LIQUID AND PROTEIN DYNAMICS USING A NEW MINIMALLY INVASIVE PLEURAL CATHETER IN RABBITS

To obtain continuous access to the pleural space without causing injury, we tested a new transdiaphragmatic pleural catheter for its ability 1) to drain the pleural space without injury and 2) to drain liquid at a rate equal to normal pleural liquid production. In 13 anesthetized rabbits, we opened the abdomen and dissected through the diaphragm to insert a flared-tip catheter into the ventral pleural space on one side and then turned the rabbit prone. In 10 of the rabbits (8 for 6 h, 2 for 24 h), we continuously collected draining pleural liquid, and in 3 rabbits (6 h), we did not open the catheter. We injected radiolabeled albumin intravenously as a protein marker. Terminally, we collected pleural liquid from both pleural spaces and lavaged for total radioactivity. In 14 awake control rabbits without catheters, we measured normal pleural liquid production by the rate of equilibration of radiolabeled albumin from plasma to pleural liquid. We found that, although the percentage of neutrophils was increased on the side with the catheter (54 vs. 1% in control rabbits), the pleural liquid volume, protein concentration, specific activity of albumin, and total radioactivity in the pleural space were the same on the side with the catheter as on the opposite side and in the control rabbits. The liquid flow rate through the catheter over 6 h was 53 +/- 23-mu-l/h [0.017 +/- 0.008 (SD) ml.kg-1.h-1], which was not significantly different from the computed rate of normal pleural liquid production in the control rabbits, 49 +/- 14-mu-l/h (0.016 +/- 0.004 ml.kg-1.h-1). This new catheter provides continuous access to the rabbit pleural space for at least 6 h without injury.