Vagus nerve stimulation complications

Vagus nerve stimulation complications

The most common side effects associated with Vagus nerve stimulation are hoarsenessthroat pain and coughingCardiac arrhythmia has been reported during lead tests performed during implantation of the device, but few cases during regular treatment.

After implanting vagus nerve electrodes to the cervical vagus nerve, side effects such as voice alterations and dyspnea or missing therapeutic effects are observed at different frequencies. Cervical vagus nerve branching might partly be responsible for these effects.

Adverse events (AEs) are generally associated with implantation or continuous on-off stimulation. Infection is the most serious implantation-associated AE. Bradycardia and asystole have also been described during implantation, as has vocal cord paresis, which can last up to 6 months and depends on surgical skill and experience. The most frequent stimulation-associated AEs include voice alteration, paresthesia, cough, headache, dyspnea, pharyngitis and pain, which may require a decrease in stimulation strength or intermittent or permanent device deactivation. Newer non-invasive VNS delivery systems do not require surgery and permit patient-administered stimulation on demand. These non-invasive VNS systems improve the safety and tolerability of VNS, making it more accessible and facilitating further investigations across a wider range of uses.

VNS battery replacement, revisions, and removals account for almost one-half of all VNS procedures. The findings suggest important long-term expectations for VNS including expected complications, battery life, and other surgical issues. Review of the literature suggests that the first large review of VNS revisions by a single center was done by Couch et al. The findings are important to better characterize long-term surgical expectations of VNS therapy. A significant portion of patients undergoing VNS therapy will eventually require revision 1).

In a retrospective study over an 8-year period, 13 patients underwent revision surgery due to lead failure. Lead failure was classified as either lead intrinsic damage or lead pin disengagement from the generator header. In the X-ray image, Zhou et al., defined an RC ratio that represented the portion of rear lead connector in the header receptacle. It was used to quantitatively evaluate the mechanical failure of the lead-header interface. Optimal procedures to identify and manage lead failure were established.

All 13 patients presented with high lead impedance ≥ 9 kOhms at the time of revision. Seven of ten patients with lead damage presented with increased seizure frequency after a period of seizure remission. In contrast to lead damages occurring relatively late (> 15 months), lead pin disengagement was usually found within the early months after device implantation. A significant association was found between an elevated RC ratio (≥ 35%) and lead pin disengagement. The microsurgical technique permitted the removal or replacement of the lead without adverse effects.

The method of measuring the RC ratio developed in this study is feasible for identifying lead disengagement at the generator level. Lead revision was an effective and safe procedure for patients experiencing lead failure 2).

Main risk of surgery is transient or permanent vocal cord paralysis.

Endotracheal Tube Electrode Neuromonitoring represents a safe adjunctive tool that can help localize the vagus nerve, particularly in the setting of varying anatomy or hazardous dissections. It may help reduce the potential for vagal trunk damage or electrode misplacement and potentially improve clinical outcomes 3).


Couch JD, Gilman AM, Doyle WK. Long-term Expectations of Vagus Nerve Stimulation: A Look at Battery Replacement and Revision Surgery. Neurosurgery. 2016 Jan;78(1):42-6. doi: 10.1227/NEU.0000000000000985. PubMed PMID: 26678088.

Zhou H, Liu Q, Zhao C, Ma J, Ye X, Xu J. Lead failure after vagus nerve stimulation implantation: X-ray examination and revision surgery. World Neurosurg. 2018 Dec 26. pii: S1878-8750(18)32893-6. doi: 10.1016/j.wneu.2018.12.070. [Epub ahead of print] PubMed PMID: 30593965.

Katsevman GA, Josiah DT, LaNeve JE, Bhatia S. Endotracheal Tube Electrode Neuromonitoring for Placement of Vagal Nerve Stimulation for Epilepsy: Intraoperative Stimulation Thresholds. Neurodiagn J. 2022 Feb 28:1-12. doi: 10.1080/21646821.2022.2022911. Epub ahead of print. PMID: 35226831.

High flow nasal cannula

High flow nasal cannula

High-flow nasal cannula (HFNC) therapy is an oxygen supply system capable of delivering up to 100% humidified and heated oxygen at a flow rate of up to 60 liters per minute. All settings are controlled independently, allowing for greater confidence in the delivery of supplemental oxygen as well as better outcomes when used. In addition to greater control over the delivery of FiO2, there are several benefits to using a high-flow nasal cannula.

In adult patients in ICU, HFNO may improve oxygenation and decrease pneumonia rate without affecting the length of ICU stay, intubation or reintubation rate, mortality, and SpO₂ at the end of oxygen therapy 1).

Sixty-five patients who underwent awake craniotomy were randomly assigned to use HFNC with oxygen flow rate at 40 L/min or 60 L/min, or nasopharynx airway (NPA) device in the anesthetic management. Data regarding airway management, intraoperative blood gas analysis, intracranial pressure, gastric antral volume, and adverse events were collected and analyzed.

