End Tidal CO2 in TBI

Does End Tidal CO2 correlate with PaCO2 in Traumatic Brain Injury?

Your neurosurgeons and trauma team have accepted a transfer to your hospital for intensive management of a trauma patient who presented to a small community hospital with a traumatic subarachnoid hemorrhage and epidural hematoma after being involved in a motorcycle accident.

Upon arrival with the critical care transport team, the patient is already intubated and stable on a a ventilator with appropriate sedation and stable hemodynamics.  However, the neurosurgeons are in the operating room managing a spontaneous intraparenchymal hemorrhage and there are no available ICU beds due to multiple gun shot victims from a gang fight that you finished admitting.

While the patient is in the ED, the neurosurgeons recommend maintaining eucapnea for the patient since while there are no acute signs of herniation.(1). 

Can you use the end tidal CO2(etCO2) or do you need to rely on arterial blood gas (ABG) measurements to maintain PaCO2 between 35-40 mm Hg? 

In trauma patients the most robust evidence for the correlation between etCO2 and PaCO2 comes form a prospective observational study in Emergency department patients at a single center conducted by Lee et. al in 2009.(2)  The median difference of PaCO2 and etCO2 was 3.6 mm Hg and greater in patients with severe hypotension and lactates > 7 mm/L.  To have maximal safety it is safe to assume that the etCO2 generally underestimated the PaCO2 by at least 5 mm Hg and the PaCO2 can be at least equal but possibly higher than the etCO2.

However in poly trauma patients especially those with severe chest and abdominal trauma there was as little as a 29% acceptable correlation of 5mmHg between the etCO2 and the paCO2.(3)  In those cases Warner et al. in 2009 concluded that there is an unacceptable correlation between etCO2 and PaCO2 in the very sick and severely injured trauma patients.  It is more likely that the etCO2 is artificially low and is a measure of relative perfusion and less correlated with the PaCO2 and ventilation.  These patients should have arterial PaCO2 measurements performed by ABG and most likely will benefit from an arterial line for monitoring resuscitation efforts.

Case conclusion: Since the patient remained hemodynamically stable on the ventilator and only suffered from isolated TBI, you performed an initial ABG at found a PaCO2 of 37 mmHg and observed an etCO2 of 39-41 mm Hg by waveform capnography.  For the next 3 hours in the ED you continued to monitor the etCO2 and did not perform any repeat ABGs. 

Bottom Line:  End tidal CO2 will differ most from PaCO2 in the severely injured and in patients with shock.  In isolated hemodynamically stable Traumatic Brain Injury, the etCO2 should correlate relatively well by at least 5mm Hg.

For more details and a continually updated list of evidence for this topic see:

  1. Badjatia N, Carney N, Crocco TJ. Guidelines for prehospital management of traumatic brain injury 2nd edition. Prehospital Emergency Care. 2008;12(s1):S1S52. doi:10.1080/10903120701732052.
  2.  Lee S-W, Hong Y-S, Han C, et al. Concordance of End-Tidal Carbon Dioxide and Arterial Carbon Dioxide in Severe Traumatic Brain injury. J Trauma. 2009;67(3):526530. doi:10.1097/TA.0b013e3181866432
  3. Warner KJ, Cuschieri J, Garland B, et al. The Utility of Early End-Tidal Capnography in Monitoring Ventilation Status After Severe Injury. J Trauma. 2009;66(1):2631. doi:10.1097/TA.0b013e3181957a25.
Edited by Manpreet Singh

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International traveling with medications?

It’s something that most don’t think about. Many readers of this blog are lucky enough to not have chronic medical problems, but not all are. Still, most of us regularly interact with an increasing number of patients with chronic conditions. And more and more of those patients are traveling internationally, potentially due to the treatments they are now able to receive. But what are the rules for people travelling with their medications and medical devices?


These authors set out to figure out how hard it is to find the requirements for travellers who may need to bring medications or medical devices with them. They determined 25 popular destination countries for Australian tourists, and then searched their embassy websites for 5 categories of information pertaining to medications, required documentation, and customs information. They also sent an email to each embassy requesting information about the same topics. They then rated the embassy websites using the RATER scale, which is a modified Service Quality tool (SERVQUAL).

