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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 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 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 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 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 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 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 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 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 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 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 > 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 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 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 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 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 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 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 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 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 Relatively slow moving horns push bowel out of way Blunt injury from shoving, butting, and throwing No reported injuries to head and neck Remain potential injuries Blunt injury to lungs only 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 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 Luckily, rarely bite but spray instead • Ocular and pulmonary irritant but does not spread rabies Foxes rarely bite humans, nocturnal and avoid human contact Therefore is human is bitten, should be considered high risk Raccoons account for > 50% of rabies documented in the US 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 Sleeping or non-verbal adult Small child No data on other infections Questions?