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Boards: Species > Amphibians > Flashcards

Amphibians Flashcards

1
Q

Amphibians, Habitus

A

three orders with over 6000 species (new added every year)
–Includes frogs, toads, newts, salamanders, sires

Variety of habitats
○ Aquatic, semi-aquatic, terrestrial
○ Rainforest to temperate zones

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2
Q

Metamorphosis of Amphibians

A

Change from strictly aquatic egg and larval stages to an adult stage can be terrestrial, semi-aquatic or aquatic

Loss of tail, gills

Development of lungs - some pedomorphic species will utilize branchial (gill) resp as adults

2 to 3 chambered heart

Development of 4 legs

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3
Q

Unique Feature of Amphibians

A

■ Multiple forms of breathing
● Gills, lungs, skin, buccopharyngeal
■ Semi-permeable skin
■ Renal portal system

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4
Q

Anatomy of Adult Amphibian Hearts

A

Three-chambered heart: two atria, one ventricle
● Right atrium larger than left
● Thick-walled ventricle with numerous tabercules

Caudatas - interatrial septum can be incomplete (fenestrated)
● Complete in Anurans

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5
Q

Arterial/Venous Vascular System in Adult Amphibians

A

Incomplete double circulation

Extensive lymphatics

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6
Q

Tadpole CV System

A

■ Two-chambered heart
■ Single-loop circulation

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7
Q

Blood Flow through Adult Heart

A

■ All venous blood arrives at sinus venosus, enters RA
■ Arterialized blood flows into LA
■ Both atria empty into one ventricle
■ Ventricular Systole: blood pumped into bulbus cordis

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8
Q

3 Main Arteries Off the Bulbus Cordis

A

○ Carotid: oxygenated blood flow to the head
○ Aorta: oxygenated blood flow to the body
○ Pulmocutaneous artery: mostly venous blood to the skin and lungs to pick up O2

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9
Q

How Continuous Ventricle in Amphibians Functionally Divided

A

slit-like trabercular meshwork
■ Keeps O2 blood on LEFT and venous (desat) blood on RIGHT - creates a laminar flow pattern to prevent mixing during contraction

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10
Q

Spiral Valve

A

in bulbus cordis; creates spiral streaming of blood flow
● Directs O2 blood to carotid and aorta
● Directs desat blood to pulmoncutaneous

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11
Q

Temperature Regulation in Amphibians

A

–Ectothermic, limited tolerance of temperature changes - affect metabolism, fluid regulation, activity levels

–Cooler temps vs reptiles: 24-27*C

–Ambient humidity >70%

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12
Q

Lymphatics in Amhibians

A

–High rate lymph production, circulation - drain fluid from tissues, return to circulation

–Includes lymph hearts

–Collects in SQ lymph sacs: indications of dz, fluid overload when enlarged

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13
Q

Lymph Hearts In Amphibians

A

■ At junctions of veins
■ Beat irregularly or synchronically at 50-60 bpm depending on fluid status of animal
■ Number present depends on species (Frogs, Salamanders (4-20); Ceacilians (100-200)
■ Preserve unidirectional flow of the lymph back to the heart
● Returns protein to circulation

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14
Q

Renal Portal System in Amphibians

A

○ Veins from the hind limbs unite with paired Jacobson’s veins
■ Flow through the kidney before entering postcaval vein

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15
Q

Hepatic Portal System

A

○ Flow from ventral abdominal vein through liver before entering postcaval vein back to heart
○ Renal and portals systems are found in anurans and salamanders
■ Not fully understood
■ May impact pharmacokinetics of drugs given in hindlimbs/tail (first pass effect)

Anesthetics are preferentially injected in front half of the animal

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16
Q

Vascular Access in Amphibians

A

○ Limited by size
■ Fine gauge needles/catheters (24 gauge or smaller)
■ Transillumination may help

○ Ventral abdominal vein
○ Femoral vein
○ Lingual vein
■ Lingual venous plexus on underside of tongues in anurans (frogs)
○ Tail vein (Caudatas - salamanders)
○ Axillary and stifle venous plexus

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17
Q

Respiration of Amphibians - Most Prominent

A

Pulmonic, cutaneous gas exchange and buccopharyngeal (gular/guttural) breathing
● Aquatic salamanders - gills
● Buccal and pharynx = extension of cutaneous respiration due to muscular pumping, unique vascular supply

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18
Q

Why Cutaneous Respiration Possible in Amphibians

A

Large surface area
Thin and semi-permeable epidermis
Highly vascularized dermis

Efficient form of respiration during anesthesia

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19
Q

Lung Structure In Amphibians

A

various shapes/sizes/simplicity
■ Range from sac-like (aquatic) to sacculated forms with alveoli in the anterior lung (terrestrial species)

Pulmonic epithelium
● Easily damaged by overventilation or ETT too far distal
● Endotracheal tubes placed just past larynx

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20
Q

Mode of Respiration in Amphibians

A

May change in various species depending on the oxygen and CO2 tension of the environment

Central respiratory drive to increase resp frequency or TV stimulated by decreased PO2 or increased PCO2