In 2 weeks, they got responses back from 11 of the 25 embassies they had emailed. This lack of service was mirrored by the impressively low scores the embassy websites received on their RATER scales. And even though the title and attempt of the study was to include medical equipment, neither the email responses nor the websites gave any guidance on medical equipment.

More concerning is the fact that no country followed the recommendations of the International Narcotics Control Board, which is an independent body that exists to help carry out the UN Drug Control Conventions.  All of them had more restrictive policies, some so severe as to require the patient to go to a local physician to certify that the medication is needed. Now, we mostly talking about narcotic and psychotropic medications, and generally supplies of less than 30 days. Anabolic steroids will also raise eyebrows in many countries.

Basically, the recommendations boil down to these.

  • Only possess your own medications
  • Carry the prescription or other documentation for those medications
  • Check with competent authorities in your destination countries well before travelling

For travelers planning on spending more than 30 days? Not much guidance, as you probably will have difficulty bringing it through customs initially, and you may have trouble getting prescriptions filled once there. And for those with medical devices (think neurostimulators), make sure to carry backup batteries and plenty of documentation for them.

Unfortunately, while the thought behind their study was valiant, the poor response rate combined with apparently terrible embassy websites means that each person travelling with controlled medications has their homework cut out for them. Still, without much else out there, it gives everyone a place to start.

Note that this doesn’t apply to medical providers carrying medications for expedition or humanitarian purposes. There is an entirely different set of rules for that.

Travelling with medications and medical equipment across international borders

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On the internet, nobody knows if it’s 25C-NBOMe (“N-bomb”)

25C-NBOMe (N-bomb)

25C-NBOMe (N-bomb)

2 out of 5 stars

25C-NBOMe: Preliminary Data on Pharmacology, Psychoactive Effects, and Toxicity of a New Potent and Dangerous Hallucinogenic Drug. Bersani FS et al. Biomed Res Int 2014;2014:734749. Epub 2014 Jul 3.

Full Text

The NBOMe drugs are phenethylamine derivatives of the 2C psychedelics. The 2 methoxybenzyl groups act to provide protection and stability, drastically increasing the potency of this drug. Although sometimes sold as LSD, 25C- NBOMe (N-bomb) is much more potent and dangerous.

This article uses both published scientific literature and discussions on Web bulletin boards and chat groups in an attempt to define the effects of this drug. The authors argue that since the internet is a crucial factor in marketing and disseminating novel psychoactive substances and since peer-reviewed articles about these substances are scarce, using unconfirmed anecdotal reports on sites like Bluelight and Drugs-Forum is justified.

I don’t buy it. However, the authors do reference several medical papers about N-bomb. for example,  a recent article by Grautoff and Kahler described a 19-year-old man who supposedly snorted N-bomb and developed seizures, acute kidney failure and acute lung failure. Unfortunately, the article is in German and the abstract does not specify whether the exposure was laboratory-confirmed.



10 Tips from Nurses to Rock Your EM Clerkship

There are lots of ways to prepare for clerkship, like finding mentors, reading up, and making learning goals, as outlined in this past post. While those tips will help you maximize your skills building and demonstrate your professional competencies, it’s also important to use clerkship as an opportunity to learn how to work as part of an interdisciplinary team within a complex health care system. There is growing recognition that quality care and patient safety depend on teamwork, and evidence demonstrates that increased collaboration between physicians, nurses, and allied health professionals helps improve client outcomes [1]. With that in mind, here are tips from nurses to help you work with respect and synergy as part of the team.

10 Tips from Nurses to Rock Your EM Clerkship

Tip 1 – Be courteous

Often health care providers can be so focused on their patients and the endless tasks at hand that we can forget what it means to be courteous. Emergency departments can be hectic places full of people in crisis, but we can still take a few moments to exercise common courtesy with our colleagues. Start conversations with “hello” or “how are you?” and introduce yourself (#hellomynameis isn’t just for patient interactions). This allows us to build professional relationships from a place of trust and respect.

