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Heat stress txolan 2012

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This is the slides from a lecture delivered by Dr. Ben Buchanan at the 2012 TXOLAN Alpaca Spectacular Show.

This is the slides from a lecture delivered by Dr. Ben Buchanan at the 2012 TXOLAN Alpaca Spectacular Show.

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Heat stress txolan 2012 Heat stress txolan 2012 Presentation Transcript

  • Heat Stress Hyperthermia Benjamin Buchanan, DVM Diplomate American College of Veterinary Internal Medicine Diplomate American College of Veterinary Emergency and Critical Care Brazos Valley Equine Hospital, Navasota Texas
  • Who is BVEH?
    • Group of Large Equine Hospitals
      • Navasota
      • Stephenville
      • Rockdale
    • Navasota
      • Full service referral facility
      • Started admitting camelids in 2008
  • Who is BVEH?
    • Two Internal Medicine Specialists
      • Ben Buchanan
        • Residency in Knoxville, TN at UTK
        • 50% Equine, 50% Food Animals
        • Trained under Sarel Van Amstel
        • Second residency in Emergency and Crtical Care
          • University of Pennsylvania
        • Navasota - 2005
    View slide
  • Who is BVEH?
    • Two Internal Medicine Specialists
      • Tiffany Hall
        • Residency at UC Davis
          • Finished in 2010
        • Started as Emergency and Critical Fellow at BVEH in 2010.
    View slide
  • Goal of Lecture
    • Lecture will cover heat stress, cause, prevention, diagnosis, treatment at the ranch before transport and what to expect after treatment.
    • Include original data from BVEH
  • Definitions
    • Heat Stress
    • Hyperthermia
    • Heat Exhaustion
    • Heat Cramps
    • Heat Stroke
  • Definitions
    • Heat Stress
      • General name for several medical conditions (heat exhaustion, heat cramps, heat stroke).
  • Definitions
    • Hyperthermia
      • “ Elevated body temperature due to failed thermoregulation ” – Wikipedia
      • Occurs when body absorbs or produces more heat than it can dissipate
  • Definitions
    • Heat Exhaustion
      • “ A condition characterized by faintness, rapid pulse, nausea, profuse sweating, cool skin, and collapse, caused by prolonged exposure to heat accompanied by loss of adequate fluid and salt from the body” – Dictionary.com
  • Definitions
    • Heat Cramps
      • Muscle cramps causes by electrolyte and water loss secondary to heat related illness.
  • Definitions
    • Heat Stroke
      • “ Hyperthermia caused by environmental exposure to heat accompanied by phsical symptoms including changes in nervous system function” – Medicinenet.com
      • Can be exertional or non-exertional
      • Damages brain, heart, kidneys, muscles
      • Medical emergency
  • Discussion
    • Based on literature
    • Based on BVEH experience
    • Based on collective veterinary experience
  •  
  •  
  •  
  • Discussion
    • Normal Metabolism
    • Heat Distribution
    • Definitions
    • Effects of Hyperthermia
    • Risk Factors
    • Symptoms
    • Diagnosis
    • Treatment
    • Prevention
    • Complications
    • Prognosis
    • BVEH – Cases
      • Demographics
      • Survival
      • Cost
  • Metabolism
    • Requires water
    • Human
      • Ingest 2.3 liters per day
      • Output
        • Skin 350 ml per day
        • Lungs 350 ml per day
        • Sweat 100 ml per day
        • Feces 100 ml per day
        • Urine 1400 ml per day
  • Metabolism
    • Camelids
      • 67% of body weight is water
      • ~1 liter per 100 pounds of body weight in thermoneutral environment
      • ~5 liter per 100 pounds on pasture
        • Includes water in forage
  • Metabolism
    • Camelids
      • Will intake less water when food intake is restricted.
      • Lactation increase water demand significantly
      • All same social factors that impact feeding may impact water consumption
      • Water intake is critical!
