4.12.2010

The Killing Spree that Wasn't

A Dutch nurse given life for murdering seven people in a killing spree that never happened will hear about her appeal on Wednesday.

Moral of the story: Don't multiply your p-values.

The statistical analysis is a rather interesting read, even though the math's a little over my head. Basically, a Dutch nurse got convicted for killing patients just because a lot of deaths happened while they were working. From the paper:

4 Appendix: extended discussion of hetero-
geneity
4.1 Preliminary remarks
The null-hypothesis tested by the court statistician H. El ers in the case of Lucia de
Berk is supposed to mean that incidents on a ward, and shifts of a particular nurse,
are independent of one another. In the minds of lawyers or medical specialists, as in
that of the man in the street, independence means: lack of causality. Causality can
be \measured" by performing the thought experiment: suppose that Lucia worked
on a particular shift, and that an incident occurred: would the same incident have
happened if Lucia had been magically exchanged for another nurse? The idea in
this thought experiment is that \everything else that might be relevant is kept
the same", so that we compare strictly comparable situations: with and without
Lucia, everything else being unaltered. In a randomized double-blind clinical trial
we do keep everything relevant the same, by randomization. In observational
studies we are unable to do this, so instead we are forced to take explicit account
of anything which could be relevant, in one way or another, if we want to conclude
causality. This requires prior knowledge concerning the mechanisms underlying
the phenomenon under study.
4.2 Are nurses interchangeable?
According to many medical specialists we have spoken to, nurses are indeed com-
pletely interchangeable with respect to the occurrence of medical emergencies
among their patients: nurses merely carry out the instructions given to them
by the medical sta , and they do this according to standard practices of proper
care, so it can make no di erence at all to replace one nurse by another. However
according to nursing sta we have consulted, this is not the case at all. Di erent
nurses have di erent styles and di erent personalities, and this can and does have
a medical impact on the state of their patients. Especially regarding care of the
dying, it is folk knowledge that terminally ill persons tend to die preferentially
on the shifts of those nurses with whom they feel more comfortable. (This might
apply to the Red Cross Hospital, where Lucia worked on two adjacent wards for
terminally ill aged patients). As far as we know there has been no statistical
research on this phenomenon.
4.3 De nition of incidents
There is another respect in which nurses can have an impact on \incidents". In
the Lucia case, incidents were never formally de ned. However, if medical doctors
were expressly called to the bed of the patient by nursing staff , then that soon
quali ed as an incident, especially if Lucia was somehow involved. Who decides if
the doctors should be alerted? The nurses on duty, themselves, of course. It seems
that several of Lucia's incidents were created by herself in situations where she was
uneasy about the patient who appeared to be developing some new and, to her,
alarming symptoms. The nurse who keeps a closer eye on her patients, and who is
less prepared to take risks, will generate in this way incidents on her shift, which
otherwise might be postponed to the next shift or even fail to materialise at all.
According to medical specialists, nurses do not have a choice in such situations:
they have been trained to make the right decision and every nurse in the same
situation will make the same decision. According to nurses however, this is just
not true. Nurses do have to make their own decisions and though they should
always be able to justify their choices, this does not mean that every individual
will make the same choice in the same circumstances.


Wow, statistics is some heavy stuff, huh? Almost makes me excited to study it again in grad school (almost).

Even the Dutch state prosecution now accepts Lucia should be acquitted and there was no evidence of any unnatural deaths, though her convictions for stealing two books from the hospital library – a charge she denies – will be upheld. Now living with her partner while awaiting judgment, Lucia is penniless, denied benefits, and paralysed down one side following a stroke she had in 2006 in the week she was told her conviction would be upheld.


All because of a math error.

You might remember the Cat who predicted deaths in an RI nursing home. I haven't heard anyone seriously suggest the cat was killing the patients.


Work last week was full of action and excitement! It was one of the busiest weeks I'd seen in a while, and I was filling in for the day-shift supervisor. It was the kind of challenge I enjoy, lots of things to do and keep track of. Around 30 elders to keep track of, with two hip-height racks of charts to manage. MD appointments, changes in condition, changes in skin, changes in wounds, sudden changes of vertical status (if we're unlucky), charts to audit, phone-tag with various MDs, labs pouring off the fax machine, face-time with family members, staff issues to work out..there's no time to be bored! Thankfully the staff I work with are all great. Those of us that are left have been through a lot with each-other and I always look forward to seeing them, even the ones I don't always agree with.

Even better, the student nurses were there for two days out of the week. Having them around has been lots of fun and has given me plenty of opportunities to reflect on my own practice as a Nurse. It's also loads of fun having extra people around to help me look stuff up and collect samples, as well as ambulating and transferring people. The sheer logistics involved in moving what seems like a small number of bodies around can get pretty intense.

I had so much fun last week that the prospect of taking this next week off is daunting. I probably should have planned a trip or something, but I couldn't think of anywhere to go.

In my idleness I've been pondering my options for grad-school. The more I work in an environment without electronic charting the more interested I am in Nursing Informatics, especially considering the extremely small number of RNs who currently hold that degree. I've been prototyping in my head what I would want an electronic charting tool for a nursing home to look like, tablet PCs with icon interfaces to add I/Os, vitals and med administration, different views for CNAs, Floor nurses and nursing supervisors, integrated inventory management, etc. I think I may save that for post-grad, though, I'm more interested in bedside nursing at the moment.

I'm browsing through the list of masters degrees in nursing offered at University of Phoenix. Strangely enough they've reversed which courses appear on the Masters of Health Care Administration and Masters of Science in Nursing pages, but I figured it out after clicking around a little bit. The graduate degree I was looking for wasn't in the list (Clinical Nurse Leadership), but Nursing Informatics is. Also, staggeringly, a dual MSN/MBA program. The also have Family Nurse Practitioner up there, but I'm not sure I like the idea of working in a doctor's office. The fluorescent lighting gets to me. Anyway, I sent off a request for some info, We'll see where it leads.

It would be nice to take classes with names like "creating change in institutions" and "Management of pediatric and adolescent populations" for a change.

1 comment:

Little Heck said...

Statistics is a game. I'm interested in studying it from a nursing perspective. Sad to hear about this nurse and the details behind her charges over the past couple of years you have talked about this case.