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Boards: Species > Fish > Flashcards

Fish Flashcards

1
Q

General Features of Fish Anesthesia

A

Differences in water temp, water quality/salinity, behavior, response to drugs
○ Make anesthesia challenging

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2
Q

Gills

A

■ Located behind head in buccal cavity
■ Covered by a sturdy flap (operculum in bony fish)
■ Consists of gill arch, a filament, comprehensive vascular system

Highly folded, highly vascular thin membranes for GE

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3
Q

Vascular Anatomy of Gills

A

Branchial basket arising from aorta, gives rise to afferent filament arteries that supply filament

Afferent filament arteries give rise to afferent lamellar arterioles that supply lamina

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4
Q

Blood Gases Exchanged in Lamina DT

A

○ Maximal surface area contact
○ Changes in blood flow
○ Velocity
○ Optimal O2 gradient tensions

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5
Q

How blood gets from gills back to dorsal aorta

A

Efferent lamellar arterioles in lamine –> efferent filament arteries –> efferent branchial arteries –> dorsal aorta

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6
Q

Arterio-arterial circulation

A

Countercurrent system to optimize oxygen uptake

Venous blood moves in the opposite direction to the water

Creates a favorable gradient between the oxygen in the blood and water to maximize uptake

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7
Q

Movement of Water Over Gills

A

Fish draws water into mouth → water pushed out over gills by closing mouth, opening gill cover

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8
Q

Ram Ventilation

A

Some species force water over gills at varying degrees to achieve more efficient ventilation

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9
Q

Additional Functions of Gills

A

■ Osmoregulation
■ Nitrogen excretion
■ Hormone metabolism
■ Acid-base regulation

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10
Q

Aquatic Surface Respiration (ASR)

A

Position mouths to skim air/water interface that is richer in oxygen

Response to hypoxic conditions include developing temporary dermal swellings of lower jaw to facilitate ASR

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11
Q

Lung Fish

A

possess true lungs with ventrally situated pneumatic duct openings in alimentary canal instead of traditional gas/”swim” bladder

Obligate air breathers

Will alter ventilation to compensate for metabolic acid-base changes

Theoretically possible to cannulate pneumatic duct to administer inhalants
● Challenging and done only experimentally

Some species if placed in immersion bath, will attempt to breath air and not respire with gills (Australian Lungfish)

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12
Q

Basic CV Structure of Fish

A

Single-cycle, closed-loop system

■ 2-chambered heart (or “4-chambered heart arranged in series”) pumps blood in a single circuit through body, picks up oxygen on way through gills

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13
Q

Parts of Fish Heart

A

■ Sinus venosus
■ Single atrium
■ Single ventricle
■ Bulbus arteriosus

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14
Q

Blood Flow through Fish

A

Single-chambered ventricle → bulbus arteriosus (through pair of ventricular-bulbar valves) → aorta → gills for oxygenation then to body → dorsal aorta then to tissues with hepatic and common cardinal veins (blood from body) → sinus venosus

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15
Q

Bulbus Arteriosus

A

non-contractile but elastic, resembles bulge at base of aorta

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16
Q

Conus Arteriosis

A

Bulbus arteriosus in sharks
● Contractile cardiac muscle fibers and rows of valves

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17
Q

Sinus Venosus in Fish

A

sac-like contractile structure

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18
Q

Role of Cardiac Valves in Fish

A

ensure unidirectional blood flow

SA valve btw Sinus Venosus
AV valve btw Atrium, Ventricle
Ventricular Bulbar Valve btw Ventricle and BA

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19
Q

ECG in Fish (precordial leads)

A

■ Pwave: onset of atrial (auricular) contraction
■ QRS: invasion of ventricle
● P-R interval: time for impulse to cross atrium, AV junction
■ T wave: repolarization of the ventricle

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20
Q

Branchiocardiac Reflex in Fish

A

Increasing HR with increasing RR to ensure optimal oxygen uptake

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21
Q

Baroreceptor Reflex in Fish

A

slows heart rate when arterial blood pressure increases

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22
Q

“Buccal flow/heart rate reflex”

A

Increased heart rate with increased water flow through the buccal cavity

Can be achieved by moving fish through the water/flowing water through the buccal cavity

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23
Q

Nervous System in Fish

A

PNS and CNS
■ PNS divided into somatic (motor, sensory) and autonomic division
■ Autonomic: sympathetic, parasympathetic, enteric nervous system

