Aquatics Flashcards
General Considerations for Aquatic Mammals
Drug Delivery = difficult
Cold, aquatic environment - fur coats, thick blubber, or fat layers for insulation
IV Access very limited, even if immobilized or anesthetized
General Pulmonary System of Aquatics
Pulmonary systems highly developed to facilitate rapid oxygen, carbon dioxide exchange
Short upper airways with extensive cartilaginous support down to small bronchioles
Take large breaths (tidal volumes) –> aids in rapid gas exchange
Dive Reflex - Summary
breath holding (apnea), decreased heart rate, shunting of blood to critical aerobic organs
Breathing Pattern Generator in Aquatics
Higher centers in brain modulate central rhythm generator both positively, negatively breathing
During episodic breathing, modulating influences alternate: periods of apnea alternating with periods of relatively high frequency ventilation
How Aquatic Peripheral Tissue Changes during Dives
Reduce metabolic functions or
Function by hypoxic or anaerobic pathways
Implications of Metabolic Changes During a Dive
Absorption of anesthetic can be unpredictable or slower if CNS depressants administered IM during breath holding or during activation of dive reflex
Once breathing initiated, blood flows to the periphery
Darting or drug administration should occur during active ventilation, avoided during apnea
When should you dart an aquatic animal?
- Active ventilation/avoided during apnea
- Mammals should not be darted with anesthetic while in aquatic environment
o Can dive out of sight, drown
Blowhole
modified nasal orifice (blowhole)
Closed by muscular nasal plug when underwater
Opens through action of forehead muscles
Divided by septum for 10-12cm
Aryteneoepiglottic Tube
Giving direct opening from internal nares to lungs
Enable animal to breathe only through blowhole
Aryteneoepiglottic Tube
giving direct opening from internal nares to lungs
Enable animal to breathe only through blowhole
Distal Airway in a Porpoise
10 cm from base of larynx, trachea branches into separate right bronchus
15 cm, bifurcates into two main bronchi
When intubated, do not extend tube into bronchus ie do not pass tube >10cm
Respiratory Pattern in a Porpoise
one full respiration in 0.3s
VT 5-10 L –> flow rates through air passages range from 30-70 L/s during expiration, inspiration
RR 2-3bpm, each breath is deep (~80% tidal air)
After inspiration, animal holds an apneustic plateau for 20-30s then rapid exhalation, inspiration
Bradycardia in Porpoises
frequently observed during anesthesia
Preanesthetic treatment with anticholinergics is recommended
IV or IM dose of atropine = 0.02 mg/kg
May be from strong PSNS stimulation or effects of sedatives or analgesics
Sedation of Porpoises
meperidine =0.2 mg/kg IM in cetaceans - meperidine provides moderate restraint in cetaceans without deleterious effects +/- BZD
Orotracheal Intubation of Porpoises
Can be intubated while awake, easier after sedation or induction of unconsciousness
Relatively large airways (24-30 mm) ET tube
Cuff inflated
Process of Orotracheal Intubation in Porpoises
Mouth held open with towels by assistant
Hand inserted into pharynx and grasps, pulls larynx anteroventrally from normal intranarial position
Digital intubation similar to cattle: ET tube guided into trachea by inserting 2 fingers into glottis, passing tube along palm of hand
Other Forms of Intubation in Porpoises
Blowhole intubation described in smaller cetaceans
Maintenance of Anesthesia in Porpoises
Require IPPV
Inhalants > TIVA
IV Access in a Purpoise
tail fluke veins
Drug Sensitivities in a Porpoise
Sensitivity to barbiturates: respiratory failure, death - no longer recommended
Plasma cholinesterase extremely low or absent in bottlenose dolphins, use of succinylcholine to induce muscular paralysis not recommended
Porpoise Parameters under GA
o HR 100-120 bpm
o On 100% O2: arterial pH averages 7.35, PaO2 100-200 mmHg, PaCO2 35-50 mmHg