Results: Patients using HFNC with oxygen flow rate at 40 or 60 L/min presented less airway obstruction and injuries. Patients with HFNC 60 L/min maintained longer awake time than the patients with NPA. While the intraoperative PaO2 and SPO2 were not significantly different between the HFNC and NPA groups, HFNC patients achieved higher PaO2/FiO2 than patients with NPA. There were no differences in Brain Relaxation Score and gastric antral volume among the three groups as well as before and after operation in any of the three groups.

HFNC was safe and effective for the patients during awake craniotomy 2).

Lin YC, Liu YT, Wu ZF, Chan SM. The successful application of high flow nasal cannula for awake craniotomy. J Clin Anesth. 2019 Aug;55:140-141. doi: 10.1016/j.jclinane.2019.01.012. Epub 2019 Jan 15. PMID: 30658329.

3 cases of post-operative PNC who we felt were symptomatic from PNC. With administration of high-flow nasal cannula (HFNC), all patients improved both clinically and radiographically within a few hours, faster than in both anecdotal experience and published trials. Due to its steady FiO2 administration, positive pressure, comfort, and low side-effect profile, HFNC may be the ideal mode of oxygen delivery in PNC. We present a review of the physiology of PNC and the characteristics of several oxygen delivery systems to build a case for HFNC in this disease process 3).

Two cases of awake craniotomy with Monitored anesthesia care (MAC) using high flow nasal cannula (HFNC) and oxygen reserve index (ORi). Gook et al. adjusted the fraction of inspired oxygen of the HFNC according to the ORi level. The patient underwent successful awake craniotomy without a desaturation event or additional airway intervention.

Combined HFNC and ORi monitoring may provide adequate oxygen reserves in patients undergoing awake craniotomy 4).

Super obesity with a body mass index (BMI) >50 kg/m2 presents a challenge for the neuroanesthesiologist during awake craniotomy procedures and poses increased perioperative risk of complications, even vis-à-vis morbid obesity. This article presents a super obese patient (BMI 57 kg/m2) with drug-refractory epilepsy and obstructive sleep apnea who underwent left anterior temporal lobectomy through awake craniotomy to preserve language and memory, using warmed humidified high flow nasal cannula (HFNC) oxygen therapy. Awake craniotomy was facilitated by the use of HFNC, which proved essential to prevent airway collapse by creating continuous positive airway pressure through high flow and facilitated intraoperative neurologic language and memory testing while maintaining adequate oxygenation 5).

A patient who developed HFNC-induced tension pneumocephalus from an unrecognized skull base fracture. Physicians should be cautious when applying HFNC to patients with suspected skull base or paranasal sinus fracture, especially when applying a higher flow rate 6).

Smith SC, Burbridge M, Jaffe R. High Flow Nasal Cannula, A Novel Approach to Airway Management in Awake Craniotomies. J Neurosurg Anesthesiol. 2018 Oct;30(4):382. doi: 10.1097/ANA.0000000000000447. PMID: 28737566.

A 32-year-old man with severe pulmonary arterial hypertension and Eisenmenger syndrome secondary to congenital ventricular septal defects presented for ventriculoperitoneal shunt insertion. Consultation between surgical and anesthesia teams acknowledged the extreme risk of performing this case, but given ongoing symptoms related to increased intracranial pressure from a large third ventricle colloid cyst, the case was deemed urgent. After a full discussion with the patient, including an explanation of anesthetic expectations and perioperative risks, the case was performed under monitored anesthesia care. Anesthetic management included high-flow nasal cannula oxygen with capnography and arterial blood pressure monitoring, dexmedetomidine infusion, boluses of midazolam and ketamine, and local anesthetic infiltration of the cranial and abdominal incisions as well as the catheter track. Hemodynamic support was provided with an epinephrine infusion, small vasopressin boluses, and inhaled nitric oxide. The patient recovered without any significant problems and was discharged home on postoperative day 3 7).


Liang S, Liu Z, Qin Y, Wu Y. The effect of high flow nasal oxygen therapy in intensive care units: a systematic review and meta-analysis. Expert Rev Respir Med. 2021 Oct;15(10):1335-1345. doi: 10.1080/17476348.2021.1937131. Epub 2021 Jun 21. PMID: 34078218.

Yi P, Li Q, Yang Z, Cao L, Hu X, Gu H. High-flow nasal cannula improves clinical efficacy of airway management in patients undergoing awake craniotomy. BMC Anesthesiol. 2020 Jun 27;20(1):156. doi: 10.1186/s12871-020-01073-z. PMID: 32593287; PMCID: PMC7320587.

Siegel JL, Hampton K, Rabinstein AA, McLaughlin D, Diaz-Gomez JL. Oxygen Therapy with High-Flow Nasal Cannula as an Effective Treatment for Perioperative Pneumocephalus: Case Illustrations and Pathophysiological Review. Neurocrit Care. 2018 Dec;29(3):366-373. doi: 10.1007/s12028-017-0464-x. PMID: 28932993.

Gook J, Kwon JH, Kim K, Choi JW, Chung IS, Lee J. Awake craniotomy using a high-flow nasal cannula with oxygen reserve index monitoring – A report of two cases. Anesth Pain Med (Seoul). 2021 Oct;16(4):338-343. doi: 10.17085/apm.21022. Epub 2021 Oct 29. PMID: 35139614.

