We Don’t Know the Midclavicular Line

The Gist:  Needle decompression for tension pneumothorax should be taught at the fourth or fifth intercostal space at the anterior axillary line (4/5ICS AAL). 

  • Note: This post will not detail critiques that needle decompression may be overused or the needle vs thoracostomy debate.

Historical teaching instructs providers to place a needle in the second ICS at the mid-clavicular line (2ICS MCL) for tension pneumothorax [1,2]. Free Open Access Medical Education (FOAM) sources such as Emergency Medicine Ireland have preached the more lateral approach for years; yet this teaching has not spread widely (outside of military circles where there seems to be better adoption). Change is difficult, particularly when it involves re-educating thousands of providers and it seems like this is the primary driver behind the 2ICS MCL remaining as the typical site for needle decompression..  However, several potential problems exist with the mid-clavicular approach that warrant consideration for assuming 4/5ICS AAL as the primary initial placement for needle decompression.

A: Where I see most needles placed, B: 2ICS MCL, C: 5ICS AAL
We may not be able to reach the pleura [3-5].  The chest wall may be particularly thick at the 2ICS MCL, particularly as the average BMI in many nations grows.  Researchers have looked at this question for years through a couple of means - measuring the depth at the 2ICS MCL on CT scans of trauma patients compared with alternative sites. The 2ICS MCL is generally 1.3 cm thicker than 5ICS AAL. 
  • This discrepancy was not solely seen in the morbidly obese.  In fact, it was seen consistently across all four BMI quartiles tested, and at the traditional insertion site, needle decompression would have been extremely difficult with any eccentric placement using a standard needle in all but the lowest BMI quartile [3].
How often would the needle fail?  A systematic review and meta-analysis in Injury 2015 by Laan et al looked at 17 studies, generally cadaveric or radiographic, and found that a standard 5 cm catheter used for needle decompression at the 2ICS MCL would fail 38% (24–54%) of the time compared with only 13% (8–22%) at ICS4/5-AAL (p= .01) [5].
  • The British Thoracic Society Guidelines (2010) even remark “a standard 14 gauge (4.5 cm) cannula may not be long enough to penetrate the parietal pleura..with up to one-third of patients having a chest wall thickness >5 cm in the second interspace.”
  • In some places, the failure rate may be even higher secondary to obesity [5].
What about a longer needle?  Many catheters used for needle decompression are 5 cm in length; however, some have access to 8 cm angiocatheters.  A analysis by Clemency and colleagues found that in order to achieve a success rate of 95%, we would need a catheter at lease 6.4 cm in length [8].  Similarly, Laan and colleagues conducted a pre-post retrospective study in an EMS system that switched from using 5 cm catheters to 8 cm catheters with an increase in success rate (48% vs 83%) [6].  For a life saving, last ditch effort, I'm not sure that 95% success rate is adequate when alternatives exist.

We don’t identify this site well [10,11].  A 2005 paper by Ferrie and colleagues had 25 emergency physicians name the correct side for needle thoracentesis and label this site with a pen on a male volunteer (erased between providers).  Nearly all participants were ATLS certified within the past 10 years.  
  • 88% (n=22) named the correct site (one additional person did name the 5ICS AAL).
  • Only 15 of the 25 participants (60%) could correctly identify the 2ICS MCL [10].   
In another study, Inaba and colleagues trained 25 US Navy corpsmen on needle decompression, using both the 2ICS MCL and the 5ICS AAL. The corpsmen then performed needle decompression at both sites on randomly selected cadavers, bilaterally.  
  • Mean distance from the correct location: 3.1 cm 2ICS MCL vs 1.2 cm 5ICS AAL
  • Correct placement (ICS +/- 5 cm):  15/50 (30%) 2ICS MCL vs 41/50 (82%) 5ICS AAL
  • Limitations: This study had multiple outcomes and no power analysis was performed [11]
I think much of this is because we underestimate the length of the clavicle.  It's easier when you can see the chest wall bones but we don't have this advantage in the clinical setting.  On a person, the midclavicular line often seems fairly lateral.  


Important structures surround the 2ICS MCL.  As mentioned above, we seem to have a tough time finding the 2ICS MCL [8,9]. There are important structures in this vicinity, particularly if the tendency is to go more medial than the actual midclavicular line, including the internal mammary artery and contents of the superior mediastinum.  Naturally, should an individual placing a needle in the 4/5ICS AAL go too caudal the possibility exists for the needle to enter the liver or spleen but the study by Inaba and colleagues suggest we may be better able to identify this space [9].

Given the literature, it seems that at this time should a needle be placed aiming for the 2ICS MCL for needle decompression and fail, this is a failure of education and changing our knowledge base rather than a patient-based failure. We should know better.

