Anesthesia and the Awake Craniotomy - Term Paper Example

Undoubtedly, the brain is an essential organ of the human body. Without this vital organ, senses such sight, hearing, tasting, smelling and feeling cannot be put to use. The brain controls everything in the human body 1 and is considered a complex structure. It is a mass of nervous tissue assembled together, weighing three pounds with more than ten billion cells present in it. The brain is able to receive impulses from various structures of the body. The brain is given the function of examining the received impulses and making the necessary adjustments or movements for that particular event. The brain is termed as man’s consciousness, memory, reasoning and intelligence. The idea that emotions are controlled by the heart is a misnomer. The emotions felt by humans are still controlled by the brain 2. The human brain is synonymous to an electrical company wherein millions of wires are needed to make the transfer of impulses smoothly and if one wire is not functioning accordingly, it will have an effect on the whole system. Similar to the brain, millions of nerves are present and function properly to guarantee smooth transmission of impulses. If a part of the brain has been affected or if a nerve was damaged along the process, it can affect the proper functioning of the brain. As what is reported 3, the brain constantly changes its structure as a response to the shifting environment brought about by man himself. Also, there is categorization among the structures and functions of the nervous system. The brain has the most important role not only for the nervous system but for all the systems present in the body. From Ramon Cajal’s 4 aembryonic pyramidal cell, he associated the development of axonal collaterals and protoplasmic with the increasing size and complexity of the cortex. As quoted from Cajal 4 (p. 107) “Cerebral gymnastics are not capable of improving the organization of the brain by increasing the number of cells . . . but it can be admitted as very probable that mental exercise leads to a greater development of the dendritic apparatus and of the system of axonal collaterals in the most utilized cerebral regions.” The role of the brain is important since it takes control of every aspect of our existence. The concept of the brain‘s chief role was verified by Plato and the Hippocratic physicians stated that the brain “comes joys, delights, laughter and sports, and sorrows, grief, despondency and lamentations. And by this, in an especial manner, we acquire wisdom and knowledge and see and hear, and know what.” 5 (p. 192) Due to the unrelenting experiments and researches handled by the scientists, the brain has been studied complexly. Gall’s concept5 which dates back to the late 17th century assert that certain areas of the brain are correlated with a particular function such as frontal lobe pathology with speech. As reported by San Diego Academic Press, 1998 6, the civilization of mankind has come a long way. Through the years, the writing and reading skills of man had been perfected. It is because of this skill that permits man to transfer knowledge and language. Reading and writing are not just an easy task particularly for the brain. Reading and writing are complex process. These processes involve the multi parts of the brain in the left and right hemisphere of the brain7. The reading function is still dependent on the organization of the cortical areas. The function is reliant on the types of reading, training for reading and the languages used. The languages used and the capability of understanding the language poses many question for the reading function correlated with the cortical area of the brain8. As reported from Trends Neuro Science 9 the human olfactory learning for humans is only based from animal studies. There are no studies about long-term and short-term recognition of learning. The olfactory learning was further examined especially those patients who have specific restrictions in their temporal lobe. Human olfactory function and the temporal lobe region had been associated as early as 1800’s. The context of olfactory auras and olfactory dysfunction was evident on epileptic patients. Continuous study and researches were done and it has been proven that from the primary regions of the brain, there is a connection to the hippocampus, ventral striatum, thalamus and orbitofrontal cortal areas.10 From Epilepsia 11 before the epileptic patient undergoes surgical procedures, the olfactory memory of epileptic patients and after surgical procedures in the different regions of the brain is only subjected to the resection of the temporal lobe and orbitofrontal region which displayed impairments. The damage done on the olfactory memory is still undetermined – that is, if it is the left part or right part of the brain. The odor recognition and other functions had been affected due to the location of the lesions and sections of the lobe, whether it is on the left section or right section. The section on temporal lobe epilepsy is first-rate and the section on neocortical epilepsy is suggested. The section correlated with the anterior callosal section