Does the Principle of Double Effect Apply to End of Life Pain Management?

The principal of double effect applies to a situation like that sure. If you are talking about increasing the amount of let's say an opioid pain killer of some sort which would potentially be foreseen to pace and death in some way. The question is do you have a sufficient reason here to go ahead and increase that dose in the circumstances? In most situations the answer is no you don't have better alternatives available to you in these in these circumstances so yes you have a proportionate reason for doing this.