The sedation can then again be increased for closure. The advantages of this technique are the avoidance of airway manipulation and its inherent risks. Some studies state that the level of sedation during the crucial stage of intra-operative cortical mapping is less and others have shown advantages in avoiding a general anaesthetic, for example, decreased nausea and vomiting.
Currently, within the UK, the most commonly used drugs in this setting are propofol and remifentanil target-controlled infusions. There is also some use of clonidine infusions. Recently, dexmedetomidine has become available for use in the UK, and is routinely used in our institution. It has anaesthetic sparing properties and does not have any effect on intracranial pressure.
However, it can cause hypotension and bradycardia, which are dose-dependent.
Dexmedetomidine is usually used as a sole agent and administered intravenously. Many studies document the advantageous use of dexmedetomidine for awake craniotomies. A loading dose of 0. This technique involves induction of general anaesthesia and control of the airway with either a supraglottic device or intubation. When neurocognitive testing and intra-operative mapping needs to commence, the anaesthetic drugs are either reduced or stopped and the airway device is removed, when the patient has regained upper airway reflexes and it is safe to do so.
Once resection of the lesion is complete, general anaesthesia can be re-introduced and with re-insertion of the airway device. The advantages of this technique include the ability to control ventilation and therefore control carbon dioxide concentrations and prevent airway obstruction and hypoventilation. It also facilitates greater depth of anaesthesia during the painful parts of the surgery. In the UK, propofol and remifentanil TCI are the most common, followed by the use of a volatile anaesthetic and a remifentanil infusion. Controlled ventilation is most commonly used after the airway device is inserted, with the advantages of preventing hypoventilation and hypercapnia.
Neuromuscular blocking agents can be used. Patient tolerance of an awake craniotomy relies on effective analgesia of the surgical field, and cannot rely on sedation or anaesthesia alone, especially as these are at a minimal level during neurocognitive testing and intra-operative mapping. A scalp block also provides haemodynamic stability and decreases the stress response to painful stimuli. Occasionally, when sedation or general anaesthesia is not used, it is the scalp block that is used as the sole technique. Most anaesthetists will insert a bilateral scalp block before pinning of the head in Mayfield Pins.
Occasionally, a scalp block is not inserted and there is a reliance on the surgeon's local anaesthetic infiltration. The total local anaesthetic available to use with and without epinephrine must be calculated for individual patients. Studies have shown that the increase in local anaesthetic levels of levobupivicaine and ropivicaine are rapid compared with other regional blocks and similar in all patients.
Despite the rapid increase of plasma levels, there were no signs of cardiovascular or central nervous system toxicity. The amount and type of local anaesthetic must be recorded and communicated with the surgeon as they will often supplement the scalp block with further infiltration of the skin, temporalis fascia and dura mater. The brain tissue is not painful to stimuli. Bupivacaine, levobupivacaine, and ropivacaine of varying concentrations with and without epinephrine have been described for use in a scalp block.
The addition of epinephrine, usually , increases the total amount of local anaesthetic that can be used, decreases localized bleeding, and maximizes the duration. However, systemic absorption may cause tachycardia and hypertension and intra-arterial injection into the superficial temporal artery is possible when blocking the auriculotemporal nerve. The scalp block technique includes infiltrating local anaesthetic to seven nerves on either side.
This is an anatomical block, and not just a ring block. A ring block will require large volumes of local anaesthetic, increases the risk of toxicity, and will not provide anaesthesia deep to the temporalis fascia. This block may be inserted with the patient sedated or after the induction of anaesthesia. The skin is cleaned using either chlorhexidine or betadine. The amount inserted at each site will be dependent upon the concentration and local anaesthetic used and whether it is mixed with epinephrine.
Using sterile gloves and a 23 gauge needle, the local anaesthetic is infiltrated into the following sites:. Scalp innervation. Reproduced from Costello and Cormack 4 with permission from Elsevier and the authors. It innervates the forehead, anterior part of the scalp, and top part of the head.
Palpate the supraorbital notch and insert needle perpendicularly and inject. It innervates the forehead and anterior part of the scalp. Just medial to the supraorbital nerve injection site, above the eyebrow line, inject local anaesthetic to spread the block medially.
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It innervates a small area of the forehead and the temporal area. The nerve passes through the temporalis muscle to enter the temporalis fascia. Therefore, the local anaesthetic needs to be infiltrated deep and superficial to the temporalis muscle. Infiltration begins at the lateral edge of the supraorbital margin and continues to the distal aspect of the zygomatic arch. It innervates the temporal areas, lower lip, lower face, auricle, and the scalp above the auricle.
