Permanent Vegetative State: Usefulness and limits of a prognostic
definition
C. J. Borthwick & R. Crossley
DEAL Communication Centre,
538 Dandenong Road,
E. Malvern, Vic. 3162
Australia
chrisb@vicnet.net.au
Abstract
Jennett and Plum’s 1972 naming of post-coma unresponsiveness as
“persistent vegetative state (PVS)” characterised the condition as
essentially irrecoverable and insentient. The evidence for these
propositions was always weak, and they have been largely disproved by
more recent research. Nonetheless, the definition and the attitudes it
embodies remain generally accepted, resting as they do on a firm
foundation of medical attitudes to disability and a public willingness
to evade uncomfortable facts. The first step in altering our approach
to people with this form of communication impairment must be to rectify
our understanding of the terminology.
Keywords
Vegetative state, persistent vegetative state, permanent vegetative
state, post-coma awareness, locked-in syndrome, disability
“If names be not correct, language is
not in accordance with the truth of things. If language be not in
accordance with the truth of things, affairs cannot be carried on to
success”
The Analects of Confucius, Book 13,
Verse 3
The Multi-Society Task Force on PVS (1994) [22] lists as among the
criteria for the persistent vegetative state “Bowel and bladder
incontinence”. The Royal College of Physicians (1996) lists as
among its criteria for the same condition “Incontinence of bladder and
bowel” [26]. Given that the other criteria for the vegetative
state include absence of voluntary movement, and thus inability to walk
to the toilet, and absence of communication, and thus inability to ask
for a bedpan, this is self-evidently fatuous.
It is also, of course, unhelpful, in that it is unlikely ever to be
employed in practice. Clinicians do not stand around a hospital bed
saying to each other “No evidence of awareness, check.” “No
evidence of purposive movement, check.” “Intermittent wakefulness,
check.” “But is he incontinent? We’d better wait a few hours,
just to be certain.” To be unhelpful, however, is not necessarily
to be uninformative; and any attempt to explain the inclusion of
pissing and shitting in the indicators for consideration of the
withdrawal of nutrition and hydration must lead to the conclusion that
there is an element of bad faith built into the definition of the
vegetative state.
By the use of the term “bad faith” I do not wish to imply any
deliberate attempt to deceive Ð rather, I would suggest that the
function of the definition is less to discriminate between conditions
than it is to lend scientific authority to judgements previously made
on other grounds; that is, the list of criteria has been designed to
give verisimilitude to an otherwise bald and unconvincing narration.
The use of terms of agency and motivation in such phrases as ‘has been
designed’ can easily drift into a mild form of conspiracy theory.
My contention is, rather, that professionals, being human, tend to
believe more easily in propositions that ease their difficulties,
diminish their distress, and increase their authority, and tend to
reserve close examination for propositions that stand the way of any of
these desirable outcomes; and that these tendencies shape the response
of the profession en masse.
To establish the nature of the judgements that the definition operates
to validate it is helpful to return to the time of its origin.
Jennett and Plum believed in 1972 [19] that an increased number of
patients with devastating brain damage resulting from such insults as
head trauma, brainstem stroke, or hypoxia - conditions that would
previously have resulted in rapid death - were surviving in a state
that was no longer coma but was not recovery. These patients
showed "wakefulness without awareness”, and no evidence of a conscious
mind. Jennett and Plum saw this situation as creating a need for a new
term: Persistent Vegetative State.
Jennett and Plum were “concerned to identify an irrecoverable
state...”. While in 1972 “the criteria needed to establish that
prediction [of irrecoverability] reliably have still to be confirmed”,
they anticipated that research would soon fill this gap: “Exactly how
long such a state must persist before it can be confidently declared
permanent will have to be determined by careful prospective studies.”
[19]
The Jennett and Plum formulation of Persistent Vegetative State is thus
both a prognostic and a retrospective definition. There are no
clear criteria that will at any given moment distinguish patients who
have it from patients who do not. The only means, then and now,
to distinguish people with persistent vegetative state from people with
merely transient vegetative state is to observe them and see whether
their vegetative state persists; the longer it persists, the higher the
probability that it will continue.
Jennett and Plum downplayed the difficulties of definitively
establishing lack of awareness and gave no consideration to the
possibility of misdiagnosis. Their opinions hardened over the
succeeding years, and at least by the time the formulation was
tightened in Plum and Posner’s The Diagnosis of Stupor and Coma (1982)
[24] persistent vegetative state was seen, essentially, as immutable,
insentient, incurable, and unmistakeable. [6]
From that time on, both those who agreed with Jennett and Plum over the
moral issues involved and those who wholeheartedly disagreed with them
phrased the terms of their dispute within the bounds of these qualities
of immutability, insentience, incurability, and clarity. Indeed,
the concept of persistent vegetative state was accepted across
medico-legal society with such enthusiasm that it is difficult in
retrospect to say whether Jennett and Plum launched an idea into the
culture or embodied an already existing archetype. Doctors,
ethicists, philosophers, theologians, and lawyers, each for their own
reasons, adopted this counter into their discourse.
The attractions of the concept are obvious. For one thing, it
allows us to avoid the contemplation of conscious unhappiness. For
another, persistent vegetative state being immutable, insentient,
incurable, and unmistakeable, involves no elements of uncertainty, and
doctors, quite naturally, prefer to have more certainty rather than
less, a point illustrated by a comment from the chairman of the BMA
Medical Ethics committee that “the atmosphere in which doctors make
decisions is even more stressful if they are uncertain whether their
decisions are correct, and that is what we are trying to put right.”
[4]
The three words ‘persistent vegetative state’ are attractive also to
such groups as ethicists and lawyers because, it is thought, they
exhaust all the morally significant information about any case in which
they occur, and any person may thus participate in any discussion of
any such case on an equal footing, without the need to examine any
particular circumstances.
The power of such a hard-edged concept to redraw fuzzy boundaries and
eliminate grey areas can be seen in the successive judgements in the
precedent-setting Bland case, where the words of the judge of first
instance (Brown J.)
Professor Jennett [in his evidence] ...
concluded ... that only exceptional cases have been reported as showing
recovery after a year.[2].
became in the judgement of the appeals court (Hoffmann J )
It is necessary to emphasise the awful
certainty of his fate. We all know of cases in which doctors have
been mistaken and where people have recovered to live meaningful lives
after being given over for dead. But no one has ever recovered
any vestige of consciousness after being in a persistent vegetative
state for more than a year. [1]
“Only exceptional cases” are not the same thing as “no one”, but any
discussion of persistent vegetative state tends to gravitate inexorably
to absolutes.
