Neuroanesthesia

Thiopental

Thiopental

Thiopental (Pentothal®)

Thiopental in neurosurgery

Thiopental administration has been described as an effective method to prevent postoperative neurological deficits in several animal studies 1) 2) 3) 4) 5)

Here are some key points about the use of thiopental in neurosurgery:

Induction of Anesthesia: Thiopental is often used as an induction agent to rapidly induce anesthesia in patients undergoing neurosurgical procedures. Its rapid onset of action makes it suitable for this purpose.

Sedation and Amnesia: Thiopental induces a state of sedation, amnesia, and unconsciousness, which is important for ensuring that patients do not experience pain or awareness during surgery.

Short Duration: One of the advantages of thiopental is its short duration of action. This allows for precise control of anesthesia depth and a quick recovery once the drug is discontinued.

Neuroprotective Properties: Thiopental has been investigated for its potential neuroprotective properties in the context of neurosurgery. It may help reduce the metabolic demands of the brain during surgery, which could be beneficial in cases where brain tissue needs to be protected.

Control of Intracranial Pressure (ICP): Thiopental can temporarily lower intracranial pressure (ICP), which can be important in neurosurgical procedures involving brain tumors or traumatic brain injury. By reducing ICP, it may provide a safer surgical environment.

Barbiturate Coma: In some cases of severe traumatic brain injury or refractory intracranial hypertension, thiopental has been used to induce a controlled barbiturate coma. This coma state is maintained for a specific duration to protect the brain from further damage and reduce ICP.

Administration: Thiopental is administered intravenously, typically as a rapid bolus injection. The dosage and administration rate are carefully controlled by an anesthesiologist to achieve the desired level of anesthesia.

Side Effects: Like all anesthetic drugs, thiopental can have side effects, including respiratory depression, hypotension (low blood pressure), and a risk of allergic reactions. These side effects are closely monitored during surgery.

Availability: The availability of thiopental may vary by region, and its use may be subject to regulatory restrictions. In some places, it has become less commonly used due to concerns about the misuse and availability of lethal injection

Protocol

May be useful when a rapidly acting barbiturate is needed (e.g. intra-op) or when large doses of pentobarbital are not available. One of many protocols is as follows (note: thiopental has not been as well studied for this indication, but is theoretically similar to pentobarbital):

1. Loading dose: thiopental 5 mg/kg (range: 3–5) IV over 10 minutes → transient burst suppression (< 10 minutes) and blood thiopental levels of 10–30 mcg/ml. Higher doses (≈ 35 mg/kg) have been used in the absence of hypothermia to produce longer-duration burst suppression for cardiopulmonary bypass

2. Follow with continuous infusion of 5 mg/kg/hr (range: 3–5) for 24 hours

3. may need to rebolus with 2.5 mg/kg as needed for ICP control

4. After 24 hours, fat stores become saturated, reduce infusion to 2.5 mg/kg/hr

5. titrate to control ICP or use EEG to monitor for electrocerebral silence

6. “therapeutic” serum level: 6–8.5 mg/dl

Chemically, propofol is not related to barbiturates and has largely replaced sodium thiopental (Pentothal) for induction of anesthesia because recovery from propofol is more rapid and “clear” when compared with thiopental. Propofol is not considered an analgesic, so opioids such as fentanyl may be combined with propofol to alleviate pain.

Thiopental and decompressive craniectomy are important integrated last-tier treatment options in aneurysmal subarachnoid hemorrhage, but careful patient selection is needed due to the risk of saving many patients a state of suffering 6).

A study showed that thiopental was associated with a lower risk of neurological complications after clipping of Unruptured Intracranial Aneurysm 7).

Test and Answers

What is the primary purpose of using Thiopental in neurosurgery? a) Pain relief b) Rapid induction of anesthesia c) Prolonged sedation d) Reducing blood pressure

Why is Thiopental chosen for induction in neurosurgery? a) It provides prolonged anesthesia. b) It has a rapid onset of action. c) It reduces intracranial pressure. d) It is an effective analgesic.

