If chloral hydrate were to be given rectally would it decrease the incidence of nause since it avoids gastrointestinal irritation?

Discontinued. That medication has been discontinued. http://www.ashp.org/drugshortages/notavailable/bulletin.aspx?id=902.
No and... The nausea is caused by the centrl effect of the drug not direct gastric irritation. Rectal administration of drugs results in rapid absorption directly into the bloodstream and avoids initial metabolism from the liver (first pass effect) resulting in much higher and potentially toxic levels. Ch is no longer used.