intra-operative aneurysm rupture
Craniotomy for clipping of a cerebral aneurysm risks include: injury to a major artery (anterior cerebral, anterior communicating, middle cerebral, posterior communicating, posterior cerebral, etc...), injury to a perforating artery, retraction injury, vasospasm, injury to the optic nerve (when clinoid drilling is required), and movement of an aneurysm clip.
Many of the complications of craniotomy for aneurysm clipping are common to all craniotomies:
Table: Neurosurgical Risks & Complications
Complications particular to craniotomy for cerebral aneurysm clipping include:
intraoperative aneurysm rupture
Aneurysmal rupture is a risk of any surgery to clip.
Intraoperative aneurysm rupture can occur during dissection around the aneurysm to expose it, during manipulation of the aneurysm, or spontaneously apparently unrelated to forces, direct or indirect, exerted on the aneurysm. Occasionally rupture can occur during the craniotomy, during cutting and elevation of the bone flap, dural incision and tenting, etc. Intraoperative
Intraoperative aneurysm rupture can be caused by a number of factors:
Anesthesia -- mechanical:
Intubation with forcible flexing of the neck and placement of an endotracheal tube can cause sudden elevation of blood pressure that could presumably provoke bleeding from an unclipped aneurysm.
Anesthesia -- pharmacology:
Sudden elevation in blood pressure due to failure to adequately anticipate for causes of these (such as placement of head fixation pins, insertion of lumbar drain, etc. could presumably provoke aneurysmal bleeding prior to or during setup and craniotomy.
Surgeon -- planning:
Depending on the direction that the aneurysm points, the size and configuration of its neck and dome, its relation to surrounding vessels and other structures the neurosurgeon plans a trajectory and exposure least likely to disturb the portion(s) most likely to rupture. Poor planning can contribute to intraoperative aneurysm rupture.
Surgeon -- judgment:
When preparing to place a clip on the aneurysm the surgeon must usually create a space for the clip around the neck of the aneurysm. The appropriate size and shape of the aneurysm clip are important in proper placement without precipitating a rupture.
Surgeon -- technique:
During clip placement disturbing the aneurysm can cause it to rupture. A clip improperly placed may dislodge with hemorrhage from the now unsecured aneurysm.
Patient -- anatomy:
Unusual patient anatomy not anticipated based on preoperative angiogram or other imaging may cause the surgeon to miscalculate during the exposure or clipping possibly precipitating intraoperative rupture.
Patient -- disease:
Aneurysms vary in their size and in the thickness of the their dome (the site most likely to rupture).
Life threatening:
If the surgeon cannot quickly stop the bleeding the patient can lose enough blood to become hypotensive and have a cardiac arrest. Usually even brisk bleeding from an intraoperative rupture can be controlled by a combination of pressure at the site of bleeding and, if this fails, application of "temporary" aneurysm clips on one or more of the arteries upstream (proximal), flowing into, the aneurysm.
Neurologic deficit:
If a massive amount of blood is released into the subarachnoid space during an intraoperative rupture the patient will be at high risk of subsequent vasospasm with possible secondary ischemia and infarction (stroke). Depending on the location, severity, and extent of the vasospasm the patient can have lesser or greater, transient or permanent, limited or extensive neurologic deficit.
Injury to an important vessels in the process of controlling intraoperative aneurysm can also lead to infarction and similarly, to neurologic deficit of greater extent, severity, or duration.
Prolongation of surgery: The maneuvers required to stop an intraoperative hemorrhage can take a long time, especially when blood and fluid coat the operative field obstructing the surgeon's vision making further dissection and manipulation hazardous and forcing him or her to work more deliberately and slowly.
Reoperation: Once the surgeon has controlled the hemorrhage he or she can usually clean up the blood sufficiently to proceed with clipping. Sometimes hemorrhage is complicated by acute reactive swelling of the surrounding brain that makes exposure of the aneurysm impossible. It may be necessary to close and return at a future time once the brain swelling has decreased enough to allow the surgeon once again to safely dissect and maneuver around the aneurysm.
