Journal Feed Weekly Wrap-Up

We always work hard, but we may not have time to read through a bunch of journals. It’s time to learn smarter. 

Originally published at JournalFeed, a site that provides daily or weekly literature updates. 

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#1: Should We Use High-Flow Nasal Oxygen for Intubation?

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High-flow nasal oxygen (HFNO) compared to conventional oxygenation in the OR reduced desaturation, improved lowest oxygen saturation, and prolonged safe apnea time.

Why does this matter?
The literature has been back and forth on HFNO for preoxygenation (PROTRACH) and apneic oxygenation (i.e. FELLOW trial). This study largely focused on HFNO for preoxygenation, but the lines blur as flow is continued after induction.

O’s for the nose
This was a systematic review and meta-analysis of four small RCTs using HFNO for induction for endotracheal intubation and four during procedural sedation. I am going to focus on the trials for intubation. Oxygen desaturation was much lower in the HFNO group, OR 0.06 (95%CI 0.01-0.59); this means a 94% reduction in the odds of desaturation. That is really good. Here is the catch – only 2 RCTs looked at this outcome for induction; one had 80 patients, and one had 10. Desaturation was variably defined as <90-93%; flow rates were 40-70 L/min. That said, the effect size was large, and the upper 95% CI of 0.59 is still clinically significant (i.e. 41% lower odds of desaturation). Minimum oxygen saturation was 5% higher (3 RCTs) and safe apnea time 33 seconds longer with HFNO compared to conventional oxygenation (3 RCTs, 1 excluded for significant heterogeneity). EtCO2 was not significantly different with HFNO. All studies were done in an OR setting and not in the ED, which limits generalizability. In practice, I use HFNO and a NRB to preoxygenate and keep the NC flowing once apneic. I see no downside, and this combined evidence suggests it helps.

Source
The Effectiveness of High-Flow Nasal Oxygen During the Intraoperative Period: A Systematic Review and Meta-analysis. Anesth Analg. 2020 Oct;131(4):1102-1110. doi: 10.1213/ANE.0000000000005073.

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#2: Fluid Overload and ICU Mortality

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Excess IV fluid was associated with increased mortality in critically ill patients.

Why does this matter?
We used to flood patients with fluid during my residency. The dogma was, “You gotta swell to get well.” But 95% of each liter leaks out of the vascular space after an hour in critically ill patients. Fluid overload may impair renal function, prolong ventilation, and increase mortality.

You gotta swell to get well? Ummm…nope.
This was a systematic review and meta-analysis of observational studies. They did not meta-analyze the three RCTs for some reason. They considered ICU mortality at 72h associated with either fluid overload (FO; >5% weight gain) or positive cumulative fluid balance (CFB; i.e. intake > output). For the primary outcome of FO, there was an aRR 8.83 (95%CI 4.30-19.22; only 1 study). That’s high. For positive CFB, the combined 4 studies which adjusted for confounders yielded an aRR of 1.44 (1.18-1.77). Eight studies were combined and found a 19% greater risk of mortality for every excess liter of fluid; RR 1.19 (1.11-1.28). As a secondary outcome, the risk of mortality at any time point (not just 72h) was much greater in patients with FO or positive CFB. Also, mortality was greater in several subgroups with positive CFB: acute kidney injury, sepsis, respiratory failure, and surgical patients. Most of the studies were retrospective, with risk of confounding by indication – sicker patients get more fluid. Still, I think there is probably something real and concerning here.

Source
Fluid Overload and Mortality in Adult Critical Care Patients-A Systematic Review and Meta-Analysis of Observational Studies. Crit Care Med. 2020 Oct 1. doi: 10.1097/CCM.0000000000004617. Online ahead of print.

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#3: Does Low Tidal Volume Matter in the Emergency Department?

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Starting low tidal volume ventilation in the ED is associated with lower mortality and overall better outcomes.

Why does this matter?
We know ARDS-Net lung-protective ventilation (LPV) strategies work to improve patient outcomes. Does it matter if we start right away after intubating in the ED?

What you do matters – even vent settings.
This was a retrospective study of 8 EDs, 4,174 patients total, with 2,437 who received LPV (≤8mL/kg tidal volume). For the primary outcome of in-hospital mortality, those who received LPV had an aOR of 0.91 (95%CI 0.84-0.96). That’s a 9% lower odds of death. There were also several other important secondary outcomes: lower ventilator days, hospital days, and cost. This study included all-comers intubated in the ED and transferred to the ICU in these 8 Canadian EDs. Not all these patients had acute lung injury as the reason for intubation, yet they still did better with low tidal volume. Vent settings matter in the ED. Work with RT and aim for ≤8mL/kg. You may want to review this post – Manage the Vent Like a Pro – or download this Mechanical Ventilation Made Simple cheatsheet.

Source
Lung-Protective Ventilation and Associated Outcomes and Costs Among Patients Receiving Invasive Mechanical Ventilation in the Emergency Department. Chest. 2020 Sep 20;S0012-3692(20)34522-0. doi: 10.1016/j.chest.2020.09.100. Online ahead of print.

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