Delaney shares insights into the mysterious world of statistics and trials. This 12 minute podcast is particularly useful for Registrars preparing for their exams and was recorded at BCC4. For similar podcasts and audio; head to www.intensivecarenetwork.com and to rego for BCC5 in Cairns, check out www.bedsidecriticalcare.com
4. Mortality or survival?
Mortality:
Number of deaths/number at risk at the end of a
period of time
28 day mortality
Rate
Survival:
Time to event analysis
How long it takes for the event to happen
If you have survived for x time, what are your chances
of dying in x+1 time
Hazard
5. Population:
>18 yo
Source of infection
Temperature >38.3oC or <35.6oC
Heart rate > 90bpm
SBP <90 mmHg for 1 hour if adequate fluids and some pressors
Urine output <0.5 ml/kg/hr for > 1 hr or PaO2/FiO2 <280
Lactate >2 mmol/L
Ventilated
Excluded:
pregnant, contra/indication to steroids, advanced cancer, AMI, PE,
AIDS,
7. Outcome:
The primary endpoint was the 28-day survival
distribution from randomisation in non-
responders to the short corticotropin test
8. Point one
Post-randomisation sub groups are dubious
9. Is the subgroup variable a characteristic
measured at baseline or after
randomisation?
“The credibility of subgroup hypotheses based on
post-randomisation characteristics is severely
compromised, and can be rejected simply on this
criterion”
10. Subdivision of patients in ISIS-2 with
respect to birth signs
Gemini and Libra shows an adverse effect on
mortality
11.
12. Results:
300 participants
In non-responders
Placebo 73/115 (63%)
Steroids 60/114 (53%)
Hazard ratio 0.67 95% CI 0.47-0.95; P=0.02
Conclusion:
Treatment with hydrocortisone and fludrocortisone
significantly reduced the risk of death in patients
with septic shock and adrenal insufficiency
14. In nonresponders, the median time to
death was 12 days in the placebo and
24 days in the corticosteroid groups;
in responders, 14 days in the placebo
and 16.5 days in the corticosteroid
groups;
and in all patients, 13 days in the
placebo and 19.5 in the corticosteroid
groups.
19. How big a difference in mortality do you
think putting a tracheostomy in at Day 4
compared to Day 10 would make on 30 day
mortality?
50% RRR (15% ARR)
25% RRR (7.5% ARR)
10% RRR (3% ARR)
5% RRR (1.5% ARR)
21. Population:
Mechanically ventilated adults
Had been ventilated for 4 days and thought to
require at least 7 more days of ventilation
Excluded:
Those requiring a tracheostomy, contraindication to
tracheostomy, respiratory failure due to chronic
neurological disease
22. Intervention:
Trachesotomy by Day 4
Comparison:
Tracheostomy after Day 10 if still required
Outcome:
All cause mortality 30 days from randomisation
23. Sample Size Calculation:
Baseline mortality of 30%
Absolute risk reduction 6.3% (21% RRR)
Power 80%
Alpha 5%
4% loss to follow up
N=1692
24. Due to study fatigue and exhaustion of
funding
N=899
25.
26. “Tracheostomy within 4 days of critical
care admission was not associated with
an improvement in 30 day mortality”
27. We are 95% certain that early
tracheostomy might be between
5.4% worse to 6.7% better in absolute risk
About 20% better or worse in terms of relative
risk
28. 6.3% of patients had a complication of
tracheostomy
53% of patients who were randomised to
delayed trache didn’t need one
2 year mortality was 52.3%
Only 5 lost to follow up
29. Conclusions:
Unable to rule out a clinically important difference
between early and late trache
It probably doesn’t make a big difference to
mortality
Unknown about patient perspective
Useful information about the patient cohort
Not really a “negative trial”