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Flashcards in Anaesthesia Deck (120)
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Nelissen P, Corletto F, Aprea F, White RAS. Effect of Three Anesthetic Induction Protocols on Laryngeal Motion during Laryngoscopy in Normal Cats. Vet Surg. 2012 Oct;41(7):876–83.

- from intro: in dogs, thiopental is best, but propofol good too
- this study: no difference between alfaxolone, propofol, ket + midazolam
- 6 cats had no movement even though they were normal cats
- (all were premedicated with methadone, Doxapram was not used)


Baetge CL, Matthews NS. Anesthesia and analgesia for geriatric veterinary patients. Vet. Clin. North Am. Small Anim. Pract. 2012 Jul;42(4):643–53–v.

- 30 % of geriatric patients have undiagnosed subclinical disease


Kelly CK, Hodgson DS, McMurphy RM. Effect of anesthetic breathing circuit type on thermal loss in cats during inhalation anesthesia for ovariohysterectomy. J Am Vet Med Assoc. 2012 Jun 1;240(11):1296–9.

- Bain circuit vs a novel mini-rebreathing circuit on temperature in cats
- no difference in temperature (probably would have been a difference in humidity)
- duration of procedure more influential on thermal loss than type of circuit


Zacuto AC, Marks SL, Osborn J, Douthitt KL, Hollingshead KL, Hayashi K, et al. The influence of esomeprazole and cisapride on gastroesophageal reflux during anesthesia in dogs. J Vet Intern Med. 2012 May;26(3):518–25.

- placebo vs esomeprazole vs esomeprazole + cisapride
- results: esomeprazole + cisapride DID reduce # of reflux events and raised pH
- protocol: esomeprazole 1mg/kg IV & cisapride 1mg/kg IV
- 12-18 hrs preop and again 1-1.5 hrs preop
- esomeprazole alone didn’t reduce # of events but it raised pH to non-acid levels


Conner BJ, Hanel RM, Hansen BD, Motsinger-Reif AA, Asakawa M, Swanson CR. Effects of acepromazine maleate on platelet function assessed by use of adenosine diphosphate activated- and arachidonic acid- activated modified thromboelastography in healthy dogs. Am J Vet Res. 2012 May;73(5):595–601.

- intro: previous reports suggest that acepromazine may alter platelet function
- no altered platelet function in dogs getting 0.1 mg/kg or 0.05 mg/kg IV


McSweeney PM, Martin DD, Ramsey DS, McKusick BC. Clinical efficacy and safety of dexmedetomidine used as a preanesthetic prior to general anesthesia in cats. J Am Vet Med Assoc. 2012 Feb 15;240(4):404–12.

- dexmedetomidine was a great preanesthetic for cats compared to no preanesthetic
- 40 mcg/kg IM!
- improved intubation, decreased amount of propofol for induction, decreased amount of iso needed for maintenance, better pain scores after procedure
- decreased heart rate, pale mucous membranes, emesis occurred more often


Escobar A, Pypendop BH, Siao KT, Stanley SD, Ilkiw JE. Pharmacokinetics of dexmedetomidine administered intravenously in isoflurane-anesthetized cats. Am J Vet Res. 2012 Feb;73(2):285–9.

10 mcg/kg given IV over 5 minutes had a T1/2 of 3.3 hours


Franklin MA, Rochat MC, Payton ME, Broaddus KD, Bartels KE. Comparison of three intraoperative patient warming systems. J Am Anim Hosp Assoc. 2012 Jan;48(1):18–24.

