I’ve argued (along with many others) that we need to shift cardiac arrest resuscitation from just going round in circles on an algorithm to a physiological approach where we actually measure the impact of what we are doing.
During CPR we have relied we’ve relied on end‑tidal COâ‚‚ and manual pulse checks, but we know that these are not particularly dynamic and in the case of pulse checks a bit of a random result generator. I’ve argued before on St Emlyn’s that we need to shift from process-based to physiology-based resuscitation. If we truly believe in measuring the effect of our interventions, then invasive monitoring, which at the moment really means placing arteriual lines is something that we can achieve and is not something that is reserved for the ICU. Arterial lines have the potential to allow us to see what’s actually happening. If we want to individualise care, titrate compressions, identify ROSC more reliably, and move toward targeted perfusion pressures (like aiming for a diastolic >35 mmHg), then Artertial lines are one route to get us there.
This week we have a paper by Akerman et al. which is really a letter, that outlines the experience of one unit that has brought intra-arrest arterial lines into their practice. It’s not the most definitive of papers, but it is interesing and worth a peek if you are interested in introducing them to your practice.
What Kind of Study Is This?
This is a retrospective case–control study. You have to be careful with this design as it is very prone to bias as described below. That said we can look at the main characteristics and consider ‘how’ that bias may manifest. Have a look at the details below and ask yourself how these may influence the results.
- Location: Quaternary care emergency department in the United States (so single centre)
- Time frame: January 2018 – November 2024 (quite a long time)
- Data source: Video review of cardiac arrest cases in a prospectively maintained registry (actiually a really good approach andn much better than asking people what they do, they actually measured it!)
- Study design: Patients who had intra-arrest arterial line placement attempts were compared to those who didn’t
- Operators: Three experienced emergency medicine attendings, all using ultrasound guidance (so only a small group)
This is not a randomised trial and the decision to place an arterial line was at clinician discretion. The aim was to assess feasibility, with exploratory outcomes on ROSC and survival. I’d love to hear more about how they manage to video resusciations for research and learning though,. I suspect this is an invaluable tool for learning.
Tell Me About the Patients
- Total patients reviewed: 375 adult cardiac arrest cases, which is a decent number but……
- The Intervention group was only 49 patients (13.1%) with at least one arterial line placement attempt during CPR. This suggests a degree of selection bias in the patients. What made them choose this group, were they easier to do, more likely to survive etc. We just don’t know
- Control group: 326 patients with no A-line placement attempt.
- All A-line attempts:
- Performed in the ED
- Ultrasound-guided
- Unclear whether femoral of radial (or other)
- We don’t know what kit or technique used
- Conducted by a small group of experienced attendings
What we don’t have, unfortunately, are detailed demographics:
- No breakdown of initial rhythm, cause of arrest, or time to first CPR
- No details on prehospital care or comorbidities
- No information on witnessed status or downtime
That makes interpretation of group comparability a bit tricky. It is highly likely that there are differences between those who had an attempt and those that did not. That’s not so much a criticism of the authors, but it is a function of this kind of study design and something we should always be wary of.
What Were the Measured Outcomes in This Study?
Procedural metrics:
- Number of attempts per patient
- Duration of each attempt (in seconds)
- Time from first attempt to successful placement
- Cumulative success rate by number of attempts
Clinical outcomes:
- Return of spontaneous circulation (ROSC)
- Survival to hospital admission
- Survival to hospital discharge
The focus here was primarily on procedural feasibility, but the authors also looked to see whether there were any signals of clinical benefit.