with frontal resection is unusual. A patient with occipital lobe epilepsy demonstrates many important aspects of the management of these patients and the association between occipital and temporal epileptic activity. The identification of the epilieptogenic zone was the main focus. The seizure origin of the patient can be traced to the lesion, usually by depth recording and attacking the lesion is more likely to be effective 12. The common development of the grip–lift synergy is paralleled with the development of manual skills. Precision grip such as independent finger movements are manipulated directly by the motor cortex via the corticomotoneuronal system13. Increased movements are correlated with the growth and maturation of cortical representation. A strong correlation was evident among the lesions of the basal ganglia and thalamus and a poorly developed grip–lift synergy. The main role of the basal ganglia is for motor control. The basal ganglia play a critical role during the motor learning process but its role diminishes in importance as the motor behavior has been established14. Children affected by cerebral palsy have impaired dexterity due to the lesions present in the basal ganglia 15. The impairment is due to muscoloskeletal malformations affecting finger tip movement. Some parts of the brain have been affected and with these some precise movements of the body were necessarily impacted on. There must be communication among basic and clinical science in the areas of brain damage and repair. Neuroscience research is progressing quickly wherein information easily becomes obsolete. Clinical neurologists and neurosurgeons continously seek to establish the correlation between damage and repair in the brain and spinal cord16. The Rationale Behind Awake Craniotomy The continuous advancement in the field of neuroimaging resulted in pre-planned surgical procedures 17. It provides the functional mapping of the brain making it easier for neurosurgeons to conduct brain surgery. The surgical procedures are well-organized since the functional map of the brain has been provided. Patients having lesions in or approximately near the motor speech area was studied after an awake craniotomy. Most of the patients were able to regain their skills except for one patient who suffered dysphasia after the surgery. Awake craniotomy is successful in maximizing the restrictions, particularly for patients with speech defects. Functional neuroimaging is a useful technique in mapping the cortical areas making the surgical procedure easier18. Despite the mapping of the functions of the human brain and its parts, understanding the whole process occurring inside the brain is still limited. There is no specific procedure that can keep track of the neural connections from the brain to its parts resulting to restricted surgical procedures. Diffusion-weighted MRI has been evaluated as reagards its utility to track down the neural connections within the brain19. Different techniques have been tested to know what would be the most effective in mapping the brain and its functions. The autoradiographic technique20 was proven to be effective animals. But for human studies, this technique is limited. The technique can only determine the location, extent of lesion on the anatomical view of the brain, as well as severity of damage and the clinical consequences. Brain surgery using local anesthesia has been improved due to the development of quick-acting anesthesia and useful technique for brain imaging 21. Awake brain surgery is used not only for treating epilepsy but also for the removal of gliomas and tumors in the eloquent cortex. Aside from improved brain surgeries, if this technique will be used often, the complete process in the brain can be completely understood. Aside from speed, this surgery prevents damage to the speech capability of the individual. Before the surgical procedure can be carried out, computed tomography scans (CT) or magnetic resonance imaging (MRI) scans are done with the patient to find out the core problem requiring them to undergo craniotomy. These diagnostic procedures are done to have a better view at the brains structure. Moreover, cerebral angiography can be used for patients to study the blood supply to the tumor, aneurysm, or other brain lesion22. Craniotomy is a surgical procedure where a part of the skull (skull flap) is removed to get into the brain. This surgical procedure is useful for lesions, implantation of deep brain stimulators for treating Parrkinson’s, epilepsy and cerebral tremor. Also, it is necessary for the upgrade of the field of neuroscience since it is used for extracellular recording, brain imaging, and manipulations such as electrical stimulation and chemical titration, extracellular recording, brain imaging, and manipulations such as electrical stimulation and chemical titration23. Utility of Awake Craniotomy Awake craniotomy has been commonly used to treat epileptic patients 24. It is also used for the resection of tumors found in the eloquent cortex. There are different anesthetic techniques for awake craniotomy. The anaesthetist is responsible in providing enough sedation, analgesia, and