Dexmedetomidine for neurocognitive testing in awake craniotomy: case report

Abstracts

JUSTIFICATIVA E OBJETIVOS: As ressecções tumorais em áreas eloqüentes do cérebro são realizadas com mais segurança utilizando-se testes cognitivos para identificação exata desses locais. Os pacientes devem estar acordados, confortáveis e colaborativos para que se identifiquem com clareza as áreas que devem ser preservadas. O objetivo deste relato foi apresentar intervenção cirúrgica realizada com o paciente acordado, utilizando sevoflurano no período inicial, sem intubação traqueal e a dexmedetomidina, posteriormente, técnica que permitiu a realização dos testes de avaliação motora e da fala. RELATO DO CASO: Paciente do sexo masculino, 27 anos, estado físico ASA I, com tumor cerebral. Na sala cirúrgica, sem medicação pré-anestésica, foi administrado midazolam (1 mg), induzida a anestesia geral com propofol (80 mg). A manutenção foi realizada com O2, N2O e sevoflurano sob máscara para punção da artéria radial direita, cateterismo vesical e infiltração da área cirúrgica. Essa fase durou cerca de 20 minutos, com início da infusão de dexmedetomidina nos últimos 10 minutos, para manter o nível de sedação Ramsay 2. Depois, foi realizado o mapeamento cortical (75 minutos). Seguiu-se a ressecção tumoral, com o paciente sedado recebendo doses maiores de dexmedetomidina. Observou-se estabilidades hemodinâmica e respiratória, tendo o procedimento transcorrido sem intercorrências, com duração total de cinco horas. Após o término da intervenção cirúrgica o paciente foi encaminhado ao CTI, sem alterações neurológicas, tendo alta para a enfermaria no dia seguinte. CONCLUSÕES: A craniotomia com o paciente acordado e o adequado mapeamento das áreas corticais de fala e motora foram realizados com sucesso, por meio da infusão contínua de dexmedetomidina. Houve plena satisfação do paciente e da equipe cirúrgica com a técnica.

CIRURGIA, Neurocirurgia; DROGAS

CLINICAL INFORMATION

Dexmedetomidine for neurocognitive testing in awake craniotomy. Case Report^*

Dexmedetomidina para prueba neurocognitiva en craniotomía con el paciente despierto. Relato de Caso

Marcelo Cursino Pinto dos Santos^I; Ronaldo Contreras Oliveira Vinagre, TSA^II

^IME₃ do CET Bento Gonçalves, UFRJ

^IICo-responsável pelo CET Bento Gonçalves, UFRJ

^{Correspondence to}

SUMMARY

BACKGROUND AND OBJECTIVES: Tumor resections in the speech areas of the brain are more safely done using cognitive tests to determine their exact location. Patients must be awake, comfortable, and cooperative for the precise identification of the areas to be preserved. The objective of this report is to present a surgical procedure done with the patient awake, without endotracheal intubation, using sevofluorane initially, followed by dexmedetomidine. This technique allowed the realization of motor and speech evaluation tests.

CASE REPORT: Twenty-seven years old male patient, physical status ASA I, with a brain tumor. In the operating room, without pre-anesthetic medication, midazolam (1 mg) was administered, and general anesthesia was induced with propofol (80 mg). Maintenance was done with O₂, N₂O, and sevofluorane, with a mask, for catheterization of the right radial artery, introduction of a vesical catheter, and infiltration of the surgical site. This phase lasted around 20 minutes, and the infusion of dexmedetomidine was initiated in the last 10 minutes to maintain a level of sedation Ramsay score 2. Cortical mapping followed (75 minutes). Afterwards, tumor resection was done while the patient remained sedated with higher doses of dexmedetomidine. Hemodynamic and respiratory parameters remained stable, and the procedure was performed without complications, lasting a total of five hours. After the surgical procedure the patient was transferred to the ICU. He did not develop any neurological changes, being discharged to a regular ward the following day.

CONCLUSIONS: Awake craniotomy with the proper mapping of speech and motor cortical areas was successfully done with the continuous infusion of dexmedetomidine. Both the patient and the surgical team were pleased with the technique.

Key Words: DRUGS: dexmedetomidine; SURGERY, Neurosurgery: craniotomy, cognitive tests.

