10. Hypothermia

Question 1

Initial Management of ROSC in an OOHCA VF arrest

Answer 1

1. Adequacy of CVS?
2. Trigger for original rhythm
3. Grade degree organ systems damaged during arrest
4. Obtain
   - HR Rhythm / 12 lead
   - BP
   - O2 Sat
   - Temp
   - ABG
   - CXR
   - BGL
   - FBC / U+E / Trop / Clotting / X match

Question 2

Ongoing initial mx

Answer 2

Collateral Hx / GP notes / Patients notes
Paramedics

Precipitating factors ?further Invx / Mx
Angio / PCI / IABP

T/Fer t ICU
Further Invx / Support / monitor/ stabilisation

Cardiology r/f
Echo / further Mx

Question 3

Elective Hypothermia TTM

Answer 3

There have been several randomised trials investigating temperature management following cardiac arrest

The HACA trial (n=137) and Bernard trials (n=77) published in NEJM in 2002 reported that therapeutic hypothermia following a VF arrest improved favourable neurological outcome.

However, small sample sizes and other methodological flaws meant the evidence was of low certainty. A number of patients in the control group developed fever and it was therefore unclear if the reported benefits were from hypothermia or the avoidance of fever

The TTM (2013) study (n=950) compared a targeted temperature of 33°C vs. 36°C in patients with an out-of-hospital cardiac arrest from a presumed cardiac cause. They reported no significant difference in all-cause mortality

The HYPERION trial (n=584) showed that in patients with coma following a non-shockable cardiac arrest, the use of moderate hypothermia improved favourable neurological outcome at 90 days compared with targeted normothermia

The European Resuscitation Council released new guidelines in March 2021. These suggest:
maintaining a target temperature at a constant value between 32 and 36°C for at least 24 h
avoidance of fever (> 37.7°C) for at least 72 h after ROSC in patients who remain in coma

Fever is associated with worse outcomes

Question 4

TTM 2

Answer 4

Intervention
Hypothermia group: target temperature 33C
Rapid cooling achieved by cold fluids and physical cooling devices (surface or intravascular devices).

A feedback-controlled system used to maintain target temperature (bladder temperature probe)
Rewarming began after 28 hours (increase temperature by no more than 0.3°C per hour until 40 hours)
95% of patients received cooling

70% cooled with external devices and 30% with intravascular devices

Question 5

TTM2 Control group

Answer 5

Control
Normothermia group: In participants who developed a temperature of 37.8°C (trigger), a device was used and set at 37.5°C
Pharmacological and conservative therapies initiated first
Physical cooling devices (surface or intravascular) used if temperature ≥ 37.8°C
Physical cooling devices could be placed prophylactically, but no active cooling was provided for patients who had a spontaneous temperature of <37.8C
A feedback-controlled system used to maintain target temperature
46% of patients needed a device to achieve target temperature (of these 69% used surface cooling, and 31% used intravascular cooling)
In 1st 24 hours ~5% of temperatures recorded at >38C

Question 6

TTM2 Conclusions

Answer 6

In patients suffering out-of-hospital cardiac arrest, induced hypothermia did not lead to lower mortality
Functional outcome and health related quality of life did not improve from hypothermia

I will aim for normothermia in my patients following out of hospital cardiac arrest. I will implement targeted temperature management if temperature exceeds 37.7°C
Future exploration may include a trial of normothermia vs no targeted temperature management