1. From the Department of Intensive Care Medicine, Northwick Park and St. Mark's Hospital (G.S., M.R.P., S.W., A.C.-C., M.D.B.); the Department of Intensive Care Medicine, Hammersmith Hospital (S.J.B.); and the Department of Haematology, Imperial College London, Northwick Park and St. Mark's Campus (N.P.) — all in London.