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Endovascular pulmonary artery inflatable balloon-induced hypotension: A novel technique for clipping giant intracranial aneurysms
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/neuroindia.NI_301_16
Management of giant intracranial aneurysms presents unique challenges to the neurosurgical team. Various techniques such as adenosine-induced hypotension, rapid ventricular pacing, and inducing deep hypothermia are described in the literature to effect circulatory arrest for the successful obliteration of giant aneurysms. We describe a novel technique of induced hypotension for clipping a giant aneurysm by using an inflatable balloon across the main pulmonary artery with a successful outcome. This technique has not been described earlier in the literature. Keywords: Giant aneurysm, induced hypotension, inflatable balloon
Surgical obliteration of giant aneurysms often requires adjuncts such as circulatory arrest achieved by adenosine, rapid ventricular pacing, or extracorporeal circulation.[1] We suggest an alternative method of using an inflatable balloon across the main pulmonary artery to achieve this goal with a desirable outcome.
A 50-year old female patient presented with progressive visual loss in both her eyes of 2 month duration. On evaluation, she had perception of light only in the right eye, with 6/18 vision in the left eye. Magnetic resonance imaging (MRI) of the brain and subsequently, her computed tomography (CT) angiography revealed a giant aneurysm of left A1 segment of the anterior cerebral artery (ACA) without any thrombus, that was projecting inferiorly and causing compression of both the optic nerves and chiasm [Figure 1]a,[Figure 1]b,[Figure 1]c. Digital subtraction angiogram showed complete filling of the aneurysm from the left A1 segment close to the A1-A2 junction [Figure 1]d. A diagnosis of giant unruptured left A1 segment aneurysm was made and different treatment options were considered. In view of the optic nerve compression with gross visual defects, surgical obliteration was preferred over endovascular coiling.
As it was a giant, wide-necked aneurysm, collapsing the sac prior to clip reconstruction of the parent vessel was considered mandatory. Due to the inferior projection of the aneurysm, it was considered surgically difficult to gain control over the contralateral A1 segment of the ACA. Thus, various options such as adenosine-induced transient asystole, rapid ventricular pacing, and deep hypothermic circulatory arrest were evaluated. As each of these techniques had its own merits and demerits, after discussion with the cardiologist, we considered the feasibility of balloon occlusion of the inferior vena cava (IVC) and the main pulmonary artery (MPA) to induce transient hypotensive circulatory arrest. Surgery After induction of general anaesthesia, the right subclavian vein was cannulated with a 7-French triple lumen, central venous catheter and a sheath was inserted into the right internal jugular vein to pass a stimulating catheter connected to an external pacer (to perform a rapid ventricular pacing in the event of our technique failing to produce adequate hypotension; or, to pace the heart in the event of any circulatory arrest that may happen following injection of adenosine). The left radial artery was cannulated with a 20G cannula to monitor the intra-arterial blood pressure. A 14-French sheath was inserted through the right femoral vein and a Coda balloon (Cook Medical, Bloomingdale, IN, USA) was inserted and placed initially in the IVC-right atrial junction under fluoroscopic guidance by the interventional cardiologist [Figure 2]a. Following inflation, the mean arterial pressure (MAP) reduced to 40 mmHg. However, the rate of reduction in blood pressure was slow and was not considered to be sufficient enough to be effective in keeping the operative field free of blood in the event of a premature rupture of the aneurysm. Hence, the balloon was advanced to the MPA and inflated [Figure 2]b. The MAP rapidly reduced to zero and was considered ideal for this aneurysm.
A standard left pterional craniotomy was done, and after the durotomy, a distal-to-proximal Sylvian dissection was performed without using frontal lobe retraction (to avoid premature rupture of the aneurysm owing to its inferior projection). The internal carotid artery (ICA) bifurcation and proximal A1 were exposed. The aneurysm was seen filling the interoptic cistern and its further visualization was not be possible in view of the large size of its fundus. Despite generous gyrus rectus resection, the neck of the aneurysm and the distal A1 and A2 could not be delineated. Hence, a bolus dose of propofol was given for burst suppression and the Coda balloon was inflated in the MPA. The MAP came down to zero, following which the sac was punctured [Figure 3]a and [Figure 3]b and a quick dissection was performed to delineate the neck of the aneurysm to facilitate clip placement. A 15-mm straight titanium clip was passed perpendicular to the parent vessel and a booster clip was applied distal to the initial clip. Another 11 mm curved clip was passed from under the surface of A1 to complete the neck obliteration [Figure 3]c. The whole procedure was completed in 1 minute 13 seconds. There was sinus bradycardia (heart rate of 34/minute) towards the end of the procedure and the balloon was then deflated. The electrocardiogram returned to normal sinus rhythm and there was reactive hypertension (MAP of 140 mmHg) that lasted for 4 minutes. Indocyanine green (ICG) angiography confirmed total occlusion of the aneurysm and normal filling of the parent vessels [Figure 3]d. The fundus was further dissected and collapsed [Figure 3]b to ensure decompression of the optic apparatus [Video 1].
