• Michael D Sharpe, Barbara van Rassel, and Wael Haddara.
• Department of Anesthesia and Perioperative Medicine, London Health Sciences Centre - University Hospital, Schulich School of Medicine and Dentistry, Western University, 339 Windermere Road, London, ON, N6A 5A5, Canada, michael.sharpe@lhsc.on.ca.
• Can J Anaesth. 2013 Oct 1;60(10):998-1002.

BackgroundThyroxine (T4) administration is advocated in the management of organ donors; however, the bioavailability of oral thyroxine is unknown in this patient population.ObjectiveThe primary objective of this study was to compare the percentage of the study time (from study drug administration to organ procurement) that patients in the oral vs the intravenous group required inotropic support. Secondary objectives included plasma levels of T3 and T4 and number of organs donated following oral vs intravenous T4 administration.DesignRandomized double-blinded study.SettingAdult medical-surgical intensive care unit.PatientsThirty-two adult solid organ donors.InterventionsPatients were randomized to receive either an oral or intravenous dose of T4 (2 μg·kg⁻¹). All patients received an oral and intravenous study drug preparation, one of which was a placebo. The study was double-blinded, and randomization occurred in blocks of four and six.MeasurementsThe number and duration of inotropic/vasopressor therapies and free serum levels of T3 and T4 were determined hourly until procurement.Main ResultsFollowing T4 administration, all patients remained on inotropic/vasopressor therapy for the same mean (SD) duration [93 (3)%] of the study period. There was a similar and gradual decrease in the number and dosages of inotropes/vasopressors required in both groups. There was no difference in T3 or T4 levels between groups. Oral bioavailability of T4 was 93% of the intravenous group at six hours and 91% overall. At six hours, the mean area under the curve for T4 was similar between the intravenous group [92.2 (33); 95% confidence interval (CI) 76 to 108.4] and the oral group [86.1 (14); 95% CI 79.4 to 92.8].ConclusionsOrally administered T4 is well absorbed and achieves a bioavailability of approximately 91-93% of intravenous T4 in organ donors. Inotropic/vasopressor requirements and hemodynamic responses following oral or intravenous thyroxine administration were comparable. Oral T4 is suitable for hormonal therapy for organ donors. This trial was registered at www.clinicaltrials.gov : NCT00238030.

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