Anesthesia and Analgesia Flashcards
In Henry’s 2014 study “Evaluation and clinical use of an intraoral inferior alveolar nerve block in the horse,” what was the only complication noted and how often were recheck examinations performed?
Pusterla, Verstraete. EVJ 2014
Abscessation of pterygoid fossa 1 horse
24h, 2 weeks, 4 weeks post op
In Henry’s 2014 study “Evaluation and clinical use of an intraoral inferior alveolar nerve block in the horse,” what percent of blocks were clinically successful?
Pusterla, Verstraete. EVJ 2014
100%
In Henry’s 2014 study “Evaluation and clinical use of an intraoral inferior alveolar nerve block in the horse,” the black arrow highligths what structure and an intraoral IANB should be performed what direction in relation to that structure?
Pusterla, Verstraete. EVJ 2014
Black arrow: palatoglossal arch
Injection should be lateral to the palatoglossal arch
In the image below what do the black arrow heads, black arrow, green arrow and white arrow represent?
Henry. “Evaluation and clinical use of an intraoral inferior alveolar nerve block in the horse,” EVJ 2014
Black arrowheads: Facial nerve branches
Black arrow: inferior alveolar artery
Green arrow: Mylohyoid nerve
White arrow: Lingual branch of trigeminal nerve
The white arrowheads are the cut edge of the mandible
What nerve is depicted by the white arrow?
Rice, JVD 2017, issue 2, Step by Step Regional Nerve Blocks for Equine Dentistry
Maxillary nerve
Rice recommended 10-20ml here
What are the landmarks to palpate for the infraorbital nerve block?
Rice, JVD 2017, issue 2, Step by Step Regional Nerve Blocks for Equine Dentistry
Palpation landmarks for the infraorbital nerve block include the nasoincisive notch (white-dashed arrow) and the rostral border of the facial crest (black-dashed arrow).1
Rice recommends 3 ml here
Manual elevation of what muscle facilitates placing the needle within the mental foramen to block the nerve?
Rice, JVD 2017, issue 2, Step by Step Regional Nerve Blocks for Equine Dentistry
depressor labii inferioris muscle
Rice recommends 3 ml here
What volume of anesthetic agent is recommended for the mandibular nerve block in this step by step?
Rice, JVD 2017, issue 2, Step by Step Regional Nerve Blocks for Equine Dentistry
Intraoral approach: 10ml
Extraoral approach: 10-12ml
In Muller’s 2017 study “Effect of butorphanol, midazolam or ketamine on romifidine based sedation in horses during standing cheek tooth removal”, which sedation group was best at reducing chewing behavior?
A. Romifidine
B. Romifidine with butorphanol
C. Romifidine with midazolam
D. Romidifidine with ketamine
BMC Vet Res 2017
C. Romifidine with midazolam
probably related to the relaxation of the masticatory muscles caused by midazolam
In Muller’s 2017 study “Effect of butorphanol, midazolam or ketamine on romifidine based sedation in horses during standing cheek tooth removal”, which sedation group needed the most additional boli of romifidine?
A. Romifidine
B. Romifidine with butorphanol
C. Romifidine with midazolam
D. Romidifidine with ketamine
BMC Vet Res 2017
A. Romifidine
In Johnson’s 2019 JVD study on an US guided inferior alveolar nerve block, what is depicted by the red and blue arrows (this is the right side of the horse)
JVD 2019 issue 1
Blue: mandibular nerve
Red: lingual nerve
In Tanner’s 2019 study “A Retrospective Study of the Incidence and Management of Complications Associated with Regional Nerve Blocks in Equine Dental Patients” what was the incidence of complications with nerve blocks, and what was the most common complication?
JVD 2019 issue 1
2.96%
Hematoma
In Johnson’s 2019 study “Ultrasound-Guided Inferior Alveolar Nerve Block in the Horse: Assessment of the Extraoral Approach in Cadavers”, what % of lingual nerve staining was noted when 2.5ml volume was used? what % when 5 ml used?
JVD 2019 issue 1
2.5ml: Lingual nerve stained in 5/8 (62.5%) of the injections
5ml: Lingual nerve stained in 4/8 (50%) injections
Overall success of staining the inferior alveolar nerve was 75% and 65% respectively for the volumes
In Johnson’s 2019 study “Ultrasound-Guided Inferior Alveolar Nerve Block in the Horse: Assessment of the Extraoral Approach in Cadavers”, what % success was noted on CT for 2.5ml volume and 5 ml volume respectively?
JVD 2019 issue 1
Smaller injection volume (2.5ml) successful in 75% injection compared to larger injection volume (5ml) 87.5% cases
Overall success 81% on CT – differed from overall success 68.8% for dissection of methylene blue staining
In Gozalo-Marcilla’s 2019 paper “Sedative and antinociceptive effects of different detomidine constant rate infusions, with or without methadone in standing horses,” which protocol produced the most intense and persistent antinociceptive effects?
EVJ 2019
Higher detomidine dose combined with methadone (DHM)
In Gozalo-Marcilla’s 2019 paper “Sedative and antinociceptive effects of different detomidine constant rate infusions, with or without methadone in standing horses,” what protocols lead to reduced gastrointestinal motility and for what duration?
EVJ 2019
All treatments reduced gastrointestinal motility
scores returned to baseline sooner for the low dose detomidine and low dose detomidine plus methadone groups
In Weber’s 2019 study “Ex vivo evaluation of the distribution of a mixture of mepivacaine 2% and iopromide following local infiltration of the infraorbital nerve via the infraorbital foramen,” what variable was associated with higher canal filling %?
