Neuroanesthesiology Protocols HBMD.org

Other

TGN RFA Ablation

All protocols

Trigeminal Nerve Radiofrequency Ablation (RFA) - Awake with Sedation

Background: Trigeminal Neuralgia

Trigeminal neuralgia is a chronic pain condition characterized by recurrent episodes of electric shock-like pain of the face, typically the forehead, cheek, and/or jaw. It is usually unilateral, but can be bilateral. The trigeminal nerve has three divisions; any or all of them may be affected by TG neuralgia:

  • Ophthalmic (V1): sensory to eye, upper eyelid, and forehead

  • Maxillary (V2): Lower eyelid, cheek, nostril, upper lip, and upper gingivae

  • Mandibular (V3): sensation to lower lip, lower gingivae, jaw; motor to muscles of mastication

Pain associated with trigeminal neuralgia can be profoundly debilitating and, in severe cases, may impair speech due to pain with jaw movement and lead to malnutrition secondary to pain with chewing. Initial management typically includes carbamazepine or oxcarbazepine (newer formula of carbamazepine), along with adjunctive agents such as gabapentin, baclofen, and opioids. For patients with refractory symptoms despite medical therapy, trigeminal nerve ablation may be considered.

The Procedure:

During the procedure, the patient will need to be asleep for the painful parts of the surgery, but fully awake and able to participate during other portions of the surgery (this can be quite challenging from an anesthetic standpoint!). Once the patient is brought into the room, high flow nasal cannula oxygen and monitors should be connected, and a light-to-moderate sedation should be initiated with short acting anesthetics (ex prop + remi).    At this point, the procedure can be broken down into five steps:

  1. Initial X-rays: The surgical team will obtain a series of xrays to help plan out their needle trajectory.

  2. Local Anesthetic + Needle Placement: The surgical team may request a deeper level of sedation for this portion. They will inject local anesthetic into the cheek, and insert the RFA needle. X-ray will be used to confirm needle positioning - this can take multiple attempts and can be quite painful, so be prepared to bolus short acting medications (such as remi) and titrate the infusions during this time. Once the surgical team is confident about their needle placement, they will ask you to wake up the patient.

  3. Patient confirmation of needle Positioning: Once the patient is fully awake, neuromonitoring will lightly stimulate the needle and the patient will be asked to describe where they feel tingling triggered by the needle. It is imperative that the patient be fully awake and able to participate during this time. The goal is to have the needle placed in such a way that the patient is able to feel tingling in the same distribution as their TG neuralgia pain.

  4. RF Ablation: Once the surgical team is confident in their needle placement, they will ask for the patient to be deeply sedated for the radiofrequency ablation itself. The ablation takes about one minute and is extremely painful, so we typically use a large remifentanil bolus (ex ~1mcg/kg). The patient has a high risk of becoming apneic during the ablation (hence the HFNC); however, manipulation of the head and jaw should be avoided as it will require the ablation to be stopped and the needle to be repositioned. As always, if the patient becomes unstable, resuscitation should take priority. The surgical team may elect to do an additional ablation(s) after the first one is completed.

  5. Post-ablation patient confirmation of treatment success: Once the ablation is done, the sedation will be stopped and the patient awoken for a neuro exam of the face. Again, the patient needs to be able to fully participate to ensure that the procedure was successful. If successful, the procedure will be done and the patient transported to PACU. If unsuccessful, the surgical team may elect to repeat the ablation.

From an anesthetic standpoint, these cases can be quite difficult. Healthy patients with a normal BMI can typically tolerate the apneic periods with HFNC; however, larger patients with sleep apnea can desaturate quickly. Unfortunately, the nature of the case prevents placement of an ETT or LMA; a nasal trumpet can be helpful in these instances. Concerns should be addressed with the surgical team preoperatively or during time out and communication during the procedure is essential. Once the ablation is done, it is not uncommon for larger patients to require some airway support (chin lift, jaw thrust, mask ventilation, etc). The surgical team is aware of this and will make room for you.

Preop Management:

  • It is essential that patients understand they will be fully awake for portions of this surgery and that there is a potential to feel pain (many are unaware of this when they arrive and many are pain-averse chronic pain patients). Be reassuring, but set appropriate expectations.

  • Preop labs:

    • No specific labs necessary for these cases, so order on a patient-dependent basis.

    • T+S & Confirmation: typically not necessary (patient-dependent)

    • On day of surgery, consider: POCT gluc, HCG

  • Preop meds:

    • Patients will likely be on pain meds for TG neuralgia, including any combination of carbamazepine or oxcarbazepine, gabapentin, baclofen, opioids, etc. Review current opioid doses to aid with dosing pain meds intraop.

    • Consider: preop tylenol, PONV meds (emend)

    • Preop Versed?: We usually avoid versed in neuro patients; however, some patients may benefit from preop versed for these procedures. This must be weighed with the need to be fully awake and able to participate during the surgery. If you feel the patient needs an anxiolytic, discuss with your attending prior to administering anything, and consider starting with a low dose and titrating to effect.

  • Cardiac History: These surgeries can be painful - ensure your patient is stable enough from a cardiac standpoint to tolerate tachycardia and hypertension from pain.

  • Preop neuro exam - document any abnormalities. It is helpful to know which side of the face is affected by the TG neuralgia (right versus left), and which divisions of the TG nerve (see background notes above for a refresher).

Intraoperative Management:

Monitors: Standard ASA. No need for art line, sed line, or TOF.

  • Turn on the respiratory rate monitor on the Philips screen and ensure your EKG leads are properly placed across the chest so the monitor can detect the RR. ETCO2 can be difficult to monitor with HFNC, so this will help monitor the patient’s breathing.

Access:

  • 1xPIV: One well-functioning IV is sufficient. Preferably an 18-20G, but a 22G is ok.

  • No foley: these cases typically last <1h

Airway:

  • High flow nasal cannula (HFNC) is essential for these cases. The strap for the HFNC should be placed around the head and properly fitted to get the full benefit from the HFNC - you may need to tape it high on the face on the surgical side to avoid the needle entry zone. Ask the tech to set up the HFNC early (it takes time). You will have to fiddle with the ETCO2 detector (keep it as close as possible to the nose/mouth, depending how your patient breathes).

  • Have emergency airway equipment at hand (ie on the anesthesia machine), including LMAs, nasal trumpet, oral airway, and ETT/laryngoscope blade/stylet/10ml Syringe, etc.

  • Ensure that the circuit is set up, can easily be grabbed, and reaches the patient.

Time out + additional meds:

  • Discuss any airway/sleep apnea or other concerns.

  • Confirm antibiotics: typically cefazolin

Induction, Maintenance, Pain Control:

  • Remi: The main anesthetic for these cases is remifentanil because it allows us to treat the pain of needle placement and ablation, and wake the patient up in a timely manner.

    • Have 2-4 x 10ml syringes with 10mcg/ml of remi prepared. You will need these to quickly bolus and titrate the remi. Do not plan to bolus off the pump - it will not be fast enough.

    • Also have a remi infusion set up (often started around 0.02-0.05mcg/kg/min).

    • Helpful tip: We typically use <1mg of remi total, so one vial should be sufficient

  • Propofol: Have an infusion and a couple of 10ml bolus syringes prepared. Prop is commonly run as a sedative during needle placement and ablation. Consider a small bolus with the remi during the ablation, but keep in mind that you will want your patient awake soon.

  • +/- Precedex: Consider having some precedex ready in case needed. Small doses can be helpful as an anxiolytic; do not over-sedate the patient though.

  • +/- fentanyl, versed: Discuss with your attending first. Sometimes helpful, but patient-dependent.

  • A helpful hint from the protocol author regarding remi: Historically, we used a mix of remi, prop, precedex, etc, but I have recently transitioned to using remi alone and have found it superior to a mixed anesthetic approach. Pain is the primary intraoperative issue for these patients, and using remi as the sole infusion allows higher remi dosing with better analgesia, fewer apnea/hypoxia events, and rapid wake-ups. I typically run remi at 0.05–1.0 mcg/kg/min when it is the sole agent, with boluses during the ablation remaining the same (~1 mcg/kg, titrated to effect).

BP management:

  • Have both norepi (8mcg/ml) and nicardipine boluses (200mcg/ml) available.

IV Fluids:

  • Plasmalyte or LR can be used for these procedures.

Postop Management:

  • Most patients go to PACU and are typically discharged the same day if they came in as outpatients.

  • PACU orders: standard PACU orders are typically sufficient.

    • Do not order meperidine for neuro patients going to PACU

  • Handoff to PACU or ICU must include a description of the patient’s baseline neurological status (this will help prevent an unnecessary code stroke).