As the citation of Brown J. makes clear, Jennett’s own position does
not now rely on absolute irrecoverability. Rather, he is currently of
the opinion that
Insistence on certainty beyond a
reasonable point can handicap the physician dealing with treatment
options in apparently hopeless cases. The rare report of a
patient with a similar condition who survived is not an over-riding
reason to continue aggressive treatment. Such negligible
statistical possibilities do not outweigh the reasonable expectations
of outcome that will guide treatment decisions....[12].
This position, however, does not seem to sit well with either judges or
ethicists, who demand exactly that certainty that Jennett dismisses
-- an assurance that the diagnosis of persistent vegetative
state involves one and only one prognosis -- and read this
certainty into any formulation that permits it.
The term ‘persistent vegetative state’ has taken such firm hold that it
has resisted subsequent attempts by its originators to revise it.
In his recent book “The Vegetative State” Jennett adopts the usage of
the Royal College of Physicians (RCP) (1996) and refers only to the
‘vegetative state’, the ‘continuing vegetative state’, and the
‘permanent vegetative state’. The term has certainly largely fallen out
of use among neurologists. Nonetheless, less informed areas - the
press, the law, medical literature, Hollywood, many clinicians, and the
public in general -- continue to use the older term ‘persistent
vegetative state”. A speech by Pope John Paul II [20], for example,
studiously avoided the use of any term other than ‘vegetative state’;
40 out of 61 references to the speech on Google (6/5/04) nonetheless
used the term ‘persistent vegetative state’, (and only four used
‘permanent vegetative state’ -- a term that has in fact had
almost no success in making its way into lay - as opposed to
neurological - usage, a failure that supports the view that the public
already interpret ‘persistent’ as in this context meaning
‘permanent’). It is for these reasons that the terminology is
adopted here.
Jennett, in adopting the RCP nomenclature, said “the ‘persistent’
component of this term.... may seem to suggest irreversibility,
although Jennett and Plum had made it clear [sic] that this should not
be implied. Recovery of varying degrees after weeks and sometimes
months in a vegetative state is now widely recognised.... “ [16] Here
Jennett has underestimated the effect of his own formulation. Lay
observers have always interpreted the diagnosis as involving prognosis;
medical writers, more aware of problematic incidents, have generally
taken the view that the impression of irreversibility is worth
preserving. In the words of a 1996 British Medical Association paper on
treatment decisions for patients in persistent vegetative state, for
example, “an enduring cause for concern.... have [sic] been the
intermittent reports of alleged "recovery" from PVS. In the BMA's view,
recoveries, where they can be verified, indicate an original
misdiagnosis.”[7] The BMA is thus saying precisely that patients
in a properly diagnosed persistent vegetative state never recover. If,
therefore, someone diagnosed as being in persistent vegetative state
recovers, this discredits the diagnosis, not the definition.
Under this approach what might otherwise be seen as disconfirming
instances are irrelevant. “If you diagnose a number of people as having
tuberculosis and all die, the definition of tuberculosis might include
the prognostic criterion ‘invariably fatal’. If one patient eventually
recovers, however, you would modify your criteria to omit the words
'invariably fatal' -- or, if you were following the PVS model of
nosology, you would note that having recovered the patient did not meet
the criterion of fatality and therefore could not have had tuberculosis
in the first place.”[5] This approach sees persistent vegetative state
as a Platonic ideal, reflected imperfectly in the diagnoses of those
who see through a glass darkly. However persuasive this may be as
metaphysics, we ourselves live in the world of phenomena, where the
only observable data consists of people who have been diagnosed as
being in persistent vegetative state. In practice ethicists,
philosophers, and the medical profession move nimbly between the
Platonic sphere and visible experience, carrying baggage both ways.
This platonic conception means that believers can also avert their eyes
from the way in which diagnoses of persistent vegetative state are
generally made in the real world. Despite what one might think
from the time devoted to it in the media, persistent vegetative state
is an extremely low-incidence disease;
Information from several studies
suggest that the incidence of the Vegetative State is about
0.7-1.1/100,000 population..... Prevalence figures from
throughout the world suggest that between 2-10/100,000 of the
population are Vegetative [26].
If admission to care was evenly distributed (as it is not) then each
American hospital would thus have new persistent vegetative state cases
at a rate of one to two every three years, and every physician
(assuming ten physicians attend each persistent vegetative state
patient) one every 25-30 years (obviously, persistent vegetative state
cases tend to group in large hospitals with emergency departments, but
this must also mean that the median contact rate for both physicians
and hospitals is considerably lower).
This does not make it easy to build expertise with these patients,
particularly as their varying presentations require some time to
master. Wade, the author of a practice guide to persistent vegetative
state, said in answer to a query on the misdiagnosis/recovery rate
among his patients that “My own experience is only of about 30 cases,
and only followed for about five years at most, insufficient to draw
any sound conclusions [31]” If the standard is as high as this,
or higher, very few people indeed can claim expertise. Many
diagnoses of persistent vegetative state will in any case continue to
be made by people who know it only from textbooks. Andrew Grubb,
Professor of Medical Law at the University of Wales and author of a
recent study, has said [11]: “What we did discover is that relatively
few doctors who were likely to have seen patients in this condition,
had seen many patients in this condition. A fair proportion had seen
one or two, but very few had seen more than, say five. And.... there
is, I think, a strong suggestion that the nature of this condition
means that it's better diagnosed through experience.”
The words “five years at most” in Wade’s earlier comment draw attention
to another difficulty; most doctors who have seen several cases of
vegetative state will have seen them in the early stages when their
case was being pursued intensively, and very few indeed will have
followed the progress of their patients even over the next year when
they are introduced to therapy or simply reduced to care and
maintenance. Any statements they make about prognosis will at
best be based on one of the consensus statements such as that of the
Multi-Society Task Force and at worst will be drawn from the same stock
of misconceptions as is held by the society at large. Persistent
vegetative state, like other conditions such as mental retardation or
autism, takes its meaning from how it is used in the world.
A yet further issue is that medical systems do not place any great
emphasis on revisiting or reviewing diagnoses over time, even where
such diagnoses are not, as here, expressed in terms of certitude and
irreversibility. Keen attention may be paid in the early months
to signs of developing communication, but once a diagnosis of
persistent vegetative state has been arrived at the bar tends to be
raised considerably. I have myself been involved in several cases
where people originally diagnosed as being in persistent vegetative
state have recovered speech [9], and one patient at least had some
difficulty convincing her medical practitioners of her recovery of
sentience even when speaking to them over the telephone.