A. volume 10 ml
B. volume 15 ml
C. age
D. legnth of needle
EVE 2019
C. age
In Weber’s 2019 study “Ex vivo evaluation of the distribution of a mixture of mepivacaine 2% and iopromide following local infiltration of the infraorbital nerve via the infraorbital foramen,” what % of canals had complete legnth filling associated with the 10 ml volume and 15 ml volume respectively? Was this stat significant?
EVE 2019
10 ml volume: 90%
15 ml volume: 70%
Not statistically signficant
In Weber’s 2019 study “Ex vivo evaluation of the distribution of a mixture of mepivacaine 2% and iopromide following local infiltration of the infraorbital nerve via the infraorbital foramen,” what % of the canal was filled by the 10ml volume?
EVE 2019
86.9%
So 90% of the blocks were filled 86.9% in volume
In Weber’s 2019 study “Ex vivo evaluation of the distribution of a mixture of mepivacaine 2% and iopromide following local infiltration of the infraorbital nerve via the infraorbital foramen,” what % of the canal was filled by the 15ml volume?
EVE 2019
74%
So 70% of the blocks were filled 74% in volume
In Rawlinson’s 2018 study “Evaluation of the equine mental foramen block: cadaveric and in vivo injectate diffusion,” what technique was determined to be most efficacious?
Vet Anes 2018
T2 → needle inserted in a dorsolateral to ventromedial direction with shaft of needle 40 degrees lateral to the parasagittal plane of the lateral mandible and 25 degrees dorsal to the dorsal plane of incisive-premolar interproximal space to depth of 1cm into canal
In Rawlinson’s 2018 study “Evaluation of the equine mental foramen block: cadaveric and in vivo injectate diffusion,” what pattern of injectate distribution and needle placement was seen for T1 vs T2?
Vet Anes 2018
Bolus patterns associated with T2
Thread patterns with T1
All T2 needle tips intracanal
All T1 needle tips embedded in bone
In Rawlinson’s 2018 study “Evaluation of the equine mental foramen block: cadaveric and in vivo injectate diffusion,” why was the 5ml injectate volume found to be superior?
Vet Anes 2018
The 5ml volume terminated in the caudal canal in 50% (6/12) vs 3ml volume 25% (3/12)
no difference between injectate volumes on distance traveled within canal, diffusion pattern and length of circumferential nerve staining
Rawlinson’s 2018 study “Evaluation of the equine mental foramen block: cadaveric and in vivo injectate diffusion,” cites the critical length of nerve exposed to a local anesthetic to reduce or block impulse conduction as how many miilimeters of exposed nerve?
Vet Anes 2018
6 to > 30mm
Rawlinson’s 2018 study “Evaluation of the equine mental foramen block: cadaveric and in vivo injectate diffusion,” suggest that what percent of mental nerve blocks will be effective?
Vet Anes 2018
30-60%
30% based on in vivo testing, 60% based on cadaveric testing
Rawlinson’s 2018 study “Evaluation of the equine mental foramen block: cadaveric and in vivo injectate diffusion,” sites that how many nodes of Ranvier must be blocked to achieve anesthesia of myelinated nerves?
3 (internodal length for mammalian fibers ~1mm)
In Best’s study “A blinded crossover study design to evaluate midazolam as an adjunct for equine standing sedation for routine oral examinations” what was the outcome between the midaz group and placebo group?
Best 2024 J Eq Vet Science
There were no significant differences in any of the single or overall sedation scores between treatment groups or within individual horses (P=0.3).
Trends towards improvement of some assessed characteristics of sedation, including decreased tongue movement and less resistance to acceptance of speculum were observed.
Nervous horses may benefit from which anxiolytic drug prior to dental procedures?
A. Tramadol
B. Trazodone
C. Detomidine
D. Ketamine
Easley Textbook, ch 23
Trazodone
Dose 2.5-10mg/kg orally twice daily. Recommend testing dose a few days prior to procedure
Acepromazine is another anxiolytic given IV 20-30 minutes prior to procedure
Which of the following are common side effects of alpha-2-agonists?
A. Tachycardia, hypotension, decreased GI motility, and polyuria
B. Tachycardia, hypertension, decreased GI motility, and anuria
C. Bradycardia, hypotension, increased GI motility, and polyuria
D. Bradycardia, hypertension, decreased GI motility, and polyuria
Easley Textbook, ch 23
D. Bradycardia, hypertension, decreased GI motility, and polyuria
What is the duration of the following opioids?
Buprenorphine
Morphine
Butorphanol
Easley Textbook, ch 23
Buprenorphine duration is 8-12 hours
Morphine duration 4-6 hours
Butorphanol duration 30-60 min
Lidocaine is commonly used for its analgesic, anti-inflammatory, and antiendotoxaemic properties. However, toxicity is possible; whatis a sign of toxicity and a good indicator lidocaine infusion should be stopped?
Easley Textbook, ch 23
Muscle fasciculation
What are the following locoregional anaesthetic drug time to onset and durations:
Lidocaine
Mepivicaine
Bupivicaine
Easley Textbook, ch 23
Lidocaine - < 2 min, 1-2 hours
Mepivicaine - <2 min, 1.5-3 hr
Bupivicaine - 5-10 min, 3-8 hours
Maxillary nerve block desensitizes which structures?
