This is going to sound stupid, but the real advice is that if you don't have the money to pay your ER bill just don't pay it. The hospital can and will wait, offer you a lower bill, send it to collections where you can negotiate lower than that.

Don't take on debt to pay debt.

I have no illusions that this debt will be paid (I have perpetually uninsured friends - one even says he just gives a fake name at the ER), but the debt is incurred anyway.