Tuesday, November 27, 2018

Speed Matters: Landmark Guided Left Subclavian Vein Central Venous Catheter Insertion & the "Deep Spot"

Recently, I got permission from a patient to video a subclavian line insertion.  This patient was absolutely terrified of any line insertion as he had had many in the past and a lot of them had been traumatic, prolonged, and painful.  I offered a bedside subclavian as an alternative to a PICC line or a right internal jugular in Interventional Radiology, promising that the entire procedure could be done in under 10 minutes.  It took just over 2 minutes, excluding prepping, draping, locally anesthetizing, and suturing.  These aspects would have added about another 3-4 minutes to the task.  Before the video started, I had infiltrated the area generously with 2% lidocaine, after prepping and draping in the usual careful fashion.

Before you watch the video, I should describe the essence of subclavian landmarking and several mandates of the procedure.  The key anatomical landmark is a spot seen in the photo accompanying this post that I call "the deep spot."  This is a spot along the inferior border of the clavicle, about 4 inches from the suprasternal notch (SSN).  It is important because it is the spot where soft tissue adjacent to the inferior border of the clavicle can be depressed the deepest, allowing the needle the easiest access to the subclavian region while being inserted "FLAT, FLAT, FLAT, FLAT, FLAT" under the clavicle with respect to the ground, i.e., parallel to the ground.  Entering the subclavicular region in this spot and remaining flat/parallel to the ground are keys to both success and avoidance of the oh-so-feared (but rare!) pneumothorax.

This spot can be found by making the middle finger and the thumb of the non-dominant hand into a comfortable "C" shape as seen in the photo.  The middle finger and thumb will be parallel to each other when in the "C" shape and will be about 4-5 inches apart depending on your fingers and the patient's anatomy.  With the middle finger in the SSN, the thumb finds the spot along the inferior border of the clavicle where the skin can be depressed the deepest.  If you're too medial, you will be atop ribs and "too high not deep enough" and if you're too lateral from the SSN, you will start climbing up the humeral head and deltoid and be "too high, not deep enough".  If you are too close to the clavicle or atop it, you will not be in the "deep spot" (it is a finger breadth or so inferior) and if you go too inferior from the clavicle, you will climb atop the pectoralis/breast and not be in the deepest spot.  Find the "deep spot"!  Again, the point (no pun intended) is to find the spot where the tissues near the clavicle can be depressed the deepest to facilitate the insertion of the needle under the clavicle and parallel to the ground.  This cannot be overemphasized, and you can feel for that spot on yourself or a willing companion for practice.

Once this spot is located, you anesthetize and then use the needle to confidently identify the clavicle and by advancing the needle towards the SSN, you can press down with your thumb on the needle (even the part under the skin) to depress it so that when advanced, it is parallel to the ground towards the SSN and it goes easily under the clavicle.  You should never "dive" to try to get under the clavicle, or use the clavicle as a fulcrum, bending the needle downward.  Watch the video carefully to see how I'm using several tactile inputs to determine where the clavicle is as I guide the needle under it.  You will see that the first several "pokes" or short advancements of the needle hit the clavicle (it happens fast, watch carefully!) which is a very important tactile confirmation of where you are, and then I push the inserted needle down with the left thumb to allow the advancement to proceed below the clavicle.

As seen in the video, the SCV is often entered when the needle is maximally inserted ("hubbed") with the skin invaginating, or upon withdrawal.  Notice too in the video that the flash was subtle at first and too rapid a withdrawal might have missed it.  Also in the video, the flash was highly positional, and the exact optimal position had to be found by iterative advancement and withdrawal and then maintained by carefully pinching the hub of the needle with the hand referenced to the patient's chest to allow the wire to be fed without inadvertent and unrecognized migration of the needle out of the vessel.

The voice overlay of the video gives several other useful tips and I hope you enjoy watching it.  The SCV central line is one of the final remaining procedures where use of ultrasound guidance (USG) confers minimal, if any benefit, and USG markedly prolongs this (and all) procedures.  Over my career during the past 20 years, I estimate I have done 500 or more SCV catheters all guided by landmark, most in critically ill patients.  I had *one* pneumothorax (PTX), in 2011 in a patient with severe COPD.  (I also supervised a resident once where there was a PTX, and to this day I don't understand how it happened.)  In properly trained hands, this procedure is incredibly safe, is the preferred location for a central venous catheter in terms of patient comfort, and infection and thrombosis risks, can be performed with a very high success rate using landmarks alone, and can be done very speedily.  Speed is the final frontier: Safety, Success, Speed.

Saturday, September 29, 2018

Activated Charcoal and Beta Blocker Overdose: Clinical Decision Making and the Risks of Dichotomization

This very nice case report in the current issue of the Annals of the ATS is an opportunity to discuss rational clinical decision making.  The authors did almost everything that I would have done in this case and it is a lovely discussion of this toxidrome and its treatment.  There is just one simple and apparently inconsequential decision that I disagree with and I intend to use it as a springboard to discuss rational clinical decision making.

The young woman had a multidrug overdose including metoprolol succinate, extended release.  She presented in shock.  The authors state "Gastrointestinal decontamination was not performed because her ingestion was suspected to have occurred several hours before admission" [emphasis mine].  I have already in an early post on this blog, discussed the inadequacy of the existing data and experimental models on the timing of charcoal administration, which interested readers can read about here.