Easley Texbook, ch 23
Ipsilateral maxillary teeth and gingiva, soft tissues rostral to infraorbital foramen, and nasal vestibule
+/- lacrimal nerve → lubricate ipsilateral eye every 30 minutes during procedure
The infraorbital nerve block desensitizes which structures?
Easley Texbook, ch 23
Ipsilateral maxillary teeth and gingiva, soft tissues rostral to infraorbital foramen, and nasal vestibule
If only passed slightly into foramen, doesn’t always anaesthetise molars
The inferior alveolar nerve block desensitizes which structures?
Easley Texbook, ch 23
Ipsilateral mandibular alveolar mucosa, teeth, gingiva, skin and labial mucosa rostral to mental foramen
The mental foramen nerve block desensitizes which structures?
Easley Textbook, ch 23
ipsilateral alveolar mucosa, incisors and canine teeth, and labial mucosa, skin, and gingiva rostral to mental foramen
Mental nerve block desensitizes only the ipsilateral lower lip
What are some nerve block complications for the maxillary nerve block?
Easley Textbook, ch 23
retrobulbar hematoma, decreased lacrimation of ipsilateral eye
What are some nerve block complications for the infraorbital nerve block?
Easley Textbook, ch 23
puncture of adjacent blood vessels, abscess
What are some nerve block complications for the inferior alveolar nerve block?
Easley Textbook, ch 23
lingual anaesthesia, abscess, lingual trauma
What are some nerve block complications for the mental nerve block?
Easley Textbook, ch 23
abscess, muzzle trauma
In McAndrews’ study “Evaluation of Three Methods of Sensory Function Testing for the Assessment of Successful Maxillary Nerve Blockade in Horses,” what was the success rate of the maxillary nerve blocks?
JVD 2023
73% success rate
In McAndrews’ study “Evaluation of Three Methods of Sensory Function Testing for the Assessment of Successful Maxillary Nerve Blockade in Horses” what nerve stimulation techniques were more reliable?
JVD 2023
Needle prick and nostril clamping with a hemostate
gingival algometry not as reliable
According to Easley 2022 what are the reported advantages of standing sedation over general anesthesia for dental procedures?
Chp 23
Decreased surgical hemorrhage
increased client compliance
improved access to both sides of head
reduced frustration with endotracheal tube positioning
What is the mechanism of action of trazodone?
Easley 2022, chp 23
Serotonin receptor antagonist/reuptake inhibitor
anxiolytic drug
recommended dosing 2.5-10mg/kg PO q12h
What are common cardiac side effects of alpha-2 agonists?
Easley 2022, chp 23
Bradycardia (second degree AV block most common bradyarrhythmia)
Decreases cardiac output –> initial increase in peripheral vascular resistance leading to hypertension followed by normo to hypotension
What are common non-cardiac side effects of alpha-2 agonists?
Easley 2022, chp 23
Hyperglycemia
polyuria
decreased GI motility
ataxia
What are uncommon possible complications associated with alpha-2 agonists?
Easley 2022, Chp 23
Paradoxical aggression –> effects on alpha-1 adrenergic receptors, more common with xylazine followed by detomidine (lower alpha-1: alpha-2 selectivity)
Respiratory distress –> occurs in febrile horses sedated with alpha-2s, tachypnea leading to respiratory distress
Combining alpha-2 agonists with opioids results in what percent reduction of each drug dose alone?
Easley 2022, Chp 23
near 50%
What is the duration of action of butorphanol and what side effect is it associated with?
Easley 2022
30 minutes to 1 hour
Head twitching
Marly 2014, Clarke 1991
What is the duration of action of morphine and what dose should not be exceeded in a 4 hour period?
Easley 2022, Chp 23
duration 4-6 hours
0.2mg/kg over 4 hour period max dose
What occurs when morphine is administered IV quickly?
Easley 2022, chp 23
Histamine release
Excitement
should be given slowly
What is the onset and duration of buprenorphine?
Easley 2022, Chp 23
onset 45-60 minutes for peak effect
druation 8-12 hours
Provides adequate sedation and analgesia but may have more side effects and postop complications compared to morphine
What are the advantages and disadvantages with using midazolam for standing sedation procedure?
Easley 2022, Chp 23
Advantages: reduction in chewing activity and tongue movements
Disadvantages: significantly more ataxic (likely due to muscle relaxation properties), midazolam alone causes severe excitement
What kind of needles are recommended for nerve blocks?
Easley 2022, Chp 23
Tuohy –> rounded bevel with offset cutting edges that push vasculature and nerves away from cutting edge
In Synder’s 2016 study “Effects of buprenorphine added to bupivacaine infraorbital nerve block on isoflurane minimum alveolar concentration using a model for acutre dental/oral surgical pain in dogs,” what was the duration of action for the infraorbital nerve blocks?
JVD 2016
36-48 hours
1ml of 0.5% bupivacaine with 0.3ml of 0.3mg/ml buprenorphine
What can be used to deliver topical anesthetics?
Easley 2022, Chp 23
Catheter
Laryngo-tracheal mucosal atomizer
How far caudal to the point where the facial crest dorsally deviates to become part of the rostral zygomatic arch should the injection site for the extraperiorbital fat body insertion technique (EFBI) be placed?
Easley 2022, chp 23
2-3cm
In Nannarone’s 2016 study “Retrograde maxillary nerve perineural injection: A tomographic and anatomical evaluation of the infraorbital canal and evaluation of the needle type and size in equine cadavers,” what was the median infraorbital foramen hieght and width?
The Vet J 2016
median height 1.2cm
median width 0.6cm
infraorbital foramen is ellipitcal shaped
In Nannarone’s 2016 study “Retrograde maxillary nerve perineural injection: A tomographic and anatomical evaluation of the infraorbital canal and evaluation of the needle type and size in equine cadavers,” what was the described shape of infraorbital canal and what was the median length?
The Vet J 2016
Serpentine
median length 13.6cm
In Nannarone’s 2016 study “Retrograde maxillary nerve perineural injection: A tomographic and anatomical evaluation of the infraorbital canal and evaluation of the needle type and size in equine cadavers,” how was obstruction to passage of a 21 gauge Tuohy needle into the infraorbital canal resolved?
The Vet J 2016
Retracting the needle 0.5-1cm and slightly rotating needle when advancing
Describe the maxillary nerve block via infraorbital canal technique described by Nannarone in their 2016 paper “Retrograde maxillary nerve perineural injection: A tomographic and anatomical evaluation of the infraorbital canal and evaluation of the needle type and size in equine cadavers.”
The Vet J 2016
Manual elevation of the levator labii superioris muscle and infraorbital nerve
insertion of a 19G x 8cm Tuohy needle with bevel directed laterally along floor of infraorbital foramen with careful rotation until entire needle inserted
10ml injected
Quincke needles found to be more difficult to insert (straight sharp tip)
In Weber’s 2019 study “Ex vivo evaluation of the distribution of a mixture of mepivacaine 2% and iopromide following local infiltration of the infraorbital nerve via the infraorbital foramen,” needle insertion how far into the infraorbital canal with what volume of injectate adequately filled the infraorbital canal to the maxillary foramen?
Equine Vet Educ 2019.
3cm
10ml
In Weber’s 2019 study “Ex vivo evaluation of the distribution of a mixture of mepivacaine 2% and iopromide following local infiltration of the infraorbital nerve via the infraorbital foramen,” increased retrograde rostral leakage and into the maxillary sinus was greater with what volume of injectate?
Equine Vet Educ 2019
15ml
tested 15ml vs 10ml inserting both 3cm into canal with 22G 3cm long needle
What are the landmarks for finding the infraorbital foramen?
Easley 2022. chp 23
line between the nasoincisive notch and point of the facial crest
displace the levator nasolabialis muscle and palpate the infraorbital foramen 1-2cm caudal to midpoint of line
In Harding’s 2012 study “Comparison of two approaches to performing an inferior alveolar nerve block in the horse,” what two methods were evaluated, what were the reported success rates for each, and was the difference stat sig?
Aust Vet J 2012
Angled vs vertical
angled success rate 73%
vertical success rate 59%
No stat sig difference between the two
Henry’s 2014 study “Evaluation and clinical use of an intraoral inferior alveolar nerve block in the horse,” showed that location of the mandibular foramen can vary up to how many mm from the third molar tooth and how many mm from the ventral border of the mandible? How about from the rostral edge of the ramus?
EVJ 2014
59 +/- 7.7mm caudal to third molar tooth
123 +/- 9.4mm from ventral surface of mandible
36 +/- 4.7mm from rostral edge of ramus
In Easley’s 2022 text, what landmarks are suggested for localizing the mandibular foramen from an extraoral approach?
chp 23
line drawn 1cm dorsal to the alveolar crest of the mandibular premolars and a line between the lateral mandibular condyle and the ventral aspect of the mandible where the facial vein is located
these modifications eliminate reliance on eye position and dental height which vary with age and breed
What the difference between the mental nerve block and the mental foramen block?
Easley 2022, chp 23
mental nerve block targets only the mental nerve rostral to the foramen so only desensitizes the ipsilateral lower lip
mental foramen block targets the rostral inferior alveolar nerve and mendtal nerves so desensitizes the lower lip and dental structures
In Rawlinson’s 2018 study “Anatomic analysis of the equine mental foramen and rostral mandibula canal using computed tomography,” where was the mental foramen located along the mandible?
Vet Anaesth Analg 2018
2/3rd the distance along the incisor-premolar interdental space from the third incisor and 1/3rds the height of the mandible from the dorsal surface of the interdental space
In Rawlinson’s 2018 study “Anatomic analysis of the equine mental foramen and rostral mandibula canal using computed tomography,” what was the mean mental foramen size and what morphological variations were seen?
Vet Anaesth Analg 2018
mean size 6.4mm x 5.6mm
bifurcated (n=1) and double foramina (n=3) observed
In Rawlinson’s 2018 study “Anatomic analysis of the equine mental foramen and rostral mandibula canal using computed tomography,” what were the mean angles of the mental foramen into the mandibular canal in transverse, sagittal and dorsal planes respectively?
Vet Anaesth Analg 2018
transverse: 68 degrees
sagittal: 28 degrees
dorsal: 41 degrees
In Rawlinson’s 2018 study “Anatomic analysis of the equine mental foramen and rostral mandibula canal using computed tomography,” the rostral mandibular canal was found to have varying levels of circumferential mineralization with what percent of canals having no visible bony walls to the level fo the second premolar? Lack of mineralization was more common in what age of horses?
Vet Anaesth Analg 2018
~30%
older horses
When performing an extraoral mental foramen block, what muscle is retracted dorsally?
Easley 2022, chp 23
depressor labii inferioris
Cardiac arrest can occur with the maxillary nerve block if the local anesthetic is injected into what structure?
Easley 2022, Chp 23
Dural cuff of the optic nerve
In Tanner’s 2019 study “A Retrospective Study of the Incidence and Management of Complications Associated with Regional Nerve Blocks in Equine Dental Patients” what is the reported incidence of lingual trauma 24 hours post injection for the inferior alveolar nerve block?
JVD 2019
4%
What is the mortality rate for elective, non-emergency general anesthesia procedures for equine patients as compared to dogs?
Easley 2022, chp 23
equine 1%
dogs 0.1%
What percentage of equine general anesthesia fatalities are associated with recovery and what are the most common causes of fatalities in that peroid?
Easley 2022, chp 23.
Over a third
fractures and myopathies
What inhalants are favored in lengthy dental procedures and why?
Easley 2022, chp 23
sevoflurane and desflurane
due to their low solubility coefficients –> faster clearance and recovery times
What mean arterial pressure should the blood pressure be kept at and above?
Easley 2022, chp 23
75mmHg
Why should arterial blood gases be evaluated intermittently in horses under GA?
Easley 2022, chp 23
Pulse oximetry and capnography may not be very accurate in the horse
pulse oximetry tends to underestimate hemoglobin saturation
ET-PaCO2 differences can be 15mmHg
Overextension of the head can result in what complication?
Easley 2022, chp 23
Laryngeal paralysis –> increased risk for upper airway obstruction in recovery
In Potter’s 2016 study “Preliminary investigation comparing a detomidine continuous rate infusion combined with either morphine or buprenorphine for standing sedation in horses,” which treatment group had stat sig higher intraoperative sedation scores?
Vet Anaesth Analg 2016
Buprenorphine
No differences in ataxia scores, heart rate, or overall adequacy of sedation
In Potter’s 2016 study “Preliminary investigation comparing a detomidine continuous rate infusion combined with either morphine or buprenorphine for standing sedation in horses,” what treatment group had at least one postoperative complication in all cases and which treatment group had no postoperative complications?
Vet Anaesth Analg 2016
Buprenorphine all had complications
Morphine all had no complications
In Stauffer’s 2017 paper “Maxillary nerve blocks in horses: an experimental comparison of surface landmark and ultrasound-guided techniques,” what were the success rates with surface landmarks, standard ultrasound guidance, and SonixGPS guidance?
Vet Anaesth Analg 2017
Surface landmarks 50%
Standard ultrasound guidance 65%
SonixGPS 83%
In Stauffer’s 2017 paper “Maxillary nerve blocks in horses: an experimental comparison of surface landmark and ultrasound-guided techniques,” what was the overall complication rate and what stat sig differences in complication rates were present?
Vet Anaesth Analg 2017
complication rate 54%
No sig difference in complication rate found between the three methods
In Tanner’s 2019 study “A Retrospective Study of the Incidence and Management of Complications Associated with Regional Nerve Blocks in Equine Dental Patients” what nerve block had no reported complications?
JVD 2019
infraorbital
In Iacopetti’s 2015 study “The Inferior Alveolar Nerve of the Horse: Course and Anatomical Relationship with Mandibular Cheek Teeth,” in 95% of horses where does the nerve change directions between the mesial root of one tooth and the distal root of another?
Anat Histo Embryol 2015
Between the mesial root of M1 and the distal root of PM4
In Iacopetti’s 2015 study “The Inferior Alveolar Nerve of the Horse: Course and Anatomical Relationship with Mandibular Cheek Teeth,” where does the inferior alveolar nerve course relative to the apices of the molar teeth vs the premolar teeth?
Anat Histo Embryol 2015
IAN ventral to the apices of the molar teeth
PM4: lingual to roots and coronal to the apices
PM2, PM3: lingual to roots and in proximity to the apices
Which of the following is correct regarding cardiac output?
A. Bradycardia diminishes cardiac output by reducing stroke volume
B. Tachycardia diminishes cardiac output by reducing stroke volume
C. Afterload impedance to cardiac output is a common problem under GA
D. Cardiac output determines systemic vasomotor tone
Lumb and Jones
B. Tachycardia diminishes cardiac output by reducing stroke volume
Stroke volume is determined by what two factors?
Lumb and Jones
Preload
Myocardial contractility
Cardiac output is determined by what two factors?
Lumb and Jones
Heart rate
Stroke volume
What two factors determine blood pressure?
Lumb and Jones
Cardiac output
Peripheral vasomotor tone
What is the important determinant of peripheral tissue perfusion?
Lumb and Jones
Peripheral vasomotor tone
What is the important determinant of brain and heart perfusion?
Lumb and Jones
Arterial blood pressure
What two factors determine blood oxygen content?
Lumb and Jones
Hemoglobin concentration
Oxygenation
What two factors determine oxygen delivery?
Lumb and Jones
Oxygen content
Cardiac output
What eyeball positions are associated with light and deep and light-medium to deep-medium anesthetic depth respectively?
Lumb and Jones
Light and deep: central
light-medium and deep-medium: rotated medioventrally
At what heart rate or below should horses be treated for bradycardia?
Lumb and Jones
< 25 bpm
What are common causes of bradycardia that are not responsive to pharmacological treatment?
Lumb and Jones
Severe hypothermia
Cardiac conduction abnormalities
Severe myocardial hypoxemia
What classes of drugs are used to treat bradycardia?