  • Metabolism
    • Requires water
    • Carries nutrients to cell
      • Turned into energy, ATP, fat, polysaccharides
    • Carries waste products away from cell
      • Carbon dioxide
      • HEAT
        • End product of ALL chemical reactions
  • Metabolism
    • Water requirement is equal to metabolism
    • For every kCal of energy need 1 ml of water
    • Increased energy demands = more HEAT = more water
      • Exercise
      • Late Pregnancy
  • Metabolism
    • Requires water
    • Waste products carried in blood
      • Requires adequate blood volume
      • Requires perfusion
    • Poor perfusion to skin = poor heat transfer
  • Metabolism
    • Getting rid of HEAT
      • Three Methods
        • RADIATION
        • CONDUCTION
        • EVAPORATION
  • Metabolism
    • Getting rid of HEAT
      • RADIATION
        • Transfer of heat via infared heat waves
        • Requires environmental temp next to skin be less than core body temp
        • Major source of heat loss
  • Metabolism
    • Getting rid of HEAT
      • CONDUCTION
        • Transfer of heat to objects touching the body
          • Minor source of heat loss normally
          • Laying on cool ground
        • Transfer of heat to air
          • Significant source of heat loss
          • Requires air to be cooler than skin
          • Air movement important (air convection)
        • Cooling effect of wind proportional to speed of wind
          • Not linear but SqRt of velocity
  • Metabolism
    • Getting rid of HEAT
      • EVAPORATION
        • Loss of heat via conversion of liquid to gas
        • Insensible loss in lungs
        • Sweat
  • Metabolism
    • Impact of Fiber as Insulator
      • Holds air next to skin and impacts Conduction and Convection
      • Insulation is impacted when fiber gets wet
    • Fat is also an insulator!
  • Metabolism
    • High Environmental Heat
      • Stops Radiation
      • Stops Conduction
        • Actually gains heat via Radiation and Conduction
      • Only route of heat loss is Evaporation
  • Metabolism
    • High Humidity
      • Impacts efficiency of Evaporation
  • Metabolism
    • Heat Index
      • Temp + Humidity
      • <120 is ok (80 F and 40% humidity)
      • 120 to 160 is slight risk
      • 160 to 180 is significant risk (80 F and 80% humidity)
      • >180 is severe risk (105 F and 80% humidity)
  • Metabolism
    • Combination of Heat and Humidity is KILLER
  • Metabolism
    • Dehydration
      • Camelids can sustain a 25% loss in body weight from dehydration with no ill effects
        • Shape of RBC allows for swelling and contraction
      • Loss of 40% of plasma volume
    • Impacts ability to respond to heat stress
  • Metabolism
    • Impacts ability to respond to heat stress
      • Lack of blood plasma reduces delivery of blood to skin
        • Less heat transfer
        • Less sweating
      • Must increase heat transfer via respiration
      • Increased respiratory rate compared to normohydration
  • Effects of Hyperthermia
    • 104 F threshold in humans and other species for heat stroke
    • Increases tissue oxygen demand
      • Core temp above 105 F
      • Unable to take in enough oxygen
        • Supplement with nasal oxygen
    • Proteins denatures at 113 F
  • Effects of Hyperthermia
    • Three important control mechanisms for cooling
      • Vasodilation
      • Sweating
      • Decrease in heat production
  • Effects of Hyperthermia
    • Vasodilation
      • All areas of the skin
        • Helps carry heat to skin
        • Increase delivery 8 times above normal
        • May drop blood pressure
      • Radiation and conduction heat transfer
  • Effects of Hyperthermia
    • Sweating
      • Instantaneous with core temp increase
      • 2 degree increase in body temp causes 10 fold increase in sweating (HUMAN)
      • Sweat glands in SAC are poorly developed
        • Located over entire body
        • Concentrated on ventrum
  • Effects of Hyperthermia
    • Decrease heat production
      • Inhibition of excess heat production
        • Shivering
  • Effects of Hyperthermia
    • Sequence of Events
      • Increase in Core Body Temp
      • Adaptation with increase RR and HR
      • Sweating
      • Dehydration – fluid shifts
      • Muscle cramps = Recumbency and stiffness
      • Loss of blood pressure control
      • Heat Stroke
  • Effects of Hyperthermia
    • Heat Stroke
      • Circulatory collapse
        • Lack of vasomotor control
        • Loss of adequate blood volume
      • Disseminated Intravascular Coagulation (DIC)
        • Bleeding and clotting disorder
        • Damages other organs and spine
      • Teratogenic effects