Studies of the timing of Activated Charcoal (AC) administration use normal volunteers taking therapeutic doses of drugs (for ethical reasons).  We have inadequate data on the speed of absorption of drugs in people who are shocked or who take very large doses of drugs, or extended release drugs.  To dichotomize the efficacy of AC by a bright line of 30 or 60 or even 120 minutes is a gross oversimplification of reality that belies overconfidence in the existing data and experimental models.  This patient took a large dose of a sustained release medication and at some point became shocked presumably causing splanchnic vasoconstriction.  She also took Tramadol and other medications which may slow gut motility via anticholinergic or other effects.  And there may be other unknowns - other medications she took that slowed absorption of the sustained release metoprolol that we don't even know about.

Tuesday, May 15, 2018

Root Cause Analysis: Dig Deeper, or the Weed Will Keep Growing Back

In a recent JAMA Performance Improvement piece, the authors describe the case of a man who presented to the emergency department with dizziness.  He was sedated for an MRI, his history of OSA (obstructive sleep apnea) may have been glossed over, and he arrested in the radiology department.  The subsequent "root cause analysis" traced the untoward outcome to a failure to recognize the OSA and the adverse effects that may follow sedation of a patient with this diagnosis.

The problem with this "root cause analysis" is that it assumed that the MRI, requested by a neurologist on-call, via telephone, was necessary.  It was not.  The root cause analysis got it wrong because it did not trace the roots to their deepest source:  glossing over the patient's chief complaint and considering it and its evaluation carefully and rationally.  Stroke is an uncommon cause of dizziness and the MRI was probably not indicated, especially in light of the other information provided in the case.

Here is the letter that I sent to JAMA which was not accepted/published.  It is a case of the distinction between rationality and intelligence.  Very intelligent people traced the "cause" or the "root" of the complication to a missed piece of information (OSA) and corollary ideas (he may have complications from sedation), but they failed to consider underlying assumptions:  namely that the MRI was necessary or would yield net benefit in the first place. 

Medicine is best played like chess, not like checkers.  "Intelligent people have superior performance when you tell them what to do."  A failure of a "root cause analysis" such as this will foment the regrowth of the weed.

Here is the letter:

I enjoyed the Performance Improvement case describing oversedation of a patient with obstructive sleep apnea1.  I posit that the most proximate possible root cause of the complications described was ordering an MRI with low clinical yield2, without pre-specifying what abnormality was being sought as well as its probability, and without delineating, a priori, how any resulting findings would change management3.  Presumably, the neurology consultant was looking for stroke.  What was its pre-test probability in a patient with dizziness?  Would management have changed if stroke were detected with imaging?  Were there contraindications to therapies for stroke?  Was the patient already receiving the indicated therapy for stroke?  What is the probability of a false positive finding (i.e., one that doesn’t explain the patients’ symptoms; an “incidentaloma”), and how might that finding lead to interventions which may yield net harm if stroke is not present?  What was the response to meclizine and odansetron, and how did this incremental information alter the prior probability of stroke?  Because decisions necessarily precede actions, they must always be considered as possible proximate causes of downstream complications.  Even if the other errors identified in the reported root cause analysis can be avoided in the future, injudicious testing may lead to other complications, including cascades of additional potentially harmful testing and intervention unguided by careful, rational, clinical decision making.

1. Blay E, Jr, Barnard C, et al. Oversedation of a patient with obstructive sleep apnea prior to imaging. JAMA 2018;319(5):495-96. doi: 10.1001/jama.2017.22004
2. Fakhran S, Alhilali L, Branstetter BFt. Yield of CT angiography and contrast-enhanced MR imaging in patients with dizziness. AJNR American journal of neuroradiology 2013;34(5):1077-81. doi: 10.3174/ajnr.A3325 [published Online First: 2012/10/27]
3. Pauker SG, Kassirer JP. The threshold approach to clinical decision making. The New England journal of medicine 1980;302(20):1109-17. doi: 10.1056/nejm198005153022003 [published Online First: 1980/05/15]

Confusion, Diaphoresis, and Hyperventilation Aboard a Private Airplane

This was intended to be a case report but the amount of work required to publish a case report is just too great to justify it.  The publishing landscape has been flooded with an attendant raft of predatory journals, so one must be very careful.

This will be an online interactive case report.  I will tweet this post, asking for comments and diagnoses in the comments below (preferable to twitter comments) and update with the answer and a discussion in 1-2 weeks.

A 68 year-old otherwise healthy male passenger was flying with his friend, a pilot, in a private plane from California to Montana for a fishing trip.  Within an hour after takeoff, he became confused and diaphoretic and was hyperventilating, then he lost consciousness for approximately 20 minutes.  The pilot applied supplemental oxygen and checked his passenger's arterial oxygenation via oximetry, finding it to be 95%.  The flight was diverted for a medical emergency.  During descent and landing, the passenger regained consciousness but remained confused.  In the emergency department of a nearby hospital, he had normal vital signs, and had a non-focal neurological examination, but remained confused.  Representative images from CTA of the chest are shown below (click on the images to expand).  A head CT was normal excepting for some age related atrophy.  What is the diagnosis?