Tuesday, July 8, 2008

The ProVent Prognostic Score: Helpful?

Palliative Care Nurse: "We got a new consult in the ICU. A 55 year old who has been on the vent for 4 weeks with platelets of 75, on levophed and hemodialysis."
Palliative Care Doctor: "Sounds pretty serious. I wonder how he is going to do?"

Have you ever faced this dilemma of prognostication? If so, there is a new prognostic test developed for just this situation. If you are asking yourself, "Where is the prognostic dilemma? I already have a pretty good idea of what is going to happen" then you can go to the head of the class.

A reader sent me a well-executed study demonstrating the development and validation of a prognostic scoring system. This NIH funded study from UNC, Duke, and ECU was completed over 4 years (3 for the development cohort of 200 patients and 1 for the validation cohort of 100 patients).

The researchers choose to study patients requiring prolonged mechanical ventilation (greater than 21 days), a population notable for a high mortality and symptom burden. The reason for the study was noble in trying to enable physicians to have an easy to use, highly specific prognostic score to encourage open discussions about prognosis with patients and surrogate decision makers. They cite two studies in the discussion for the severe lack of prognostic disclosure in critical care situations (12% and 40% (SUPPORT)). (Hint: get a palliative care consult)

They identify the four variables with the highest relative risk: Age older than 50y, vasopressors, platelets less than 150, and hemodialysis. Each is assigned one point to get your ProVent Score. (I give one point for cleverness on the name for the score!) A score of 3 or 4 indicates a roughly 95% one-year mortality risk and a 85% 3 month mortality risk. (Disclaimer:Read the study for more details before you take this information and apply it clinically.)

Do you find this score to be clinically relevant? Would you use it to inform your decisions/prognostic estimates? Would you quote it to the family or patient? How about discussing with other clinicians? Personally, I am not too sure it is clinically relevant. We rarely see patients on vents longer than 21d still in the hospital. They are often already at the long term acute care hospital. I plan to give it a try and see how it compares with my own clinical judgement and that of my peers.

The authors conclude:

"Simple clinical variables measured on day 21 of mechanical ventilation can identify patients at highest and lowest risk of death from prolonged ventialtion."
The best part about actually reading an article is you can come to completely different conclusions (beware quoting abstracts!). For me (and you if you have read this far) the take home points to this article are really hidden and have numerous implications:

for clinical care (to be further validated):
  • 40-50% of patients on prolonged mechanical ventilation (more than 21d) will die in the hospital (i.e. consider a palliative care consult trigger to discuss prognosis)
  • If you survive the hospital stay, your mortality is only 17% at one-year (Graph)
  • If you have a ProVent score of 2 or more you have minimal chances at being alive and independent in all ADL's at one year.
for future prognostic studies:
  • Obtain clinician estimates for survival as a measure to compare your calculated prognostic score. Otherwise you risk making a score that is no better than current practice (communicated or not).
  • Condeming all clinical estimates of survival based on a small handful of poorly designed studies does not qualify statements like "we know that prediction of mortality by clinicians using clinical probability of ICU survival is not accurate." We have too much to learn about the practice of clinical prognostication to come to this conclusion.
  • Inclusion of the prognostic score is vital as a core part of the research to be examined and discussed amongst peers.
  • Clinically relevant prognostic time frames are important and are very situation dependent. Discussing the chance that someone may have a 90% chance of dying within 1 year or even 3 months is not typically being discussed in ICU palliative care family meetings. The range may be hours, days or maybe a couple of weeks.
and for ICU studies of mortality:
  • Include palliative care consultation and decisions to withdraw or withhold key life support measures as baseline demographic or outcome variables. These two issues could have major repercussions on validity of data sets concerning mortality.
  • Consider using the ProVent score to stratify different risk groups in this select patient population.
(HT: B. Arnold)
ResearchBlogging.orgCarson, S.S., Garrett, J., Hanson, L.C., Lanier, J., Govert, J., Brake, M.C., Landucci, D.L., Cox, C.E., Timothy, S.C. (2008). A prognostic model for one-year mortality in patients requiring
prolonged mechanical ventilation.
Critical Care Medicine, 36
(7), 2061-2069. DOI: 10.1097/CCM.0b013e31817b8925

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