1 Faculty of Medicine, University of British Columbia, Vancouver, B.C., Canada.
2 Department of Anesthesia, BC Women's Hospital, Vancouver, B.C., Canada; Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, B.C., Canada.
3 Department of Anesthesia, BC Women's Hospital, Vancouver, B.C., Canada; Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, B.C., Canada. Electronic address: smassey@cw.bc.ca.