- once in the OR, Bair Hugger vs Bair Hugger + water blanket vs warming panels

- once in the OR, all 3 groups maintained temp equally
- the warming panels were as effective as Bair huggers at maintaining temp
- none were able to regain the lost heat from surgical prep


In general, drugs that are more lipid soluble take longer/less time to achieve a steady state concentration with CRI’s or multiple dosing



From the perspective of general anesthetic action, the organs and tissues of the body may be divided into three groups, categorized by how quickly drugs distribute to them after an IV injection. What are the three groups?

vessel-rich group (brain, heart, kidneys)
muscle group
vessel-poor group (fat)


Most vaporizers used in small animal anesthesia today are:
in-circuit / out-of-circuit
variable-bypass / measured flow
flow-over / bubble-through / injection- type
temperature compensated / not temperature compensated
not agent specific / agent specific

out of circuit, variable-bypass, flow-over, temperature compensated, agent specific


If an incorrect agent is used in an agent-specific vaporizer (e.g. you put isoflurane in a sevoflurane vaporizer), what might happen?

the vaporizer might have an unpredictable output


What makes a desflurane vaporizer unique?

- it is warmed to allow the desflurane to become a gas
- it is an injection-type vaporizer
- it needs to be plugged into a power source
- it has a special refilling mechanism to ensure a tight seal btwn bottle and vaporizer


What does the capnograph of a patient re-breathing CO2 look like?

It does not drop back to 0


In a rebreathing system, what will happen if the inspiratory valve becomes stuck open? What will happen if the expiratory valve becomes stuck open?

-Inspiratory valve open: the patient will rebreathe exhaled gas with CO2
-Expiratory valve open: the patient will rebreathe exhaled gas with CO2


When using a rebreathing circuit, do we usually use the system as a “closed” circuit or a semi-closed circuit?



What is the weight cut-off for using a rebreathing vs a non-rebreathing system?



Equation for Minute volume (MV)



What is the recommended fresh gas flow rate for a nonrebreathing system?

At least 3 times the patient’s respiratory minute volume


Ko JC, Austin BR, Barletta M, Weil AB, Krimins RA, Payton ME. Evaluation of dexmedetomidine and ketamine in combination with various opioids as injectable anesthetic combinations for castration in cats. J Am Vet Med Assoc. 2011 Dec 1;239(11):1453–62.

- playing with different kitty magic cocktails
- all cats got dexmedetomidine (25 ucg/kg) + ketamine (3 mg/kg) with either:
- buprenorphine, butorphanol, or hydro
- results: DKBut and DKH were good cocktails to do a neuter. DKBup not quite enough sedation by 10 min


Fresh gas flows around ________ ml/kg are required to prevent rebreathing in most nonrebreathing systems.

200 – 500 ml/kg


In a rebreathing system, the concentration of inhalant the patient inspires will be less than that dialed on the vaporizer. In a nonrebeathing system, the concentration of inhalant the patient inspires will be the same as that dialed on the vaporizer T/F?



Name the color code and cylinder type that is found in for each of the following gasses color-coded (North American color coding):
Nitrous oxide, carbon dioxide, nitrogen, oxygen, medical air

Blue and E: Nitrous oxide
Gray and E: Carbon dioxide
Black and H: Nitrogen
Green and E or H: Oxygen
Yellow and E: Medical air


If a tank of oxygen has half of the pressure than it did when it was full, then what percentage of oxygen volume is left in the tank?



When reading the flow rate on a flowmeter with a bobbin, you should read the top/middle/bottom of the bobbin. When reading the flow rate on a flowmeter with a ball, you should read the top/middle/bottom of the ball.

bobbin: top
ball: middle


Why shouldn’t the oxygen flush valve be used while an anesthetized patient is on a nonrebreathing system? Why shouldn’t the oxygen flush valve be used while an anesthetized patient is on a rebreathing system?

-nonrebreathing: barotrauma from the high flow rate
-rebreathing: the oxygen will dilute the gas anesthetic and alter the plane of anesthesia


How does MAC relate to the body (According to Tobias - the basis for MAC values)

End-tidal concentration (concentration in alveoli at end of expiration) of inhalant is considered to be equal to the concentration of inhalant in the brain at equilibrium


Name two ways to scavenge inhalant anesthetics

active and passive scavenging


What gas cannot be scavenged with the passive charcoal-container scavenging?



Name three types of anesthesia ventilators

time-cycled, volume-cycled, and pressure-cycled


When using a volume-cycled ventilator, what should you initially set the volume to? And what does this equate too?

10 – 15 ml/kg it equates to the tidal volume of the patient


When using a pressure-cycled ventilator, what pressure should you set for cats and for dogs?

cats: 12 mmHg
dogs: 15 mmHg


Which has a more profound effect on blood oxygen content, hemoglobin concentration or PaO2

hemoglobin concentration


What is the typical eye position during a light plane of anesthesia? During a medium plane of anesthesia? During a very deep plane of anesthesia?

light: central
medium: ventromedial
deep: central again


What is the equation for mean arterial pressure (using SAP and DAP)?

MAP = DAP + [{SAP-DAP}/3]


When taking Doppler blood pressure measurements, what will happen if the cuff is too loose – not snugly secured?

You’ll get an artificially high value


In cats, the Doppler tends to underestimate the systolic arterial blood pressure by up to ______ mmHg.



In cats, oscillometric devices tend to underestimate ___________ but are relatively precise for ______________.

underestimate SAP
relatively precise for MAP and DAP


Which indirect blood pressure measuring method, Doppler or oscillometric, will tend to fail in the presence of irregular heart rhythms, tachyarrhythmias or bradyarrhythmias?



Hypercarbia results in:

respiratory acidosis, vasodilation, and increased intracranial pressure


Is end-tital CO2 measurement most accurate in a nonrebreathing system or in a rebreathing system (assuming the capnograph is between the endotracheal tube and the rest of the anesthetic tubing)?

It is more accurate in a rebreathing system. In a nonrebreathing system, the sample of gas is diluted with incoming fresh gas.


Describe the capnograph associated with hypoventilation

returns to base line (0), end tidal CO2 levels progressively increase and duration of exhale shortens. The elephants get taller toward their heads and narrower


Describe the capnograph associated with rebreathing CO2

does not return to 0 so base line elevates


Describe the capnograph associated with a leak in the system

Loss of flat plateau, looks more like a mtn peak, phase 1 sharp increase in CO2 ass with exhale but then no plateau a more gradual drop in CO2 instead (leaking out)


Describe the capnograph associated with hyperventilation

decline in CO2


What two forms of hemoglobin do pulse oximeters detect? What other forms of hemoglobin can exist and affect the pulse oximeter readings?

oxyhemoglobin and deoxyhemoglobin
methemoglobin and carboxyhemoglobin


What PaO2 corresponds with an SaO2 of 90%?
What PaO2 corresponds with an SaO2 of 95%?

SaO2 of 90 % = PaO2 of 60 mmHg
SaO2 of 95 % = PaO2 of 80 mmHg


An SaO2 of 98 % corresponds to a PaO2 of about 100 mmHg – why is that a worrisome thing in a patient under anesthesia?

Because they are breathing 100 % oxygen so they should have a PaO2 of 500 mmHg


Does anemia affect SpO2 reading?

Not until it is very very severe (e.g.


Pharmacologic reversal of neuromuscular blockade should not be attempted until

all 4 twitches can be seen in the “train-of-four” analysis with a nerve stimulator


What is normal CVP (in mmHg and in cm H2O)?

0 – 8 cm H2O
0 – 5 mm Hg


The CVP’s response to a fluid bolus is more diagnostic than the baseline CVP, in determining a patient’s fluid status. What would you expect after a 5-10 ml/kg crystalloid fluid bolus in a hypovolemic patient? In a hypervolemic patient?

hypovolemic: CVP increases slightly, then quickly back to baseline
hypervolemic: CVP rises 4-5 cm H2O, very slow return to baseline if at all (may take 30-60 mins)


Number the following inhalant anesthetics from lowes to highest MAC:
____ halothane
____ desflurane
____ sevoflurane
____ isoflurane

____ halothane 1
____ desflurane 4
____ sevoflurane 3
____ isoflurane 2


On which ion channels do local anesthetics act?

fast sodium channels


About how long does lidocaine take to have onset? About how long does it last? Bupivacaine?

Lidocaine: onset within 5 minutes; lasts 45-60 minutes
Bupivacaine: onset up to 45 minutes; lasts up to 6-8 hours


Why isn’t bupivacaine given IV like lidocaine?

cardiotoxicity: cardiac arrest, cardiac arrhythmias, decreased contractility


Name a depolarizing neuromuscular blocking agent. Now name a nondepolarizing one

depolarizing: succinylcholine
nondepolarizing: atracurium, cis-atracurium


How is atracurium (and cis-atracurium) metabolized/eliminated?

degradation by Hoffman elimination


What are the reversal agents for nondepolarizing neuromuscular blockade?

neostigmine and edrophonium


What should you have with you or give prophylactically when giving one of these reversal agents from question 94, in case the reversal agent leads to a cholinergic crisis?



A blood pressure cuff that is wider than 40-60% of the circumference of the limb (to big) will result in an artificially __________ value.

low. Too big a cuff underestimates BP


A cuff that is too small will result in an artificially low or high value



1. What is “delta down” and what does it tell you about a patient?

It is attenuation of the arterial blood pressure waveform with a positive-pressure breath caused by collapse of the great vessels in the thorax and it is seen in patients with low intravascular volume.


MOA of dobutamine and dopamine and
Affect on the heart

B-adrenergic agonists
Increase heart rate


MOA of atropine

Acetlycholine competitive antagonist for the muscarinic receptors particularly


How do opioids cause constipation?

Mu receptors in myenteric plexus of GI tract. Initially stimulates dogs to defecate (less so in cats) then constipation and ileus from GI spasms and activation


Name and localize the 3 muscarinic receptors
And what two common drugs we use to antagonize them

M1 - CNS and autonomic ganglian
M2 - SA and AV nodes
M3 - Secretory glands, vascular endothelium, smooth mm

Atropine and Glycopyrolate


What is a murphy eye and whats it for

Hole near the end of an endotracheal tube so that air can continue to pass if the end of the tube becomes clogged


Described the rule of 6 technique for making a cri

body weight in Kg x 6 = mg to be added to 100ml of diluent (if over 10ml total drug to be added then subtract amount added to diluent from the diluent e.g. 100-10 so 10ml of drug and 90 mil of diluent). This will result in a rate of 1ml/hr to obtain 1mcg/kg/min. 5ml/hr will equal 5mcg/kg/min


How many micrograms are in a milligram

1000 mcg in 1 miligram


When using the rule of 6 technique, what if you want to use a 50ml syringe

your using 50ml of diluent not 100 which is 100/2 so divide 6 by 2 as well.
bdy wt in kg x 3 added to 50ml of diluent run at 1ml/hr will result in 1mcg/kg/min


What is soda lime and how does it work

A combination of water, sodium, calcium and potassium hydorxides. CO2 reacts w water forming carbonic acid on the surface of the absorbent granules. It then dissociates to free protons and carbonate. These then associate w strong bases to form water and calcium carbonate.
Indicator dye changes color on reaction with acid


Opioid receptors

mu, kappa and delta
all are g protein coupled receptors


Mu receptors

most of the clinically relevant analgesia and side effects occur from activation of this receptor


Analgesic effects of opioids in the periphery

Presynaptic - affects cAMP and thus decreased levels of Ca within cell = decreased release of neurotransmitters like substance P and glutamate
Post synaptic efflux of K = hyper polarization