RESUMEN

JUSTIFICATIVA Y OBJETIVOS: Las resecciones tumorales en áreas elocuentes del cerebro son realizadas con más seguridad utilizando pruebas cognitivas para la identificación exacta de esos locales. Los pacientes deben estar despiertos, cómodos y con deseos de colaborar para que se identifiquen claramente las áreas que deben ser preservadas. El objetivo de este relato fue el de presentar intervención quirúrgica realizada con el paciente despierto, utilizando sevoflurano en el período inicial, sin intubación traqueal y la dexmedetomidina, posteriormente, técnica que permitió la realización de las pruebas de evaluación motora y del habla.

RELATO DEL CASO: Paciente del sexo masculino, 27 años, estado físico ASA I, con tumor cerebral. En la sala quirúrgica, sin medicación preanestésica, se le administró midazolam (1 mg), inducida la anestesia general con propofol (80 mg). El mantenimiento se realiza con O₂, N₂O y sevoflurano bajo máscara para punción de la arteria radial derecha, cateterismo vesical e infiltración del área quirúrgica. Esa fase duró aproximadamente 20 minutos, con inicio de la infusión de dexmedetomidina en los últimos 10 minutos, para mantener un nivel de sedación Ramsay 2. Subsecuentemente se realizó el mapeo cortical (75 minutos). En seguida la resección tumoral, con el paciente sedado recibiendo dosis mayores de dexmedetomidina. Se observó una estabilidad hemodinámica y respiratoria, habiéndose dado el procedimiento sin incidencias, con duración total de cinco horas. Después el término de la intervención quirúrgica el paciente fue llevado al CTI, sin alteraciones neurológicas, y le fue dada el alta para enfermería al día siguiente.

CONCLUSIONES: La craniotomía con el paciente despierto, adecuado mapeo de las áreas corticales del habla y motora fue realizado con éxito, a través de la infusión continua de dexmedetomidina. Hubo una plena satisfacción del paciente y del equipo quirúrgico con la técnica.

INTRODUCTION

Surgical interventions in the speech areas of the brain present a challenge to surgeons and anesthesiologists. Many of these lesions are better demarcated and removed while the patient is awake, allowing for prompt responses when these prime areas are stimulated. For such interventions, the patient should be comfortable during the procedure and alert in order to cooperate and to participate in the cognitive tests realized during the demarcation of the surgical area in the cerebral cortex¹.

The technique of conscious sedation allows the maintenance of independent and functional airways besides the patient's ability to respond appropriately to motor stimuli and verbal orders, being one of the options for the realization of these procedures².

During the most painful moments of the surgical procedure or when there is no need for a patient's cooperation, some techniques of general anesthesia, intravenous, inhalation, or a combination of both, are used and the patient is intubated or a laryngeal mask is used³. When this technique is used, the patient has to be awake, extubated or the laryngeal mask has to be removed, during the period of cognitive testing.

Dexmedetomidine is an a₂-adrenergic agonist with potent hypnotic, ansyolitic and analgesic actions. It causes sedation without respiratory depression, therefore avoiding hypercapnia and hypoxemia^4,5. It maintains adequate hemodynamic stability and inhibits the secretion of stress hormones, avoiding the administration of other adjuvant drugs. It also provides an easy and early awakening.

The objective of this case report was to present the use of general anesthesia for invasive surgical procedures that are more painful in the beginning, without the need of tracheal intubation or laryngeal mask, and maintaining sedation with low dexmedetomidine dose during the main surgical periods, avoiding the development of psychomotor agitation, respiratory depression, hemodynamic changes, excessive sleepiness and, especially, without interfering with the cognitive evaluation necessary during the procedure.

CASE REPORT

Twenty-seven years old male patient, white, physical status ASA I, with a diagnosis of a cerebral tumor in the right temporoparietal region measuring 6 cm in its larger diameter.

He presented seizures controlled by carbamazepine (1,200 mg.d^-1). Tumor resection was indicated; it was diagnosed as a probable glioma.

The patient did not receive premedication in the morning. Upon arrival in the operating room the patient was awake, alert, oriented, and cooperative. Monitoring included non-invasive blood pressure, cardioscope, and pulse oxymeter; venipuncture was done in the right upper limb with a 16G peripheral catheter. After sedation with midazolam (1 mg), cefazoline (2 g), dexametasone (10 mg), droperidol (1.25 mg), and metoclopramide (10 mg) were administered. General anesthesia was then initiated with propofol (80 mg), and the patient was under assisted ventilation with a face mask with oxygen (O₂), nitrous oxide (N₂O), and sevoflurane. Catheterization of the right radial artery, insertion of a vesical catheter, and another venipuncture in the left upper limb with a 16G catheter were done while the patient was under general anesthesia.

