Conference: 2008 International PHA Conference and Scientific Sessions
Release Date: 06.20.2008
Presentation Type: Abstracts
Hunt J.M. 1, Barker S.A. 2, Messenger J.C. 2, Groves B.M. 2, Lowes B.D. 2, Carol J.D. 2, Gruber M.P. 1, Bull T.M. 1
1. Department of Medicine, Division of Pulmonary and Critical Care Medicine, Pulmonary Hypertension Center
2. Division of Cardiology, University of Colorado Health Sciences Center, Denver, CO, USA
BACKGROUND: Significant improvements in the treatment of Pulmonary Arterial Hypertension (PAH) have occurred in the past two decades. Right heart catheterization (RHC) and assessment of acute vasoreactivity is recommended before selection of therapy. Inhaled nitric oxide (iNO) is frequently used for this purpose due to its short half life and safety profile. However, the exact details of iNO use in the assessment of vasoreactivity have not been standardized. We sought to determine the duration of time necessary to assess for the presence or absence of acute vasoreactivity using iNO.
METHODS: We performed a prospective cohort study of 52 patients referred with PAH for RHC between March of 2005 and February of 2006. RHC measurements were obtained at baseline and then repeated at 5 and 10 minute intervals after initiation of iNO (40 ppm + 0.5 FIO2) via facemask. The patients were assessed for acute vasoreactivity based on a modification of the ACCP 2004 guidelines .
RESULTS: 7 subjects (13%) met the criteria for acute vasoreactivity to iNO. Among these subjects there was no statistical difference between mean pulmonary artery pressure, cardiac output, or pulmonary vascular resistance as measured at 5 or 10 minutes after initiation of iNO. However, two of the 7 vasoreactive subjects did not meet criteria for a positive response until 10 minutes after initiation of iNO.
CONCLUSIONS: The onset of vasodilatation in the pulmonary vascular bed occurs quickly after initiation of iNO. The majority of patients respond by 5 minutes with no statistically significant change in hemodynamics between 5 and 10 minutes. This suggests vasoreactivity should be assessed initially 5 minutes after initiation of iNO. If the criteria for vasoreactivity are met at this time, the study can be discontinued. If the criteria are not met, the patient's hemodynamics should be reassessed at 10 minutes.