Flashcards in Chpt. 5 - Tech Notes Deck (42):
Why is monitoring necessary?
It is necessary for two reasons:
1. It is necessary to keep the patient safe.
2. It is necessary to regulate anesthetic depth.
What is anesthetic monitoring based on?
It is based on the principle that in the average patient each monitoring parameter is expected to show a predictable response at any given anesthetic depth.
What marks the border between stages I and II?
Loss of consciousness
What marks the border between stages II and III?
Loss of spontaneous muscle movement
What marks stage IV?
Loss of all reflexes, widely dilated pupils, flaccid muscle tone, and cardiopulmonary collapse
Inadequate to perform surgery
Stage III, plane 1
Suitable for most surgical procedures
Stage III, plane 2
Considered to be excessively deep for most surgical procedures
Stage III, plane 3
Stage III, plane 4
Stage III divided into three planes
1. Light surgical anesthesia indicates an inadequate depth.
2. Medium surgical anesthesia indicates the optimum depth for most procedures.
3. Deep surgical anesthesia indicates an excessive depth.
Name the objectives of surgical anesthesia
- Pt does not move
- Pt is not aware
- Pt does not feel pain
- Pt has no memory of procedure afterward
- Pt does not have dangerous depression of the cardiovascular and respiratory systems
What should always be brought to the DVM's attention?
Disturbances in cardiac rhythm!
The DVM needs to assess this because benign arrhythmias can quickly degenerate into dangerous rhythms if not recognized and managed.
Who makes an electrocardiographic diagnosis?
Only a veterinarian!
But as a monitor the tech must be able to differentiate normal from abnormal, and dangerous from nondangerous rhythms.
What is MAP?
Mean arterial pressure
It is the average pressure through the cardiac cycle and is the most important value from the anesthetist's standpoint because it is the best indicator of blood perfusion of the internal organs.
Why is MAP a good indicator of tissue perfusion during anesthesia?
If MAP falls below 60 mm Hg, blood flow to internal organs is reduced and tissues may become hypoxic. Every effort should be made to maintain a MAP of 60 mm Hg or greater in small animals and ruminants, and 70 mm Hg or greater in horses.
Name the two indirect monitors that are most commonly used in general practice to measure BP.
The Doppler and oscillometric monitors.
Both of which use a cuff to sequentially occlude and release blood flow in a major artery of a limb or the tail. These systems differ in the way the pressure is measured.
BP cuff details
- width of cuff should be 30% to 50% of the circumference of the extremity
- cuff should be placed firmly but not too tightly over a peripheral artery
- cuff should be wrapped slightly more tightly in large animals than in small animals
- cuff should be at the same horizontal plane as the heart
What do pale MMs indicate?
- intraoperative blood loss
- anemia from any cause
- poor capillary perfusion
What does cyanosis indicate?
Very low blood oxygen concentration
Partial pressure of oxygen in arterial blood
- measured by blood gas analyzers
Blood oxygen saturation
- measured by pulse oximeters
Why does neither Pao2 nor Spo2 give an accurate measure of oxygen availability when a patient is anemic?
This is because even if the Pao2 and/or Spo2 are normal, the carrying capacity of the blood is severely decreased owing to the decrease in the number of hemoglobin binding sites.
Oxygen saturation greater than 95%
During oxygen administration
A pulse oximeter reading of 90% to 95%
Pt is hypoxemic (must be investigated)
Oxygen saturation less than 90%
Need for therapy
Oxygen saturation less than 85% for longer than 30 secs
A medical emergency
How can you reverse atelectasis in its early stages?
By gently inflating the lungs.
In this procedure, called bagging or sighing the Pt, the reservoir bag of the anesthetic machine is carefully squeezed, forcing air into the Pt's breathing passages, until the animal's chest rises as with a normal breath.
Name the three factors determining blood CO2 levels.
1. The rate of production by the cells
2. The rate of transport to the lungs
3. The rate of elimination from the lungs
Name the four distinct aspects which are required to be evaluated in order to effectively interpret a capnogram.
1. The baseline value
2. The ETco2 (end-tidal CO2) value
3. The waveform shape
4. The rate at which changes occur (suddenly, rapidly, or gradually)
Partial Pressure of CO2
It is often 45 to 60 mm Hg during anesthesia because the respiratory depression produced by most anesthetics causes the body to retain CO2. A PaCO2 greater than 60 mm Hg indicates that the Pt is hypoventilating.
Body temperature during anesthesia
Body temp loss during anesthesia is greatest in the first 20 minutes.
Body temp in the range of 32* to 34*C (89.6* to 93.2*F) prolong anesthetic recovery and significantly decrease the dose of anesthetic agents required.
Temps below 32*C (89.6*F) cause dangerous CNS depression and changes in heart function.
In practice, anesthetic monitoring is alarmingly simplified all too often into three stages:
What is the main indicator used to determine when it is safe to remove the ET tube?
The return of the swallowing reflex during recovery
The palpebral reflex
- should be absent during surgical anesthesia in small animals maintained with iso- or sevoflurane
- very slight response in most horses indicates a surgical plane of anesthesia
- slightly stronger reflex in ruminants than in horses, but spontaneous blinking almost always indicates a plane of anesthesia that is too light
The pedal reflex
- present during light anesthesia
- lost during optimum anesthesia
- particularly important in animals undergoing mask inductions, in which the presence of a mask makes assessment of other reflexes or jaw tone somewhat difficult
The corneal reflex
- should be present in light and medium planes of anesthesia
- lost when anesthetic depth is excessive
- unreliable in small animals
- primarily used in large animal Pts to tell if Pt is anesthetized too deeply
- avoid opening the Pt's mouth too wide (because resistance will be felt when the mouth is open to the maximum extent leading to a false interpretation)
Central eye position
Sign of either light or deep anesthesia in small animals and ruminants
Ventromedial eye position
Sign of medium anesthesia in small animals and ruminants
Eye position in horses
- eye can rotate in any direction
- sometimes eyes will rotate in opposite directions
- generally rotation of one or both eyes indicates adequate anesthetic depth for Sx
Nystagmus in horses
- common during certain planes of anesthesia
- fast nystagmus indicates very light anesthesia (gradually slows as depth increases)
- very slow nystagmus ("roving eye") may be present during medium anesthesia