Intraoperative management of an aneurysm rupture includes tamponade (pressure with a cottonoid pattie) and possible temporary clipping of the feeding artery (or arteries). Once the bleeding is under control the surgeon returns his or her attention to clipping the aneurysm.
If tamponade and temporary clips fail to control bleeding other options include isolation and ligation or clipping of the major feeding artery (carotid) and possibly administration (by anesthesia) of medications to drop the patient's arterial blood pressure (induced hypotension). Decreasing the patient's blood pressure will of course compromise blood flow to the entire brain and increases the risk of stroke.
The frequency of intraoperative aneurysm rupture during a craniotomy for clipping is ---
Monitoring:
The anesthesiologist monitors the patient's blood pressure throughout opening, dissection, and aneurysm clipping to help reduce the risk of intraoperative rupture.
Pharmacology:
Blood pressure control may require the administration of blood pressure-lowering medications.
Planning:
The surgeon usually approaches an aneurysm along a trajectory that avoids manipulation of the dome (most likely to bleed or presumed site of bleeding) as much as possible.
Technique:
Intraoperative aneurysm rupture during a craniotomy for clipping is less likely if manipulations at and around the dome of the aneurysm are kept to a minimum, and if necessary, avoided until proximal control (description of procedure) is secured.
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Multiple aneurysm clips required to completely eliminate a complex anterior circulation (carotid) aneurysm
Irritation of cerebral arteries lying on the surface of the brain by blood breakdown products in the cerebrospinal fluid of the subarachnoid space can cause these vessels to decrease in diameter (vasospasm) resulting in decreased blood flow through them and potential ischemia and infarction of the tissues they supply.
Intraoperative:
Vasospasm may be noted intraoperatively following craniotomy with clip ligation of aneurysm
Immediate post operative:
vasospasm following craniotomy with clip ligation of aneurysm
Delayed post operative:
Vasospasm occurs usually between the third and eleventh day post-subarachnoid hemorrhage.
Delayed:
Vasospasm following clip ligation of a cerebral aneurysm rarely occurs beyond 2 weeks after a subarachnoid hemorrhage.
The pathophysiology of vasospasm is incompletely understood but seems to be related to irritative effects of hemoglobin from red blood cells on arterial smooth muscles.
Life threatening:
Vasospasm following craniotomy with clip ligation of a cerebral aneurysm can be a life threatening complication if it is associated with ischemia and swelling of the brain with increased intracranial pressure.
Neurologic deficit:
Vasospasm following craniotomy with clip ligation of aneurysm typically presents clinically with a neurologic deficit (such as weakness on one side of the body -- hemiparesis, or inability to speak -- aphasia).
Neurophysiologic compromise:
Vasospasm following craniotomy with clip ligation of aneurysm can lead to swelling of the brain with increased intracranial pressure and herniation of brain tissue.
Reoperation:
vasospasm following craniotomy with clip ligation of aneurysm
Intraoperative:
Vasospasm that is noted intraoperatively during following craniotomy with clip ligation of aneurysm
vasospasm following craniotomy with clip ligation of aneurysm occurs frequently but with varying degrees of neurologic deficit. Sometimes vasospasm is found on angiography in a patient with no neurologic deficit.
Berry aneurysms (the most common and the most commonly clipped) occur at junctions between branches of the major intracranial arteries supplying the brain (anterior circulation [internal carotid, cerebral arteries {anterior, middle, posterior communicating, ...}], posterior circulation [vertebral, basilar, superior cerebellar, posterior cerebral]).
Intraoperative:
Injury to a major artery during surgery to clip a cerebral aneurysm that creates a defect (hole) in the vessel can result in intraoperative bleeding that is brisk and difficult to control. If occlusion is the only method that controls the bleeding an iatrogenic stroke downstream in the distribution of the injured vessel can result in ischemia and infarction (stroke).