o Room air, conscious: arterial PaO2 65-98 mmHg, PaCO2, ranges 40-60 mmHg
Monitoring of Depth in Porpoises
Cessation of tail-fluke movements = surgical anesthesia
Occurs after loss of strong corneal and eyelid reflexes
Swimming reflex = best criterion for assessing depth
Other Reflexes of Depth in Porpoises
–Palpebral
–Corneal
–Swallowing with pharyngeal stimulation
–Body movements with anus distention
–Tail Movements
–Pectoral flipper movement IRT surface stimulation
–Movement of blowhole after stimulation of nares, vestibular sacs
–Vaginal or penile movement when manipulated
Extubation of Porpoises
ET tube kept in place until blowhole reflex returns
Usually 15-45 min after cessation of inhalant administration
Timing removal of ET tube critical
Only after animal capable of breathing on own = movements of blowhole/thorax, struggling, coughing, or bucking
o ET tube removed, larynx must be placed in its normal intranarial position
If animal does not exhale through blowhole within 3 min or HR <60bpm, re-intubate and ventilate for a few minutes
Porpoise Recovery
near neutral in buoyancy
o Out of water = more difficult for them to breath and maintain circulation
o Returned to water ASAP post recovery
Analgesia in Porpoises
Local anesthesia: analgesia for minor painful procedures
o Toxic doses of various LAs not established, use smallest dose possible
NSAIDS: carprofen, flunixin – gastric ulcers common
Toothed, Baleen Whales
- Chemical immobilization, anesthesia attempted in large cetaceans
- Killer whales: sedated with meperidine, midazolam for minor procedures
Anesthesia, sedation generally not successful
Mortality in California Sea Lions
Perianesthetic mortality of California sea lions under ax = 3.4%, within 72hr post up to 4.3%
Respiratory System of Eared Seals, Walruses, True Seals
Highly efficient respiratory systems
o Alveolar exchange in seals measured at ~46% vs terrestrial mammals only 12-16%
Induction of Eared Seals, Walruses, True Seals
In species that can be physically restrained or sedated with BZD tranquilizers (diazepam/midazolam 0.1 mg/kg IM), induction with gas anesthetics recommended
o Mask inductions can be very fast, as little as 3-4bpm
o High alveolar exchange, low solubility
- Respiratory monitoring important: ETCO2
- Injectable anesthetic drug elimination = more variable
Monitoring in Seals, Walruses
Temperature closely monitored via esophageal or rectal probe
o Hyperthermia/hypothermia can occur during physical restraint, sedation, anesthesia, handling outside normal aquatic environment
Doppler flow detector: important tool in assessing peripheral perfusion
Walruses
High mortality rates with opioids, DA
o Most likely from severe respiratory, circulatory compromise when animals out of water
o Respiratory arrest common with potent opioids, even +ventilatory support
Potential Protocol for Walruses
midazolam 0.1 mg/kg, meperidine 2.2 mg/kg
o Prevent vagal induced bradycardia atropine 0.04 mg/kg
Drug Access in Walruses
- IM - hip, epaxial muscles, long needle 3-4 inches
- IV - epidural venous sinus
- ETT for emergency drugs
IV Access in Walruses: epidural venous sinus
Place like epidural needle: sternal recumbency, wings of ileums can be palpated
Needle perpendicular to skin
Large walruses: 6 inch spinal
Epidural IV for fluids, emergency drugs, anesthetics: small boluses of propofol (40-60 mg) used to relax muscle
Maintenance and Intubation of Walruses
Onset of immobilization, HR 80-100 bpm – slows to 60 as anesthesia depends
Apnea common: prove ventilatory support
Intubation easiest in sternal with head extended
Small oral cavities
Digital palpation of the larynx, direct placement of ET tube possible once animal relaxed, mouth pulled open by assistant
Oxygen flow rates, vaporizer settings similar to equine: minimum flow 4 L/min
Immobilization of Southern Elephant Seals
seals generally lethargic
