… The truth behind organ donation & organ transplants
The Nasty Side of Organ Transplanting.
Some comments by Dr David Wainwright Evans
We are talking about severe, usually traumatic, brain injury. There will be parts of the brain which have been destroyed by the injury itself, by the extravasation of blood or by total deprivation of blood supply - due to rupture or occlusion of critical vessels perhaps but also because the blood supply to the brain as a whole becomes compromised by the rise in intracranial pressure (due to the brain swelling/oedema which accompanies the initial trauma). The “global ischemic penumbra” of which Coimbra speaks is that potentially very large part of the brain (hence the term “global”) which has not been destroyed by the interruption of circulation but is nevertheless so severely compromised by it (i.e. getting such an absolutely minimal trickle of blood - just enough to keep it alive but not enough to allow it to function) that it shows no sign of life (is functionless for the time being) and will die if the circulation is not restored very quickly or if it is not somehow protected from the effects of anoxia while the supply of oxygen and nutrients remains inadequate. There are treatments aimed at protecting this apparently functionless and severely compromised brain tissue from further ischemic damage during the crucial few hours after the index injury. They include drugs and hypothermia and they work by limiting or actively reducing the swelling (so that some blood can get into the skull against the elevated intracranial pressure which tends to keep it out) and by reducing the demand for oxygen and nutrients while the blood flow is critically inadequate. This latter is the way in which moderate hypothermia is thought to work. Whether or not it can really achieve much salvage is still a matter of debate. The most recent studies of which I am aware indicate that it is the intracranial pressure which is of paramount importance and that attempts to increase the perfusion pressure do not help. It looks as if the emphasis should be on measures to reduce the “reactive oedema” and to keep the brain reasonably cool (and perhaps “sedated”) during the early hours in the hope that circulation will be restored to the “penumbra” brain tissue in time for it to regain function and viability.
To sum up : The management of severe brain injury in its early phase is dominated by (1) attempts to reduce swelling of the brain within the rigid skull so that as much blood as possible may get in against the rising intracranial pressure which is keeping it out, and (2) attempts to minimize the demand for oxygen and nutrients of those (perhaps large) parts of the brain which might survive if they could be protected from handing in their cards before the swelling goes down and an adequate blood supply returns in consequence. The measures used in pursuance of (1) include drugs and the prevention of hypertension and overhydration. Hypothermia (not profound hypothermia, which is cooling to very much lower temperatures for different purposes) is favoured by some in pursuance of (2) but many are unconvinced of its value and there is vigorous debate about the validity of the trial findings.
What matters is, as Coimbra says, that all the efforts in the early hours be made with the purpose of preserving as much compromised brain tissue as possible. The details of management will (properly) differ from centre to centre - and in due course consensus may emerge. That is the way genuine progress is made. What should be said is that the treatment of severe head injury should be optimised to that end, in the critical early stages particularly. That means that potentially harmful procedures (such as apnoea testing, which can cause lethal reduction in the perfusion of severely compromised tissue in the “penumbra” regions) must be avoided. Likewise overhydration, hyperthermia etc. The avoidance of measures which might exacerbate the brain damage, by whatever mechanism, is at least as important in the optimal management of these patients as the deployment of specific therapies. It is just such optimal management (aimed at maximizing salvage and therefore prospects of recovery) which is so conspicuously absent when the patient is regarded as a potential organ donor - perhaps from the first.