respiratory and haemodynamic control, but the anesthetist must see to it that the patient is awake. A cooperative patient ensures good results such as increased accurate pathological diagnosis, reduced intercranial pressure and the lowered chance of occurrence of low grade tumor. Anaesthetic techniques for awake craniotomy have been continuously improved through the years including local anaesthesia and sedation or true asleep–awake–asleep techniques using general anaesthesia with intra-operative wake-up 25. The main advantage of awake craniotomy is its capacity to evaluate the patients neurological status during surgery, although this capacity must be balanced against the loss of control of ventilation and assurance of immobility. The use of short-acting anaesthetic agents offer good operating conditions for the neurosurgeon while making sure that the patient is cooperative and that the patients is still feeling comfortable. The neuroanaesthetist plays a key role in the perioperative management of this challenging procedure. Anaesthesia As stated anesthesia is important in surgical procedures. It originated from the Greek which means without or loss of perception 26. The kind of anesthesia to be used is dependent on the surgical procedure to be carried out to the patient. The use of anesthesia is recommended by physicians for the patient’s comfort during the surgical procedure. The specialty of neuroanesthesia carries on adapting with changes in neurosurgical procedures, developments in operative technology, and advances in neuro-imaging. New anesthetic agents, new monitoring devices, new surgical procedures and new thinking on the management of the central nervous system (CNS) disease are given focus 27. New Anesthetic Agents There are new anesthetic agents that have been used recently and they are as follows; Propofol Propofol was recommended with its precaution because of its potential to lower the mean arterial pressure (MAP) and cerebral perfusion pressure (CPP) 28. It is known as a useful agent in neuroanesthesia, especially for induction, sedation or as a component of total intravenous anesthesia (TIVA). It produces a decrease in CBF, cerebral metabolic rate (CMRO2), and ICP. Propofols capacity to provide "brain protection" is currently being studied and debated. The advantages of taking Propofol are rapid onset of effect, speedy recovery of the patient, decrease in CBF, ICP, CMRO2 and expensive neurophysiologic monitoring cost while the disadvantages of taking it include potential hypotension, prolonged effect and reliance on I.V. access. Desflurane This volatile anesthetic agent has similar effects to isoflurane on CBF and ICP. Concentrations of 1.5 MAC or higher may increase CBF and cerebral blood volume. The manifestation from anesthesia with desflurane is quicker than with isoflurane and with nominal biodegradability, and it is recommended for patients undergoing prolonged surgical procedures. Rapid onset and emergence, decreased CMRO2 and minimal biodegradability are the advantages of desflurane. Coughing, CBF and ICP’s likely increase, and high cost are the disadvantages of this anesthetic agent 29. Sevoflurane This anesthetic agent has similar effects on CBF and ICP but the onset and emergence from anesthesia is quicker. Sevoflurane has a "less noxious" odor and can be used more efficiently for mask inductions in children and adults. It is expensive for long procedures but may be useful when no IV access is present. It poses the possibility of causing renal injury and and its effects are still being closely studied 30. Remifentanil The profound hemodynamic control and ultra-short half-life of remifentanil have made it an appealing agent for neuroanesthesia. In patients with supratentorial brain tumors, remifentanil and alfentanil were evaluated. Neither opioid caused a significant increase in ICP. Its lack of residual analgesia results in significant discomfort, which must be relieved before excessive hypertension occurs postoperatively 31. Monitoring Monitoring in neuroanesthesia includes cerebral oximetry and neurophysiologic techniques such as EEG and evoked potentials 32. Monitoring of motor-evoked potentials permits accurate mapping of the motor cortex and brain-stem if needed. A new EEG parameter, the bispectral index (BIS) is now accepted as a guide in monitoring anesthetic depth and the hypnotic effect of anesthetic agents. Intraoperative titration using BIS may allow for more rapid recovery from anesthetics and may be used for monitoring of burst suppression. Transcranial Doppler (TCD) monitoring may be of value preoperatively in screening for vasospasm 33. Intraoperative use during craniotomy is cumbersome and unsubstantiated as a modifier of outcome. There is increasing hope that computerized analysis of TCD waveforms may provide useful data on intracranial pressure (ICP) and this could be useful during induction. Clearly, TCD can recognize entire barriers to blood flow. Still, there are more helpful information about the extent of ICP allowing estimation of cerebral perfusion pressure which is unavailable currently. New Procedures Stereotactic Biopsy/ Craniotomy Stereotaxis is the exact