POD Aortic Dissection

jonas pologe · September 14, 2018 · Ultrasound, Cardiovascular

A patient came to the north side today with an acute aortic dissection. Here are images obtained by the ultrasound team when the patient first came in.

A suprasternal view showing an intimal flap:

A short axis view of the abdominal aorta showing an intimal flap

Diagnosis was made, BP meds started, cardiothoracic consulted, and CT expedited.

CT showed a severe type B thoracoabdominal aortic dissection:

Aortic Dissection

Pathophysiology:

Tear in the intima (inner most layer), bleeding into the media (middle layer)

Diagnosis of aortic dissection is very time sensitive:

mortality is directly proportional to time elapsed between symptom onset and diagnosis/treatment

How does it eventually kill you? (I think it’s important to ask this question about all disease processes)

acute aortic regurgitation —> cardiogenic shock

Cardiac tamponade —> obstructive shock

Major brach-vessel obstruction —> vasodilatory shock from dead organ or limb

Aortic rupture —> hemorrhagic shock

2 types that we care about: Stanford Type A and Stanford Type B

Type A

involves ascending aorta

— surgical — a/w aortic rupture, tamponade, aortic regurg, AMI, stroke — more common (68%)

Type B

does not involve ascending aorta — medical (BP control and monitoring) — a/w limb/organ ischemia — less common, (32%) — usually originates just distal to L subclavian artery

Classic history: old person,

very hypertensive

;

abrupt onset

tearing/ripping chest pain

radiating to bac

k; a/w neuro symptoms e.g.

weakness/numbness

(due to vessel branch occlusion); a/w syncope/diaphoresis/N/V

Other risk factors include Marfan’s, connective tissue disease, FHx aortic disease, known aortic valve disease, recent aortic manipulation (e.g. TAVR, surgery), known thoracic aortic aneurysm, tobacco; rarely 3rd trimester pregnancy, TB, syphilis, vasculitis, blunt trauma

Classic physical: Pulse deficit (present in <20% of cases), unequal BP in upper/lower extremities, neuro deficits, signs of tamponade

Diagnosis:

Labs: basics, coags, trop, consider d-dimer (actually high sensitivity/NPV for dissection due to blood often clotting I false lumen)

CT angio aorta: gold standard for diagnosis of aortic dissection

CXR: not sensitive, not specific — sometimes mediastinal or aortic knob widening, few other nonspecific signs

TEE: is an excellent modality that’s in the works but we don’t have it operational yet

TTE: next best thing, as usual with ultrasound it’s specific but not sensitive - see below

Ultrasound for aortic dissection — obtain the following views:

Subxiphoid: look for pericardial effusion

Parasternal long: look for effusion, look at the descending aorta, look for aortic regurg with color doppler and measure the aortic root (nl <4cm) if you want to be fancy

Suprasternal window:

look for dissection flap (image from University of Maryland department of cardiology)

Probe above the the patient’s sternum pointed inferoposteriorly with probe marker to patient’s left (assuming cardiology convention)

Abdominal aorta scan: look for dissection flap from diaphragm to iliacs, also measure diameter in short and long

Management (From the AAC/AHA aortic dissection guidelines):

ACC AHA AoD Treatment-Algorithm

Note: When blood pressure is intact, first bring heart rate with beta blockers, then control pain, then see if they need further BP control.

The Bougie POD

jonas pologe · September 11, 2018 · Airway

Awwww yisss, airway stuff!

I’d like to start this POD off by talking about the study that got everyone buzzing about the bougie this summer, published last June in JAMA by Driver et al. at Hennepin:

Effect of Use of a Bougie vs Endotracheal Tube and Stylet on First-Attempt Intubation Success Among Patients With Difficult Airways Undergoing Emergency Intubation, A Randomized Clinical Trial

Numbers and outcomes:

They randomized 757 patients: 381 to a bougie-first approach, 376 to a traditional styletted ETT-first approach
Population was >18, undergoing intubation with a Macintosh (standard geometry) blade (direct or video, how much the intubator looked at the screen was at the teams discretion)
380 patients had at least one difficult airway feature
Success on 1st attempt was 98% in bougie-first group vs 87% in ETT+stylet group, P=0.0001, NNT=9
Success on 1st attempt in patients with difficult airway features was 96% in bougie-first group vs 82% in ETT+stylet group, P<0.0001, NNT=7

Let’s just state what that last NNT means in words to let it sink in: You have use a bougie on 7 patients with difficult airway features in order to prevent one first-pass failure.

Furthermore, the bougie held its own among every stratification, e.g.:

Obese patients: (96% vs 75%)
Patients that needed cervical in-line stabilization: (100% vs 78%,)
Patients with poor views (Cormack-Lehane grades 2 to 4): (97% vs 60%)

A few other noteworthy things:

The duration of the first pass was about the same between bougie and ETT groups,
The total time of intubation was far longer in the ETT group, owing to more often needing multiple attempts passes
No difference in complication rate or direct airway trauma

Bottom line: This is extremely compelling evidence that first pass success is improved with use of a bougie.

