RESPIRATORY SYSTEM MECHANICS IN PATIENTS TREATED WITH ISOTONIC OR HYPERTONIC NACL SOLUTIONS

Twenty-one patients who underwent elective surgery for coronary artery bypass were studied right after chest wall closure. They were anesthe tized, paralyzed, and artificially ventilated with a constant-flow ven tilator. Airflow, changes in lung volume, and tracheal pressure were m easured. Respiratory system resistance (Rrs,max) was partitioned into its homogeneous (Rrs,min) and uneven (Rrs,u) components. Respiratory s ystem elastance (Ers) was also measured. The subjects were randomly di vided into two groups injected with test solutions just after chest wa ll closure: eleven patients received isotonic saline (0.9% NaCl soluti on), whereas the remaining ten were injected with hypertonic saline (7 .5% NaCl solution). In all patients, mechanical parameters were measur ed at six different times: just before infusion, at 5 and 10 min (end of infusion); and at 15, 20, and 25 min after beginning of injection. No statistically significant differences were observed in respiratory system mechanical parameters between groups or between different times within each group. Our data suggest that hypertonic saline infusion d oes not result in significant changes in respiratory system mechanics in patients submitted to coronary artery bypass.