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482 Cards in this Set

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What is meant by a VIC designed anesthesia machine?
Vaporizer incorporated into the breathing system
What is the term for an anesthesia machine with the vaporizor downstream from the flowmeter?
VOC
What type of pressure is found at the gas cylinder of an anesthesia circuit?
High pressure
How do you determine the amount of N2O remaining in a cylinder?
Weigh it
Which O2 tank size (letter) has the largest capacity?
G
In the US, what color are Oxygen cylinders?
Green
In the US, what color are N2O cylinders?
Blue
Whta component of an anesthesia system controls pressure?
A regulator
Why aren't cylinder valves lubricated?
Could combust with O2
What step should be followed prior to attaching an O2 cylinder to a yoke?
Point the valve opening away from you, open very slightly to flush dirt away from outlet port
What system is in place to ensure that gas tanks are not attached to an improper valve?
Color-coding, thread sizing, pin index
What is the function of the O2 pressure gauge?
Indicate the pressure upstream from the regulator
Which component of the anesthesia machine reduces pressure?
The regulator
What is the typical machine pressure?
60 psi
When a machine is carrying 2 gases, what type of valves are used to prevent them from backflow?
Check valves
What is the purpose of the flowmeter?
Measure and indicate gas flow around it
On a flowmeter with a sphere indicator, where is the reading taken?
In the middle of the sphere
Which component of the anesthesia machine allows for a high flow of O2 from the inlet which has not passed thru the vaporizer?
Oxygen flush/bypass valve
A bypass valve is never used when using what type of anesthesia system?
Non-rebreathing
Which device is activated when O2 pressure falls to zero and flow ceases?
Low oxygen warning
What is the purpose of the flowmeter?
Measure and indicate gas flow around it
On a flowmeter with a sphere indicator, where is the reading taken?
In the middle of the sphere
Which component of the anesthesia machine allows for a high flow of O2 from the inlet which has not passed thru the vaporizer?
Oxygen flush/bypass valve
A bypass valve is never used when using what type of anesthesia system?
Non-rebreathing
Which device is activated when O2 pressure falls to zero and flow ceases?
Low oxygen warning
Opening the emergency air intake valve allows the animal to breath what type of air?
Room air
What is the function of the vaporizer?
Vaporize liquid anesthetic resulting in a diluted vapor in a carrier gas
Why is a vaporiser needed?
Undiluted vapors are lethal
Name the 2 types of resistance ventilators are available as...
High and Low resistance
What name is given to a ventilator type in which the air is pushed through the system?
Plenum
Older vaporiser devices use what type of air flow?
Draw over (suck through)
What type of vaporiser design is most commonly used?
Calibrated (precision)
What enviromental factors can affect vaporizer performance?
Temperature extremes, barometric pressue
(thymol-halothane only)
What is the purpose of the scavenging system?
Remove waste anesthetic gases from the vicinity
Name the 2 types of scavenging systems available.
Active and Passive
How does an active scavenging system work?
It sucks!
Why are active scavenging systems the only type used in human anesthesia?
Able to deal with a wide range of flow rates
By what 4 methods can we deliver O2 and anesthetic inhalational agents?
Chamber
Face Mask
ET Tube
Laryngeal mask
What are the 3 benefits of using an ET tube?
Reduce risk of aspiration
Allow admin of O2 & agent without leakage into the room
Reduce contamination of room by waste gases
What type of ET is used in birds and why?
Uncuffed- to prevent damage to tracheal rings (rings are complete, overinflation can damage them)
What feature of an ET tube can help prevent an obstruction of the tube?
A Murphy's eye
During surgery, what factors can affect respiratory variables (rate, tidal volume, minute volume?
Pain, pyrexia, depth of anesthesia
During surgery, O2 consumption is influenced by which metabolic factors?
Age, temperature, thyroid function, drugs, muscle tone, response to surgery
What is the amount of normal tidal volume?
15mlkg
Tidal volume is divided into 2 part: anatomical dead space (ADS) and what?
Respiratory exchange area (REA)
General anesthesia can reduce the tidal volume by how much?
Up to 30% reduction
What does the term apparatus dead space refer to?
Any dead space within the breathing system that may contain exhaled patient gas and which will be rebreathed at the beginning of the subesquent inhalation
What are the 2 most common sources of added dead space?
Overly long ET tubes, Y-piece of a circle system
What is meant by the term "Open Anesthetic Breathing System?
Pt. inhales gases directly from the anesthetic machine and exhales to the atmosphere with no rebreathing
In which type of system is there complete rebreathing of expired gas with CO2 absorbed by chemical means?
Closed or circle systems
What factors drive the selection of a breathing system?
Integral resistance of system
Controlled vs spontaneous ventilation
Economy
Circuit drag
Ease of maint and sterilization
Ease of scavenging
Mechanical dead space
On a non-rebreathing system (Bain and T-piece) how are expired gases removed from the system?
High gas flows
In small animals, what is the minimum O2 provision amount usually quoted?
10mlkg min
What is meant by the term "low flow anesthesia?"
O2 delivered slightly higher than the minimum (metabolic) requirement
If Nitrous Oxide is used in a circle system, would you adjust your O2 flow higher or lower than usual?
Higher
What is the criteria used for selecting the size of the reservoir/rebreathing bag?
Should be 3 times the tidal volume
What is the formula for calculating minute volume?
Tidal volume (10-15 mlkg) x respiratory rate
What is the minimum of O2 flow needed for a precision vaporizer to function accurately?
200 ml/min
What is the pressure of O2 when using the oxygen flush button?
30-50 liters/min
What formula can be used to quickly calculate minute volume?
Body weight / 5
How do you calculate the flow for a non-rebreathing system?
Minute volume x 2
At the start of inhalation anesthesia on a circle system, why do you begin with a flow that is higher than needed?
For rapid uptake of the agent and to flush nitrogen from the body
When collecting the pre-anesthetic history on a pt., what might nocturnal coughing be a sign of?
Cardiac disease
Prior to GA, how long ago should the last meal have been taken?