In view of these factors one should not be surprised that many surveys
have found that a considerable proportion of people carrying diagnoses
of persistent vegetative state can be declared misdiagnosed after a
relatively cursory examination (see, for example, Tresch et al, 1991
[30]). Ethicists who say such things as “To the best medical
knowledge when properly diagnosed, such a condition is irreversible....
the patient will not return to any level of sapient or sentient
existence.....[29]” rely on the use of weasel words such as “properly
diagnosed” to imply that cases of misdiagnosis are really nothing to do
with the central issue when in fact such errors are both predictable
and inevitable. It is as if there were two identical and
indistinguishable species of mushrooms, one of which was delicious and
the other fatal; to say “Provided you choose the delicious variety, you
are absolutely safe’ would be true but would also be recklessly
misleading.
The almost universal acceptance of Jennett and Plum’s definition, and
of the approach it embodies, has made it difficult to remember that
this approach was not inevitable. There were a number of
alternative routes open to them. They could have sought for ways
to uncover consciousness where it conceivably lay hidden, or they could
have sought out the treatments that were associated with the then rare
instances of recovery and sought to build on them, or they could have
simply presented the issues, raised the questions, and left it to
future research to confirm or deny their hypotheses.
None of these approaches, to be sure, would have solved the problem as
they saw it, which was that doctors had to make predictions and
decisions immediately, before any further research was done. More
specifically, Jennett and Plum believed that it was from time to time
desirable to allow such cases to die. Being men of their time, they
believed that resources were limited, the death of a person with a
severe disability was not a matter for any great sadness, and that the
person best fitted to make life and death decisions of this kind was a
medical practitioner. This being so, they sought a way for
a doctor to be able to say definitively that further treatment would be
futile and to have his opinion accepted without any time-wasting
arguments; and they took a short cut to certainty.
They made the assumption that future research would fill in the gaps
that they had noted in their argument, and that this research would
confirm their speculation. They assumed, too, that there were no
other aspects of brain function, not yet identified, of which they were
ignorant. In the words of Donald Rumsfeld, they assumed that
there were known unknowns, but no unknown unknowns. On the basis
of these assumptions they built into the definition of persistent
vegetative state the necessary conditions for unfettered medical
autonomy.
Jennett and Plum’s conclusions fitted snugly into the prevailing
medical culture, which also by and large saw the fundamental problem
with people surviving in a semi-comatose state not as their being in a
semi-comatose state but as their surviving at all. Resources, it
was felt, were being wasted on people who would never recover and who
would be unlikely to contribute to the national wealth. Jennett
himself passionately believed that patients in persistent vegetative
state placed a strain on limited resources, and that physicians who
care for them “sound ... a death knell for those who are denied the
benefits of appropriate care by [this] spendthrift attitude. [17]”
Jennett and Plum apparently believed that the number of people
requiring long-term total care had increased, was increasing, and
needed to be diminished. I should comment parenthetically that
Jennett and Plum asserted this growth in cases of persistent vegetative
state but did not document it, and no reliable survey has since been
done to establish it.
Jennett and Plum are in the position of a Virginian settler who in 1650
notes that there have in a community of a thousand inhabitants been
five deaths from native American attack in the past year in the thirty
miles abutting on to the township, and on that basis calculates that
when America has been extended to the Pacific three thousand miles away
the number of yearly deaths will be five hundred per thousand head of
population. The flaw in this calculation is that it is the
frontier that is liable to such casualties, and the frontier moves
forward on both sides, taking land from the native Americans on one
side and converting it into safer settled land on the other. Similarly,
Jennett and Plum’s approach to coma treatment rests, I believe, on a
misconceived idea of how medical science works. It is not usually
the case that a new medical advance creates for any extended period a
larger number of people surviving with disability. I would suggest that
the pattern is that medical advances shift the border of normal
practice into new areas but maintain a roughly constant area of
disputed borderland -- that more underweight babies, for
example, are saved from disability by improved techniques, emboldening
doctors to attempt to save still lighter and earlier births at higher
risk, leaving the total number of babies born with disabilities largely
unaltered.
Jennett’s attitude to the use of finite medical resources may have been
reinforced by the fact that many people have strong feelings about the
undesirability of disability. When Professor Andrews of England’s Royal
Hospital for Neurodisability reported a study finding that 75% of the
patients presenting with diagnoses of persistent vegetative state were
eventually able to communicate [3] the publication of this article in
the British Medical Journal was accompanied by an editorial by Ronald
Cranford that said “.... all 17 patients who were found to be conscious
were severely disabled; .... I would speculate that most people would
find this condition far more horrifying than the vegetative state
itself, and some might think it an even stronger reason for stopping
treatment than complete unconsciousness.[8]”
Some, myself included, might think that Dr. Cranford’s opinion on
stopping treatment was rather less significant than the opinion of the
17 patients with whom communication had been established. He,
however, was a member of the Multi-Society Task Force and they were
not, which may help to account for its stealthy expansion of the
Jennett definitional criteria.
a persistent vegetative state becomes permanent .... when a physician
can tell the patient's family .... with a high degree of medical
certainty that there is no further hope for recovery of consciousness
or that, if consciousness were recovered, the patient would be left
severely disabled.[emphasis mine] [22]
In 1972 Jennett and Plum called for research to establish the criteria
needed to establish reliably a prediction of permanence.
Thirty-two years of research having failed to achieve this reliability,
it is now said to be unnecessary. Patients have Permanent Vegetative
State if they will be either probably unconscious or certainly
disabled. This, too, approaches bad faith -- taken,
again, as meaning that the process has an undisclosed agenda. The
uncontested expansion of the definition can be explained only under the
hypothesis that the problem that the Multi-Society Task Force was
concerned to combat was not the lack of awareness of these patients but
their survival.
If this prejudice represented a misdirection or a perversion of the
general will, to expose it would suffice to correct it. This
seems, however, unlikely. Our society wants the problem to go away, and
believes whatever serves this end. Such a hypothesis would go some way
to explaining why such research as that of Professor Andrews has had
such minimal impact.
Such research has now established virtually beyond cavil that the
diagnosis of persistent vegetative state is liable to considerable
error. Depending on the intensity of the examination, combined
error and misdiagnosis rates in different studies have ranged from 15%
[17] to 75% [18] the latter figure being one that should have exploded
the notion of irreversibility altogether. This has not happened,
and it is difficult to account for this inaction except under the
hypothesis that projected irrecoverability was never as important an
element of the concept as was present inconvenience. One might
compare Aesop’s fable of The Wolf and the Lamb. The wolf says to
the lamb “I’m going to eat you because you’re fouling my water”, and
the lamb points out it is drinking downstream; the wolf says “I’m going
to eat you because you called me bad names last year”, and the lamb
points out that it was only born this year; the wolf says “Well, if it
wasn’t you, it was your father” and eats it. When a belief
survives the conclusive disproof of the assumptions on which it
supposedly rests, it is reasonable to suggest that it rests on other
assumptions that cannot be so openly avowed.
