Precedex

[fabfive5]

Can the seniors please tell how / when / what cases they use Precedex for? We use it a lot in peds but I am trying to get more comfortable with it and would like the elders to elaborate.

Thank you

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[cchoukal]

I use it in the ICU more than the OR, but I'll outline some of my uses below:

OR:

1) Part of a varied cocktail for TIVA/Balanced anesthetic for neuro-monitoring cases. I typically don't bolus.

2) Continuous sedation for regional or local cases in patients w/ pulm HTN (in whom changes in minute volume caused by more traditional sedatives can be problematic).

3) people have used this for sedation for awake intubations, and I think it's even been randomized and studied, but I don't find that it is any better than midaz and fent, as long as you're well topicalized (which, frankly, is 99% of the anesthetic for an awake intubation).

ICU:

1) Sedation for vented patients when we've been out of propofol. It's definitely harder to get patients synchronous with this, particularly when using low tidal volume/lung protective strategies, compared with propofol, and doses often exceed the FDA-approved 0.7.

2) Alcohol withdrawal syndrome: although it hasn't been studied in humans, this is a great drug for managing the delusions, agitation, and hemodynamic changes associated with AWS. It should be noted, however, that it does not provide prophylaxis against seizures and therefore should not be the solo agent for AWS. I would be shocked if someone isn't out there randomizing patients to Dex vs Placebo and counting up how much benzo they're sparing.

3) Sedation for the medically delirious elderly patient. The effect here is often quite profound. I would add, though, that this, like AWS, is an off-label use of the drug. When used for this purpose, it's a little hard to know when to d/c it.

 

[IlDestriero]

TIVA.
MEG scans.
Awake fibers.

What are you using it for outside of the ICU?

 

[proman]

How do you use it for TIVA?

 

[sevoflurane]

Prolly 1 mcg/kg/hr for 30 minutes then .5mcg/kg/hr for the rest of the case. Particularly useful in neuromonitoring cases.

 

[sevoflurane]

Also:

http://www.anesthesia-analgesia.org/content/111/2/490.short

We have premixed 20mcg/10cc syringes and 40mcg/10cc syringes that the pharmacy makes up. I use it often and for just about any case that has a high sympathetic outflow that doesn't get a sympatholysis with 2-4mcg/kg of fentanyl.

 

[cchoukal]

How do you use it for TIVA?

It's tricky in that it is thought not to produce hypnosis or amnesia, so you have to have something else on board, like propofol or some inhalational agent. If you're going to add propofol for amnesia, you might as well just use propofol and skip the dex altogether, in my opinion.

My main OR use these days is to combine it with sufentanil and desflurane for heads and backs with neuromonitoring.

 

[proman]

It's tricky in that it is thought not to produce hypnosis or amnesia, so you have to have something else on board, like propofol or some inhalational agent. If you're going to add propofol for amnesia, you might as well just use propofol and skip the dex altogether, in my opinion.

My main OR use these days is to combine it with sufentanil and desflurane for heads and backs with neuromonitoring.

I guess that's what I'm going after. I did plenty of cases with neuromonitoring and 1/2 mac of gas + 50% nitrous gives fine signals. Never used dex in the OR, and just a couple of times in the ICU.

How does dexmeditomidine affect EEG, MEP, SSEP signals?
Does it allow for lower opioid use (which I would be all for)?
Adverse effects other than the brady/hypotension everyone talks about?
Lower doses of propofol?

I'm currently doing TIVAs for cardiac cases requiring circ arrest where we use EEG instead of packing the head in ice. I could believe that volatile anesthetics affect EEG since the cortex is very sensitive (more than motor or sensory tracts).

 

[Mofeen]

Awake crani's with some remi. Smooth.

 

[ssmallz]

we use it for cardiac post bypass and up to ICU

 

[cchoukal]

I guess that's what I'm going after. I did plenty of cases with neuromonitoring and 1/2 mac of gas + 50% nitrous gives fine signals. Never used dex in the OR, and just a couple of times in the ICU.