Which of the following is NOT a characteristic of Thiopental? a) Short duration of action b) Neuroprotective properties c) Rapid bolus injection d) Long-lasting sedation

In what situations might Thiopental be used to induce a controlled barbiturate coma? a) Routine neurosurgical procedures b) Cases of severe traumatic brain injury c) During outpatient surgeries d) For postoperative pain management

How is Thiopental typically administered? a) Orally b) Intramuscularly c) Intravenously d) Subcutaneously

What is the recommended therapeutic serum level of Thiopental? a) 1-2 mg/dl b) 6-8.5 mg/dl c) 20-30 mcg/ml d) 50-60 mg/dl

Why has Propofol largely replaced Thiopental for induction of anesthesia? a) Propofol is cheaper. b) Propofol has a shorter duration of action. c) Propofol is more effective at reducing intracranial pressure. d) Propofol has a faster recovery time.

What is a potential risk associated with using Thiopental in neurosurgery? a) Rapid recovery b) Allergic reactions c) Hypertension d) Analgesia

When might Thiopental and decompressive craniectomy be considered as treatment options in aneurysmal subarachnoid hemorrhage? a) As a first-line treatment b) As a second-line treatment c) As a last-tier treatment d) Only in cases of minor bleeding

What did a study suggest about the use of Thiopental in clipping of Unruptured Intracranial Aneurysm? a) It had no impact on neurological complications. b) It increased the risk of complications. c) It was associated with a lower risk of neurological complications. d) It prolonged surgical procedures.

Answers:

b) Rapid induction of anesthesia b) It has a rapid onset of action. d) Long-lasting sedation b) Cases of severe traumatic brain injury c) Intravenously b) 6-8.5 mg/dl d) Propofol has a faster recovery time. b) Allergic reactions c) As a last-tier treatment c) It was associated with a lower risk of neurological complications.

References

1)

Michenfelder J.D. The Interdependency of Cerebral Functional and Metabolic Effects Following Massive Doses of Thiopental in the Dog. Anesthesiology. 1974;41:231–236. doi: 10.1097/00000542-197409000-00004.
2)

Drummond J.C., Cole D.J., Patel P.M., Reynolds L.W. Focal cerebral ischemia during anesthesia with etomidate, isoflurane, or thiopental: A comparison of the extent of cerebral injury. Neurosurgery. 1995;37:742–748. doi: 10.1227/00006123-199510000-00019.
3)

Kofke W.A., Nemoto E.M., Hossmann K.A., Taylor F., Kessler P.D., Stezoski S.W. Brain blood flow and metabolism after global ischemia and post-insult thiopental therapy in monkeys. Stroke. 1979;10:554–560. doi: 10.1161/01.STR.10.5.554.
4)

Musch T.I., Pelligrino D.A., Dempsey J.A. Effects of prolonged N2O and barbiturate anaesthesia on brain metabolism and pH in the dog. Respir. Physiol. 1980;39:121–131. doi: 10.1016/0034-5687(80)90040-7.
5)

Zarchin N., Guggenheimer-Furman E., Meilin S., Ornstein E., Mayevsky A. Thiopental induced cerebral protection during ischemia in gerbils. Brain Res. 1998;780:230–236. doi: 10.1016/S0006-8993(97)01188-8.
6)

Björk S, Hånell A, Ronne-Engström E, Stenwall A, Velle F, Lewén A, Enblad P, Svedung Wettervik T. Thiopental and decompressive craniectomy as last-tier ICP-treatments in aneurysmal subarachnoid hemorrhage: is functional recovery within reach? Neurosurg Rev. 2023 Sep 7;46(1):231. doi: 10.1007/s10143-023-02138-6. PMID: 37676578.
7)

Kim BG, Jeon YT, Han J, Bae YK, Lee SU, Ryu JH, Koo CH. The Neuroprotective Effect of Thiopental on the Postoperative Neurological Complications in Patients Undergoing Surgical Clipping of Unruptured Intracranial Aneurysm: A Retrospective Analysis. J Clin Med. 2021 Mar 12;10(6):1197. doi: 10.3390/jcm10061197. PMID: 33809302; PMCID: PMC7999640.

Propofol

Propofol

Propofol is a potent intravenous (IV) anesthetic agent used for the induction and maintenance of general anesthesia during surgical procedures and medical interventions. It is one of the most widely used and recognized anesthesia drugs in clinical practice. Here are some key points about propofol:

Induction of Anesthesia: Propofol is often used to rapidly induce anesthesia in patients before surgery or medical procedures. It causes rapid loss of consciousness and a state of general anesthesia.

Maintenance of Anesthesia: In addition to induction, propofol can also be used to maintain anesthesia during surgery. Anesthesia providers can adjust the infusion rate to maintain the desired level of anesthesia.

Rapid Onset and Offset: One of the advantages of propofol is its rapid onset of action, typically within seconds after IV administration. It also has a relatively short duration of action, which allows for a quicker recovery when compared to some other anesthetic agents.

Sedation and Amnesia: Propofol induces a state of sedation, amnesia, and unconsciousness. Patients under the influence of propofol do not feel pain or remember the surgical procedure.

Controlled Infusion: Propofol is administered as a controlled infusion through an IV line. The infusion rate is adjusted to maintain the desired level of anesthesia throughout the procedure.

Side Effects: Common side effects of propofol include respiratory depression, hypotension (low blood pressure), and pain at the injection site. These effects are closely monitored during surgery.

Antiemetic Properties: Propofol has antiemetic (anti-nausea and anti-vomiting) properties, making it useful in preventing postoperative nausea and vomiting.

Propofol-Related Infusion Syndrome (PRIS): In rare cases, prolonged and high-dose use of propofol can lead to a condition called PRIS, which may result in metabolic acidosis, heart and kidney dysfunction, and other serious complications. This is why propofol use is carefully monitored, and its dosage is controlled.

Not an Analgesic: It’s important to note that propofol is not an analgesic (pain reliever). It is typically used in conjunction with analgesic medications such as opioids to manage pain during and after surgery.

Intravenous Administration Only: Propofol is administered exclusively through IV injection. It is not available in oral or other forms.

Rapid Recovery: Due to its short duration of action, patients typically wake up quickly and experience a clear-headed recovery after discontinuation of propofol.

Color and Lipid Emulsion: Propofol is known for its milky white appearance, and it is formulated as a lipid emulsion. This unique formulation contributes to its rapid onset and offset of action.

Special Considerations: Dosage and administration of propofol are tailored to the patient’s age, weight, medical condition, and the type of surgery being performed.

see Agents generally used for induction.

Propofol in neurosurgery

Reduces cerebral metabolism, CBF and ICP. Has been described for cerebral protection and for sedation. Short half-life permits rapid awakening which may be useful for awake craniotomy. Not analgesic.

The exact mechanism of action unknown. Short half-life with no active metabolites. May be used for induction and as a continuous infusion during total intravenous anesthesia (TIVA). It causes a dose-dependent decrease in mean arterial blood pressure (MAP) and ICP.

It is more rapidly cleared than and has largely replaced thiopental.

Dexmedetomidine (Precedex®). Alpha 2 adrenergic receptor agonist, used for control of hypertension postoperatively, as well as for its sedating qualities during awake craniotomy either alone or in conjunction with propofol.

Propofol has a mild effect on evoked potential (EP): total anesthesia with propofol causes less EP depression than inhalational agents at the same depth of anesthesia 1).

Propofol (INN, marketed as Diprivan by Fresenius Kabi) is a short-acting, intravenously administered hypnotic/amnestic agent. Its uses include the induction and maintenance of general anesthesia, sedation for mechanically ventilated adults, and procedural sedation. Propofol is also commonly used in veterinary medicine. It is approved for use in more than 50 countries, and generic versions are available.

Chemically, propofol is not related to barbiturates and has largely replaced sodium thiopental (Pentothal) for induction of anesthesia because recovery from propofol is more rapid and “clear” when compared with thiopental. Propofol is not considered an analgesic, so opioids such as fentanyl may be combined with propofol to alleviate pain.