Immediate post operative:
Because the effects of a stroke in the distribution of a major cerebral artery are so neurologically dramatic, injury to major artery with occlusion is usually detected within a few hours of recovery or arrival in the ICU.
Surgeon -- technique:
Surgical technique is primarily culpable in the majority of injuries to a major artery during surgery to clip aneurysm. The surgeon can injure an artery by too vigorous dissection and manipulation and/or by using inappropriate instruments to perform these maneuvers. Poor clip placement can injure the wall of an artery near the aneurysm neck.
Patient -- anatomy:
Peculiarities of the patient's brain and/or arterial anatomy are not usually the cause of injury to a major cerebral artery during surgery to clip aneurysm because the surgeon can visualize these either preoperatively (angiogram) or intraoperatively and adjust his or her surgical maneuvers accordingly.
Patient -- disease:
More severe subarachnoid hemorrhage can predispose to swelling of the brain which makes retraction, dissection, and exposure more difficult and may therefore predispose to injury to a major artery during surgery to clip aneurysm.
Death complicating clipping of a cerebral aneurysm
Death following clipping of a cerebral aneurysm usually occurs within several hours but delayed complications such as wound infection can get out of control and occasional kill a patient.
Death following clipping of a cerebral aneurysm can be due to a number of causes singly or in combination.
Infarction with cerebral swelling and increased intracranial pressure, herniation and death.
Compression by extra-axial hematoma with associated cerebral swelling, herniation, and death.
Death is very uncommon following cerebral aneurysm clipping. Anesthetic techniques the surgical microscope and improvements in cerebrovascular microsurgery and technical training.
Some patients are so sick and some aneurysms so difficult that not all deaths following aneurysm clipping are preventable. The best prevention is to follow standard protocols for hemodynamic optimization, control intracranial pressure, and monitor for post op hematoma and/or edema formation.
intra-operative aneurysm rupture
compromise of flow parent artery
A
Perforating arteries are small vessels that take off at right angles from the main cerebral arteries. Perforators are the primary blood supply for some eloquent (functionally important) brain structures such as the caudate nucleus (supplied by the recurrent artery of Huebner usually a perforator of the anterior communicating artery) and thalamus (supplied by the thalamostriate perforators that come off of the posterior cerebral artery
Noticed usually in ICU as somnolence, confusion, slow to awaken from anesthesia.
Surgeon misjudges the location of the artery and inadvertantly coagulates and divides it as part of the dissection to approach an anterior communicating artery aneurysm.
The consequence of injury to a perforating vessels depends on the structures being supplied by that vessel.
The frequency of injury to a perforating artery during clip ligation of a cerebral aneurysm is ___
Prevention of injury to a perforating artery
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Aneurysm clips are two metal blades of variable length and thickness (to occlude the necks of the range of aneurysm sizes) connected by a spring mechanism than provides the force necessary to keep the aneurysm neck occluded in the face of systolic pressure within the cerebral artery from which the it arises.
Migration of an aneurysm clip is typically detected on a post operative imaging study. Clip opening is the most likely diagnosis (pending imaging confirmation) in a patient with sudden onset of headache and neurologic deficit following aneurysm clipping.
Migration can occur in the acute post operative phase or weeks or months or even years following surgery.
If the forces pushing the clip blades are less than those pushing between them at the neck of the aneurysm, the blades will separate allowing the neck to open and blood to escape from the artery through the neck to the dome and then into the subarachnoid space (subarachnoid hemorrhage).
If the blades of the clip are poorly placed they risk slipping even without forces applied to push them apart.
Clip migration can occur without aneurysm rupture and subarachnoid hemorrhage. A displaced clip is sometimes an incidental unexpected finding on a CT or angiogram performed after aneurysm clipping for a number of indications not related to clip location (rule out post subarachnoid hemorrhage hydrocephalus, subdural hematoma, etc.)
Clip migration requires re-operation only after repeat angiogram demonstrates residual aneurysm with a potential for re-rupture.
The frequency of clip migration is very low. The force applied the blades is usually much more than that from within the artery.
