Obstacle avoidance between take-off and airway

Yesterday I tried to plan a flight from Big Bear City (California) to Santa
Monica, in a Bonanza. The routing I worked out was L35..DAWNA.V8.PDZ.V186
TIFNI.ELMOO.DARTS..KSMO. DAWNA is on a portion of the airway that shows a MEA
of 10500 on the chart. Since I was westbound, I figured to climb to 12000. I
planned to depart from runway 26. My calculations showed that the Bonanza
could carry out this climb.

My question is: How do I make sure that I don't hit anything between the
runway and the first fix on my filed route? The ODP for Big Bear only gives
details for runway 8, and says "N/A" for runway 26. The only departure
procedure is an obstacle departure, also for runway 8. So what's the proper
way for me to plan a flight so that I don't run into anything between the time
I leave runway 26 and the time I reach DAWNA? Should I use a VFR sectional?
Is there something on en-route IFR charts that I'm missing? Did I overlook
something in the Instrument Procedures Handbook (it seems surprisingly vague
on this)?