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From the Department of Anesthesia, Toronto Western Hospital, University Health Network, University of Toronto, Toronto, Ontario, Canada.
Address correspondence to: Dr. Pirjo H. Manninen, Department of Anesthesia, Toronto Western Hospital, 399 Bathurst Street, Toronto, Ontario, M5T 2S8. Phone: 416-603-5118; Fax: 416-603-6494; E-mail: Pirjo.Manninen{at}uhn.on.ca
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Methods: This was a retrospective chart review of 100 consecutive patients treated by endovascular coiling compared with 100 patients treated by surgical clipping of a cerebral aneurysm. Information compared and analyzed included demographics, pre-procedure medical history, neurological status including location and size of aneurysm, anesthetic management, complications and patient outcome. P < 0.05 was considered significant.
Results: Patients in the INR group were older (54 ± 15 vs 49 ± 12 yr), had a greater incidence of pre-procedure cardiorespiratory problems (55 vs 34 patients) and had more aneurysms located in the posterior fossa (68 vs 11) (P < 0.05). General anesthesia was used in all except seven INR patients who received conscious sedation. There were some differences in the anesthetic agents and techniques. There was less monitoring of INR patients; temperature (33 vs 99 patients), intraarterial catheter (22 vs 100), central venous catheter (4 vs 78), and evoked potential monitoring (0 vs 100). There were no differences in the incidence of documented complications or in patient outcome.
Conclusion: There were some differences in the anesthetic management of patients undergoing endovascular treatment of a cerebral aneurysm compared with treatment in the operating room. The patients in the INR suite were sicker and somewhat older and they received less invasive monitoring, but the complication rate and outcome did not differ.
ENDOVASCULAR therapy is now an established therapeutic alternative to surgical clipping of some cerebral aneurysms.1–5 Initially, aneurysms that were surgically difficult to access, such as those situated in the posterior fossa, were treated by interventional neuroradiology (INR).6 As well, patients with high-risk medical conditions may benefit from INR as they need not be subjected to the more invasive technique of surgery.7 The most common endovascular treatment is by the insertion of Guglielmi detachable coils (GDC).1 In most institutions, an anesthesiologist is involved in the care of the patient during INR treatment.2,8–10 The roles of the anesthesiologist in the INR suite are to monitor the patient, to provide appropriate anesthesia to facilitate the procedure, and to manage any complication that may arise. The aim of this study was to review the overall anesthetic management of patients during the treatment of their cerebral aneurysm in the neuroradiology suite and compare this to the management in the operating room for surgical clipping of a cerebral aneurysm.
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. Patients in the INR group were older and had a higher incidence of cardiovascular and respiratory illness. There were no differences in the WFNS grade or of the size of aneurysms between the groups: small – INR 74, surgery 69; large – INR 17, surgery 18; giant – INR 9, surgery 13. More patients in the INR group had aneurysms located in the posterior circulation (Table I). Seventy procedures were performed on an emergency basis (23 INR, 47 surgery). The timing of the procedure following a subarachnoid hemorrhage was different between the groups: the mean (± SD) interval for the INR group was 9.7 ± 19.2 days and for the surgical group 4.4 ± 5.7 days, (P = 0.04). The anesthetic technique for the INR group was general anesthesia with tracheal intubation in all cases except for six patients who received neurolept anesthesia and one patient who had monitored anesthetic care. These seven patients were all of good neurological grade (Grade 1 (2) and intact (5)). One patient started with neuroleptanesthesia that was converted to general anesthesia 165 min into the procedure, because of excessive pain and discomfort. The procedure then proceeded uneventfully and coiling was successful. Twelve patients arrived from the intensive care unit (ICU) with an endotracheal tube in situ (INR 7, surgery 5). The anesthetic data are summarized in Table II. Propofol (n = 67) was used more commonly as an induction agent in INR whereas thiopental (n = 89) was used for surgery. Patients who underwent INR had a shorter duration of procedure and required less opioid and volatile anesthetic agents. Patients who had arrived with an endotracheal tube in situ were returned to the ICU for continuous ventilation of their lungs. Thirteen patients (INR 2 vs surgery 11, P = 0.02) had delayed awaking and were transferred to ICU for ventilation and tracheal extubation at a latter time. The two INR patients had both suffered an intracranial bleed during the procedure.
