Bleeding after Perfusion for Open Heart Surgery

The use of extracorporeal circulations for open cardiac surgery has presented many new and unique problems. One of these is a disturbance of blood-clotting due to passage of the blood through the circuit of the pump and oxygenator. A haemorrhagic state may follow perfusion of a patient. It has been attributed to a deficiency of one or other of the coagulation elements in the blood, and these are discussed later. One additional factor which can contribute to the haemorrhagic state is the presence of unneutralized heparin after perfusion. The detection and elimination of this is important and is the subject of this paper. An anticoagulant is essential in extracorporeal circulations to maintain the fluidity of the blood and to protect the platelets and plasma-coagulation factors in the pump-oxygenator circuit. It must be potent, nontoxic, rapid in action, and be quickly and easily neutralized. Heparin best fulfils the requirements, and is the anticoagulant used for this type of surgery. The drug (2 mg. /kg.) is given to the patient immediately before perfusion with heparinized donor blood (20 mg./500 ml.) from the pump-oxygenator. For haemostasis at the end of the perfusion the circulating anticoagulant is neutralized by an antiheparin drug-commonly protamine sulphate. To ensure that this has been done adequately we have used a rapid and sensitive test for the detection of traces of heparin. This is the thrombin clotting-time of plasma, and it is described below. We have found by using this test that traces of heparin may remain in the bloodstream after protamine administration and be enough to prolong the oozing state post-operatively both in the experimental animal and in patients. "Oozing " is an apt description of this state with its slow, steady loss of blood necessitating careful haemostasis. The operation time is prolonged, further transfusion is required, and post-operative drainage is considerable. Haematomas may form in the wound and in the chest. In the early experimental work on dogs a number succumbed because of excessive bleeding before it was realized that the complete elimination of heparin was so important. Since following this policy we have had no serious bleeding after perfusion.