location of a definite circumscribed area within the brain, with nominal damage to the remainder of the organ, by repositioning a probe or electrode along coordinates from exact distances from certain external points or markerS of the skull creating smaller incision which increases the potential for decreased blood loss and speedy recovery for the patient. Anesthetic techniques can vary according to the patient, location of the lesion, and surgical preference. The potential problems for this new method are seizures, bleeding, airway loss, and air embolism 34. Kinds of Anesthetics Local anesthetics are similar to those used by dentists and these anesthetics are injected using a hypodermic needle into the tissue surrounding the area to be operated 35. Local anesthetics are not recommended if inflammation or infection of the tissues around the surgery site is present. The drugs used for local anesthetics can lower the patient’s resistance to infection and the same time, the inflammation can reduce the effectiveness of drug as pain-killer. The advantages of local anesthesia with sedation are as follows: being less expensive; with less equipment needed; the patient can assist in movement; and most importantly, the ability to evaluate the patient’s neuro status. On the other hand, the disadvantages are as follows: discomfort for the patient; potential for respiratory depression; loss of airway during seizure; and limited position for the patient. General anesthetics are those that induce sleep or unconsciousness, along with absence of pain. It causes amnesia to the patient while it is taking effect 35. Also general anesthetic produces a certain loss of muscle tone and reflex action. The advantages of General Anesthesia with Endotracheal Incubation includes secured airway path, control of ventilation, amnesia and blood pressure control while the disadvantages encompass additional monitoring, inability to track the neuro status and being very costly. Anesthetic Techniques The goals of the anesthetics techniques are as follows 36: 1) Provide adequate sedation and analgesia for bone flap removal; 2) Attain a suitable level of consciousness for cortical speech or seizure focus mapping; and 3) Maintain patient comfort, hemodynamic stability, and prevent complications. Complications include nausea, excessive sedation, seizures, and patient intolerance. Numerous techniques for conscious sedation and monitored anesthesia care have been described. It is also extremely important to provide adequate local anesthesia. Local Anesthesia This section is essential and can only be carried out by the surgeon and/or the anesthetist. The best technique would be the one designed for blocking of the nerves, which innervate the scalp. In addition, infiltration may be carried out in the area of incision. It requires the use of bupivacaine 0.5% with epinephrine, 1:200,000 lasting for 8-9 hours. This solution is injected at described markers requiring 20 minutes for full onset. It can also be performed in the operating room after the patient has been given sedation or prior to his coming. It is important that the patient be aware of the total amount of local anesthetic administered to him for the surgical procedure to be done 37. Intravenous Agents Traditionally, techniques using intravenous narcotics and neuroleptic drugs have been successful for conscious sedation during the awake procedure. Fentanyl and droperidol are usually used and may be injected by bolus or infusion techniques. Fentanyl and droperidol are efficient in lessening the discomfort related with scalp infiltration and the surgical procedure. It is important to titrate the dose carefully and to be aware of the more painful parts of the surgery. While fentanyl is useful, the shorter-acting agent, alfentanil gives more advantages since it can be easily induced (0.5-0.25 ug/kg/min) and preserved throughout the preparation and start of surgery. The dose allowing spontaneous ventilation and comfort is maintained until approximately 20 minutes before testing is required. Remifentanil has recently been reported for this use as it has a shorter duration of action requiring less than 5 minutes for offset when administered with a propofol infusion38. Concerns unique to induction of anesthesia for craniotomy are principally related to ICP in the case of mass lesions or prevention of hemorrhage in the case of vascular lesions. The history of effects of anesthetics on ICP during induction began in the 1960s when the earliest measurements were made on patients anesthetized for tumor surgery. Major increases in ICP were observed with anesthetic induction. In the subsequent fervor to provide optimal care, it was felt that any increase in ICP could only be unfavorable for the patient and thus use of anesthetics known to increase ICP was avoided. Although logical, this came at some cost. Something should be used to offer anesthesia and those drugs known to reduce ICP (e.g., thiopental) typically have prolonged durations of action or produce hemodynamic instability39. The effects of various anesthetics on ICP in humans are inadequate because most information has been derived from animal studies. More