Keywords
flow diverter - anesthetic management - intracranial aneurysms
Introduction
Flow diverter (FD) placement is an endovascular technique where the flow to the aneurysm
is directed away from the aneurysmal sac by placing a stent in the parent vessel ([Fig. 1]). It also causes neo-intimal proliferation that completely occludes the inflow to
the aneurysm.[1]
[2] The indications for this device placement are complex aneurysm configurations, giant
aneurysms, fusiform, or wide-necked aneurysms, where both conventional coiling and
clipping are difficult to perform. Previous literature has demonstrated that the use
of the FD has high rates of aneurysm occlusion with relatively low complication rates.[3]
[4] Flow diversion leads to reduced hemodynamic stress velocity within the sac of the
aneurysm, which results in a reduced risk of re-rupture and better long-term occlusion.
The anesthetic concerns and the associated complications related to their placement
have not been studied earlier. In this case series, the authors share their institutional
experience pertaining to the periprocedural care and the clinical course of patients
with intracranial aneurysm requiring placement of FD.
Fig. 1 Digital subtraction angiography (DSA) images showing different stages of treatment.
(A) Pretreatment giant right-side ophthalmic segment internal carotid artery aneurysm.
Note the filling of aneurysmal sac. (B) Flow diverter in situ (white arrow) and reduced filling of sac. (C) Follow-up image showing reduced sac size.
Methods
After approval from institute ethics committee (IEC), the authors included all patients
who underwent endovascular therapy with placement of FD for intracranial aneurysms
from January 2014 to December 2017. Data regarding patient demographics, presenting
complaints, ruptured or unruptured aneurysm, its size, location, details of anesthesia
technique, and intra- and postprocedural complications were noted. Duration of hospital
stay, follow-up imaging data, and neurological outcome (as assessed by Glasgow outcome
scale [GOS]) at discharge and at 6 months were also noted. Data are presented as median
(range) or number (%).
Results
Over a period of 3 years, 22 patients having aneurysms at different sites underwent
FD placement procedures. The demographics, presenting complaints, and comorbidities
are listed in ([Table 1)]. All had unruptured aneurysms except two patients, who had recent history (3 and
7 days) of subarachnoid hemorrhage (SAH) at the time of presentation. All the aneurysms
were located in the anterior circulation ([Table 1]). During procedure, all patients received intravenous propofol as an agent for anesthesia
induction. The standard monitoring included electrocardiography, noninvasive blood
pressure monitoring, pulse oximetry, end-tidal carbon dioxide, skin temperature, and
urine output in all patients. In addition, arterial catheterization was performed
in all patients for carrying out beat-to-beat blood pressure monitoring. Most patients
received a combination of sevoflurane and nitrous oxide for maintenance of anesthesia
(20/22 [91%]). All patients received intravenous heparin during the procedure to maintain
an activated clotting time of 2 to 2.5 times the baseline value. The duration of the
whole procedure was 210 (120–325) minutes. One patient developed intraprocedural FD
thrombosis that was promptly taken care of by intra-arterial abciximab. Postprocedural
systolic blood pressure was kept in the range of 140 to 150 mm Hg. Five out of 22
patients were not tracheally extubated at the end of the procedure. The most common
indication for mechanical ventilation was delayed reversal due to hypothermia (4/5
[80%]). Postoperatively, two patients developed motor deficits that improved subsequently.
On postoperative day 2, one patient died of large parietal hematoma and increased
intracranial pressure. The median duration of hospital stay was 7 (5–20) days. At
discharge, the mean GOS was 4 in all patients, except one who had a GOS of 1 (died).
Follow-up digital subtraction angiography (DSA) showed small residual aneurysms in
4 of 21 patients. All patients who were followed up at 6 months (18/21) had a GOS
of 5. None of the patients developed any delayed complications related to FD and were
neurologically intact.
Table 1
Demographics and clinical characteristics of patients
|
Age (y)
|
50 (30–66)
|
|
Abbreviations: ASA, American Society of Anesthesiologists; F, female; ICA, internal
carotid artery; M, male; SAH, subarachnoid hemorrhage.
