FENTANIL AND REMIFENTANIL

[charliececi]

hi, I have the habit to start the GA by using fentanil 2mcg/kg for the induction and then start the remifentanil infusion. I feel not safe to start with remifentanil ( I had an episode of tremendous stiffness) do you think this practice is correct? Do you have any clinical evidence to support or not this practice ?( I never had problems)
thanks
Simone

[yogenbhatt1]

HI,
Out here in India, we do not have Remifent. We had Sufent some time back, not available again.
I had a very bad experience with Sufent. The elderly patient was given Sufent, the dose was more than we actually wanted to give( Almost twice over).
This patient developed such tight stiffness that we just could not ventilate the patient. It was a frightening experience in an old cardiac patient. We had to paralyse her to ventilate her and  had to give vaso pressors to a  patient posted for spine surgery, where we would like hypotension.

[jafo1964]

Chest wall rigidity is common to all phenopiperidine group of narcotics which includes all the nil's - Fenta, Sufenta, Alfenta and remifenta.
So theorotically similar rigidity can occur with all agents in the susceptible patient. this can be minimized by administration in a diluted form.
Theorotically there is no advantage of starting with fentanyl and switching to remifentanyl.
Thankfully both are mu receptor agonists and can be compatibly  used.
Cases have been documented were chest wall rigidity led to inability to ventilate and also to hypoxic cardiac arrest.
although rare it can be a very dangerous complication.

On the converse when you work with remifentanyl you need to worry about post-op analgesia. As soon as you stop remi( which is done to allow the patient to awaken from anaesthesia) the patient will experience the full pain. To take care of this, longer acting narcotic must be started much before Remi is stopped. This longer acting could be Morphine or Fenta

I have no working experience with Remi but theorotically this seems to be the take on these drugs

regs

[dejswa]

Starting with fentanyl for that reason doesn't make much sense.

I use remi all the time.  Clinically used doses are 'potent' because it is a short acting drug.  Thus, you can get some stiffness, but no different than with any other of the narcotics listed below.

I always mix with propofol and have no problems anyway - 1 mg remi in 50 cc propofol.

Besides, that is what rocuronium or other relaxant is for.

But generally - no relaxant needed with 10cc of the above mixture. (but maybe a little ephedrine).

Regarding end of infusion.  You can add some other narcotic or not.

I find that meperidine is great.  Knocks out shivering which is more common when recovering from remi infusion.

[Pingwin]

1 mg of Remi in Propofol? Are You sure about that dose? Anyway - is it ok to mix these drugs? We use Fentanyl and then - Remifentanyl, You are all right about the stiffness, but You need to give drugs slowly - whenever You push them with a high speed, You get troubles.

[charliececi]

HI what I wanted to say is that in my experience remi is not so easy to titrate in some patients ( generally old people ) I use usually remi alone but in some case I have seen profound ipotension just after intubation and at relatively low dosing (0,25 mcg/kg/min) and in 2 cases (young people) stiffness, that I never see using the old fashioned 100mcg of fenta. In these patients I feel safer by using fenta for induction and then if necessary starting the remi ( or giving more fenta). My question is : is there any support to my practice ( literature or something ) or not? thanks

[LOSKOTA]

Subject: Re: REMIFENTANIL

I tend to do a lot of TIVA (total intravenous anesthesia).  Especially with the prone patient in whom we are monitoring Visual Evoked Potentials (as a study of "postoperative blindness", in progress) because the inhalation agents obliterate the visual evokes.
And then in neuroanesthesia, for open craniotomy (vascular and tumor), as well as in neurointerventional, where patients may be awake/asleep/awake/asleep for functional testing during AVM (arteriovenous malformations) embolizations, and during anterior cervical spine cases, where we monitor the recurrent laryngeal nerve motor evoked responses via an endotracheal tube stimulator....(are you glad you're not in some academic center with all this fuss?)...or in any case, where I need a very quick alteration of depth of analgesia without delayed emergence:
REMIFENTANIL is my "drug of choice".
TIVA induction is 2-5 (usually 5) mg midazolam, 250 ug fentanyl, vecuronium 8 mg, and 100 mg lidocaine prior to propofol titrated to a BIS (Bispectral index)/Aspect EEG (electroencephalogram-graph) monitor of 60 or less (when you can use the BIS)...with remifentanil at 0.2 ug/kg/min started immediately on an IV pump and propofol at 50-200 ug/kg/min to maintain a BIS of 65 or less (burst suppression at higher propofol doses titrated to a BIS of 20 or so and an SR (suppression ratio) of 66 or more on the BIS when burst suppression is indicated).
Where perfusion becomes of concern (at when isn't (is it not) of concern ?), altering the infusion of remifentanil rather than the propofol helps to maintain MAP (mean arterial pressure) and the EEG can help assess functional cerebral perfusion (at least in the frontal lobe site of the BIS monitor placement) as well as ETC02 (endtidal carbon dioxide) can assess  decreased CO (cardiac output) effects in the pulmonary vasculature or decrease urine output, decrease GFR (glomerular filtration rate).
Depending upon the duration of the case and the propofol infusion "load", I usually stop the propofol 20 minutes prior to emergence and run the finish on remifentanil as needed (up to 0.4 ug/kg/min without delays in emergence).  Extubation and emergence can be facilitated with flumazenil (0.5 mg IV) and the endotracheal tube "pulled" upon eye opening and following command ("open your mouth"), regardless of spontanteous ventilation (in the "normal patient") as remifentanil does not seem to have a clinically significant effect on the CO2 response curve following emergence (as does sufentanil or other longer acting opioids/opiates).  The now awake patient will breath on command if for some reason the ETCO2 is below respiratory drive threshold or may be assisted for a few minutes, until spontaneous, regular respiration is demonstrated..
Emergence is rapid and allows for a functional assessment in the OR (operating room) prior to PACU (post anesthesia care unit or recovery room).  The 20 minute emergence time after DC (discontinuing) propofol allows for assessment of hemodynamic responses and the control of BP (blood pressure), usually with bolus nicardipine (0.5 to 1 mg and/or infusion at 5 mg/hr) prn (per registered nurse), or labetalol or esmolol qs (quantity sufficient) to achieve target post operative BP levels.
Of course, whenever I don't need TIVA, I use remifentanil infusion with low dose sevoflurane (0.5 - 1 %) which works very well (in my hands <G>) at 3 l/min flows.
For longer spine instrumentation cases, sufentanil ( 1 mg/kg/hr) replaces remifentanil.
In the past, I have used dexmedetomidine, in combination with all of the above, as an intraoperative infusion.  It works especially well in craniotomies, as emergence is not only rapid, but the postoperative analgesia "window" is approximately 20 minutes.
Once functional assessment is performed in the OR, the rapidly diminishing analgesia can be restored with your anlgesic of choice.

[charliececi]

thanks, very useful post, but do you know any literature support in using remi and fenta together?thanks

[yogenbhatt1]

Dr. Loskota,
Is it that I do not understand the Anaesthesia and the Monitors used by you, or is it that I am growing old already and being in India in private practice that  I am not used to the terms and the monitors. I feel too premitive now.
I must say that you are lickyto be able to practice the way you are practicing. I do envy you.
Regards Dr. Bhatt

[medanes]

I am been using remifentanil and propofol in the last 8 years without seeing a single case of muscle rigidity.I always infused the 2 drugs separately,remif diluted to 20 microgr/ml and starting with 0.1,max 0.2 microgr/kg/min:no boluses of remif ever!(except after intubation).Now that i am practicing only for private patients my caseload is fallen,but I am continuing  with the same approach and intubate without muscle relaxant,following the number presented by my personal CSM monitor(Danmeter),quite similar to the BIs except for differences in the algorythm.INtubation will occur when CSM value is below 60 and blood pressure on  the low side,i.e not before  5-6 min of infusion of both drugs.Propofol is started  at a higher dosage,between 10 and 20 mg/min until the patient(breathing O2) is asleep.Therefore I strongly believe that rigidity occurs only if remif is pushed as a a bolus and in absence of propofol hypnosis.