Department of Anaesthesia, Atkinson Morleys Hospital, Copse Hill, Wimbledon, London SW20 0NE, UK 1 Present address: Department of Anaesthesia, St Marys Hospital, Praed Street, London, UK
Corresponding author. E-mail: judith.dinsmore@btinternet.com LMA® is the property of Intavent Limited.
Accepted for publication: October 2, 2002
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Abstract |
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Methods. The records of all patients who had awake craniotomy at our institution were reviewed. Patients were divided into three groups according to anaesthetic technique. Patients in Group 1 were sedated throughout the procedure. Patients in Groups 2 and 3 had an asleepawakeasleep technique. Those in Group 2 were anaesthetized with a propofol infusion and fentanyl, and breathed spontaneously through a laryngeal mask airway (LMA). Patients in Group 3 had total i.v. anaesthesia with propofol and remifentanil, and ventilation was controlled using an LMA. We noted the incidence of complications in each group.
Results. There were 99 procedures carried out between 1989 and 2002. Group 3 had the fewest complications. No patients in Group 3 developed hypercapnia (E'CO2 >6 kPa), compared with all of the patients in Group 2. Patients in Group 1 had no E'CO2 monitoring, but 7% developed airway obstruction. No patients in Group 3 required additional analgesia for pain, compared with 70% of patients in Group 2.
Conclusions. We have developed a technique for craniotomy, which facilitates awake neurological testing, is safe, and has good patient satisfaction.
Br J Anaesth 2003; 90: 1615
Keywords: anaesthetic techniques; complications; surgery, craniotomy
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Introduction |
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One neurosurgeon at our institution regularly performs awake craniotomies for tumours near functional areas of the brain. This has given us the opportunity to develop a technique which fulfils these requirements, provides good operative conditions, and is acceptable to the patient. We reviewed all patients who had awake craniotomy, and describe the evolution of this technique, the incidence of complications, and the quality of the awake period.
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Methods |
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Complications were classified as anaesthetic: inadequate or excessive sedation, pain, nausea or vomiting; respiratory: oxygen saturation <90%, increase in E'CO2 (>6 kPa), hypoventilation (<8 bpm), or airway obstruction; haemodynamic: systolic blood pressure <80 or >170 mm Hg, or heart rate <40 or >110 beats min1; or neurological: convulsions, brain swelling or development of a new neurological deficit.
Patients were placed into one of three groups depending on the anaesthetic technique used (Table 1). The majority of cases were anaesthetized by one of four anaesthetists, and the anaesthetic technique was modified over the years from providing a type of conscious sedation to a true asleepawakeasleep technique. There were never any anaesthetic protocols, but it became obvious on reviewing the patient records that there were three main anaesthetic techniques. All patients received dexamethasone i.v. and anticonvulsants for seizure prophylaxis during the preoperative period. They were not premedicated and monitoring consisted of electrocardiogram (ECG), SpO2, E'CO2, and invasive arterial pressure. The operative site was infiltrated with a mixture of bupivacaine 0.25% and lidocaine 0.5% in Groups 1 and 2, and with bupivacaine 0.5% in Group 3.
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Group 2
This technique was modified in 1996 by the use of the laryngeal mask airway (LMA). This allowed better control of the airway, a means of assessing adequacy of respiration via the E'CO2 trace, and the ability to control ventilation if the need arose. When the tumour was located, the propofol was stopped, the LMA was removed, and the patient was allowed to wake up. For closure of the surgical incision, the propofol infusion was restarted and the LMA reinserted. These patients received fentanyl, but not droperidol or midazolam.
Group 3
Our present technique is a true asleepawakeasleep technique. Additional monitoring is provided by using bispectral index score (BIS). Patients receive total i.v. anaesthesia with a target-controlled infusion of propofol and a remifentanil infusion. An LMA is inserted and ventilation controlled until the tumour is exposed. The rates of propofol and remifentanil are adjusted in response to changes in the haemodynamic variables, the response to surgical stimulation, and the BIS. The remifentanil infusion and artificial ventilation allow control of PCO2 based on arterial blood gases, providing good operative conditions. All patients receive acetaminophen 1 g p.r., diclofenac 75 mg i.v., unless contraindicated, and ondansetron 4 mg i.v.
When the tumour is exposed, the remifentanil is reduced until spontaneous respiration resumes. The LMA is then removed. The propofol infusion is stopped and the patient allowed to waken (Fig. 1). A background infusion of remifentanil of 0.0050.01 µg kg1 min1 is used to provide additional analgesia during the awake period. When tumour resection is complete, the patient is re-anaesthetized and the LMA replaced. Ventilation is again controlled until completion of surgery. Patients are given morphine up to 10 mg for postoperative analgesia before returning to the recovery room.