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24
Q

CNS in Fish

A

Include spinal cord, brain stem (medulla oblongata, telencephalon, diencephalon, mesencephalon, cerebellum)

Diencephalon - epithalamus, thalamus, hypothalamus

Fish have an archipallium (olfactory part of cerebral cortex)

Lack neopallium in cerebrum (cognition, spatial reasoning, higher centers in mammals)

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25
Q

Fish and Stress

A

Fish are easily stressed: results in high morbidity and mortality

Include:
● Changes in water quality (temp, pH, nitrogenous waste)
● Handling
● Transportation
● Disease
● Noise
● Light abnormalities
● Inadequate nutrition
● Stocking, etc

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26
Q

How Fish Respond to Stress

A

a neuroendocrine response that includes adrenergic system, the hypothalamic-pituitary-interrenal (HPI) axis
● Factors and neurotransmitters:
○ Adrenocorticotropic hormone
○ Catecholamines

27
Q

What are the three stages of stress response in fish?

A
  1. Primary
  2. Secondary
  3. Tertiary
28
Q

Primary Stress Response in Fish

A

fight or flight response through catecholamine release

29
Q

Secondary Stress Response in Fish

A

increase in CO, metabolic rate, respiration, lactic acid and fatty acids

30
Q

Tertiary Stress Response in Fish

A

physiological exhaustion, decreased immune function and reproduction, growth rate, changes in behavior, increased mortality

31
Q

Role of Chemical Sedation, Anesthesia in Fish

A

result in lower stress response when compared to drug-free handling and transport
● Lowered circulating cortisol levels
● Secondary indicators: blood glucose, HCT, HgB, lactate, osmolarity

32
Q

Which agent consistently and significantly blocks HPI response in fish?

A

metomidate

33
Q

Lateral Line System

A

allows fish to determine direction, rate of water movement.

Gain a sense of own movement, that of nearby predators or prey, even water displacement of stationary objects

34
Q

Nociception

A

■ Signals travel via peripheral nerves
● C- or A-𝛅 fibers depending on species and pain stimulus
■ Sent via the spinothalamic and trigeminal tracts to the brain
■ Functional endogenous opioid system: all 4 receptors identified

35
Q

Thermoregulation

A

Ectothermic

Induction, recovery prolonged in lower temps due to decreased respiratory rates and CO, lowered metabolism

Acidosis and hypercapnia occur at higher temps
● Leads to hyperventilation, decreased induction/recovery times

36
Q

Thermoregulation in Tuna, Some Sharks

A

developed ability of endothermy by conserving heat, increasing body temp
■ Conserve heat in slow-twitch muscle, viscera, brain and eyes
■ Endothermy leads to increased rate of anesthetic uptake and metabolism

37
Q

MsK System

A

All teleost fish: anatomic separation between aerobic, slow-oxidative muscles (red muscle) and anaerobic, fast-twitch glycolytic muscle (white muscle)

Distinct pattern of highly oxygenated, slow oxidative muscle runs along midline of body
● Increased capillarization
● Injection of anesthetic agents into region may result in more rapid induction times

Thin, large variations in thickness and location
● Consistent injection difficult

38
Q

Vascular Access in Fish

A
  • Ventral tail vein
    -Cardiac puncture - behind operculum, ventral through body wall
    -Doral aorta through mouth
    -Periorbital Sinus through mouth

Catheterization not routine, impossible to maintain

May need spinal needles DT depth of vessel

39
Q

Fasting in Fish

A

Fasting fish for 12-24 hours recommended to reduce the amount of nitrogenous waste production
■ High levels may decrease oxygenation, lead to acidemia and methemoglobinemia
● May affect uptake and metabolism of anesthetic agents

Reduced risk of regurgitation that may obstruct the gills

40
Q

Consequences of Regurgitation in Fish

A

Fine regurgitant can cover gill lamellae and result in suffocation (sestonosis)

41
Q

Other Considerations with Fish

A

–Baseline behavior parameters
–Containers with adequate H2O for transport, induction, maintenance, recovery
–H2O: similar to normal environment - temp, pH, salinity
–Maintain moisture of skin, fins, eyes if out of water procedure

42
Q

Size of Fish and Drugs

A

■ Bigger fish need less drug per unit weight

43
Q

Tricaine Methanesulfonate (MS-222) (Fish)

A

Local anesthetic - blocks voltage–gated sodium channels

Peripheral, central effect by blocking Na, K, Ca channels
○ Activation of secondary messenger via membrane-bound protein activation