Propofol has been referred to as milk of amnesia (a play on words of milk of magnesia), because of the milk-like appearance of its intravenous preparation.

It is on the World Health Organization’s List of Essential Medicines, the most important medications needed in a health system.

Level II: propofol may control ICP after several hours of dosing, but it does not improve mortality or 6-month outcomes. ✖ Caution: high-dose propofol (total dose > 100 mg/kg for > 48 hrs) can cause significant morbidity (see propofol infusion syndrome).

℞: 0.5 mg/kg test dose, then 20–75 mcg/kg/min infusion. Increase by 5–10 mcg/kg/min q 5–10 minutes PRN ICP control (do not exceed 83 mcg/kg/min = 5 mg/kg/hr).

Side effects include propofol infusion syndrome. Use with caution at doses > 5 mg/kg/hr or at any dose for > 48 hrs.

Propofol, an established hypnotic anesthetic agent, has been shown to ameliorate neuronal injury when given after injury in a number of experimental brain studies. We tested the hypothesis that propofol pretreatment confers neuroprotection against SBI and will reduce cerebral edema formation and neurobehavioral deficits in our rat population. Sprague-Dawley rats were treated with low- and high-dose propofol 30 min before SBI. At 24 h post-injury, brain water content and neurobehavioral assessment was conducted based on previously established models. In vehicle-treated rats, SBI resulted in significant cerebral edema and higher neurological deficit scores compared with sham-operated rats. Low- or high-dose propofol therapy neither reduced cerebral edema nor improved neurologic function. The results suggest that propofol pretreatment fails to provide neuroprotection in SBI rats. However, it is possible that an SBI model with less magnitude of injury or that propofol re-dosing, given the short-acting pharmacokinetic property of propofol, may be needed to provide definitive conclusions 2).

Propofol concentration needed for induction of unconsciousness in 50% of patients is reduced in Parkinson’s Disease patients 3).

Complications

Propofol infusion syndrome.

Case series

Malekmohammadi et al. from the Department of Neurosurgery, University of California, Los Angeles, collected local field potentials (LFPs) in 12 awake and anesthetized PD patients undergoing DBS implantation. Spectral power of β (13-35 Hz) and high-frequency oscillations (HFOs: 200-300 Hz) was compared across the pallidum.

Propofol suppressed GPi power by > 20 Hz while increasing power at lower frequencies. A similar power shift was observed in GPe; however, power in the high β range (20-35 Hz) increased with propofol. Before anesthesia both β and HFO activity were significantly greater at the GPi (χ2 = 20.63 and χ2 = 48.81, p < 0.0001). However, during anesthesia, we found no significant difference across the pallidum (χ2 = 0.47, p = 0.79, and χ2 = 4.11, p = 0.12).

GPi and GPe are distinguishable using LFP spectral profiles in the awake condition. Propofol obliterates this spectral differentiation. Therefore, LFP spectra cannot be relied upon in the propofol-anesthetized state for functional mapping during DBS implantation 4).

We analyzed 231 neurosurgery patients. In all patients, propofol was used for standard anesthesia induction. Patient demographics, medical histories, fasting duration, percentage weight loss, baseline blood pressure, and PPV during normal tidal volume breathing and that during forced inspiratory breathing (PPVfi) were recorded. Hemodynamic changes within 10 minutes of intubation were observed. Patients developing hypotension and severe hypotension were determined; lowest mean arterial pressure (MAP) and systolic arterial pressure (SAP) values were recorded, and their differences relative to baseline values were calculated. RESULTS: The incidence of hypotension was 18.6%. Both percentage weight loss and PPVfi were correlated with the changes in MAP and SAP. A PPVfi>14 identified all observed hypotensive episodes with 86% sensitivity and 86.2% specificity, whereas percentage weight loss >1.75% identified all observed hypotensive episodes with 81.4% sensitivity and 70.7% specificity. Furthermore, PPVfi>16.5 identified severe hypotension with 85% sensitivity and 90.5% specificity, whereas percentage weight loss >1.95% identified severe hypotension with 85% sensitivity and 73% specificity. CONCLUSIONS: Percentage weight loss and PPVfi are good predictors of hypotension after anesthesia induction and, thus, may allow anesthesiologists to adopt preventative measures and ensure safer anesthesia induction 5).

