Terms in this set (208)
Anesthesia is defined as:
the loss of feeling or sensation
general anesthesia vs local anesthesia
general = the whole body
local = a specific part
General anesthesia is characterized by:
unconsciousness and insensibility to feeling and pain which is induced by the administration of anesthetic agents
General anesthesia allows us to
perform procedures that would be painful to the animal
the process of bringing a patient from a state of consciousness to general anesthesia usually by means of injectable anesthetic drugs
the process used to keep patients under general anesthesia until the procedure is over
the loss of sensation to a localized body part or region without the loss of consciousness
-obtained by administering drugs to a specific area (lidocaine and buprivacaine for dentals is common)
state without pain
refers to drugs administered to the patient before general anesthesia is induced
state of calm or drowsiness
a state of relaxation and reduction of anxiety
a state of profound sedation and analgesia produced by giving simultaneous administration of an opioid and tranquilizer
Objectives of analgesia
-produce a loss of sensation
-provide muscle relaxation
the process of using several different drugs that have complimentary effects
ex. giving acepromazine as a premed, inducing with ketamine and valium (50/50 mix), maintaining with sevoflurane (gas) and administering morphine for analgesia
6 steps of anesthesia
1. Patient evaluation and preparation
2. Equipment and supplies
3. Preanesthetic medication
Because swallowing reflexes are sluggish and esophageal sphincter tone decreases, it is recommended for most patients to be fasted for about _____ hours before surgery.
What are the LVTs responsibilities when they are checking in surgical patients during the morning?
Find out if the patient has been fasted, if there has been any change in their behavior or mentation, if the patient is on any medications not already documented in their chart, and verify the reason they are here (i.e., neuter, cruciate injury, etc.)
A _____ should be performed by a DVM before any drugs are administered to the patient.
During the pre-surgical PE, the LVT is responsible for obtaining and recording what?
CRT, MM color, TPR, mentation, weight and drawing blood/running pre-anesthetic tests (BUN, CREA, ALKPHOS ALT)
The info collected via the PE and laboratory results will allow the DVM to formulate the patient's ARA, what does this stand for?
Anesthetic Risk Assessment
What does the Anesthetic Risk Assessment determine?
what types of drugs are used and which are omitted
Where are ET tubes placed and what are they used for?
Placed inside of the trachea of an unconscious patient, attached to a breathing tube, and connected to the anesthetic machine.
-This allows us to deliver oxygen and anesthetic gas to the patient which maintains them at a surgical plane of anesthesia.
3 benefits of ET tubes
-allows an open airway
-prevents aspiration of stomach contents and water
-allows for manual ventilation if needed
What is the internal diameter (ID) used for?
to measure the tubes; the size of the tube can be found on the side of the tube (make sure to read ID not ED-external diameter)
ET tubes should be checked for _____ and _____ before using.
leaks and cleanliness
A- valve with syringe
B- pilot balloon
C- patient end
H- inflated cuff
I- patient end
J- Murphy eye
Identify the parts of the ET tube (A,B,C,D,E,H,I,J)
What are laryngoscopes used for?
to allow better visualization of the pharynx and larynx when placing ET tubes
2 parts of a laryngoscope
blade (with light) and handle
2 species that laryngoscopes are not used in
cattle and horses
cone shaped device that allows you to deliver oxygen and/or anesthetic gases to the patient without intubating them
The _____ size mask to comfortably fit the patient should be used.
Masks maintain an open airway, prevent aspiration, and allow you to manually ventilate the patient, T or F?
What do induction chambers allow you to do?
provide the patient with O2 and/or anesthetic gas
-very helpful in anesthetizing aggressive small animals such as cats and some dogs
-require high flow rate of gas and O2
Why must you remove the patient quickly, close the lid, and move the induction chamber outside to vent?
it pollutes the environment
Anesthetic machines are used for?
to deliver O2 and anesthetic gas to a patient which allows us to maintain them at a surgical plane of anesthesia
12 basic parts to an anesthetic machine
1. oxygen source (either attached to the machine or piped in)
3. pressure regulator
4. flow meter
5. soda lime granules
6. scavenger unit (passive or active)
8. breathing tubes
9. pop off valve
10. unidirectional valves
11. O2 flush valve
12. rebreathing bag
What color are oxygen tanks?
