Transcript Mammalian Injuries

Mammalian Injuries
Wilderness Medical Consortium
Matthew Sholl
Outline
General comments
Frequency of mammalian injuries
Etiology of an injury
General approach to mammalian injuries
Bite characteristics
To Close or Not To Close
Injury patterns based on species
Infectious patterns based on species
Species
Bear
Large Cats
Mountain
Lions/cougars
Large Herbivores
Deer - MVA’s
Moose - Trampling
Bull - Gorings
Exotic Pets
Chimps and
monkeys
Lions and Tigers
Small Rodents
Rats and Mice
Skunks, Foxes,
Raccoons
Bats
General Comments
Human injuries from wild mammals rare
Usually due to humans ignoring obvious
signals from the animal
Most animals attack as last resort when all other
signals have failed

Animals in nature have adapted intricate signals to avoid
violent encounters
Route cause of many bites:
Human intrusion on animal’s territory
Interruption of mating activities
Female with young
Incidence of Mammalian Injury
Wild animal injuries are rare in comparison to
domestic animal injuries, insect injuries or
vector borne diseases
Several thousand deaths/year due to wild animals
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Most are due to man-eating lions and tigers in Africa and
Asia
60,000 deaths/year due to snakes
Millions of deaths/year due to insects
Greater than 3 million visitors/year to
Yellowstone Nat Park
Incidence of animal injuries less than lightning
strikes
Injuries in the US
200 US deaths/year due to animals
131 deaths from deer/moose traffic accidents
43 deaths from hymenoptera envenomation
14 deaths from dog bites
10 deaths from rattlesnake envenomation
Freer, L “North American Wild Mammalian Injuries” Emerg Med Clinics of No Amer, May 2004
When Injuries Do Occur…
Often devastating due to :
Size and weight of animal
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Moose routinely weigh > 1000 lbs
Animal’s strength…
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Dog’s bite strength approximately 200 psi
• Six times that of a human
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Wolves can tear steal bowls with teeth
Hyenas can bite through 2 inch planks
4 men needed to subdue a chimpanzee
Orangutan can maintain a 1 fingered grip unbreakable by
humans
Evaluation of the Injured
Size, weight and strength of animals are
augmented by sharp claws, large teeth and
horns
Combination of penetrating and blunt injuries
These structures may cause occult deep
tissue damage to any structure
Multiple examples of small appearing external
wounds with devastating internal injuries
All patients deserve aggressive work up and
evaluation for occult injuries
Especially to neuro/vascular structures
Evaluation, continued
Evaluation of animal injuries challenging:
Risk of blunt injury - trampling, throwing
Risk of penetrating injury - goring, biting
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External wound may belie the patient’s underlying
injuries
Risk of infection generally higher than standard
wounds
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Contaminates from saliva, nasal secretions, soil
Penetrating and puncture wounds
Many injuries occur in remote areas removed from
medical care
In Field Evaluation
Due to the remote location in which
many injuries occur as well as the
increased risk of infection due to biting
or puncture wounds, treatment MUST
begin at the site at which a bite occurs
Initial measures should include:
Resuscitative efforts
Local wound care
Local Wound Care
Animal bites, gorings or wounds from claws
are not clear injuries
Often involve some degree of crush injury along
with contaminants
Debridement better than irrigation in
removing dead/devitalized material, clot, soil
and other contaminates
May be difficult if no local anesthetic or pain
medications available
Local Wound Care, continued
After debridement of dead/devitalized
tissue, initiate irrigation
Removes all remaining debris
Potable water as minimum
1% provodone/iodine preferable due to
bactericidal and viricidal properties
Irrigate with large volumes of solute
100 - 300 cc per cm
Risk of Infections
Most bites do NOT become infected
Many bites or injuries result in contusions
only with no deep penetration through the
skin
BUT certain characteristics place a
wound at risk for infections….