Lumb and Jones
anticholinergics
sympathomimetics
What factors were associated with increased risk of death for horses undergoing acute emergency abdominal surgery?
Lumb and Jones
Long duration of anesthesia
Hypotension
What is the internal diameter of a size 6 endotracheal tube?
Lumb and Jones
6mm
Tube sizing often reflects the internal diameter of the tube
What type of endotracheal tube is most commonly used in large and small animals?
Lumb and Jones
cuffed Murphy type tube
What is the purpose of the Murphy eye/hole in a Murphy endotracheal tube?
Lumb and Jones
To provide an alternative route for gas flow if the beveled opening became occluded
What muscles are incised to perform a tracheotomy?
Equine Surgery 5th edition.
Cutaneous colli (more superficial)
paired sternothyrohyoideus muscles
What direction should a tracheotomy incision be made in and what percent of the tracheal circumference should the tracheotomy incision not exceed?
Equine Surgery 5th edition
the annular ligament should be incised parallel to the orientation of the rings
should not exceed 50% of the tracheal circumference
parallel to rings incision prevents postsurgical tracheal collapse and granulation tissue formation
Systolic blood pressure is primarily determined by what cardiovascular factors?
Lumb and Jones
Stroke volume
Arterial system compliance
Diastolic pressure is primarily determined by what cardiovascular factors?
Lumb and Jones
Vasomotor tone
Heart rate
How is cardiac preload clinically assessed?
Lumb and Jones
End diastolic diameter via echocardiography
Diameter of posterior vena cava via chest rads
Ease of jugular vein distension
In horses what can be used as a surrogate marker of central venous pressure?
Lumb and Jones
Jugular venous pressure
What is the normal central venous pressure of laterally recumbent vs dorsally recumbent or standing horses?
Lumb and Jones
laterally recumbent: 15-20 cmH2O
dorsally recumbent or standing: 5-10cmH2)
Positive pressure ventilation impedes what cardiovascular factors?
Lumb and Jones
Intrathoracic venous return
diastolic filling of the heart
stroke volume
Large and small stroke volumes are associated with what pulse and pulse pressure waveform characteristics?
Lumb and Jones
Bounding pulse → tall, wide waveform → likely associated with large stroke volume
Thready pulse → short, narrow waveform → small stroke volume
What causes hemoglobin concentration to decrease during general anesthesia?
Lumb and Jones
Anesthetic induced vaso and splenic dilation
Administration of non-hemoglobin containing fluids
Intraoperative blood loss
Decreased fractional shortening is indicative of what change to contractility?
Lumb and Jones
Decreased
What causes vasoconstriction?
Lumb and Jones
hypovolemia
heart failure
hypothermia
vasoconstrictor drug administration
What causes vasodilation?
Lumb and Jones
Systemic inflammatory response
hyperthermia
administration of vasodilator drugs
What breathing pattern is described as cycling between hyperventilation and hypoventilation, and may be seen in a healthy anesthetized horse?
Lumb and Jones
Cheyne-Stokes breathing
Which capnograph indicates that the sample port is too close to fresh gas inflow?
Lumb and Jones
c.
Which capnograph is indicative of excessive alveolar deadspace (hypovolemia, thromboembolism)?
Lumb and Jones
e.)
Which capnograph is indicative of deadspace rebreathing?
Lumb and Jones
f.)
An increased arterial-venous PCO2 gradient suggests what in terms of tissue perfusion?
Lumb and Jones
Decreased tissue perfusion
How would you troubleshoot the following capnograph?
There is a slant to the upstroke portion of the expiratory phase of the breathing cycle - this may indicate a kinked endotracheal tube, an obstructed endotracheal tube, partial airway obstruction or bronchospasm.
How would you troubleshoot the following capnograph?
Lumb and Jones
The baseline is not returning to zero, there may be exhausted CO2 absorbing granules, incompetent or absent unidirectional valves, decreased oxygen flow rate in a non-rebreathing circuit, or damaged non-rebreathing circuits.
How would you troubleshoot the following capnograph?
There is no plateau or an abnormal downstroke present on inhalation –> check the endotracheal tube cuff!
What is the lowest body temperature not associated with detrimental effects?
Lumb and Jones
96F
What body temperatures can cause ventricular fibrillation?
Lumb and Jones
72-74F
What body temperatures cause marked CNS depression?
Lumb and Jones
82-86F
Shivering will not occur → require artificial rewarming
Atrial arrhythmias may occur, O2 consumption reduced to 50%, heart rate + cardiac output about 35-40% of normal, arterial blood pressure to about 60%, cerebral metabolism ~25%
Cell damage starts at what hyperthermic temperature?
Lumb and Jones
108F
Oxygen delivery can no longer keep up with incr metabolism and O2 consumption
What is the difference between a tranquilizer and a sedative?
Lumb and Jones
Tranquilizers induce a feeling of calm but do not reduce overall response to external stimuli like a sedative
Phenothiazines work on what receptors?
Lumb and Jones
Adrenergic
Muscarinic
Dopaminergic
Serotonergic
Histamine
What is the mechanism of action for the sedative effects of phenothiazines?
Lumb and Jones
dopamine receptor (D2) blockage
Acepromazine (sedative) 0.1mg/kg IV decreases mean aortic pressure and cardiac output by what percents respectively?
Lumb and Jones
aortic pressure 20-30%
Cardiac output 10-15%
What is the mechanism of action of benzodiazepines?
Lumb and Jones
Ehance GABA receptor’s affinity for GABA
increased chloride conductance and hyperpolarization of postsynaptic cell membranes. (alpha1 and alpha 2 subunits)
What is the mechanism of action for alpha-2 agonists?
Lumb and Jones
binding receptors in the nociceptive pathways in the brainstem and dorsal horn of the spinal cord
afferent input modulated and reduces norepinephrine release (presynaptic inhibition) and occupancy of those receptors (postsynaptic inhibition)
What is the mechanism of action for bradycardia by alpha 2 adrenergic receptor agonists?
Lumb and Jones
Increased systemic vascular resistance
Reduced central symphathetic outflow
What is the onset and duration of action of xylazine?
Lumb and Jones
Onset 5-10 minutes
Duration 30-60 minutes
What is the onset and duration of detomidine?
Lumb and Jones
onset 5 minutes
duration 1 hour
How does the onset to peak sedation and duration of romifidine compare to xylazine and detomidine?
Lumb and Jones
longer onset and duration (15 minutes to peak sedation)
What adrenergic receptor antagonists are typically used for dexmedetomidine and xylazine respectively?
Lumb and Jones
Dexmedetomidine: atipamezole
Xylazine: yohimbine, tolazine
What is the definition of potency?
Lumb and Jones
the relative dose needed to elicit a response
Not related to duration of effect or efficacy
What is first pass metabolism?
Lumb and Jones
The intestinal lining and liver biotransform a portion of the medication into a form that is not systemically effective
Systemic opioid doses are most effective at decreasing nociception of which nerve fibers?
C fibers (slow conducting, unmyelinated nerves associated with dull aching pain)
less effective on A delta fibers (fast conducting, myelinated nerves associated with sharp, discrete pain)
Opioids tend to cause what change to pupil diameter in horses and cats?
Lumb and Jones
Mydriasis
Morphine and butorphanol tend to impair coordination of motility of what parts of the gastrointestinal tract specifically?
Lumb and Jones
Morphine: colon
Butorphanol: jejunum
What opioid receptors ehance urine production?
Lumb and Jones
kappa
What is the mechanism of action for urine retention with opioid use?
Lumb and Jones
Decrease in detrusor muscle contraction
Increased tone of urinary sphincters
Inhibition of micturition
Cats and horses tend to experience what thermoregulation response to opioid use?
Lumb and Jones
Hyperthermia
Which opioid is effective as an NMDA antagonist?
Lumb and Jones
Methadone
more effective analgesic for chronic and refractory pain
What opioid has reported hyperesthesia, muscle fasciculations, sweating and adverse CV effects reported in horses?
Lumb and Jones
Meperidine (pethidine)
Buprenorphine is how many times more potent than morphine?
Lumb and Jones
25 times
What is the IV onset to action of buprenorphine and the duration of action?
Lumb and Jones
20 minutes
4-12 hours (dependent on route)
Oral transmucosal route of buprenorphine is effective in what species?
Lumb and Jones
Dogs and cats
not horses
What opioid receptors does butorphanol act on?
Lumb and Jones
Mu antagonist to partial mu agonist
kappa agonist
Naloxone works primarily on what opioid receptors?
Lumb and Jones
mu antagonist
What is dantrolene used to treat?
Lumb and Jones
Malignant hyperthermia
Rhabdomyalosis
What are the general effects of guaifenesin?
Lumb and Jones
Centrally acting skeletal muscle relaxant with sedative properties
Co-administered with anesthetic agents for induction and maintenance of general anesthesia
What are the properties/effects of methocarbamol?
Lumb and Jones
centrally acting muscle relaxant that selectively inhibits spinal and supraspinal polysynaptic reflexes through its action on interneurons without direct effects on skeletal muscle
What is the molecular mechanism of action of local anesthetics?
Lumb and Jones
Primary ion channel blockers
Blockade of inward sodium currents through voltage gated sodium channels which impedes membrane depolarization and nerve excitation and conduction
Also block voltage dependent potassium and calcium channels
act on intracellular G-protein coupled receptors
What percent of sodium conductance at 3 or more nodes of Ranvier of a myelinated nerve fiber must be blocked to achieve local anesthesia?
Lumb and Jones
> 84%
What is the chemical structure of lidocaine, mepivacaine and bupivacaine?
Lumb and Jones
amino-amides
metabolized by the liver
What effects have been shown when alpha-2 adrenergic receptor agonists are added to local anesthetics?
Lumb and Jones
Shorter onset
longer duration of sensory and motor block
enhanced block quality, lower pain scores, decreased systemic opioid requirement
What are the signs and results of cardiac toxicity secondary to local anesthetics?
Lumb and Jones
Prolonged PR and QRS intervals, hypotension, bradycardia, respiratory arrest, asystole
What is allodynia?
Lumb and Jones
Pain due to a stimulus which does not normally provoke pain.
What is the only class of analgesic drugs that prevent nociception transmission?
Lumb and Jones
Local anesthetics
Does COX1 or COX2 act centrally?
Lumb and Jones
COX1- antinociceptive effects at level of the brain, spinal cord
Which classes of analgesics prevent generation of noxious stimuli?
Local anesthetics
NSAIDs
Opioids modulate pain by increasing the pain threshold but do not prevent generation of noxious stimul
What arrhythmia does high dose dobutamine cause?
Ventricular tachycardia
What are the reported complication after maxillary nerve block?
Easley ch 29
Retrobulbar hematoma
Globe prolapse
Horner’s signs
Laceration of the tongue can be a complication of which nerve block?
