Doctors' estimates of the feasibility of preserving the dying for future revival

That's a way higher number than I expected.

I worry that there's a selection bias: physicians who even bothered to respond to a survey on this topic.

I agree, and I am a US physician! Curiously, their paper was sponsored by an entity that funds cryopreservation research. The paper asserts that those surveyed were general practitioners, but the actual survey itself had quotas for various subspecialties. The survey also has an introduction section that frames cryopreservation (not used in medicine) in the context of hypothermic protocols (commonly used in medicine), which would seem to lend it some legitimacy. But that isn't a fair comparison. Only critical care specialists and some surgeons and anesthesiologists have much experience with therapeutic hypothermia. GPs would typically have less experience and might not readily notice the inequivalence.

I can't help but wonder whether they changed the protocol after the survey was designed and only interviewed general practitioners. Or, worse, perhaps they selectively excluded a portion of the interviewed population.

First author here to provide context:

1. We had both general practitioners and various specialists. We set a minimum quota for each so that we'd get some sense of what all the various groups thought. We aimed for and obtained 180 specialists along with the 150 general practitioners. See figure 1 c.

1a. We absolutely did not change the protocol after the survey was designed, or selectively exclude sections of the population. The inclusion/exclusion criteria are as per the methods, and this was a one-shot survey (no piloting beyond initial validation on colleagues). I'm all for open and reproducible science!

2. The introduction does not claim an equivalence between induced hypothermia and preservation, just that induced hypothermia does provide some precedence that preservation may work.

"Some surgical operations, such as repairs of aneurysms of the aortic arch, are performed using deep hypothermic circulatory arrest (Connoly et al., 2010). In this procedure, a patient’s body is cooled to ~20°C, experiencing both circulatory arrest and complete electrocerebral silence on EEG. Patients can survive 30+ minutes in this state with >90% survival rates and intact post-surgical cognition (Percy et al., 2009).

This demonstrates that long-term memory and personality can persist through prolonged cessation of brain activity - a finding which builds upon other neuroscience data showing that these depend on structural properties such as neuronal connectivity, rather than requiring uninterruptible electrochemical dynamics (Stecker et al., 2001).

Some terminally ill patients, based on this medical evidence and their personal beliefs about future medical advances, have requested procedures to preserve their brain structure after legal death..."

3. I was also surprised the probability estimates were as high as they were! I think doctors just think this has a greater chance of working than is commonly perceived.

These were physicians who were being paid to complete surveys - no reason to think they were more likely to select/reject this one over any of the others available to them at the time.

<puzzled frown>. There's at least one reason. It's in the comment you responded to.

> though the speculative nature of the estimates warrants consideration.

Experts in a related field were asked to guess how successful something no one has ever done would be, if it could be done.

That's like asking a bunch of certified mechanics how fast George Jetson's flying car could go. I mean, there are mechanics in The Jetson's universe, so... same knowledge base, right?

Two: the phrase "being paid".

Thanks for the excellent response and clarification! I apologize for misreading your method with regard to inclusion of subspecialties. Figure 1 is particularly enlightening. Indeed, I'm in one of the two most skeptical subspecialties, and I considered switching to the other for some time. I suppose that says something about my biases as does the fact that I lurk on HN.

Apologies, that was my mistake. The subspecialties I thought weren't included were reported in detail in one of the figures, and they were some of the more optimistic groups. The result is surprising to me.