Low Tidal Volume Neuroprotective Post-Arrest

Short Attention Span Summary

Low Vt - a neuroprotective agent post-arrest
Yesterday we discussed how lung protective vent strategies started in the ED save lives.  Today we learn how this is also neuroprotective post-arrest.  Odds of neurologically-intact survival after cardiac arrest increased 60% for every 1 mL/kg decrease in tidal volume (Vt) (obviously with a lower limit around 6mL/kg...don't crank it down to zero) compared with patients ventilated at >8 mL/kg.  Those with Vt <8 mL/kg had a cerebral performance category 1 or 2 (CPC 1 or 2 = good outcome) 27% of the time; only 12% with Vt >8 mL/kg had a CPC 1 or 2.  That's a NNT of 7.  They used propensity-adjusted analysis to account for potential confounders.  Lower Vt was also associated with improvement in several other secondary outcomes and didn't appear to have any adverse effects.  Based on this rigorous analysis, I think the results are probably true.  This is big news and easy to implement immediately.

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Simply dialing down the tidal volume < 8 mL/kg improves neurologically-intact survival post-arrest.  For this and other reasons, learn to Manage the Vent Like a Pro.  Not many in the EM FOAM world were talking about this article at the time of this writing, which was pretty surprising.  So share and spread the word.  If there was a drug that made this big an impact on cognitive outcome post-arrest, big pharma would bottle and sell it for billions.


Abstract

Am J Respir Crit Care Med. 2017 Mar 7. doi: 10.1164/rccm.201609-1771OC. [Epub ahead of print]

Favorable Neurocognitive Outcome with Low Tidal Volume Ventilation After Cardiac Arrest.

Beitler JR1, Ghafouri TB2, Jinadasa SP3, Mueller A4, Hsu L5, Anderson RJ6, Joshua J7, Tyagi S8, Malhotra A9, Sell RE10, Talmor D11.

Author information:

1 University of California, San Diego, Division of Pulmonary and Critical Care Medicine, San Diego, California, United States ; jbeitler@ucsd.edu.

2 University of California, San Diego, Department of Medicine, San Diego, California, United States ; tghafouri@ucsd.edu.

3 Beth Israel Deaconess Medical Center, 1859, Department of Anesthesia, Critical Care, and Pain Medicine and Department of Surgery, Boston, Massachusetts, United States ; sjinadas@bidmc.harvard.edu.

4 Beth Israel Deaconess Medical Center, Department of Anesthesia, Critical Care, and Pain Medicine, Boston, Massachusetts, United States ; almuelle@bidmc.harvard.edu.

5 University of California, San Diego, Department of Medicine, San Diego, California, United States ; lehsu@ucsd.edu.

6 University of California, San Diego, Department of Medicine, San Diego, California, United States ; rja002@ucsd.edu.

7 University of California, San Diego, Department of Medicine, San Diego, California, United States ; jjoshua@ucsd.edu.

8 University of California, San Diego, Department of Medicine, San Diego, California, United States ; styagi@ucsd.edu.

9 University of California, San Diego, Division of Pulmonary and Critical Care Medicine, San Diego, California, United States ; amalhotra@ucsd.edu.

10 University of California, San Diego, Division of Pulmonary and Critical Care Medicine, San Diego, California, United States ; rsell@ucsd.edu.

11 Beth Israel Deaconess Medical Center, Department of Anesthesia, Critical Care, and Pain Medicine, Boston, Massachusetts, United States ; dtalmor@bidmc.harvard.edu.

Abstract

RATIONALE:

Neurocognitive outcome after out-of-hospital cardiac arrest (OHCA) often is poor even when initial resuscitation succeeds. Lower tidal volumes (VT) attenuate extrapulmonary organ injury in other disease states and are neuro-protective in preclinical models of critical illness.

OBJECTIVE:

To evaluate the association between VT and neurocognitive outcome following OHCA.

METHODS:

Propensity-adjusted analysis of two-center retrospective cohort of OHCA patients who received mechanical ventilation for at least the first 48 hours of hospitalization. VT was calculated as the time-weighted average over the first 48 hours, in mL/kg predicted body weight (PBW). The primary endpoint was favorable neurocognitive outcome (cerebral performance category 1-2) at discharge.

MEASUREMENTS AND MAIN RESULTS:

Of 256 included patients, 38% received time-weighted average VT > 8 mL/kg PBW during the first 48 hours. Lower VT was independently associated with favorable neurocognitive outcome in propensity-adjusted analysis (OR 1.61, 95% CI 1.13-2.28 per 1 mL/kg PBW decrease in VT; p=.008). This finding was robust to several sensitivity analyses. Lower VT also was associated with more ventilator-free days (ß = 1.78, 95% CI 0.39-3.16 per 1 mL/kg PBW decrease; p=.012) and shock-free days (ß = 1.31, 95% CI 0.10-2.51; p=.034). VT was not associated with hypercapnia (p=1.00). While the propensity score incorporated several biologically relevant covariates, only height, weight, and admitting hospital were independent predictors of VT ≤ 8 mL/kg PBW.

CONCLUSIONS:

Lower VT following OHCA is independently associated with favorable neurocognitive outcome, more ventilator-free days, and more shock-free days. These findings suggest a role for low-VT ventilation after cardiac arrest.

PMID: 28267376