Infiltration of the area of the surgical incision with 0.33% bupivacaine and adrenaline 1:200,000 was also done in this initial phase. A cushion was placed under the patient's neck and shoulder on the side to be operated to relieve the tension in this area and provide a comfortable position. His legs were flexed and a pillow placed under them. These procedures lasted around 20 minutes. The infusion of dexmedetomidine was initiated in the last 10 minutes.

The surgical intervention was initiated after the patient awakened; at this moment, he was slightly sedated (Ramsay 2), under the influence of dexmedetomidine (0.2 µg.kg^-1.h^-1) that was started during the period of general anesthesia. During craniotomy, which lasted approximately 50 minutes, the patient was sedated, being capable of reacting to verbal stimuli (Ramsay 3), with dexmedetomidine in doses varying from 0.2 to 0.4 µg.kg^-1.h^-1.

Electro-stimulation for cortical mapping lasted approximately 1 hour and 15 minutes. During this time the patient was conscious, but under sedation, being stimulated to speak and move his limbs; the doses of dexmedetomidine were in the range of 0.1 to 0.3 mg.kg^-1.h^-1 (Ramsay 2). The stimulation and mapping of motor and speech cortical areas were successfully done. Afterwards, the surgical procedure per se, for resection of the tumor, was initiated.

During tumor resection, which lasted approximately 2 hours and 15 minutes, sedation was maintained with dexmedetomidine (0.2 to 0.6 mg.kg^-1.h^-1) and the highest concentration was used in the last 70 minutes (0.5 to 0.6 mg.kg^-1.h^-1), in the phase of closure of the surgical site. The patient was sedated during this period, maintaining a Ramsay level 3.

Regarding the hemodynamic parameters, there was a reduction in mean arterial pressure from 85 mmHg to 70 mmHg when compared to the values obtained upon admission to the operating room. This lower level was maintained throughout the procedure; heart rate remained stable, around 75 to 80 bpm. There were no complications during the anesthetic-surgical procedure.

Cerebral edema detected by the naked eye was not observed during the procedure. Mannitol was not infused. Four hours after incision of the skin, arterial blood was drawn for ABGs, which showed pH 7.39, pO₂ 152 mmHg, and pCO₂ 32 mmHg. The anesthetic procedure lasted five hours.

Upon arrival to the intensive care unit, the patient was awake, alert, and oriented; his hemodynamic parameters were stable; he showed no neurological deficits. He was discharged to the regular ward the following day.

DISCUSSION

Anesthesia for awake craniotomy has been done for many years using a number of techniques, from local anesthesia associated or not with sedation to general anesthesia, in which the patient is awake during the period that cortical mapping around the tumor area is done^3,5.

Several sedation techniques are used, including fentanil alone or with droperidol or propofol and, more recently, fentanil and remifentanil with or without propofol. When general anesthesia is chosen, the intravenous drugs used are mainly the association of opioids and propofol. Recent reports have shown a preference for inhaled anesthesia with drugs that are rapidly eliminated, which are discontinued during the cognitive tests, allowing the patient to cooperate with them. The inhaled combinations used more often are sevoflurane or desflurane with nitrous oxide and oxygen, aiming at a quick awakening, without agitation, and with precise answers during electro-stimulation^4,6.

The indications for cognitive testing in tumor resections to identify speech and motor areas include resections near those areas (Broadman's 4/6 areas and resections including the anterior 5 cm of the frontal cortex, respectively)¹. During electrical stimulation the patient is asked to answer a few questions to observe any change in speech at this moment. When stimulating motor areas, the patient is observed for involuntary movements in the regions corresponding to the areas stimulated, allowing the safe delimitation of the margins of the tumor to be resected.

This procedure is obviously contraindicated in patients with difficulty to speak (dysphasic), confused, extremely anxious, or with exaggerated response to pain, as well as those who need to be in a prone position (occipital tumors), with lesions affecting the dura mater (strong pain stimuli)⁷, and patients with morbid obesity or with a history of gastroesophageal reflux⁸.

