Background. Reamed intramedullary nailing causes an increase of intramedullary pressure. A new rinsing-suction reamer (RSR) can reduce this problem, and it was evaluated in animal experiments in comparison with the AO reamer (AOR) to see its effects on intramedullary pressure and fat intravasation. Methods: Reamed intramedullary nailing was performed in 14 sheep using the RSR or AOR. The following parameters were evaluated: intramedullary pressure, hemodynamics, blood tests, lung histology, and radiographs of the femur that was operated on. Results. Intramedullary pressure during reaming was significantly (p < 0.001) lower with RSR (9 min, 34 nun Hg; 9.5 mm, 4 min Hg; 10 nun, 1 mm Hg) than AOR (9 mm, 750 min Hg; 9.5 mm, 292 min Hg; 10 mm, 138 min Hg). There was a significantly (p < 0.05) higher increase of pulmonary resistance in AOR (from 144 84 dyne-s-cm(-5) to 391 169 dyne-s-cm(-5)) than in RSR (from 137 51 dyne-s-cm(-5) to 258 +/- 105 dyne-s-cm(-5)) after nailing and less intravenous fat measured in RSR (0.9; AOR, 2.9; p < 0.05) at all stages of reaming, at nail insertion (RSR, 0.3; AOR, 2.7; p < 0.05), and 30 seconds after nail insertion (RSR, 0.2; AOR, 1.1; p < 0.05) proved by the Gurd test. PCO2 increased (p < 0.05) in AOR (AOR, 36 +/- 5 vs. 40 +/- 7 min Hg; RSR, 33 4 vs. 32 3 min Hg) and pH dropped significantly (AOR, 7.49 +/- 0.06 vs. 7.45 +/- 0.05; RSR, 7.53 +/- 0.04 vs. 7.54 +/- 0.04; p < 0.05). Semiquantitative histologic analysis proved a significant higher pulmonary fat load in AOR (13.1 +/- 13.4) versus RSR (3.9 +/- 1.5, p = 0.00002). Conclusion:. Because we found only a minimal increase of the pulmonary arterial pressure as a sign of pulmonary embolism, we conclude that by using the RSR, the systemic side effects caused by intravasation of medullary content during reaming could be reduced as far as possible.