Absolute Hemostasis

Arteriovenous malformation (AVM) resection should be bloodless, with sharp dissection of subarachnoid spaces, precise occlusion of pial feeders, clean dissection of parenchymal margins, and careful occlusion of deep supply along the ependymal plane. The slightest bleeding is meticulously stopped to maintain absolute hemostasis before progressing to the next step. Ironically, AVM resections are some of the cleanest and driest dissections despite their high-charged hemodynamics. Nonetheless, some intraoperative bleeding is inevitable with AVM resection, no matter how meticulous the dissection, how skilled the neurosurgeon, or how cooperative the AVM. Cauterizing dysplastic arteries with high flow will stir up bleeding that ranges from a small trickle from a pesky perforator to a torrent from nidal rupture. The threat of intraoperative rupture permeates these cases, and when it occurs, it can transform the operation. Blood suffuses the field and visualization is lost; suction must remain on the bleeder to clear the field and the sucker hand is immobilized; the resection stalls to reestablish hemostasis; the cause and site of the bleeding may be unclear; bleeding may force technical errors and morbidity from chasing the source into eloquent white matter; and AVM bleeding can be so brisk that it overwhelms the neurosurgeon and spirals out of control. Although AVM bleeding is unnerving, it must be met with a swift response to avert catastrophe.

The technical response to intraoperative AVM rupture differs from aneurysm rupture, which progresses through an orderly sequence of tamponade, suction, proximal control with temporary clipping, distal control with temporary clipping, and permanent aneurysm clipping. There is no aneurysm dome to tamponade with AVM bleeding, and there are too many feeding arteries for proximal control. There is no temporary clipping or neck to close. The bleeding source must be pursued, exposed, and controlled. A small cottonoid is applied at or near the bleeding site and suctioned to dry the field. A jet of blood is traced back to the source, which may be arterial, venous, or nidal.

Arterial Bleeding

Arterial bleeding originates from the parenchymal side of the resection bed, not from the nidus itself. A cottonoid prevents suction from injuring the brain, and some retraction pressure can be applied to the cottonoid with the sucker tip, allowing the sucker to be a dynamic retractor in the hunt. Small bleeders can be controlled with bipolar forceps and suction, suctioning right at the bleeding point or even drawing the artery into the barrel of the sucker. The sucker simultaneously clears the blood and immobilizes the bleeder, while the bipolar cauterizes the artery proximally. When cautery fails, I resort to microclips for small perforating arteries and aneurysm clips for large feeding arteries. Some arteries are thin, friable, and uncontrollable, but they become more manageable as they are exposed proximally. Therefore, intractable arteries are subdued by chasing them proximally, which requires deeper transgression into brain tissue and may jeopardize eloquent tracts or cortex. The pursuit of bleeders in subarachnoid spaces is safer, but there are risks to normal branches and bystander arteries.