Effect of delayed sternal closure after cardiac surgery on respiratory function in ventilated infants

Objective. Studies examining the effect of sternal closure on respiratory f unction have not been published, and currently there is little evidence to guide ventilation management immediately after closure. The aim of this stu dy was to establish the impact of delayed sternal closure on expired tidal volume, respiratory system compliance, and CO2 elimination immediately afte r the procedure in infants who had undergone open heart surgery. Design: Prospective study of respiratory function before and after delayed sternal closure. Setting. Cardiac intensive care unit, Great Ormond Street Hospital, London. Patients., Seventeen infants (median age, 2 wks) with open median sternotom y incisions after cardiac surgery. Data were collected between August 1998 and March 2000. Interventions, Respiratory function was measured continuously for 30 mins b efore and after delayed sternal closure in paralyzed ventilated infants. Measurements and Results: Four babies were excluded from the study because they required either immediate increase in ventilation after delayed sterna l closure (n = 3) or removal of pericardial blood collection (n = 1). In th e remaining 13 infants, expired tidal volume and CO2 elimination decreased significantly (p < .005) by a mean of 17% and 29%, respectively, after ster nal closure. In five of the remaining 13 patients, the magnitude of trachea l tube leak increased by greater than or equal to 10% after delayed sternal closure, thereby invalidating recorded changes in respiratory system compl iance. Of the eight infants in whom there was a minimal change in leak, res piratory system compliance decreased significantly (p < .05) by a mean of 1 9%. Conclusions. This study supports the hypothesis that respiratory function m ay be compromised after delayed sternal closure and that ventilatory suppor t should be increased to counteract the anticipated decrease in tidal volum e. Extra vigilance should be applied in monitoring blood gases after delaye d sternal closure to assess clinical responses to sternal closure or change s in ventilatory support. Accurate assessment of change in respiratory syst em compliance after any therapeutic intervention may be precluded by change s in tracheal tube leak during the procedure.