One test of that hypothesis is to see how Jennett responded to research
that raised the possibility of emergence from persistent vegetative
state. We find that when Andrews originally reported on evidence
of recovery from persistent vegetative state Jennett’s first response
was to complain that Andrew’s paper might “reverse the trend towards
compassionate withdrawal of life support, measures that have hitherto
seemed a reasonable response to the ethical dilemma....[14]”. That is
to say, if the demonstration of consciousness was incompatible with
termination of the persistent vegetative state patient, it was the
former, not the latter, that had to go.
If, then, the medical consensus on the appropriate treatment for people
with post-coma wakefulness rests not on such characteristics as assumed
irrecoverability (which can be refuted) but on such characteristics as
their cost and trouble (which are undeniable), what point is there,
then, in raising such issues as the misdiagnosis and/or recovery rates
at all?
If it was possible to prise open the jaws of the definition, we might
as a minimum establish protocols for the treatment of people diagnosed
as being in persistent vegetative state that would spare them the
horrors of being operated on without anaesthetic (“the PVS patient may
'react' to painful stimuli, but he or she does not 'feel' pain in the
sense of conscious discomfort of the kind that doctors would be obliged
to treat....”[21]) or being starved to death over a period of weeks or,
in unpractised hands, months (for letting die, too, is a specialist
skill).
If the issue was able to be discussed without subterfuge, we might even
work our way towards a positive alternative -- one that
could allay society’s fear of disability without eliminating the people
with disabilities.
The first step, however, must be to correct the defects of the present
terminology. The term persistent vegetative state has been
booby-trapped from the outset, and it is almost impossible for patient
advocates to use it without self-contradiction. It is as if there was
in the courtroom no neutral term for ‘defendant’, and the lawyer for
the defence had to refer to his client as ‘the guilty party’.
Using the term concedes the accusation and decides the case. “This PVS
patient may be able to communicate” is equivalent to saying that “This
criminal is innocent” or even “This triangle has four sides”. We cannot
reach a solution to the problems of treating post-coma patients while
we retain the terminology of persistent vegetative state. The
term ‘persistent vegetative state’ contains within itself the
refutation of any objections we might make.
Practical consequences follow. If the problem is seen as the
survival of unwanted people then other situations that differ from
persistent vegetative state on medical indices but resemble it in
presenting the same problem are easily brought into the same discourse
and gravitate easily to the same range of solutions and the same
systematic euphemisms. This process can be seen in operation in
legal terms in the recent English case of Re D [25], where the actions
previously approved in cases of uncontested persistent vegetative state
were seen as appropriate also to a case where “one paragraph of the
guidelines had not been fulfilled”.
The recent identification of ‘the minimally conscious state’ (MCS) may
also prove a means of extending the ambit of persistent vegetative
state rather than limiting it. ‘Minimally conscious’ patients
‘demonstrate discernible behavioral evidence of consciousness but
remain unable to reproduce this behavior consistently’ [12], and it can
reliably be assumed that any comments made about the possibility of
diagnostic error or the probability of recovery in persistent
vegetative state will apply a fortiori to patients in MCS. If, however,
MCS is seen as further restricting the boundaries of ‘real’
consciousness rather than as drawing more strictly the boundaries of
persistent vegetative state then these patients will have less rather
than more chance of attracting appropriate therapy. Jennett, for
example, feels that
As medical knowledge about the
diagnosis and prognosis of the minimally conscious state increases and
becomes more widely known, it seems likely that the law may come to
accept that it may be in the best interests of some such patients to
have life-sustaining treatment withdrawn. [15]
If it was possible to wind back the clock to 1972, we could ask whether
the world would have been better off if the term persistent vegetative
state had never been coined. If people who had emerged from coma
but not yet demonstrated awareness had been referred to in later
literature as ‘people who have emerged from coma but not yet
demonstrated awareness’ we may well have had more freedom to consider
all possible routes out of the difficulties presented by the situation.
The recent proposal from the Australian National Health and Medical
Research Council [23] to refer to vegetative state as ‘Post-Coma
Unresponsiveness (Vegetative State)’ is a step in this direction.
Indeed, as the misdiagnosis/recovery rate of people diagnosed as being
in persistent vegetative state is between 17% and 75%, it is at least
as true to say of a randomly selected patient diagnosed as having
persistent vegetative state (or ‘post-coma unresponsiveness’) that he
or she is conscious but locked in to a generally unresponding body as
it is to say that he or she has persistent vegetative state, with all
that entails.
The term “locked-in syndrome’ (LIS) is now usually applied only to
patients who become unable to speak or move as the result of certain
rare cerebro-vascular accidents involving the brainstem. The
appearance of patients with locked-in syndrome is similar to those
diagnosed as being in persistent vegetative state, except that the
former may be able to control vertical eye movements or
blink. If all patients who have emerged from coma and are
unable to speak or move reliably were treated as being in the same
category as people diagnosed with locked-in syndrome, nomenclature
would be simplified; and while we cannot know whether all such cases
have consciousness, it would certainly appear that under such an
assumption we will make fewer mistakes.
Such a change may in fact have a concrete effect on the quality of
hospital care and thus on survival . Survival rates in LIS are
many times that in persistent vegetative state (five year survival rate
in LIS, 83% [10] five year survival rate in persistent vegetative
state, somewhere between 5% and 50% [18] depending on whether the
population is sampled at the time of the trauma or the declaration of
permanence). This difference in outcomes exists despite the close
similarity in the physical manifestations of the two conditions (and in
their resource costs -- costs which do not, for some
reason, seem to arouse any clamour for the termination of LIS
patients).
In part the difference in survival rates is obviously due to a greater
number of deliberate terminations of patients diagnosed as persistent
vegetative state: it is also probable, though, that the average
standard of nursing care provided for people who are believed to be
unable to appreciate attention and are known to be unable to complain
about neglect is less than that provided to people who are thought able
to feel and communicate. Jennett himself identified as a relevant
variable whether a hospital labelled patients as persistent vegetative
state earlier or later. “There is no doubt that the label PVS in the
first few weeks after a brain insult can result in suboptimal
rehabilitation efforts at a stage when active treatment is important,
because recovery is still possible.”[16]. Is it not probable that
having the label persistent vegetative state not simply in the first
few weeks but in the months and years after a brain insult
-- that having that label for anybody, ever - also results
in suboptimal rehabilitation?
