Keep 'em cool!

A new feature of VicCritCare is the assessment of some of the biggest papers in the critical care world - past and present.  This week's guest reviewer is Dr James Malycha.

James is an Intensive Care Registrar from Melbourne, Australia.  He has a love of obscure humour.

Treatment of comatose survivors of out of hospital cardiac arrest

Stephen A. Bernard N Engl J Med, Vol. 346, No. 8 · February 21, 2002

Summary

A well designed randomised, not blinded study showing clear improvement in neurological outcomes in patients who have out of hospital VF arrests who are promptly cooled (within 2 hours) to 33 degrees and treated in well resourced tertiary hospital, although no improvement in mortality found.

Background

Poor outcomes for OOHCA

5-35% survival

Survivors have poor outcomes due to anoxic brain injury

Study question: Does cooling help, as suggested by animal studies?

Hypothesis: Cerebral ischaemia may persist for hours post-resus. Hypothermia may help reduce damage caused by this phenomenon.

Existing data: Only other human trials  are retrospective and uncontrolled.

Methods

Design

Inclusion – VF, ROC at scene, 4 ED’s

Exclusion - < 18yo male, < 50yo female, SBP < 90 despite resus, causes other than cardiac, ROSC had to occur at scene

Primary outcome – survival to hospital discharge good enough to go home or rehab

Secondary outcome – heamodynamic, biochemical and heamotological effects of hypothermia

77 patients in total – 43 hypo, 34 normothermic

Controlled for Pa02, K, creatinine, CK, MAP.

Protocol 

Both groups given antiarrythmic (lignocaine bolus then infusion)

PACatheter. Some not (roughly 20% in each group)

Sedated and paralysed (all in hypo, as needed in normo) – midaz and vec.

Outcome 

In ICU – withdrawal, trachy or extubated depending on progress

On wards -Rehab physician assessed needs on discharge from hositpal. Blinded to initial treatment.

Stats

Well powered. Achieved significance.

Aimed to achieve 15 – 50% improvement in primary outcome b/w groups.

Results

84 pt over 33 months

Characteristics of groups similar

More men in normothermic group?? 79 vs 58 %

No difference in mortality

Difference in ‘positive outcome’ 

23% improvement in normal or minimal disability group – stat significant

Also shown with odds ratios. Both p values 0.046

Weaknesses

No women < 50yo.

More men in normothermic group.

Not blinded at scene or in ED/ICU (?impossible).

Randomisation using odd/even days is not ideal.

Application to ICU

Strong applicability to out of hospital cardiac arrest who gain ROSC in the field and are promptly cooled by emergency care givers.