Risk Factors for Infection from
Animal Injuries/Bites
From Freer, L “Bites and Injuries Inflicted by Wild Animals”, pg 984 Wilderness Medicine 2001
“To Close Or Not To Close That Is The Question”
Decision based on three factors:
Cosmetic Appearance
Function
Risk of Infection
Cosmetic appearance virtually mandates
closure of facial wounds as well as other
highly visible areas
Low risk of infection
Function of hands and feet is highly critical
but in balance, closure is NOT recommended
due to risk of infection
The Decision to Perform
Primary Closure
General risk of infection from any wound
sutured in the ED is 3-7%
Depending on species, risk varies:
Dog Bites (all locations)
Dog Bites Hand
Dog Bites Face
Cat Bites (all locations)
5 - 10%
12 - 30%
0 - 5%
30 - 50%
Most wild animal bites similar to dog or cat in
bacterial isolates, in general:
Bears = Dogs
Large Cats = Small Cats
Location of Bites
Talan, “Bacteriologic Analysis of Infected Dog and Cat Bites” NEJM Vo.340 No. 2 Jan 1999
Hand Wounds - A Special
Circumstance
The hand is a highly specialized structure
Poorly vascularized structures and tendon sheaths
that poorly resist infection
Fascial spaces and tendon sheaths of the hand
communicate with each other promoting spread of
infection rapidly
Due to multiple connecting spaces, irrigation may
not effectively reduce bacterial numbers
Hand Bites - Data From
Domestic Animals
Retrospective study from Oslo, Norway
“All hand wounds healed uneventfully when the
wounds were left open”
European Study:
Base line rate of infection of cat and dog bites was
18.8%
Rose to 25% if the wound was closed primarily
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Average time to first medical treatment was 11 hours
Dahl “Animal bites at the casualty department of Oslo city council” Tidsskr Nor Laegeforen 18:2614 1998
Aigner “Bite wounds and their characteristic position in trauma surgery management” Unfallchirurg 99:346 1996
Summary of Bite Wound
Closure Recommendations
Hals “Bites and Stings: An Overview of Close Encounters with Nature. Part 1” Emergency Medical Reports Vol. 26 No. 9 April
18, 2005
Treatment of the Hand in
Particular
Irrigate and debride if possible
Leave open initially
May choose to perform delayed
primary closure at a later date
Immobilize and splint in an
elevated position
Initiate antibiotics
In instances of confirmed
infection,
Consider admission for IV
antibiotics
Specialty consults and followups
Infected cat bite R hand, Nov 2000
The Animals
Black Bear
General Description
4 - 7 feet tall nose to tail
2 - 3 feet at shoulder
Adults weigh between 125 and 500 lbs
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Depending on age season and food
Black coat - occasionally brown or blond
Range - Found only in No America
Population estimated at 750,000
Range into Canada and as far south as FL and Mexico
Mating season - May - July with births in Jan/Feb
Black Bear - Characteristics
Large brain size in comparison to body
One of the most intelligent mammals
Excellent swimmers
May run greater than 30 mph
Most are active during the day
Exception is afternoon nap
Rare few are active at night
Black Bear - General
Adapted for arboreal environment
Prefer vegetation and carrion
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Live prey makes up less than 5% of diet
Have sharp, short radius claws adapted
for climbing trees
Black bears tend to retreat in the face of
danger
Using trees for safety
Recognizing Black Bear
Habitat
Scat - droppings
Tracks
Other Markings
Dens
Tree scars
Bear Sounds
Bear Scat
Appearance varies with bear’s diet
Black bears are mostly vegetarians
Scat therefore mainly contains plant
materials
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Berries, buds, leaves, bark, nuts
May contain ruminants of opportunistic
diet
Tin cans, boxes, food containers/wrappers
Bear Tracks
Bears are pacers - moving both legs on one side of
the body at a time (alternating both right limbs then
both left)
Plantigrade - heal of the back foot lands flat
Short claws with slightly separated toes
Arc of toes greater in black bears than grizzly bears
Brown Bears
AKA - Grizzly Bear or Kodiac
Historically found across No America
Esp in open habitats of plains
Currently found only in the Rocky Mountains in the
contiguous US and in Alaska
British Columbia, Alberta, Yukon, No West
Territories, Alaska, Idaho, Wyoming,
Washington and Montana
Grizzly Food
Omnivores
Mostly feed on berries, roots, bulbs if
plants, whitebark pine nuts, and grasses
Also ground dwelling rodents, moose,
elk, mountain goats, and mountain
sheep
Cut worm moths
Grizzly Size and Color
Typically brown in color but may be
white or black
Grizzly bears may reach up to 10 feet
tall
Usually closer to 6 - 8 feet depending on
gender
Weights usually 270 - 770 by 8 years of life
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Record of 1000 lbs
Brown Bear - General
Claws are long and curved, coupled with their
strong shoulder muscles, makes them well
adapted for digging and ground feeding
Because they evolved in predominantly open
habitats, are not adapted to retreat from
danger
Behavior in general is aggressive if
confronted
In particular, mothers will aggressively protect
cubs
Recognizing Brown Bear
Habitat
Tracks - toes are grouped close
together and follow nearly a straight line
with little arch
Front tracks measure 6 - 8 inches long
and 7 - 9 inches wide
Hind tracks measure 12 - 16 inches
long and 8 - 10.5 inches wide
Frequency of Bear Attacks
Rare - average of 10 people injured and 1
death per year
500 attacks reviewed
37 fatal and 12 sustained major injuries
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> 35 sutures, major internal organ system injured,
required surgery, hospitalized > 24 hours
Most attacks by human habituated, food
conditioned or predaceous bears
Attack rates are generally increasing
Bear-Human Interactions
Bears in general tend to avoid humans
When encounters do occur, three types
Sudden Encounters - neither person or bear
aware of each other until in close range
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Account for 90% of injuries in Yellowstone
Black bears tend to flee - even mothers with cubs
Grizzly tend to be aggressive - 70-80% of all encounters
are with mothers and cub
• Usually brief, < 2 min and likely meant to neutralize threat
while cubs flee
Provoked Attacks
Increasing frequency as more people explore
bear habitat
Second most common cause of bear-related
injuries
Predation
Bear directly treats victim as food source
Almost exclusively with male bears in remote
locations
Accounts for 90% of attacks by black bears
Less likely with brown bears
Medical Management
Initial management includes stabilization and
rapid evacuation
In fatal wounds, death commonly due to
exsanguination
Most wounds, however, are minor
If small, clean and little crush, may be closed
primarily (if not involving the hand)
Major wounds commonly require surgical
debridement and exploration
Many are re-explored 24 - 48 hours later due to
significant crush component
Infection from Bear Attacks
Tetanus prophylaxis should be current
Rabies immunization controversial
Rabies has rarely been documented in domestic
bears
CDC however recommends rabies immunization
Bear oral flora much like that of dog’s and is
generally responsive to Augmentin
Avoiding Bear Attacks
Avoid areas with obvious signs of bear
Esp. fresh scat
Travel in groups of three or more
Review of 143 bear encounters
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88% involved solitary hikers, 8% in parties of 2, 3% in
parties of 3 none in parties of 4 or more
Noise - make bears aware of your approach
Avoid bear bells, esp in National Parks
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Predatory bears equate bells with food
Keep campsites clean and food stored in
bear bags in trees or in airtight containers
Sleep in partially zipped sleeping bags
Response to Black Bear
Attack
Appropriate behavior depends to some extent
of the species of bear attacking
Black Bears
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Attacking black bears usually predacious with intention of
killing victim
Only chance for survival is to attempt to intimidate the
bear or, in the case of physical contact, fight back
Make loud noises, raise arms above head, raise large
object above head (not backpack)
Running not effective as black bears can travel at speeds
of 30 mph - unless shelter near by
Climbing trees not effective as black bears are excellent
climbers
Response to Brown Bear
Attack
Most charges are bluff charges or attempts to
investigate
If physical contact is made, usually from
mother
Intention in these instances is to neutralized
perceived threat
Therefore, victim should fall to ground and play
dead
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Important to remain still
• 80% of those who fight are injured
• Remain still for several minutes after the event to ensure
the bear is gone
Cougars AKA Mountain Lions
Cougars
Also known as Mountain Lions, panther,
catamount, or Puma
Once the most widely distributed animal in No
America
Hunted to near extinction on early 1900’s
Gained protective status in 1960’s
Currently population at approximately 20,000
Live in 11 western US states, BC, Alberta,
and FL (ruminant population)
None verifiable in Northeastern US
Cougar Attacks
Infrequent in number but uniformly
severe
39 injuries between 1992 and 1972
Encounters on the increase though as
humans encroach on cougar territory,
cougar populations rebound, and
increased recreation in the wilderness
Attacks on the Increase
46 non-fatal attacks between 1900 - 1992
33 of these since 1970
Cougars do not generally perceive human’s
as prey
Prefer instead deer, elk, porcupine, marmot,
beaver, hare, raccoon and other small animals
Extremely territorial with younger animals
forced toward fringe territories with increased
risk of human contact and potential for
habituation towards humans
? Preferential Prey ?