Clip movement is prevented by placement of the correct clip in terms of length and thickness with respect to the aneurysm neck to be occluded.
If the blades of an aneurysm clip are inadvertently placed across the parent vessel (vessel from which an aneurysm arises) there can be elimination of all flow with resultant stroke.
Compromise of flow through a parent artery during clip ligation of a cerebral aneurysm
Compromise of flow through a parent artery during clip ligation of a cerebral aneurysm
The cortex is liable to injury by any one or combination of several mechanisms. These injuries can complicate intraoperative dissection and post operatively may evolve into foci of cortical irritation that can be a focus of seizure activity.
Intraoperative:
injury to cortex during surgery to clip aneurysm
Immediate post operative: injury to cortex during surgery to clip aneurysm
Delayed post operative: injury to cortex during surgery to clip aneurysm
Delayed: injury to cortex following craniotomy with clip ligation of aneurysm
Neurologic deficit
Prolongation of surgery
Bleeding from the pia is not fast but sufficient blood collects to drip into the surgical field and interfere with visualization of instruments and structures. Controlling the bleed
Wait and observe.
Will either get better without intervention or it won't.
No known intervention.
Diuresis and possibly steroids in the short term post op until swelling due to retraction resolves
Retraction of brain tissue is necessary to expose the artery with the aneurysm on it.
In order to expose an aneurysm for clipping the brain above and around it must be moved out of the way.
Retraction injury is usually discovered post-operatively
Intraoperative:
retraction injury
Immediate post operative:
retraction injury
Delayed post operative:
retraction injury
Retraction injury during clip ligation of cerebral aneurysm is usually caused by an underestimation of the amount of pressure brain tissue can tolerate before it becomes ischemic and/or mechanically injured.
The consequence of retraction injury durign
Irreversible: retraction injury
Intraoperative: retraction injury
Acute post operative: retraction injury
Long term: retraction injury
The frequency of brain retraction injury during craniotomy for clip ligation of aneurysm is ___
Monitoring: retraction injury following craniotomy with clip ligation of aneurysm
Pharmacology: retraction injury following craniotomy with clip ligation of aneurysm
Equipment: retraction injury following craniotomy with clip ligation of aneurysm
Planning:
Retraction injury following craniotomy for clip ligation of aneurysm can be avoided by limiting the time and force of retraction.
injury to optic nerve by clinoid drilling and removal
The anterior clinoid process must be removed to provide adequate maneuvering room for placement of an aneurysm clip on most ophthalmic segment aneurysms. Some internal carotid artery aneurysms also require that the clinoid be removed. The optic nerve lies just lateral to the clinoid. The bit that drills away the clinoid ends up within a millimeter or so of the medial portion of the optic nerve.
Injury to optic the optic nerve by during clinoid drilling and removal is usually recognized intraoperatively. The intraoperative impression of optic nerve injury with the drill bit is confirmed in the immediate post operative by the patient with blindness in the same side (ipsilateral) eye on when examinable (conscious and cooperative) in Recovery or ICU.
Injury to the optic nerve during clinoid removal to access an internal carotid artery aneurysm can be caused by problems with the high speed drill.
The consequence of injury to the optic nerve during clinoid drilling
Irreversible:
Injury to the optic nerve by an errant clinoid drill bit may result in irreversible blindness.
Intraoperative:
If a trauma is recognized at the time it occurs intraoperatively an attempt can be made to mitigate the effects of edema by administration of steroids. Other than possibly steroids there is no known effective medical or surgical treatment for optic nerve injury due to clinoid drilling and removal.
Acute post operative:
injury to optic nerve (clinoid drilling)
Long term:
An injury that has not shown any functional improvement by 3 to 6 months post injury is not likely to show any thereafter. Patients should be informed that their blindness may be permanent so that they can get on with life adjustments necessary to live with the disability.
The frequency of injury to the optic nerve during clinoid drilling
A drill that jumps or toggles is dangerous and should be refused by the surgeon.
Planning: injury to optic nerve (clinoid drilling)
Technique: