What is the appropriate standard of care for a plaintiff in a medical malpractice case?

The trial judge identified the appropriate standard of care as set out in Ryan v. Victoria (City), 1999 CanLII 706 (SCC), [1999] 1 S.C.R. 201 at para. 28: Conduct is negligent if it creates an objectively unreasonable risk of harm. To avoid liability, a person must exercise the standard of care that would be expected of an ordinary, reasonable and prudent person in the same circumstances. The measure of what is reasonable depends on the facts of each case, including the likelihood of a known or foreseeable harm, the gravity of that harm, and the burden or cost which would be incurred to prevent the injury. In addition, one may look to external indicators of reasonable conduct, such as custom, industry practice, and statutory or regulatory standards.