Myocardial protection against global ischaemia by preconditioning: Studies in rabbit myocardium and humans undergoing cardiac surgery.

The presence of pericardial adhesions prolongs the operation time and increases the risk of serious damage to the heart and other major vascular structures during resternotomy. The reported incidence of such damage is 2-6[percent]. Pericardial mesothelial cells have regenerative potential and exhibit fibrinolytic activity. The pericardial mesothelium therefore has the capacity to recover following cell loss or damage and has an actual or potential role in the break down of the fibrinous adhesions that serve as the initial scaffolding for the firm collagenous adhesions seen at reoperative surgery. These features of the pericardium may have been underestimated in much of the previous research into pericardial substitution. The studies in this thesis have demonstrated That during cardiac surgery there is a significant reduction in the pericardial fibrinolytic activity in comparison to initial activity. The recovery in fibrinolytic activity that occurs towards the end of the surgical procedure and afterwards never reaches the preoperative magnitude. That during cardiac surgery, simultaneous with the changes in the fibrinolytic activity, increasing pericardial inflammation occurs with a concomitant increase in mesothelial damage. Permanent residual damage is apparent in the reoperative pericardium. That during the reduction in pericardial fibrinolytic activity the simultaneous plasma tPA activity rises to a peak suggesting that the fall in pericardial fibrinolytic activity independent of the plasma tPA and haemodilution. That the cellular content of pericardial fluid is mainly mesothelial which may therefore contribute to mesothelial regeneration and recovery. The pericardial fluid, by virtue of its enzyme content, has the potential to take part in fibrinolytic activity. That the polyhydroxybutyrate pericardial patch does not confer any obvious short-term reoperative advantage in calves exposed to CPB surgery