6 hours
During the clinical exam prior to GA, what might be the cause for an animal to be underweight?
liver disease (portosystemic shunt), malabsorption, renal disease, hyperthyroidism
A pot-bellied appearance my indicate what disease condition in a dog?
Cushing's
An irregular heart rate discovered during the pre-anesthesia exam, should be investigated by what procedure?
ECG
Obtaining a history and completing a physical exam are needed to classify the animal's anesthesia risk according to which system?
ASA
Amercian Society of Anaesthetists
What effect might exogenous corticosteroids have on an animal undegoing anesthesia?
Can depress cortical function, may not be able to produce endogenous steroids in response to the surgery
NSAIDS could have what effect on anesthetic drugs?
Nsaids are usually protein bound and could displace protein bound anesthetics
What drugs could cause nephrotoxicity that could complicate anesthesia?
Antibiotics
What is the difference between a tranquilzer and a sedative
Both quiet the animal, a sedative produces drowsiness
Which type of drug produces sleep from which an animal is NOT readily roused by a painful stimuli?
Narcotic
What type of drug is a combination of a sedative/tranquilizer and a narcotic?
Neurolepanalgesic
What are 3 reasons for using premeds?
-calms pt
-smooth induction & recovery
-reduces amt of drugs needed
-pre-emptive analgesia
-counteract undesirable effects of other drugs
What are some disadvantages to using pre-meds?
-prolongs recovery
-respiratory depression
-requires time if not given IV
-altered cardiovascular function
Pre-meds given by the IV route are given how long prior to induction?
5-10 mins
Orally, pre-meds would be given how long prior to induction?
60 mins for dogs and cats
For old, obese or sick animals are pre-med doses increased or decreased?
Decreased
Ace is in what drug class?
Phenothiazine
Ace provides tranquilization and what other effect?
Anti-emetic
Ace is an A2 receptor agonist and has what effect on vasculature?
Vasodilation
Ace causes vasodilation and hypotension, what effect does this have on the CVS?
Fall in stroke volume and cardiac output, is an anti-arrhythmic
Under which condition should Ace not be used?
-hypovolemia or shock
-impaired liver function
-anemia
-breeding stallions working
Which dogs are very sensitive to Ace?
Boxers and giant breeds
Ace is usually given along with what other type of drug as a pre-med?
Opioid
An A2 agonist has what effect on vasculature?
Vasodilation
What effects do A2 agonist drugs have on the CVS?
-cardiodepressant
-reduce output
-bradycardia
-periph vasoconstriction followed by return to normal or lower values
What effect does an A2 agonist have on the GI tract?
relaxation and decresed motility
In which species is Xylazine used?
Used in most
Which A2 agonist is used in wildlife and exotic species?
Medetomidine
Detomidine is used primarily in which species?
Horses
A2 agonists are usually given in conjunction with what other class of drugs?
Benzodiazepine or opioid
Do pigs require a higher or lower does of an A2 agonist?
Higher
What is the major side effect of using an A2 agonist?
Cardiovascular depression- reduced cardiac output
How does an A2 agonist produce central muscle relaxation?
Via inhibition of spinal interneurons
What drug is the only approved A2 agonist allowed for use in food production animals?
Xylazine
Along with sedation, what other 2 CNS effects does xylazine produce?
Emesis
Bradycardia
What effect does Xylazine have on cardiac output?
Decreased (bradycardia, hypotension)
If xylazine is given to a small ruminant, which route of administration should be used?
IM, to reduce the risk of pulmonary edema
What effects does Xylazine have on the GI tract?
-Inhibition of motility
-reduces ruminal motility
-hypersalivation in ruminants
Under which condition is the use of Xylazine contraindicated?
Contraindicated for cows in last trimester of pregnancy
What is a potential disadvantage to using Xylazine in horses?
Occasional wake up without warning- can be explosive
Is Xylazine reversible?
Yes, with Yohimbine, Atipamezole (Antisedan)
What effect will Xylazine have on 90% of cats and 50% of dogs?
Vomiting within 10 minutes
What caution must be taken when using Xylazine on horses?
Can strike out even when sedated
Which species is very sensitive to Xylazine?
Goats
When is Detomidine used?
Horses and wild animal sedation
Compared to Xylazine, what is the CVS effect of Detomidine?
More bradycardia
Give an example for the use of Romfidine
Radiography of a horse..sedation with less ataxia than xyalzine
Medetomidine has similar effects as other A2 agonists, what effect does it have on body temp?
Marked hypothermia for up to 5 hours
The CVS effects of Medetomidine are profound even at low doses. What drug should Medetomidine be given with to lower the dose?
An opioid
Which A2 agonist is the only one used in human medicine?
Dexmedetomidine
How is the dosage of Dexmedetomidine calculated?
By body surface, not weight
Under what conditions are A2 agonists contraindicated?
-hypotension
-hypovolemia
-myocardial disease
-liver failure
-urinary obstruction
-cows in last trimester of pregnancy
A2 agonist provide a huge drug sparing effect which means what?
Can reduce the amount of subsequent anesthetic doses
What are the 2 A2 antagonists used to reverse A2 agonists?
Atipamezole and yohimbine
Atipamezole acts in what time frame?
4-5 minutes following IM administration
Which drug reverses the effects of Xylazine?
Yohimbine (and atipamezole)
What class of drug are Diazepam and Midazolam in?
Benzodiazepines
When are these drugs used?
In babies, old, sick or debilitated animals. Also used to control seizures
On which receptors do BZ's affect?
GABA
What effect do BZ's have on the CVS?
Minimal CV depression
Do BZ's affect the respiratory system?
Minimally
What primary effect do BZ's have on the CNS?
Increase the seizure threshold
By which route should Diazepam be administered?
IV ..which is painful due to glycol/alcohol solvent..do NOT give IM
What prolongs the action of Diazepam?
Metabolized in the liver into 2 active metabolites
What are the advantages of Midazolam over Diazepam?
-more rapid onset
-shorter acting
-water soluble
-no pain on injection
Which drug is the reversal agent for BZ's?
Flumazenil
Which drug is used as a short acting tranquilizer...primarily for pigs?
