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Recent studies have demonstrated that bedside cranial burr hole and insertion of intraparenchymal catheters for intracranial pressure monitoring performed by intensive care physicians is a safe procedure, with a complication rate comparable to other series published by neurosurgeons. The overall morbidity rate is comparable to, or even lower than, that caused by central vein catheterization. The procedure is also quite simple and modern disposable intracranial procedural kits are available. After the skin is prepped the land- mark for skin incision, called the 'Kocher's point', located about 2-A cm lateral to the midline (mid-pupillary line) and 2-3 cm anterior to the coronal suture, is found. Then the surgical field is prepared with the sterile drapes and the skin infiltrated with local anaesthetic (0.5% lidocaine with 1: 200 000 epinephrine). After skin incision and retraction of the skin and subcutaneous tissue, the periosteum should be scraped off in order expose the skull. The skin is then divaricated, exposing the underlying bone. The hole is drilled with either an electric drill or a twist drill (the drilling procedure must be performed with the drill held within 100 of the perpendicular position to the incision site). The hole is then irrigated with sterile saline and an 18-G spinal needle may be used to open the dura (exercise caution when perforating the dura so as to avoid damage to the underlying structures). Following opening of the dura, the Bolt, containing a stylet, is screwed manually into the skull at approximately 5 mm to 1 cm for adults. The stylet is then removed after the bolt has been screwed in, after which the bolt should be filled with saline. Finally, the zeroing of the transducer is performed by simply holding the tip in air while zeroing on the monitor. The transducer is inserted inside the bolt and the screw tightened. The intracranial pressure value can then be read. [ABSTRACT FROM AUTHOR]

Transcranial Doppler is an innovative, flexible, accessible tool for the bedside monitoring of static and dynamic cerebral flow and treatment response. Introduced by Rune Aaslid in 1982, it has become indispensable in clinical practice. The main obstacle to ultrasound penetration of the skull is bone. Low frequencies, 1-2 MHz, reduce the attenuation of the ultrasound wave caused by bone. Transcranial Doppler also provides the advantage of acoustic windows representing specific points of the skull where the bone is thin enough to allow ultrasounds to penetrate. There are four acoustic windows: transtemporal, transorbital, suboccipital and retromandibular. The identification of each intracranial vessel is based on the following elements: (a) velocity and direction; (b) depth of signal capture; (c) possibility of following the vessel its whole length; (d) spatial relationship with other vessels; and (e) response to homolateral and contralateral carotid compression. The main fields of clinical application of transcranial Doppler are assessment of vasospasm, detection of stenosis of the intracranial arteries, evaluation of cerebrovascular autoregulation, non-invasive estimation of intracranial pressure, measure of effective downstream pressure and assessment of brain death. Mean flow velocity is directly proportional to flow and inversely proportional to the section of the vessel. Any circumstance that leads to a variation of one of these factors can thus affect mean velocity. The main pathological condition affecting flow velocity is the vasospasm. Vasospasm is a frequent complication of subarachnoid haemorrhage, it often remains clinically silent and the factors that make it symptomatic are largely unknown. Threshold velocities above which vasospasm comes into place are well defined as regards the median cerebral artery, while there is no consensus for the other vessels. Nevertheless, an increase in velocity alone is not sufficient to arrive at a diagnosis of vasospasm; a condition of hyperaemia also presents with an increase in flow velocity. The Lindegaard Index has therefore been introduced, which is defined by the ratio between the mean flow velocity in the median cerebral artery and the mean flow velocity in the internal carotid artery. Criteria for diagnosis of a stenosis >50% of an intracranial vessel with transcranial Doppler include: (a) segmentary acceleration of flow velocity; (b) drop in velocity below the stenotic segment; (c) asymmetry; and (d) circumscribed flow disturbances (turbulence and musical murmur). The transcranial Doppler enables us to assess both components of self-regulation. The static component is measured by observing changes in flow velocity caused by pharmacologically induced episodes of hypertension and hypotension. The dynamic component of autoregulation can be measured using a method devised by Aaslid known as the 'cuff test'. A very effective and safe device for measuring cerebral autoregulation is the transient hyperaemic response test. This test is based on the compensatory vasodilatation of the arterioles, which occurs after brief compression of the common carotid. Csonyka proposed the following formula based on clinical observation for the calculation of cerebral perfusion pressure: CPP = MAP X FVd/FVm + 14. Brain death is defined as the irreversible cessation of all functions of the whole brain. The clinical criteria are usually considered sufficient to establish a diagnosis of brain death; however, they might not be sufficient in patients who have been on sedatives or when there are ethical or legal controversies. Many authors have demonstrated the existence of a transcranial Doppler pattern, which is typical of brain death. [ABSTRACT FROM AUTHOR]

