title: Elevated pulmonary dead space and coagulation abnormalities suggest lung microvascular thrombosis in patients undergoing cardiac surgery.
abstract: 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.
authors.affiliation: Intensive Care Unit, St. Vincent's Hospital, 3065, Melbourne, Victoria, Australia. barry.dixon@svhm.org.au
authors.forename: Barry
authors.initials: B
authors.lastname: Dixon
authors.forename: Duncan J
authors.initials: DJ
authors.lastname: Campbell
authors.forename: John D
authors.initials: JD
authors.lastname: Santamaria
mesh_terms: 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
chemical_list: D000925:Anticoagulants; D006490:Hemostatics; D006493:Heparin; D007611:Aprotinin; D010959:Tissue Plasminogen Activator