypothesized that infants who have undergone thoracic procedures have preoperative and immedi- ate postoperative pulmonary dysfunction specific to their type of surgical procedure. To test this hypoth- esis, we measured CL and R immediately preopera- tively, and sequentially postoperatively, in infants who had one of two commonly performed thoracic procedures: Blalock-Taussig shunting or repair of coarctation of the aorta. MATERIALS AND METHODS The study was approved by the Institutional Review Board, and parental informed consent was obtained. The study group con- sisted of 17 full-term infants with either congenital coarctation of the aorta without a ventricular septal defect (n = 7; study weight, 3.24 2 0.6 kg [mean -r- SD]) or cyanotic heart disease (n = 10; study weight, 3.3 ? 0.3 kg) and required surgical intervention before 1 month of age. No member of the study population, had known primary pulmonary pathology, and all were free of intercur- rent illness. All were considered stable by the surgical team and were on minimal ventilator support or were breathing spontane- ously. Each infant required at least 24 hours of mechanical ventilation in the immediate postoperative period. The study population underwent correction of the coarctation of the aorta with end-to-end anastomosis or a modified Blalock- Taussig shunting procedure with an artificial graft (W.L. Gore and Associates, Elkton, MD), with standard anesthesia and monitor- ing. In the postoperative period, prostaglandin E1 infusion was discontinued. The ductus arteriosus was ligated surgically in the infants with coarctation, and was allowed to close spontaneously in the infants who received a shunt. Routine postoperative care was maintained by the surgical intensive care staff and included mechanical ventilation, inotropic and vasodilatory support, and fluid administration as necessary to maintain stable hemodynamic parameters. Ventilation was per- formed with a pressure-limited, time-cycled ventilator initially set at: respiratory rate of 20 to 30 breaths per minute, positive end-expiratory pressure of 4 to 5 cm H20, and positive inspiratory pressure necessary to achieve adequate chest excursion byvisualiza- tion (25 to 35 cm HlO). Thereafter, mechanical support was altered to maintain the desired alveolar ventilation (PCOZ of 40 to 45 mm Hg) and oxygenation (oxyhemoglobin saturation of approxi- mately 80% in the shunted group, and more than 94% in the repaired coarctation group). The patients were given a trial of extubation when hemodynamics and gas exchange normalized on minimal support. For the purposes of this study, the physicians caring for the infants were blinded to the results of the pulmonary function testing. Preoperative pulmonary function tests were performed just before the surgical procedure, with the infant on mechanical ventilator support. Thereafter, pulmonary function tests were performed on the same day as the surgery (postoperative day 0) and on the first and third postoperative days. CL and R were ~ourna/ofPediatric Surgery, Vol31, No 7 (July), 1996: pp 878-880