References:

  1. MacDuff A, Arnold A, Harvey J. Management of spontaneous pneumothorax: British Thoracic Society pleural disease guideline 2010. Thorax. 2010;65(Suppl 2):ii18–ii31.
  2. Advanced Trauma Life Support, 9th ed. 
  3. Inaba K, Ives C, McClure K, Branco BC, Eckstein M, ShatzD, Martin MJ, Reddy S, Demetriades D. Radiologic evaluation of alternative sites for needle decompression of tension pneumothorax. Arch Surg. 2012;147(9): 813Y818.
  4. Inaba K, Branco BC, Eckstein M, Shatz DV, Martin MJ, Green DJ, Noguchi TT, Demetriades D. Optimal positioning for emergent needle thoracostomy: a cadaver-based study. JTrauma. 2011;71(5):1099Y1103; discussion 103.
  5. Laan D V., Vu TDN, Thiels CA, et al. Chest wall thickness and decompression failure: A systematic review and meta-analysis comparing anatomic locations in needle thoracostomy. Injury. 2015:14–16. 
  6.  Laan D, Berns KS, Habermann EB. Needle thoracostomy: Clinical effectiveness is improved using a longer angiocatheter. 2015. doi:10.1097/TA.0000000000000889.
  7. Hecker M, Hegenscheid K, Völzke H, et al. Needle decompression of tension pneumothorax. J Trauma Acute Care Surg. 2016;80(1):119–124. doi:10.1097/TA.0000000000000878.
  8. Carter TE, et al. Needle Decompression in Appalachia Do Obese Patients Need Longer Needles? West J Emerg Med, 2013; 14(6): 650–2
  9. Clemency BM, Tanski CT, Rosenberg M, May PR, Consiglio JD, Lindstrom HA. Sufficient catheter length for pneumothorax needle decompression: a meta-analysis. Prehospital and disaster medicine. 30(3):249-53. 2015.
  10. Ferrie EP, Collum N, McGovern S. The right place in the right space? Awareness of site for needle thoracocentesis. Emerg Med J. 2005;22(11):788–789.
  11. Inaba K, Karamanos E, Skiada D, et al. Cadaveric comparison of the optimal site for needle decompression of tension pneumothorax by prehospital care providers.

GCS: Saying What We Mean

The Gist:  The Glasgow Coma Scale (GCS) is widely used, yet complicated by clunkiness and poor inter-rater reliability (explanation of kappa).  The Simplified Motor Score (SMS) is easier to use and equivalent, although this is prone to similar limitations.  Until a better means of communicating mental status comes, it may be best to communicate what the patient is doing (opening eyes to voice, moaning incomprehensibly, localizing pain). See this ScanCrit post.

The Case: A 29 year old male involved in a MVC with multiple traumatic injuries resulting in a prolonged ICU course at Janus General had a tracheostomy placed for respiratory failure.  The patient was responding appropriately to questions, following commands, opening his eyes spontaneous and lacked any signs of confusion or delirium, mouthing words, but was awaiting tracheostomy exchange for a fenestrated trach with a Passy-Muir valve.  What's the patient's GCS? Does this patient's GCS reflect their mental status?
  • Documented at as 10NT, 11T, and 15 by various providers.  The arguments behind each: 10NT - cannot test verbal, 11T -one point for showing up, 15 -patient oriented, and saying appropriate words, just without phonation.
In medicine, we communicate through abbreviations, codes, and numbers. When we see heart rate or blood pressure values we can place these numbers in the context of our knowledge of the patient’s peers. These numbers become actionable.  

Other critical components to the physical exam and evaluation are less easily quantified.  The mental status, for example, is a key component to evaluating a patient.  The GCS was developed to communicate the mental status of a head injured individual among providers during continuing care in a neurosurgical unit [1].  It is often used to track neurologic status when transferring care or over time.  A particular GCS in the prehospital setting may also qualify a patient for a trauma activation in some settings. 

Limitations: Unfortunately, unlike other vital signs, scores don't have explicit meaning.  The total GCS is often reported, yet this 13 point scale (3-15) actually has 120 different possible combinations.  A patient with a GCS of 10 may be completely oriented but totally paralyzed or be moaning incomprehensibly with their eyes own and a withdrawal reflex present.  Further, the sum of the GCS does not equal the parts, with regard to mortality. Healey et al used the National Trauma Database to model mortality predictions based on GCS and found that the same total sum score could be associated with double the mortality (ex: from 27% to 52%) depending on the individual components. Further, the mortality associated with scores is not linear [3].  So a GCS of 11, for instance may mean very different things for two different patients.

Yet, even if the numbers did mean something, the GCS has been found to have abysmal inter-rater reliability.  In one study, 19 emergency physicians rated 131 patients within five minutes of each other found a concordant GCS 32% of the time (Spearson's rho 75, weighted kappa 0.40) [4].   Even in the rather protected setting of case based written scenarios, emergency providers the overall GCS accuracy was 33.1% (95% CI, 30.2-36.0) [5].  In a written mock scenario, EMS personnel (n=178) generated an accurate GCS one-quarter of time without a scoring aid and a shocking 57% with the use of a scoring aid [7].

