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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
Fish and Stress
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
26
How Fish Respond to Stress
a **neuroendocrine response** that includes **adrenergic system, the hypothalamic-pituitary-interrenal (HPI) axis** ● Factors and neurotransmitters: ○ Adrenocorticotropic hormone ○ Catecholamines
27
What are the three stages of stress response in fish?
1. Primary 2. Secondary 3. Tertiary
28
Primary Stress Response in Fish
fight or flight response through catecholamine release
29
Secondary Stress Response in Fish
increase in CO, metabolic rate, respiration, lactic acid and fatty acids
30
Tertiary Stress Response in Fish
physiological exhaustion, decreased immune function and reproduction, growth rate, changes in behavior, increased mortality
31
Role of Chemical Sedation, Anesthesia in Fish
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
Which agent consistently and significantly blocks HPI response in fish?
metomidate
33
Lateral Line System
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
Nociception
■ 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
Thermoregulation
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
Thermoregulation in Tuna, Some Sharks
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
MsK System
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
Vascular Access in Fish
- 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
Fasting in Fish
**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
Consequences of Regurgitation in Fish
Fine regurgitant can cover gill lamellae and result in suffocation (sestonosis)
41
Other Considerations with Fish
--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
Size of Fish and Drugs
■ Bigger fish need less drug per unit weight
43
Tricaine Methanesulfonate (MS-222) (Fish)
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
Metabolism of MS-222
Rapidly biotransformed via acetylation (polar, non-polar metabolites) Excreted via gills and kidney, bile
45
Other Features of MS-222
Buffer required to maintain optimal water pH Salt water = natural buffering capacity Only FDA approved drug, withdrawal time: 21 days
46
Benzocaine in Fish
● Local anesthetic ● Parent compound to MS-222 ● Dissolving in organic solvent required (ethanol/acetone)
47
Metomidate
Non-barbiturate hypnotic MOA: GABAA receptors Decreased cortisol release by blocking HPI axis in fish Administration by immersion or oral
48
Isoeugenol (Clove oil/Aqui-S™)
Associated with CV/Resp depression, stress response Potential carcinogenic properties
49
2-phenoxyethanol
● Used primarily for sedation for transport ● No pH change in water ● Hypoventilation and poor analgesia
50
Quinaldine
● 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
Key Features of Immersion Drugs in Fish
51
Key Features of Immersion Drugs in Fish
water soluble or utilize water-soluble solvent Can also use iso via immersion
52
Parenteral Anesthetics in Fish
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
Which parenteral route is most common in fish and where is it located?
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
Intracoelomic Route in Fish
Increased risk of visceral damage Drugs may pass through serosal surface - erratic induction times
55
Adjunctive Agents in Fish
Benzodiazepines, opioids, NSAIDs Morphine used as analgesic - long DOA Butorphanol, buprenorphine limited analgesic effects
56
Non-Chemical Anesthesia in Fish
Electroshock - common in fisheries for group immobilization ● Severe muscle tetany and injuries Hypothermia used but has too many deleterious effects to be considered
57
Anesthesia Flow By Technique in Fish
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
Flow Rates for Immersion Systems in Fish
(influenced by drug concentration): 1-3L/kg/min ● Assures gills remain wet for gas exchange ● Prevents gastric dilation
59
Monitoring of Ax Depth in Fish
■ Assessing muscle relaxation, Jaw tone, body muscle tone ■ Heart rate, respiratory rate ■ Evaluating loss of righting reflex ■ Responsiveness to stimuli
60
Stages of Ax in Fish - sx ax
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
Observation of Heart Beat in Fish
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
Recovery in Fish
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
Recovery in Fish that Ram ventilate
sufficient water flow by pump required

Boards: Species (12 decks)

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