<PRE>
Message: #2948 - BPI Tech Brief #15
Date: 28 Jul 94 20:37:04 EDT
From: Mike Darwin <>
Message-Subject: SCI.CRYONICS BPI Tech Brief #15
BPI TECH BRIEF # 15
This is the last installment (for now) of the Standby
Manual. I have completed three more chapters including a
rough draft of the chapter on premedication; the
premedication chapter was an especially difficult one. I
have also completed the final version of the Chapter on
Standby Staff Safety and Infection Control. Ahead lie
Chapters on Euthanasia, Legal aspects of Standby and
cryopreservation, Basic Principles of Home Nursing Care and
possibly yet another chapter or two on other subjects
related to Standby.
I am especially interested in feedback from people on issues
that you feel are left unaddressed so far (in the material
covered) or questions which are raised, implied or otherwise
not dealt with well. This kind of feedback will help me
substantially in upgrading the final, printed version of
this book.
Of the Chapters I have completed, I am *least* satisfied
with this one (Chapter 6). Why? Because it just isn't good
enough at doing what it is really supposed to do: guide
standby personnel in determining when and how the patient
will experience cardiac arrest. I have two frustrations in
writing this Chapter. The first is that it is an impossible
task. There are so many ways that a system as complex as a
human being can fail that there are no substitutes for vast
experience. The ideal person would be someone of Feynman's
intellect and perspacity, with the combined career data base
of a seasoned neurologist, cardiologist, internist, hospice
nurse, oncologist, hematologist, etc... Alas, we have no
such person and even very experienced medical people are
tripped up or (wise enough to be) unwilling to make
prediction(s) about when a patient will arrest. The second
is the lack of more experience an actual measurements which
might serve to clarify the situation a great deal. In cases
of slow death (and even in many cases of so-called sudden
death) I feel that there are probably many fairly reliable
markers which can be used to determine the time-course to
cardiac arrest. But we have to *look* for for them.
Some systems for predicting patient survival outcome such as
the APACHE system already exist. BPI has (and uses) a
simple version of that program. The full fledged APACHE
program costs upwards of $250,000 and requires a large
mainframe to run. It won't tell you time course with a lot
of precision, but it *will* tell you whether or not the
patient will survive the hospitalization (providing the
tests and measurements the program requires to work are
being made) with better than 90% accuracy. Some larger
hospitals are already using APACHE to triage patients in the
ICU and CCU and contain costs. This is how APACHE Medical
Syatems, Inc. makes money on the program and why they can
charge what they do. (In all fairness it *is* a tremendously
sophisticated program and it is fraught with liability --
just wait till the public realizes this thing is already in
use to triage right now (of course they don't use that
word). In the final edition of this chapter I intend to
spend some time dealing with APACHE and suggesting ways we
can use it if the hospital that has the software is
cooperative and/or the patient is in a facility with APACHE
capability (NOTE: many facilities won't tell you they are
using APACHE).
I mention APACHE here because it bears paralells with my
perdicament in writing Chapter 6 and with the perdicament of
standby persnnel in predicting time course to legal death.
Everybody said APACHE was impossible. But it works,
surprisingly well. We need to start looking at our dying
patient's *closely* and doing lab analysis for lactates,
ammonias and other markers which may be highly predictive
and we need to start graphing this data. I believe we will
find markers which, while not they will not be 100%
predictive, will at least be very useful as a guide, much as
the APACHE system is. I would like to see ALL cryonics
organizations work together to build this data base by
openly sharing their records and agreeing to standardize
data gathering and laboratory monitoring during standby and
transport. Our statistical base (individually) is just too
small otherwise.
Having said the above about what we need to *discover* I
would also say that one of my great sources of frustration
and guilt is what I (we) don't know already that we *should*
know. You will see warnings about pulse oximetery in this
chapter and its use on low hemoglobin patients. This was
hard won information for me. Yes, I rememered the "facts"
but they didn't mean nearly as much to me as they did
*after* I had a patient experience cardiac arrest when the
standby team was neither present or prepared because I
overlooked clinical signs of hypoxemia (the patient was
agitated and *nasty*, and while he had previously been
agitated and confused while on morphine, he was never
aggressive -- a likely tip off that it was hypoxia due to
anemia rather than his usual problems with opiates). That
patient experienced uneeded minutes of warm ischemia because
of my lack of experience in applying a "book fact" to real
life, *and* because of the problem (common to health care
providers and nuclear reactor operators everywhere) of not
wanting to think or see the worst even as it begins to
unfold in front of you. If there is any take-home message
in this chapter it is in the opening quote. Too bad I read
it on the plane coming *back* from that patient's standby
when he was already in the cargo hold and the "incident" was
over. Hopefully you will learn from my mistakes. -- MD
Chapter 6 of STANDBY: END-STAGE CARE OF THE HUMAN
CRYOPRESERVATION PATIENT
by Michael Darwin with Charles platt
Copyright 1994 by Michael G. Darwin. All rights reserved.
Chapter 6
Standby and Transport Logistics
The first step in caring for a critically ill patient is to
realize that he is in serious difficulty. This may not be
easy, and seemingly inconsequential findings may presage
disaster. The gravity of the situation may not be apparent
even though there is serious malfunction of one or more
systems. A subtle change in a physical sign could be the
first indication of general collapse. It has been our
personal experience that early warning signs are overlooked
or dismissed unless the physician is ever aware of the
possibility of serious trouble. There is a recurring
tendancy even after one has "learned his lesson," to dismiss
an abnormal finding by ascriboing it to an unimportant
cause. It is not enough to recognize that a physical sign
could indicate serious difficulty. The weakest link in
patient care is the tendency of the physician to convince
himself that somehow everything will be all right. Every
clue must be sifted and analyzed. Every unexpected sign must
be understood.
--Stephen M. Ayers, M.D.
Care of the Critically Ill
Second Edition
The standard Local Standby Kit (LSK) contains two "E"
cylinders of oxygen, capable of powering the Michigan
Instruments Heart-Lung Resuscitator (HLR) for approximately
thirty minutes. This will usually be sufficient to transport
the patient via hearse or ambulance from the hospital or
nursing home to a mortuary or other facility where extended
external cooling and/or blood washout can be carried out.
Arrangements should be made with the cooperating mortuary
(or, if legal death is occurring at home, with the home-
hospice program) to provide at least two "H" oxygen
cylinders, each of 220 cubic foot capacity, or larger.
Always try to conserve E-cylinder oxygen for use when the
patient is being moved by a vehicle. If the patient is
initially hospitalized, try to use the hospital's oxygen
supply while waiting for the mortician or ambulance. In most
hospitals, you will find a wall outlet for oxygen in each
room. To tap into this supply, you will need to obtain a
special adapter or coupling from the respiratory therapy
department of the hospital or carry an assortment of
adapters for systems commonly in use in your country.
If a wall adapter has a flow restriction device such as a
flow meter, it will not provide enough pressure to run the
HLR. Only a wall oxygen connector with a DISS fitting (see
figure 3-1) can be used.
If the hospital does not have or will not make available
this type of fitting, you should ask for an H cylinder or
other source of bottled oxygen. Alternatively, you can seek
permission to bring a source of bottled oxygen in from
outside. Please note that when you are moving an oxygen
cylinder through the halls of a hospital, you must always
mount it on a proper cylinder truck or hand cart. This is a
safety requirement which is vigorously enforced in all
hospitals. Once the cylinder is in the patients room, it
must be secured to the wall or placed in an anti-tip base.
Alternatively, if the cart is a four wheel type which allows
the cylinder to rest stably at an angle, the cylinder may be
left *chained* to the cart.
A word of caution is in order about getting prompt access to
oxygen under emergency conditions in a strange city. Most
locales now require a prescription for medical oxygen. You
can safely substitute welding gas, but it is rarely
available on a 24-hour basis. Therefore, you should always
try to plan ahead and have oxygen ordered and delivered to
the home or mortuary as soon as you hear that the patient is
terminally ill--even if the patient is expected to survive
for weeks or months.
Sometimes, of course, it is not possible to plan ahead, and
transport technicians should know the procedure for calling
in a prescription for oxygen, either as a physician or the
agent for a physician. Unfortunately, cylinder oxygen is
becoming increasingly hard to obtain on a 24-hour basis. The
need for it has been diminished by widespread use of oxygen
concentrators (which plug into the wall and make oxygen from
room air) and liquid oxygen systems. In many cities and most
small towns, rapid, 24-hour delivery of oxygen in cylinders
is becoming a thing of the past. Consequently, it's even
more critical to plan ahead to insure a supply.
-------------------------------------------------------
WARNING: Mortuary personnel are generally unfamiliar with
the safe handling of oxygen. The transport technician will
need to supervise loading, unloading, and handling of oxygen
cylinders with great care. Remember always the risk of a
CATASTROPHIC FIRE at the mortuary or en route to it. Within
the confines of a vehicle, oxygen concentration can easily
rise to a dangerous level. Consequently, you must warn
mortuary or other personnel NOT TO SMOKE AS THEY MAY
NORMALLY BE ACCUSTOMED TO DOING SO.
----------------------------------------------------------
It's easy to forget this precaution when your prime concern
is caring for the patient, but mortuary personnel frequently
smoke and are especially inclined to do so at times of
stress--such as moving a patient who is on HLR support.
Remember, in a closed vehicle where there is a high
concentration of oxygen, a lighted cigarette can almost
guarantee a serious fire. Remember the Apollo fire!
Access To Ice
You will need 300 to 400 pounds of ice to cool the average
160 pound (72 kg) man, plus another 200 pounds for shipping
the patient. If the institution which has control of the
patient does not have access to this amount of ice or will
not make access available, you will have to get it from an
outside source.
There are 24-hour ice services in most cities. After you
obtain ice from an outside source, a mortuary may keep it
for you in one of their freezers (if they have one), or a
hospital may allow you to store it in one of their food
freezers. Note that if the ice has melted at all along the
way, refreezing it may turn it into a semisold mass, and
you'll need an ice pick or screwdriver to break it up.
If you are conducting a standby in the patient's home, you
must arrange to have a large supply of ice on hand, or you
must find a 24-hour source nearby. Convenience stores such
as 7-11 can usually meet this need. If one of these stores
is nearby, you may be able to delay buying ice until the
patient becomes frankly agonal, so long as enough personnel
are available to go out for ice when the time comes.
If there is no reliable source of ice nearby, and no freezer
in which to stockpile it for quick access, good quality
picnic chests can be used to store ice with relatively
little melting. The Igloo brand, with foam-insulated lids,
is recommended. You will need six 22-quart chests for an
average standby.
Do not use inexpensive, "soft" expanded polystyrene picnic
chests that are sold in drugstores and supermarkets. They
will leak copiously and will not hold ice for long enough to
be economical.
Arranging Prompt Release of the Patient
If the hospital has a staff mortician or diener (lab
assistant) who is responsible for handling and processing
remains in the morgue, you should contact this person and
ask for his help. If you take care of this early on, you'll
have a much better chance of obtaining prompt release of the
patient. A staff mortician can significantly delay the
release of the patient from the hospital if he feels that
you have ignored him or treated his authority with
insufficient respect.
Whenever possible, try to see that a death certificate is
filled out in advance, leaving the lines blank for the cause
of death and the signature of the pronouncing physician.
If the patient is at home and the hospice is unable to
provide round-the-clock nursing service, you will need to
make special arrangements for quick pronouncement of death.
This is generally done by having a registry nurse in
attendance. You will definitely need to clear this with the
hospice agency, and possibly with the coroner or medical
examiner as well.
Securing a Private Room
If the patient is in an open ward or undivided Intensive
Care Unit (ICU) and the institution seems cooperative, you
shold ask for transfer to a private room or cubicle
(preferably near an exit) to minimize disruption and attract
as little attention as possible during stabilization and
removal. If the patient is unequivocally terminal, reassure
the hospital that the cryonics organization (if it is their
policy) will pay for the added expense of a private room.
Evaluating the Patient's Condition
Once the basic administrative and physical details outlined
above have been dealt with, the team leader should see the
patient and to ask to examine the chart. A general
assessment of the patient should be made at this time, and
the evaluation should be carefully recorded with proper
notes.
Is the patient alert and oriented as to person, place, and
time? Is the patient comatose? What is the patient's fluid
status: edematous, dehydrated, in balance? Whenever
possible, obtain a photocopy of the recent medical history
and daily "graphic record" from the nursing staff or the
attending physician. This may be difficult, and you may have
to use the Patient's Directive and Power of Attorney. You
should be concerned with the current status and status for
the previous 24 hours of the following key items:
Temperature
Blood Pressure
Pulse
Neurological Status (see Table 1, Glasgow/Pittsburgh Coma
Scale)
Fluid Balance (pulmonary edema?)
Hematological Status (bleeding or coagulopathies?)
Laboratory Test Results
Medications Currently Being Administered (or given during
the previous 48 hours)
Surgical/Diagnostic Procedures
Unusual Findings
Prognosis
The patient's temperature and fluid balance are of primary
importance, since they can profoundly affect the course and
quality of resuscitation and stabilization. If a patient is
markedly febrile (running a temperature), CPR will be even
less effective at meeting metabolic demand than normal.
Remember to note this on the transport records. Likewise,
the presence of edema will affect the efficacy of CPR due to
diminished lung gas-exchange surface area. Severe
dehydration could mean inadequate circulating blood volume
and thus inadequate blood pressure and tissue perfusion
during CPR.
Predicting Cardiac Arrest
Once you have evaluated the patient's condition, you should
try and establish a probable time of legal death. Is the
patient likely to experience cardiac arrest in a few
minutes, a few hours, or a few days? Your assessment will
profoundly affect every aspect of the standby operation.
Obviously, if the start of ischemia is only minutes away,
you will need to summon essential support personnel (such as
the cooperating mortician or ambulance service). You will
also need to begin drawing up medications.
On the other hand, if the life expectancy seems likely to be
numbered in days rather than minutes, your most immediate
priority will be to determine where to situate yourself.
I cannot overstate the importance of making a reasonably
accurate assessment of when cardiac arrest is likely to
occur. Typically, there will be only one set of transport
medications available on-site for a local or remote standby.
Once the medications have been drawn up, they must be used
(even if promptly refrigerated) within no more than 24-48
hours. If your estimate of the patient's condition is
incorrect, you may find yourself lacking transport
medications when they are needed.
The overall level of readiness may be even more important
than the issue of when to draw up medications. There is
almost no disaster more demoralizing (short of not being
able to cryopreserve the patient at all) than being
unprepared when the patient experiences cardiac arrest. Here
again, assessing the patient with a reasonable degree of
reliability is vital, particularly when essential transport
personnel must be located off-site for any reason.
Unfortunately, a general assessment is rarely
straightforward. Human beings are complex, and many factors
will determine when this complex system fails. Nevertheless,
there are a few useful guidelines. it should be noted that
using these "markers" as predictors with any precision
requires both skill and experience. Whenever possible, the
transport technician should trust the judgment of those who
have the greatest clinical experience. In particular, the
nurses caring for the patient may be able to tell with a
fair degree of accuracy when the patient will experience
legal death. You should ask them for an assessment and give
their estimations considerable weight.
Key Factors to Consider
There are two fundamental ways that a patient can experience
cardiac arrest: acutely, as a result of very rapid
destabilization (perhaps cardiac arrhythmia or hemorrhage),
or slowly (perhaps as a result of decompensation and shock).
The presence of arrhythmias--which can precipitate sudden
cardiac arrest--can be disclosed by discussing the patient's
condition with the nursing staff providing care. The range
of cardiac conditions that can lead to sudden cardiac arrest
is large, and a detailed discussion of the risk factors for
sudden cardiac arrest is beyond the scope of this guide.
Also, the presence of arrhythmias that are linked to sudden
cardiac arrest is usually not going to be very useful in
determining with any degree of precision when the patient i!
s going to arrest.
Arrhythmias
Having said this, there a few specific guidelines that can
be given. Some cardiac arrhythmias are a cause for concern
only in the context of the patient's overall condition. For
example, premature ventricular contractions (PVCs) may occur
in a variety of disease states, especially following acute
myocardial infarction. Depending upon their nature and
frequency, they may or may not be serious. However, in a
patient who is entering the agonal shock period, the
appearance of PVCs should be great cause for concern. If the
PVCs become frequent, occur in runs, or are accompanied by
the R-on-T phenomenon, you should be alert for the
possibility of impending cardiac arrest. Even if the patient
does not arrest as a result of the arrhythmia, it may
indicate that shock is deepening and that cardiac arrest may
be close.
One arrhythmia which demands serious attention is
ventricular tachycardia (V-Tach). When it is observed in a
terminal patient, this arrhythmia must always be viewed as a
precursor to ventricular fibrillation and cardiac arrest.
Treatment is normally (in a non-terminal patient) immediate
and very aggressive, usually through a combination of drugs
and cardioversion (electric shock delivered to the heart).
When V-Tach is observed in a terminal cryopreservation
patient, the transport technician should alert other team
members (waking them if necessary), lay out medications, and
take all other necessary steps to insure readiness. Since V-
Tach can sometimes be sustained for hours, it is probably
not wise to draw-up transport medications. However, if the
V-Tach is associated with evidence of inadequate perfusion,
such as a fall in blood pressure or alteration in
consciousness, final preparation of transport medications
should be undertaken.
Evaluating Tissue Perfusion
Shock is the pathway to all non-sudden cardiac arrest and
the Transport Technician should understand its elements and
the many ways in which it can present itself. Simply put,
shock is inadequate blood flow or inadequate tissue
perfusion as a result of decompensation or frank failure in
one or more of the homeostatic mechanisms responsible for
delivering blood flow to tissues. Shock can result from the
following factors, individually or in combination:
inadequate cardiac output secondary to a diseased or failing
heart, inadequate distribution of a very large cardiac
output, or insufficient blood volume for the heart to pump.
In turn, the possible causes of pump failure or inadequate
volume could be many. Hemorrhage may deplete circulating
volume, and so may altered capillary permeability, which
allows vascular fluids to leak out of the circulatory system
and into the tissues. Whatever the cause, shock is the
proximate cause of all slow death.
Low blood pressure is often, but not always, associated with
shock. A patient who is in shock may have a centrally
measured mean arterial pressure of 70 mm Hg, and yet have
grossly inadequate perfusion of limbs and even core organs.
The critical element is not pressure or even "flow," but
adequate perfusion. In septic shock, for instance, flows may
be very high and yet be inadequate. The point is that the
patient has to be considered as a unit and in context,
rather than on the basis of any isolated number. The
assessment points given below are designed to help you to
make that assessment. Beware, there is no "royal road" to
achieving clinical skill in patient assessment.
Level of Consciousness
The patient's level of consciousness, considered with the
patient's diagnosis and the other factors below, is one of
the most valuable and easily evaluated indicators. The body
will maintain cerebral perfusion as long as possible, often
at the expense of other organ systems. Thus, when
From:
Date: 30 Jul 94 00:00:00 GMT
To:
Subject: cryonics: #2948-#2949 (2/2)
Status: R
compromises in neurological function occur as a result of
shock, they are often evidence of the final phase of
decompensation. If the patient has been conscious and the
level of consciousness deteriorates, it may be an ominous
sign that cardiac arrest is approaching.
Similarly, changes in the patient's demeanor may be
critical. Combativeness and hallucinations are two of the
earliest signs of cerebral hypoperfusion and should be given
considerable weight when you evaluate the likely time to
cardiac arrest. In order to evaluate these changes
objectively, you will need to interrogate the patient. Some
guidelines are presented below. When performing an
evaluation, always compare the left side of the body with
the right and current responses with prior responses.
Cortical Function
Assess Response to External Stimuli
* Degree of stimulus required to elicit a response
* Degree of response to the stimuli (use the
Glasgow/Pittsburgh Coma Scale; see Table 3-1)
* Presence of weakness or loss of function
* Progression of deterioration
Assess Mental Status and Cognitive Function
* Short-term memory
* Long-term memory
* Calculation
* Reasoning
* Orientation to person, place and time
Assess Motor Function
* Compare the left side with the right side
* Muscle strength, pushing or pulling against resistance
* Grip strength
* Motor speech--assess for motor aphasia
In patients who are obtunded or comatose, it is important to
evaluate cranial nerve function. Deteriorating cranial nerve
function should be considered a warning sign that cardiac
arrest is usually no more than four to six hours away.
Cranial Nerve Function
* Assess pupil reaction, size and shape. Pupils should be
round and equal in size within 1-2 mm.
* Pupil reaction to bright light should be brisk. Shine a
light in one eye and check for constriction of the pupil.
Check the other eye, too. Through internuncial pathways, it
should mimic the response of the eye that is exposed to
light. This is known as a consensual response. Pupillary
responses should be carefully documented during the agonal
phase since failed pupillary reactivity is probably an
indication of gross cerebral hypoperfusion or total
ischemia.
[insert tables and charts]
The lower the combined total score of the two scales, the
worse the patient's condition and the shorter the likely
time interval to cardiac arrest. Maximum possible score: 30.
Minimum possible score: 9.
At the end of this chapter you will find a worksheet to
evaluate the patient using the Glasgow/Pittsburgh Coma
Scale.
Reflexes
* Assess the corneal reflex by briefly and lightly touching
the corneas with a piece of cotton or soft gauze. The eyes
should close.
* Assess the blink reflex by touching the eyelashes lightly.
The eyes should close.
* Assess the Babinski reflex by stroking the exposed skin of
the sole of the foot. Moving upward from the heel, stroke
the outer edge of the sole and then stroke across the ball
of the foot. The toes should curl down in response. If the
big toe moves upward toward the knee and the other toes
flare out, the reflex is positive, which is abnormal in
someone who has learned to walk and, during shock, may
indicate cerebral hypoperfusion.
* Assess joint reflexes by tapping the limb with a reflex
hammer to stretch the tendon. In a normal functioning state,
the limb should move to shorten the tendon.
Cardiovascular Assessment
Central Circulation
One of the first, most important, and easiest things to
assess is the patient's circulation. Look for a bluish tint
in the mucous membranes of the conjunctivae and the lips,
indicating the presence of an increased amount of reduced
hemoglobin (central cyanosis). An important caveat about
cyanosis is that (as will be discussed in greater detail
shortly in the section on pulse oximetry) cyanosis may not
be evident even in the presence of marked hypoxia or shock
if the patient's hemoglobin is 5g/dl or less. Symptoms which
may accompany cyanosis (and/or hypoxia when cyanosis is not
present, i.e. during severe anemia) are tachycardia
(increased heart rate), tachypnea (increased breathing
rate), and dyspnea (shortness of breath) and confusion
and/or hostility or combativeness.
Peripheral Circulation
When a patient is agonal and the body is attempting to
compensate for failure of one or more homeostatic
mechanisms, circulation to the brain and core organs tends
to be maintained at the expense of other areas. Usually, the
body shunts blood flow away from organ systems which can
tolerate periods of reduced or absent flow, such as the
limbs, skin, and the gastrointestinal system. In such
patients, the peripheral circulation usually becomes
compromised in a very consistent fashion. As the more distal
parts of the body (such as the lower extremities) begin to
experience failed perfusion, you should notice pallor,
cooling, and an increase in capillary refill time beyond two
seconds. The nail beds will loose their normal pink color
and become cyanotic, and the arms and legs will become cool
to the touch.
When capillary refill times increase to four or more
seconds, the limbs assume a mottled purplish appearance. In
some cases there may even be signs of dependent lividity
where blood in the limb, under the influence of gravity,
settles into the most dependent part of the tissues. This is
normally a postmortem change but it may also be seen in
patients with very protracted agonal courses; particularly
in AIDS patients, the extremely elderly, and in patients
dying of dehydration. If you notice these changes in a
patient's circulation--particularly in conjunction with
abnormalities in vital signs (low blood pressure or pulse),
you should expect that cardiac arrest will occur within a
few hours at most.
Vital Signs
Primary vital signs are generally defined as blood pressure,
pulse rate, and respiratory rate. In many situations, these
signs may be a reliable guide to the agonal time course. Of
course, the patient's underlying condition and status will
also have considerable relevance. For instance, extreme
tachycardia (elevated heart rate) will be tolerated far
longer in a young marathon runner in shock after an accident
than in an 86-year-old heart-attack victim. Still, there are
certain vital signs which cannot be tolerated by any
individual. A peak systolic blood pressure of 50 mm of
mercury or less is seldom tolerated by the heart for more
than an hour. Terminal patients (i.e., those in whom no
resuscitation intervention is planned) with peak systolic
pressures of 50 mm or less should be considered frankly
agonal and in imminent danger of cardiac arrest. Sustained
peak systolic pressures below 80 mm Hg should also be
considered cause for concern, particularly in the presence
of other abnormal vital signs (tachycardia, bradycardia, or
Cheyne-Stokes respiration) or evidence of peripheral
vascular shutdown. On the other hand, if a patient's
systolic blood pressure is 70 mm Hg while the other vitals
appear stable and central and peripheral perfusion are good,
the low blood pressure is probably not predictive.
---------------------------------------------------------
NOTE: Blood pressure readings are given as the systolic
pressure over the diastolic pressure; for example, 120/70. A
few adults may have very low normal blood pressure, even as
low as 70 systolic. The difference between the patient's
normal pressure and the current pressure may be more
relevant than an absolute value.
------------------------------------------------------------
It is very important to remember that for arterial pressure
to be measured reliably, you need a central catheter rather
than a cuff. Quite commonly, a cuff-measured pressure may be
nonexistent or very low, while a reading of central arterial
systolic pressure may be 80 or even 100 mm Hg.
Tachycardia and bradycardia are also indicators of impending
cardiac arrest, particularly when considered in light of
other vitals signs. Typically, heart rates higher than 150
to 175 bpm are not sustainable for more than a few hours.
Heart rates over 120 bpm are cause for concern, particularly
if the blood pressure is less than 100 mm Hg or other signs
of decompensation such as peripheral vascular shutdown are
present.
In the case of bradycardia, it must always be assessed in
the context of the patient's overall condition. Some
patients can tolerate heart rates in the range of 30 to 40
bpm for extended periods of time, particularly if the
bradycardia is a result of a conduction defect(s) and has
developed over a long period. Alternatively, a patient in
serious distress who is classified as "dying" and has a
heart rate of 40 bpm (down from a normal or elevated heart
rate) should be considered at high risk for imminent cardiac
arrest.
The respiratory rate varies so widely, it cannot be used as
an indicator by itself. However, Cheyne-Stokes syndrome (a
respiratory pattern consisting of stepped, sonorous intakes
of air; see Glossary for details) is a frankly agonal sign
when coupled with other abnormalaties in vitals. If it is
present, the transport technician should prepare for cardiac
arrest within 24 to 48 hours or less. Very low respiratory
rates or respiration characterized by increasingly long
periods of abpnea (transient cessation of breathing) should
also be considered prognostic of impending cardiac arrest.
The "death rattle" is a fairly distinctive bubbling or
gurgling respiration which results from a combination of
impaired consciousness and mucous accumulation. This is a
very reliable sign that cardiac arrest is near, although
there are occassional exceptions. Finally, the presence of
so-called classical shock, as indicated by hypotension (low
blood pressure) with tachycardia and diaphoresis (sweating),
should be considered a serious warning sign. If the
patient's skin is cold and clammy, respirations are fast and
shallow, and blood pressure is low, the patient can be
considered in shock and not far from cardiac arrest.