Alternatives: Given the inaccuracy of the GCS, Thompson et al set out to determine whether the performance of the SMS, a truncated version of the GCS was equivalent to the GCS in a retrospective cohort of out of hospital head injured patients. In the SMS, points are awarded for obeying commands (2), localizing pain (1), and withdrawing to pain or worse (0). They found that the predictive nature of the SMS paralleled that of the GCS, although the GCS seemed to predict mortality slightly better,  0.90 using GCS (0.88-0.01) vs 0.87 using SMS (0.86-0.88) [7].

So, what do we do?
Trashing the GCS is simply not an option for most of us; yet, score cards don't seem to do us any favors.  For example, during a trauma activation, the expectation (at least at Janus General) is to communicate to the room the patient’s GCS.  This may seem to convey more neurologic information than the actual exam discriminates. Recognizing the limitations to the GCS is important in discerning both what we do with this information and how we communicate what we mean, whether it's in documentation, to other providers, or family members.

  • Describe the exam.  With the knowledge of the subjectivity and poor reliability of the GCS, one may give the breakdown of points rather than a simple total GCS and describe the neurologic examination.  Documenting descriptors in medical records this may aid other teams in tracking the patient's exam.  
  • We may also engage in interdisciplinary discussions about use of simplified scoring systems such as the SMS or about the ways we communicate and document neurologic exams. 
References:
1. Green SM. Cheerio, laddie! Bidding farewell to the Glasgow Coma Scale. Ann Emerg Med. 2011;58(5):427–30. doi:10.1016/j.annemergmed.2011.06.009.
2. Singh B, Murad MH, Prokop LJ, et al. Meta-analysis of Glasgow Coma Scale and Simplified Motor Score in predicting traumatic brain injury outcomes. 2013;27(March):293–300. 
3. Healey C, Osler TM, Rogers FB, et al. Improving the Glasgow Coma Scale score: motor score alone is a better predictor. J Trauma. 2003;54(4):671–678; discussion 678–680. 
4. Beveridge R, Ducharme J, Janes L, Beaulieu S, Walter S. Interrater reliability of Glasgow Coma Scale scores in the emergency department. Ann Emerg Med. 2004;43(February):215–223. 
5. Bledsoe BE, Casey MJ, Feldman J, et al. Glasgow Coma Scale Scoring is Often Inaccurate. Prehosp Disaster Med. 2014. doi:10.1017/S1049023X14001289.
6. Feldman A, Hart KW, Lindsell CJ et al. Randomized controlled trial of a scoring aid to improve glascow coma scale scoring by emergency medical services providers. Ann Emerg Med. 2015 Mar;65(3):325-329.e2.
7. Thompson DO, Hurtado TR, Liao MM, Byyny RL, Gravitz C, Haukoos JS. Validation of the Simplified Motor Score in the out-of-hospital setting for the prediction of outcomes after traumatic brain injury. Ann Emerg Med. 2011;58(5):417–25. 

FOAM on the Spot – A Needle in a Haystack?

At the SAEM conference, I had the privilege of partaking in a didactic with Dr. Anand Swaminathan, Dr. Ryan Radecki, and Dr. Matt Astin entitled, "FOAM on the Spot - Integration of Online Resources into Real-Time Education and Patient Care."

The cornucopia of free open access medical education (FOAM) resources may be overwhelming and I get frequent requests for guidance sorting through the cornucopia of FOAM.  People often have the question, "I remember hearing about this technique but I can't recall which site and want to review it..."  As such, I've posted a recording of my portion of the didactic here.

The Gist:
  • Filter FOAM by searching relevant information - FOAMsearch [1].
    • Customized Google search engine of 300+ blogs related to EM/critical care plus journal articles.
  • Engage in the community of personal librarians - Twitter (a few pearls on Twitter)
    • Tag others when you have a question
    • Participate in discussions and "be the librarian" for others.
  • Use a system to stay organized and collate resources - AgileMD.
    • Pro - Can collate several FOAM blogs, PV cards from Academic Life in Emergency Medicine, WikEM, and podcast notes all in one application on a smart phone/tablet.
    • Con - Presently can only build a "library" from a limited number of resources.
As a rather junior individual, selfishly, always welcome constructive feedback on my talks. This is my experiment in crowdsourcing feedback from the FOAM community to become a better presenter.


1. Raine T, Thoma B, Chan TM, Lin M. FOAMSearch.net: A custom search engine for emergency medicine and critical care. Emerg Med Australas. 2015;(March):n/a–n/a. doi:10.1111/1742-6723.12404.