[1] Geisinger Med Ctr, Div Anesthesiol, Danville, PA 17821 USA
[2] Harvard Univ, Massachusetts Gen Hosp, Dept Anesthesia & Crit Care, Sch Med, Boston, MA 02114 USA
[3] Harvard Univ, Massachusetts Gen Hosp, Sch Med, Div Thorac Surg, Boston, MA 02114 USA
[4] VA Boston Healthcare Syst, Anesthesia & Crit Care Serv, Boston, MA 02132 USA