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‫سوره مبارکه املنافقون‬
‫آیه نهم‬
‫بسم هللا الرحمن الرحیم‬
‫ين َآم ُنوا ََل ُت ْله ُك ْم َأ ْم َو ُال ُك ْم َوََل َأ ْوََل ُد ُك ْم َعن ذ ْكر َّ‬
‫َيا َأ ُّي َها َّالذ َ‬
‫اَّلل وَ‬
‫ِ ِ ِ‬
‫ِ‬
‫ِ‬
‫ْ َ َُ َ‬
‫ْ َ‬
‫َ‬
‫َمن َيف َع ْل ذ ِل َك فأ ْول ِئ َك ُه ُم الخا ِس ُرون‪.‬‬
‫به نام خداوند بخشنده مهربان‬
‫اى كسانى كه ايمان آوردهايد [زنهار] اموال شما و‬
‫فرزندانتان شما را از ياد خدا غافل نگرداند و هر كس چنين‬
‫‪In the name of Allah, Most Gracious, Most‬‬
‫كند آنان خود زيانكارانند‪.‬‬
‫‪Merciful‬‬
‫‪Believers, do not let either your‬‬
‫‪possessions or your children divert you‬‬
‫‪from the remembrance of allah. those who‬‬
‫‪do that shall be the losers.‬‬
Monitoring of Anesthesia
Stages of Anesthesia
Stage 1: (Induction, Voluntary excitement movement), epinephrine release with
rise in RR & HR
Stage 2: (Delirium, Involuntary excitement), Loss of consciousness; Analgesia
begins; Breath holding; Self injury; Exaggerated reflexive responses to stimuli
are common, as is vomiting.
Stage 3: (General/Surgical Anesthesia),
Plane 1- Light anesthesia, Most reflexes (pedal, corneal, palpebral) are still present.
Eyeballs are in central position.
Plane 2- Medium anesthesia, Most surgeries are conducted at this level. Muscles are
relaxed. Most reflexes (pedal, corneal, palpebral) are absent. Eyeballs are in
ventromedial position.
Plane 3- Deep anesthesia, intercostal muscles are relaxed. Eyeballs are in central
position
Plane 4- Too deep. All muscles (diaphragm & intercostal m.) are paralyzed.
Stages of Anesthesia cont.
Stage 4: (Irreversible Anesthesia), Respiratory arrest, followed by circulatory
collapsed. Death.
* The key body systems responsible for the short-term wellbeing of an animal
during anesthesia and surgery
1. Central nervous system (CNS)
2. Cardiovascular system
3. Respiratory system
* For monitoring to be effective, three basic processes have to occur: early
recognition, correct interpretation of changes, and appropriate intervention.
•
Many anesthetic-induced changes in the CNS, cardiovascular, or pulmonary
system are gradually progressive over time rather than sudden events (with the
exception of anesthetic induction); therefore, if one continually monitors the
appropriate parameters it will allow early recognition of negative trends while
physiologic disturbances are still reversible.
•
It is imperative that an anesthetist never relies on just a single parameter to
monitor patient status.
Cardiovascular System
Most anesthetic agents cause a dose-dependent depression of the cardiovascular
Cardiovascular monitoring allows not only an assessment
system
of adequate circulatory function, but also provides information on
depth of anesthesia as well.
Observational techniques used for monitoring the cardiovascular system
includes:
Heart Rate and Rhythm, Pulse Strength, Capillary Refill Time
Heart Rate
* Cardiac output = HR × Stroke Volume
•
Increases in heart rate will increase cardiac output whereas decreases in heart
rate will decrease cardiac output.
•
Bradycardia frequently occurs as the anesthetic plane gets deeper and
tachycardia occurs when the anesthetic plane is too light.
•
Tachycardia can be caused by:
Painful surgical stimulation in a lightly anesthetized animal
Hypotension
Hypovolemia
Hypoxia
Hyperthermia
Hypercarbia
•
Bradycardia may be caused by:
1. Specific anesthetic drugs (opioids, alpha 2 agonists)
2. Reflex activity (mesenteric traction, intubation, oculocardiac reflex, hypertension)
3. Hypothermia
4. Hyperkalemia
5. Cardiac conduction disturbances
If anesthetic depth is determined to be appropriate, bradycardia may be treated by
anticholinergics.
Anticholinergics would be the treatment of choice for bradycardias caused by opioids,
xylazine, vagal reflex activity, and certain cardiac conduction disturbances.
Bradycardias secondary to hypothermia are often unresponsive to anticholinergics and
require rewarming of the animal for improvement.
Bradycardia as a result of hyperkalemia represents a serious disturbance in cardiac
conduction and emergency steps to reduce serum potassium would need to be
instituted.
PULSE STRENGTH
Digital palpation of the pulse from an accessible site:
Femoral artery
Auricular artery
Tail artery
Pulse pressure is the numerical difference between systolic and diastolic arterial blood
pressures. The larger the systolic/diastolic difference, the stronger the pulse feels.
A large systolic/diastolic difference resulting in good pulse strength does not always
indicate adequate tissue perfusion.
Although a good pulse is not always an absolute indication that all is going well during
anesthesia, the absence of a palpable pulse should always be considered a sign of
inadequate cardiovascular function. ???????
CRT: Capillary Refill Time (Normal = 2.5 sec.)
CRT is considered an indicator of peripheral perfusion, and a prolonged CRT is seen
during hypotension or low cardiac output states.
It is important to realize, however, that CRT is markedly influenced by arteriolar tone.
A number of conditions causing peripheral arterial vasoconstriction will prolong
CRT even though overall tissue perfusion is likely adequate.
Pain,
excitement,
hypothermia,
and
certain
drugs
(e.g.,
xylazine)
vasoconstriction and can increase CRT above the acceptable upper limit.
induce
Electrocardiography (ECG)
ECG monitors allow continuous or intermittent accumulation of heart rate and
rhythm data at different stages of an experiment.
In addition, an ECG is the only way to establish absolutely the diagnosis of
arrhythmias that might occur as a result of anesthesia or surgical manipulations.
it represents only cardiac electrical activity and does not provide an assessment of
the cardiac output or tissue perfusion, which are the more important
functional aspects of cardiovascular performance.
The ECG of most species consists of a set of waves: the p wave indicates atrial
depolarization, the QRS complex occurs during ventricular depolarization,
and the T wave represents ventricular repolarization.
ARTERIAL BLOOD PRESSURE
The majority of anesthetic agents will cause a dose-dependent depression of blood
pressure through their effects on cardiac output, vascular tone, or both and therefore
a trend of progressively decreasing blood pressure may be an indication of
excessive anesthetic depth.
Factors that contribute most notably to blood pressure (BP) are cardiac output (CO),
peripheral vascular resistance (PVR), and blood volume.
B P = CO × PVR
Therefore, in monitoring arterial blood pressure, a mean blood pressure less than
60 mm Hg is considered unacceptable for maintaining tissue blood flow.
Mean BP = diastolic BP + 0.3 (systolic BP - diastolic BP)
CENTRAL VENOUS PRESSURE
Central venous pressure (CVP) reflects the pressure in the right atrium and is an index
of cardiac filling pressure.
The factors which influence CVP are the volume of blood in the central veins, the
compliance of the right atrium during filling, central vein vascular tone, and
intrathoracic pressure.
Central venous pressure is useful when extensive blood loss, rapid fluid administration,
or fight-sided cardiac insufficiency is anticipated. Normal CVP is -1 to + 5 cm H20,
but during anesthesia the range of normal may increase to + 10 cm H20.
Low CVP indicates that the blood volume of the animal is too low for the capacity of
its vascular system.
Loss of blood volume (e.g., intraoperative hemorrhage)
An increase in vascular capacity (e.g., anesthetic induced venodilation).
High CVP indicates either hypervolemia (e.g., fluid overload) or failure of the cardiac
pump (e.g., anesthetic overdose).
Respiratory System
The major function of the respiratory system under anesthesia is to act as a gas
exchange organ.
The lung is responsible for:
1. Introduction of oxygen into the arterial blood (oxygenation)
2. Elimination of carbon dioxide from the body (ventilation)
3. Uptake and elimination of gas anesthetics when inhalation anesthesia is used
RESPIRATORY RATE
•
Looking at chest wall motion,
•
By auscultation of the thorax,
•
By observing the re-breathing bag on an anesthetic machine,
Most anesthetics are respiratory depressants and as a general rule the respiratory rate
decreases with increasing anesthetic depth.
TIDAL VOLUME
The amount of gas entering the respiratory tract during one respiratory cycle is called
the tidal volume.
An average tidal volume for most species is about 10 ml/kg.
Monitoring tidal volume is usually subjective based on the degree of chest wall motion
with each breath or the amount of movement in the re-breathing bag of the
anesthetic machine.
The volume of gas in each respiratory cycle can be measured by attaching an
instrument called a respirometer to the endotracheal tube of the animal.
MINUTE VENTILATION
Respiratory rate and respiratory volume are determined as an indication of the minute
ventilation of the animal. Minute ventilation is the product of respiratory rate and
tidal volume.
The partial pressure of CO2 in arterial blood is the major stimulus for ventilation in the
respiratory control center in the brain. It is there that anesthetics exert their
respiratory depressant effect (increased threshold and decreased sensitivity to CO2).
A decreasing minute ventilation during anesthesia may reflect a decrease in CO2
production (often seen with hypothermia) or it may reflect increased depression of
the respiratory control centers from the anesthetic drugs.
An elevation in PaCO 2 (above 60 mm Hg) indicates the need for increased minute
ventilation, through an increase in respiratory rate, volume, or both, and may also
indicate the need to decrease anesthetic depth.
Mucous Membrane Color
Pale mucous membranes: Occurs in
horses suffering from shock form
hypovolemia or pain. This finding may
accompany other signs such as cold
extremities.
Red mucous membranes: Associated
with septic or endotoxic shock when
blood pools in the capillaries and small
vessels
Cyanotic mucous membranes: The result of
severe or prolonged shock. This may be seen
along with an overlying hyperemic tone due to
the pooling of blood in the capillaries and the
cell's subsequent depletion of oxygen. This
indicated a poor prognostic sign and presents as a
high surgical and anesthetic risk
CAPNOGRAPHY
The concentration of carbon dioxide in the inspired and expired gas can be
continuously measured from the airway with capnography.
Inspired gas should contain virtually no carbon dioxide.
The peak expired CO2 is a reflection of the partial pressure of CO2 in the alveolar gas
which is equilibrated with arterial blood.
Therefore, increased values suggest hypoventilation whereas low peak expired CO2
suggests hyperventilation.
In addition to ventilatory information, capnographs can be useful in the rapid detection
of endotracheal tube malfunctions, such as a disconnect from the circuit or a kinked
or obstructed tube.
PULSE OXIMETRY
A pulse oximeter is an instrument that by means of a light source and photodetector
measures the light absorbance of tissues and indicates the level of oxygen saturation
of hemoglobin in the blood.
Adequate arterial oxygenation requires a minimum PaO 2 value greater than 60 mm Hg
(and ideally > 90 mm Hg).
A PaO 2 of 60 mm Hg corresponds to a 90% saturation of the hemoglobin in the rterial
blood.
Using a pulse oximeter, changes in hemoglobin saturation can be monitored
continuously.
When the SaOz value falls below 90% the animal is becoming hypoxemic and steps
should be taken to improve oxygenation such as:
Administering 100% oxygen
Endotracheal intubation
Assisting ventilation
BLOOD GAS ANALYSIS
The partial pressure of CO2 in arterial blood should fall between 35 and 45 mm Hg.
A PaCO 2 <35 mm Hg is defined as hyperventilation.
A PaCO2 >45 mm Hg is by definition hypoventilation.
If an animal has a PaCO2 above 60 mm Hg during anesthesia, steps should be taken to
improve ventilation, which may include endotracheal intubation, manual or
mechanical positive pressure ventilation, or decreasing the level of anesthesia as
indicated.
The partial pressure of oxygen in the arterial blood >90 mm Hg assures adequate
oxygenation (provided there is adequate tissue perfusion).
Central Nervous System
Observational techniques are particularly important when assessing the depth of
anesthesia.
High-intensity painful procedures will require a deeper level of anesthesia than
low intensity pain procedures:
Joint capsule incision
Periosteal stimulation
Fracture manipulation
Visceral or peritoneal traction
Diaphragmatic stimulation
Corneal manipulation
Manipulation of inflamed tissue
Because different pain intensities occur within a procedure as different tissues are
manipulated, the anesthetist must frequently reassess and adjust the depth of
anesthesia as is appropriate.
A good assessment of muscle relaxation can be made by monitoring jaw tone (masseter
muscle strength) in certain species.
Jaw tone is easily assessed in certain small animal species such as dogs and cats. It is
much more difficult to evaluate in rodents, sheep, and swine.
If an animal attempts to close its mouth when gentle traction is placed on the mandible
during a procedure, more anesthesia is needed.
Purposeful movement is an indication of light anesthetic depth and usually occurs in
response to painful stimulus.
Purposeful movement such as swallowing (often stimulated by the presence of an
endotracheal tube) and head shaking (seen in small laboratory animal species such
as the guinea pig) are typical indications of too light a plane of anesthesia.
Purposeful movement in response to surgical manipulation must be differentiated from
spontaneous movement which can be seen with certain anesthetic agents such as
ketamine, opioids, enflurane, and methoxyflurane and which does not occur as a
response to a surgical stimulus (although it may occur coincidentally with a
stimulus).
The pedal withdrawal reflex is commonly used to help determine the level of surgical
anesthesia in small laboratory species.
The foot is extended and the toe itself is pinched with the fingernails or gently with a
hemostat:
If the limb is withdrawn in response to
the toe pinch, then the animal will need more anesthesia before
a painful procedure can begin.
(Ocular reflexes can be used to indicate anesthetic depth)
Palpebral response
Ocular position
Corneal reflex.
The palpebral response is the blinking that occurs when the edge of the eyelid is lightly
touched.
Most animals lose the palpebral response fairly early in surgical anesthesia. In horse in
deep stage of anesthesia it will disappear and is not favorite symptom.
Rabbits may maintain a palpebral response even at deeper planes of anesthesia.
The palpebral response is lost early with barbiturates and most inhalation agents;
however, it is well-maintained with ketamine.
Ocular position is generally a reliable sign of changing anesthetic depth in many
species.
As anesthesia is induced and in light planes of anesthesia the eyeball remains central in
the orbit and a palpebral response is present.
Nystagmus and lacrimation are also indications of a light plane of surgical anesthesia.
When a surgical plane of anesthesia is reached the globe rotates ventromedially.
As anesthesia deepens (and muscle relaxation continues to increase) the globe will
again rotate upward and return to a central position in the orbit.
A centrally located globe during a deep plane of anesthesia can be distinguished from
the centrally located globe of light anesthesia by the absence of the palpebral
response during increased anesthetic depth.
The corneal reflex is another ocular reflex that changes with the changing depth of
anesthesia.
To determine the presence of a corneal reflex, the surface of the cornea is lightly
touched and the presence of a blinking response noted.
A brisk corneal reflex is found in awake animals and its intensity begins to diminish as
the plane of anesthesia deepens.
Certain species, such as ruminants, will maintain a corneal reflex during a surgical
lane of anesthesia, whereas the reflex is often absent at a surgical plane in other
species, such as the dog and cat.
Increases in heart rate, blood pressure, and respiratory rate can be seen in response to
surgical stimulation when no purposeful movement has been observed.
Thermoregulation
Most anesthetic procedures cause a depression of the hypothalamic thermoregulatory
mechanism, predisposing animals to hypothermia.
This is further compounded by the removal of hair and wetting the remaining hair coat
during aseptic preparation of the surgical site.
When this small damp animal is then placed on a cold metal surface, the result can be
fatal hypothermia.
Opening a body cavity will further accelerate the loss of body heat.
Body temperature is best monitored by a small thermistor placed into the esophagus to
the level of the heart. This will provide a closer indication of core body temperature
than a rectal thermistor because the temperature in the rectum falls more slowly
than core body temperature.
Hypothermia can be minimized by warming of surgical preparation solutions,
insulating the patient from both cool ambient temperatures and a cold restraining
surface, using warmed fluids if supplemental fluids are provided, warming of
inspired gases, and using supplemental heat provided by a circulating water
warming blanket.
Electric heating pads should be avoided as they can cause serious thermal burns and
even hyperthermia.
The End