[1] VA TN Valley Healthcare Syst, Anesthesia Serv, Nashville, TN 37212 USA
[2] Vanderbilt Univ, Med Ctr, Dept Anesthesiol, Div Crit Care, Nashville, TN 37212 USA
[3] Vanderbilt Univ, Sch Med, Div Allergy Pulm & Crit Care Med, Dept Med, Nashville, TN 37212 USA
[4] Vanderbilt Univ, Sch Med, Ctr Hlth Serv Res, Dept Med, Nashville, TN 37212 USA
[5] Tennessee Valley Healthcare Syst, Geriatr Res Educ & Clin Ctr GRECC Serv, Dept Vet Affairs Med Ctr, Nashville, TN USA