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Now back to our episode.

3:01

So let's talk about lumbar

3:03

punctures. This is one of my favorite

3:06

procedures in emergency medicine. In

3:08

my opinion, the satisfaction of

3:10

the CSF dripping out of the spinal needle

3:13

into those little clear plastic tubes

3:15

is rivaled only by a couple other procedures

3:18

in our specialty. So to begin, let's

3:20

start by talking about the indications for lumbar punctures.

3:23

Now to lead this section off, I want

3:25

to share a quote from one of my attendings in

3:27

residency that has stuck with me. A

3:30

lumbar puncture is almost never considered

3:33

an emergent life-saving procedure. That

3:36

is 99.9% of the time you are

3:39

performing a lumbar puncture for diagnostic

3:41

purposes and not for therapeutic

3:43

purposes. If you are unsuccessful

3:46

in obtaining CSF, you can still

3:48

just treat the patient for the underlying condition

3:51

that you are concerned and the LP can be performed

3:53

later under imaging guidance. Now

3:56

this doesn't mean that LPs aren't important

3:59

to perform in a timely manner.

3:59

manner. They certainly are.

4:02

If CSF is obtained too

4:04

far in the future after antibiotics

4:06

are given in a case of suspected meningitis,

4:09

the patient is possibly committed to receiving

4:11

the full course of parental antibiotic

4:14

therapy for presumed meningitis regardless

4:17

of the CSF results. There have

4:19

been a few decent studies on the topic and

4:21

consistently it has been found that

4:23

the longer time between antibiotic administration

4:26

and CSF collection, the more

4:29

normal the CSF results will look.

4:31

For example,

4:32

after about four hours the

4:34

CSF culture will likely become sterile

4:37

and the CSF glucose and protein

4:39

levels will begin to normalize with

4:41

near complete normalization occurring at

4:43

the 12-hour mark. However, CSF

4:46

white cell count tends to be unaffected by

4:48

antibiotic administration at least

4:50

in the first 12 to 24 hours. So what you should

4:53

take away from this is that lumbar punctures

4:56

are never life-saving, but they are very

4:58

important. And with that out of the way,

5:01

let's talk indications. There are

5:03

a few conditions in which CSF

5:05

studies are required in order to confirm

5:07

diagnosis.

5:09

Pause the episode for a second. How many

5:11

can you name?

5:13

I can think of at least four. Number

5:16

one, diagnosis of a CNS

5:18

infection such as meningitis or encephalitis.

5:21

Number two, diagnosis of a subarachnoid

5:24

hemorrhage via the presence of xanthrochromia

5:27

when initial imaging is negative but clinical

5:29

suspicion is still present.

5:31

Number three,

5:32

diagnosis of Guillain-Barre syndrome.

5:35

And number four, diagnosis and

5:37

treatment of idiopathic intracranial

5:40

hypertension also known as pseudotumor

5:42

cerebri. This is the rare situation

5:45

where an LP can be therapeutic and

5:47

I would consider performing a therapeutic

5:49

lumbar puncture if I was concerned for

5:51

IAH and the patient had objective

5:54

neurologic deficits on exam.

5:56

Those are the four big indications for

5:58

lumbar puncture in the ED. Now,

6:02

contraindications.

6:03

In general, these terms can be boiled down

6:06

to any cause of increased intracranial

6:08

pressure, anything increasing

6:10

risk of bleeding, or anything increasing

6:12

the risk of iatrogenic infection. More

6:15

specifically, there are 5 contraindications

6:18

you should know. Number 1 is

6:21

the presence of a space-occupying lesion

6:23

with mass effect, such as a tumor

6:25

or an Arnold-Kiran malformation. Number 2

6:29

is coagulopathy with an INR of 1.5 or

6:31

greater.

6:33

Number 3 is thrombocytopenia.

6:36

Some sources say less than 50K is

6:38

a contraindication, however new data

6:41

is showing less than 20K is

6:43

a contraindication, and lumbar

6:45

punctures performed with a platelet count between 20

6:47

and 50K are safe.

6:49

Number 4,

6:50

concern for cellulitis overlying

6:52

the lumbar puncture site, or concern

6:54

for spinal epidural abscess.

6:57

Number 5, traumatic injury to the

6:59

location of the LP, e.g.

7:02

a lumbar spine fracture.