Case reports

Acute psychosis following propofol in a patient with Parkinson’s disease: effects of a GABA–dopamine imbalance 6).

Test and answers

What is the primary use of Propofol in clinical practice? a) Pain relief b) Induction and maintenance of general anesthesia c) Treatment of hypertension d) Treatment of epilepsy

What is the advantage of using Propofol for induction of anesthesia? a) It provides prolonged anesthesia. b) It has a slow onset of action. c) It causes rapid loss of consciousness. d) It is available in oral form.

How does Propofol compare to some other anesthetic agents in terms of its duration of action? a) It has a longer duration of action. b) It has a shorter duration of action. c) It has no duration of action. d) Its duration of action depends on the patient’s age.

What state does Propofol induce in patients during surgery? a) Euphoria b) Sedation and amnesia c) Hyperactivity d) Increased pain perception

How is Propofol administered during surgery? a) Orally b) Intramuscularly c) Subcutaneously d) As a controlled IV infusion

What is one of the common side effects of Propofol during surgery? a) Increased heart rate b) Hypertension (high blood pressure) c) Respiratory depression d) Elevated body temperature

What property of Propofol makes it useful in preventing postoperative nausea and vomiting? a) Analgesic effect b) Antidepressant effect c) Antiemetic properties d) Anticoagulant effect

What rare condition can occur with prolonged and high-dose use of Propofol? a) Hypothermia b) Propofol overdose c) Propofol-related infusion syndrome (PRIS) d) Propofol addiction

Which of the following statements about Propofol is true? a) It is commonly used as a standalone analgesic. b) It is available in various forms, including oral tablets. c) It is administered exclusively through IV injection. d) It is primarily used as an anticoagulant.

Why is Propofol known as the “milk of amnesia”? a) It has a white color. b) It is derived from milk. c) It tastes like milk. d) It causes amnesia-like effects.

Answers:

b) Induction and maintenance of general anesthesia c) It causes rapid loss of consciousness. b) It has a shorter duration of action. b) Sedation and amnesia d) As a controlled IV infusion c) Respiratory depression c) Antiemetic properties c) Propofol-related infusion syndrome (PRIS) c) It is administered exclusively through IV injection. a) It has a white color.

1)

Liu EH, Wong HK, Chia CP, et al. Effects of isoflurane and propofol on cortical somatosensory evoked potentials during comparable depth of anaesthesia as guided by bispectral index. Br J Anaesth. 2005; 94:193–197
2)

Pakkianathan C, Benggon M, Khatibi NH, Chen H, Marcantonio S, Applegate R 2nd, Tang J, Zhang J. Propofol Pretreatment Fails to Provide Neuroprotection Following a Surgically Induced Brain Injury Rat Model. Acta Neurochir Suppl. 2016;121:323-7. doi: 10.1007/978-3-319-18497-5_56. PubMed PMID: 26463969.
3)

Xu XP, Yu XY, Wu X, Hu XW, Chen JC, Li JB, Wang JF, Deng XM. Propofol Requirement for Induction of Unconsciousness Is Reduced in Patients with Parkinson’s Disease: A Case Control Study. Biomed Res Int. 2015;2015:953729. Epub 2015 Oct 1. PubMed PMID: 26495319.
4)

Malekmohammadi M, Sparks H, AuYong N, Hudson A, Pouratian N. Propofol Anesthesia Precludes LFP-Based Functional Mapping of Pallidum during DBS Implantation. Stereotact Funct Neurosurg. 2018 Sep 7:1-10. doi: 10.1159/000492231. [Epub ahead of print] PubMed PMID: 30196280.
5)