importantly, there is insufficient data regarding any relationship between anesthetic effects on ICP and outcome from craniotomy. The few human studies that have been performed have used crude outcome assays putting off a definitive definition of the relevance of this problem. As a result, the use of various anesthetics during craniotomy have been broadened to allow all facets of a successful anesthetic to be considered40. Awake Craniotomy Craniotomy in the awake state41 has been carried out even in the ancient times. Present day signs include resection of a lesion in the eloquent or speech center of the brain. Surgical procedures for the treatment of seizures, tumors, or arteriovenous malformation have been performed in the awake patient. With refinement of neurophysiological monitoring techniques, awake craniotomies are vital for only a small percentage of patients. However, surgery for movement disorders has doubled in number because of this technique. The preliminary approach to the patient requiring craniotomy is similar to that of all other patients. There are just some additional considerations. It is important to obtain an appropriate baseline neurologic evaluation. At emergence from anesthesia, failure to recover the baseline neurologic function can be credited to surgery, anesthesia, or an interaction between the two. It is the responsibility of the anesthesiologist to recognize changes from baseline so as to participate in making the diagnosis42. It is also important to gain insight into the magnitude of intracranial hypertension and possible interactions with anesthetic agents. Acute changes in intracranial pressure (ICP; e.g., epidural hematoma) are potentially more devastating and are likely to be more sensitive to anesthetic effects. The anesthesiologist also can benefit from appreciating the characteristics of the lesion with respect to potential for major hemorrhage43. With respect to vascular lesions, it is valuable to know the interval since aneurysmal hemorrhage with respect to importance for surgery relative of risk of vasospasm. Patients receiving nimodipine/nicardipine exhibit exaggerated hemodynamic responses to volatile anesthetics. For arteriovenous malformations (AVM), history of preoperative neuroradiologic intervention can help the anesthesiologist in anticipating magnitude of blood loss and potential for perioperative malignant brain swelling. Resection of a radiologically obliterated AVM typically poses small risks for these complications, while untreated previous lesions need attention44. Awake craniotomy requires a responsive patient who can safely and comfortably cooperate for a long neurosurgical procedure. The advantages of awake craniotomy include the ability to identify the seizure focus and minimize brain injury and minimal anesthetic effects to suppress seizure activity and rapid recovery. The disadvantages of this surgical procedure are as follows: prolonged surgical procedure with awkward body positioning, need for patient cooperation to evaluate language, memory, and motor skills, potential for significant patient discomfort- pain, nausea, recall potential for emergent airway management should the patient become uncooperative or persistent seizure activity occur45. The general procedure for craniotomy includes the following steps. 1) The hair on the scalp is shaved. 2) The patient is given a general anaesthetic. 3) The patient’s head is placed on a round or horseshoe-shaped headrest so that the area where the brain injury is thought to lie is easily accessible. If head movement must be minimized, the patient’s head is clamped into place with a head pin fixing device. 4) Through preoperative imaging, the neurosurgeon can know the most appropriate site for the craniotomy. The procedure begins by first cutting through the scalp. 5) Small holes (burr holes) are drilled into the exposed skull with an instrument called a perforator. 6) An instrument called a craniotome is used to cut from one burr hole to the next, creating a removable bone flap. 7) The membrane covering the brain is opened, usually as a flap. 8) The brain injury or disease is operated on – for example, ruptured blood vessels are repaired, or the blood clot or tumor is removed. 9) After the operation is finished, the piece of excised bone is replaced, the muscle and skin are stitched up and a drain is placed inside the brain to remove any excess blood left from the surgery. 