Medicion no invasiva de la saturacion cerebral de oxigeno en voluntarios normales, mediante espectroscopia cercana al infrarrojo / Non invasive measurement of the oxygen cerebral saturation in normal voluntaries, by mean of spectroscopy with near infrared light

Se practicaron mediciones de la saturacion de oxigeno cerebral regional (rSHbO2), mediante espectroscopia de luz cercana al infrarrojo, no invasiva, a fin de determinar los valores medios en una poblacion voluntaria normal habitando a nivel del mar. Seleccionamos 100 voluntarios normales de diferente sexo y edades a los cuales se les midio la rSHbO durante un periodo de 5 minutos a una frecuencia de 4 tomas por minuto, en cada lado de la region frontal. se utilizo el INVOS 3.100 (Somanetics Corp) para la medicin no invasiva de la rSHbO2. Se obtuvieron valores que se corresponden con otros promedios logrados por metodos invasivos. Concluimos que este metodo ofrece sensibilidad para la medicion de la rSHbO2, haciendolo util y de facil aplicacion en el monitoreo continuo no invasivo de la rSHbO2 en Neuroanestesia y Cuidados Intensivos

[Surgical treatment of giant cerebral arteriovenous malformations]. / Tratamiento quirúrgico de las malformaciones arteriovenosas cerebrales gigantes.

Despite advances in the surgical management of cerebral arteriovenous malformations (AVMs), giant (AVMs (greater than 5 cm] are still considered unsuitable for direct surgical resection by most neurosurgeons. Some of the lesions are being treated with embolization, or embolization followed by surgical excision. Embolization alone is not curative and carries potential risks of neurological deficit as well involves multiple procedures. Fourteen patients with giant AVMs underwent surgical resection without prior embolization. Four of the AVMs were located primarily in the frontal lobe, two in the temporal lobe, one each in the parietal and occipital lobes, while six AVMs were localized to two lobes (temporal-occipital or parietal-occipital). Four patients had associated aneurysms with the arteriovenous malformation. Eight patients presented primarily with seizures. One of these had multiple subarachnoid hemorrhages while another had symptoms suggestive of transient vertebrobasilar ischemia. Two patients had one or more subarachnoid hemorrhages. The primary complaint in the remaining four patients was headache with other associated symptoms. The patients with AVMs involving the optic radiation have had varying degrees of visual field deficit not interfering with their function. There were no deaths and only three patients had deterioration of neurological function. One of these three had an intra cerebral hemorrhage secondary to an associated aneurysm rupture. We feel that the majority of these giant AVMs are amenable to direct surgical excision. It is difficult to asses, from the literature, the benefit of embolization prior to surgical excision in cases of giant AVMs. At least in one report dealing with combined treatment of seven giant AVMs, some authors stressed that preoperative embolization did not significantly alter the blood flow and, hence, potential of bleeding at the time of operation. Blood loss has not been a significant problem in our experience. When there is an associated aneurysm, it should be treated prior to or at the time of excision of the malformation.

Biomechanics of vascular occlusion in neurosurgery.

Principle factors involved in effective vascular occlusion were identified and incorporated into a computer program designed to calculate the minimal occlusion force (MOF) in accordance with a modified version of Laplace's law. In vivo, the carotid arteries of 14 guinea pigs were occluded for one hour at an experimentally determined MOF or MOF + 50. A good correlation was found between the computed MOF and the experimentally determined MOF. Scanning electron microscopic (SEM) examination of the endothelium of the occluded vessels revealed extensive damage with forces greater than the MOF.

Aneurysm clip testing meter.

The force that a vascular clip exerts when it is applied to a vessel is a critical factor in its safe and proper use. Permanent occlusion effected in the obliteration of aneurysms requires clip closure forces great enough to resist sliping, yet low enough not to damage the neck of the aneurysm. The authors consider the need for a device that can readily measure clip closing forces just prior to pre-surgical sterilization (immediately prior to implantation), and an instrument that meets that need is presented.