A move in this direction would have the virtue of liberating us from
the fundamental rigidity of the definition of persistent vegetative
state -- the belief, inherent in the term, that prognosis
is dependent on the nature of the trauma and not on the nature of the
treatment, that the problem is entirely in the skull and not at all in
the hospital.
Jennett and Plum closed off a number of avenues of research by making
the question one of the intrinsic composition of the patient, a
decision that has largely determined the attitude of the field since.
If a patient was in persistent vegetative state they would not recover
consciousness; if they were not, they might; it was a matter of the
physical state of the brain on day one, not of anything that the
hospital might do. To use another analogy, it is as if a cookery
book were to divide egg dishes into two groups - soufflŽs (which always
rose) and scrambled eggs (which never rose) purely by a chemical
analysis of the ingredients of each (more or less salt, larger or
smaller eggs, cracked at the big or the small end) rather than by
looking at baking or frying.
We need not only to change the name of persistent vegetative state but
to recast its nature completely. The most serious effect of belief in
the absolute nature of persistent vegetative state is that it carries
the implication that, in the words of the Multi-Society Task Force, “By
definition, patients in a persistent vegetative state are unaware of
themselves or their environment. They are noncognitive,
nonsentient, and incapable of conscious experience. [22]”
This belief closes off any road into the condition through
communication. This is a serious matter. After all, an
entire discipline has sprung into existence since Jennett and Plum
first used the term persistent vegetative state -- the
field of Augmentative and Alternative Communication, or AAC, devoted to
establishing and strengthening communication in people without
functional speech (an area in which medically trained staff have much
confidence but little competence).
If people do not communicate awareness, why do we not begin from the
standpoint that this a deficit in communication, rather than leaping to
a conclusion that there is a deficit in awareness -- a
conclusion that should only be reached, if at all, when all other
explanations have been exhausted? We should in the
first instance attempt to remedy communication problems and only then
decide whether awareness is irrecoverable.
If the various bodies attempting definitions in this area had consulted
therapists they might have produced different results. Where the
criteria state that persistent vegetative state may be diagnosed if no
evidence is shown of “sustained, reproducible, purposeful, or voluntary
behavioural responses to visual, auditory, tactile, or noxious
stimuli”[22] therapists know that there are a number of problems with
these requirements. “The ability to generate a behavioural response
fluctuates from day to day and hour to hour, and even minute to minute,
depending on fatigue factors, general health of the patient and the
underlying neurological condition.” [27] As Professor Andrews has said,
“it takes considerable skill in getting them into the optimal condition
to be able to communicate.” [11] ”Many patients who are
misdiagnosed as being in the vegetative state are blind or have severe
visual handicap; thus lack of eye blink to threat or absence of visual
tracking are not reliable signs for diagnosing the vegetative state.”
[3]
AAC therapists would be able to add to the list of things that might
interfere with communication such factors as contractures, medication,
motivation, depression, fatigue, position, long- and short-term changes
in muscle tone, and stress -- stress that would be
maximised in test situations where the patient is asked to perform on
command (as in Alice in Wonderland -- “Give your evidence,”
said the King; “and don’t be nervous, or I’ll have you executed on the
spot.”)
Dyspraxia, the condition where one is able to perform a movement only
on condition that one doesn’t think about it, is a recognised hazard in
AAC. All these problems make the words ‘sustained’ and
‘reproducible’ dangerous and destructive. If I was trapped on a
desert island and trying to contact passing ships I would hope that
they would come to investigate my first attempt at a bonfire rather
than waiting for a pattern to emerge, and if I only had enough wood for
one clearly visible fire I would hope that was enough.
Unfortunately, one of the other issues with the term persistent
vegetative state is that its diagnosis is usually taken to preclude AAC
intervention. In a recent study, the most commonly cited reason
for failure to offer AAC to people with acquired problems was presumed
lack of cognition [27]. Given the uncertainties inherent in the
diagnosis of persistent vegetative state, AAC intervention should
precede diagnosis rather than vice versa. Indeed, intervention
aimed at establishing communication should be mandatory for this
population, as non-speech communication strategies now available may be
able to make use of controlled movements not evident at a traditional
neurological examination. Andrews et al report that in their unit "the
patient's awareness is nearly always identified first by the
occupational therapists ... and only later is communication achieved by
the other members of the team" [3] and relate this to the patients'
severe physical impairments and the need for appropriate positioning
and adaptive equipment to elicit responses.
Everyone who has been diagnosed as being in a persistent vegetative
state, no matter how long ago the diagnosis was made, should have a
non-speech communication assessment given by a specialist
multi-disciplinary team. Even if no useable responses are found
this assessment should be reviewed annually (and immediately any
improvement is observed in the patient). Regular reviews are
necessary both because there may have been subtle gains in movement
control not detectable without the use of technology and because
non-speech communication technology itself is developing rapidly.
The idea of a specialist team necessarily implies the development of a
centre dealing with such cases in each large population centre.
The Royal Hospital for Neuro-Disability may well serve as a model (and
should serve as a benchmark; recovery/rediagnosis rates much below
their 75% should eventually require explanation).
The existence of such centres (or their absence) should be given legal,
or at least judicial, recognition. It is not simply that courts
should not accept a diagnosis of persistent vegetative state as being
authoritative unless made by an expert in the field (though that should
also go without saying) but that courts should not accept a prognosis
of continuing vegetative state unless the patient has been offered a
prolonged period of rehabilitation by experts. Diagnosis cannot
be separated from therapy.
If the lessons of Professor Andrews’ work are accepted, replicated, and
supported, people with these conditions can be offered the opportunity
to take life and death decisions for themselves, without the need for
the judgements of doctors, priests, or husbands. This will still, of
course, raise ethical questions -- but rather different
ones. It hardly seems fair, for example, that the only
circumstance in which a person cannot be killed is if they are able to
ask for release. Once having re-established communication, we must show
these people that their lives can be made bearable, or we must accept
the consequences .
