Antithrombin III in patients with severe sepsis: a pharmacokinetic study

To evaluate the safety, pharmacokinetics, and the practicability of two different antithrombin III (AT III) high-dose regimens in patients with severe sepsis.

Prospective, open, randomized, 2 parallel groups, multinational clinical trial.

Eleven academic medical center intensive care units (ICU) in Austria, Belgium, Denmark, Germany, Norway and Sweden.

Thirty-three patients with severe sepsis who received standard supportive care and antimicrobial therapy, in addition to the administration of AT III.

Patients received an intravenous loading dose of 6,000 IU AT III followed by either intermittent bolus infusions of 1,000 IU AT III every 4 h or a continuous infusion of 250 IU AT III/h for 4 days, resulting in a total dose for both dosage regimens of 30,000 IU AT III.

All patients were evaluated for safety and all but one for pharmacokinetics.

The administration of AT III was safe and well tolerated. The overall 28-day all-cause mortality was 30% (43% intermittent bolus infusions; 21% continuous infusion). The mean probability of dying according to the SAPS II was 48%. The difference in mortality between both groups was within the range of chance. AT III plasma levels were elevated from low baseline levels to above 120% soon after onset of AT III therapy and remained at these levels for the treatment phase of 4 days. Functional and immunologic levels of AT III corresponded very well. With an overall median volume of distribution of 4.5 l (range: 2.4-6.5 l), AT III only moderately extended beyond plasma. The overall median elimination half-life was 18.6 h (range: 5.1-37.4). Overall, median response was 1.75% per IU/kg (range: 1.14-2.8). The variability of elimination parameters was quite noteworthy (CV = 41-59%), whereas distribution-related parameters showed a moderate variability (CV = 24%). In spite of this variability, both high-dose IV regimens reliably provided AT III levels above 120% for all but one patient. An increased mortality was observed for patients with a distribution volume exceeding 4.5 l (or a response < 1.7% per IU/kg). AT III distribution volumes above 4.5 l might indicate a capillary leak phenomenon. The continuous infusion regimen was slightly preferred by the investigators with regard to practicability.