When should Oxygen tanks be changed?
when they contain 100-200 psi
What color are Nitrous Oxide tanks?
__ tanks are smaller.
-connect to anesthetic machine
-contains 700 L of oxygen
-contains 1,600 L of nitrous oxide
__ tanks are taller.
-contain 7000 L of oxygen
-contain 16,000 L of nitrous oxide
What do pressure regulators do?
reduce the pressure to a level that will not damage the anesthetic machine, usually 50 psi.
What does the flow meter do?
controls the amount of gas (oxygen) flowing through the vaporizer or to the patient; read by middle of steel ball
Unit of measure of flow meter/oxygen
L/min or mL/min
gas-specific components of anesthetic machine
flow meter & vaporizer
Why should you never over-tighten the flow meter?
you can damage it
Flow of O2 through system
1. compressed gas (very high pressure) >>
2. pressure regulator (takes pressure down to 50 psi >>
3. flow meter (precision control of gas to be delivered to vaporizer or patient)
used "out of the circle" when patient has no influence over amount of gas used; deliver an adjustable concentration of gas
used "in the circle" when patient has influence over amount of gas used; dependent on oxygen flow rate, depth & frequency of patient respirations & environmental temp.
Ideal stage/plane of anesthesia
stage 3, plane 2
colors of vaporizer with matching gas
purple = isoflurane
yellow = sevoflurane
red = halothane (not common anymore)
waste anesthetic gases
function of scavenger
removes WAGs from environment
active scavenging system
uses a mechanical fan to remove waste gas from the machine & places it in the outside environment
passive scavenging system (F/air canister)
removes waste anesthetic gas from the machine, cleans it using activated charcoal, & puts it into the room
function of soda lime granules
remove carbon dioxide from the breathing circuit;
change color from white (new) to blue (old) once a certain amount of CO2 has been removed
function of manometer
measures the pressure within the machine & patient's lungs
unit of measurement of pressure w/in manometer & patient's lungs
normal pressure within anesthetic machine
20 cm/H20 (should never exceed)
function of pop-off valve
acts as a vent to allow excess pressures to leave the breathing circuit
(needs to be closed when manually breathing/bagging a patient or when checking machine for leaks)
****always make sure to REOPEN the pop-off valve if you close it- matter of life or death!
function of unidirectional valves
used with rebreathing circuits & only allow the gas to move in one direction
function of O2 flush (fast flush valve)
allows you to introduce pure O2 (no anesthetic gas) into the breathing circuit & is usually found near the flow meter
-this may be required in emergencies when you want to quickly "wake up" the patient & bring them to a lighter plane of anesthesia
Can an O2 flush be used on a non-rebreathing circuit?
function of rebreathing bags
holds extra gas that allows the patient to recycle gas that was previously exhaled & cleaned of CO2 with the soda lime
benefits of rebreathing bags
-good way to monitor respiration rate as it deflates with inspiration and inflates with expiration
-allows us to manually breathe (bag) for the patient
-this is done by closing off the pop-off valve & gently squeezing the bag
When breathing for the patient with a rebreathing bag, make sure the manometer does not go over ___ cm/H2O & observe patient's chest.
When is manually breathing for the patient done?
during CPR or during long procedures to prevent pulmonary atelectasis (we have to breathe for the patient every 5-10 minutes)
a complete or partial collapse of a lung or lobe of a lung (respiratory complication after surgery)
When choosing a rebreathing bag, should you round up to the next biggest size or round down?
always round up
How do you calculate the rebreathing bag needed?
use a bag equivalent to 6 x the patient's tidal volume
tidal volume =
Ex. a dog that weighs 20 kg (44 lbs) would need a 1,200 ml bag
6 (20kg x 10 ml) = 1,200 = 1.5 L (bag size)
function of breathing circuits
move O2 and anesthetic gases from the machine to the patient
2 main types of breathing circuits
rebreathing and non-rebreathing
rebreathing circuits vs non-rebreathing circuits
rebreathing- require the patient to move the gas through the tubes while inhaling and exhaling (allows rebreathing of gas, more economical)
non-rebreathing- rely on higher pressures to move the gas and do not require the patient to move it (safer for smaller patients but more costly)
the most common type of rebreathing circuit
Y-piece rebreather (new design is the Universal F-circuit)
The Universal F-circuit
allows incoming air to be warmed by the air the patient has exhaled
(also provides less congestion by the patient's head which is especially helpful while performing dentals)
Non-rebreathing circuits are generally used on what sized animals?
small animals weighing under 2.5-3 kg (5.5-6.6 lbs)
How does the Bain's non-rebreather work?
