Effect of diaphragmatic lymphatic contamination on caudal mediastinal node lymph flow in unanesthetized sheep

Our purpose was to determine the effect of diaphragmatic lymphatics on steady state caudal mediastinal node (CMN) or lung lymph flow in the unanesthetized sheep. After standard lung lymph fistula preparation, in which the CMN efferent was cannulated, nine sheep had an additional extensive cautery procedure in the right chest along the esophagus and diaphragm to sever any systemic lymphatics entering the CMN. This was followed by a similar cautery procedure on the left side, one week later. There was no difference in steady state lymph flow, QL, or in the lymph-to-plasma, L/P protein ratio in any paired study when comparing the bilateral cautery procedure with the right side alone, nor was there any difference in these parameters when this data was compared with that from thirty standard lymph fistula preparations. In addition, diaphragmatic lymphatics were cannulated in five sheep. Mean QL immediately post-surgery was 1.6 +/- 0.4 ml/hr compared to a CMN QL of 6.1 +/- 0.4 ml/hr. By six hours after surgery, diaphragmatic QL decreased to 0.4 +/- 0.2 while CMN flow remained relatively steady. We conclude that residual diaphragmatic lymphatics, if any, entering the caudal mediastinal lymph node, not removed by the standard preparation do not appear to affect steady state CMN lymph flow or L/P ratio, in the normal unanesthetized sheep, especially if measurements are obtained at least 6 hours after surgery.