Ali A, Altiparmak O, Tetik A, Altun D, Sivrikoz N, Buget M, Bolsoy S, Yaman N, Akinci IO. Pulse Pressure Variation and Weight-Loss Percentage Predict Hypotension After Anesthesia Induction in Neurosurgery Patients: A Prospective, Observational, Blinded Study. J Neurosurg Anesthesiol. 2016 Jun 17. [Epub ahead of print] PubMed PMID: 27322092.
6)

Vinckier F, Gaillard R, Taylor G, Murray GK, Plaze M, Bourdillon P, Perin-Dureau F. Acute psychosis following propofol in a patient with Parkinson’s disease: effects of a GABA-dopamine imbalance. Psychiatry Clin Neurosci. 2022 Mar 29. doi: 10.1111/pcn.13360. Epub ahead of print. PMID: 35352434.

Test your knowledge about awake surgery for glioma systematic reviews

What was the median age of patients analyzed in the systematic review of awake surgery for glioma resection during pregnancy?

a) 25 years

b) 30.5 years

c) 35 years

d) 40 years

In the same review, what percentage of patients underwent awake surgery in the third trimester of pregnancy?

a) 25%

b) 50%

c) 67%

d) 83%

Which medications were used to achieve conscious sedation in 67% of the cases during awake surgery?

a) Remifentanil and propofol

b) Morphine and ketamine

c) Diazepam and midazolam

d) Aspirin and ibuprofen

What is the main conclusion of the systematic review of awake surgery for glioma resection during pregnancy?

a) Awake surgery is not a suitable option during pregnancy.

b) Awake surgery is safe during pregnancy with no maternal-fetal complications.

c) The long-term effects of awake surgery during pregnancy are well-determined.

d) Awake surgery should only be performed in the first trimester of pregnancy.

What parameters were evaluated in the systematic review regarding repeated surgery in awake conditions for diffuse glioma patients?

a) Blood pressure, heart rate, and oxygen saturation

b) Return to work, neurocognitive disorders, and epileptic seizures

c) Tumor size, location, and histology

d) Surgical complications, anesthesia duration, and hospital stay

How many patients returned to active socio-professional life after repeated surgery in the systematic review on repeated awake surgeries?

a) 15%

b) 41%

c) 78%

d) 85%

According to the systematic review on stress, anxiety, and depression in AC patients, what percentage of studies concluded that awake craniotomy does not increase stress, anxiety, and/or depression?

a) 10%

b) 33.3%

c) 66.7%

d) 95.8%

What was the most common psychological outcome evaluated in the studies included in the review on stress, anxiety, and depression in AC patients?

a) Mood swings

b) Neurocognitive disorders

c) Anxiety

d) Memory loss

In the systematic review on speech and language errors during awake craniotomy with DES, what percentage of errors were reported at the subcortical level?

a) 10%

b) 20%

c) 40%

d) 60%

According to the meta-analysis mentioned in the last paragraph, what is the main benefit associated with awake craniotomy with Electrostimulation during glioma resection?

a) Faster recovery of motor skills

b) Reduced surgical complications

c) Lower risk of long-term neurological and language deficits

d) Shorter anesthesia duration

Answers:

b) 30.5 years
b) 50%
a) Remifentanil and propofol
b) Awake surgery is safe during pregnancy with no maternal-fetal complications.
b) Return to work, neurocognitive disorders, and epileptic seizures
b) 41%
d) 95.8%
c) Anxiety
c) 40%
c) Lower risk of long-term neurological and language deficits

See Literature

Vagus nerve stimulation complications

Vagus nerve stimulation complications

The most common side effects associated with Vagus nerve stimulation are hoarseness, throat pain and coughing. Cardiac 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).

Vocal cord paralysis

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).

1)

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.
2)

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.
3)

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).

Case series

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).

Case reports

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).

1)

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.
2)

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.
3)

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.
4)

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.
5)

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.
6)

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.
7)

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

Sevoflurane (Ultane®)

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

Indications

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.

Prospective preliminary studies

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).

Case reports

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).

1)

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.
2)

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.