Azaperone
Following IM injection of azaperon, what must you do with the animal?
Leave undisturbed for 20 minutes
Butryophenones (droperidol and azaperone) have actions similar to what other drug?
Ace
Name 3 opioids which can be given as pre meds for anesthesia
-meperidine, morphine, methadone, hydromorphone, fentanyl, alfentanyl, buprenorphone, butorphanol
Atropine and Glycopyrrolate are classified as which type of drug?
Anticholinergics (antimuscarinics)
Are Anticholinergics given routinely as part of anesthesia premed in cats and dogs?
No
In which species are anticholinergics given routinely? Why?
Small furry animals...to maintain cardiac output and reduce risk of salivary secretions causing airway obstruction
In which dog breeds do some vets pre-emptively use anticholinergics?
Brachycephalic breeds
What effect do anticholinergics have on the CVS?
Tachycardia (often transitory bradycardia after initial administration)
What are the respiratory effects of anticholinergics?
Inhibits mucus secretions
Bronchodilation
What effect do anticholinergics have on the eyes?
Pupillary dilation
In which species should anticholinergics NOT be used?
Horse and ruminants
What effect do anticholinergics have on salivation in ruminants?
Does not prevent salivation--makes salivary secretions more viscid: risk of ileus and colic
Anticholinergics can be combined with anticholinesterases to reverse what condition?
Neuromuscular blockade
What are the advantages of glycopyrrolate over atropine?
-doesn't cross the blood-brain barrier
-less arrhythmogenic
-more potent, longer acting
-does not produce ocular signs
In which species is Glycopyrroltes the anticholinergic of choice?
Rabbits
Why should anesthetized animals always receive fluids?
-establish venous access
-compensate for CVS effects
-replace insensible fluid loss
-correct fluid loss
In healthy, conscious animals, what is the best route for administering fluids?
Orally- let the body take care of fluid and electrolyte balances
Under which circumstances is IV fluid administration a substitute for oral intake?
-emergencies
-pt unwilling or unable to drink
-fluid loss exceeds the capacity for oral replacement
Name the 3 body compartments in regards to body water
-intracellular (ICF)
-interstitial (ISF)
-intravascular (IVF)
Which body compartment is the biggest in terms of the amount of body water?
ICF
What governs the distribution of the body water?
Osmotic gradients across semi-permeable membranes
Body water makes up how much of adult bodyweight?
60-65%
What is the daily maintenance water requirement for healthy dogs, cats and horses?
2-3 ml/kg/hr
40-65 ml/kg/day
Circulating blood volume consists of what 2 components?
Plasma plus red blood cells
What is the circulating blood volume in a dog?
90 mlkg
What is the circulating blood volume in a cat?
60 mlkg
What separates the ICS from the ECS?
Cell membranes that are freely permeable to water and impermeable to most solutes
Which forces favor reabsorption of fluid?
Higher oncotic pressure
Lower hydrostatic pressure
Which forces favor filtration?
Lower oncotic pressure
Higer hydrostatic pressure
What determines the water content of any given compartment?
Number of solutes in the compartment
Define osmolarity
Number of osmoles of solute (molecules) per liter of solvent
Define osmolality
Number of osmoles of solute per kg of solvent
What is the value of normal plasma osmolarity?
300 mosml
What substance contribute to the osmolality of body solutions?
electrolytes (Na, Cl (ecf), K (icf), lactate ions
glucose
urea
lipids
What is colloid oncotic pressure?
The pressure required to prevent osmosis when the solution is separated from pure solvent by a semi-permeable membrane
Do small or large molecules have a stronger colloid oncotic pull?
Large molecules
What is normal plasma colloid oncotic pressure?
20 mm Hg
What is the major electrolyte found in ICF?
K+
What are the major electrolytes of ECF?
Na+ and Cl-
50% of the body stores are in ECF, how is the balance principally regulated?
By the kidney (aldosterone)
What are some causes of Hypernatremia?
-reduced water intake
-excess water loss
-overinfusion of high Na+ fluids
What are the causes of hyponatremia?
-high volume renal failure
-vomiting/diarrhea
-excessive sweating
-overinfusion of low Na+ fluids
The movement of K+ between ICF and ECF is linked to what?
Acid-base status (H+)
What are the causes of hyperkalemia?
-renal failure
-metabolic acidosis
-severe trauma/burns
-muscle damage
What are the causes of hyponatremia?
-reduced intake
-increased loss- diarrhea
-increased urinary loss- diuretics
Define a crystalloid
Water with an added combination of small molecular weight particles (electrolytes, glucose, lactate, acetate)
Once administered IV, how much of a crystalloid remain in vessels?
Only 1/4 to 1/3 remains after 30 minutes...rapidly redistributes to the intravascular space
What are some examples of crystalloid fluids?
LRS, normal saline, hypertonic saline, detrose, D5W, normosol, plasmalyte
Colloids are larger molecules made up of what?
Complex sugars (starches) or proteins
Some colloids can remain in the vasculature for how long?
Up to 12 hours
In the case of hypoalbuminemia, what is the effect of colloids?
Raises oncotic pressure
What is a primary use for colloid fluids?
Plasma volume expanders to increase cardiac output in hypovolemic patients
Give some example of colloids.
-gelatin
-dextrans
-pentastarch/hetastarch
Give some example of blood products that can be given to deal with fluid balance.
-whole blood
-packed rbc's
-plasma
-human serum albumin
-oxyglobin
Which administration route is the safest for K+ supplementation?
Oral
Which vein is used for high volume fluid replacement?
Jugular
Which fluid administration route is used with old feline outpatients?
Subcutaneous
When giving fluids by subcu, what type of fluid should be used?
Isotonic, with Na+ similar to plasma
Why should dextrose containing fluids NOT be given subcu?
Potentially bacterial growth media
Which fluid administration route should be used cautiously but provides a large area for absorption?
Intraperitoneal
When is the intra-osseous fluid administration route used?
As an alternative to IV in small or collapsed patients
Tonicity of fluids is determined by the content of what?
Glucose and sodium
Fluids are defined as iso, hyper or hypotonic relative to what?
Plasma
During anesthesia, why are polyelectrolyte solutions used?
To restore ECF volume
Why do the isotonic replacement fluids contain buffers?
To benefit animals that have a metabolic acidosis or a normal acid-base status...also designed for pts. with renal disease, shock & trauma, diarrhea, vomiting (except pure gastric vomiting)
Balanced electrolyte solutions rapidly equilibrate across the intravascular and interstitial compartments. How much fluid needs to be given to replace an intravascular deficit?
3-4 times the volume of blood lost
LRS cannot be given with what other fluid product?
Do not give with blood...Ca2+ will activate the clotting system
Why is 0.9% NaCL called an acidifying solution even though it has Na equal to plasma?
Contains no buffers and can lower plasma HCO3
What are some of the potential complications of isotonic crystalloid replacement therapy?
-inadequate fluid administration
-volume overload
-hemodilution
-pulmonary injury
-brain trauma
What is the tonicity of a dextrose solution?
Hypertonic
What is the aim of dextrose fluid therapy?
Generally used for caloric supplementation of parenteral maintenance fluids
Hypertonic saline contains how much NaCl?
7.2%
Hypertonic saline causes water to move from where to where?
From the interstitial space to the intravaascular space...increasing intravascular volume
Why should hypertonic saline be used with caution?
Can cause pulmonary or peripheral edema
What effect does hypertonic saline have on cardiac output?
Increases it
What effect does hypertonic saline have on intracranial pressure?
Reduces it
What is the primary use of hypertonic saline in small animals?
To manage shock, brain injury and to boost blood pressure intra-operatively
What is the primary use of hypertonic saline in horses?
To manage shock and to "prime" the CVS before induction of anesthesia (horses are at risk of hypotension)
What are the potential disadvantage of a hypertonic saline infusion?
Hypernatremia
Hyperchloremia
Hypokalemia
How long is the effect of increased volume when hypertonic saline is given alone?
30 minutes
How can the effect of hypetonic saline be extended?
Give a colloid
What type of fluid must follow the administration of hypertonic saline?
An isotonic fluid....intravascular expansion is transient
If the hypertonic saline is given too rapidly, what effects might be seen?
Hypotension, bradycardia, brochconstriction, rapid shallow breathing
Colloids are used as plasma volume expanders and to treat hypoproteinemia. Under which condition would you NOT use a colloid?
Animals with pre-existing coagulopathies (may interfere with platelets and clotting)
What are the potential complications of colloid therapy?
-volume overload
-increased bleeding time (dilution of clotting proteins)
-care required for animals in heart failure
Oxyglobin is purified Hb from which species?
Bovine
Oxyglobin can improve oxygen transport for how long?
Up to 3 days
What effect does oxyglobin have on cardiac output?
Reduces it
When might the use of oxyglobin be indicated?
For the treatment of auto-IMHA
Using oxyglobin in cats can have increased risk of what?
Pulmonary edema
What are the golden rules of pre and intra-operative fluid therapy?
-Establish what sort of fluid has been lost
-Replace like with like
What effects can intravascular fluid deficits (hypovolemia) have?
-tachycardia
-low blood pressure
-vasoconstriction
-pale mm
-prolonged CRT
-cold extremities
-hyperlactatemia
-decreased urine output
-increased urine SG (azotemia)
What effects can interstitial fluis deficits (dehydration) have?
-poor skin turgor
-sunken globes
-dry mm
-increased PCV and total solids
-increased urine SG, azotemia
What effects can intracellular deficits have?
-dull mentation
-hypernatremia
-hyperosmolarity
Is pure water loss common or uncommon?
Uncommon
Which fluid deficit situation requires immediate correction?
Hypovolemia- loss from the intravascular compartment
Loss from dehydration requires a fluid replacement plan with fluids given over what time period?
6-24 hours
What information is needed to make decisions regarding fluid therapy?
-history
-astute physical assessment
-baseline objective data
On clinical exam, how is hydration status determined?
-skin tugor
-moistness of mm
-eye position
-HR
-peripheral pulse
-CRT
-jugular distension
How is fluid balance best assessed?
By serial bodyweight measurement and lab tests
Name 3 lab tests in which the parameters can be influenced by hydration status
-PCV
-total protein
-USG
-BUN
When examining lab results for hydration status, inflammatory disease will raise which portion of the proteins?
Globulin
In the case of hypovolemia, which protein value will be raised?
Albumin
In a case of dehydration, an elevated BUn will be accompanied by what type of change in USG?
Increased
What condition does an elevated BUN and a low USG indicate?
Renal disease
Fluid loss during anesthesia/surgery can be from what?
-pure water loss
-loss of mixed water and electrolytes
-hemorrhage
During anesthesia, how is pure water mainly lost?
Evaporation from exposed membranes
What are the causes of electrolyte loss during the peri-anesthetic period?
-vomiting
-diarrhea
-sweating (horses)
Why can hemorrhage lead to cardiovascular collapse?
Fluid lost is plasma
No change in the relative concentration of electrolytes & water, so no incentive for water to move from ISF to ICF to replace what is lost from circulation
What type of fluid should any healthy animal undergoing anesthesia receive?
Isotonic, crystalloid fluid
What is the infusion rate for the isotonic fluid therapy during GA on a healthy animal?
5-10mlkg h (5 times maintenance)
This rate will not compensate for what type of fluid loss?
Dehydration or blood loss
For short procedures with GA, which solutions are suitable?
-LRS
-Plasmalyte or Normosol
What is the rule of thumb for volume of fluid to compensate for blood loss?
3 times the volume of a crystalloid for minor hemorrhage
if hemorrhage or blood loss continues, what should then be infused?
Colloids
How is blood loss during surgery monitored?
-suction bottle contents
-gauze swabs
-lap sponges
-surgical drapes
-surgeon's gowns
-floor, table surface under drapes
How do we replace blood loss during surgery when the amount is
<10% blood volume?
With crystalloids
How do we replace blood loss during surgery when the amount is
<20% blood volume?
With colloids and crystalloids
How do we replace blood loss during surgery when the amount is
>20% blood volume?
With blood plus cystalloids
What is the aim of rapid fluid therapy?
Maintain PCV >20%, and TP >35gdl
During GA, what is the infusion what for crystalloid fluids?
5-10 mlkg h (higher when doing surgery)
What is the infusion rate of crystalloid fluids for treatment of shock?
60-90 mlkg h
At what rate should hypertonic saline be given?
4-5 mlkg single dose administered slowly
What is the rate for colloid fluid infusion?
2-20 mlkg h for intra-operative hypotension, peri-op hypoproteinemia, mild hemorrhage
(not to excedd 40mlkg h due to coagulopathies)
What effects can crystalloid or colloid fluids have on hypotension during surgery?
-restore circulating volume,
-raise blood pressure
-maintain organ perfusion
Continued high rate of crystalloids cannot be continued indefinitely due to the risk of what?
Dilution of plasma proteins (esp albumin), reduce plasma colloid oncotic pressure, increasing loss of water from vasculature leading to edema
Post-anesthesia maintenance fluids contain what type of levels of Na, CL and K?
Na low
Cl low
K high
What is the tonicity of maintenance fluids?
Hypotonic or isotonic
In some critically ill patients, addtional K is needed and is given in the form of what?
KCl
What is the most important monitoring device?
Human senses
According to the minimum monitoring standards of the ASA, what factors must be continually monitored during anesthesia?
-CNS, depth of anesthesia
-Oxygenation
-Ventilation
-Circulation
-Temperature
What parameters are monitored during induction?
-respiration
-heart rate
-mm color
-palpebral reflexes
-muscle activity
-swallowing and coughing
-eye position
What parameters and body systems are monitored while the animal is unconscious?
-CVS
-respiratory system
-eye signs
-muscle activity
-body temp
-swallowing
-equipment
What additional monitoring takes place during recovery?
Adequacy of pain control
Rotation of the eye occurs during which levels of anesthesia?
Light and medium
With dogs and cats the surgical plane of anesthesia is when the eye is in which position?
Ventromedial
Is the pupillary light reflex active during anesthesia?
Yes, but obtunded
Does mydriasis or miosis occur during GA?
Could be either depending on the technique
Why is a sterile opthalmic solution needed during GA?
Lacrimation slows dramatically
What happens to the palpebral reflex during GA?
It is lost with increasing depth of anesthesia
What eye signs are seen with Ketamine?
A brisk palpebral reflex and central eye position
Why is the corneal reflex rarely used?
Cornea is easily damaged
Why is it important that the swallowing reflex return before the ET tube is removed?
If the animal vomits they will swallow instead of aspirating
When is checking the pedal reflex helpful?
Gauging when intubation should be attempted
Which reflex can be tested on a cat for depth of anesthesia, but is not reliable?
Ear flick
Which muscles should be checked to assess depth of anesthesia?
Muscles of mastication, tone of jaw (ease of opening mouth), flex and extend the elbow, carpus..neck muscles in horses, swans, small ruminants)
When might you see muscle rigidity in anesthetized animals?
When Ketamine mixtures are used.
By which methods do we monitor the CVS during anesthesia?
-CRT and mm color
-palpation of peripheral pulse
-esophageal stethoscope
-ecg
-arterial blood pressure
-central venous pressure
What is CRT and mm color an idication of?
Peripheral perfusion...not ABP
What do cyanotic blue mm indicate?
<5g oxygenated Hb per 100 ml blood
Sepsis or dehydration can be seen by what color of mm?
Brick red
What do ashen grey mm indicate?
Circulatory failure
What is the normal value for CRT?
< 2 seconds
When palpating a peripheral pulse during anesthesia, what should you consider?
Tone and amplitude, rhythm and synchronicity with the heart/ECG
What information about blood pressure can be gained by palpating the peripheral pulse?
None, reflects stroke volume not blood pressure
The femoral pulse is palpable at what pressure?
80 mm Hg
What can be identified and measured via an esophageal stethoscope?
Respiratory rate and heart rate
What information is gained by using an ECG?
Electrical activity of the heart- arrhythmias and the myocardial environment...no information on the mechanical function or cardiac output
How might the ECG be misleading?
Will be normal with hypovolemia
May be normal during cardiopulmonary arrest
What is the definition of blood pressure?
BP = cardiac output x total peripheral resistance
During anesthesia, the goal for blood pressure is to maintain MAP at what level? SAP?
MAP > 60 mm Hg
SAP > 80 mm Hg
What damage can result from hypotension?
Reduced perfusion of vital organs (kidney, brain, liver)
Urine output is an indirect indicator of cardiac output and blood pressure, at what pressure must the kidneys be perfused to produce urine?
MAP > 60mm Hg
What is the purpose of monitoring Centrsl Venous Pressure?
Assess right-sided heart function and adequacy of circulating blood volume
What is normal CVP?
2-5 cm H2O
What does an elevated CVP indicate?
Right ventricle is unable to deal with volume of blood returning to it
What are the likely causes of elevated CVP?
-decreased cardiac function
-fluid overload
Low CVP (<1cm H2O) can be an indication of what condition?
Low circulating blood volume
Bradycardia and hypothermia are indications of anesthesia that is too light or too deep?
Too deep
Tachycardia can be an indication of what conditions during GA?
Light anesthesia
Pain
Arrhythmias during GA can be caused by what?
-myocardial disease
-light anes. causing pain/symp stimulation
-excessively deep anes
-hypoxemia
-respiratory acidosis
-metabolic acidosis
-electrolyte abnormalities
-hypothermia
How is respiratory monitoring accomplished during GA?
-rate
-depth/tidal volume
-pattern
-evaluation of giving a "sigh"
-oxyhemaglobin saturation (pulse ox)
-end tidal CO2 (capnograph)
-blood gas analysis
Name 3 methods that can used to detect the respiratory rate
-count chest or reservoir bag excursions
-listen w/ esophogeal stethoscope
-use Apalert
What are some causes of a slow respiratory rate or apnea?
-intubation
-excess anes depth
-resp depressant drugs (opiods, barbs, iso)
-hypocapnia
-muscle relaxants
-increased intracranial pressure
What are some of the causes of rapid respiration during GA?
-light anes
-drug related (opioids can cause panting)
-hypercarbia
-hyperthermia
Shallow respiration will likely have what effect on tidal volume?
Reduced
Describe a normal GA respiratory pattern.
Chest wall out on inspiration, abd wall quietly in on expiration
Ketamine can induce what type of breathing patter?
Apneustic
By what technique can the anesthetist check the respiratory system if the animal and check the anesthesia machine for leaks?
By giving a "sigh"...squeezing the reservoir bag with the pop-off valve closed
Why is it important to maintain homeothermy during anesthesia?
Essential for cardiac function, metabolism, normal enzyme activity and homeostasis during sugery
When is the greatest amount of heat lost, and why?
Within the first 20 mins of GA due to redistribution of heat from the core to the periphery.
Which animal will have the largest heat loss...a small or large dog?
Small dog....surface area:body weight ratio
What effect does hypothermia have on cardiac function?
Myocardial irritation and bradycardia, reduction in cardiac output and blood pressure
What effect does hypothermia have on MAC?
Reduction in MAC, more easily overdosed
How should core temp be monitored during GA?
By esophageal probe or tympanic membrane probe...rectal is for peripheral temp not core
What are some methods that can be used during surgery to maintain core body temp?
-avoid cold solutions
-minimize surgery time
-ambient temp as warm as is comfortable for staff
-warm anesth. gases
-bair huggers (forced warm air)
-thernal blankets
-warm IV fluids
Minimum CVS monitoring during GA includes what?
-heart rate
-rhythm
-pulse
-mm color
-CRT
What additional CVS monitoring is needed for high risk patients?
-ECG
-blood pressure
+/- CVP
What respiratory monitoring is needed during GA?
-rate
-depth
-oxygenation
What does pulse oximetry measure?
Oxyhemoglobin saturation of arterial (pulsating) blood
Oxyhemoglobin absorbs light more strongly at which wavelength?
940 nm
What are the best locations for placing a pulse ox probe?
Tongue, vulva, toe webbing, prepuce, ear
An "excellent" pulse ox reading would be what?
97-100 saturation
Pulse ox monitors oxyHb saturation, but does not measure what?
PaO2
What does a capnograph measure?
CO2 tension in both inspired and expired gases
End tidal CO2 is a good indication of CO2 where?
Alveolar...in turn a good indication of arterial CO2 tension
What key components should you examine on a capnogram?
-height of plateau and see if it returns to zero
-shape and regularity of peaks and troughs
Describe a normal capnogram.
-smooth upstroke
-horizontal smooth plateau
-a teep down stroke
-baseline with zero CO2 tension
On a capnogram, what does a slanted upstroke indicate?
Slow exahlation- respiratory obstruction, tube obstruction, obstructive airway disease
On a capnogram, what does an increasecd or decreased plateau height mean?
Hyperventilation or hypoventilation or low cardiac output
On a capnogram, what does a slanted downstroke indicate?
Slow inspiration- insufficiently inflated ET tube cuff, malfunction of inspiratory vavle on rebreathing system, bronchoconstriction
What does a base above zero indicate on a capnogram?
Rebreathing Co2- exhausted soda lime or insufficient fresh gas flow
What can be the cause of a sudden loss of tracing of a capnogram?
ET tube disconnection, cardiac arrest
Name thr 2 types of capnographs that are available.
Maintream
Side stream
What is the advantage of a mainstream designed capnograph?
Very fast response
What is a disadvantage of a sidestream designed capnograph?
Lag time in display
Give 3 condition that decrease end-tidal CO2 volume.
-hyperventilation
-low cardiac output
-low CO2 production (hypothermia)
-pulmonary embolism (incr. alveolar dead space)
-sampling error (leak)
Give 3 conditions that can increase end tidal CO2 levels.
-hypoventilation
-rebreathing
-sepsis
-hyperthermia
-skeletal muscle activity
-malignant hyperthermia
In addtion to blood pressure measurement, what other measurement will help evaluate cardiac output?
Arterial blood pressure
Mean arterial blood pressure (MAP) should be maintained at what level?
> 70mm Hg
Systolic arterial pressure (SAP) should be maintained at what level?
> 90 mm Hg
Blood flow it major organs is autoregulated. This function could be compromised if blood pressure falls below what range?
60 -120 mm Hg
During anesthesia, blood pressure that falls below 80/40 mean what?
Possible organ dysfunction..intervention needed
What should normal Systolic and Diastolic pressure be?
Systolic 90-120 mm Hg
Diastolic 55-70 mm Hg
Mean 60-100 mm Hg
Hypotension is defined as MAP at what level?
MAP < 70 mm Hg
(systolic < 90 mm Hg)
Hypertertension is defined as MAP at what level?
MAP > 100 mm Hg
(systolic > 150 mm Hg)
If a femoral pulse and a metatarsal both can both be palpated, blood pressure can be assumed to be a what level?
> 80 mm Hg
What if just the femoral pulse is present but not the metatarsal?
Systolic pressure is 80 mm Hg = hypotension
For the kidneys to produce urine, they must be adequately perfused. MAP must be what for this to occur?
> 60 mm Hg
What is the "gold standard" method for monitoring arterial blood pressure?
By placing a catheter in a peripheral artery ( dorsal metatarsal in a dog, femoral artery in a cat)
What is DINAMAP?
Device for Indirect Non-invasive Automated Mean Arterial Pressure
By what other method can arterial blood pressure be monitored?
Doppler ultrasound
Does Doppler measure systolic or diastolic pressure?
Systolic
What is meant be Central Venous Pressure (CVP)?
Measure of the hydrostatic pressure in the right atrium
How is CVP determined?
By the function of the right heart and pressure in the venous blood of the vena cava
True or False. CVP measures cardiac function and blood volume.
False...does not measure either directly...must be interpreted
CVP measurement can provide ealy evidence of what conditions?
