Environmental Emergencies Flashcards
Why does water decrease the body’s resistance to electrical flow?
- Due to Ohm’s Law (Q = P/R)
- Wet skin = less resistance = more damage
- Dry skin = more resistance = less damage
What does alternating current (AC) do to the body?
- Results in muscle tetany
- Muscles contract & patient is unable to let go
- Increases exposure time and overall injury
Which current is more severe, AC or DC?
AC. DC does not cause muscle contraction, meaning less exposure time
What is electroporation?
- The development of holes in the cellular membrane, cellular pore disruption. The holes allow the movement of larger molecules such as fluids or ions across the cellular membrane
- This causes excessive swelling or shrinking of cells, resulting in osmotic damage and cell death
What is thermal injury secondary to electrocution?
- Occurs when electrical energy turns into heat
- This increases the temp of the ICF & ECF
- This causes breakdown of tissue proteins which causes necrosis of the overheated tissue
What arrhythmia does AC cause?
Vfib - low voltage
What arrhythmia does DC cause?
Asystole - high voltage
What is a possible sequaela to electrocution?
Pulmonary edema, thought to be neurogenic
What height qualifies a high rise fall?
2 or more stories (20 feet)
High rise fall injury results from ___?
Vertical deceleration trauma
What is responsible for attempting to correct abnormal position while falling in cats?
The vestibular system
Why is it possible that cats may land on their side instead of their feet in a fall >7 stories?
Terminal velocity results in deactivation of the vestibular system
What is the pathophysiology of drowning?
Following submersion, a rise in CO2 levels in the bloodstream stimulates resps and water is absorbed
Aspiration of ____ml/kg of fluid leads to impaired gas exchange
1-3
Does sea water or fresh water lead to a more severe hypoxemia?
Sea water - hypertonic sea water aspiration leads to surfactant washout and diffusion of interstitial water into alveoli, thus preventng ventilation
How does fresh water drowning contribute to hypoxemia?
Pulmonary surfactant is diluted, leading to alveolar instability and collapse, which prevents normal ventilation of affected alveoli
Why does dry drowning sometimes lead to NCPE?
NCPE is likely secondary to intrathoracic pressure changes associated with continued respiratory effort in the presence of persistent laryngospasm
What is the diving reflex?
When the face hits water <41F, CNS activation from the trigeminal nerve will cause bradycardia and hypertension, resulting in shunting of blood to cerebral circulation
What are the 4 mechanisms of thermoregulation?
- Conduction (heat to surface)
- Convection (heat to air)
- Radiation (heat to objects not in contact)
- Evaporation (heat from moist surfaces)
What signs are seen at body temp of 90-99F?
- Vasoconstriction
- Ataxia
- Shivering
What signs are seen at body temp of 82-90F?
- Decreased LOC
- Hypotension
- May or may not be shivering (losing the ability to do so)
What signs are seen at body temp of 68-82F?
- Complete loss of shivering reflex
- +/- cardiac abnormalities
- +/- extreme CNS deficits
What signs are seen at body temp <68F?
- CV & CNS deficits
- Coag deficits leading to hypocoagulable state
What are the two types of hypothermia?
- Primary: heat loss in the face of normal heat production, encompassing environmental exposure. Unable to keep up with heat loss
- Secondary: result of dz process, drug administration (GA) or injury. Diseases can alter thermoregulation and increase/decrease metabolic rate
Anesthetic agents reset the T threshold needed to cause a ______?
Reflex vasoconstriction
If the ______has been reset, an animal may be intolerant of heat support even if clinically hypothermic
Temperature setpoint
What isotonic fluid should be avoided in severe hypothermia?
LRS, because lactate requires hepatic metabolism
Below ____F, heat loss increases and the patient becomes colder, faster
94F
Where are forced air warmers best placed?
On or near areas with a large blood supply such as the neck or abdomen
If using active internal rewarming, fluids should not exceed _____F to avoid damage to internal tissues
109.5F
Why should caution be excerised if infusing warm fluids via central line?
The resulting temp gradient at the heart may lead to irritability of the myocardium and cardiac arrhythmias
What is afterdrop?
- A decrease in patient temp AFTER warming has been instituted
- Occurs because the skin is warmed and vasoconstricted tissues begin to dilate, moving cold blood into the central vasculature
What is rewarming shock?
- Characterized by vasodilation as a result of applied heat
- Vasodilation has the potential to negatively impact organ perfusion and DO2 during rewarming
What body parts should external rewarming be focused on?
- Core. Avoid limbs
- This allows the vasculature to vasodilate slowly as warming progresses, allows CV system to adjust and avoids collapse
What biochemical changes will be seen in hypothermic patients?
- Metabolic acidosis which can continue to worsen as lactic acid is recruited from limbs and other hypoxic tissues
- Hyperkalemia as cellular K leaks out from damaged cellular membranes and in rewarming there is a shift of K from the intracellular to the extracellular space
What are the two most important fever producing cytokines?
- Interleukin 1& 6
- Tumor necrosis factor
How do NSAIDs bring down a fever?
- Pyrogens go to the anterior hypothalamus stimulating release of prostaglandins, causing an increase in temp
- NSAIDS inhibit prostaglandin synthesis
Why is fever beneficial?
It interferes with growth and reproduction of causative organism
Fevers >____F are considered life threatening
106
Why is actively cooling a patient with a fever detrimental?
- The body works harder to maintain its new set point
- If active cooling measures are suddenly removed, this can cause a patient to rebound to an even higher T
Why does humidity hinder heat dissipation?
Humidity reduces the evaporation of H2O, therefore the animal has to expend more energy to dissipate heat
Irreversible brain damage has been identified at _____F?
105.8
Why is hypoglycemia common in heat stroke?
Secondary to acute hepatic insult and increased metabolic demands
Convection, conduction, and radiation are passive cooling processes that are in effect until the ambient T >____F?
89.6F
Focused cooling efforts should be on what parts of the body?
Those with large blood vessels, such as the neck and inguinal area
At what temp should active cooling cease?
103-103.5F
Why should oxygen be provided to a heatstroke patient?
- Hyperthermia causes an increased O2 demand to the body because of increased metabolic activity
- Perfusion and oxygen delivery will be impaired due to metabolic shock
Which snake family can control the amount of toxin released?
Crotalidae
What animals appear resistance to snake venom?
- Pigs, likely due to slow absorption of venom from fat
- Cats, but become more critical patients because they antagonize the snake then hide afterwards
What is Antivenin?
- Fort Dodge
- Polyvalent equine origin
- Effective against numerous snake venoms
- Carries significant risk of anaphylaxis
What are the Fab antivenoms?
- Ovine IgG molecules are cleaved to discard inflammatory portion of antibody
- Much less likely to cause allergic reaction and more potent than equine origin
What is ACP antivenon?
- Boehringer Ingelheim
- Whole IgG, equine origin
A snake bite can be considered dry if no signs are seen after _____?
1 hour
What snake family “chews” to inject venom?
Corals - they have short, fixed front fangs and a relatively poor venom delivery system
How do the hemotoxic venoms exert their effect?
- The proteins break down tissue and allow penetration of venom into patient’s systemic circulation
- It destroys RBC, inhibits coagulation, breaks down fibrinogen proteins
- Destroys vascular walls, which allows leakage of RBC and plasma into extravascular spaces
How can the venomous coral snakes be distinguished from non venemous?
“Red on yellow, kill a fellow. Red on black, venom lack”
How does neurotoxic venom exert its effect?
- Neurotoxic venom is chemically similar to non depolarizing neuromuscular blocking agents
- Mixture of polypeptides including cholinesterase & acetylcholine
- This nondepolarizing blocking of acetylcholine receptor sites has a slow onset and markedly prolonged duration
- Clinical signs: muscle fasciculations, spasms, paralysis, resp failure
What is the origin of coral snake antivenom?
Equine antibodies
Black widow snakes reside in every state except for?
Alaska
Which species is extremely susceptible to black widow bites?
Cats - painful vocalization can progress to ataxia and paralytic signs +/- death
What are the clinical signs of black widow bites?
- Nearly painless bite followed by severe pain
- Can see muscle spasms, cramping, and abdo rigidity are thought to be due to massive release of neurotransmitters
What type of toxin does the black widow spider have?
A potent neurotoxin, alpha latroxin, that initially stimualtes secretion of neurotransmitters, then inhibits uptake
Black widow bite treatment
- Calcium gluconate lessens signs, but antivenom is highly effective in cats.
- Antivenom: Derived from horse serum, standardized by a biologic assay in mice, and
administered intravenously. Rapid reversal of symptoms noted within hours - Supportive therapies: Morphine, barbiturates, and glucocorticoids
What spider species has a violin shaped icon on dorsum?
Brown spider
What effect does brown spider venom have?
Highly toxic to tissues by interfering with leukocytes and causing dermal necrosis
- Renal injury can result from the Loxosceles toxins binding to glomerular and tubule cells
Is there antivenom available for brown spider bites?
No
Do spider bites cause infection or transmit communicable disease?
No
What spider bite causes a bullseye/target sign?
Brown spider
What scorpion is of concern to companion animals?
Bark scorpion (Centruroides exilicauda)
What effect does bark scorpion venom have?
Blocks voltage-gated potassium and sodium channels; causes systemic symptoms like nystagmus, paraesthesia, excessive salivation, tachycardia, and myoclonus.
What is the treatment for bark scorpion bites?
- Symptomatic care includes high doses of benzodiazepines and opioids.
- Anascorp antivenom, derived from horse plasma, neutralizes venom toxins but has no veterinary literature on its use in animals