Easley ch 29
Inferior alveolar
What are possible causes of this ETCO2 waveform?
Equine Anesthesia, Hubbel, ch 8
What are the possible causes of this ETCO2 waveform?
Equine Anesthesia, Hubbel, ch 8
What possible causes are there for this ETCO2 waveform?
Equine Anesthesia, Hubbel, ch 8
What causes are there for this waveform ETCO2?
Equine Anesthesia, Hubbel, ch 8
Name this ECG
Equine Anesthesia, Hubbel, ch 3
Sinus arrhythmia
Name this ECG
Equine Anesthesia, Hubbel, ch 3
Sinus tachycardia. Note the shortening of the P wave, PR, and QT intervals; the depression of the PR segment; and the elevation of the ST-T wave—all of which are physiologic changes observed with tachycardia.
Name this ECG
Equine Anesthesia, Hubbel, ch 3
2nd degree AV block (p waves without QRS)
Common in horses sedated with alpha-2s
Name this ECG
Equine Anesthesia, Hubbel, ch 3
Sinus arrest - give atropine to restore
What are the ECGs in A and B
Equine Anesthesia, Hubbel, ch 3
A. Atrial tachycardia
B. Atrial flutter
A - Regular abnormal P waves (P’) are evident through-
out the strip, with many superimposed on the QRS and T complexes. Most of ectopic P waves are blocked in
the AV node and are not conducted to the ventricles.
B - Atrial activity is characterized by
saw-toothed flutter waves (F) occurring at a rapid rate and regular intervals.
Name this ECG
Equine Anesthesia, Hubbel, ch 3
Ventricular tachycardia
What can cause this ECG reading?
Equine Anesthesia, Hubbel, ch 3
Hyperkalemia produced atrial standstill, a ventricular conduction disturbance (wide QRS), and ST-T abnormalities
How does the choice in inotropic drugs dopamine and dobutamine differ?
Equine Anesthesia, Hubbel, ch 3
Dopamine is preferred for treating bradycardia and hypotension
Dobutamine is preferred for treating hypotension without bradycardia
Both used for bradycardia!
What are side effects of dobutamine?
Equine Anesthesia, Hubbel, ch 3
Dose-dependent effects
Vasoconstriction
Tachycardia
Ventricular arrhythmias
How does hematocrit differ in donkeys compared to horses?
Equine Anesthesia, Hubbel, ch 18 (Nora Matthews)
Donkeys are adapted to the desert; increases in hematocrit, commonly seen with dehydration in horses, do not occur until donkeys are approximately 30% dehydrated
What condition are donkeys predisposed to when anorexic?
Equine Anesthesia, Hubbel, ch 18 (Nora Matthews)
Hyperlipidemia
How does the jugular vein differ in donkeys to horses when trying to get venous access?
Equine Anesthesia, Hubbel, ch 18 (Nora Matthews)
Cutaneous colli muscle is a sheet of fascia, and the skin is thicker
Needles should be angled more perpendicular to the skin in donkeys
How does the facial artery differ in donkeys?
Equine Anesthesia, Hubbel, ch 18 (Nora Matthews)
the anatomy of the branches of the facial artery
(i.e., the artery that is located under the temporal crest) makes it difficult to place an arterial catheter in that location
How do vitals differ in donkeys compared to horses?
Equine Anesthesia, Hubbel, ch 18 (Nora Matthews)
HR response to exercise/pain the same
Body temp may increase higher in donkeys in warm climates or exercise
Resp rates higher in donkeys - 20 to 30 breaths/min is normal at rest
HR most reliable to indicate pain in a donkey as they are so stoic
How does sedative dosing differ for mules and donkeys?
Equine Anesthesia, Hubbel, ch 18 (Nora Matthews)
same drugs as horses
mules require 50% more drug than donkeys or horses to achieve adequate sedation
Ketamine after sedation with an a2-agonist is generally acceptable but is metabolized more rapidly in donkeys and mules than in horses
ketamine - Faster metabolism in conjunction with a more
rapid distribution phase results in higher doses and more frequent readministration
How shoud your combination for GKX differ for donkeys?
Equine Anesthesia, Hubbel, ch 18 (Nora Matthews)
Increase the concentration of ketamine - 2 g/L rather than 1g/L in the horse
what nerves innervate the TMJ, and what block(s) should be performed for a condylectomy?
Sanders EVE 2014
branches of maxillary (zygomaticotemporal and zygomaticofacial) and the mandibular (auriculotemporal) nerves
Perform both ipsilateral maxillary and mandibular nerve blocks
Facilitated a standing condylectomy in this case report
What is the genetic defect of concern with HYPP? And how prevalent is it?
Doherty, Manual of Equine Anesthesia and Analgesia
Defect in NA-K pump
Excess Na –> Increased serum K+
Less negative resting potential –> triggered more (why muscle fasciculations are 1st sign)
0.4% American QH; 2% registered QH
What clinical signs during anesthesia would make you susptect HYPP?
Doherty, Manual of Equine Anesthesia and Analgesia
Prolonged recovery = #1
Muscle fasciculations
ECG changes: inc amplitude T wave, wide QRS, dec amplitude P wave)
Tachycardia –> bradycardia
Hyperthermia
What muscle is being lifted here in Rice’s JVD step by step?
JVD 2017
levator labii superioris muscle
Different than muscle listed in Ch 23 of Easley 2022!
