… The truth behind organ donation & organ transplants
The Nasty Side of Organ Transplanting.
Some comments on special techniques by Dr David Wainwright Evans
Cerebral angiography is an old and quite dangerous technique for demonstration of blood flow in the major arteries and veins inside the skull. It involves the injection of a radio-opaque contrast medium (often known colloquially as “dye”) into the carotid - and, maybe, the vertebral - arteries. This contrast medium is not radioactive. Its presence in the intracranial vessels can only be ascertained by taking X-ray pictures from several angles. It is a relatively insensitive technique because the thick bony skull poses problems for X-ray imaging and, crucially, because quite a lot of contrast has to get into the intracranial (i.c.) vessels to guarantee a “shadow” on the film. It is, therefore, easy enough to see things like displacement of well-filled vessels (e.g. in cerebral tumour etc.) but difficult or impossible to rule out some blood flow in some parts of a generally swollen brain. It is entirely possible for an angiogram to be reported as showing no evidence of i.c. flow although there may be just enough oxygenated blood getting through to keep brain tissue in some areas alive (cf. Coimbra’s “ischemic penumbra”). For these reasons - and because the technique may exacerbate the brain damage or even cause fatal collapse in the X-ray room (shades of the apnoea test ….) - cerebral angiography has never been a popular investigation where so-called “brain death” is concerned, even in those centres where the technique is readily available.
By contrast radioisotope studies do, as their name suggests, use radioactive tracer substances in their attempt to detect intracranial blood flow. This, also, is a relatively insensitive means of demonstrating minimal flows - for many of the same reasons - but it is much less dangerous (though not generally available). Doppler flow studies, which use ultrasound, are even safer but still less reliable. Some centres use these techniques, chiefly in research studies aimed at justifying the clinical diagnosis of “brain death", but they have never been popular here and are not required for the diagnosis of “death for transplant purposes” on the basis of the Department of Health’s “Code of Practice”. Were they to be carried out on some of those certified “dead” under those rules, it is exceedingly likely that some would show evidence of persisting i.c. blood flow - an additional and very powerful reason not to use such “confirmatory techniques”. The same is true of elegant EEG techniques which look for “evoked potentials” - demonstrable responses to various stimuli which may indicate that there is still functional activity in, for example, brain stems which have been declared “dead”.
Other sensitive diagnostic techniques, such as magnetic resonance imaging, are being developed and may well have the power to detect continuing life in brains pronounced “dead” on the basis of the simple bedside tests in current use.