The hospital has breached its duty to keep your health information private.
If subpoenaed it should only provide the specific records covered by the subpoena, that is, it should limit access to only what is necessary.
State Government & the Information Privacy Principles Instruction
State Government agencies ensure the protection of personal information by adhering to the Information Privacy Principles Instruction (IPPI), published as Premier and Cabinet Circular No. 12.
The IPPI regulates the way State Government agencies can collect, use, store and disclose personal information. The IPPI is administered by the Privacy Committee of South Australia.
The principal officer, or Chief Executive, of each State Government agency is required to ensure the IPPI is implemented, maintained and observed in respect to the personal information the agency collects or holds.
Here is a link to make your privacy complaint: