Download DRUG THERAPY IN ANESTHESIOLOGY AND RESUSITATION

DRUG THERAPY IN
ANESTHESIOLOGY AND
RESUSITATION
General anesthesia
General anesthesia is the induction of a state of
unconsciousness with the absence of pain sensation
over the entire body, through the administration of
anesthetic drugs.
It is used during certain medical and surgical procedures.
General anesthesia has many purposes including:
• pain relief (analgesia)
• blocking memory of the procedure (amnesia)
• producing unconsciousness
• inhibiting normal body reflexes to make surgery safe
and easier to perform
• relaxing the muscles of the body
General Anesthesia (cont’d)
Anesthesia performed with general anesthetics
occurs in four stages which may or may not be observable
because they can occur very rapidly:
• Stage One: Analgesia. The patient experiences analgesia
or a loss of pain sensation but remains conscious
and can carry on a conversation.
• Stage Two: Excitement. The patient may experience
delirium or become violent. Blood pressure rises and
becomes irregular, and breathing rate increases. This
stage is typically bypassed by administering a barbiturate,
such as sodium pentothal, before the anesthesia.
General Anesthesia (cont’d)
• Stage Three: Surgical Anesthesia. During this stage, the
skeletal muscles relax, and the patient’s breathing
becomes regular. Eye movements slow, then stop, and
surgery can begin.
• Stage Four: Medullary Paralysis. This stage occurs if
the respiratory centers in the medulla oblongata of the
brain that control breathing and other vital functions
cease to function. Death can result if the patient cannot
be revived quickly. This stage should never be reached.
Careful control of the amounts of anesthetics administered
prevent this occurrence.
GENERAL ANESTHESIA
Agents used for general anesthesia may be either
gases or volatile liquids that are vaporized and inhaled
with oxygen, or drugs delivered intravenously. A combination
of inhaled anesthetic gases and intravenous drugs
are usually delivered during general anesthesia; this
practice is called balanced anesthesia and is used because
it takes advantage of the beneficial effects of each anesthetic
agent to reach surgical anesthesia. If necessary, the
extent of the anesthesia produced by inhaling a general
anesthetic can be rapidly modified by adjusting the concentration
of the anesthetic in the oxygen that is breathed
by the patient. The degree of anesthesia produced by an
intravenously injected anesthesic is fixed and cannot be
changed as rapidly. Most commonly, intravenous anesthetic
agents are used for induction of anesthesia and
then followed by inhaled anesthetic agents.
General anesthesia
When general anesthesia was first introduced in
medical practice, ether and chloroform were inhaled with
the physician manually covering the patient’s mouth.
Since then, general anesthesia has become much more
sophisticated. During most surgical procedures, anesthetic
agents are now delivered and controlled by computerized
equipment that includes anesthetic gas monitoring
as well as patient monitoring equipment. Anesthesiologists
are the physicians that specialize in the delivery of
anesthetic agents. Currently used inhaled general
anesthetics include halothane, enflurane,
isoflurane, desfluorane, sevofluorane, and
nitrous oxide.
General anesthesia
Commonly administered intravenous anesthetic agents
include ketamine, thiopental, opioids, and propofol.
Ketamine (Ketalar) affects the senses, and produces a
dissociative anesthesia (catatonia, amnesia, analgesia)
in which the patient may appear awake and reactive, but
cannot respond to sensory stimuli. These properties
make it especially useful for use in developing countries
and during warfare medical treatment. Ketamine is
frequently used in pediatric patients because anesthesia
and analgesia can be achieved with an intramuscular
injection. It is also used in high-risk geriatric patients
and in shock cases, because it also provides cardiac
stimulation.
General anesthesia
Thiopental (Pentothal) is a barbiturate that
induces a rapid hypnotic state of short
duration. Because thiopental is slowly
metabolized by the liver, toxic
accumulation can occur; therefore, it
should not be continuously infused. Side
effects include nausea and vomiting
upon awakening.
General anesthesia (cont’d)
Opioids include fentanyl, sufentanil, and alfentanil, and
are frequently used prior to anesthesia and surgery as a
sedative and analgesic, as well as a continuous infusion
for primary anesthesia. Because opioids rarely affect
the cardiovascular system, they are particularly useful
for cardiac surgery and other high-risk cases. Opioids
act directly on spinal cord receptors, and are freqently
used in epidurals for spinal anesthesia. Side effects may
include nausea and vomiting, itching, and respiratory
depression.
General anesthesia (cont’d)
• Propofol (Diprivan) is a nonbarbiturate hypnotic agent
and the most recently developed intravenous anesthetic.
Its rapid induction and short duration of action are identical
to thiopental, but recovery occurs more quickly
and with much less nausea and vomiting. Also, propofol
is rapidly metabolized in the liver and excreted in
the urine, so it can be used for long durations of
anesthesia, unlike thiopental. Hence, propofol is rapidly
replacing thiopental as an intravenous induction agent.
It is used for general surgery, cardiac surgery,
neurosurgery, and pediatric surgery.
General anesthesia (cont’d)
General anesthetics are given only by anesthesiologists,
the medical professionals trained to use them. These
specialists consider many factors, including a patient’s
age, weight, medication allergies, medical history, and
general health, when deciding which anesthetic or
combination of anesthetics to use. General anesthetics
are usually inhaled through a mask or a breathing tube
or injected into a vein, but are also sometimes given
rectally.
General anesthesia is much safer today than it was in
the past. This progress is due to faster-acting anesthetics,
improved safety standards in the equipment used to
deliver the drugs, and better devices to monitor breathing,
heart rate, blood pressure, and brain activity during
surgery. Unpleasant side effects are also less common.
General anesthesia
Precautions
Patients who have had general anesthesia
should not drink alcoholic beverages or
take medication that slow down the
central nervous system (such as
antihistamines, sedatives, tranquilizers,
sleep aids, certain pain
relievers, muscle relaxants, and antiseizure medication) for at least 24 hours,
except under a doctor’s care.
LOCAL ANESTHESIA
Local or regional anesthesia involves the injection or
application of an anesthetic drug to a specific area of the
body, as opposed to the entire body and brain as occurs
during general anesthesia.
Local anesthetics are used to prevent patients from
feeling pain during medical, surgical, or dental procedures.
Over-the-counter local anesthetics are also available
to provide temporary relief from pain, irritation, and
itching caused by various conditions, such as cold sores,
canker sores, sore throats, sunburn, insect bites, poison
ivy, and minor cuts and scratches.
LOCAL ANESTHESIA
Types of surgery or medical procedures that regularly
make use of local or regional anesthesia include the
following:
• biopsies in which skin or tissue samples are taken for
diagnostic procedures
• childbirth
• surgeries on the arms, hands, legs, or feet
• eye surgery
• surgeries involving the urinary tract or sexual organs
Surgeries involving the chest and abdomen are usually
performed under general anesthesia.
Local and regional anesthesia have advantages over
general anesthesia in that patients can avoid some
unpleasant side effects, can receive longer lasting pain
relief, have reduced blood loss, and maintain a sense of
psychological comfort by not losing consciousness.
Regional anesthesia
Regional anesthesia typically affects a larger area than
local anesthesia, for example, everything below the waist.
As a result, regional anesthesia may be used for more
involved or complicated surgical or medical procedures.
Regional anesthetics are injected. Local anesthesia involves
the injection into the skin or muscle or application to the
skin of an anesthetic directly where pain will occur. Local
anesthesia can be divided into four groups: injectable,
topical, dental (non-injectable), and ophthalmic.
Types of regional anesthesia include:
• Spinal anesthesia. Spinal anesthesia involves the
injection of a small amount of local anesthetic directly
into the cerebrospinal fluid surrounding the spinal cord
(the subarachnoid space). Blood pressure drops are com
mon but are easily treated.
• Epidural anesthesia. Epidural anesthesia involves the
injection of a large volume of local anesthetic directly
into the space surrounding the spinal fluid sac (the
epidural space), not into the spinal fluid. Pain relief
occurs more slowly but is less likely to produce blood
pressure drops. Also, the block can be maintained for
long periods, even days.
Types of regional anesthesia include
(cont’d):
• Nerve blocks. Nerve blocks involve the injection of an
anesthetic into the area around a nerve that supplies a
particular region of the body, preventing the nerve from
carrying nerve impulses to the brain.
Anesthetics may be administered with another drug,
such as epinephrine (adrenaline), which decreases
bleeding, and sodium bicarbonate to decrease the
acidity of a drug so that it will work faster. In addition,
drugs may be administered to help a patient remain calm
and more comfortable or to make them sleepy.
INJECTABLE LOCAL ANESTHETICS. These medicines
are given by injection to numb and provide pain relief to
some part of the body during surgery, dental procedures,
or other medical procedures. They are given only by a
trained health care professional and only in a doctor’s
office or a hospital. Some commonly used injectable
local anesthetics are procaine (Novocain), lidocaine
(Dalcaine, Dilocaine, L-Caine, Nervocaine, Xylocaine,
and other brands), and tetracaine (Pontocaine).
TOPICAL ANESTHETICS. Topical anesthetics, such as
benzocaine, lidocaine, dibucaine, pramoxine, butamben,
and tetracaine, relieve pain and itching by deadening the
nerve endings in the skin. They are ingredients in a variety
of nonprescription products that are applied to the
skin to relieve the discomfort of sunburn, insect bites or
stings, poison ivy, and minor cuts, scratches, and burns.
These products are sold as creams, ointments, sprays,
lotions, and gels.
DENTAL ANESTHETICS (NON-INJECTABLE). Some
local anesthetics are intended for pain relief in the mouth
or throat. They may be used to relieve throat pain,
teething pain, painful canker sores, toothaches, or discomfort
from dentures, braces, or bridgework. Some
dental anesthetics are available only with a doctor’s prescription.
Others may be purchased without a prescription,
including products such as Num-Zit, Orajel, Chloraseptic
lozenges, and Xylocaine.
OPHTHALMIC ANESTHETICS. Other local anesthetics
are designed for use in the eye. The ophthalmic anesthetics
proparacaine and tetracaine are used to numb the eye
before certain eye examinations. Eye doctors may also use
these medicines before measuring eye pressure or removing
stitches or foreign objects from the eye. These drugs
are to be given only by a trained health care professional.
Precautions
People who strongly feel that they cannot psychologically
cope with being awake and alert during certain
procedures may not be good candidates for local or
regional anesthesia. Other medications may be given in
conjunction with the anesthetic, however, to relieve anxiety
and help the patient relax.
Local anesthetics should be used only for the conditions
for which they are intended. For example, a topical
anesthetic meant to relieve sunburn pain should not be
used on cold sores. Anyone who has had an unusual reaction
to any local anesthetic in the past should check with
a doctor before using any type of local anesthetic again.
The doctor should also be told about any allergies to
foods, dyes, preservatives, or other substances.
Side effects of regional or local anesthetics
A physician should be notified immediately if any of
these symptoms occur:
• large swellings that look like hives on the skin, in the
mouth, or in the throat
• severe headache
• blurred or double vision
• dizziness or lightheadedness
• drowsiness
• confusion
• anxiety, excitement, nervousness, or restlessness
• convulsions (seizures)
• feeling hot, cold, or numb
• ringing or buzzing in the ears
• shivering or trembling
• sweating
• pale skin
• slow or irregular heartbeat
• breathing problems
• unusual weakness or tiredness
CARDIOPULMONARY RESUSCITATION
Cardiopulmonary resuscitation, commonly called CPR,
combines rescue breathing (one person breathing into another
person) and chest compression in a lifesaving procedure
performed when a person has stopped breathing or a person's
heart has stopped beating.
When performed quickly enough, CPR can save lives in
such emergencies as loss of consciousness, heart attacks or
heart "arrests," electric shock, drowning, excessive bleeding,
drug overdose, and other conditions in which there is no
breathing or no pulse. The purpose of CPR is to bring oxygen
to the victim's lungs and to keep blood circulating so oxygen
gets to every part of the body. When a person is deprived of
oxygen, permanent brain damage can begin in as little as four
minutes and death can follow only minutes later.
CARDIOPULMONARY RESUSCITATION
There are three physical symptoms that
indicate a need for CPR to be performed
immediately and for emergency medical support
to be called:
• unconsciousness
• not breathing
• no pulse detected
CPR in basic life support
Figure A: The victim
should be flat on his back
and his mouth should be
checked for debris. Figure
B: If the victim is
unconscious, open airway,
lift neck, and tilt head
back. Figure C: If victim is
not breathing, begin
artificial breathing with
four quick full breaths.
Figure D: Check for
carotid pulse. Figure E: If
pulse is absent, begin
artificial circulation by
depressing sternum.
Figure F: Mouth-to-mouth
resuscitation of an infant.
CARDIOPULMONARY RESUSCITATION
The steps usually followed in CPR are as follows:
• If the victim appears to be unconscious with either no breathing
or no pulse, the person should be shaken or tapped gently to
check for any movement. The victim is spoken to loudly, asking
if he or she is OK. If there is no response, emergency help must
be called and CPR begun immediately.
• The victim is placed on his or her back on a level surface such as
the ground or the floor. The victim's back should be in a straight
line with the head and neck supported slightly by a rolled up
cloth, small towel, or piece of clothing under the neck. A pillow
should not be used to support the head. The victim's clothing
should be loosened to expose the chest.
• The rescuer kneels next to the victim, tilts the victim's head back,
lifts the jaw forward, and moves the tongue forward or to the
side, making sure it does not block the opening to the windpipe.
The victim's mouth must be kept open at all times, reopening as
necessary.
CARDIOPULMONARY RESUSCITATION
• The rescuer listens close to the victim's mouth for any sign of
breathing, and watches the chest for movement. If the victim is
found to be breathing, and has perhaps fainted, he or she can be
placed in the recovery position until medical assistance arrives.
This is done by straightening the victim's legs and pulling the
closest arm out away from the body with the elbow at a right
angle or 3 o'clock position, and the other arm across the chest.
The far leg should be pulled up over the victim's body with the
hip and knee bent. This allows the victim's body to be rolled
onto its side. The head should be tilted back slightly to keep the
windpipe open. The head should not be propped up.
• If the victim is not breathing, rescue breathing begins, closing
the victim's nostrils between a thumb and index finger, and
covering the victim's mouth with the rescuer's mouth. Two slow
breaths, about two seconds each, are breathed into the victim's
mouth with a pause in between. This is repeated until the chest
begins to rise. The victim's head should be repositioned as often
as necessary during the procedure. The mouth must remain open
and the tongue kept away from the windpipe.
CARDIOPULMONARY RESUSCITATION
• When the chest begins to rise, or the victim begins to breathe on
his or her own, the rescuer looks for signs of circulation, such as
coughing or movement. If a healthcare professional has arrived
by this time, the pulse will be checked before resuming
resuscitation.
• If chest compressions are needed to restart breathing, the
rescuer will place the heel of a hand above the lowest part of the
victim's ribcage where it meets the middle-abdomen. The other
hand will be placed over the heel of the first hand, with fingers
interlocked. Keeping the elbows straight, the rescuer will lean his
or her shoulders over the hands and press down firmly about 15
times. It is best to develop an up-and-down rhythm, keeping the
hands firmly on the victim's chest.
• After the compressions, the rescuer will give the victim two long
breaths. The sequence of 15 compressions and two breaths will
be repeated until there are signs of spontaneous breathing and
circulation or until professional medical help arrives.
There are certain important precautions for rescuers to
remember in order to protect the victim and get the best result
•
•
•
•
•
•
from CPR
Do not leave the victim alone.
Do not give chest compressions if the victim has a pulse. Chest
compression when there is normal circulation could cause the
heart to stop beating.
Do not give the victim anything to eat or drink.
Avoid moving the victim's head or neck if spinal injury is a
possibility. The person should be left as found if breathing freely.
To check for breathing when spinal injury is suspected, the
rescuer should only listen for breath by the victim's mouth and
watch the chest for movement.
Do not slap the victim's face, or throw water on the face, to try
and revive the person.
Do not place a pillow under the victim's head.
Clinical death occurs when a patient's heartbeat and breathing have
stopped. Since breathing rarely continues when the heart is stopped,
clinical death is synonymous with cardiac arrest or cardiac death. The
reversal of clinical death is sometimes possible through cpr, defibrillation,
epinephrine injection, and other treatments. Resuscitation after more than
4 to 6 minutes of clinical death at normal body temperature is difficult,
and can result in brain damage.
Brain death
Brain death (irreversible cessation of all
function of the brain) means death of both
the upper brain and brain stem. A person
who is brain dead has lost both the
capacity to think and perceive, as well as
the control of basic body functions.