[al from Canada]

http://www.sciencedirect.com/science...ba97af9aa3e8ab

http://www.ncbi.nlm.nih.gov/entrez/q...&dopt=Abstract

http://www.anesthesia-analgesia.org/...ract/90/6/1411

http://freud.tau.ac.il/~shamgar/pdf_files/52.pdf

This is a lot of reading but, winter nights are long; especially in this God forsaken, snowed-in part of the planet we call the great white north.
Al