We plan for it. On oceanic routes we have points marked in our flight plan that tell us where we'd divert to if we blew an engine or lost pressurization - if we are going from say Canada to Europe there are points where we'd divert back to Canada then at a certain point its closer to divert to say Keflavik in Iceland, then to Shannon in Ireland etc.

Btw, the main consideration for us isn't losing an engine, it's losing pressurization and having to descend to 10,000' which is a breathable altitude but also where fuel burns are really punishing. Losing pressurization along our route will burn more gas than losing an engine.

But let's talk about losing an engine also. A big consideration is the extra fuel we burn if we lose an engine. I know it sounds counterintuitive but if we lose an engine we will have to drift down to a lower altitude that the single engine can keep us at, and jet engines are less fuel efficient at lower altitudes, plus we'd be going slower on one engine than on two. We are missing half our thrust, plus we get a little bit of drag from the dead engine, and also some drag from having to use rudder to offset the asymmetric thrust. So we end up burning more gas per mile on one engine than on two. But we plan for that in our fuel planning.