Other daily courtesies apply to workplace settings, too. Respectful and polite language, like saying “please” and “thank you”, sharing workspaces, returning supplies and charts when you’re finished with them, remembering to log off computers – all of these things help improve workflow and can make a sometimes chaotic environment just a little more pleasant. Other tips for being courteous in the workplace are available from the business sector here.

Tip 2 – Capitalize on other people’s expertise

There’s a reason that health care has interdisciplinary teams with specialties and sub-specialties – we can’t all know everything. Make the most of the variety and depth of knowledge that surrounds you. Nurses, especially, know the patients, staff, policies, and hospital well, and appreciate being recognized as a resource. We are (typically) with our patients for 8-12 hours at a time and are very familiar with their baseline status, so please trust us when we are worried, and listen to our concerns. This interesting paper takes a “pragmatic view of intuitive knowledge in nursing practice” and highlights the importance of a nurses’ intuition [2]. We’re also happy to show you what we know, especially if you’ll teach us something, too.

Tip 3 – Strategically pick your timing

Research shows that, like physicians, nurses also face many interruptions. One study showed that nurses are interrupted once every 6 minutes [3]. While it’s great to ask questions, solicit and give feedback, and have an open dialogue with colleagues, there are better and worse times for these discussions. Refrain from interrupting procedures, and wait until we have completed our assessment to start yours. Know that all health care providers are juggling a lot of competing priorities, and although we want to support your learning and attend to your patients, we may need to prioritize something else, so please be patient. Having said that, if you have immediate concerns about patient safety, speak up.

Tip 4 – Strategically pick your location

Pick your location wisely when questioning someone’s practice or debating a plan of care. Don’t do so in front of a patient, unless there is an immediate safety concern or bedside rounds are standard at your institution. Those conversations are probably best saved for the charting station, not the hallway, where patient confidentiality is easily compromised. When picking a location to do extra reading or learning, choose somewhere where you won’t be interrupted by people maneuvering around you for supplies or charts. When picking a location to watch a procedure, be mindful of sterile fields and introduce yourself to the patient and provider(s) rather than silently hovering.

Tip 5 – Practice Stewardship: Leave your patients, colleagues and the department how you found them or better

Nothing feels more disrespectful than someone leaving their mess for me to clean up. It’s definitely best practice to remove bedding, clothing, dressings and diapers to examine your patients, but please put them all back when you’re done. If there’s a complex wound, feel free to ask when the next dressing change is so that you can assess it then, or at least let the nurse know that you’ll have to remove a dressing so we can plan our care accordingly. Return or throw-out supplies when you’re finished a procedure, and dispose of all your sharps properly. If you don’t know where something goes, ask instead of putting it away in the wrong place. Ask your colleagues how you can help and what you can do to help make their job easier. Ask patients if there is anything they need before you leave the room.

Tip 6 – Take responsibility for patient safety

Little things make all the difference, even when you are a medical student. Leaving patients in better shape than you found them is also about patient safety. This means assuring that bed-rails are put back up and the call-bell is within reach. A significant number of patients experience adverse events in the hospital, especially falls [4]. Keep this in mind when mobilizing patients, and communicate fall risk with the rest of the healthcare team.


Hand hygiene is an important part of patient safety – so important that it warranted its own section. We all know that practicing hand hygiene is the number one way to reduce the spread of infection. But it’s incredible how few healthcare providers do it properly or as often as they should. Brush up on best practices and follow them.

Tip 8 – Do not touch things if you don’t know what they are

If you’re going to change or remove any tubes, pumps, IVs, or ventilator settings, please let us know. Unless you are totally familiar with how to use them, please do not touch them without asking first, as the nurse probably spent a significant amount of time setting them up, untangling them, and completing safety checks. If you’re curious about what a patient is hooked up to, just ask! Also, it’s best to keep your hands to yourself when observing a sterile procedure.