Banik S, Parrent AG, Noppens RR. Awake craniotomy in a super obese patient using high flow nasal cannula oxygen therapy (HFNC). Anaesthesist. 2019 Nov;68(11):780-783. English. doi: 10.1007/s00101-019-00695-4. Epub 2019 Nov 4. PMID: 31686115.

Chang Y, Kim TG, Chung SY. High-flow Nasal Cannula-induced Tension Pneumocephalus. Indian J Crit Care Med. 2020 Jul;24(7):592-595. doi: 10.5005/jp-journals-10071-23482. PMID: 32963447; PMCID: PMC7482350.

Burbridge MA, Brodt J, Jaffe RA. Ventriculoperitoneal Shunt Insertion Under Monitored Anesthesia Care in a Patient With Severe Pulmonary Hypertension. A A Case Rep. 2016 Jul 15;7(2):27-9. doi: 10.1213/XAA.0000000000000329. PMID: 27224039.


Sevoflurane (Ultane®)

Mildly increases CBF and ICP, and reduces CMRO2. Mild negative inotrope, cardiac output not as well maintained as with isoflurane or desflurane.

Sevoflurane is a sweet-smelling, nonflammable, highly fluorinated methyl isopropyl ether used as an inhalational anesthetic for induction and maintenance of general anesthesia. After desflurane, it is the volatile anesthetic with the fastest onset.

The general inhalation anesthetic sevoflurane can be used for the topical treatment of complicated wounds. It is applied in liquid form and may be used to irrigate the inside of cavities. Sevoflurane also exhibits in vitro antimicrobial activity. Therefore, sevoflurane may be used as an alternative to typical antibiotic or surgical treatment of complicated, localized infections.

Joys et al. from Chandigarh, used digital subtraction angiography to compare the effects of propofol and sevoflurane on the luminal diameter of cerebral vessels and on cerebral vascular mean transit time in patients with aneurysmal subarachnoid hemorrhage (aSAH).

This prospective preliminary study included adult patients with good-grade aSAH scheduled for endovascular coil embolization; patients were randomized to receive propofol or sevoflurane anesthesia during endovascular coiling. The primary outcome was the luminal diameter of 7 cerebral vessel segments measured on the diseased and nondiseased sides of the brain at 3-time points: awake, postinduction of anesthesia, and post coiling. Cerebral transit time was also measured as a surrogate for cerebral blood flow.

Eighteen patients were included in the analysis (9 per group). Baseline and intraoperative parameters were similar between the groups. Propofol increased the diameter of 1 vessel segment at postinduction and post coiling on the diseased side and in 1 segment at post coiling on the nondiseased side of the brain (P<0.05). Sevoflurane increased vessel diameter in 3 segments at postinduction and in 2 segments at post coiling on the diseased side, and in 4 segments at post coiling on the nondiseased side (P<0.05). Cerebral transit time did not change compared with baseline awake state in either group and was not different between the groups.

Sevoflurane has cerebral vasodilating properties compared with propofol in patients with good-grade aneurysmal subarachnoid hemorrhage (aSAH). However, sevoflurane affects cerebral vascular mean transit time comparably to propofol 1).

The case of a 61-year-old male patient who suffered a cranioencephalic trauma 18 years previously is presented. The patient underwent surgeries related to the trauma on numerous occasions. To date, he has suffered various recurrent epidural abscesses, which have been treated with surgical cleaning and antibiotic treatment. In the most recent episode, he presented a frontal epidural abscess 25 mm in diameter with fistulization of the skin. The patient gave written informed consent to be treated with sevoflurane irrigation, and the Pharmacy Service authorized the off-label use. Sevoflurane was applied via a catheter placed inside the cavity during weekly outpatient procedures. The procedures began 8 weeks after the clinically and radiologically verified recovery of the abscess. By avoiding surgery and the associated hospital admission, this novel alternative may prevent patient morbidity and, furthermore, may produce important economic savings.

The treatment of complicated wounds with liquid sevoflurane may be an effective and economically efficient clinical alternative for some patients 2).


Joys S, Panda NB, Ahuja CK, Luthra A, Tripathi M, Mahajan S, Kaloria N, Jain C, Singh N, Regmi S, Jangra K, Chauhan R, Soni SL, Bhagat H. Comparison of Effects of Propofol and Sevoflurane on the Cerebral Vasculature Assessed by Digital Substraction Angiographic Parameters in Patients Treated for Ruptured Cerebral Aneurysm: A Preliminary Study. J Neurosurg Anesthesiol. 2022 Jan 28. doi: 10.1097/ANA.0000000000000833. Epub ahead of print. PMID: 35090162.

Ferrara P, Domingo-Chiva E, Selva-Sevilla C, Campos-García J, Gerónimo-Pardo M. Irrigation with Liquid Sevoflurane and Healing of a Postoperative, Recurrent Epidural Infection: A Potential Cost-Saving Alternative. World Neurosurg. 2016 Jun;90:702.e1-5. doi: 10.1016/j.wneu.2016.02.079. Epub 2016 Feb 24. PubMed PMID: 26924116.