Neuraxial Anesthesia and Intracranial HTN

[drlee]

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I have a patient in labor requesting an epidural. She is a primigravida and has a history of Arnold-Chiari malformation and is s/p VP shunt placement. Currently she denies having any symptoms of intracranial HTN. Her shunt is fully functional per her neurologist. I'm aware of the dangers of increased ICP with labor pain and the benefits and risks of neuraxial anesthesia with pts with intracranial HTN. My question is : would you place an epidural in this patient?

Is intracranial HTN a contraindication for epidural anesthesia? How about spinal anesthesia? Different reasons?
😕

 

[drlee]

I am aware also that accidental dural puncture ("wet tap") leading to a csf leak can lead fatal brainstem herniation. Can someone explain the mechanism? Isn't lumbar puncture one of the treatment modalities for intracranial HTN??

 

[Fastrach]

Wow...great question...

This is how I understand it...

A CSF leak can lead to a brainstem herniation in the presence of increased ICP and a block in CSF outflow within the cranium. Basically, things move from high pressure to low pressure. Since CSF is unable to flow, the brain is up next, so it herniates.

Lumbar puncture is not supposed to be used to treat intracranial HTN if there a block in CSF outflow, because it can result in herniation.

Although her CSF outflow may be blocked by the malformation, it seems that this patients ICP is relieved by her VP shunt, so you don't have much to worry about. I would do an epidural.

I vote no... though it's an epidural, I'd wanna steer clear of any chance of getting into that subarachnoid space. If she did get a dural puncture and got a headache, just think of the headache that's gonna cause YOU and everyone else-- "Is there a shunt malfunction?" "Did she get a shunt infection or meningitis from the epidural?" "Oh my god, is she herniating?!"

Just not worth it, unless there's a really damn good reason to do it.

 

[seinfeld]

AS always risk benefit. Is it worse for the patient to have continured intemittment bouts of increased ICP from splinting secondary to pain or better to have epidural. Obviously the patient needs to understand the risk but if the shunt is funtional epidural away. If the patient appears to additional risk factors where a GA would be far more likley to increase m/m i would also take that into account.

I looked this up years ago and remember a retrospective cohort study on the matter, ill see if i still have the reference.

 

[Fastrach]

Ok, this is straight out of Spinal and Epidural Anesthesia by Cynthia Wong:

" Neuraxial anesthesia has been safely used for the management of patients with a shunt without complications. Although some have argued that radiologic studies should be performed in order to ascertain the exact location of the shunt prior to initiating a neuraxial technique, others have performed neuraxial techniques safely without the aid of imaging studies. There are no reported cases of trauma to the spinal portion of a lumboperitoneal shunt. Shunts are typically located at a low intervertebral space (L3-L4 or L4-L5) and the tubing runs laterally to the peritoneum. Common sense dictates the insertion of the needle at an intervertebral space below or above the scar, depending on the location of the shunt. There is also concern that drugs in the CSF may leak into the atrium or peritoneum, depending on the shunt type. Therefore, theoretically, a single-shot spinal is not the preferred neuraxial technique. Because of the risk of shunt infection, it has been recommended that prophylactic antibiotics be administered prior to initiating neuraxial techniques.
Symptoms of shunt failure, such as headache and increased ICP, may be confused with postdural puncture headache. Safe and successful performance of an epidural blood patch has been reported in a patient with a lumboperitoneal shunt. Although there are no reported cases of patients with third ventriculostomy receiving neuraxial techniques, neuraxial anesthesia is not contraindicated and the decision as to the type of anesthesia should be based on surgical considerations and the neurologic status of the patient.

Table 5-2 Anesthetic Considerations of Patients with Increased ICP

Neuraxial Anesthesia:
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May attenuate the increased ICP that results from painful uterine contractions
Dural breach may increase the supratentorial-infratentorial pressure gradient and result in brain herniation
Epidural drug injection may increase ICP

General Anesthesia:
-------------------------
Induction, airway manipulation, and emergence may increase ICP
Some drugs such as succinylcholine may increase ICP"

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So again, I'd personally prefer to stay away from an epidural in this population, but I can see how I might get talked into it if the situation warranted. Additionally, I thought the part about giving prophylactic antibiotics before placing the epidural was interesting, and put my mind a little more at ease with regards to introducing bugs in these pts.

 

[DET0897]

Wow...great question...


Although her CSF outflow may be blocked by the malformation, it seems that this patients ICP is relieved by her VP shunt, so you don't have much to worry about. I would do an epidural.

However, keep in mind that with this patient, she still has (at least partially) non-communicating CSF flow (assuming the VPS was placed due to symptomatic increased ICP.) The VPS did not solve that problem, but rather it relieves her symptoms when her intracranial pressure becomes too high from the lack of CSF flow to the spinal canal due to the ACM-I.

My thought is that, theoretically, if you drain a bunch of CSF from the lumbar area, you could cause a pressure gradient across the ACM-I. The VPS won't help if the pressure in the cranial vault is normal (or below the shunt settings if there is a valve), while the pressure in the spinal column is low. Her problem then isnt elevated ICP, but now the possibility of symptomatic herniation.

 

[DET0897]

Ok, this is straight out of Spinal and Epidural Anesthesia by Cynthia Wong:
s.

I've read that as well, and think it is poorly worded. In the paragraph prior to the one you posted, she lumps together non-communicating hydrocephalus (aqueduct stenosis etc..) and communicating hydrocephalus (IVH at birth etc). She then writes the above posted paragraph which includes data (references 46,47) from lumbar shunts in patients with pseudotumor cerebri.

I am finding it difficult to apply these data to the OP patient.