Tip 9 – Take care of yourself

Adjusting to long shifts can be physically and mentally exhausting. It’s harder to care for others if we’re not caring for ourselves. It’s your own responsibility to assure that you’re fed and watered and ready to learn. We are all doing what we can to take care of ourselves and our patients, so please don’t rely on others to take care of you, too. Remember, many of your nursing colleagues have had years of experience with working shifts. If you’re having trouble, reach out to them, as they will likely have some tried and true tips to share.

stolen foodTip 10 – Do not steal anyone’s snacks

Just trust me.

Acknowledgements: Thanks to my colleagues for their input on this post, including the nurses at BC Children’s Hospital and those who contribute to the online forums at reddit/r/nursing. Check out the great Reddit feed started by Claire for even more advice. 

This post was edited by Teresa Chan and Eve Purdy.


  1. Martin, J. S., Ummenhofer, W., Manser, T., & Spirig, R. (2010). Interprofessional collaboration among nurses and physicians: making a difference in patient outcome. Swiss Med Wkly, 140, w13062.
  2. Billay, D., Myrick, F., Luhanga, F., & Yonge, O. (2007) A pragmatic view of intuitive knowledge in nursing practice. Nurs Forum ; 42(3): 147-55. (http://www.ncbi.nlm.nih.gov/pubmed/17661807)
  3. Kalisch, B. J., & Aebersold, M. (2010). Interruptions and multitasking in nursing care. Joint Commission Journal on Quality and Patient Safety36(3), 126-132. (https://www.researchgate.net/publication/42253476_Interruptions_and_multitasking_in_nursing_care)
  4. Hitcho, E. et al. (2004). Characterstics and circumstances of falls in a hospital setting. J Gen Int Med; 19(7): 732.789. (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1492485/)

Author information

Eve Purdy
Medical Student Editor at BoringEM
Fourth year medical student at Queen's University-happily consuming, sharing, creating and researching #FOAMed

The post 10 Tips from Nurses to Rock Your EM Clerkship appeared first on BoringEM and was written by Eve Purdy.

Should the 48-hour Cardioversion Window Be Revised?

It has become generally accepted practice to treat new-onset atrial fibrillation and atrial flutter with electrical cardioversion in the acute setting – provided the known onset of atrial fibrillation is less than 48 hours.  Beyond that, caution tends to be advised – whether through use of transesophageal echocardiography to rule out left atrial thrombus, or through pre- and post-procedural anticoagulation.

However, this data from a research letter in JAMA suggests – possibly we ought to be even more cautious regarding time-of-onset.

This is a re-analysis of FinCV, a 7 year trial registry of cardioversion for atrial fibrillation from Finland.  The study cohort is comprised of 2,481 patients undergoing 5,116 electrical cardioversions, all without peri-procedural anticoagulation for symptom onset <48 hours.  Outcomes were gathered from vital records review, evaluating for cerebrovascular thrombotic complications within 30 days.

Of these patients undergoing cardioversion, there were 38 definite thrombotic complications.  30 of these 38 occurred in patients whose symptom onset was >12 hours.  There were few apparent pro-thrombotic differences between groups, and thus, the authors very reasonably conclude – we should be cautious regarding cardioversion after 12 hours.  Other predisposing factors in their multivariate analysis include female sex, heart failure, and diabetes – but increasing length of time showed the strongest association.

The 12-48 hour window in this study still only represented a 1.1% risk for 30-day thromboembolism, compared to the ~2% risk after 48 hours.  However, it still exceeds the ~0.3% risk of thromboembolism with peri-procedural anticoagulation.  There are other risks associated with anticoagulation, but it is reasonable to suggest the management strategy is no longer as clear-cut around 48 hours.

“Time to Cardioversion for Acute Atrial Fibrillation and Thromboembolic Complications”

Tension Pneumothorax – an alternative view

Ever since I was a junior medical officer and I was faced with a spontaneous tension pneumothorax at sea on a dived submarine…I have had an interest in managing pneumothorax.

