SQL Statement for if last boot is within last 10 minutes then insert the word in email "Power Loss"

Try the following as a SQL variable in your alert.

select case 
when lastboot is null
then 'No Last Boot Time Available'
when DATEDIFF(MINUTE,lastboot, getdate()) <= 10
then 'Possible Power Outage' 
when DATEDIFF(MINUTE,lastboot, getdate()) >= 10 
then 'No' 
end as 'MinutesSinceLastBoot'
from nodes

I'm testing this now and will let you know

The solution provided doesn't work.  The response I get simply says "No" each time.