The incoming air is warmed by the exhaust hose which surrounds it, similar to a F-circuit. Only has 1 spot to connect it to the machine unlike the F-circuit which has 2 (has a tube inside another tube).
Ayres non-rebreathing circuit
not truly a Bain
Before the surgical day begins, what should you do to the anesthetic machine and why?
leak check it- this will ensure that the machine is working properly and that you will not be exposed to unneeded WAGs
9 leak checking steps
1. Turn on O2 if not already done
2. Attach breathing circuit
3. Completely close pop-off valve
4. Occlude patient end of
rebreathing tube with your thumb or palm of your hand
5. Turn on flow meter to 2 L/min and watch the manometer until it reaches 20 cm/H2O
6. Turn the flow meter down to 200 ml/min
7. Watch the manometer. If the system is leak free the manometer should stay at 20 cm/H2O while at 200 ml/min for at least 20 sec.
8. If the needle does not stay at 20 cm/H2O then you have a leak. Check the machine and recheck if a problem is found. Common places for leaks include the breathing circuit, rebreathing bag, soda lime granules (especially if it has just been replaced).
*If you cannot detect a leak you can spray the machine with soapy water and repeat the steps. The leak should cause bubbles to form at the source. (don't spray machine if you don't have to)
9. When completed, make sure you turn off the flow meter and triple check that you have OPENED the pop-off valve.
How long before the patient is induced to unconsciousness are premeds given to the patient?
Functions of premeds
-calm the patient
-aid in restraint
-reduce pain & discomfort
-minimize vagal reflexes (vagus nerve has inhibitory effects on heart & lungs)
-smooth anesthetic induction & recovery
-minimize doses of anesthetics required for induction & maintenance
4 types of premeds
Tranquilizers & Sedatives
a state of analgesia & reduced awareness produced by simultaneous administration of neuroleptic agent & narcotic agent
ex. droperidol-fentanyl, acepromazine-etorphine
used to reduce or eliminate some of the undesirable effects of anesthesia (reduce secretions, maintain adequate c.o.)
2 examples of anticholinergics used
Why is Glycopyrolate used more commonly in equine anesthesia than Atropine?
Atropine decreases GI motility which can induce colic in horses
Cardiac output =
stroke volume x HR
Benefits of Tranquilizers & Sedatives
-aids in restraint
-decreases amount of general anesthetic needed
-aids in smoother recovery
3 examples of tranquilizers & sedatives
Alpha-2-agonists (Xylazine, Medatomidine)
What is the effect of acepromazine on the seizure threshold?
it lowers it
What is the effect of valium on the seizure threshold?
What is a useful characteristic of alpha-2-agonists?
they are reversible;
xylazine - yohimbine (Yobine)
medatomidine - atipamezole (Antisedan)
very potent analgesics, often used in preanesthesia & post-op pain
-potent respiratory depressants
4 examples of opoids
What is fentanyl reversed by?
What happens 5-10 minutes after inducing morphine to a patient as a premed?
the patient will vomit (this is normal for this drug)
Neuroleptanalgesics are combinations of
tranquilizers and opioids that can provide sufficient analgesia & amnesia for minor surgical procedures (small wound closure, skin biopsies, ear flushes, etc.)
Innovar-Vet = Fentanyl & Droperidol
Acepromazine + Oxymorphine
Fentanyl & Droperidol
What has to happen between premeds & induction?
-all of the supplies for intubation need to be gathered
-some clinics place IV catheters before the induction agent, some do it after (depends on the individual clinic and patient to some extent)
-induction drug needs to be put out & possibly calculated & drawn up if not already done
The goal is to have the patient anesthetized for as _____ as possible.
