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Frontal GBM: Incision, Craniotomy, Burr hole and Managing Air Embolism

January 15, 2016


This video describes three important techniques. Number one, principles of craniotomy, including incision and placement of burr holes. Number two, management of intraoperative venous air embolism. And number three, use of fluorescein fluorescence for guiding GBM resection. This is the case of one of my patients who presented with a seizure, and on MRI evaluation, was noted to have a parasagittal ring enhancing lesion, with some edema, just anterior to the centrolobule. Further evaluation and staging of his tumor revealed no other findings elsewhere. Therefore, this tumor was suspected to be a primary high-grade glioma. Patient underwent his surgery in a supine position. You can see placement of the skull clamp, linear incision across midline. After the skin has been prepped once, I use local anesthetic with epinephrin, to inject the incision, and then re-prep the incision, and then to drape the incision. Early infiltration of the skin provides ample amount of time for vasoconstriction of the scalp vessels, potentially decreasing the volume of blood loss. You can see the head is above the level of the heart. And the most common position for venous air embolism is actually the supine position, because supine position is most not commonly used for performance of craniotomies. The incision is draped. The operator should always have a high index of suspicion for presence of venous air embolism. After draping is complete, incision is extended to the level of the skull. I use the belly of the knife, not its tip. And not angled, rather perpendicular to the level of the scalp, so that the closure of the skin is more readily accomplished, while approximating the edges of the skin during closure. Following completion of the incision, hemostasis is achieved via bipolar forceps. For smaller incisions, I may not use Raney clips. Self-retaining retractors are positioned. Monopolar cutter is used to reflect the pericranium. And a burr hole is placed over the superior sagittal sinus. One may place the burr hole on both sides of the sinus. Here's the sagittal suture. The burr hole is placed over the sinus. Let's go ahead and review the principles for placement of the burr hole. You can see that that burr is perpendicular, and not in an angle, because the side-cutting burr can actually injure the dura, and tear the sinus. But the tip of the drill is quite safe and blunt. You can see the outer cortical bone is removed, the cancellous bone is also removed, and here is the inner table of the skull. Now I pay special attention, and remove the bone in smaller layers. Here, you can see the inner table of the calvarium. Generous burr hole is placed, so visualization through the burr hole is possible. Here, you can see the roof of the sinus. The burr hole is further widened, so that the number three Penfield dissector can be used effectively to dissect the sinus and the dura, away from the inner skull bone. Here is the use of Kerrison rongeurs to remove the inner aspect of the burr hole, so that the entire circumference of the burr hole is efficiently used. Here's the use of the angle, number three Penfield dissector, to remove the adherent bands on the wall and roof of the sinus, away from their inner skull. Moderate, to small amount of bleeding is usual and related to intradiploic veins, connecting to the dural venous sinus. The footplate is, at all times, perpendicular to the surface of the skull. Sharp turns are avoided. The drill may be toggled back and forth so that the tip of the footplate can be used as a dissector to mobilize the dura away from the inner aspect of the skull. Here, you can see a wide turn. Usually, I perform the final cut over the dural venous sinus, so if bleeding is encountered, the bone flap can be efficiently elevated to control the bleeding. As the bone flap was elevated, the patient had some decrease in his blood pressure. CO2 started to rise. I immediately cover the area of the superior sagittal sinus with gel foam, and also attempted to seal any retrograde sanctioning through the cancellous bone, at the edges of the cranium, and then flooded the field with irrigation fluid, and also used a large lap sponge, which was wet, to cover the area of dural exposure. Subsequently, the patient's head was lowered, so that blood pressure can be treated, and the patient can be stabilized. Here, you can see the lowering of head of the patient, the use of large lap sponge. The anesthesiologist is working with the surgeon, to assure that the blood pressure is increasing, and all the parameters are moving in the right direction. After the patient is stabilized, the head is left at a lower level than the heart. This sponge is slowly removed, and the areas of bleeding are dealt with. As the head of the patient is now lower the level of the heart, the source of retrograde air embolism, would become the points of bleeding. And I continue using the bone wax to wax the cancellous bone, and also seal off any bleeding from the superior sagittal sinus, or the venous lakes. After the bleeding is dealt with, the patient's head is carefully elevated. You can see that this area over the dura can be a source of tear, and venous bleeding, and retrograde air embolism. Patient was subsequently stabilized, and venous bleeding was controlled, and the dura was opened in a curvilinear fashion. You can see removal of the enhancing tumor using fluorescein fluorescence, under Yellow 560 module. Following gross total removal of the tumor, small residual fragments, under fluorescein fluorescence, are removed. Relatively good demarcation between the tumor, and the peritumoral white matter is evident. During enclosure, we encountered another episode of venous air embolism, and the patient's head, again, was lowered. A large, wet lap was used to cover the area of the dura and craniotomy. You can see the head of the patient is lower than the heart. Again, the bone wax and thrombin-soaked gel foam were used to seal off all the points of retrograde air sanctioning, through non collapsible veins, close to the dural venous sinus and cancellous bone. After the patient was stabilized, pieces of Surgicel and Fibrillar were used to cover the dura, and seal off any sources of venous air embolism. The bone flap was replaced, as you can see here. Postoperative MRI demonstrated gross total resection of mass, without any complicating feature, and the patient recovered from his surgery adequately. Thank you.

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