-volume overload
-recurrent pericardial effusion
-right side heart failure
Low CVP is indicative of what condition?
Low CO = hypovolemia
High CVP is indicative of what?
low CO = heart failure
CVP monitoring is considered mandatory under what circumstance?
In patients where concern exists regarding fluid therapy
What is the normal range for CVP?
0 - 5 cm H2O
Values > 12-15 cm H2O are suggestive of what condition?
Volume overload

< 0 = hypovolemia
Is CVP lowest or highest during expiration?
Highest
How can CVP be estimated?
By looking at jugular filling pressure- with volume overload jugular may look distended, pulsations may be visible
What is the difference between pain and nociception?
Pain is a conscious experience
Nociception describes the process of neurotransmission
Acute and persistent pan can have what overall effects on the patient?
-metabolic effects (can affect wound healing)
-cardiovascular effects (hypertension, tachycardia)
-poor recovery from anesthesia, greater risk of post-op complication
-chronic pain with increased risk to auto mutilation, wound biting
Define the nociceptive C fibers.
Slow and unmyelinated
Define the nociceptive A alpha fibers.
Small diameter myelinated fibers
The nociceptive fibers conduct a noxious stimulus to where in the spinal cord?
Dorsal horn
Define Hyperalgesia
An exaggerated response to a noxious stimulus
What is allodynia?
A pain response to a non-noxious stimulus (such as a gentle touch)
How do peripheral nociceptors ( C and A) become sensitized?
Induced by inflammatory mediators released by tissue damage
By what 3 ways can we assess pain?
-physiological signs
-behavioral signs
-response to analgesia
What are some of the physiological signs of pain?
-altered heart rate
-altered respiratory rate
-hypertension
-increased temp
-changes in biochemical factors (cortisol, adrenaline, noradren, acute phase proteins)
In the dog and cat, what are some behavioural indications of pain?
-postures (hunching, praying)
-locomotion (stiff, non-weight bearing)
-vocalization
-facial expression
-attention to the affected area
-hyperalgesia, allodynia
What is the response of a horse to any stimulus which frightens or hurts it?
Attempt to escape
What is a sign of persistant pain in a horse?
Withdrawal, weight shifting, restlessness, subtle changes in head and ear posture
How do ruminants respond to pain?
Withdraw, grind teeth, weight shifting, restlessness, depression
What is the best tool available to assess acute pain in animals?
Short form of the Glasgow Pain Assessment System
What are the 4 main categories of analgesia?
-pre-emptive
-multimodal
-regional/local
-analgesic infusions
What is the theory behind pre-emptive analgesia?
Central sensitization is more susceptible to analgesic agents before rather than after a noxious stimulus
In dogs and cats, why must you be cautious is using NSAIDs as pre-emptive analgesics?
Risk of renal impairment
Which analgesics can be given intra-operatively via CRI?
-opioids
-ketamine
-lidocaine
Which analgesic groups are usually given post op?
Opioids plus NSAID's
Sedation drugs should always be given in combination with what other type of drug?
An analgesic
What level of analgesia is provided by anesthetic agents?
None
By which routes can analgesic drugs be administered?
Local
Intrathoracic
Intraperitoneal
Intra-synovial
Systemic- bolus or infusion
Extradural
Oral
What is the theory of multimodal analgesia?
Use a combination of various agents by various routes in smaller doses to produce an overall greater effect than using a single large dose of one agent
What is the method of action of NSAID’s?
Prevent the formation of eicosanoids from arachidonic acid by blocking the cyclo-oxygenase enzyme
In vet med, which NSAID is selective for COX-2?
Firecoxib
What is the most common side effect of oral NSAID therapy?
GI ulceration
What is the potential effect of NSAID therapy on the kidneys?
Nephrotoxicity-impairs PGE2 production
What effect can NSAIDs have on platelets?
Can interfere with platelet aggregation- predisposing to bleeding disorders
Are NSAIDs high or low plasma protein bound?
Highly protein bound
What are the contraindications for the use of NSAIDs?
-concurrent corticosteroid medication
-hypotension or hypovolemia
-gastric ulceration or vomiting
-renal dysfunction
-coagulopathy
What change in the dosing of NSAIDs must you make when treating a cat?
Carefully dosed at longer intervals (deficient in glucoronidation enzymes)
What class of drugs are the most effective analgesic agents?
Opioids
Name the 3 types of opioid receptors?
Mu, delta, kappa (3,1,2)
What effect do opioids have on the CVS?
Benign effects
What effect does giving opioids have on other anesthetic drugs?
Anesthetic-sparing
Are opioids reversible?
Yes
What side effect can opioids have on respiration?
Respiratory depression
What side effect might be seen if an opioid is used as a pre-med in a non-painful animal?
Nausea/vomiting
What effect do opioids have on the GIT?
Reduced motility
What is the difference between a partial and a full opioid agonist?
Full agonist is dose dependent and the effect can be enhanced by incremental dosing
Partial agonist cannot induce a maximal effect
Which opioids are best suited for severe pain control?
Morphine, methadone, fentanyl
Is Butorphanol a good analgesic?
No…is a good sedative and anti-tussive
What is the duration of action of Morphine in dogs? Cats?
Dog: 3-4 hours
Cat: 6-8 hours
What might occur if Morphine is given too quickly IV?
Histamine release, anaphylaxis
What is the typical dose for Morphine in a dog?
0.3-0.5 mg/kg
Methadone is a full mu-selective agonist. What is its duration of action?
4-6 hours
Fentanyl is a very potent analgesic. What effects can be induce by using fentanyl?
Bradycardia, respiratory depression
What drug is an opioid antagonist?
Naloxone
Burpenorphine is what type of opioid?
Partial agonist
Burpenorphine is used under what conditions?
Visceral or soft tissue pain, esp in cats
Aside from IM or IV dosing, what other route can Buprenorphine be given?
Orally, well absorbed by the mucosa
How should the skin surface be prepared for the placement of a Fentanyl patch?
Clipped, wiped clean…no soap or alcohol
What are the disadvantages to using a Fentynal patch?