Induction agents are given to
bring a patient from consciousness to unconsciousness
used to induce & maintain general anesthesia
Barbituates are generally classified as
(short/ultra-short acting are most common)
What are long & intermediate acting barbituates used for?
What are short & ultra-short acting barbituates used for?
to induce anesthesia
rapid onset anesthesia to allow for intubation for maintenance or for short acting procedures (not used often anymore)
Dangerous side effects of thiopental:
-vasodilation & decrease in BP
-dramatically reduces HR if overdosed
Always use ketamine with a _____.
With _____ drugs, eyes remain open, therefore, you should always use artificial tears ointment so corneas will not dry out.
Benefit of propofol
Disadvantages of propofol
expensive, can cause transient apnea (will stop breathing shortly)
_____ is the only white substance used IV.
Maintaining unconsciousness is mainly done by using what kind of drugs?
steps in induction process
1. intubate patient
2. connect patient to anesthetic machine
3. set both the flow meter & vaporizer settings
4. prep patient for surgery
prepping patient for surgery include:
shaving surgical site, admin eye lube, possible admin abx, express bladder, trim nails (outside of surgery suite preferably)
Small/large animal gas flow rates on rebreathing CLOSED system:
small animal (5-10 ml/kg/min)
large animal (2-3 ml/kg/min)
Small animal induction gas flow rate for rebreathing open/semi-closed system:
Small animal maintenance gas flow rate for rebreathing open/semi-closed system:
Large animal gas flow rate for rebreathing open/semi-closed system:
Non-rebreathing gas flow rate
Closed system refers to
operating the machine with the pop-off valve closed, patient is given minimum amount of O2
-economical because of lower flow rates but very dangerous, rarely used in small animal anesthesia
open or semi-open system refers to
the pop-off valve being partially or completely open
-more costly, but safer as flow rates are higher & pressure build-up is uncommon because extra gas can exit via the pop-off valve
Inhalant anesthetics are supplied in the form of _____.
liquid; the liquid is poured into a vaporizer & turns to gas once in contact with oxygen flowing by a vaporizer
5 inhalant anesthetics
MAC (Minimum alveolar concentration)
the lowest alveolar concentration required to prevent gross purposeful movement to a graded noxious stimulus (such as skin incision or tail clamp) in 50% patients
indicates the potency of an anesthetic
The lower the MAC value, the _____ potent the anesthetic.
_____-_____ MAC usually maintains surgical plane of anesthesia.
describes how an anesthetic gas is distributed between: blood & gas, tissue & blood
-expressed as a partition coefficient
Is solubility the same as potency?
The greater the blood-gas parturition, the _____ the uptake of anesthetic by blood.
Why do drugs like methoxyflurane with a coefficient of 13, have long induction & recovery periods?
because large amounts of anesthetic must be taken into the blood before the tension or partial pressure of the anesthetic rises sufficiently to produce anesthesia
The lower the blood-gas partition coefficient, the _____ soluble the drug in the blood.
Inhalant anesthetic that some veterinarians still use for very painful procedures
Inhalant anesthetic that used to be very popular but has been replaced with "Iso"
Inhalant anesthetic that is very popular, allows a quick recovery
Inhalant anesthetic that is very expensive, has a very rapid onset, good for induction of small rodents and reptiles
Between Methoxyflurane, Halothane, Isoflurane, and Sevoflurane, which is the shortest acting?
Sevoflurane (lowest #)
Between Methoxyflurane, Halothane, Isoflurane, and Sevoflurane, which takes the longest to induce anesthesia?
Methoxyflurane (biggest #)
Between Methoxyflurane, Halothane, Isoflurane, and Sevoflurane, which is the most potent?
Methoxyflurane (biggest %)
Between Methoxyflurane, Halothane, Isoflurane, and Sevoflurane, which is the least potent?
Sevoflurane (smallest %)
Goal during maintenance
keep the patient at a surgical plane of anesthesia & ensure adequate tissue perfusion
-close & constant monitoring of the patient & adjusting the vaporizer setting, flow meter, & possibly both to keep vital parameters in the normal area
3 stages of anesthetic planes:
Stage 1 = amnesia
Stage 2 = excitement or delirium (trying to fight off anesthesia)
Stage 3 = anesthesia
5 anesthetic planes:
Plane 1 = light anesthesia
Plane 2 = surgical anesthesia
Plane 3 = deep anesthesia
Plane 4 = overdosage
Plane 5 = terminal (death)
We want to keep our patients in stage ___, plane ___ which is surgical anesthesia.
stage 3, plane 2
How long does the "excitatory phase" last?
about 15-30 seconds; the patient may begin to thrash around and begin moving his/her legs in a running fashion, this is a normal response (involuntary)
Monitoring is especially critical during the _____ phase of anesthesia.
Can you set the dial and walk away?
NO, never rely on machines only; the patient's depth of anesthesia will need to be adjusted as the surgery takes place
when the eyelids are touched, the eyelids close;
generally a strong palpebral reflex indicates a light plane of anesthesia, at a medium or deep level of anesthesia, palpebral reflexes are sluggish and completely disappear
When is the corneal reflex used?
usually only used when checking euthanized patients
Pupillary light response
shining light into the eye- not used often
firmly pinch skin between toes;
if animal pulls back (even slightly) they are too light. You should get no response from the pinch which needs to be very firm.
2 stethoscopes to auscultate with
esophageal stethoscope or regular stethoscope
Report to DVM if dog's HR drops below ___ or above ___ in a large dog.
below 60 or above 140
Report to DVM if dog's HR drops below ___ or ___ in a small dog.
below 70 or above 160
In cats, report to DVM if HR drops below ___ or ___.
below 100 or above 200
Palpation of arteries in a dog
femoral, dorsal metatarsal, digital, lingual
Palpation of arteries in cats and swine
Palpation of arteries in horses
facial, transverse facial, lateral metatarsal
Palpation of arteries in ruminants
auricular, digital, coccygeal and dorsal metatarsal
Ideal MM color
Report to DVM if respiration rate goes below ___ or above ___ in dogs/cats.
below 8 or above 20
In a surgical plane of anesthesia, the eyes should be rolled _____. If eyes are looking right at you, the animal is too deep or too light (more sensitive in dogs than cats).
When monitoring anesthesia, how should the jaw tone be?
moderate, use 2 fingers to try and separate the mandible from maxilla.
One of the most commonly used machines is the pulse _____.
What do pulse oximeters do?
evaluate the level of oxygen saturation in the blood by evaluating the amount of hemoglobin saturation (most machines record HR as well)
Normally when breathing pure oxygen, hemoglobin in the lungs is at least _____%.
On the pulse oximeter, the lowest acceptable reading is
>95% with 100% being ideal
On the pulse oximeter, a reading between 90-95% indicates
On the pulse oximeter, a reading below 90% indicates
On the pulse oximeter, readings below 85% for more than 30 sec =
Most probes for the pulse oximeter are clips that can be placed on the:
tongue (most common), lip, ear (2nd most common choice), prepuce, vulva, digital web, & sometimes the feet of small patients and rectal use
If using a standard probe for a pulse oximeter, the red light should be _____ the tongue for the best results.
A capnograph can be used to measure what?
CO2 content of inspired/expired air
Normal expired air displayed on a capnograph is _____-_____mm/Hg
How is an electrocardiogram hooked up?
white = right front
black = left front
red = left rear
green = right rear
"Green & white is always right, xmas tree in back"
Why is it important to monitor temp. every 15-30 minutes while a patient is under anesthesia?
hypothermia is common
2 ways BP can be monitored
indirect & direct
direct measurements of BP
most accurate, but require arterial catheter to be placed, therefore it is rarely used except in specialty type hospitals.
indirect measurements of BP can be taken with what 2 tools?
sphygmomanometer & Doppler monitor
What does the Doppler monitor require?
a small spot must be shaved usually on palmar or plantar surface, conducting gel applied to the spot, & a probe placed over the gel
The probe of the Doppler monitor will transmit the sound of _____ blood to an amplifier for you to hear.
The sphygmomanometer cuff will be placed above the probe of the Doppler monitor & the width of the cuff should be ___ - ___ % the circumference of the patient's leg.