Inject local anaesthetic about 1 cm anterior to the auricle, above the level of the temporomandibular joint. This nerve crosses over the root of the zygomatic process of the temporal bone and lies deep to the superficial temporal artery, which should be palpated to avoid intra-arterial injection. It ascends along the posterior border of the sternocleidomastoid muscle. It innervates the scalp in the lateral area of the head posterior to the auricle. Infiltrate local anaesthetic subcutaneously behind the auricle starting from the top-down to the auricular lobule and then continue to infiltrate along the superior nuchal line to the greater occipital nerve.
It arises from the first and second cervical vertebrae. It ascends to innervate the skin along the posterior part of the scalp. It can also innervate the scalp at the top of the head and over the auricle. It is located by initially palpating the occipital artery, which is found about 3—4 cm lateral to the external occipital protuberance along the superior nuchal line and then inject the local anaesthetic, medial to the occipital artery.
It is the largest of the ascending branches and emerges around the posterior border of the sternocleidomastoid muscle. It divides into an anterior and a posterior branch and provides sensory innervation for the skin over the parotid gland and mastoid process and the auricle. Inject the local anaesthetic about 2 cm posterior to the auricle, at the level of the tragus. The patient is awoken for this stage and time is needed to allow the patient to adjust to the environment to ensure that they are ready for clinical evaluation. A calm, quiet environment is required for patient awakening.
It is upon emergence that several complications can occur, for example, pain from either the pins or discomfort from the prolonged immobility, agitation or nausea, and vomiting. It is important to address these issues quickly and effectively as it can lead to poor surgical conditions.
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Cortical stimulation, also known as cortical or brain mapping, aims to localize the eloquent areas of the brain through direct electrical stimulation of the cerebral cortex by electrodes. These areas are those involved in speech, language, and motor abilities.
Specifically, the Broca's area is needed for speech production and language processing and the Wernicke's area is used for language comprehension. It is also important to identify the motor and sensory cortex. Seizures, either focal or generalized, are most likely to occur during cortical mapping. They are treated by irrigating the brain tissue with ice-cold saline. They usually cease with this treatment alone, but occasionally benzodiazepines, anti-epileptic drugs, or re-sedation with airway control are required. An emergency plan for airway control has to be in place at all times and this can be challenging as the patient's head is fixed in head pins and often away from the ventilator.
The options include the insertion of an LMA which may be easier than oro-tracheal intubation. Awake craniotomy is generally a well-tolerated procedure with a low rate of conversion to general anaesthesia and a low rate of complications. One of the most frequent complications is patient intolerance of the procedure, often because of the urinary catheter or prolonged positioning and intra-operative seizures.
Once resection is completed, the patient can be re-sedated or re-anaesthetized with re-insertion of the airway device, even if in the lateral position. Closure of the dura mater, the bone flap, and the scalp are then performed, the pins removed and the patient woken up. Following an awake craniotomy the patient returns to either a neurosurgical ward or a high-dependency unit bed.
This may require an urgent repeat craniotomy for evacuation of the clot. Some neurosurgical centres, including within the UK, carefully select appropriate patients for day case awake craniotomy surgery. There are stringent inclusion and exclusion criteria and the use of routine postoperative imaging for haematomas and access to advice after discharge if needed. Most patients are in hospital for 1—2 days after operation.
After the scalp block has worn off, systemic pain relief is used. The use of postoperative pain relief can be decreased in patients who have received a scalp block. Regular paracetamol and opioids, such as codeine, morphine, or oxycodone, are used. There is increasing evidence that an awake craniotomy would be an appropriate choice for removal of all supratentorial tumours non-selectively.
It can maximize lesion resection, which can be linked to improved survival rates, and has low complication rates. Details including positioning, urinary catheter placement, and noise related to craniectomy, amongst other subjects, should be carefully explained. The preoperative visit also allows an opportunity for patients to rehearse the various mapping-related tasks with neurophysiologists before surgery.
Obtaining some personal patient details that can serve as topics of conversation e. Reassurance and empathy facilitate the establishment of good patient rapport. May adversely affect neurocognitive function; 49 consider only if there is intractable anxiety. May cause nausea, itchy nose and dizziness; consider only if there is intractable pain. Oral or iv acetaminophen can be a useful analgesic adjunct. Possesses unwarranted neurologic effect, may cause dystonic reactions; not recommended. Previously used for neuroleptanalgesic anesthesia, may impede neurocognitive testing; not recommended.
Intraoperative care can be divided into three sequential phases based on how the anesthesia is managed: pre-awake phase, awake phase, post-awake phase. The following discussion is laid out based on this sequence of events.
