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Mammalian Injuries

Mammalian Injuries

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Mammalian Injuries

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  1. Mammalian Injuries Wilderness Medical Consortium Matthew Sholl

  2. 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

  3. 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 Species

  4. 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

  5. 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 • 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

  6. 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

  7. When Injuries Do Occur… • Often devastating due to : • Size and weight of animal • Moose routinely weigh > 1000 lbs • Animal’s strength… • Dog’s bite strength approximately 200 psi • Six times that of a human • 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

  8. 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

  9. Evaluation, continued • Evaluation of animal injuries challenging: • Risk of blunt injury - trampling, throwing • Risk of penetrating injury - goring, biting • External wound may belie the patient’s underlying injuries • Risk of infection generally higher than standard wounds • Contaminates from saliva, nasal secretions, soil • Penetrating and puncture wounds • Many injuries occur in remote areas removed from medical care

  10. 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

  11. 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

  12. 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

  13. 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….

  14. Risk Factors for Infection from Animal Injuries/Bites From Freer, L “Bites and Injuries Inflicted by Wild Animals”, pg 984 Wilderness Medicine 2001

  15. “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

  16. 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) 5 - 10% • Dog Bites Hand 12 - 30% • Dog Bites Face 0 - 5% • Cat Bites (all locations) 30 - 50% • Most wild animal bites similar to dog or cat in bacterial isolates, in general: • Bears = Dogs • Large Cats = Small Cats

  17. Location of Bites Talan, “Bacteriologic Analysis of Infected Dog and Cat Bites”NEJM Vo.340 No. 2 Jan 1999

  18. 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

  19. 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 • 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

  20. 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

  21. 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 follow-ups Infected cat bite R hand, Nov 2000

  22. The Animals

  23. Black Bear • General Description • 4 - 7 feet tall nose to tail • 2 - 3 feet at shoulder • Adults weigh between 125 and 500 lbs • 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

  24. 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

  25. Black Bear - General • Adapted for arboreal environment • Prefer vegetation and carrion • 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

  26. Recognizing Black Bear Habitat • Scat - droppings • Tracks • Other Markings • Dens • Tree scars • Bear Sounds

  27. Bear Scat • Appearance varies with bear’s diet • Black bears are mostly vegetarians • Scat therefore mainly contains plant materials • Berries, buds, leaves, bark, nuts • May contain ruminants of opportunistic diet • Tin cans, boxes, food containers/wrappers

  28. 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

  29. 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

  30. 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

  31. 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 • Record of 1000 lbs

  32. 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

  33. 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

  34. 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 • > 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

  35. 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 • 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

  36. 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

  37. 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

  38. 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

  39. 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 • 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 • 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

  40. Response to Black Bear Attack • Appropriate behavior depends to some extent of the species of bear attacking • Black Bears • 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

  41. 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 • 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

  42. Cougars AKA Mountain Lions

  43. 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

  44. 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

  45. 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

  46. ? 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

  47. 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

  48. 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

  49. 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

  50. Site of Attack • The neck is this primary site of attack • Two mechanisms of injury: • Forcible hyperextension causing cervical fracture • 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 • Teeth and claws used - depth of wounds greater than external injuries suggest • Extremity wounds usually defensive