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21
Q

Important Considerations for Cutaneous Respiration in Amphibians

A

All adults utilize to varying degrees
○ Can account for significant portion of O2 exchange

Skin must be kept moist

Permeability of skin for gas exchange will vary by species (ex: Toads have <permeable due to thick skin)

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22
Q

Cutaneous System, Fluid Regulation

A

Important organ for immune function, water regulation
■ Evaporation major factor for water loss

Uptake of water through ventral surface
1. Drinking Patch
2. Small percentage of GI

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23
Q

Drinking Patch in Amphibians

A

functional structure on pelvis, contributes 80% of water uptake (frogs, toads)

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24
Q

GI Fluid Uptake in Amphibians

A

oral fluids less effective than keeping animal moist by soaking in an appropriate fluid (isotonic/hypotonic water

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25
Q

Osmolarity of Environmental Fluid and Fluid Uptake in Amphibians

A

Osmolarity of environmental fluid important: difference between external and plasma osmolality determines water regulation/movement
■ Change composition of plasma to tolerate fluctuations in water osmolality
■ Imbalance = fluid overload (kidney compromise)

High permeability allows absorption of exogenous compounds (drugs/toxin)

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26
Q

Physical Exam of Amphibians

A

–Occur prior to GA, detect abN that may increase risk
–Observe in enclosure: activity, demeanor, breathing pattern, hydration
–Gentle restraint to prevent escape, failing: brief, efficient stress free, safe
–Expect sudden bursts of activity to escape

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27
Q

Safe Handling of Amphibians

A

Premoistened Talc-free latex gloves: reduce risk of skin damage/transfer of pathogens/toxins btw handler, animal

+/- protective eye wear

Washed vinyl gloves for larvae

Water/fluid to moisten should be distilled, dechlorinated to prevent chlorine uptake - consider non-toxic, water soluble gel provides better protection for animals with sensitive skin

Some frogs/toads will bite; salamanders will drop tails

28
Q

Determination of Dehydration in Amphibians

A

Some species urinate when stressed
● Lack of behavior may indicate dehydration

Dehydration may present with skin tenting, sunken eyes, tacky skin, slow/decreased activity/mentation

29
Q

Hypocalcemia in Amphibians

A

Common Problem

Tetany, muscle fasciculations, paresis, GI stasis, bloating
■ Treated with calcium gluconate in a bath

Calcium readily absorbed through skin
■ Blood chemistry analysis performed after induction (minimize stress)

30
Q

Fasting in Amphibians

A

Not generally necessary: can maintain a closed larynx
○ Reserved for large species that eat rodent prey

24-48 hours prior to anesthesia to decrease risk of ileus and facilitate visualization during coelomic procedures

31
Q

Route of Administration of Anesthetics in Amphibians

A

TOPICAL

Drugs delivered in water, absorbed across gills or skin
–Inhalants can be administered topically or in solution
–Induction prolonged or unsuccessful if bubbled through water

Some species can be intubated awake and administered inhalants

32
Q

Unreliability of Injectable Drugs in Amphibians

A

■ Low margin of safety
■ Prolonged recovery
■ Doses species specific

33
Q

Considerations with Bath Solution Logistics in Amphibians

A

Bath solution for induction: dose dependent on surface area of animal
■ Ie. small patients may be exposed to more drug

Tank water from enclosure should be used
○ Reduces exposure to abrupt pH/temp changes
○ Can use bottled spring water at room temp
○ Can prepare “Amphibian Ringers” solution

Container used should be thoroughly cleaned and rinsed

34
Q

Cleaning the Solution Tank for Amphibians

A

Container used should be thoroughly cleaned and rinsed
○ Cleaning chemicals can be toxic if absorbed
○ Rinse well between patients due to secretions may be toxic

35
Q

Respiratory Ventilation During Ax in Amphibians

A

Reduced or absent during anesthesia
○ Cutaneous gas exchange may be low
○ Supplement oxygen to avoid hypoxemia and acidemia

36
Q

How Ventilate and Provide O2 to Amphibians

A

Supplement oxygen to avoid hypoxemia and acidemia
■ Bubble oxygen into water bath
■ Intubate to provide O2

IV catheters with adaptors, Cole tubes for larger species

Ventilate gently to avoid lung damage
● 5 cmH20, every 10 seconds

37
Q

Selection of Anesthetic Agents in Amphibians

A

○ Procedure to be performed
○ Level of immobilization required
○ Duration of anesthesia

38
Q

Skin Moisture in Amphibians

A

● Skin kept moist to prevent damage/dehydration, ensure dermal respiration maintained

39
Q

MS-222

A

Tricaine Methanesulfonate; Finquel®)

Most commonly used

Wide margin of safety; effective in all species, life stages

Requires buffering with sodium bicarbonate to pH 7.0-7.4 (highly acidic)

MOA: Sodium channel blocker, inhibiting nerve conduction
■ CNS depression

40
Q

Dehydration in Amphibians

A

Some species urinate when stressed: lack of behavior may indicate dehydration

Dehydration may present with skin tenting, sunken eyes, tacky skin, slow/decreased activity/mentation

