Mortality metrics can discourage doctors from treating complex cases.
As Michael Howell reminded me, the real challenges are in finding the metrics that matter and preventing unintended consequences with any given metric. Take a simple metric on mortality for surgery: patients should not die during surgery. But what if the patient’s situation was complex to start with? There are cases where a patient did not receive care and died because giving him appropriate care could have resulted in a worse quality score for the doctor.
— Healthcare And Data - How To Measure Quality · Forbes