Postoperatively, the patient recovered uneventfully without any fresh neurological deficits. She was extubated and monitored in a neurointensive care unit for 72 hours and later shifted to the ward. Postoperative CT angiography showed complete occlusion of the aneurysm with normal filling of the parent vessel [Figure 4]a,[Figure 4]b,[Figure 4]c,[Figure 4]d. She was discharged in a stable condition after 7 days.
Giant aneurysms constitute 5% of intracranial aneurysms and pose a significant challenge during their surgical obliteration. Most of these aneurysms are wide-necked and thick-walled, thereby increasing the complexity of successful clip reconstruction.[1],[2],[3],[4] Various options are available for the microsurgical elimination of giant aneurysms such as conventional clipping and clip reconstruction of parent vessel, trapping the aneurysm with cerebral bypass, and parent vessel ligation.[1],[2] Successful clip reconstruction warrants collapse of the sac to facilitate neck dissection and careful passage of clip blades so as to prevent the clip from slipping out or occluding the parent vessel. Collapsing the sac requires significant hypotension, which is more than what can be safely achieved with routine pharmacological measures and anesthetic maneuvers. Deep hypothermic circulatory arrest This can be achieved by a femoro-femoral bypass and extracorporeal circulation under deep hypothermia. However, various complications may be associated with this procedure including cerebral ischemic injury, postoperative bleeding due to heparinization, and femoral vessel complications, all of them leading to a poor neurological outcome. The procedure also prolongs the operative time and thereby increases the cost and the postoperative infective complications.[1],[2],[3],[4],[5] Hence, it is not widely used nowadays. Adenosine-induced hypotension Intravenous adenosine (0.3–0.4 mg/kg) can induce a brief period of circulatory arrest of up to 45 seconds. It has a short half-life, and thus recovery of the normal circulation is achieved without additional medications. However, it has considerable dose-response variability and should be avoided in patients with severe obstructive airway disease, coronary artery disease, and those with cardiac conduction abnormalities.[6],[7] Rapid ventricular pacing in cerebral aneurysms The use of rapid ventricular pacing (RVP) in Neurosurgery was first described in 1971 by Rovit for intracranial aneurysms;[8] however, it has not been used very often. Recently, there is a resurgence of this technique for giant aneurysms. In contrast to adenosine, RVP-induced hypotension has an almost immediate “on-off” effect, has a predictable duration, and is not affected by patient related factors, such as asthma and heart block. However, it can cause sustained ventricular fibrillation.[8],[9],[10],[11] Inflatable inferior vena cava/pulmonary artery balloon-induced hypotension As all the above mentioned techniques have some limitations, we propose a novel technique of an endovascular inflatable balloon placed inside the main pulmonary artery to induce transient hypotension to permit vascular interventions, for periods lasting for around 1 minute. It produces an abrupt reduction in the MAP by reducing the preload, and thereby the cardiac output. This technique has the potential to supersede the above-mentioned techniques because of its almost instantaneous on-off phenomenon; the cuff inflation produces the desired amount of fall in blood pressure in less than 3 seconds, causing significant reduction in the turgidity of the aneurysm, which facilitates its clipping. The problems that the anaesthetist should be aware of during the conduction of this procedure are the development of arrhythmias, severe bradycardia, and hypotension. Cuff deflation can rapidly reverse these cardiovascular disturbances. In short, the precise control over physiology is the major advantage of this technique over the previously described techniques, which are not so reliable in terms of their onset, duration, and reversibility of actions. However, this technique adds on to the cost of the procedure because it requires an interventional cardiologist, C-arm fluoroscopy, and the Coda balloon. There is also a theoretical risk of pulmonary artery dissection or rupture, damage to the tricuspid valve, and ventricular fibrillation due to prolonged balloon inflation. To conclude, inflatable balloon-induced hypotension can be used as a safe modality in well-equipped centres, for surgical management of giant intracranial aneurysms. Utilizing a multidisciplinary team, it can serve as an alternative to adenosine administration and rapid ventricular pacing. Acknowledgements The authors sincerely thank Dr. Bashi V. Velayudhan, Director and Senior Consultant, Cardiothoracic Surgery, SIMS Hospital for conceptualizing this management strategy practised by him for the last 15 years to bring down the blood pressure to apply side-biting clamp on the ascending aorta while performing proximal vein graft anastomosis in off-pump coronary artery bypass surgery; and, Dr. Nishanth Sampath, Junior Consultant, Clinical Neurophysiology for his assistance in the manuscript preparation and submission. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3], [Figure 4]
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