Without patents, you would just get people signing even longer term exclusive contracts. The whole point of the patent system is that it's less bad than the previous situation, where either inventors were ripped off wholesale or they forced buyers into perpetually exclusive agreements.

Hospitals have no choice but to bend to BD's will.

Well, they could pay more in the short term and hope for innovation to undermine the monopoly over the long term, by buying cheaper and more effective products from disruptive competitors.