Prognosis Scenario

You admit a 68 year old male to the ICU who suffered a cardiac arrest while at home. He was successfully resuscitated by emergency medical personnel but had approximately 30 minutes of cardiopulmonary resuscitation. He is intubated and unresponsive to verbal stimulation. He is now 3 days post arrest and has no motor response to pain. The family wants to discuss limiting care if you think he is unlikely to recover. You decide to look for evidence to help advise the family and form the question, ‘in patients with no motor response 3 days following a hypoxic coma after a cardiac arrest, what is the chance of good neurological recovery?’

You search MEDLINE using the terms ‘anoxic’ and ‘coma’ and find an article
Lancet 1994;343:1055-59.

Read the article and decide:

  • Is the evidence about prognosis valid?
  • Is the valid evidence about prognosis important?
  • Can you apply this valid and important evidence about prognosis in caring for your patients?

Completed Prognosis Worksheet for Critical Care Medicine

Citation

Edgren E, Hedstrand U, Sutton-Tyrell K, Safar P, and BRCTI study group.
Assessment of neurological prognosis in comatose survivors of cardiac arrest.
Lancet 1994;343:1055-59.

Are the results of this prognosis study valid?

Was a defined, representative sample of patients assembled at a common (usually early) point in the course of their disease?
Yes.
Was patient follow-up sufficiently long and complete?
Yes. 12 months
Were objective outcome criteria applied in a “blind” fashion?
Objective outcome criteria applied (Cerebral performance categories) but did not state if blinded.
Patients were part of a clinical trial but unclear if people were blind to neuro exam results.
If subgroups with different prognoses are identified, was there adjustment for important prognostic factors?
Groups did not appear to be different.
Was there validation in an independent group (“test-set”) of patients?
No.

Are the valid results of this randomised trial important?

How likely are the outcomes over time?
0 % (0 out of 43) of patients without motor response on day 3 recovered.
How precise are the prognostic estimates?
95% CI: -2% to 2%

If you want to calculate a Confidence Interval around the measure of Prognosis

Clinical Measure Standard Error (SE) Typical calculation of CI
$$text{Proportion (as in the rate of some prognostic event, etc) where:}$$

$$text{the number of patients} = n$$

$$text{the proportion of these patients $\\$who experience the event = $p$}$$

$$ sqrt{frac{ptimes(1-p)}{n}}$$
$$text{where $p$ is proportion and $n$ is number of patients}$$ 		$$text{If $p$ = 24/60 = 0.4 (or 40%) and $n$=60}$$
$$sqrt{frac{0.4times(1-0.4)}{60}}$$
$$= 0.063 (text{ or } 6.3%)$$

$$text{95% $CI$ is 40% $pm$ 1.96 $times\\$ 6.3% $times$ or 27.6% to 52.4%}$$

$$text{$n$ from your evidence: }underline{quad69qquad}\\$$
$$text{$p$ from your evidence: }underline{quad0qquad}$$ 		$$sqrt{frac{ptimes(1-p)}{n}}$$
$$text{where $p$ is proportion and $n$ is number of patients}$$ 		$$text{Your calculation:}
text{SE} =
sqrt{0.005times(1-frac{0.005}{43})}$$
$$= 0.005(0.1%)_________.$$

$$text{95% $CI$: 0% $pm$1.96 $times$ 0.0012 = -2% to 2%}$$

Can you apply this valid, important evidence about prognosis in caring for your patient?

Were the study patients similar to your own?
Yes
Will this evidence make a clinically important impact on your conclusions about what to offer or tell your patient?
Yes

Additional Notes

This paper evaluated the prognostic ability of several other physical exam findings however, we focused only on motor response.

Anoxic Brain Injury: Estimating Recovery

Clinical Bottom Line

Pt who have no motor response 3 days after hypoxic stroke following cardiac arrest have 0% chance of good neurologic outcome at 1 year.

Citation

Edgren E, Hedstrand U, Sutton-Tyrell K, Safar P, and BRCTI study group.
Assessment of neurological prognosis in comatose survivors of cardiac arrest.
Lancet 1994;343:1055-59.

Clinical Question

In patients without motor response three days after hypoxic stroke, what is the probability of a good neurologic recovery (cerebral performance category[CPC] 1 or 2).

The Study

The authors studies 262 patients with hypoxic coma following cardiac arrest and the cohort was drawn from a multicenter clinical trial of thiopentone (Brain Resuscitation Clinical Trials Group). Patients were examined daily and followed for one year. The primary outcome was good neurologic recovery at one year. Forty-three patients had no motor response on day 3.

The Evidence

$$Prognostic factor$$ $$Outcome$$1 $$Time$$ $$Measure$$ $$95% CI$$2
$$text{No motor response}$$ $$text{CPC 1 or 2}$$ $$text{Day 3}$$ $$0% (0/43)$$ $$-2% text{to} 2%$$
$$text{No pupil light response}$$ $$text{CPC 1 or 2}$$ $$text{Day 1}$$ $$18% (16/89)$$ $$10% – 26%$$
$$text{No pupil light response}$$ $$text{No pupil light response}$$ $$text{Day 3}$$ $$0% (0/18)$$ $$-3% text{to} 3%$$

Comments

  • Study suggests that absence of motor response on day 3 is the best predictor of poor outcome. However, absence of pupil light response also helps in predicting poor outcome.
  • They had a well defined cohort with adequate follow up however it is unclear if person evaluating the outcome was blinded to neuro exam.
  • They did not evaluate the model in an independent test set of patients.

References

  1. good neurologic outcome defined as cerebral performance categories (CPC) 1 or 2. 
  2. 0.005 used as the event rate to calculate the 95% CI