http://stackoverflow.com/questions/15653346/how-would-you-optimize-a-query-with-multiple-joins-and-redundant-criterias/15653584

gistfile1.sql

declare @max_mrdate datetime
declare @max_nexteval datetime

select
	@max_mrdate=max(cast(mrdate as datetime)),
	@max_nexteval=max(cast(nexteval as datetime))
from tblpms
where CaseNo = 'TR13-011-CRW'

select *
from tblpms where CaseNo = 'TR13-011-CRW'
and (
	(med_stat is not null and cast(mrdate as datetime) = @max_mrdate)
	or
	(mrprocedure is not null and cast(nexteval as datetime) = @max_nexteval)
)