Association of Anaethetists: Management of vagus nerve stimulation therapy in the peri-operative period

Question 1

Indications for vagus nerve stimulator therapy

Answer 1

• Drug-resistant epilepsy
• Major depressive disorder
• Areas of research: chronic pain, anxiety, migraines

Question 2

Mechanism of action of vagus nerve stimulators

Answer 2

Unclear
- electrical stimulation of the left cervical vagus nerve
- stimulates nuclei in the brainstem (locus coeruleus and raphe nucleus) to produce serotonin, noradrenaline, dopamine and GABA
- stimulates the limbic system (amygdala and hippocampus) and modulates the pre-frontal cortex
- Modulates the release of inflammatory cytokines and alters the permeability of the BBB

Question 3

Perioperative risks of vagus nerve stimulators

Answer 3

Airway obstruction and pulmonary aspiration
- Can stimulate the recurrent laryngeal nerve on the left and cause left vocal cord adduction
- Therefore intubation is recommended can get partial laryngospasm when using a SAD

Bradyarrhythmias, hypotension and asystole
- The left vagus nerve is used to reduce the risk of this as the right supplies the SA node but it is still a possibility

Diathermy, defibrillation and electromagnetic interference
- Damage and disable the device

Question 4

Pre-operative assessment for patients with vagal nerve stimulators

Answer 4

• Input from neurology
• VNS information- last check, position of battery and pulse generator. If not available CXR to check position
• Response to VNS
• Any evidence of vocal cord issues- hoarse voice, sore throat, OSA symptoms
• Medical history often focussing on seizures, medications and rescue plans
• Ensure compliance with AEDS and taken on day of surgery
• FBC, U&Es and LFTs due to AEDS
• ECG- AEDS

Question 5

Intra-operative considerations for patients with vagal nerve stimulators

Answer 5

• Device should be deactivated with all stimulating currents programmed to 0mA
• In the emergency setting a magnet can be taped over the device for the duration of surgery
• The device should be reactivated as soon as possible and interrogated
• Intubation is recommended due to risk of vocal cord adduction
• Vigilance for the possibility of bradycardia, asystole
• Avoid monopolar diathermy as this may heat the device and cause tissue damage
• Cardioversion can damage the device and vagal nerve, a magnet should be placed if time allows

Question 6

Risk of MRI and Vagal Nerve Stimulators

Answer 6

VNS are MR conditional (pose no hazards in an MRI environment with specific conditions)
- Heating effects on VNS
- Inadvertent device rest
- Delivery of vagal nerve stimulation
- Image artefact
- Device damage