Recent studies have demonstrated that bedside cranial burr hole and insertion of intraparenchymal catheters for intracranial pressure monitoring performed by intensive care physicians is a safe procedure, with a complication rate comparable to other series published by neurosurgeons. The overall morbidity rate is comparable to, or even lower than, that caused by central vein catheterization. The procedure is also quite simple and modern disposable intracranial procedural kits are available. After the skin is prepped the landmark for skin incision, called the 'Kocher's point', located about 2-4 cm lateral to the midline (mid-pupillary line) and 2-3 cm anterior to the coronal suture, is found. Then the surgical field is prepared with the sterile drapes and the skin infiltrated with local anaesthetic (0.5% lidocaine with 1 : 200000 epinephrine). After skin incision and retraction of the skin and subcutaneous tissue, the periosteum should be scraped off in order expose the skull. The skin is then divaricated, exposing the underlying bone. The hole is drilled with either an electric drill or a twist drill (the drilling procedure must be performed with the drill held within 10 degrees of the perpendicular position to the incision site). The hole is then irrigated with sterile saline and an 18-G spinal needle may be used to open the dura (exercise caution when perforating the dura so as to avoid damage to the underlying structures). Following opening of the dura, the Bolt, containing a stylet, is screwed manually into the skull at approximately 5 mm to 1 cm for adults. The stylet is then removed after the bolt has been screwed in, after which the bolt should be filled with saline. Finally, the zeroing of the transducer is performed by simply holding the tip in air while zeroing on the monitor. The transducer is inserted inside the bolt and the screw tightened. The intracranial pressure value can then be read.

Transcranial Doppler is an innovative, flexible, accessible tool for the bedside monitoring of static and dynamic cerebral flow and treatment response. Introduced by Rune Aaslid in 1982, it has become indispensable in clinical practice. The main obstacle to ultrasound penetration of the skull is bone. Low frequencies, 1-2 MHz, reduce the attenuation of the ultrasound wave caused by bone. Transcranial Doppler also provides the advantage of acoustic windows representing specific points of the skull where the bone is thin enough to allow ultrasounds to penetrate. There are four acoustic windows: transtemporal, transorbital, suboccipital and retromandibular. The identification of each intracranial vessel is based on the following elements: (a) velocity and direction; (b) depth of signal capture; (c) possibility of following the vessel its whole length; (d) spatial relationship with other vessels; and (e) response to homolateral and contralateral carotid compression. The main fields of clinical application of transcranial Doppler are assessment of vasospasm, detection of stenosis of the intracranial arteries, evaluation of cerebrovascular autoregulation, non-invasive estimation of intracranial pressure, measure of effective downstream pressure and assessment of brain death. Mean flow velocity is directly proportional to flow and inversely proportional to the section of the vessel. Any circumstance that leads to a variation of one of these factors can thus affect mean velocity. The main pathological condition affecting flow velocity is the vasospasm. Vasospasm is a frequent complication of subarachnoid haemorrhage, it often remains clinically silent and the factors that make it symptomatic are largely unknown. Threshold velocities above which vasospasm comes into place are well defined as regards the median cerebral artery, while there is no consensus for the other vessels. Nevertheless, an increase in velocity alone is not sufficient to arrive at a diagnosis of vasospasm; a condition of hyperaemia also presents with an increase in flow velocity. The Lindegaard Index has therefore been introduced, which is defined by the ratio between the mean flow velocity in the median cerebral artery and the mean flow velocity in the internal carotid artery. Criteria for diagnosis of a stenosis >50% of an intracranial vessel with transcranial Doppler include: (a) segmentary acceleration of flow velocity; (b) drop in velocity below the stenotic segment; (c) asymmetry; and (d) circumscribed flow disturbances (turbulence and musical murmur). The transcranial Doppler enables us to assess both components of self-regulation. The static component is measured by observing changes in flow velocity caused by pharmacologically induced episodes of hypertension and hypotension. The dynamic component of autoregulation can be measured using a method devised by Aaslid known as the 'cuff test'. A very effective and safe device for measuring cerebral autoregulation is the transient hyperaemic response test. This test is based on the compensatory vasodilatation of the arterioles, which occurs after brief compression of the common carotid. Csonyka proposed the following formula based on clinical observation for the calculation of cerebral perfusion pressure: CPP = MAP x FVd/FVm + 14. Brain death is defined as the irreversible cessation of all functions of the whole brain. The clinical criteria are usually considered sufficient to establish a diagnosis of brain death; however, they might not be sufficient in patients who have been on sedatives or when there are ethical or legal controversies. Many authors have demonstrated the existence of a transcranial Doppler pattern, which is typical of brain death.