  • Risk Factors
    • Geography and Travel
    • Heat Index and Duration
    • Fat and Fiber
    • Increased activity (fighting, packing, etc)
  • Risk Factors
    • Food and Water intake
    • Pregnancy and Lactation
    • Lack of appropriate shelter
    • General health / Parasitism
  • Symptoms
    • Clinical Signs
      • Increase HR and RR
      • Nose flaring
      • Open mouth breathing
      • Drooling
      • Cushed over water or leaning forward
      • Laying in abnormal positions
  • Symptoms
    • Clinical Signs
      • Scrotal swelling
      • Decreased GI function
      • Poor appetite
      • Frequent cooling in sprinkler or pools
      • Stiff gait
      • Neurologic deficits
  • Diagnosis
    • Clinical Signs and History
    • Lab Values
      • High CK/AST – muscle damage
        • Most consistent abnormality
      • Low Platelets
      • Stress response
      • Other organ damage
      • CTnI and Lactate
  • Therapy
    • Emergency Cooling
      • RADIATION
        • Shade
      • CONDUCTION
        • Fans
        • Concrete
        • A/C
      • EVAPORATION
        • Water
        • Fans
      • DO NOT PUT ICE ON SKIN
      • Contact Veterinarian
  • Therapy
    • Veterinary care
      • Fluids
        • Blood Pressure
        • Cold – Core Cooling
        • Correct Acid-Base and Electrolyte Issues
      • Enema
        • Cold water
      • Oxygen
  • Therapy
    • Veterinary care
      • Pain Management
        • Critical
        • Muscle damage is painful
        • Nephrotoxic?
      • Vitamins
        • Target at metabolism and muscle repair
        • B Vitamins, Vitamin E
  • Therapy
    • Veterinary care
      • Antibiotics
        • Especially with recumbency
      • Slings and Pools
        • Helpful in recovery
        • Not in acute stage
  • Therapy
    • Veterinary care
      • Recumbency management
        • Physical therapy
        • Supportive care
        • Nutritional therapy
  • Prevention
    • Environment
      • Air quality
        • Lots of fans and misters
          • Consider humidity when using mister
          • Consider fan quality
        • Adequate space for herd
      • Sprinklers and ponds
  • Prevention
    • Environment
      • Shade and Shelter
        • Important year round
      • Try to avoid traveling in heat of day July and August
  • Prevention
    • General Health
      • Body Condition Score
      • Weigh Frequently
        • Identify dehydration and body water loss early
      • Monitor temps
        • Microchips
  • Prevention
    • General Health
      • Screen for parasites
      • SHEAR! and repeat in July or August if necessary
  • Prevention
    • Breeding
      • Plan breeding
        • Not heavy pregnant in July, August, September
        • >30 days pregnant by July 1
      • Weaning
        • Not lactating in July, August, September
        • Wean before July
      • Heat temporarily damages sperm quality
  • Prevention
    • Nutrition
      • Monitor food intake
        • Decreased food intake = decreased water intake
      • Provide excessive amounts of clean water in multiple locations
      • Vitamins
        • Vit E?
      • Herbs and Minerals?
  • Complications
    • Complications
      • Acute death
      • Chronic neurologic impairment
      • Increased susceptibility to future hyperthermia
      • GI dysfunction
  • Complications
    • Complications
      • Problems of recumbency
        • Pneumonia
        • Eye ulcers
        • Bed sores
        • Urine/fecal scalding
  • Prognosis
    • Prognosis?
      • People
        • Rarely leads to permanent deficit with heat stroke
        • Not always true
          • Chicago study 58 heat strokes
          • 25% died within 3 months after discharge
          • Remainder had permanent neuro impairment
          • Half had chronic organ damage (Kidney)
          • Age not a factor
  • Prognosis
    • Prognosis?
      • Alpacas
        • Not known
        • Restrospective Case Evaluation of BVEH
          • 2008 through 2011
          • Seasons
          • Laboratory
          • Therapy
          • Cost
          • Survival
  • Case Discussion
    • BVEH Cases
      • 22 Records
        • 2008 – 1 patient
        • 2009 – 6 patients
        • 2010 – 7 patients
        • 2011 – 8 patients
  • Case Discussion
    • BVEH Cases
      • Season
        • June – 2 cases
        • July – 2 cases
        • August – 13 cases
        • September – 4 cases
        • April – 1 case
  • Case Discussion
    • BVEH Cases
      • Laboratory Values
        • CK/AST – 100% increased
          • < 10 % of recumbent alpaca had increase
        • Glucose – 30% increased
        • Lactate – 20% increased (all died!)