Analgesic effects of opioids centrally

Block release of inhibitory transmitter GABBA on presynaptic descending nerve fibers. Blocking this inhibition (i.e. disinhibition) allows increased descending pathway activity decreases the amount ascending pathway activity (pain transmission toward the brain)


According to Tobias administration of opioids can reduce the inhalant anesthetic requirement by



GI side effect from opioids and why

Receptors in the myenteric plexus. activation leads to an increase in segmental contractions and a decrease in propulsive contractions


Ocular side effects of opioids

Mydriasis in cats due to increased catecholamines
Miosis in dogs


Respiratory side effects of opioids

Dose dept
mu-2 receptor mediated hypoventillation and decreased responsiveness to high CO2


Whats a PICC line? Can you use it for CVP measurment

Peripherally inserted central catheter.
Can use but normal ranges have not been established in dogs but most likely would be similar to jug cath in evaluating dynamic fluid challenge


Non-invasive cardiac output monitoring

Thermodilution, lithium dilution CO, pulse contour analysis (PulseCO), noninvasive CO (NiCO)



Current method to which all others compared too
Thermister in plulmonary artery measures change of temp of room air temp or chilled saline injected just proximal to thermister. CO called from area under the temperature curve


Lithium dilution CO (LidCO)

Similar to thermodilution but uses lithium chloride change in concentration instead of saline change in temperature


Noninvasive CO (NiCO)

Least invasive technique.
Uses modified fick principle (O2 consumption and arterial-venous [oxygen} to calculate CO). Its true because uptake of a substance is equal to the product of the blood flow to the tissue and the a-v concentration gradient.
Device forces patient to rebreath CO2. Then measures actual amount of CO2 being produced and eliminated by the patient to determine cardiac output.
Shown to be accurate in dogs (most reliably if >20kg)


With respect to strength/potency what are opioids compared too?



What is the potency of the following opioids Hydromorphone, oxymorphone, meperidine, methadone, fentanyl, buprenorphine

FOHMM (like foam) from highest to lowest strength. Throw b
Meperidine 10x LESS than morphine
Methadone 2x more potent then morphine
Hydromorphone 8x more potent
Oxymorphone 10x more potent
Buprenorphine 40x more potent at the mu receptor but does not fully activate the receptor (i.e. a partial mu agonist) so analgesia is less than a full agonist
Fentanyl 100x more potent


Why might Methadone be associated with fewer excitatory responses in cats

Along with mu receptor activity it has NMDA receptor antagonist activity


Fentanyl patches in cats vs dogs

Reliable [therapeutic] in cats when placed on lateral thoracic wall (may take 12-16 hours) and last up to 5 days.
[Plasma] in dogs varies widely,



Fentanyl analogue unique in that it is metabolized by plasma esterase's which = an extremely short 1/2 life so RAPID recovery.
Does not require hepatic or renal metabolism


Why might butrophanol warrant further investigation for visceral pain?

Its a kappa receptor agonist (and mu receptor antagonist)


Tramadol analgesic properties associated with?

serotonin and adrenergic receptors within the CNS


What drugs may not be a good combo with Tramadol and why? And what other analgesic drug has similar concerns

MAOIs and serotonin antagonist/reuptake inhibitors (trazadone). May lead to serotonin syndrome (has not been reported in Vet Med)


Serotonin syndrome

Excessive serotonin in the CNS
Can see - hyperthermia, anxiety; in severe cases shock, rhabdomyolysis and subsequent renal failure.



