Influence of splenectomy on hemodynamics during cardiac tamponade.

The effect of prior splenectomy on the hemodynamics of cardiac tamponade was investigated in 15 closed-chest pentobarbital sodium-anesthetized dogs. Hemodynamics were compared at baseline and during staged cardiac tamponade (pericardial pressures of 5, 10, and 15 mmHg) at control (n = 15) and after splenectomy (n = 8) and sham operation (n = 7). The fall in mean arterial pressure with cardiac tamponade was significantly greater in splenectomized dogs than in either sham-operated or control dogs (P less than 0.001). Cardiac output was more depressed at the third level of cardiac tamponade in splenectomized than in sham-operated or control dogs (12.8 +/- 14.5 vs. 29.3 +/- 8.7 and 25.4 +/- 9.4 ml.min-1.kg-1, respectively; both P less than 0.05 vs. splenectomy). Hemodynamic failure, defined as an inability to maintain mean arterial pressure greater than 50 mmHg for 5 min, occurred at a lower pericardial pressure in splenectomized than in sham-operated dogs (13.1 +/- 3.8 vs. 18.1 +/- 3.5 mmHg, P less than 0.05). Hematocrit increased significantly with cardiac tamponade in controls and sham-operated but not splenectomized dogs. The percent increase in hematocrit from baseline to the third stage of cardiac tamponade was 19.6 +/- 9.8 and 22.3 +/- 5.6% in control and sham dogs, respectively. Thus the canine spleen plays an important role in cardiovascular compensation to cardiac tamponade. Parallel changes in hematocrit suggest that a part of this response is due to splenic autotransfusion.