        • CTnI – Elevated in 3 cases (2 died)
  • Case Discussion
    • BVEH Cases
      • Laboratory Values
        • CK/AST
          • Internal component of muscle cell
          • Requires lysis of cell for increase
          • CK goes up first
          • AST remains elevated longest
  • Case Discussion
    • BVEH Cases
      • Laboratory Values
        • Lactate
          • Indication of oxygen debt
            • Increased metabolism beyond normal
            • Decrease in oxygen delivery
          • Poor delivery
            • Blood pressure control
            • Lack of blood volume
  • Case Discussion
    • BVEH Cases
      • Laboratory Values
        • CTnI
          • Internal component of HEART muscle
          • Cleared rapidly
          • Elevation is indication of ongoing damage
  • Case Discussion
    • BVEH Cases
      • Therapy
        • Air conditioning
        • Most received IV fluids
        • Most received ESE
          • Non-surviors more likely to not receive ESE
          • Likely due to acute nature of death
          • Added to therapy in 2010
  • Case Discussion
    • BVEH Cases
      • Cost
        • Average length of stay = 9 days (range 4 to 30 days)
        • Average invoice total = $1,374.63 (range $466.70 to $4,571.07)
  • Case Discussion
    • BVEH Cases
      • Survival
        • 14 out of 22 discharged alive 63%
          • 1 to 7 years of age
          • Rectal temp at presentation – 103.7 F
      • Non survivors
        • 8 out of 22 died in hospital 37%
          • 2 to 10 years of age
          • Rectal temp at presentation 105.1 F
  • Case Discussion
    • BVEH Cases
      • Long term
        • Not officially completed
        • Several relapsed and presented the following or subsequent years
        • Several had neurologic deficits
        • One aborted cria
        • Several euthanized at home for variety of reasons
  • Case #1
    • Adult male
      • Houston Weather on August 21, 2009
        • 0.73 inches of rain
        • High of 100 F
        • Humidity ~ 71% with high of 100%
        • Wind 5 to 32 mph
      • 8 consecutive days of > 95 F and 95%
  • Case #1
    • Aug 21
      • Acutely recumbent 5 pm on farm with fever
        • Given banamine by owner
      • Presentation
        • 106.8 on arrival
        • Increased RR at 40 bpm
        • Lateral recumbency
        • Transported into ICU (air conditioned)
  • Case #1
    • Aug 21
      • 7 pm
        • Fans and water bath
        • Placed IV catheter (jugular)
        • Bolus 2 liters of room temp electrolyte fluids
        • Switched to cold fluids post bolus
      • Laboratory
        • CK unmeasureable, AST unmeasureable, Glu 300 mg/dl, Creatinine 2.2 mg/dl
  • Case #1
    • Aug 22
      • 9 pm
        • Temp 97.7 F, HR 52, RR 24
      • 2 am
        • Temp 95.7 F
      • 8 am
        • Temp 97.2, HR 40, RR 12
        • Unable to stand
  • Case #1
    • Aug 22
      • 8 am
        • Given banamine IV
        • ESE IM
      • 5 pm
        • T – 95.7 F, HR 40, RR 16
        • Good appetite unable to stand
  • Case #1
    • Aug 23 to Aug 25
      • Kept in ICU, but taken off 24 observation and care
      • Continued banamine and physical therapy
    • Aug 26 moved out of ICU
      • Temp spiked to 102.4 – 104.3
      • Continued banamine and physical therapy
  • Case #1
    • Laboratory
      • Aug 26
      • CK – decreasing 1497
      • AST – unmeasurable
      • Glu – 170 mg/dl
      • Creatinine 1.3 mg/dl
  • Case #1
    • Aug 26 – 31
      • Continued to have rectal temp 103 F to 104 F
      • Continued PT and banamine
    • August 31
      • Stood with assistance
      • CK – 407 IU/L, AST – 1988 IU/L
      • Went home
  • Case #1
    • Conclusions
      • Muscle damage is part of syndrome not recumbency
        • Returned to normal despite being recumbent
      • CK / AST values indicative of severity and possibly level of pain.
      • Need to address muscle issues with recumbency
  • Take Home
    • 5 Most Important Points
      • Combination of heat and humidity is important
      • Understand and manipulate cooling
      • