What is the recommended anesthetic plan for a patient with essential tremor undergoing bilateral deep brain stimulator placement?

Anesthetic Management for Deep Brain Stimulator Placement in a Patient with Essential Tremor

For a patient with essential tremor undergoing bilateral deep brain stimulator placement, the recommended anesthetic plan should include an awake technique with monitored anesthesia care using dexmedetomidine and remifentanil for sedation during the initial and closing phases, while maintaining patient alertness during neurophysiologic testing.

Understanding Deep Brain Stimulation Surgery for Essential Tremor

Deep brain stimulation (DBS) is a highly effective surgical treatment for essential tremor, providing adequate tremor control in approximately 90% of patients 1. The procedure involves:

1. Placement of a stereotactic frame on the patient's head
2. MRI or CT imaging to identify the target (typically the ventral intermediate nucleus of the thalamus)
3. Creation of burr holes in the skull
4. Advancement of microelectrodes to the target
5. Microelectrode recording (MER) to confirm proper positioning
6. Macrostimulation to verify target placement and assess clinical effect
7. Permanent electrode implantation
8. Connection to an implantable pulse generator (usually in a separate procedure)

Anesthetic Considerations

Preoperative Assessment

• Evaluate the severity of essential tremor and its impact on daily functioning
• Review current medications (especially propranolol, primidone, topiramate, or benzodiazepines) 2
• Assess airway and potential challenges for an awake procedure
• Evaluate comorbidities that may affect anesthetic management

Anesthetic Technique

Recommended Approach:

1. Monitored Anesthesia Care (MAC) with Conscious Sedation:

   • This is the prevailing method as it allows for neurophysiologic testing during electrode placement 3
   • Patient must remain cooperative for neurocognitive testing

2. Medications for Sedation:

   • Dexmedetomidine: Primary agent due to its anxiolytic effect and lower risk of delirium 4
     • Start at 0.5-1 mcg/kg/hr without a loading dose
     • Titrate to desired level of sedation
   • Remifentanil: Excellent analgesic with rapid onset and offset 5
     • Initial rate of 0.05-0.1 mcg/kg/min
     • Can be titrated in 0.025 mcg/kg/min increments every 5 minutes

3. Local Anesthesia:

   • Generous infiltration at pin sites and incision areas
   • Typically 0.5% bupivacaine with epinephrine

4. Procedural Phases:

   • Frame Placement and Burr Hole Creation: Moderate sedation with dexmedetomidine and remifentanil
   • Microelectrode Recording: All sedatives discontinued 15-30 minutes prior 3
   • Macrostimulation Testing: Patient fully awake for neurological assessment
   • Electrode Implantation and Closure: Resume sedation

Intraoperative Monitoring

• Standard ASA monitors
• Arterial line if comorbidities warrant
• Neuromuscular blockade monitoring if needed for intubation
• Ensure TOF ratio >0.9 before any neurophysiologic testing 4
• Continuous assessment of level of consciousness and ability to participate

Potential Complications and Management

1. Airway Compromise:

   • Position patient with head elevated 20-30 degrees
   • Avoid oversedation
   • Have emergency airway equipment immediately available

2. Hemodynamic Instability:

   • Dexmedetomidine may cause bradycardia and hypotension
   • Consider lower doses in elderly or those with cardiovascular disease
   • Have vasopressors readily available

3. Seizures:

   • Can occur during electrode testing
   • Have benzodiazepines prepared
   • Be prepared to secure airway if prolonged seizure occurs

4. Patient Discomfort/Agitation:

   • Ensure adequate local anesthesia
   • Consider low-dose propofol (20-30 mg boluses) for breakthrough agitation
   • Communicate frequently with patient

5. Post-procedure Jerking/Twitching:

   • May require PRN benzodiazepines (midazolam 0.01-0.05 mg/kg IV) 6
   • Monitor respiratory status closely after administration

Special Considerations

1. Tremor Management:

   • Continuation of anti-tremor medications until the morning of surgery may be considered
   • Propranolol can be continued perioperatively if no contraindications exist

2. Positioning:

   • Ensure comfortable positioning as procedure may last 4-8 hours
   • Padding of pressure points
   • Consider Foley catheter for prolonged cases

3. Communication:

   • Establish clear communication signals with the patient
   • Explain each step of the procedure to reduce anxiety
   • Maintain a quiet operating room environment during testing phases

Postoperative Care

1. Pain Management:

   • Acetaminophen and low-dose opioids as needed
   • Continue local anesthetic infiltration at incision sites

2. Neurological Monitoring:

   • Frequent neurological assessments
   • Monitor for intracranial hemorrhage (headache, altered mental status)

3. Management of Postoperative Tremor:

   • Resume anti-tremor medications
   • PRN benzodiazepines for severe tremor exacerbation

By following this structured approach, you can provide safe and effective anesthesia for your patient undergoing bilateral deep brain stimulator placement for essential tremor, optimizing both surgical conditions and patient comfort while ensuring accurate electrode placement.