Elevated pulmonary dead space and coagulation abnormalities suggest lung microvascular thrombosis in patients undergoing cardiac surgery.
OBJECTIVE
Inflammation has been shown to trigger microvascular thrombosis. Patients undergoing cardiac surgery sustain significant inflammatory insults to the lungs and in addition are routinely given anti-fibrinolytic agents to promote thrombosis. In view of these risk factors we investigated if evidence of pulmonary microvascular thrombosis occurs following cardiac surgery and, if so, whether a pre-operative heparin infusion may limit this.


METHODS
Double-blind randomised controlled trial.


METHODS
Tertiary university affiliated hospital.


METHODS
Twenty patients undergoing elective cardiac surgery.


METHODS
Patients were randomised to receive a pre-operative heparin infusion or placebo. All patients were administered aprotinin.


RESULTS
Pulmonary microvascular obstruction was estimated by measuring the alveolar dead-space fraction. Pulmonary coagulation activation was estimated by measuring the ratio of prothrombin fragment levels in radial and pulmonary arterial blood. Systemic tissue plasminogen activator (t-PA) levels were also assessed. In the placebo group cardiac surgery triggered increased alveolar dead-space fraction levels and the onset of prothrombin fragment production in the pulmonary circulation. Administration of pre-operative heparin was associated with a lower alveolar dead-space fraction (p < 0.05) and reduced prothrombin fragment production in the pulmonary circulation (p < 0.05). Pre-operative heparin also increased baseline t-PA levels (p < 0.05).


CONCLUSIONS
The changes in the alveolar dead-space fraction and pulmonary coagulation activation suggest that pulmonary microvascular thrombosis develops during cardiac surgery and this may be limited by a pre-operative heparin infusion.
Dixon
Barry
B
Intensive Care Unit, St. Vincent's Hospital, 3065, Melbourne, Victoria, Australia. barry.dixon@svhm.org.au
Campbell
Duncan J
DJ
Santamaria
John D
JD
D000925:Anticoagulants / Q000008:administration & dosage / Q000627:therapeutic use*; D007611:Aprotinin / Q000627:therapeutic use*; D002315:Cardiopulmonary Bypass; D001026:Coronary Artery Bypass; D004311:Double-Blind Method; D005260:Female; D006490:Hemostatics / Q000627:therapeutic use*; D006493:Heparin / Q000008:administration & dosage / Q000627:therapeutic use*; D006801:Humans; D007249:Inflammation / Q000150:complications / Q000209:etiology; D007902:Length of Stay; D008173:Lung Diseases, Obstructive / Q000209:etiology* / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000517:prevention & control*; D011300:Preoperative Care; D012126:Respiratory Dead Space; D013927:Thrombosis / Q000209:etiology / Q000517:prevention & control*; D010959:Tissue Plasminogen Activator / Q000097:blood
D000925:Anticoagulants; D006490:Hemostatics; D006493:Heparin; D007611:Aprotinin; D010959:Tissue Plasminogen Activator