A consortium of investors is poised to acquire HCA in what is believed to be largest ever private equity transaction. Bain Capital, Merrill Lynch, Kolberg, Kravis Roberts (KKR) and members of HCA’s founding Frist family have agreed to pay $33bn (£17.5bn), including the assumption of $11.7bn (£6.2bn) debt, for the US’s largest hospital operator. The…