A tension pneumothorax is the presence of intrapleural air that is under positive pressure throughout the entire respiratory cycle. It occurs when air enters the thorax through a pleural defect but can not leave (a one way cat flap). We have all been taught that we should never see a chest x-ray of a tension pneumothorax, with good reason. It is a diagnosis that should be made on clinical grounds only and certainly never have a chest x-ray performed to confirm your suspicion (although here is one… well, these things happen).

Tension Pneumothorax

Of all of the clinical signs that we have been taught to recognise – it is the rapidity of deterioration of a patients’ clinical condition, in the context of known, or clinical signs of a pneumothorax that should make you think of the presence of a tension. Learned texts speak of distended neck veins, tracheal deviation and a displaced apex beat (very difficult to ascertain); these are late signs and clinicians should have considered and be acting upon the diagnosis before these are present.

Prompt recognition and treatment is key – traditionally we have been taught needle decompression in the second intercostal space, mid-clavicular line. Whilst this does facilitate timely access to the pleural space for some – it may not be the best anatomical choice for all – but more of that (and ideal needle length) another time…

So, if we are agreed that we should not be seeing chest x-rays of tension pneumothoraces – what about a CT scan of tension pneumothorax?

What features can been seen on this CT?

  • Increased thoracic volume R side
  • Displaced mediastinum
  • Collapse and occlusion of the right main bronchus. Just distal to the carina it forms a crescent shape and then occludes. The whole of the right lung is collapsed as a result.
  • Collapse of left lower lobe
  • A large bore chest tube in situ in the right thoracic cavity with no apparent occlusion of the tube

It is worthwhile stopping and considering for a moment some of these features present on the scan. We are used to hearing about a displaced mediastinum which, as it worsens, we understand to gradually occlude the vena cava causing eventual reduction and cessation of venous return to the right ventricle. But what about complete collapse of the right main bronchus? Anatomically, there are intact concentric rings of cartilage at this point in the bronchial tree. To cause collapse and occlusion of these rings there must be a very considerable positive intrathoracic pressure acting upon them.

Experimental physiological data on this subject are sparse to give reliable estimates, but it is known that a pressure of 6Kpa (~60cm/H20) will cause the posterior membrane of human trachea to invaginate with surface contact between the membrane and lateral walls. The likelihood of collapse is greater when there is longitudinal tension or flexion on the trachea. In this case with right main bronchus collapse, the concentric cartilagenous rings should (in theory) be able to withstand more pressure before deformation or collapse than the incomplete ‘C’ shaped rings in the trachea. Perhaps in this case the additional longitudinal tension and/or flexion on the bronchial tree as the mediastinum was deviated modified that likelihood.

This individual already had a 28F chest tube in place following penetrating thoracic trauma and a haemopneumothorax – this was subsequent ‘traumagram’ CT. He was clinically stable going in – says he felt dreadful in the scanner, and quickly better when the gantry moved back out again. Considering the patient had a patent chest tube at the beginning of the investigation and a patent tube as we rushed in straight after the investigation – what could have happened?

So what happened?

We think that the chest drain tubing got snagged in the gantry as the patient moved into the scanner. This occluded the tube, stopping egress of air from the thoracic cavity, resulting in increasing intrathoracic pressure and ultimately a tension on the affected side.

Either way, this case allows you to appreciate the gross cardiopulmonary insult a tension pneumothorax can induce in a short space of time.

Take home message

Transfer of the traumatised and/or critically ill patient requires careful handing and planning ahead – particularly when moving parts are involved. Tubes, lines and monitoring wires may all be sitting safely before the scan starts – but think ahead to where all these items will be when the patient has moved into the scanner!


  1. Brims F. Primary spontaneous tension pneumothorax in a submariner at sea. Emergency medicine journal: EMJ 2004;21:394. [Full Text]
  2. Begis D, Delpuech C, Le Tallec P, Loth L, Thiriet M, Vidrascu M. A finite-element model of tracheal collapse. Journal of applied physiology 1988;64:1359-68. [Abstract]
  3. Leigh-Smith S, Harris T. Tension pneumothorax–time for a re-think? Emergency medicine journal : EMJ 2005;22:8-16. [Full Text]

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