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Results |
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The anaesthetic records were missing from the patient notes in five cases, and it was difficult to obtain accurate information on the incidence of anaesthetic complications in some of the earlier patients. The patients in Group 1 remained sedated throughout the awake period, but there were no documented problems with pain, excessive sedation, or of lack of patient cooperation. Twenty-four patients in Group 2 received supplementary fentanyl during the awake period for discomfort during tumour resection. One patient in Group 2 was restless and uncooperative and had to be re-anaesthetized. No patients in Group 3 complained of pain (Table 2). One procedure in Group 3 had to be abandoned because of excessive sedation, but this same patient underwent repeat awake craniotomy the following week, without complications. Nausea or vomiting was not reported in any group.
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There were no haemodynamic complications in Group 1, but this was based on limited anaesthetic notes. Two patients in Group 2 and four patients in Group 3 had transient hypotension after induction of anaesthesia or on local anaesthetic infiltration. Four patients in Group 2 had episodes of hypertension during closure of the craniotomy, requiring treatment with labetalol. Two patients in Group 2 developed intraoperative seizures (Table 2). In one patient, this resulted in a prolonged post-ictal period and the procedure was abandoned. Three patients in Group 2 and one patient in Group 3 developed mild neurological deficits.
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Discussion |
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In the USA, the majority of these procedures are performed under local anaesthesia with sedation, and it has been suggested that this should be a standard approach to certain supratentorial tumours.9 A shorter hospital stay and shorter use of high dependency facilities result in considerable cost reductions and some centres are even advocating day-case procedures.10 In the UK, there is reluctance from both patients and surgeons to perform these procedures under local anaesthetic, and the depth of sedation required in many cases is associated with an increased incidence of complications. Over-sedation not only results in an uncooperative patient, but may also lead to respiratory depression. Any increase in PaCO2 may result in cerebral swelling.
Many anaesthetic techniques have been described for awake craniotomy. Neurolept analgesia is associated with excessive sedation and a higher incidence of pain and convulsions.11 The patients in our first group were sedated using propofol infusions and several studies have endorsed this technique. Propofol was associated with a decreased incidence of convulsions but with a higher incidence of respiratory depression.2 The use of the LMA has also been described previously for awake craniotomy.3 7 When combined with a propofol infusion, it is well tolerated and provides a method of airway control in case of respiratory depression.
The combination of remifentanil and propofol has been used successfully for awake craniotomy, but in spontaneously breathing patients.4 5 Remifentanil has a very short half-life, which is independent of the rate of infusion, and allows rapid control of the depth of anaesthesia. In addition, it provides greater haemodynamic stability. However, these patients also develop respiratory depression. We decided to use the respiratory depression produced by remifentanil to control ventilation to a desirable PaCO2 during the asleep period. The safety of the LMA for controlled ventilation has been the subject of recent discussion, but we have had no problems with its use in carefully selected patients.12
Patients who might benefit from awake neurological testing are selected by the neurosurgeon. Any potential medical problems are discussed with the anaesthetist who then contacts the patient for further review. A good rapport between the patient and the anaesthetist is essential. The only absolute contraindication to this technique is an uncooperative patient. Patients with oesophageal reflux, the very obese, and those with large vascular tumours all pose potential problems. If there are any doubts as to patient suitability, the decision to proceed is made after discussion between the anaesthetist, the surgeon, and the patient. The anaesthetic technique is then changed as necessary. Patients are counselled before the operation and have the opportunity to talk to other patients who have had an awake craniotomy. Those who decide to proceed with surgery tend to be very motivated and have a positive attitude to the whole procedure, which may also account for their quick recovery.
Despite our observations that the clinical conditions were superior in Group 3, poor record keeping and difficulty in assessing complications retrospectively made this difficult to prove. The most striking difference is the incidence of hypercapnia in Group 2 (Table 2). Interestingly, despite raised PaCO2 values in these patients with intracranial pathology, clinical conditions were thought to be acceptable in the majority of cases. However, the expectations of both anaesthetists and surgeons have changed over the years. Our surgeons now expect an awake and cooperative patient, and good intraoperative conditions. This was achieved in 95% of the procedures in Group 3, with high patient satisfaction (Marsh and Murphy, personal communication). All these patients were discharged within 1 week, with three discharged within 3 days. Our incidence of complications compares favourably with other groups (Table 3).
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References |
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