Risk prediction models for major surgery: composing a new tune

Abstract

In this paper I explain why I think that most of the models that predict postoperative mortality should not be used when we're talking to patients about postoperative survival. Available models are isolated in time (from survival in the present) and space (from survival outside hospital). We know a lot about survival outside hospitals, with sufficient detail that we can discriminate between a man born in 1975 vs. 1976, or a woman aged 64 years vs. 65 years. We can use survival outside hospitals to inform what we do in hospital. I use my own survival to contrast with the survival of people older or younger than me. I will use my survival to illustrate how I might expect my mortality hazard to temporarily change when I have a scheduled operation (total hip replacement) and when I'm unwell and have an operation (for a fractured femoral neck). People live longer and longer and we operate on people older and older. We are also intervening earlier in progressive diseases, knowing that people are living long enough to experience harm from their progression. There is an evolving conflict between operating on older people and operating on younger people. Who has most to gain from the operation and who has most to gain from peri-operative critical care? Do we prioritise on reducing death now, in patients with relatively short life expectancies, or do we invest in the long-term survival of patients with relatively low rates of dying now? This conundrum is not informed by current risk models, with their focus on one to three postoperative months: we need to know survival outside hospital to gauge the value of what we do in hospital.

Keywords: major surgery; models; risk prediction.