Tranquilizer that enhances effect of GABA.
Also an anticonvulsant
Wide therapeutic index (overdose nearly impossible)
No sig cardiovascular or respiratory depression
No analgesia
Diazepam and Midazolam are examples



gamma aminobutyric acid and inhibitory neurotransmitter
Activated receptor allows Cl into nerve cell depolarizing it
Distribution of receptor within the CNS accounts for species differences in response to benzo's



Reversal for Benzo's



Benzodiazepine. IV, IM and almost immediately absorbed nasal or rectally
Metabolites (nordiazepam, oxazepam) can have sedative activity and slower clearance (so not good for liver dz or others with bad metabolism)
Lasts about 2 hours
Absorbs to plastic and is light senstive



benzo of choice for hepatic dysfunction or other causes of delayed metabolism
Can go IV or IM without irritation and lasts ~1hr
Its major metabolite 1-hydroxymethyl midazolam has minimal biologic activity



Acepromazine - Depresses dopamine (sedating) and is an alpha-1 receptor antagonist (vasodilation and protect against arrhythmia)


Alpha-2 agonists

Ratio of selectivity of alpha-2 to alpha-1 receptors dictates the degree of sedation and adverse effects. Alpha-2 agonists reliably produce profound sedation (decreased norepi release in CNS) and analgesia and muscle relaxation
Alhpa-1 in periph responsible for some of the side effect like
vasconstriction, hypertension, arrythmogenicity
Medetomidine and Dexmedetomidine (and Xylazine)


Ficks eq for determining cardiac output (C0) using O2 uptake

CO = O2 uptake/([arterial O2])-([Venous 02)


Leon N. Warne, DVM; Thierry Beths, DMV, PhD; Merete Holm, DVM; Evaluation of the perioperative analgesic efficacy of buprenorphine, compared with butorphanol, in cats JAVMA, Vol 245, No. 2, July 15, 2014

Compared IM Buprenorphine 0.02mg/kg vs Butorphanol 0.4mg with medetomidine as premed (medetomidine reversed) for pain control 2 phases – 1st with premed only, 2nd with addition of repeat dose at closure
Phase one stopped early because 9 of first 10 needed rescue analgesia (neither drug worked well).
Phase 2 Buprenorphine better; none required rescue whreas all torb cats did



alpha-2:alpha-1 = 1600:1 (Xylazine 160:1)
Dogs = persistent hypertension and reflex bradycardia
Cats = hypertension is minimal but heart rate, stroke volume and cardiac output all drop
Increasing the dose prolongs duration, does not change the degree of effect



dextrorotary isomer of medetomidine (theoretically may have fewer side effects)
May results in lesser degree of sedation and may have a shorter duration of action
Equipotent dose is 1/2 that of medetomidine


What makes propofol a good choice for patients with hepatic disease

Has extra hepatic sites of metabolism and is rapidly redistributed


Propofol MOA

Agonist at GABA receptors increasing inhibition throughout the CNS.
Unrelated to barbiturates


Propofol CNS, Resp and Cardio effects

Dose dependant depression of all.
Cadiac via drop in CO and sys vasc resistance


What makes Propofol a good choice for head trauma

decreased CBF and CMRO2 (cereb metal of O2) and their ratio is unchanged or slightly increased


Good for and why?
Not good for and why?

Good for bad hearts. Minimal CV depression
Bad for critically ill (rel. ad. insuffiency)Induced adrenal suppression that can last up to 6 hours.
If used give post op physiologic dose or corticosteroid


Why is the anesthesia required to prevent movement during surgery 1.2-1.5 times MAC

Because MAC is defined as the minimum alveolar... to prevent movement in response to a std stimulus in 50% of normal patients and the stimulus is not as strong as surgery


MAC of in dog then cat

Halothane 0.87 1.19
Iso 1.3 1.7
Sevo 2.1 3.1
Desfl 7.2 10.3



Atropine, glycopyrrolate
Competitively antagonizes Ach


Which anticholinergic doesn't cross BBB? What else doesn't it cross



What is the equation to estimate TV



Rigotti, CF Effect of prewiring on the body temp of small dogs undergoing inhalation anesthesia. JAVMA 2015

Prewarming in an incubator didn't work


Cardia output (CO) equation



Which opioid is best for epidurals and why

Morphine because its not very lypophylic


Drug contraindicated in c-section



Doxapram dose

1.1mg/kg IV