Sacroiliac joint injections

Hi, I met with a chronic pain consultant, haven waited 8 months for my appointment. I’ve had severe right leg pain due to moderate to severe spinal stenosis. This has caused what physio calls neurogenic claudication, where as well as the nerve being compressed, its blood supply is also affected, causing severe cramping pains in the leg. It has eased, but the right leg, hip and buttock remain tender to touch, and painful sitting. She is going to do a sacroiliac joint injection as well as a hip bursa injection. She asked if I wanted local or sedation, I said local but now questioning myself. I’ve had the hip bursa done previously and have no worries with that.
One of my concerns is lying flat on my stomach for 20 minutes or so. It’s being done with X-ray. My other concern is I have severe adrenal insufficiency, and produce no cortisol, so if the procedure is very painful, my cortisol levels are likely to plummet, leaving me feeling very ill and at risk of a crisis. How have others found this procedure. Wondering whether to contact her and change to having the injection with sedation.