o Injected close range with pole syringe, 16-18g needle up to 4 inches in length
Drugs Used in Seals
- Concern for excessive salivation with ketamine
- Succinylcholine (2.5 mg/kg) has been used to immobilize seals rapidly
Must be used with concurrent analgesic or anesthetic drug administration, ventilatory support - Medetomidine, consider reversal with atipamezole
IV Access in Seals
Restrained in squeeze cage to access flipper, vein in ventral aspect of flipper
~3 cm anterior to its posterior for IV administration
Meperidine in Sea Lions
provides little restraint of sea lions, causing profound respiratory depression
o Low dosages or avoid in sea lions
Induction/Maintenance of Seal Lions
Sea lions can hold their breath for as long as 5 min
When breathe, intake = enormous, rapid
Respiratory pattern during induction not accurate gauge of CNS depression
Post induction, trachea is easily intubated for further inhalant, 0.75-1.5% halo/iso usually sufficient to maintain anesthesia
telazol in sea lions
Telazol >2.5 mg/kg IM can be fatal in sea lions, hypothermia is commonly observed
Apneustic breathing seen post telazol, use doxapram
Safe, effective doses: 0.5-1mg/kg +/- ketamine
Manatees
Many minor procedures can be performed with proper physical restraint
Local infusion for painful procedures
Positioning of Manatees
Maintain in sternal if sedated or awake (restrained)
Tail is potentially dangerous if in dorsal or lateral recumbency
Tail can be restrained by assistants, foam pads
Potential Drug Combinations in Manatees
Sedation: midazolam 0.045 mg/kg IM
Light GA: restraint midazolam 0.066 mg/kg IM + meperidine (up to 1 mg/kg IM)
o Flumazenil, naloxone = effective antagonist
Nasotracheal intubation easily accomplished with fiberoptic endoscope
o Scope in one nares, tube in opposite nasal passages
o PPV recommended, iso maintenance 1.5-2.5%
Best sites for IM Injection in Polar Bears
shoulder, neck = best sites for IM
Considerations for Polar Bears
- Potent drug combinations
- Positioning: avoid excessive pressure on limb m - swelling, lameness
- Hypometabolic state in the summer
- reversible protocol
Summer State of Polar Bears
hypometabolic state
Characterized by fasting, decreased body temp (93-95 F)
IM mobilizing drug requirements may also be decreased
Importance of Reversible Protocol in Polar Bears
Areas where lots of polar bears congregate: important due to risk of predation, also important for mom with cubs
Immobilized with Telazol, typically keep their heads out of water better than bears immobilized with opioids
Probably due to muscle extension with use of DA vs relaxed curled body position with use of carfentanil or etorphine
Drug Administration and Safety in Polar Bears
Mature bears: darted with 22 caliber blank powered projectors, explosive discharge darts
Needle up to 10 cm in length necessary to ensure the IM injection
Polar bears notorious for pretending to be immobilized, awaken suddenly
Polar Bear Transport
Suspension in a cargo net for recovery can cause acute hypertension (up to 50% increase in MAP), hypoxemia, evidence of stress
Cargo net can restrict ventilation and circulation
Should be transported on rigid platform
Opioids in Polar Bears
Fentanyl, carfentanil, etorphine all used to immobilize polar bears
o Fentanyl IM 0.44 mg/kg, volume needed is too high for adult bears
o Fentanyl reportedly provides better muscle relaxation than etorphine
o Naloxone 25 mg to 10 mg of fent, 25 mg per 0.5 mg of etorphine for rapid reversal
Sea Otter Protocol
Most effective combo = fentanyl 0.05-0.1 mg/kg + ACP or DZP (0.1-0.22 mg/kg IM)
Capture, Restraint of Seanotters
Manual restraint, nets often effective for capture and examination
o Hand injection used in these situations
o If restraint possible, mask induction with sevo/iso works well
Transport of Sea Otters
body temp to increase during capture
o Transported in well-ventilated cages that are iced to help keep animals cool