7:03

Now when it comes to patients on anticoagulants

7:06

who you need to perform a lumbar puncture in, the

7:08

decision to perform LP or delay

7:11

is quite nuanced based

7:13

on the exact anticoagulant that

7:15

the patient is taking, the time

7:17

of the patient's last dose of anticoagulant,

7:20

and the results of the patient's labs. There

7:23

is no one-size-fits-all answer here, and

7:25

this topic is way too nuanced to dive

7:27

into on this episode, so just recognize

7:29

that this is a gray area. Complications

7:33

It is very important that you do not forget

7:35

to consent the patients on the complications

7:37

of the procedure. I'll give you guys my

7:39

personal spiel. So

7:42

I break up complications into two categories.

7:45

The first category is complications known

7:47

to every medical procedure that we perform,

7:50

and the second category is complications specific

7:53

to the procedure that we are doing today.

7:55

The complications of every medical

7:58

procedure include pain, and the second category is pain. bleeding,

8:01

damage to nearby structures, need

8:03

for further procedures, disability

8:05

plus or minus death,

8:07

and there are a few complications that are specific

8:09

to lumbar punctures. The first, which

8:12

is the most common, is a post-puncture

8:14

headache, which may require a second

8:16

procedure down the line, known as a blood patch,

8:19

to fix it.

8:20

Anywhere between 5 and 20% of patients

8:22

will develop a post-lumbar puncture headache. The

8:25

second complication is known as a spinal

8:27

hematoma, which can lead to permanent paralysis

8:30

and can be devastating, but is

8:32

pretty rare. I've never seen this occur

8:34

in clinical practice in my experience.

8:37

And number 3, which is extremely rare,

8:40

is brain herniation, which shouldn't

8:43

happen if we adequately assess for

8:45

findings of increased intracranial pressure

8:47

prior to performing the lumbar puncture.

8:50

And lastly, when consenting patients

8:52

for lumbar punctures, I always

8:54

specifically consent them for failure.

8:57

Doing a lumbar puncture blind will never

8:59

be 100% surefire, and

9:02

setting realistic expectations up front

9:05

will go a long way if you are unsuccessful

9:07

in performing the procedure.

9:10

Next, let's talk about the procedure itself.

9:13

A lumbar puncture can be performed with

9:15

the patient either sitting upright, bent

9:17

over

9:17

in a scared cat position,

9:20

or it can be performed with the patient lying on

9:22

their side in the fetal position.

9:25

If measuring opening pressure is of importance

9:28

to you, such as in idiopathic

9:30

intracranial hypertension, you must

9:33

proceed with the patient in the lying position.

9:36

I personally use the sitting position as

9:38

much as possible, as I think it is easier

9:40

to align the patient properly.

9:43

The direction of the bevel is also somewhat

9:45

important to reduce trauma while performing

9:48

the procedure. The way I think about

9:50

it is that the bevel should be pointed in such

9:52

a way that it is always facing the

9:54

patient's mid axillary line. So

9:57

if the patient is upright, the bevel

9:59

should be be facing either left or

10:01

right. And if the patient is lying

10:04

on their side, the bevel should either be

10:06

facing the floor or the ceiling.

10:08

Now, everyone has their own little tricks

10:11

for how they perform procedures. What

10:13

I'm going to share with you is not necessarily the

10:15

best way to do it, so to speak.

10:18

It is just how I personally found success

10:20

in my own experience performing lumbar

10:22

punctures.

10:23

So my first tip is positioning.

10:27

Positioning is everything. Positioning

10:29

will either set you up for success or cause

10:32

you to fail. I first have the patient

10:34

sit at the edge of their stretcher with their feet

10:36

on a stool in front of them. You

10:39

want to align the patient's shoulders and

10:41

their hips so that each joint is

10:43

kind of like a corner on a rectangle. That's

10:45

how I think about it.

10:47

Once positioned, I have the patient bend

10:50

forward and lean on a mayo stand.

10:53

I also ask the patients if they've ever seen

10:55

a scared cat before. You know how

10:57

they kind of stick out and arch their back in

10:59

the air when they're scared? That's

11:01

what I try to have the patients do, and that's how I

11:03

coach them through it. Sometimes I'll

11:05

even pull up a picture on my phone from Google

11:08

showing them exactly what I mean. Now,

11:11

if they do not have good anatomic

11:13

landmarks because of body habitus, the

11:15

last thing I will use to help me is

11:18

ultrasound to find my landmarks. Once

11:21

the patient is positioned, I draw two imaginary

11:23

lines. One vertical line

11:26

across the course of their spinous processes,

11:29

and one horizontal line connecting

11:31

the two posterior superior iliac

11:33

crests.

11:34

Where these two lines intersect

11:37

should be right about at the L4 spinous

11:39

process. And then I mark

11:41

one space above this intersection, corresponding

11:44

to the L3-L4 space, and

11:46

one space below this intersection, corresponding

11:49

to the L4-L5 space.

11:51

Then I grab

11:53

an empty 10cc syringe

11:55

and push it into their back while withdrawing

11:58

on the plunger hard, holding it for me.

11:59

maybe 10 or 15 seconds.

12:02

This will leave a nice bullseye target

12:04

for you that will not wash away when

12:07

you're cleansing the skin prior to the procedure.

12:10

My second tip has to do with finding the subarachnoid

12:12

space. I personally

12:15

have never felt a pop when

12:17

entering the subarachnoid space.

12:19

So, my strategy is

12:21

essentially to insert the needle until

12:23

I hit bone.

12:24

If I don't hit bone and the needle

12:27

keeps advancing, I know I'm either

12:29

in the space or lateral

12:31

to it.

12:32

Ideally, though, I hit bone.

12:34

This tells me that I'm aligned correctly

12:36

horizontally and I just need to change

12:39

my vertical alignment. I will

12:41

then withdraw the needle maybe 1cm,

12:44

change my vertical angle of entry ever

12:46

so slightly, and reinsert the needle.

12:49

While reinserting the needle, I

12:51

pull the stylat out every

12:53

1mm of advancement to check for CSF.

12:56

Yes, this slows me down and is

12:59

painfully slow. I often remove

13:01

the stylat 10 to 30 times

13:04

before I successfully obtain CSF.

13:06

But being thorough and methodical about

13:08

this helps me make sure that

13:11

I'm not overshooting or undershooting.

13:13

And

13:14

those are my personal tips for success.

13:17

Now, finally, we've arrived to

13:19

our last discussion point. The

13:21

age-old question, when do

13:24

I have to CT before LP?

13:26

One could argue that you should always

13:29

CT before LP just to be

13:31

safe. But studies have shown

13:33

the delay to obtaining CSF

13:36

and the delay to antibiotics is

13:38

definitely clinically significant, and

13:40

we should only spend the time CTing if

13:43

absolutely necessary.

13:45

Now, lucky for us, the

13:47

Infectious Disease Society of America

13:50

has published guidelines of when

13:52

you should be obtaining a head CT before LP.

13:56

There

13:56

are 6 situations where you should

13:58

obtain the CT before LP.

14:00

These 6 situations are 1. Patients

14:03

with an altered level of consciousness

14:06

2. Patients with a

14:08

focal neurologic deficit 3. Patients

14:12

with new onset seizures within

14:14

the past week 4.

14:16

Patients with a

14:18

history of CNS disease in the past, such

14:20

as a brain mass 5.

14:22

Patients who

14:24

are immunosuppressed, such as patients

14:26

with HIV 5. Patients who have organ

14:29

transplants, etc. 6. Patients

14:32

who have papillodema on fundoscopy exam

14:35

You can always look these up if you forget, as

14:37

the list is kinda long, but the way

14:39

I remember it is anything that makes

14:41

you suspicious of increased intracranial

14:44

pressure will require a CT

14:46

before LP.

14:48

Okay, whoo! That

14:50

was a lot.

14:51

Let's summarize quickly. 1. Indications

14:54

for lumbar puncture. CNS infection,

14:57

subarachnoid hemorrhage, Guillain-Barre

14:59

syndrome, and idiopathic intracranial

15:01

hypertension.

15:03

2. Contraindications for lumbar puncture. 3.

15:06

Space-occupying lesion with mass effect.

15:09

4. Thrombocytopenia and coagulopathy. 5. Cellulitis

15:12

overlying the LP site or concern for

15:14

epidural abscess, and traumatic

15:17

injury to the spine. The

15:20

complications for lumbar puncture include

15:22

post-lumbar puncture headache, spinal

15:24

hematoma, and brain stem herniation.

15:27

My personal advice for performing lumbar

15:29

punctures, positioning is everything.

15:32

Use ultrasound if necessary, and

15:34

check for CSF early and often.

15:37

And finally, when to see

15:39

T before a lumbar puncture? Essentially

15:42

altered mental status, focal neurologic

15:44

deficit, new onset seizures,

15:47

known CNS lesions, immunosuppression,

15:51

and papillodema.

15:53

And that is all I have for y'all

15:55

today. Send me emails

15:57

with feedback, mike at em.

16:02

Thanks again to our sponsors at Pearson

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Ravitz Insurance and until next month,

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keep working hard, keep studying,

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and be sure to enjoy your

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shift.