Key-words:
Adenosine-induced asystole - adenosine-induced profound hypotension - basilar artery
aneurysm - basilar trunk aneurysm - clipping - middle cerebral artery bifurcation
aneurysm - multiple intracranial aneurysms
Introduction
Microsurgical clipping of basilar artery aneurysms is technically challenging as the
surgical corridors for temporary clip application are narrow and deep. Adenosine enhances
the safety of clipping these aneurysms by providing transient asystole or profound
hypotension during clipping.[[1]] We describe successful clipping of a distal basilar trunk aneurysm during adenosine-induced
profound hypotension (AIPH).
Case Report
History and examination
A 46-year-old male presented with a history of sudden severe headache 1 week back,
one episode of seizures followed by altered sensorium and right hemiparesis for 2
days. The patient was drowsy and Glasgow Coma Scale (GCS) was E4V4M6. The patient
had right hemiparesis (Medical Research Council grade – 4/5).
Imaging features
Computed tomography (CT) revealed diffuse subarachnoid hemorrhage (SAH) (Fisher's
Grade III) with blood predominantly in interpeduncular fossa. CT angiogram revealed
wide-necked distal basilar trunk aneurysm arising from the basilar trunk between the
origin of the left superior cerebellar artery (SCA) and posterior cerebral artery
(PCA) and pointing to the left [[Figure 1]]. There was ectatic dilatation of distal basilar trunk between the origins of SCAs
and PCAs. Small bilobed left middle cerebral artery (MCA) bifurcation aneurysm was
also noted. Ruptured aneurysm was probably distal basilar trunk aneurysm as blood
was predominantly in interpeduncular fossa close to basilar artery aneurysm.
Figure 1: (a-c) Preoperative computed tomography angiogram showing distal basilar trunk aneurysm
arising between the origin of the left posterior cerebral and the left superior cerebellar
arteries, ectatic dilatation of distal basilar trunk between the origin of superior
cerebellar arteries and posterior cerebral arteries, bilobed left middle cerebral
artery bifurcation aneurysm (arrow in A). (d-g) Postoperative digital subtraction
angiography (DSA) showing successful clip ligation of distal basilar trunk and middle
cerebral artery bifurcation aneurysms
Operation and postoperative course
Both the aneurysms were planned for clipping in one session. Cardiac workup and clearance
for adenosine-induced transient asystole (AITA) was taken. Approach to distal basilar
trunk aneurysm was left subtemporal and for the left MCA bifurcation aneurysm was
left pterional [Video 1]. Total intravenous anesthesia with propofol and fentanyl
infusion was used for better brain relaxation. Large frontotemporal craniotomy suitable
for both the approaches was performed. It was decided to clip the ruptured distal
basilar artery aneurysm first. Surgery was performed in supine position. Head was
fixed in Sugita clamp and turned 90° to the right for the left subtemporal approach
for basilar trunk aneurysm. Transcutaneous pacemakers were placed. Basilar trunk proximal
to the aneurysm was exposed for managing inadvertent rupture of aneurysm during dissection.
Basilar trunk aneurysm was wide necked with a thin wall and was projecting laterally.
The distal basilar trunk between the origins of SCAs and PCAs was ectatic. Both options
of clip application parallel to basilar trunk with curved/angled clip and perpendicular
to basilar trunk with straight/slightly curved clips were considered [Video 1]. Perpendicular
clipping with slightly curved clip (FE-752K-Aesculap, Yasargil, 8.3 mm standard curved
clip) was considered to be the safe clipping technique for this aneurysm [Video 1].
Thiopentone (150 mg) was given just before AITA for cerebral protection. Single bolus
6 mg of adenosine was given and aneurysm was successfully clipped during AIPF (systolic
<60 mmHg) without application of temporary clip. Another booster clip of same size
was applied. There was no asystole and only transient profound hypotension for around
20 s was recorded with 6 mg adenosine. There were no complications related to AIPF.
Ectatic dilatation of the distal basilar trunk was wrapped with Teflon fluff and covered
with fibrin glue. Later, the left MCA bifurcation aneurysm was clipped in the same
session. Optimal position for clipping of MCA bifurcation aneurysm (head rotation
to the right by 30°) without changing the drapes could be achieved by rotating the
Sugita head frame and table. Two clips (FE740K-7 mm std. straight clip and FE710K-5
mm mini straight; Aesculap, Yasargil) were used to clip the bilobed MCA bifurcation
aneurysm [Video 1]. Postoperatively, the patient remained drowsy for a few days. The
patient's sensorium and right hemiparesis gradually improved over the next 2 weeks.
Check angiogram (digital subtraction angiography (DSA)) done before discharge revealed
successful clip ligation of both the aneurysms [[Figure 1]]. At a follow-up of 3 months, the patient's sensorium was normal (GCS-E4V5M6) and
the right hemiparesis improved significantly (4+/5).
