1 Department of Anesthesiology, Neurology and Physical Medicine and Rehabilitation, Johns Hopkins School of Medicine, Baltimore, Maryland.
2 Department of Anesthesiology and Physical Medicine and Rehabilitation, Walter Reed National Military Medical Center, Uniformed Services University of the Health Sciences, Bethesda, Maryland.
3 Department of Anesthesiology and Perioperative Medicine, Mayo School of Medicine, Rochester, Minnesota.
4 Anesthesiology Service, Department of Surgery, Naval Medical Center-San Diego, San Diego, California, USA.