A patient in our clinic with a long history of depression just underwent vagal nerve stimulator (VNS) implantation. What do I need to know about this therapy?

Dhivya Valluvan, RN, BSN, and Bridget Parsh, EdD, RN, CNS, reply-Prior to the coronavirus pandemic, depression impacted nearly 10% of people in the United States. The rate jumped to 27.8% in early 2020 then to 32.8% in 2021. The latest estimates show that depression affects 1 in every three American adults.1

Although numerous treatments are available for major depressive disorder, patients may be highly resistant (refractory) to many sequential treatment regimens. In 2005, the FDA approved the use of the VNS therapy system for the adjunctive long-term treatment of chronic or recurrent depression for patients aged 18 years or older who are experiencing a major depressive episode and have not had an adequate response to four or more antidepressant treatments.2

The VNS therapy system consists of the implantable pulse generator, the VNS therapy lead, and the external programming system used to change stimulation settings. The lead and the pulse generator make up the implantable portion of the VNS therapy system. Electrical signals are transmitted from the pulse generator to the vagus nerve by the lead. The software allows a healthcare provider (HCP) to identify, read, and change device settings. The pulse generator is surgically placed in the left chest. The lead is then connected to the pulse generator and attached to the left vagus nerve. Patients are provided with magnets that, by placing the magnet over the implanted pulse generator, can deactivate (turn off) programmed stimulation. Programmed stimulation resumes when the magnet is removed. Similar to a cardiac pacemaker, VNS sends regular, mild pulses of electrical energy to the brain via the left vagus nerve to influence the production of neurotransmitters.3 VNS therapy is contraindicated in patients after a bilateral or left cervical vagotomy. Shortwave diathermy, microwave diathermy, or therapeutic ultrasound diathermy should not be used on patients with a VNS therapy system. Heating of the VNS therapy system resulting from diathermy can cause temporary or permanent nerve or tissue or vascular damage, may result in pain or discomfort, loss of vocal cord function, or even possibly death if there is damage to blood vessels.

Diathermy may also damage the VNS therapy system components resulting in loss of therapy, requiring additional surgery for system explantation and replacement. The safety and efficacy of VNS therapy have not been shown for patients with these conditions:

* acute suicidal thinking or behavior

* history of schizophrenia, schizoaffective disorder, or delusional disorders

* history of rapid cycling bipolar disorder

* history of previous therapeutic brain surgery or brain injury

* progressive neurologic diseases other than epilepsy or depression

* cardiac dysrhythmias or other heart abnormalities

* history of dysautonomias

* history of lung diseases or disorders, including shortness of breath and asthma

* history of ulcers (gastric, duodenal, or other)

* history of vasovagal syncope

* only one vagus nerve

* other concurrent forms of brain stimulation

* preexisting hoarseness

VNS therapy can increase the remission rates in people who have depression compared with patients who received the usual treatment methods.4 VNS adjunctive therapy, compared with treatment as usual (such as antidepressant therapy), displayed greater improvements in quality of life.5

Nursing considerations

Postoperatively, patients should be monitored for surgical wound integrity, bleeding, and signs of infection.6 Clinical response to VNS therapy typically occurs between 3 and 12 months, so these patients continue to need monitoring for depressive symptoms after implantation.7 The HCP may advise patients to continue to take their antidepressant medications after beginning VNS therapy. The HCP may also decide to add new medications to the patient's treatment regimen. Teach patients to always follow their HCP's instructions regarding their medications. Teach patients to contact their HCP before undergoing imaging studies, such as MRI, or before having other devices implanted.3 Teach patients to inform all their HCPs that they should not be exposed to diathermy.

Patients should also be taught about common adverse reactions of therapy and encouraged to notify their HCP immediately should any occur. The most common adverse reactions include:

* constantly hoarse voice

* painful or irregular stimulations

* choking, trouble with breathing, trouble with swallowing, or change in heart rate with stimulations

* changes in the level of consciousness (for example, constant drowsiness)

* feeling that the generator may not be stimulating properly or that the VNS therapy system battery is depleted (stops stimulating)

* anything new or unusual that appears related to the stimulation

* the usual feeling during stimulation becomes stronger or weaker

* increased depressive symptoms or suicidal thoughts or behavior

Studies that led to the 2005 approval of VNS therapy for treatment-resistant depression showed that 20%-30% of patients reported significant improvements after 1 year, with half reporting that their symptoms had almost resolved completely.3 Nonetheless, more research is needed on the effects and mechanisms of VNS therapy on depression.7 Although the evidence indicates that VNS therapy decreases symptoms of depression, there is not enough reliable data to provide this therapy to patients who have not explored other options.

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