Since the Russians are essentially occupying eastern Ukraine, and are attacking Kyiv from the north, east and south, maybe NATO military forces with US support should move into western Ukraine to prevent Russia from completely overrunning Ukraine. Air cover would have to be provided for the ground forces.
This would allow Ukrainian civilians to remain in Ukraine, and it could provide an alternate Ukrainian government seat of power if Kyiv is taken by the Russians. The presence of NATO and US military forces in western Ukraine would also provide leverage to get the Russians out of eastern Ukraine since NATO and the US could agree to pull its forces out of western Ukraine as part of a negotiated settlement.
Moving military forces into western Ukraine runs the risk of war with Russia, but the alternative of trying to get Russia out of Ukraine with sanctions and diplomacy might not be viable.
Additionally, it would put Russia on notice that it faces robust military action by NATO if it tries any expansionist moves in the future.