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). Blood pressure and/or heart rate was pharmacologically (esmolol, labetalol, metoprolol or hydralazine) lowered in 11 patients during INR and 10 patients during surgery. Blood pressure was increased by the administration of a vasoactive agent (ephedrine, phenylephrine, dopamine) in 9 INR patients and 29 surgical patients (P < 0.05). Induced hypotension was not used for any INR treated patient in this series and only for two surgical patients. A central venous catheter was in situ in four patients in the INR group. None were inserted in the INR suite. In the surgical group, four were in situ and 74 patients received a central venous catheter in the operating room. The most common site for central venous monitoring was the right internal jugular vein. Monitoring of cerebral function by somatosensory evoked potentials (SSEP) was used in the operating but not in the INR suite. Clinically important SSEP changes were documented in seven patients and six of them had a new neurological deficit postoperatively. Heparin use for anticoagulation was documented in 96 INR cases, and reversal with protamine was documented in 26 cases at the end of the procedure. Intravenous heparin was administered without the use of activating clotting times by giving a bolus dose (100 units•kg) followed by hourly additions of 1000 units. There were no major anesthetic complications documented in either group during the procedure. Post procedure, one patient from each group required unanticipated re-intubation after the procedures due to delayed recovery (surgery) and respiratory distress (INR). All INR group patients were treated with GDC coils. Procedure related complications included vascular perforation in four INR cases. Eight INR procedures failed to secure the aneurysm, of which four proceeded to surgery with fair to good outcomes. Of the four managed conservatively, three subsequently died of complications related to rebleeding. In the surgical group, clipping of the aneurysm was successful in all cases and none required further surgical or interventional management. Intraoperative rupture of the aneurysm was documented in 12 patients. These were controlled by tamponade effect or by use of temporary clipping. There were no significant differences in overall outcome at discharge between the two groups. A good to fair outcome (no major neurological deficits) was recorded for 88 INR and 94 surgical patients; poor outcome (major neurological deficits) in three INR and four surgery patients; eight INR and two surgery patients died.
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The indications for endovascular therapy are evolving.1,7,10,11 The initial use of INR for aneurysms was in situations where surgical treatment was difficult such as in the posterior fossa. The less invasive approach of INR may be a good alternative for elderly and patients with severe cardiorespiratory or systemic diseases.7,11 The management of our patients reflected these trends in that more patients with posterior fossa aneurysms and with cardiorespiratory disease were treated by INR. Early treatment of a ruptured aneurysm is the usual practice to decrease the incidence of rebleeding.12,13 In our study, INR patients had their procedures performed at a later date from their subarachnoid bleed than the surgical group. Since our hospital is a referral centre for INR, there could have been delays in the referral and transfer process. Another possible reason is that these patients had more medical problems which required stabilization before the procedure. In this retrospective review, we were unable to determine the definitive reason for the selection and the time of treatment for all patients that were treated by INR.
The technique of anesthesia used for INR procedures varies amongst institutions and is often influenced by the preferences of the neuroradiologist. Both neurolept/conscious sedation and general anesthesia have been described.8–11,14 During conscious sedation, the awake patient serves as an effective overall monitor of neurological status. Conscious sedation may also be more suitable for patients with systemic medical problems.11 Reasons for the use of general anesthesia during INR procedures include the length of time that the patient may have to lie still, as well as the repeated requests for absolute stillness (breath holding) for some of the radiological techniques such as road mapping. The definite reason for neurolept anesthesia in seven of our patients was not documented but, overall, it has been the preference of our neuroradiologists to have all patients under general anesthesia for treatment of cerebral aneurysms.
The principles of safe neuroanesthesia should be applied to all patients with a cerebral aneurysm whether it is in the operating room or the INR suite.12,13 In our study, some of the anesthetic agents and techniques used in the INR were different from those used in the operating room. The different choices of induction agent can be explained by the set up; in the INR suite thiopental is not kept as a pre-mixed solution, contrary to the operating room, and propofol is readily available. The total quantity of agents used reflects the differences in the duration of the procedures and the degree of "painful" stimulation. The optimal or the intended level of blood pressure during these procedures is difficult to assess from a retrospective review. We only analyzed the level of blood pressure during the maintenance phase and there was no difference. However, more patients required pharmacological agents to increase their blood pressure during surgery, implying that there were probably more episodes of hypotension in the operating room. The end-tidal CO2 was lower in the surgical patients. Mild to moderate hyperventilation is commonly used during a craniotomy to help decrease brain bulk to allow for surgical exposure. This would not be required during INR procedures. The ability to assess the neurological status of patients immediately at the end of the procedure is desirable. In our review, delayed awakening occurred more frequently in the surgical group, which may reflect the greater complexity of the procedure and anesthetic during surgery. The overall outcome at discharge did not differ, but the purpose of our review was not to assess completeness of the coiling or clipping of the aneurysm.
