parameters

find=PCI | find1=STEMI | find2=... : search news titles + summaries (note: db intensive, please limit numarticles)
title=PCI | title1=STEMI | title2=... : search news titles only (*much* less db intensive)
cat=January 2009 : list articles from Jan 2009
year=#### : list articles published in year ####, starting with most recent (use 4 digits)
prevmon=# : list articles published so many months ago, as displayed on Category:Published
prevyear=# : list articles published so many years ago, as displayed on Category:Published

NOTE: time limiters & searches can be combined -- this is a good way to limit results. EX, you could say

{{searchnews2|prevmon=0|title=PCI}}  <-- search within the last month's news

numarticles=# : number of articles to display (for title searching, it will be this number. For text searching, search is conducted within this number of most recent articles.
cacheresults (true or false, defaults to true) : whether it's OK to use data up to an hour old

Examples

{{searchnews2|prevmon=0|title=PCI}}  <-- search titles within the last month's news

{{searchnews2|prevmon=0|find=PCI|find1=STEMI|find2=stent}}  <-- search text within the last month's news

As noted elsewhere, search terms for 'find' params are case insensitive. Titles are not. See Template:Searchnews for more info on this.
This is slightly modified from Template:Searchnews which limits display articles to 5, irrespective of the articlenum param. Searchnews also doesn't give the option of searching by year and/or title.
As in Searchnews & Listnews, the control of the display is dictated by Template:Newsarticle.dplsearch