[1] Inst Nacl Cancerol, Dept Crit Care Med, Ave San Fernando 22,Col Secc 16, Mexico City 14080, DF, Mexico
[2] Mexican Inst Social Secur, Hosp Especialidades, Dept Crit Care Med, Ctr Med Nacl Raza, Mexico City, DF, Mexico
[3] Mexican Inst Social Secur, Dr Carlos McGregor Sanchez Reg Gen Hosp 1, Clin Epidemiol Res Unit, Mexico City, DF, Mexico
[4] Univ Nacl Autonoma Mexico, Fac High Studies FES Zaragoza, Mexico City, DF, Mexico
[5] Fdn Clin Med Sur, Dept Crit Care Med, Mexico City, DF, Mexico