Monitoring standards for anesthesia in remote locations, such as the INR suite, should be no different from those in the operating room.15,16 All patients were monitored with an electrocardiogram, pulse oximetry, non invasive blood pressure, and capnography. However, there was a difference in other monitoring modalities in our study. There was a lack of monitoring of the patient's temperature in the INR suite. The reason for this can only be speculated on. The capacity to monitor temperature was always available, but not as conveniently located as in the operating room. This deficiency has now been rectified in our institution. More patients in the INR group had premorbid cardiorespiratory illness and yet, few had invasive monitoring. Routine invasive arterial monitoring for blood pressure was not used in the INR. Most of the patients who had an intraarterial catheter and all central venous catheters arrived with these lines in situ from the ICU. There were no major problems documented with blood pressure or fluid management in the INR. Induced hypotension was not used for any of these INR procedures. Central venous lines are useful for monitoring volume status and venous air embolism. Marked fluid shifts, blood loss and an air embolism are less likely to occur during INR treatment. The need for a central venous pressure monitoring is therefore less indicated in INR. The lack of invasive monitoring in our study population during INR did not appear to affect the management, the incidence of complications nor the outcome of our patients. SSEP are used as a neurophysiologic monitor during aneurysm surgery.17,18 In our surgical group, according to our routine practice, all patients were monitored with appropriate SSEP modalities. SSEP monitoring is feasible, though more complex in the INR suite.19,20 In our centre, it was not used in the INR suite due to space and logistical constraints.
There are certain limitations to this study. Being retrospective in design, data are limited to what was recorded in the medical records of the patient. Some complications and problems may not have been documented. It was not the intent of this study to examine the reasons for the best treatment choice of the patient with a cerebral aneurysm. A prospective, randomized trial would be needed in this regard.
In conclusion, the anesthetic management of patients with cerebral aneurysms differed in the INR suite compared with the operating room during surgical treatment. For the anesthesiologist one needs to be aware that the patient presenting for INR treatment may have more premorbid cardiorespiratory illnesses and may be older. In our study the INR patients received less invasive monitoring, but the complication rate and outcome did not differ. Further studies and developments in INR technology will help to guide in the anesthetic management of patients undergoing endovascular treatment of their cerebral aneurysm.
Accepted for publication December 11, 2000.
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2 Luessenhop AJ. Interventional neuroradiology: a neurosurgeon's perspective. AJNR 1990; 11: 625–9.[Medline]
3 Leber KA, Klein GE, Trummer M, Eder HG. Intracranial aneurysms: a review of endovascular and surgical treatment in 248 patients. Minim Invas Neurosurg 1998; 41: 81–5.[Medline]
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Brilstra EH, Rinkel GJE, van der Graaf Y, van Rooij WJJ, Algra A. Treatment of intracranial aneurysms by embolization with coils. A systematic review. Stroke 1999; 30: 470–6.
5 Nakstad PH. Review article. Interventional neuroradiology. Acta Radiologica 1999; 40: 344–59.[Medline]
6 Guglielmi G, Viñuela F, Duckwiler G, et al. Endovascular treatment of posterior circulation aneurysms by electrothrombosis using electrically detachable coils. J Neurosurg 1992; 77: 515–24.[Medline]
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13 Zander JF. Subarachnoid haemorrhage. Cur Opin Anaesthesiol 1999; 12: 503–9.
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Manninen PH, Chan ASH, Papworth D. Conscious sedation for interventional neuroradiology: a comparison of midazolam and propofol infusion. Can J Anaesth 1997; 44: 26–30.
15 Manninen PH. Anaesthesia outside the operating room. Can J Anaesth 1991; 38: R126–9.
16 American Society of Anesthesiologists. Guidelines for nonoperating room anesthetizing locations. Approved by House of Delegates October 1994. In: Park Ridge, IL: American Society of Anesthesiologists 2000 Directory of Members, 2000: 491.
17 Schramm J, Koht A, Schmidt G, Pechstein U, Taniguchi M, Fahlbusch R.. Surgical and electrophysiological observations during clipping of 134 aneurysms with evoked potential monitoring. Neurosurgery 1990; 26: 61–70.[Medline]
18 Manninen PH, Lam AM, Nantau WE. Monitoring of somatosensory evoked potentials during temporary arterial occlusion in cerebral aneurysm surgery. J Neurosurg Anesthesiol 1990; 2: 97–104.
19 Hacke W, Zeumer H, Berg-Dammer E. Monitoring of hemispheric or brainstem functions with neurophysiologic methods during interventional neuroradiology. AJNR 1983; 4: 382–4.[Abstract]
20 Hacke W. Neuromonitoring during interventional neuroradiology. Central Nervous System Trauma 1985; 2: 123–36.[Medline]
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