References
1 Airedale N.H.S. Trust v. Bland, [1993]
1 All ER 821 (Hoffman J.)
2 Airedale N.H.S. Trust v. Bland, [1993]
2 WLR 318 (Brown J.)
3 K. Andrews, L. Murphy, R. Munday, C.
Littlewood, C. Misdiagnosis of the vegetative state: retrospective
study in a rehabilitation unit. BMJ 313 (1996) 13-16
4 H. Ashraf, BMA address the issue of
withholding and withdrawing treatment, Lancet 353 (1999) 9171
5 C. Borthwick, The Permanent Vegetative
State: Ethical crux, medical fiction? Issues in Law & Medicine,
12:2 (1996) 167-185
6 C. Borthwick, Persistent Vegetative
State -- Syndrome in search of a name, or judgement in
search of a syndrome? Monash Bioethics Review, 14:2 (1995) 20-25
7 British Medical Association,
Withholding and withdrawing Life-Prolonging Medical Treatment, Author,
London, 1996
8 R. Cranford, Misdiagnosing the
persistent vegetative state, BMJ 313 (1996) 5-6
9 R. Crossley, Speechless, E P Dutton,
New York, 1997
10 J. Doble, A. Haig, C. Anderson, & R.
Katz, Impairment, activity, participation, life satisfaction, and
survival in persons with locked-in syndrome for over a decade:
follow-up on a previously reported cohort. J Head Trauma Rehabil. 18(5)
(2003) 435-44.
11 Frontline, Scotland; Back from the dead,
22/11/2000, http://news.bbc.co.uk/1/hi/scotland/1033502.stm
12 J. Giacino, S. Ashwal, N. Childs, R.
Cranford, B. Jennett et al, The minimally conscious state: Definition
and diagnostic criteria Neurology;58 (2002) 349-353
13 B. Jennett, Resource allocation for the
severely brain damaged, Arch Neurol 33 (1976) 595-597
14 B. Jennett, K. Boyd, Managing the Persistent
Vegetative State, BMJ, 305(6852) (1992) 486-7
15 B. Jennett, The vegetative state: Medical
facts, ethical and legal dilemmas, New York, CUP, 2002, p.144
16 B. Jennett, The vegetative state: Medical
facts, ethical and legal dilemmas, New York, CUP, 2002, p.4
17 B. Jennett, Resource allocation for the
severely brain damaged, Arch Neurol 33 (1976) 595-597
18 B. Jennett. The persistent vegetative state
BMJ 310 (1995) 1137
19 B. Jennett & F. Plum, (1972) Persistent
Vegetative State After Brain Damage; A Syndrome in Search of a Name,
Lancet. 1(7753):734-7
20 John Paul II, Address to participants in the
International Congress on ‘Life-Sustaining Treatments and Vegetative
State; Scientific Advances and Ethical Dilemmas’, 20 March 2004,
http://www.vatican.va/holy_father/john_paul_ii/speeches/2004/march/documents/hf_jp-ii_spe_2040320_congress-fiamc_en.html
21 K. Mitchell, I. Kerridge., & T. Lovat,
T, Medical futility, treatment withdrawal, and the persistent
vegetative state, Journal of Medical Ethics, 19 (1993) 71-76
22 Multi-Society Task Force on PVS,. Medical
aspects of the persistent vegetative state (1). New England Journal of
Medicine. 330(21) (1994) 1499-508
23 National Health and Medical Research
Council, Post-coma unresponsiveness (Vegetative State): a clinical
framework for diagnosis, NHMRC, Canberra, 2003
[http://www.health.gov.au/nhmrc/publications/synopses/hpr23syn.htm]
24 Plum F, Posner J. The diagnosis of stupor
and coma. 3rd ed. Philadelphia, PA:FA Davis;1982.
25 Re D [1998] 1 FLR 411
26 Royal College of Physicians, Guidance on
diagnosis and management: Report of a working party of the Royal
College of Physicians, London, Royal College of Physicians, 1996
27 Royal Hospital for Neurodisability,
International Working Party Report on the Vegetative State (1996),
London, RHN
28 A. Russell. & S. McAllister, Use of AAC
by Individuals with Acquired Neurologic Communication Disabilities:
Results of an Australian Survey, AAC, 11, 3 (1995) 138-141
29 T. Shannon & J. Walter, Artificial
nutrition, hydration; Assessing papal statement, National Catholic
Reporter, April 16, 2004,
http://natcath.org/NCR_Online/archives2/2004b/041604/041604i.php
30 D. Tresch, F. Sims, E. Duthie et al,
Clinical characteristics of patients in the persistent vegetative
state. Arch Intern Med:151 (1991) 930-32
31 D. Wade, Response, eLetters for Jennett 319
(7213) 796-7, (Electronic response) 7 October 1999,
http://www.bmj.com/cgi/eletters/319/7213/7
Footnotes -
1 “persistent vegetative state’ and ‘Schiavo’ called up 4,760 entries
on Google (6/5/04), ‘permanent vegetative state’ and ‘Schiavo’ only 824.
2See, for example, Schildler v. Schiavo, 2004, Case 2d03-5200 Florida
District Court of Appeal.
3 Of 112 Medline citations for ‘vegetative state’ in the period
2002-2003, 60 mention ‘persistent vegetative state’ , 44 ‘vegetative
state’ only, and only 8 “permanent vegetative state”.
4 See, for example, “Critical Care” (1997), “Signs of Life”
(1999), “Talk To Her” (2002), or “The Safety of Objects” (2003).
Special Edition of Neuropsychological Rehabilitation
Manuscript
Number:
NRH_S1_17
Title:
Ethics and the Vegetative State
Abstract
Before discussing ethical issues to do with patients in Permanent (or
Persistent) Vegetative State (PVS) it is necessary to address the
foundational issue of whether PVS as a concept is able to provide a
robust link to situations in the real world. The high reported
rates of misdiagnosis and recovery in patients diagnosed as being in
PVS casts doubt upon the applicability of ethicists’ thought
experiments on Platonic forms to actual decisionmaking in clinical
situations. We should abandon the illusion that we can have
access to logical certainty through diagnostic definition, and should
instead frame our opinions and our procedures in ways that can
accommodate a high element of uncertainty, and should in the light of
recent studies give considerable weight to the possibility that
patients at present unable to express opinions on their care will later
become able to do so, if given proper treatment and adequate evaluation.
Ethics and the Vegetative State
Ronald Dworkin, like virtually all ethicists, defines “a persistent
vegetative state… [as one where the patients] are unconscious…. and the
higher centers of their brains have been permanently damaged in a way
that rules out any return to consciousness. They are capable of
no sensation and no thought.”(Dworkin, 1995)
Ethicists such as Dworkin have written largely on issues associated
with the vegetative state (VS) , almost always in the form of the
Persistent (or Permanent) Vegetative State (PVS), understood in
Dworkin’s formulation (1). These issues include
• Is
a person in PVS a ‘person’ (in a number of senses)? (Gormally L, 1993)
•
Can a person in PVS have interests, or ‘best interests’? (McLean, 2001)
•
Should scarce medical resources be allocated to people in PVS?
