Intra-operative investigations using sterile disposable 16 MHz probes1)
Using this method, it is possible not only to detect the route of the blood flow, the flow direction and flow rate in all branches, but also to detect the local hemodynamic in the region of the anastomosis.
This permits intra-operative assessment of the anastomosis quality and of its different anastomosis techniques. Stenosis at the site of anastomosis, which may lead to acceleration of the blood flow rate, are expected in the case of end-to-end anastomosis. This is also true for end-to-side anastomosis with concealed incision of the lateral branch.
Transcutaneous pre-operative and post-operative Doppler sonography of the cervical vessels and post-operative monitoring of the route and flow in an extra-intracranial anastomosis are standard investigation techniques in the event of occlusions.
During surgery, the method is applied transcutaneously to locate the afferent artery and to measure the route and the flow of the blood. With extra-intracranial anastomosis, the thrombosis or the stenosis usually appears during operation. They are not visible externally and can be tracked by Doppler sonography.
Bypass of large aneurysms
Doppler measurements at the site of the anastomosis with controlled constriction of the cervical carotid artery up until the start of an adequate flow provide the best basic prerequisites for a well-functioning bypass and decrease the risk of an ischemia due to unnecessary high-grade stenosis.
Despite the excellent possibilities of microsurgery, occlusions and stenosis can be developed unintentionally in the afferent or adjacent vessels while the aneurysm is being clipped, and these may not be easily detected. Incomplete clipping with risk of post-operative bleeding is also possible.
Doppler sonography can be used to assess the state of the afferent vessels and to monitor clipping of the aneurysm.
Intra-operative monitoring (microvascular Doppler)
Microvascular Doppler permits intra-operative monitoring of specific blood vessels to check their status during difficult interventions. With its small probe size and measurement range, this system offers the best basic prerequisites for taking useful measurements during operation.
1) disposable 16 MHz probes are currently in accreditation process and will be available in the End of year 2012.