-analgesic response is highly variable
-lag time until effective plasma concentration is reached
-potent drug- open to accidental or deliberate use
Opioids produce what effect on cats’ eyes?
Mydriasis
Ketamine is an antagonist of which receptor type?
NMDA
When should Ketamine be used as an analgesic?
In patient’s whose pain has not been controlled by standard analgesic regimes based on opiods and NSAIDs (spinal surgery, amputation)
Which A2 agonist has been recognized as possessing analgesic properties?
Medetomidine
Tramadol has morphine-like effect on which receptors?
All opioid receptors, esp Op3
How does Tramadol produce an analgesic effect?
Inhibition of serotonin and noradrenaline re-uptake
What are the most common side effects to using Tramadol?
Mild nausea and vomiting
As an analgesic, Gabapentin is used in what cases?
Neuropathic pain
What drug has NMDA antagonist effects and can be used to lower the dose of opioids needed?
Amantidine
What role do sedative drugs play in analgesia?
Anxiolytic
What drugs are contained in MLK?
Morphine, Lidocaine, Ketamine
When using MLK with isoflurane, how much should the MAC be reduced?
By 45%
Why isn’t MLK given to cats?
Due to the Lidocaine
What other drug can be used instead of Mophine to make MLK?
Fentanyl (FLK)
What is TIVA?
Total intravenous anesthesia..when IV is used for induction and maintenance of anesthesia
In an IV solution, 1% is hoe many grams in 100 ml?
1 gram
How much is Ketamine 100 mgmgl?
10%
5% Thiopental is how many mgml?
50 mgml
Thiopental 25 mgml is what percent?
2.5%
Which class of drug is the oldest injectable anesthetic?
Barbituates
Which barbituate is on of the few available today in vet med?
Thiopental
In solution, thiopental is highly alkaline, what effect does this have on tissues?
Highky irritant if extravasated
What is the mechanism of action of barbituates?
Depresses the RAS in the brainstem responsible for wakefulness, interacts with GABA
Which is the active portion of a barituate...the protein bound or unbound?
The unbound is active
Thiopental is up to 40% unionized in plasma, making it lipid soluable. In this form, what can the drug do?
Cross the blood brain barrier
What biochemical condition will increase the intensity of the barbituate effect?
Acidosis
Is recovery from a drug due to metabolism or redistribution?
Redistribution
In which breeds should Thiopental be avoided?
Sight hounds (low body fat = lack of depot for the drug)
How quickly does Thiopental take effect?
One arm-brain time...unconsciousness in 30 seconds
What effect does Thiopental have on intracranial pressure?
Lowers it
What level of analgesia does Thiopental produce?
None
What are the CVS effects of Thiopental?
Cardiovascular depression, vasodilation, drop in output. arrhythmogenic
What respiratory effect is usually seen post induction?
Apnea
What caution must be taken with preparing Propofol?
Contains no preservative, can grow bacterial
What is the mechanism of action of Propofol?
Enhances GABA activity, enhances NMDA activity
What effect does Propofol have on intraocular pressure?
Reduces it
What are Propofol shakes?
Some animals can develop muscle rigidity and spasm following induction. responds to Ketamine
Does Propofol raise the seizure threshold?
No, used as an anti-convulsant in dogs with refractory epilepsy
What are the CVS effects of Propofol?
CVS depression, vasodilation, decreased aterial blood pressure, stroke volume and cardiac output
Little effect on heart rate
What are the respiratory effects with Propofol?
Respiratory depression
How can the pain of injecting Propofol be reduced?
Draw blood back into the syringe prior to injection, use a low dose of lidocaine
Do pigs require higher or lower doses of Propofol?
Higher
What caution should be taken when using Propofol in cats?
Prolonged recovery if used as CRI
Which neuroreactive anesthetic agent is not yet licensed in the US?
Alfaxalone
What is the mechanism of action of Alfaxalone?
Enhances inhibitory effects of GABA, acts on central glycine and nicotinic Ach receptors
Alfaxalone has CVS effecst similar to what agent?
Propofol
In which species is Alfaxan not used?
Dogs, histamine release
Name the 2 common dissociative drugs used in vet med
Ketamine, Tiletamine
Ketamine is usually co-administered with what other class of drugs?
Rarely given alone, usually given with BZ, ACP, A2 agonist
What is the mechanism of action of Ketamine?
Unclear. Believed to be a result from inhibition of excitatory neurotransmitters
What is the name of the Ketamine metabolite formed in the liver?
Nor-ketamine
What is a disadvantage of Ketamine in terms of recovery?
Usually an unpleasant recovery
What are the CNS affects of Ketamine?
-increased cerebral blood flow
-increased cerebral O2 consumption
-increased intracranial pressure
-epileptogenic
-good analgesic
-increases muscle tone
What ocular effects are seen with Ketamine?
-eyelids remain open (use eye gel)
-increases intra-ocular pressure
-dilated, centrally fixed pupils
What effect does Ketamine have on the CVS?
Stimulates the CVS, indirect sympathomimetic action
What are the respiratory effects of Ketamine?
Minimal respiratory depression
Pharyngeal/laryngeal reflexes maintained
Apneustic breathing
Hypersalivation
What are some conditions that contra-indicate the use of Ketamine?
-increased ICP
-hepatic, renal disease w/ obstruction
-risk of seizure
-increased intra-ocular pressure
How does Tiletamine compare to Ketamine?
Similar in action, but more potent and a longer duration of action
What are the common uses for Tiletamine?
-aggressive dogs, feral cats
-horses, pigs, exotics
Whjat is the advantage of using Etomidate?
Has minimal CVS depressant effects, minimal effects on the sympathetic nervous system and barorecptors
What is the effect of Etomidate on the adrenals?
Temporary adrenal suppression
What is TIVA?
Using drugs in combination as a continuous IV infusion to maintain anesthesia when an inhalational agent is not desirable or possible
What are the properties of the ideal drugs for TIVA?
-non cumulative
-rapidly metabolized
-non irritant
-no undersirable properties from long administration
What is an example TIVA technique used in equine medicine?
Triple drip...Guaphenesin, ketamine and xylazine