Children involved in many more attacks
than adults
? If due to smaller size and therefore
perceived “easier” prey
Although cougars often attack animals at
least their size if not larger with no difficulty
Cougar Attack - Case Report
18 y/o male jogging mountain trail behind his
CO high school on Jan 14, 1991 @1330
Common site for recreation
Attacked suddenly from left, posterior without
warning
Cougar bit the pt in the neck
Extensive soft tissue injury
Transected R IJ and puncturing R carotid
Claw marks to L posterior and superior thorax
Cause of death - exsanguination
No c-spine injury
Cougar Attack - Case Report
Patient and cougar rolled down 10 foot
embankment together
After patient died, was dragged a further 30
feet under a tree
Post-mortem damage = loss of multiple
structures of the chest (ribs, L lung, heart,
aorta), evisceration of bowel, skeletonization
of the face.
Punctures to the skull and face found
Mechanism of Attack
Many victims do not see the cougar and are
attacked suddenly from behind
Smaller numbers report seeing the animal before the
attack exhibiting “stalking” behavior
Horizontal leaps of 45 feet have been reported
with common distances of 15 - 20 feet
Teeth are 1 - 2 inches in size and claws are 1 1.5 inches in size
Cougars attempt to kill on first pass
Smaller lungs and limited cardiovascular endurance
Site of Attack
The neck is this primary site of attack
Two mechanisms of injury:
Forcible hyperextension causing cervical fracture
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With teeth embedded in the neck and claws in the back
of the victim, the cougar then shakes it’s prey to aid in
vertebral fracture or dislocation
Sharp transection of anterior structures
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Teeth and claws used - depth of wounds greater than
external injuries suggest
Extremity wounds usually defensive
After Victim Death
Cougars rarely attack for sport and will
generally eat their prey after it dies
Will usually consume contents of thorax as
well as abdomen
Later will feed on lions and extremities
Large sized animal will keep cougar fed for
up to 14 days
During this time, cougar will remain in close
proximity to prey
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In our case report, the cougar was easily found nearby
Implications for rescuers
Medical Treatment
Most victims survive to medical
treatment
Phases of acute care
Resuscitation
Wound care
Identification of deep or occult damage
Infectious concerns
Acute Phases of Resuscitation
Most victims will have injuries involving the
neck
Mandates appropriate work up of injuries to
the:
Cervical spine and cord
Trachea or esophageal injuries
Neuro/vascular injuries
Penetrating injuries to skull with subsequent
cerebral injuries
Further work up dictated by sites of injury
Chest, abdomen, extremities
Wound Care
Cougar injuries unlike many other
animal injuries in that they are usually
described as sharp and clean
Due to wound characteristics, primary
closure of wounds not uncommon
Except on hands
Deep structure injuries not uncommon
due to size of teeth/claws
Infectious Concerns
Large cat bites considered high risk for
infection
Poor evidence for nature of large cat flora but
generally considered similar to that of
domestic cats
Pasturella multocida
IV antibiotics recommended in early
treatment
Chronic deep infection, osteomyelitis, septic
arthritis, abscess, or embolization reported
Avoiding Attacks
Increase apparent size
Raise arms above head
Waive objects above head
Pick up children
Combined size appears larger to the cougar as well as
preventing the child from running
Slowly back away
Quick movements may be interpreted as fear
Loud sounds as well as threatening voice may be
effective
If attacked, fight back - vigorous resistance has
thwarted cougar attacks
Goring from Bison and Cattle
Bison Goring - Case Report
42 y/o female approaches w/in 20 feet of a
bison when it charged her
Bison gored her through the jeans, along
the R thigh and extending upward toward
the abdomen
Bison Goring - Case Report
continued
EMS VS = 144/98, 110, 20
Exam = penetrating wound
4 cm above the inguinal
ligament extending from
an 18 cm lateral thigh
laceration
Exposed fascia and muscle
form the patella to the pelvis
No injury to femoral canal
Ex Lap negative for bowel
injury
Wound debrided and
received IV Abx for 3 days
Bison goring injury to lateral thigh, courtesy, L Freer,
Yellowstone Nat Park
Bison - General
AKA buffalo - used to roam the western
plains in the millions
Hunting and westward migration of
humans nearly brought extinction to the
bison
Currently few remaining herds
In US - Yellowstone is only active area
Bison - Characteristics
Appear stogy, slow and difficult to provoke
In reality, may be very aggressive and violent
if approached
Stand 5 - 6 feet at the shoulder, weight 1000 2000 lbs and may charge up to 20 mph
Horns are boney with hard epidermal sheath
On average 20 - 25 cm (8 - 10 in)
Bison Related Injuries
Bison cause injury from 4 general mechanisms:
Goring
Butting/Shoving
Charging
Tossing in the air
41%
12%
22%
16%
These mechanisms similar to those of cattle and
other live stock
Bison Injuries - Site of Injury
During a goring, head held low. At impact, the animal
extends it’s head with horns following natural arch
Leads to many injuries in lower half of body
40% of injuries to upper thigh, buttocks, perineum, abdomen
Buttocks, thighs involved as victim runs away
Bison Attacks - Types of
Injuries
No bites recorded
Penetrating injuries to abdomen - thigh
Some eviscerations, no bowel trauma
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Relatively slow moving horns push bowel out of way
Blunt injury from shoving, butting, and
throwing
No reported injuries to head and neck
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Remain potential injuries
Blunt injury to lungs only
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No PTX
Risk of Infection
Goring type injuries typically large and deep
penetrating injuries
Wounds are so large, they are easily irrigated
Anecdotal suggestions that “dirt” horns are
high risk to seed soil/bacteria in wounds
Study of 56 bison gorings showed no infection
Cattle gorings studies in India resulted in no to few
infections
Most any positive cultures were consistent with
any post surgical wound infection
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Gram Positive
Deer and Moose Injuries
Responsible for 65% of all animal
induced injuries per year
Majority due to motor vehicle accidents
Moose weigh 600 - 1700 lbs
Commonly cause major front end damage
to vehicle
Moose legs clipped and falls onto hood or
into passenger compartment of vehicle
Trampling Injuries
Little literature and few cases
Major blunt trauma
Head, chest, abd/pelvis, extremities
No data on extent of injuries, nature of
injuries, or common patterns of injury
Anecdotally, many cases fatal
Exotic Pets - Chimps and
Monkeys
Few US reported cases and no studies
Cases reported involve major amounts of
trauma
Conventional agreement on high risk for
infection
Polymicrobial with mixed aerobic/anaerobic
Rats and Mice
Account for 2 - 10% of animal bites
presenting to the ED
Smaller animals generally do not cause major
injuries
Defined as deep, penetrating, debilitating
cosmetically or functionally
Exception is in small children
Rat bites become infected 2 - 5 % of the time
Rabies is rare in wild rodents
Yersinia pestis still pathogenic in So Western US
Raccoons, Skunks, Foxes
Rabies common in all these animals
Skunks frequently rabies positive when caught
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Luckily, rarely bite but spray instead
• Ocular and pulmonary irritant but does not spread rabies
Foxes rarely bite humans, nocturnal and avoid
human contact
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Therefore is human is bitten, should be considered high
risk
Raccoons account for > 50% of rabies
documented in the US
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All bites are high risk for rabies
Rate of other infection uncertain
Bats
Similar to mice, cause little damage when do
bite
Very small teeth
Most bites cannot penetrate skin
Very high risk for rabies transmission
Most common cause of rabies transmission in the
US
Any contact with a bat in which a bite cannot be
excluded should be treated with rabies prophylaxis
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Sleeping or non-verbal adult
Small child
No data on other infections
Questions?