How does dexmeditomidine affect EEG, MEP, SSEP signals?
Does it allow for lower opioid use (which I would be all for)?
Adverse effects other than the brady/hypotension everyone talks about?
Lower doses of propofol?

I'm currently doing TIVAs for cardiac cases requiring circ arrest where we use EEG instead of packing the head in ice. I could believe that volatile anesthetics affect EEG since the cortex is very sensitive (more than motor or sensory tracts).

It's thought not to affect amplitude or latency of MEP and SSEP signals. Not sure about EEG. There are data in dogs and healthy humans that suggest a drop in CBF w/o a decrease in CMRO2, which might suggest to me that the EEG would be minimally effected.

This issue of lower opiate doses is complicated. There's nothing about its known mechanism that would suggest an analgesic component, but popular lore suggests that it does provide an opiate-sparing effect (I thought maybe someone had looked at this in the bariatric population and found an effect).

The brady and hypo occur (and, paradoxically, you can see transient hyPERtension thought to be due to peripheral a-1 action). The only other thing I've seen is that it hangs around a lot longer than propofol. Using it for MAC cases late in the day will mean you're stuck with sleepy patients in the PACU.

 

[sevoflurane]

We used it a lot in residency as part of a TIVA. Our neuroanesthesia attendings were pretty anal about a pure unadulterated TIVA, especially when there was pre-existing neurological deficits. They wanted neuromonitoring signals to be pure from the very begging of the case... i.e. no inhaled agents whatsoever.

Typically:

Once in the room, crank up the propofol infusion to 150-200mcg/kg/min + Dex/Fentanyl/ketamine gtt's. Titrate a small/slow bolus of prop + Sux for intubation. Once 1/2 loading dose of infusions on board or vitals dictate, turn down propofol to 50-75 mcg/kg/min and add background remi for continued apnea.

Dexmedatomidine def. has an opiod sparing effect (http://bja.oxfordjournals.org/content/102/1/117.full.pdf) as well as propofol sparing affect. It does not affect SSEP's or MEP's. Regarding EEG's: propofol, opiods and inhaled agents will slow EEG's. Being a sedative, dexmedetomidine produces a progressive slowing of the EEG with increased amplitude, decreased frequency sometimes superimposed with sleep spindles. It will also slow your EEG.


What is your end point with EEG? Delta waves at 1-2 cycles/second? Is there evidence that TIVA is better than ICE for brain protection during circ arrest? I don't know, we've always packed the head and made them cold. Are you doing TIVA for the entire case? I guess inhaled agents do increase CBF although they also decrease CMRO2.

Regarding adverse affects: you can see brady/hypotension but rarely, if ever, a real problem that can't be treated easily... unless you are doing pedi hearts:

"The potential for hypotension and systemic vasodilatation due to DEX sympatholitic action carries great concern in children with cyanotic CHD, as it may increase the right-to-left shunt thus worsening hypoxemia. Despite of having significant more patients with cyanotic CHD, the DEX group showed no significant changes in pulse oximetry as compared to MDZ group. Possibly, fentanyl and a high FiO2 might have reduced the pulmonary vascular resistance and offset this deleterious effect. Caution should also be exercised in patients with fixed CO such as severe aortic stenosis, since vasodilatation can lead to low coronary and cerebral perfusion [25]. Due to the scarce experience with DEX in pediatric patients undergoing open heart surgery or in critical state treatment, there are yet no data concerning the DEX effects on the balance between pulmonary and systemic vascular resistance in the single ventricle physiology; we, therefore, excluded children undergoing Norwood, Glenn, and Fontan surgery from our study.
In conclusion, the combination of fentanyl-DEX infusion provided effective anesthesia for pediatric patients undergoing cardiac surgery, when compared to a control group that received fentanyl-midazolam infusion anesthesia. In addition, the fentanyl-DEX group hyperdynamic response to surgical stimuli was blunted. However, a worrisome hypotensive response may ensue and need prompt treatment, particularly in patients already receiving vasodilators."

http://www.hindawi.com/journals/arp/2010/869049.html

http://www.anesthesia-analgesia.org/content/103/1/52.full

Lastly, how's that fellowship going? You are nearly 1/2 way done...

 

[dhb]

Does it allow for lower opioid use (which I would be all for)?

There is this well know guy in Brussels who is allergic to opiates (for his patients). Dex is just making a come back in Europe so his regime is something like 3-5mcg of clonidine, Mag NSAIDS before induction , prop and ketamine for induction , K infusion, if it's a big case lido infusion.
I've not tried it but apparently very stable anesthetic and little need for morphine in the PACU.

 

[fakin' the funk]

Have used it a couple times for MAC cases for patients who I have the suspicion are gonna wyle out during the case (e.g., young men/women w/ lots of anxiety)

 

[fabfive5]

We use it in almost every pedi cardiac case we do. We start it at 0.4-0.7 mcg/kg/HOUR (notice, HOUR, not minute) post-bypass. It's great to extubate the little ones with.

Also, T&A's....right after induction, give 0.5 mcg/kg over 5-10 minutes. If you do this, cut your narcs in half. We usually give 1.5-2 mcg/kg of Fentanyl upfront, but you should lower that to 0.5-1mcg/kg.

You can use the drug in almost any case...but be careful for outpatient procedures. The drug lingers for a while and can prolong discharge.

 

[Masseter Spasm]

In many ways, I feel this is a drug still waiting for an indication for use in the OR. I generally only use it for awake fiberoptic intubations, awake craniotomies, sometimes for neuroanesthesia with evoked potential monitoring, and in patients with significant narcotic tolerance. I do not use it for my pediatric patients, mainly because the average case length is so short. It is not a great medication for ambulatory surgery, unless your PACU nurses feel comfortable monitoring someone for an extended period of time.

 

[proman]

What is your end point with EEG? Delta waves at 1-2 cycles/second? Is there evidence that TIVA is better than ICE for brain protection during circ arrest? I don’t know, we’ve always packed the head and made them cold. Are you doing TIVA for the entire case? I guess inhaled agents do increase CBF although they also decrease CMRO2.

We cool until electrocerebral silence, then a couple of degrees colder. We'll do a TIVA for the whole case, cutting the infusion back as we cool, stopping at 28C, then restarting it when the neuro tech shows EEG activity. It's definitely a more scientific approach to neuroprotection, but I don't think there's good evidence to support it.

Lastly, how's that fellowship going? You are nearly 1/2 way done...

212.44 days to go. Came to work this morning expecting to do a CABG/MVR and found them draping a CABG/double lung. Dropped the guy off in the unit 14 hours later with him needing ECMO. Not fun. Plus, a 2nd year med student kept sitting in my chair (not that I had time to).

 

[sevoflurane]

Nice dude. Awesome experience...straight up! Kinda jealous over here, except for the med student .. I do believe I would have employed him to push some Vec as I swiped my chair back.

Did my share of L/RVADs/BIVADS, Tx, and felt like I did a pedi heart fellowship during residency... but never a CABG/double lung with a twist of ECMO. In my experience, ECMO in adults usually leads to bad outcomes. But geesh... nice case.

What is the sequence of events during a CABG/double lung? (single vessel only?). Do you do the DBLTx then the CABG or... all on bypass? If bypass for both what are pump times like? Clamshell or median sternotomy? Cool case proman. Makes me want to go back and do a fellowship.

 

[proman]

2 vessel CABG first. Did the whole thing off pump. Full clamshell incision. Made for a long day. Mixed venous with Hgb 13, CO 4LPM, FiO2 1.0 = 35-45. We actually have very good results with ECMO in adults. A lot depends on the skill of the perfusionists and doing it early before organ failure starts.

On pump would have been much easier and probably faster but would have been much more coagulopathic. Great learning cases though (especially when the cardiac fellow suggested we add dopamine...attending and I both looked at him with WTF looks)