A phase 1 trial of nebulised heparin in acute lung injury.
BACKGROUND
Animal studies of acute lung injury (ALI) suggest nebulised heparin may limit damage from fibrin deposition in the alveolar space and microcirculation. No human studies have been undertaken to date. We assessed the feasibility, safety and potential anticoagulant effects of administration of nebulised heparin to patients with ALI.


METHODS
An open label phase 1 trial of four escalating doses of nebulised heparin was performed. A total of 16 ventilated patients with ALI were studied. The first group was administered a total of 50,000 U/day, the second group 100,000 U/day, the third group 200,000 U/day and the fourth group 400,000 U/day. Assessments of lung function included the PaO2/FiO2 ratio, lung compliance and the alveolar dead space fraction. Monitoring of anticoagulation included the activated partial thromboplastin time (APTT) and the thrombin clotting time. Bronchoalveolar lavage fluid was collected and the prothrombin fragment and tissue plasminogen activator levels were assessed. Analysis of variance was used to compare the effects of dose.


RESULTS
No serious adverse events occurred for any dose. The changes over time for the PaO2/FiO2 ratio, lung compliance and the alveolar dead space fraction levels were similar for all doses. A trend to increased APTT and thrombin clotting time levels was present with higher doses (P = 0.09 and P = 0.1, respectively). For the highest dose, the APTT reached 64 seconds; following cessation of nebulised heparin, the APTT fell to 39 seconds (P = 0.06). In bronchoalveolar lavage samples a trend to reduced prothrombin fragment levels was present with higher doses (P = 0.1), while tissue plasminogen activator levels were similar for all doses.


CONCLUSIONS
Administration of nebulised heparin to mechanically ventilated patients with ALI is feasible. Nebulised heparin was not associated with any serious adverse events, and at higher doses it increased APTT levels. Larger trials are required to further investigate the safety and efficacy of nebulised heparin. In these trials due consideration must be given to systemic anticoagulant effects.


BACKGROUND
Australian Clinical trials registry ACTRN12606000388516.
Dixon
Barry
B
Department of Intensive Care, St Vincent's Hospital, 41 Victoria Parade, Melbourne 3065, Australia. barry.dixon@svhm.org.au
Santamaria
John D
JD
Campbell
Duncan J
DJ
D000925:Anticoagulants / Q000008:administration & dosage*; D001780:Blood Coagulation Tests; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D005260:Female; D006493:Heparin / Q000008:administration & dosage*; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D009330:Nebulizers and Vaporizers; D010314:Partial Thromboplastin Time; D010446:Peptide Fragments / Q000032:analysis; D011498:Protein Precursors / Q000032:analysis; D011516:Prothrombin / Q000032:analysis; D012128:Respiratory Distress Syndrome / Q000188:drug therapy*; D012129:Respiratory Function Tests; D010959:Tissue Plasminogen Activator / Q000032:analysis
D000925:Anticoagulants; D010446:Peptide Fragments; D011498:Protein Precursors; C029733:prothrombin fragment 1; C044183:prothrombin fragment 2; D011516:Prothrombin; D006493:Heparin; D010959:Tissue Plasminogen Activator