41
Q

Clove Oil (eugenol, isoeugenol)

A

Administered via immersion
Species-specific different responses
Dosing difficult as concentration of eugenol may not be known

42
Q

Adverse Effects of Clove Oil in Amphibians

A

Commonly causes gastric prolapse due to pungent taste

cause renal tubular apoptosis
■ Hepatic necrosis, hemorrhage of coelomic fat bodies reported

cutaneous necrosis if applied directly to skin

43
Q

Inhalants - two methods for Admin in Amphibians

A
  1. Cutaneous Administration
  2. Bubbled through H2O
44
Q

Cutaneous Administration of Inhalant in Amphibians

A

(mixed with KY jelly)
■ Species-specific variability in effects

45
Q

MOA Clove Oil

A

MOA: local anesthetic
■ Blocks Na-Voltage gated channels and TRPV1
■ Activates inhibitory GABA receptors

46
Q

Bubble Through H2O with Inhalants with Amphibians

A

■ High exposure levels of waste gas - use a sealed container but makes handling difficult
■ Induction time = SLOW, recovery = RAPID once removed from bath

47
Q

Benzocaine in Amphibians

A

○ Needs to be dissolved in ethanol first
■ Final concentration should not exceed 1%

48
Q

Injectables in Amphibians

A

Propofol, ketamine, alfaxalone, 𝝰2-adrenergic agonists show wide species variability
■ Unpredictable inductions and recoveries
■ Undesirable mortality rates

49
Q

Propofol Immersion in Amphibians

A

○ Chemical restraint and sedation but not surgical anesthesia

50
Q

Do we usually premed amphibians?

A

not routinely performed
○ Administration of analgesic with/without sedative prior to induction may be beneficial in larger species

51
Q

Monitoring in Amphibians: HR

A

–Baseline HR obtained prior to anesthesia or immediately after induction to allow a trend to be formed
○ Relatively low heart rates (50bpm)
○ Visualization or with doppler probe at heart

–Good indicator about depth
–Sudden drop or slow decrease in time: increase in depth

ECG (avoid skin damage), Doppler, Visualization

52
Q

How to Change Depth with Amphibians

A

Change concentration of the bath

Syringes of premade solution (with and without anesthetic) can be used to deepen/lighten anesthesia as necessary by flushing over skin

53
Q

Stages of Anesthesia in Amphibians

A

Cessation of movement, righting reflex is first indication of induction

Light stage: loss of righting reflex, loss of abdominal breathing

Surgical depth: loss of withdrawal (with toepinch) and no gular respiration

54
Q

Other Features of Monitoring Amphibians

A

Pulse oximeter is not validated
○ Used to monitor trends

Provide thermal support, fluid uptake and analgesia

55
Q

Recovery of Amphibians

A

prolonged but usually smooth
○ Close monitoring to reduce complications
○ Phase of excitemen, erratic movements may be seen

Residual topical anesthetic rinsed off
○ Skin kept moist

Recovery on room air

56
Q

Recovery Process of Amphibians

A

Return of Withdrawal reflexes → increase in gular respiration → righting reflex → movement with improving coordination

57
Q

Recovery Process of Amphibians

A

● Recovery Process: Return of Withdrawal reflexes → increase in gular respiration → righting reflex → movement with improving coordination

58
Q

Analgesia in Amphibians - endogenous opioid system

A

–Well established, opioids effective analgesics

Dermorphin
Deltorphine

59
Q

Dermorphin

A

Potent amphibian-specific opioid compound found in skin of some SA frog species
■ 40x more potent than morphine
■ Potent 𝝻-agonist

DERMORPH = MORPH IN SKIN

60
Q

Deltaorphine

A

endogenous opioid peptide from skin
■ Potent 𝛅-receptor agonist
■ May play role in protection from predators/role in hibernation

61
Q

Nociceptive Pathways in Amphibians

A

Comparable to mammalian:
–Large and medium myelinated A-fibers, small myelinated B-fibers, small unmyelinated C-fibers
–Substance P, glutamate present in spinal cord

Peripheral sensitization to noxious stimuli can occur

Ascending pathways not fully understood

62
Q

Important Consideration with Analgesic Techniques in Amphibians

A

● Species-specific differences likely
○ Unable to extrapolate from one species to the next

63
Q

Opioids in Amphibians

A

dose-dependent effect
■ Receptor selectivity less than mammals
■ Relative potency mu > delta > kappa
■ Doses higher than mammals
● Onset to peak analgesic effect longer: >60’

64
Q

a2 R Agonists in Amphibians

A

○ Provides analgesia without sedation
■ Normal reflexes remain intact
○ Rapid onset, long lasting

65
Q

NSAIDS in Amphibians

A

○ Little data exists

Flunixin meglumine reported to provide analgesia
■ High dose required (25mg/kg)
■ One animal died, had evidence of renal congestion and inflammation

Meloxicam reduced circulating prostaglandins
■ No significant effect in analgesic trials

Indomethacin and ketorolac provided mild analgesia in two studies

Boards: Species (12 decks)

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