We recently had an email discussion among the attendings at one of my sites in regards to TTM goals. Here was my overall thoughts on the current situation:
General post arrest care thoughts:
- I think any focus on mortality with TTM is misplaced. The goal with post arrest care should be improved outcome (modified Rankin score/neurologically intact discharge) instead of improved mortality. I don't necessarily think we do anyone any favors with trach/peg/LTAC outcomes. However when it comes to studies, mortality is an easy button outcome.
- It's often impossible to guess outcomes early on. In my brief experience, too many people want to throw in the towel on post arrest patients too early. I've seen "extended downtime" (how much should we trust downtime reports that have gone through multiple people) have good outcomes and extremely brief arrests have poor outcomes. Of course pre-arrest status matters and most patients will do poorly, but I think it's worth the effort to try to salvage the rare salvageable patient.
- Expanding on the above, official AHA/ECC recommendation is no prognosis for 72 hours after arrest or 72 hours after the completion of a 33 degree C TTM run (class of evidence 2a benefit >>risk, LOE 2-NR (moderate quality, non-randomized).
- AHA/ECC also recommends against using myoclonic jerks for prognostication (class of evidence 3: risks >benefit, LOE 2-NR) (I'm definitely guilty of this).
- So the question becomes "Who is salvageable, and when do we know that they're salvageable?" Given that the period of maximum recovery is about 3-6 months post arrest, I don't feel comfortable trying to prognosticate an outcome 2 hours post arrest short of poor pre-arrest function OR significant imaging findings.
So... thoughts on TTM:
- Older studies show benefit, more recent larger, more robust studies seem to show no difference for 33 vs 37 degrees C.
- I agree that likely the benefit is avoiding fever more so than inducing hypothermia
- EMCrit/IBCC recommends scheduled APAP, however given the amount of ischemic hepatitis, I'm concerned about adding insult to injury. Maybe Ofirmev would be better (given lack of first pass metabolism), but cost would be an issue.
- The benefit of TTM, regardless of temp goal, is that it is a proactive management strategy rather than a reactive strategy.
- If we forego starting TTM on everyone post arrest, then we need to be aggressive at starting it if the temperature starts to go up. Similarly, we should be using continuous core temperature monitoring on all post arrest patients regardless of whether we're actively cooling them or not.
EMCrit/IBCC editorial on post arrest TTM:
Post-cardiac arrest management Recommends against 33 degrees C. Recommends aggressive anti fever measures including empiric, scheduled APAP dosing.
Effects of in-hospital low targeted temperature after out of hospital cardiac arrest: A systematic review with meta-analysis of randomized clinical trials. 2015:
Effects of in-hospital low targeted temperature after out of hospital cardiac arrest: A systematic review with meta-analysis of randomized clinical trials - PubMed. 6 studies, 1,418 patients. Low T was associated with good neurologic performance at hospital discharge compared with in-hospital high or not targeted temperature.
Targeted Temperature Management at 33 Versus 36 Degrees: A Retrospective Cohort Study (2020):
Targeted Temperature Management at 33 Versus 36 Degrees: A Retrospective Cohort Study - PubMed. Single center urban hospital, before/after analysis. 782 patients. No mortality difference, however improved neuro intact discharge level with 33 degrees. odds ratio, 1.79; 95% CI, 1.09-2.94
TTM 1 (2013):
Targeted temperature management at 33°C versus 36°C after cardiac arrest - PubMed 36 hospitals, Europe and Australia, 939 patients, no change in outcome. hazard ratio with a temperature of 33°C, 1.06; 95% confidence interval [CI], 0.89 to 1.28; P=0.51
TTM 2 (2021): (other attending's initial email) 1,850 patients, international multicenter trial, no change in outcome. Improvement in mRS: 1.00; 95% CI, 0.92 to 1.09