How is the sphygmomanometer used?
It is inflated until the sound disappears, then slowly let out the pressure in the cuff & when you hear the noise again, record the reading on the sphygmomanometer
*this is a systolic reading
Automated Oscillometric Unit
Another option for measuring BP; cuff selection is based on the width of the cuff being 30-50% the circumference of the leg
-can be placed around the foreleg, metatarsals, metacarpals, or tail base
-no shaving required
In a perfect world, what would you do after the surgical procedure is over?
turn off the vaporizer while the DVM is finishing suturing the surgical site & let the patient breathe pure O2 for 5 minutes
-this will help the gas leave the lungs & the patient will "wake up" more smoothly & quicker
Another approach after surgery is over:
Disconnect patient from breathing circuit, occlude breathing circuit & hit the O2 flush. This will remove the extra anesthetic gas out of the pop-off valve and into the scavenger. Reconnect the patient & allow them to breathe.
Some clinics have special recovery areas where one person stays with the patients until they can hold themselves in a _____ position.
Does the recovery phase mean the patient is no longer in danger?
no; many patients that die under anesthesia do so during the recovery phase.
The tech will gently clean around the surgical site of dried blood with _____.
H2O2 (hydrogen peroxide)
Why shouldn't you go over the actual incision site with hydrogen peroxide?
it will delay the healing process if it gets into the wound
After the patient is in the recovery area, deflate the ET tube & untie it. DO NOT pull the tube until the patient has done what?
What should you do if a patient begins to regurgitate during an anesthetic procedure?
1. Notify DVM if present
2. Immediately move patient so that their head is off the table & pointing at the ground. This will allow gravity to work in our favor. It may be necessary to lavage the oral cavity once the regurgitation has ceased.
What is hypovolemia & how is it corrected?
a decrease in the volume of circulating blood; blood transfusion or IV fluid therapy done by a DVM
What is hypothermia & how is it corrected?
Decreased body temp; Warm the patient, ideally with a warm water re-circulating blanket.
-Can use heating pads with extreme caution, should always be kept on low with a towel in between the patient & the pad.
-Can also use rice bags & warm water bags placed in the inguinal region with extreme caution to prevent damage to the skin.
What is hypoventilation & how is it corrected?
decrease in ventilation; breathe for the patient, administering doxapram (Dopram) with DVM permission or turning down vaporizer & allowing patient to breathe oxygen.
What is hypotension & how is it corrected?
decrease in BP; increase IV fluid rate w/ DVM permission, or turning down vaporizer.
What is hypoxemia & how is it corrected?
decrease in amount of oxygen in peripheral blood; breathing fresh oxygen for the patient, or turning down/ off the vaporizer
What do you do if the patient begins to wake up on the surgery table?
1. Check to make sure ET tube is placed correctly
2. Check the anesthetic machine. Check for any liquid anesthetic in the vaporizer, check if the % is too low
3. Check the flow meter to make sure oxygen is flowing
4. Make sure machine is hooked up properly
5. Worse case scenario- give injectable meds to buy time
What should you do if the patient goes into cardiac arrest?
1. Alert DVM
2. Check ABCs (airway, breathing, circulation)
3. Locate emergency drug box
4. Begin CPR if needed, if ET tube is placed- breathe for patient & have someone perform chest compressions
5. If DVM requests, get epinephrine from the refrigerator & admin. as directed
ARA scale: 1- Minimal risk =
normal, healthy patient undergoing elective procedure (i.e., spay/neuter)
ARA scale: 2- Low risk =
patient with mild systemic disease
neonatal, geriatric, or obese patients
patients with mild dehydration
procedures such as lump removal
ARA scale: 3- Moderate risk =
patient with severe systemic disease such as anemia
compensated major organ disease
ARA scale: 4- High risk =
patient with severe systemic disease that is a constant threat to life (i.e., ruptured bladder, internal hemorrhage, pneumothorax, pyometra)
ARA scale: 5- Extreme risk =
patient is moribund & is not expected to live without operation (i.e., severe head trauma, pulmonary embolus, GDV, end-stage organ failure)
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