Figure 6-4: Correlation of mean arterial pressure (MAP) and
heart rate in a patient dying from dehydration and pulmonary
insufficiency (secondary to end-stage adenocarcinoma of the
lungs) with clinical signs and occurrence of cardiac arrest.
Urine Output/Fluid Status
Urine output is probably the second most important general
indicator of the progression of shock. When a dying patient
becomes oliguric (defined as less than 30 cc of urine output
per hour) or anuric (no urine output), it is a sign that the
kidneys are no longer receiving adequate blood flow and
cardiac arrest can be expected within hours or, at the
extreme, a day or two. Note that oliguria and anuria can
only be assessed accurately and reliably if the patient has
a bladder catheter.
Some moribund patients may have a naturally low urinary
output, resulting in long periods (up to a day) between each
instance of urination and the next. This should not be
mistaken for anuria.
Laboratory Measurements
There are clinical laboratory tests and measurements which
can help in assessing the time to cardiac arrest, but when a
terminal patient is receiving orthodox treatment, these
tests are seldom performed. If a patient still has some
chance of recovery and is receiving acute care in an ICU or
CCU, you are more likely to get useful data such as the
following:
Arterial Oxygen Tension
A paO2 (the concentration of oxygen in the blood) of less
than 70 mm Hg in a patient breathing 100% oxygen on a
ventilator is an indicator that cardiac arrest may be
imminent.
Blood Lactate
Metabolic acidosis with elevated blood lactate levels (over
1 mEq/dl) indicates inadequate perfusion.
pH
Blood pH of less than 7.25 (with normal pCO2 levels) is
another indication of terminal shock.
[insert tables and captions]
Table 3-2 gives normal and crisis values for blood gases and
chemistries. Memorizing these values is essential for rapid
assessment of a patient's status in a difficult emotionally
stressful situation. The Transport Technician should commit
these values to memory and review them frequently.
Pulse Oximetry
You should now understand that it's seldom easy to determine
when a patient is going to experience cardiac arrest.
Recently, a tool has come into use in the cryonics community
which promises to objectify this process somewhat and
provide a more reliable measure of when a patient is
becoming frankly agonal by providing a very reliable
indicator of the patient's overall perfusion status.
This device is the pulse oximeter. It has a number of
advantages over all of the assessment techniques described
above. It is simple, accurate, noninvasive, painless, and
easy to use, giving continuous information about a patient's
pulse and perfusion status. The pulse oximeter consists of
either two or three components: the oximeter module, a cable
with sensor (which is applied to the patient), and if the
unit is portable with internal, rechargeable batteries: it
will have a separate power supply/charger!
.
Figure 6-5: Pulse Oximeter: oximeter, photodetector, sensor
placement.
The sensor contains two diodes emitting red and infrared
light which is picked up by a photodetector after it has
passed through human tissue. In some pulse oximeters, the
detector is placed opposite the emitting diodes, with an ear
lobe or fingertip in between. In other units, the light is
detected after it has penetrated tissue and reflected off
internal bone, typically in the patient's forehead.
Some units combine both modes of operation, to allow maximum
flexibility of probe placement. This is especially important
for cryonics purposes where poor perfusion may persist for
many hours. In such cases, you should be able to use areas
such as the bridge of the nose or the forehead, where
perfusion usually persists until the very end.
Regardless of whether the unit uses transmittance,
reflectance, or both, it works on the principle that oxygen
content will alter the light-absorbing characteristics of
hemoglobin in the arterial blood supply. Thus, the pulse
oximeter provides a reliable guide to arterial oxygen
saturation, at the same time that it monitors the patient's
pulse.
Usually, there will be an alarm that can be preset to values
for pulse rate and saturationa selected by the operator.
There will be another alarm preset to values which cannot be
overridden.
In a terminally ill cryonics patient, assuming the patient
and family are cooperative, pulse oximetry should be used as
soon as possible and should be continued for as long as
possible. There are no exceptions to this rule. Any patient
who has been diagnosed as terminal is at increased risk of
sudden cardiac arrest, and pulse oximetry enables a constant
24-hour vigil.
The importance of this cannot be overstated. Decompensation
may occur suddenly, particularly in cases where the patient
is elderly, has heart disease, has active orb potential for
active bleeding, or has chronic obstructive pulmonary
disease (such as emphysema or pulmonary fibrosis). The
emergency can easily occur when no one is around or when a
sitter or registry nurse has fallen asleep.