5. What Are the Main Results?
In feasibility terms they found:
- 82 arterial line attempts across 49 patients (not many over 6 years)
- Median attempts per patient: 1 (IQR 1–2)
- Median time per attempt: 102 seconds (IQR 71–143)
- Median time to successful placement: 226 seconds (IQR 99–252)
- Cumulative success rate plateaued at ~90% by the third attempt
- Success dropped below 25% after attempt number three
Clinical outcomes were not the main point of thisn study but are still interesting to look at:
- ROSC:
- Arterial line group: 71.4%
- Control group: 44.8%
- Statistically significant (p = 0.01)
- Survival to hospital admission:
- Arterial line: 28.6%
- Control: 28.8%
- Not significant (p = 0.90)
- Survival to discharge:
- Arterial line: 0%
- Control: 6.9%
- Not statistically significant (p = 0.14)
So overall, this looks fairly reasonable. Roughly 62% of lines went in first time and pretty quickly. More than 3 attempts seems fairly futile. The interesting thing is that it did not lead to improved patient outcomes, in fact it appears to be (no significantly) worse in the arterial line group for discharge (although higher rates of ROSC). This may be a survivor bias effect, but again we just don’t know.
What about the Methodology
This is not a definitive trial design, but it is of interest. The video review is really good and something I’d like to see more of (though the ethics and governance needs to be really tight on this). The fact that experienced clinicians using ultrasound can get a line in under four minutes during CPR, with moderate success, is an impressive demonstration of what’s possible in high-functioning teams, and is similar to what we have seen in high performing prehospital teams. So both in and out of hospital this is a feasible technique.
However, we have to be cautious here. The decision to place an A-line wasn’t random, it was made by clinicians at the bedside. That introduces a lot of selection bias. It’s entirely plausible that patients selected for A-line attempts had better prognoses from the outset. Maybe they had shorter down-times, better rhythms, or more favourable clinical features. We just don’t know. Compounding that is the lack of demographic detail which makes that even harder to assess. Without knowing who these patients were, shockable vs non-shockable, witnessed vs unwitnessed, it’s difficult to assess how comparable the groups were.
The increase in ROSC is interesting, especially as it didn’t translate to improved survival to discharge. But more than that, i need to understand what the a-line added. Just measuring something is unliklely to impact patient outcomes. If we are to use advanced monitoring then we should have a better idea of what that leads to. Maybe that’s a different way of delivering CPR, or medications or something else. Again we don’t know.
Also worth noting: all the lines were placed by three very experienced physicians. That’s not representative of every ED or every training environment. If we want to generalise this to other settings, we need to consider who will be placing the lines and whether they have the skills and support to do it safely.
Should We Change Practice Based on This Study?
No. Not yet.
We need larger, prospective studies, ideally randomised, to evaluate whether intra-arrest monitoring actually improves meaningful outcomes, and also what makes a difference to things like DBP. We need to explore how we interpret arterial line waveforms in real time, how we integrate them into CPR decision-making, and what to do when they show us poor perfusion. Just seeing a pressure isn’t enough, we have to be able to act on it.
If you’re working in a centre where you have the skills and systems to support arterial line insertion during arrest, then now might be the time to start exploring this, with clear protocols, governance, and simulation-based training. But for most departments, I’d suggest caution and curiosity in equal measure.
Summary
This study helps us understand arterial lines in the cardiac arrest setting. I am an advocate, but to be honest the data is not there for prime time. I think that it makes physioplogical sense, but we really need more data.
References.
- Akerman M, Cohen AL, Haddad G, Rolston DM, Jafari D. Arterial Line Placement Is Feasible During Emergency Department Cardiac Arrest. Resuscitation. 2025. doi:10.1016/j.resuscitation.2025.110740
- Simon Carley, “Non-invasive or arterial pressure monitoring in PHEM?,” in St.Emlyn’s, September 29, 2024, https://www.stemlynsblog.org/non-invasive-or-arterial-pressure-monitoring-in-phem/.
- Simon Carley, “Is Diastolic Blood Pressure the New Resuscitation Target,” in St.Emlyn’s, February 15, 2025, https://www.stemlynsblog.org/is-diastolic-blood-pressure-the-new-resuscitation-target/.
- Simon Carley, “Intra-Arrest Arterial Blood Pressure and Return of Spontaneous Circulation in Out-of-Hospital Cardiac Arrest.,” in St.Emlyn’s, November 22, 2024, https://www.stemlynsblog.org/intra-arrest-arterial-blood-pressure/.