Note: Numbers expressed as median (range), number (%).
|
|
Sex (M:F)
|
3:18
|
|
Weight (kg)
|
60 (48–80)
|
|
ASA I/II/III
|
12/8/2
|
|
Comorbidities
• Hypertension
• Diabetes
|
8 (36.3)
1 (4.5)
|
|
Presentation
|
Headache
|
17 (77.2)
|
|
Vision impairment
|
7 (31.8)
|
|
Diplopia
|
4 (18.1)
|
|
Ptosis
|
2 (9.0)
|
|
Recent SAH
|
2 (9.0)
|
|
Aneurysm size
|
< 7 mm
|
6 (27.2)
|
|
7–12 mm
|
4 (18.1)
|
|
13–24 mm
|
6 (27.2)
|
|
≥ 25 mm
|
6 (27.2)
|
|
Location
|
Cavernous ICA
|
9 (40.9)
|
|
Clinoidal ICA
|
2 (9.0)
|
|
Ophthalmic ICA
|
7 (31.8)
|
|
Communicating ICA
|
1 (4.5)
|
|
Superior hypophyseal
|
3 (13.6)
|
Discussion
In this case series, the authors collected data regarding the periprocedural care
and the clinical course of patients with intracranial aneurysm requiring placement
of FD. The most common presenting symptom was headache due to mass effect of unruptured
aneurysm. One patient had a history of SAH, 3 months back, and other two patients
presented with recent SAH (at third and seventh days). From the recent evidence on
the use of FD in ruptured aneurysms, it has been observed that large aneurysms and
posterior circulation aneurysms have more risk of associated complications.[5] In this small series, all aneurysms were present in anterior circulation, and 72.7%
of these were greater than 7 mm.
The goals of anesthesia for FD placement are similar to those required for other intracranial
neurointerventional procedures. These include making the patient immobile during procedure,
maintaining stable blood pressure, managing anticoagulation, managing intraoperative
complications, early and prompt recovery, safe transport of patients, and following
radiation safety rules. The blood pressure goals have to be individualized based on
patient’s baseline value. In this series, there were few episodes of transient hypotension
and hypertension in some of the patients, which possibly did not require any active
management as no data on drug use were available. In cases of intraprocedural thrombosis,
a balance has to be maintained by keeping the blood pressure in high normal range.
Low blood pressures are avoided to maintain good cerebral perfusion. At the same time,
a very high blood pressure has to be avoided to prevent any hemorrhagic event as these
patients receive heparin intraoperatively and are on antiplatelet agents also.
In our institute for therapeutic neurointerventional procedures, we usually administer
general anesthesia (GA). As it is a relatively newer technique mostly used for difficult-to-treat
aneurysms, GA has been commonly used for carrying out these procedures in various
studies.[6]
[7] On the other hand, monitored anesthesia care allows for prompt detection of intraoperative
complications that otherwise can be appreciated only after extubation. In a retrospective
matched cohort study, authors found that placement of an FD can be safely performed
under conscious sedation and is associated with reduced procedure length. The rates
of procedural complications were comparable between both groups, and no complication
attributable to GA was recorded. However, for conscious sedation, the patient should
be cooperative; intervention should not be too complex; and an experienced operator
should perform the intervention.[8] In another study, monitored anesthesia care was used for daycare treatment of cerebral
aneurysms with the same-day discharge.[9] However, for this, patients should be carefully selected, and they should fulfill
the criteria for safe discharge. In this series, all patients received GA for carrying
out these procedures. Propofol was the most commonly used induction agent, and sevoflurane
in oxygen/nitrous mixture (40:60) was used as the maintenance agent in all except
two patients who received propofol infusion.
In addition to standard ASA (American Society of Anesthesiologists) monitoring, arterial
blood pressure monitoring was performed in all patients to titrate it closely. Peripheral
intravenous access usually suffices in all these patients, and central line is generally
not required. Bispectral index is useful for titrating the anesthetic depth in these
patients and may help in early recovery. Near-infrared spectroscopy provides information
about cerebral oxygenation and is a predictive marker of critical perfusion changes.[10]
Patients received dual-antiplatelet agents such as aspirin and clopidogrel 5 days
before procedure, and these are continued thereafter typically for 6 months similar
to common practice.[11] After a period of 6 months, clopidogrel is stopped and aspirin is continued for
rest of life. In addition, where priming was not possible, aspirin and clopidogrel
300 mg each were given 4 hours before procedure. However, the practice varies regarding
the optimal dose, agent, and timing of antiplatelet agent used. The use of antiplatelets
in acute SAH carries risk of aneurysmal rebleeding. In such cases, single dose of
aspirin and loading dose of GpIIb/IIIa inhibitor may be administered or a dose of
aspirin before procedure followed by clopidogrel at end of procedure.[12]
[13] At our institute, patients with recent-onset SAH received only postprocedural antiplatelets
(aspirin 75 mg OD, clopidogrel 150 mg). We did not perform aspirin and clopidogrel
response testing in any patient.