Similarly, younger patients who are at risk of sudden
decompensation, such as those with heart disease,
arrhythmias, electrolyte imbalance, or risk of bleeding
(such as patients with gastric or esophageal tumor
involvement) must be continuously monitored to avoid cardiac
arrest occurring without advanced warning.
Figure 6-6: Vital signs and pulse oximetery data in a 55-
year old male AIDS patient. This patient was in peak
physical condition 2-years prior to onset of his illness
(runner/weightlifeter). Note the extended period of time
which these reserves allowed the patient to tolerate poor
perfusion.
Pulse Oximetry Crisis Values
You should become more vigilant when oxygen saturation drops
to 90% or below. If the patient becomes agitated or is
moved, this may result in false low saturation readings.
However, they may also signal the onset of cerebral hypoxia,
and you should take great care to do a complete evaluation
including a pulse oximetry reading.
As saturation declines below 80%, cardiac arrest is usually
imminent (typically 24 hours or less), and changes in vital
signs, mentation, and tissue perfusion will become more
pronounced.
Setting Up and Troubleshooting the Pulse Oximeter
A variety of oximeters may be in use throughout the cryonics
community in the coming years. For specific guidance, follow
the manufacturers' instructions carefully. In general,
however, the following guidelines should apply:
Check the cable and probe.
Clean the probe with alcohol as recommended by the
manufacturer.
Change the site used for measurement every four to six hours
as needed to reduce vasoconstriction and accompanying false
"low" readings. (This will also reduce the chance of
ischemic damage to the skin from compression by the probe or
probe holder.)
If the room is brightly lit, there will be a risk of false
readings. Guard against this by covering the site where the
probe is applied in such situations.
Initially, if the patient finds forehead or earlobe
monitoring uncomfortable or distressing, you can apply the
probe to a finger or toe. As the perfusion status
deteriorates, however, the patient's level of consciousness
may diminish to the point where you can shift the probe to
an ear lobe without causing undue distress. Ultimately, as
even the ear lobe experiences diminished perfusion, the
forehead or the bridge of the nose can be used.
Caveats on Pulse Oximetry
Perhaps the most important caveat to pulse oximetry is that
it can only be effective if you use it. In fact, if you use
the pulse oximeter inconsistently, this may create a false
sense of confidence. Similarly, if the unit is not operating
properly it constitutes a serious hazard. In the complete
absence of pulse oximetry, other methods of monitoring the
patient will be used; but this will not be the case if you
are placing your trust in the monitoring equipment.
One final caveat is also in order. Pulse oximetry is not a
reliable indicator of hypoxia or inadequate tissue perfusion
in cases of severe anemia where the patient's hemoglobin is
less than 8 g/100 ml. In such instances, hemoglobin oxygen
saturation may be reported by the oximeter as adequate (as
indeed it is), but the amount of hemoglobin available to
deliver oxygen to the tissues is not adequate, and oximetry
will not indicate the true state of affairs until very near
the time of cardiac arrest (minutes to an hour). Thus, in
cases of severe anemia, you must use other methods in
addition to pulse oximetery to assess the patient's
perfusion status.
Similarly, in cases where the amount of abnormal hemoglobin
(carboxyhemoglobin, methemoglobin or sulfhemoglobin) is
greater than 3% to 4%, pulse oximetry will not be a reliable
indicator. Increased bilirubin levels which occur in
jaundice secondary to liver failure (a common occurrence in
end-stage cardiac, cancer, and hepatic disease patients) can
also cause false readings, indicating low saturation.
Saturation may also be "falsely" depressed in cases of
peripheral vascular disease or when vasoconstricting
medication is being used.
Graph Your Data
Taking all the readings and gathering the data as outlined
above is important and is the first step. However it is of
only limited usefulness unless the data is presented in a
way that lets you spot *trends*. Thus it is very important
that you graph data in real time. Heart rate, blood
pressure (preferably as mean arterial pressure (MAP))
respiratory rate and mixed blood oxygen saturation should
all be plotted graphically, preferably on the same sheet of
graph paper. This will allow you to spot trends early and
being making preparations.
Study the graphics of the two patients' agonal vitals
presented in this chapter. In both cases trends were
important. In one case (patient A-1049) the trend of
increased heart rate and steadily dropping blood pressure
was highly predictive. This is almost a textbook case; when
the patient's systolic blood pressure dropped below 50 mmHg
she expired very shortly thereafter. Maintaining a graphic
record can tip you off to the beginning of the final spiral
of decompensation precious hours before you might have
noticed it otherwise.
A Final Note
Generally, shock is not tolerable for more than a few hours,
particularly in chronically ill and debilitated patients.
You should rely on nursing staff to assess whether a patient
is experiencing shock and how much time may remain until
cardiac arrest.
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