10) A craniotomy can take about two and a half hours 46. For reasons not yet understood, patients undergoing craniotomy may exhibit hypertension during emergence that is sustained through the early phases of recovery. Because of the implications of intracranial hemorrhage, it is mandatory to plan the treatment of hypertension before it becomes manifest. Prophylactic doses of labetolol are helpful, usually requiring 40–60 mg to be effective. It has not been proven that hypertension is part of the cause of hematoma formation. It has been shown, however, that many patients who develop postoperative hematomas had episodes of hypertension during emergence or early recovery47. The chief source of hemorrhage is almost always within the surgical field and thus quality of hemostasis undoubtedly is important. However, because the mortality associated with postoperative hematoma formation needing emergent evacuation is high, it seems incumbent on the anesthesiologist to seriously attend to management of hemodynamics during emergence47. Postoperative nausea and vomiting (PONV) is a frequent problem after craniotomy. Several studies have shown that greater than 50% of patients suffer this complication. The incidence of PONV appears to be independent of whether the craniotomy was performed awake or under anesthesia, and independent of opioid dose. This suggests that surgery itself is contributory. Females, younger patients, and those undergoing infratentorial craniotomy are at greater risk 48. PONV is not only an early emergence problem but can be sustained for hours or days after surgery 49. Ample evidence is now available that prophylactic anti-emetic therapy markedly reduces the magnitude of this problem. Droperidol (0.625 mg) appears to be at least as effective as 4 mg ondansetron without causing detectable sedation. In either case, the duration of action of a single dose just prior to emergence is expected to be several hours. This is likely to be transiently beneficial and will require repeated supplementation if PONV is to continue to be suppressed. It is important to know if the patient is dying of intracranial hypertension. This is particularly true of expanding hematomas. These cases are unquestionable surgical emergencies. The cure is surgical and the most important thing the anesthesiologist can do is make the patient ready for incision as rapidly as possible 50. Regardless of academic discussions on the importance of anesthetic effects on ICP in scheduled craniotomies, most agree that in these patients all effort should be made to minimize increases in ICP. Patients who are herniating, or near herniating, are not likely to be conscious. Prevention of recall is of minimal concern51. Effort should be made to secure the airway as rapidly as possible and turn the patient over to the surgeon. Small doses of barbiturate (so as to not cause hypotension) to reduce metabolic rate and coupled blood flow or opioid may be appropriate until surgical decompression is achieved. Profound hyperventilation should be avoided. Inhalational anesthetics have little or no role in the early stage of these procedures. Enhanced venous and arterial access can be made by the anesthesia team simultaneous with onset of surgery52. After the surgery, some drugs will be taken for faster recovery phase. These are among the most common drugs that may be ingested: Steroid Medication It reduces the swelling in the brain. If the operation is for tumor and the patient is undergoing radiation therapy, the dose of the medication decreases slowly and stops at the same time when the radiation therapy ends. A lot of patients who had undergone craniotomy, do not need dexamethasone 53. Anticonvulsant Therapy This therapy is for patients who are experiencing seizures. If the patient is not experiencing seizures then he does not need to take in medicine for anticonvulsant. If the patient needs to undergo this therapy, he must see to it that he is aware of the side effects of the drugs and as well to monitor his blood vessel 54. Expectations after Craniotomy 1) All patients who have undergone craniotomy will feel very tired. Rest is very important for the patients. Headaches would be felt every now and then around the wound. The tiredness felt by the patient can lead to short-temperedness but it is the common reaction and nothing to worry about. 2) The wound will feel sore for five days due to the cut nerves causing numbness that will eventually heal. As the wound starts to heal, a shooting pain would be felt near the wound and also scalp is very itchy which is indicative of healing process. 3) As the swelling in the scalp subsides, the depression which has been the point of entry for the surgical procedure will be evident. The bone flap will shrink with the help of exercise. 4) Headaches would be felt often but it is nothing to be worried about. Panadol or panadiene can be taken in for relief. At the end of the day, the intensity of the headache is increasing which is associated with tiredness. 5) If the patient before the operation is clumsy or weak then there is great possibility that after the operation, improvements on his weakness and clumsiness will be evident. 6) Alcohol must be avoided since it can alter the process of healing 7) Tiring exercises are not recommended because it will just make the patient tired resulting to severity of the headache felt by the patient. 8) Physiotherapy exercises are suggested. Simple walking can help the patient for faster recovery. Also if the patient had cuts on his temporalis muscle then the simple mouth opening would be a good exercise for the patient. 9) The patient is advised to have a complete 6-week rest before going back to his daily routine 10) If the pain felt is intolerable, it still best to consult a physician 55. References 1. Clark R. Brain. My First Encyclopedia. Vol. 4. International ed. 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