The periprocedural complications may vary from thromboembolic or ischemic events,
side branch occlusions, parent artery injury, and/or rupture and malposition or migration
of FDs.[14] These are associated with significant morbidity and should be recognized and treated
promptly. There were no intraoperative complications except in one patient who developed
FD thrombosis. As these acute thrombi are platelet-rich, antiplatelet agents such
as abciximab, tirofiban and eptifibatide are most effective for clot disruption. Blood
pressure may be augmented to tide over the period of acute thrombus formation. In
this case, it resolved promptly, and the patient was extubated post procedure. The
neurointervention suite is usually cold and 4 out of 22 patients developed intraoperative
hypothermia (34°C). These patients had inadequate reversal and were mechanically ventilated
postoperatively. One patient developed a large parietal hematoma post procedure and
succumbed to death on postoperative day 2. Blood pressure should be optimized such
as to prevent aneurysmal bleed, prevent aggravation of any brain edema, and to maintain
a good flow across the parent artery. However, this needs to be studied further, and
optimum goals need to be established.
The long-term safety and efficacy of FD is yet to be studied. A trial aimed to study
the effect of flow diversion versus traditional coil-based endovascular therapy comparing
the standard treatment with FD placement has been terminated because of the rarity
of disease and difficulty in enrollment.[15] In a meta-analysis, the authors concluded that the risk of procedure-related morbidity
and mortality cannot be neglected in FD placement. Patients with posterior circulation
aneurysms are at higher risk of ischemic stroke, particularly perforator infarction.
These findings should be considered when considering the best therapeutic option for
intracranial aneurysms.[4] We observed that one patient developed FD-related thrombosis of internal carotid
artery, which was promptly recognized and treated during procedure, which resulted
in an uneventful recovery. However, two patients in this case series developed postprocedural
mild motor weakness that subsequently improved over the next few months. After the
procedure, there may occur peri-aneurysmal vasogenic edema in the brain parenchyma,
more likely if aneurysm is large, partially thrombosed, or close to the brain parenchyma.[16]
[17] The proximity of the treated aneurysm to the brain parenchyma probably causes inflammation,
blood–brain barrier disruption, and edema formation. This may lead to aggravation
of headache or clinical deterioration. Few may prefer to administer dexamethasone
for 1 to 2 weeks to cover high-risk period; however, there are no clear recommendations
about it.[18]
In a randomized trial comparing flow diversion and best standard treatment—the FIAT
trial, the authors had to stop the trial due to safety concerns. The primary hypothesis
is that flow diversion can be performed with an “acceptable” immediate complication
rate, defined as less than 15% morbidity and mortality; however, they found out that
16% patients had either died or became dependent after FD placement.[19] In this study, progressive mass effect, periprocedural arterial rupture, carotid
thrombosis due to migration of FD, and delayed rupture were the predominant causes
of poor clinical outcome. Hence, the authors concluded that flow diversion was not
safe and effective as hypothesized. However, in this series, except for one patient,
others had a good functional outcome. Delayed aneurysm rupture and delayed intraparenchymal
hemorrhages (DIPHs) are often fatal complications of FD placement for intracranial
aneurysms. In one such study, the delayed ruptures accounted for 76.6% within 1 month
and the associated prognosis was poor.[20] In our experience, only one patient had a fatal hemorrhagic complication that occurred
immediately in the postprocedure period. However, we did not notice any DIPH. Thus,
the rate of complication in our series is only 4.5% as compared with 15 to 18% found
in the literature. The neurological outcome at discharge and at 6 months was good
(GOS 4/5) in 21 out of 22 patients (95.4%).
Conclusions
In this clinical report, we found that FD placement is an attractive, innovative,
and safe way of treating intracranial aneurysm with few rates of complication. The
neurological outcome was good in all patients who were followed at 6 months. Periprocedural
anesthetic and intensive care management of such patients requires updated knowledge
regarding the dynamics of the FS, anesthetic goals, and associated early and delayed
risks associated with them.