The complications most commonly associated with this technique are agitation, dizziness, nausea, and seizures^9,10. Respiratory depression, with increased PaCO₂ that may reach 45 to 60 mmHg¹¹, leading to circulatory changes in the brain, which may make the surgical procedure difficult or impossible to make, may occur with the use of opioids.

General anesthesia is chosen because it provides comfort, can be interrupted for the cognitive testing following which the patient is anesthetized once again. When general anesthesia is used, the airways are maintained through tracheal intubation or a laryngeal mask. When the patient needs to be awake, the dose of the drugs is reduced, the patient is extubated or the laryngeal mask is removed, and the patient is capable to take part in the testing^4,5,7.

In this case, we chose to use general anesthesia initially, when invasive and painful procedures were done, such as puncture of the radial artery, insertion of a vesical catheter, and infiltration of the site of surgical incision with a local anesthetic. While under general anesthesia, the patient remained on assisted ventilation with a face mask. With this option, the patient remained comfortable, with a reduction in the time taken for his monitoring and preparation, allowing for prompt beginning of the surgical procedure. During the cognitive testing phase, when a tracheal tube or laryngeal mask is used and removed, the patient can awake agitated, disoriented, nauseous, and there may be respiratory depression and hemodynamic changes that can affect the brain circulation. These reactions may delay or even hinder the adequate evolution of the testing and culminate with the need for reintubation or reintroduction of the laryngeal mask.

Electro-stimulation is done with biphasic stimuli of 200 to 500 ms, lasting 2 to 5 s, with a frequency of 50 to 70 Hz. At this moment there is risk of seizures^1,5,7, with an incidence between 16% and 18% in awake craniotomies, as well as the incidence of nausea and vomiting in 8% to 50% of the patients⁵.

Dexmedetomidine, a drug that was initially restricted to sedation in intensive care units for no more than 24 hours, is currently increasingly used in Anesthesiology, both in sedation and as adjuvant of general anesthesia. It produces dose-dependent reduction in blood pressure and heart rate due to its actions on a₂-adrenergic receptors. Despite those effects, the intensity variation of the hemodynamic parameters observed in this case was minimal. Some studies have compared those changes to the ones observed with other associations of intravenous drugs, showing that the repercussions were less severe with dexmedetomidine^2,12,13. The small hemodynamic changes observed in this case are in agreement with the effects observed with infusion of low doses of dexmedetomidine in young adults¹³.

The use of dexmedetomidine almost eliminated the need to use adjuvant drugs to obtain satisfactory conditions for this surgical procedure, which has several benefits, such as lack of respiratory depression^4-8,14,15, provides hemodynamic stability without the need of vasopressor drugs, indicating that it can be used as the sole sedative medication. Confirming what was observed in this case, Mack et al. reported that dexmedetomidine allowed the realization of complex cognitive testing in 10 patients without complications⁴. However, Bustillo et al. did not have satisfactory results in the responses to cognitive tests in five patients. They were sedated with dexmedetomidine associated with fentanil and midazolam for intravascular embolization of cerebral arterial-venous malformation¹⁷. It wasn't clear why the goal was not achieved, unlike other reports^4,12,13,16. It seems that the reason lies in the drugs and doses used in relation to the intensity of the surgical stimulus. It also seems that patients with low surgical stimulation do not need doses higher than 0.05 mg.Kg^-1.h^-1. Besides the dose, it seems that the association of a₂-adrenergic drugs with benzodiazepines increases the sedation, and in the cases reported by Bustillo et al.¹⁷ fentanil was used as adjuvant in the beginning of the procedure¹⁸.

We presented a case of awake craniotomy without endotracheal intubation or insertion of a laryngeal mask, in which low doses of dexmedetomidine were used without complications. The use of general anesthesia in the beginning of the procedure using a face mask and dexmedetomidine to maintain sedation proved to be a safe method and capable of providing comfort for the patient. Surgical conditions were deemed ideal by the surgeons during the period of cognitive testing for mapping and tumor resection.

REFERENCES

Submitted for publication 17 de agosto de 2005

Accepted for publication 3 de abril de 2006

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*

Received from Hospital Clementino Fraga Filho, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ.

Publication Dates

• Publication in this collection
  24 July 2006
• Date of issue
  Aug 2006

History

• Accepted
  03 Apr 2006
• Received
  17 Aug 2005