Discussion
AITA or AIPH facilitates safe clipping of aneurysms when temporary clip placement
is difficult.[[2]],[[3]],[[4]],[[5]],[[6]],[[7]],[[8]] It is a much simple and safe technique of providing temporary flow arrest or profound
hypotension during aneurysm surgery compared to deep hypothermic cardiac arrest or
rapid ventricular pacing.[[2]],[[7]] Adenosine binds to cardiac A1 receptors and prolongs the conduction through atrioventricular
node by decreasing the activity of adenylate cyclase.[[7]] The major disadvantage of AITA/AIPH is the very short duration of asystole or profound
hypotension as the half-life of adenosine is only 10 s and is rapidly cleared from
circulation.[[2]],[[3]],[[4]],[[5]],[[6]],[[7]] The duration of AITA/AIPH is difficult to predict.[[2]],[[3]],[[4]],[[5]],[[6]],[[7]],[[8]] Considering these limitations, AITA/AIPH should be used only when temporary clip
placement is difficult.[[5]],[[7]] AITA/AIPH facilitates clipping of basilar artery aneurysms as narrow and deep surgical
corridors make application and removal of temporary clip relatively difficult, and
temporary clip may obscure the operating view of these aneurysms.[[1]],[[7]] Other indications for AITA/AIPH include early intraoperative rupture before proximal
and distal control, insufficient control with temporary clip, synergistic to temporary
clip application in achieving complete flow arrest, giant/complex aneurysms with difficult
anatomy for temporary clip placement, and atherosclerotic proximal vessel.[[2]],[[3]],[[4]],[[5]],[[6]],[[7]],[[8]] AITA is a safe technique, and complications are extremely uncommon.[[2]],[[3]],[[4]],[[5]],[[6]],[[7]],[[8]] Various complications reported include atrial fibrillation, prolonged bradycardia/asystole,
and ventricular tachycardia. AITA should be avoided in patients with coronary artery
disease, cardiac dysrhythmias, bronchial asthma, and gout.
After the first description of the use of adenosine for clipping a basilar apex aneurysm
in 1999 by Groff et al., safety and efficacy of adenosine during microsurgery for
intracranial aneurysms has been reported in various reports.[[1]],[[2]],[[3]],[[4]],[[5]],[[6]],[[7]],[[8]],[[9]] Wang et al., in their literature review of AITA for intracranial aneurysms, found
that there was a wide variation in the dose of adenosine given (initial dose of adenosine
given ranged between 6 and 12 mg/0.2 and 0.4 mg/kg and median dose of adenosine between
12 and 78 mg) for inducing AITA and in the median duration of AITA (8–57 s).[[7]] Both test incremental method (starting with 6 or 12 mg adenosine and additional
doses based on the response) and estimated dose injection method (0.3–0.4 mg/kg given
in precalculated manner) have been described.[[8]] Powers et al. reported escalating doses of adenosine (6, 12, 18, 24, and 36 mg)
to determine the dose of adenosine that would cause 30 s of asystole.[[6]] Predetermining the dose of adenosine that causes considerable duration of AITA
by escalating doses and using that dose during clipping will expose the patient to
multiple episodes of transient asystole and can cause complications secondary to brain
ischemia, especially in patients with acute SAH similar to the present case.[[4]],[[8]] In the present report, we decided to give an initial dose of 6 mg of adenosine
after keeping the clip ready for clipping at the neck of the aneurysm. We decided
to apply the clip once there is profound hypotension or asystole with 6 mg of adenosine
and use higher doses if there is no AITA/AIPH with this dose. Profound hypotension
was achieved with 6 mg of adenosine in this patient and aneurysm was successfully
clipped during this period.
Endovascular treatment for both distal basilar trunk and MCA bifurcation aneurysms
in this patient will be far more expensive than surgical treatment in a developing
country like India due to very high device cost of material (hardware, microcatheter,
guidewires, coils, stents, flow diverters, etc.) required for endovascular treatment.[[9]] The patient's family opted for surgical clipping as they could not afford expensive
endovascular treatment. Clipping of both the aneurysms in a single session was performed
in this patients as multiple intracranial aneurysms is a high-risk condition requiring
prompt and early treatment of both ruptured and unruptured (silent) aneurysms, and
poor outcome due to subsequent fatal bleeding from silent aneurysms following clipping
of only ruptured aneurysms was reported.[[10]] Clipping of both the aneurysms was done for free of cost under the state government
health scheme in this patient. Although endovascular treatment is preferred to clipping
for basilar artery aneurysms at many centers, clipping is a reasonably safe and cost-effective
treatment option for these aneurysms in developing countries.
Conclusion
AITA or AIPH enhances the safety of clipping basilar artery aneurysms in narrow and
deep surgical corridors as temporary clip placement is difficult in these cases.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form the patient(s) has/have given his/her/their consent for his/her/their
images and other clinical information to be reported in the journal. The patients
understand that their names and initials will not be published and due efforts will
be made to conceal their identity, but anonymity cannot be guaranteed.