Muscle relaxation, sedation, CV+Resp depression occur in dose-dependent manner

44
Q

Metabolism of MS-222

A

Rapidly biotransformed via acetylation (polar, non-polar metabolites)

Excreted via gills and kidney, bile

45
Q

Other Features of MS-222

A

Buffer required to maintain optimal water pH

Salt water = natural buffering capacity

Only FDA approved drug, withdrawal time: 21 days

46
Q

Benzocaine in Fish

A

● Local anesthetic
● Parent compound to MS-222
● Dissolving in organic solvent required (ethanol/acetone)

47
Q

Metomidate

A

Non-barbiturate hypnotic

MOA: GABAA receptors

Decreased cortisol release by blocking HPI axis in fish

Administration by immersion or oral

48
Q

Isoeugenol (Clove oil/Aqui-S™)

A

Associated with CV/Resp depression, stress response

Potential carcinogenic properties

49
Q

2-phenoxyethanol

A

● Used primarily for sedation for transport
● No pH change in water
● Hypoventilation and poor analgesia

50
Q

Quinaldine

A

● Strong acid - must be buffered
● Provided as stock solution (10g/L)
● High lipid solubility, will accumulate in brain
● NOT approved for use in US, common elsewhere due to low cost
● Effective, low toxicity, wide safety margin, short recovery time

51
Q

Key Features of Immersion Drugs in Fish

A
51
Q

Key Features of Immersion Drugs in Fish

A

water soluble or utilize water-soluble solvent

Can also use iso via immersion

52
Q

Parenteral Anesthetics in Fish

A

oral, IV, IM and intracoelomically (ICe)

Similar to other species:
–Prolonged recovery, excitement with ketamine
–Positive chronotropic, inotropic with alfax
–Resp depression with propofol
–Telazol: mortalities

53
Q

Which parenteral route is most common in fish and where is it located?

A

IM route most common: Dorsal saddle area, located around dorsal fin

Problems include:
○ Unreliable response, prolonged recovery, need for ventilatory support
○ Influenced by patient status

54
Q

Intracoelomic Route in Fish

A

Increased risk of visceral damage

Drugs may pass through serosal surface - erratic induction times

55
Q

Adjunctive Agents in Fish

A

Benzodiazepines, opioids, NSAIDs

Morphine used as analgesic - long DOA

Butorphanol, buprenorphine limited analgesic effects

56
Q

Non-Chemical Anesthesia in Fish

A

Electroshock - common in fisheries for group immobilization
● Severe muscle tetany and injuries

Hypothermia used but has too many deleterious effects to be considered

57
Q

Anesthesia Flow By Technique in Fish

A

Induction by immersion

Removed from water, placed on elevated foam holder/padded fenestrated shelf inside a container which can collect circulated water

Buccal cavity intubated with bifurcated plastic tube, connected to a non-recirculating or recirculating system (dependent on fish size)
● Supplies aerated water containing anesthetics
● Re-circulating systems reuse the collected water via pump or manually with syringe

58
Q

Flow Rates for Immersion Systems in Fish

A

(influenced by drug concentration): 1-3L/kg/min
● Assures gills remain wet for gas exchange
● Prevents gastric dilation

59
Q

Monitoring of Ax Depth in Fish

A

■ Assessing muscle relaxation, Jaw tone, body muscle tone
■ Heart rate, respiratory rate
■ Evaluating loss of righting reflex
■ Responsiveness to stimuli

60
Q

Stages of Ax in Fish - sx ax

A

loss of equilibrium, loss of reaction to pressure on the peduncle, loss of reaction to emersion with no activity and relaxed muscles

2-5 operculum movements/min

61
Q

Observation of Heart Beat in Fish

A

Heart beats can be visualized or use of a doppler probe/ECG
■ Doppler placed directly over heart or into opercular slit
■ ECG clips on fins (via hypodermic needles)

Electrode patches not recommended DT concern for skin damage

If CO is adequate, flow-by water through gills provide adequate gas exchange
■ Recommended to decrease anesthetic concentration

62
Q

Recovery in Fish

A

If fish has strong pulses, ventilating well - can be placed in a dedicated aerated recovery tank void of any anesthetics

Fish is held upright and moved through water to provide flow of oxygenated water through the gills for washout

Gradual return of reflexes and coordinated movement
■ Continual monitoring to prevent injury

63
Q

Recovery in Fish that Ram ventilate

A

sufficient water flow by pump required

Boards: Species (12 decks)

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