A global run on the U.S. dollar triggered by the coronavirus pandemic is once again prompting the Federal Reserve to step in as the lender of last resort for investors and companies scrambling for dollars. The Fed enhanced the existing dollar-liquidity swaps it offers foreign central banks and established new ones as part of sweeping emergency measures unleashed to ease a shortage of greenbacks. The idea is to help companies seeking to either raise cash or repay loans and alleviate pressure on c