We massively underutilize the bougie. Let’s improve our first pass success and use it more often.

I would especially consider using a bougie as first pass if you’re a less-experienced intubator or you’re starting to learn DL. Furthermore, even if you want to be old school and use it “only as a backup/rescue device”, heaven help you if you actually have to use it as such and have never practiced using it.

For anyone that may not be 100% familiar…

How to use a bougie:

get a view
pass your bougie through the cords, the coudé tip helps guide it anteriorly where it needs to go
you know you’re in the trachea because it stops around the carina (be gentle, airway perforations are sub-optimal), you can also theoretically feel the subtle clicking of the tracheal rings as it slides down the trachea
your assistant slides the tube over the back end of the bougie and then stabilizes the back of the bougie while you railroad the tube over it and through the cords
keep retracting the tongue with the laryngoscope while you do this to facilitate passage
you may encounter some resistance when it reaches the arytenoids; twisting the tube solves this problem
you can definitely do all this by yourself too, it’s just a little trickier to maneuver all the moving parts

The bougies used in the Hennepin study were 70 cm gum elastic (blue) bougies, the same ones we stock in our ED. These as well as slightly shorter 60cm bougies are stocked in most departments you might work in. Thanks to Reuben we also now stock the purple malleable bougies! These excellent devices and will save you when you run into weird geometry and can even be used with hyperangulated laryngoscopes but this is a little harder. When I use them as a regular bougie, I’ll usually give them a slight coudé tip and mild anterior bend like that of the ETT and revise if necessary. The stopper can be taken off or used to pre-load the tube.

Superficial Cervical Plexus Block POD

jonas pologe · September 7, 2018 · Ultrasound, Procedures

That’s right. Time to talk about my favorite nerve block.

The SCPB

This block is

quick

and

easy

It makes

IJ central lines

painless procedures

It also provides excellent analgesia for

clavicle fractures

ear lobe lacerations

blind subclavian lines

, or

anything within this quadrilateral

How to do it

Find the

posterior aspect of the sternocleidomastoid (SCM) muscle

Position the probe half way down the SCM as you measure it from mastoid process to clavicle.

About at the level of the superior aspect of the thyroid cartilage, also about where the EJ crosses over the sternocleidomastoid.

The fascial plane under the posterior aspect of the sternocleidomastoid muscle is your target.

Like other

plane blocks

you are not targeting any one nerve in particular. By infiltrating this tissue plane, you get the superficial plexus as it peeks out from behind the SCM at this level:

Inject 5-10 cc of local anesthetic.

Ensure it is spreading in the plane like this.

Safety:

As with all ultrasound guided nerve blocks, visualize your needle tip always, especially prior to injection.
When you begin injecting, inject one mL only to ensure you see it spreading in the fascial plane. Then inject the rest.
Withdraw before you inject if there is even a slight possibility you are close to a vessel
Throw some color on your site to ensure you identify any vessels.
In general this is a very well tolerated and forgiving block.
The incidence of phrenic nerve involvement is extremely low with SCPB, far lower than with the interscalene block. Phrenic nerve involvement will be avoided if ensure you don’t go too deep - a few cm, or about half way down the deep edge of the SCM. Going deeper than this results in a deep cervical plexus block which will result in some motor and sensory blockade of the arm.
Horner’s syndrome is a rare and self-limiting complication.
The amount of local anesthetic used in this block is nowhere near close to toxic levels, so local anesthetic systemic toxicity will not occur as long as you manage to avoid the IJ and carotid.

Tips and troubleshooting

For a central line, you can set up, gown, drape, and set up your ultrasound like usual, then use the 5 cc lidocaine which come in the central line kit for your block. Place the block first, then flush your line/lay out your equipment, and your patient will likely be completely numb by the time you’re ready to start your line placement.
The other option is to place your block while you’re doing your pre-scan. This way you can use 5-10 cc, but you have to get it out of the Pyxis. Just clean the probe and the skin with a chlorhexidine swab and use sterile gel.
If it’s your first time doing a block, consider doing it as a 2 person block. Use some IV extender tubing and have another provider operate the syringe for you. I like slightly longer tubing than typical IV tubing, e.g. the one below. At Maimo, you can find it in the stock room between North and South sides, top shelf straight ahead when you first walk in.
Can't visualize your needle? Make sure your ultrasound probe is directly above it and in-line with it. Next, make sure it is as close to parallel to the surface of the probe/perpendicular to the ultrasound beams as possible. If you are approaching a 45 degree angle, your needle will be close to invisible. At close to a 0 degree angle, it will shine like a laser beam.
You can use the 27 gauge needles to make it more comfortable but they are a little harder to see.