•
Are nutrition and hydration for a person in PVS medical operations?
• Is
there a difference between killing a person in PVS and letting them
die? (Randall F, 1997)
•
Should people in PVS be considered to be ‘dead’ (in a number of senses)?
All these are issues in which I have neither expertise nor interest,
and I refer those who wish to survey the discussion in this area to the
abundant literature reviewed in Jennet (2002).
My intention in this paper is to examine the conditions that would be
necessary for those discussions to be meaningful, and to examine the
evidence for the proposition that such conditions exist.
Philosophical Inquiries
Philosophers have gone to some trouble to distinguish between false
statements and meaningless statements. Bertrand Russell, for
example, argued that the statement “The present King of France is bald”
is on the face of it not false, despite the fact that France has no
king, because if the statement was false then its negation – “The
present King of France has hair” – would be true (Russell, 1905).
Russell resolved this paradox by saying that in stating “The present
King of France is bald” we are making several separate but linked
assertions - that an x exists such that x is the King of France, and
that x is bald – and that the first of these, and therefore the
statement as a whole, is false.
If you want to be bald, it is necessary to exist. However, cognitive
philosophy also boasts an entire bestiary of creatures who are
universally agreed not to exist but who are nonetheless employed as
thought experiments to draw out the implications of different
philosophical positions. The Martian lacks humanity, but has
consciousness and observable behaviour; the Zombie has humanity and
behaviour, but lacks consciousness (Midgely, 2004); the Robot has
neither humanity nor consciousness, but has behaviour (Kirk,
1986). If we make these up into a table, we find that there are
vacant spaces for people who have humanity but neither consciousness
nor behaviour, and people who have humanity and consciousness but no
behaviour; and these gaps have been filled by recruiting people in PVS
and Locked-In Syndrome (LIS).
Ordinary Human
Martian
Robot
Zombie
Human in PVS
Human in LIS
Humanity
*
*
*
*
Consciousness
*
*
*
Behaviour
*
*
*
*
Philosophical actors, being embodiments of defined states of being, do
not pretend to be based on real-world experience, though their
hypothesized behaviour may still cast light on actual phenomena.
Ethical Foundations
Ethics, too, has its cast of didactic characters, each employed to
demonstrate the implications of particular combinations of
qualities. If we respect the rights of people with profound
mental retardation, it is argued, we should respect the rights of
nonhuman primates who have demonstrated speech-related capacity
(Ansotz, 1993). If we are prepared to abort a foetus a day before
birth, then we should be prepared to kill a [handicapped] baby a day
after birth (Kuhse and Singer, 1985). If we are forced to choose
between either saving the life of a chimpanzee who wants to go on
living and a human with profound brain damage who is not capable of
having desires for the future because its mental capacities do not
allow it to grasp that it is a mental entity existing over time, then
it is entirely justifiable to choose to save the chimpanzee (Singer,
1997).
Cells in the ethical table are filled roughly as follows (the
assignation of subjects in each case relying on varying assumptions as
to clinical observations and particular definitions of such open-ended
words as ‘consciousness’).
Adult Human
Ape (Koko)
Retarded Adult
Human Baby
Human Baby (Anencephalic)
PVS
Fetus
Humanity
*
*
*
*
*
*
Consciousness
*
*
*
*
Behaviour
*
*
*
*
Potential
*
*
*
Language
*
*
In the field of ethics, however, practitioners seek to make their
constructs do double duty. They must both fit neatly into
structures of argument and be able to be reached down from the shelf
for application in actual situations. This makes it necessary to
address the issue of whether the person in PVS - ‘a human with profound
brain damage who is not capable of having desires for the future’ - has
existence, or whether he or she is, like the present king of France, a
merely hypothetical entity.
It is here that the classification “vegetative state”, and its
extensions “permanent vegetative state” and “persistent vegetative
state”, become so useful. They provide ethicists with the ability
to export definitional truths from the world of logic to the world of
clinical reality. “By definition, patients in a persistent
vegetative state are unaware of themselves or their environment. They
are noncognitive, nonsentient, and incapable of conscious experience.”
(Multi-society Task Force, 1994). By definition, people in
vegetative state “do not 'feel' pain in the sense of conscious
discomfort of the kind that doctors would be obliged to treat”
(Mitchell, Kerridge & Lovat, 1993).
By definition, too, permanent vegetative state (or, more often,
‘persistent vegetative state’) is permanent; a 1996 British Medical
Association paper on treatment decisions for patients in persistent
vegetative state, for example, said that “an enduring cause for
concern… have [sic] been the intermittent reports of alleged ‘recovery’
from PVS. In the BMA's view, recoveries, where they can be verified,
indicate an original misdiagnosis.”(British Medical Association, 1996).
This alibi is important, because whether or not people with permanent
vegetative state recover, people diagnosed as being in persistent
vegetative state certainly do recover.
Historically, Jennet and Plum wanted "to identify an irrecoverable
state" -- irrecoverable and thus permanent. They named the
syndrome 'persistent vegetative state' because they did not have the
data to make 'permanent vegetative state' stick – as they put it, “the
criteria needed to establish that prediction [of irrecoverability]
reliably have still to be confirmed. Until then “persistent’ is
safer than “permanent” or “irreversible” ... (Jennett &
Plum, 1972, p. 734
The criteria that could successfully identify irreversibility, and the
data that should support them, have not been developed in the thirty
years since; indeed, more recent studies have cast ever-increasing
doubt on the certainty of the clinician, culminating in Andrews’ study
(Andrews, Murphy, Munday, & Littlewood, 1996) in which 75% of the
patients presenting with diagnoses of persistent vegetative state
proved in the event to be either misdiagnosed or capable of some
recovery: “Of the 40 patients diagnosed as being in the vegetative
state, 10 (25%) remained vegetative, 13 (33%) slowly emerged from the
vegetative state during the rehabilitation programme, and 17 (43%) were
considered to have been misdiagnosed as vegetative.”
That is to say, it is at least possible that (at most) one person in
four diagnosed as having Permanent (or Persistent) Vegetative State is
permanently vegetative.
I have hypothesized elsewhere (Borthwick, in press) that clinicians
have in general preferred to ignore the increasingly suspect nature of
the prognosis inherent in the diagnosis of permanent (or persistent)
vegetative state because they have been concerned less with issues of
consciousness than with opinions about resource use (according to
Jennett, physicians who care for such patients “sound ... a death knell
for those who are denied the benefits of appropriate care by [this]
spendthrift attitude.” - Jennett, 1976) and because they tend to
believe severe disability to be as bad as or worse than death
(Cranford, for example, commented on Andrews’ results that “… all 17
patients who were found to be conscious were severely disabled; … I
would speculate that most people would find this condition far more
horrifying than the vegetative state itself, and some might think it an
even stronger reason for stopping treatment….” – Cranford, 1996).