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Standard patient monitors — electrocardiography, blood pressure, pulse oximetry, capnography, temperature — should be applied. Consideration should be given to placing the blood pressure monitor on the arm that is ipsilateral to the brain lesion so as not to interfere with the sensorimotor monitoring of the arm that is contralateral to the brain lesion. This should be done similarly with the pulse oximetry probe — i. If it is on the contralateral arm, the intra-arterial and intravenous catheters can be secured with transparent dressings to allow detection of any subtle motor responses that might otherwise be obscured under dressings.
These choices, however, are clearly institutional preferences. End-tidal carbon dioxide EtCO 2 should be monitored via the sampling channel integrated into nasal cannula tubing i. The respiratory rate but not the EtCO 2 can also be monitored using breathing cycle-induced electrocardiogram variation integrated into many standard monitoring platforms. Placement of an urinary catheter is facilitated by intravenous sedation and intra-urethral lidocaine application.
Urethral lidocaine e. Intraoperative language and sensorimotor mapping is normally tasked to a trained neurophysiologist and regarded as a surgical aspect of AC. The use of intraoperative stimulation mapping is one of the core components of AC and, based on a meta-analysis of available data, has been associated with fewer late severe neurologic deficits and more extensive tumour resection.
Heterogeneity exists in the use of intraoperative stimulation mapping and neurophysiological monitoring techniques. The technical details of intraoperative mapping can be found in other published reports. This maneuver positions the patient facing the anesthesia workstation, which makes the face-to-face interaction during the awake phase convenient and facilitates any airway management, if needed.
The body side i. The upper leg is elevated with padding. The hip and knee of the lower leg can flex slightly for comfort.
Intraoperative Functional Ultrasound Imaging of Human Brain Activity
The upper arm rests on the chest and abdomen. A small number of institutions simply support the head on a horseshoe frame or its equivalent. It is usually well tolerated by the patient. Various techniques of airway management during the pre-awake phase of AC have been described. The GA—awake—GA a. This technique is laborious and is prone to complications with inexperienced practitioners.
The tube exchanger left in the trachea for reintubation can affect intraoperative language testing. Even though the LMA offers some airway control, it does not guarantee satisfactory controlled ventilation. Ineffective ventilation due to a malpositioned LMA-related air leak, which can occur in a semi-laterally positioned patient when the head is slightly rotated, can cause undesired hypercapnia.
Some institutions use unilateral or bilateral nasopharyngeal airways nasal trumpet attached to the breathing circuit in patients who are spontaneously breathing but deeply sedated. In this case, a nasal cannula taped to both cheeks , with an EtCO 2 sampling channel, is used for supplemental oxygen and monitoring respiration. Although a nasopharyngeal or oropharyngeal airway is normally not needed, it can be placed when necessary, facilitated by propofol sedation and lidocaine paste.
If airway obstruction or hypoventilation develops, one can either add dexmedetomidine to minimize the dose of propofol or remifentanil, or stop sedative infusions altogether to awaken the patient. The superiority of any one technique for airway management during the pre-awake phase of AC is unknown because of the lack of comparative studies.
Otherwise, the patient is regarded as being under light to moderate sedation MAC. Potential disadvantages of light to moderate sedation for the pre-awake phase include movement, talkativeness, and anxiety. The transition to being fully awake, however, is much faster, more predictable, and less problematic. Comparison between craniotomy under general anesthesia GA and awake craniotomy.
Both surgical approaches are arbitrarily divided into three phases. For craniotomy under GA, the GA is applied throughout all three phases. Currently, MAC is the most popular anesthetic technique used during the post-awake phase. Some institutions rely solely on field infiltration, whereas others combine field infiltration primary modality with scalp nerve blocks as adjuncts.
The efficacy of field infiltration for controlling surgical pain during craniotomy has been verified by both clinical experience and previous studies. With adequate local anesthesia, intravenous opioid administration is rarely needed during AC. Subsequent injection of additional local anesthetics into the incision site including the dura and across the scalp flap is usually effective in relieving new-onset pain that occurs during the surgery.
According to the results of some laboratory and retrospective studies, other advantages attributable to local anesthetics include a neutral neurocognitive effect and potential tumour-suppressive effects. Exuberant application of local anesthetics has the potential to cause seizures and other toxicities, 67 as well as hypertension in the case of inadvertent intravascular epinephrine injection. It is enlightening to revisit the evolution of anesthetic regimens for AC, especially the story of the rise and fall of each drug.