The medical profession has thus been prepared to relax its standards,
both in accepting a degree of error as to outcome – “Insistence on
certainty beyond a reasonable point can handicap the physician dealing
with treatment options in apparently hopeless cases….” (Giacino,
Ashwal, Childs, Cranford, Jennett et al, 2002) – and in recommending
termination for a wider range of cases – “As medical knowledge about
the diagnosis and prognosis of the minimally conscious state
increases…. it may be in the best interests of some such patients to
have life-sustaining treatment withdrawn.” (Jennett, 2002).
Both the argument from resources and the argument from disability
deserve attention, but they are not arguments that relate particularly
to the characteristics of the Permanent (or Persistent) Vegetative
State – permanence, lack of sensation, and absence of thought - as
employed by, say, Dworkin. Unless those qualities can be
regained, we are, when addressing the issues originally listed, in what
might be called a King of France situation.
One argument that has been employed to avoid this conclusion is
that “…when properly diagnosed, such a condition is irreversible…”
(Shannon & Walter, 2004) – that is, while we are in practice
subject to human error, this does not affect the qualities of the
platonic ideal of the PVS patient that is the proper object of ethical
discourse. This argument serves only to paper over the
fundamental difficulty of transferring ethical prescriptions into the
world of phenomena. To be told that we must treat people in
properly diagnosed PVS differently from people who have been
misdiagnosed as PVS is hardly helpful unless we have a way of telling
them apart, while to treat them the same way rather smacks of the
crusader’s way of distinguishing the faithful from heretics – “Kill
them all. God will recognize his own.”
The discussion of ethics as applied to disabilities of this nature
cannot progress until we discard once and for all the notion that there
is a name that when invoked can make our decisions simple and
straightforward. These matters are not susceptible of
hard-and-fast rules. It would be much easier if they were; and that is
why people try to pretend that they are, or at least behave as if they
thought so. Of course, you can have hard-and-fast rules if you want to,
but then they will be false rules, and they will lead you wrong;
because their simplicity will render them inapplicable to problems
which are not simple.
The discipline of ethics should abandon the illusion that it can have
access to logical certainty through diagnostic definition. Rather
than relying upon abstracted but determinative ethical pronouncements
we should instead frame our opinions and our procedures in ways that
can accommodate a high element of uncertainty. We should in the
light of Andrews' studies give considerable weight to the possibility
that patients at present unable to express opinions on their care will
become able to do so later if given proper treatment and adequate
evaluation.
Footnotes
(1) The nomenclature in this area is
confused. Most neurologists now adopt the usage of the Royal
College of Physicians (RCP) (1996) and refer only to the ‘vegetative
state’, the ‘continuing vegetative state’, and the ‘permanent
vegetative state’. Nonetheless, almost everybody else - the
press, the law, much medical literature, Hollywood, many clinicians,
and the public in general -- continue to use the older term ‘persistent
vegetative state’ as if it meant ‘permanent vegetative state’.
The term ‘post-coma unawareness’, suggested by the Australian National
Health and Medical Research Council (2003), would be an improvement
(although in the light of Andrew’s findings a more accurate term might
simply be ‘locked-in syndrome’).
(2)
References
Andrews, K., Murphy, L., Munday, R., Littlewood, C. (1996) Misdiagnosis
of the vegetative state: retrospective study in a rehabilitation unit.
British Medical Journal 313, 13-16
British Medical Association (1996) Withholding and withdrawing
Life-Prolonging Medical Treatment, London: Author
Ansotz, C. (1993) Profoundly Intellectually Disabled Humans and the
Great Apes: a comparison, in Cavalieri P. & Singer P. (eds) The
Great Ape Project, St. Martins Griffin, New York
Borthwick, C. (in press) Permanent Vegetative State: Usefulness and
limits of a prognostic definition, Neurorehabilitation
Cranford, R. (1996) Misdiagnosing the persistent vegetative state,
British Medical Journal 313; 5-6
Dworkin, R. (1993) Life’s Dominion: an argument about abortion, Harper
Collins, London, p. 187
Giacino, J., Ashwal, S., Childs, N., Cranford, R., Jennett B. (2002)
The minimally conscious state: Definition and diagnostic criteria
Neurology 58: 349-353
Gormally, L. (1993) Definitions of Personhood: Implications for the
Care of PVS Patients Catholic Medical Quarterly 44(4):7-12
Jennett, B. (1976) Resource allocation for the severely brain damaged,
Archives of Neurology 33: 595-597
Jennett, B. (2002) The vegetative state: Medical facts, ethical and
legal dilemmas, New York, CUP, p.144
Jennet, B., & Plum, F. (1972) Persistent Vegetative State After
Brain Damage; A Syndrome in Search of a Name, Lancet, 734, 736 (1972)
Kirk, R. (1986) Sentience, causation and some robots. Australasian
Journal of Philosophy 64:308-21
Kuhse, H., & Singer, P. (1986) Should the Baby Live? Oxford
University Press, New York
McLean, S. (2001) Permanent vegetative state and the law, J Neurol
Neurosurg Psychiatry 71(Suppl 1):i26-i27
Midgley, M., (2004) Zombies Can’t Concentrate, Philosophy Now, 44: 24-25
Mitchell, K., Kerridge, I., & Lovat, T. (1993) Medical futility,
treatment withdrawal, and the persistent vegetative state, Journal of
Medical Ethics, 19: 71-76
Multi-Society Task Force on PVS (1994) Medical Aspects of the
Persistent Vegetative State: Second of two parts, New England Journal
of Medicine, 330, 22, 1572-1579
National Health and Medical Research Council, Post-coma
unresponsiveness (Vegetative State): a clinical framework for
diagnosis, NHMRC, Canberra, 2003
[http://www.health.gov.au/nhmrc/publications/synopses/hpr23syn.htm]
Randall, F. (1997) Why causing death is not necessarily equivalent to
allowing to die, Journal of Medical Ethics, 23: 373-6
Russell, B. (1905) On denoting, Mind 14: 479-493.
Shannon, T. & Walter, J. (2004) Artificial nutrition and hydration:
Assessing the papal statement, National Catholic Reporter, April
16, 2004
Singer, P. (1997) Ethics and the limits of scientific freedom, Monash
Bioethics Review, 16