What Horsley used in his AC patients was a combination of morphine and chloroform, with the chloroform discontinued during the case to awaken the patient. It should also benefit disease-specific outcomes, similar to the advantageous oncological effect i.
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Every modern anesthetic drug used for AC is a double-edged sword. Different patients may have differing sensitivities to the same drug. Moreover, the drug effect is almost always dose dependent. It is advisable not to put forward an invariable protocol but to advocate a flexible approach based on the needs and response of the individual patient. A recent retrospective study correlated the use of inhalational anesthesia, compared with intravenous anesthesia, with worse survival in cancer patients, although the study was not specifically done on brain tumour patients. Remifentanil, albeit a narcotic, is chosen because it is easily titratable, acts as a potent sedative i.
The satisfactory application of dexmedetomidine as a sole sedative agent for AC has also been reported. If a deep plane of sedation or GA is used during the pre-awake stage, preparedness for awakening the patient should be started as early as possible. The surgeon normally gives a time estimate for awakening the patient. All sedative or hypnotic agents are typically discontinued at the moment the bone flap is removed unless some asleep cortical mapping is desired.
The goal is to awaken the patient smoothly and rapidly without agitation, confusion, or drowsiness. The goal during the awake phase is to have the patient engaged, cooperative, pain-free, and comfortable. Similarly, ice chips work well to optimize patient comfort and offer a temporary distraction as they chew or suck the chips.
It is important to instruct the patient not to move the head and shoulders when making positional adjustments. An air blanket can be used as needed to provide either warm or cool air. Empathy, hand-holding, and reassurance offer great support to patients and should always be provided during the awake phase. Ongoing encouragement, coaching, and conversation are essential. Finally, keep in mind that bilingual patients may need bilingual language testing as language function for the primary language may not entirely overlap the secondary language. Emergence agitation and delirium can ensue on awakening, especially if the pre-awake phase is done under GA or deep sedation, and can be dangerous to the patient and extremely difficult to manage.
At this time, there is no consensus on effective management. Nevertheless, the following strategies can be used. A physostigmine bolus 0. Finally, droperidol or haloperidol can be administered prior to the re-awakening with awareness of the potential QT-prolonging effects. Effective prevention for emergence agitation and delirium is unproven. It is prudent to minimize sedation in high-risk patients e. Somnolence on emergence leaves the anesthesiologist with many fewer management options. Intravenous caffeine is an option but has undefined efficacy. Elderly patients seem particularly sensitive, 87 so great caution should be exercised with dexmedetomidine in these cases.
Similarly, midazolam should be avoided in elderly patients, especially those with impaired hepatic or kidney function. Imminent potential complications during AC that require life-saving intervention are seizures and airway emergencies. The first line of treatment is irrigation of the cortex with ice-cold crystalloid solution applied by the neurosurgeon repeated as necessary. If it is ineffective i. The patient must be closely watched for seizure recurrence or airway compromise.
Most intraoperative seizures are resolved without adverse consequences, although apnea and cardiac arrest can occur. Airway instrumentation is normally not needed. When needed, it is often the result of excessive propofol administration. For an obstructed airway emergency, a rapid differential diagnosis is needed to identify the cause.
In anticipation of such a life-threatening event, there should always be an LMA, syringe, and lubricant at hand. Some also like to have an ETT and video laryngoscope within reach. An LMA should be placed if mask ventilation fails or if the situation otherwise mandates it. It can be difficult to position an LMA in a semi-lateral patient whose head is slightly turned and secured in a pinned head frame. The patient can be intubated using a video laryngoscope with the anesthesiologist standing in front of the patient, although it is better done with the assistance of an additional skilled anesthesiologist.
Lastly, if the ventilation crisis is due to remifentanil-induced apnea or chest rigidity, one should attempt mask-ventilation while at the same time stopping the remifentanil infusion. These actions may be sufficient to resolve the crisis. Sedation is normally restarted, and the case can usually be finished without an LMA even if it was used during the pre-awake phase.
The patient typically requires lower rates of sedative infusions during the post-awake phase than during the pre-awake phase. This may be due to fatigue from the awake phase, release of the psychological pressure after learning of successful lesion removal, and the lower level of painful stimuli during skull closure compared with that at skull opening. The goal of sedation is to keep the patient drowsy but without airway obstruction. The rapid recovery after AC has revolutionized the subsequent care of these patients.
A recent systematic review concluded that AC is associated with a much shorter hospital stay four days than craniotomy under GA nine days based on seven comparative studies P value unreported. The short-term outcomes associated with AC, in contrast to those associated with conventional craniotomy under GA, can also be better appreciated with this early postoperative visit. Quality research and evidence can improve patient outcomes via standardization of clinical practice and the resolution of controversial topics.
The outcomes of most concern to patients e. The patients who experience persistent delirium stay in the intensive care unit and hospital longer, 97 , 98 have prolonged mechanical ventilation, 98 incur more health care cost, 99 and are at increased risk for dementia, institutionalization, and death after hospital discharge.
Finally, the effect of anesthetic agents on brain tumour progression or recurrence and patient survival should be prioritized in future research. Visit and establish good rapport with the patient; explain to patient the relevant details of the perioperative care; answer questions. Some authors prefer light to moderate MAC with the patient drowsy but readily arousable. Smooth and rapid return of the baseline mental status; avoid somnolence, confusion, agitation, and delirium.
The goal is to have an engaging, cooperative, pain-free, comfortable patient. No or minimal sedation e. Have a video laryngoscope in room; have an LMA different sizes with lubricant and an endotracheal tube with a stylet handy; have propofol and succinylcholine in syringe. If airway emergency, call for helper, stop infusions, mask-ventilate with an oropharyngeal or nasopharyngeal airway , try to place an LMA if no improvement with mask ventilation may need to pull the tongue out to facilitate the placement , try to intubate the patient using video laryngoscope by standing in front of the patient if LMA fails; surgeon to lift drapes out of the way while preserving sterility.
Irrigate ice-cold saline solution onto the cortex, small propofol bolus mg if needed; think ABC airway, breathing, circulation ; supportive if patient recovers; convert to GA if necessary; show empathy and comfort the patient if neurological complications e. LMA is normally not replaced even if used during the pre-awake phase. Sedation often suffices, as patients are often fatigued. Large variation in practice.
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Early discharge with a well-established backup plan is the current trend. The authors thank Dr. This submission was handled by Dr. Hilary P. Lingzhong Meng , David L. McDonagh , Mitchel S. Berger , and Adrian W. Gelb contributed substantially to the conception and design of this review article. Lingzhong Meng and David L. McDonagh drafted the article. Gelb critically revised the article. Skip to main content Skip to sections. Advertisement Hide. Download PDF. Anesthesia for awake craniotomy: a how-to guide for the occasional practitioner.
This process is experimental and the keywords may be updated as the learning algorithm improves. Importance of good patient rapport The path to successful AC begins with the preoperative patient interview. Premedications Some institutions routinely administer anticonvulsants and corticosteroids before surgery, whereas others, if the indication for AC is epilepsy, for example, withhold anticonvulsants to facilitate cortical mapping.
Medications e. Patient monitoring Standard patient monitors — electrocardiography, blood pressure, pulse oximetry, capnography, temperature — should be applied. The patient can be positioned supine — laterally on an axillary roll or semi-laterally with the back of the patient resting on a round longitudinal pillow. It also facilitates spontaneous ventilation by enhancing chest compliance in a patient with an obese abdomen. An axillary roll can be used in the lateral position but is normally not needed for the semi-lateral position.
Open image in new window. It has been argued that the avoidance of GA-related physiological disturbances, mechanical ventilation, and potential anti-tumour immunity suppression might contribute to the beneficial outcomes associated with AC, when compared with surgery under GA, 54 although the validity of this proposition remains highly speculative.
Nonetheless, an important distinction is needed here Fig. For craniotomy under GA, the anesthetic is applied throughout the procedure, whereas with conventional AC using an LMA the patient is exposed to GA only during the pre-awake phase. This is different from the scenario where the pre-awake phase of AC is performed under light to moderate sedation, and the patient is never exposed to GA.
The impact of GA vs light to moderate sedation on outcomes in this setting is unknown. It appears that the major institutions that perform AC are split on their preferences — some prefer a sedation level that renders the patient drowsy but readily arousable and others prefer GA with an LMA. The improvement in anesthetic care has made a major contribution to the increasing popularity of AC. Research is not always feasible when taking into account the scientific merits, priorities, and costs. Sedation often suffices, as patients are often fatigued Postoperative care Large variation in practice.
Conflict of interest None declared. Editorial responsibility This submission was handled by Dr. Author contributions Lingzhong Meng , David L. Financial support and sponsorship None. Horsley V. Remarks on ten consecutive cases of operations upon the brain and cranial cavity to illustrate the details and safety of the method employed. Br Med J ; 1: Penfield W , Boldrey E. Somatic motor and sensory representation in the cerebral cortex of man as studied by electrical stimulation.
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Awake craniotomy vs surgery under general anesthesia for resection of supratentorial lesions. Neurosurgery ; The evolution of brain surgery on awake patients. Acta Neurochir Wien ;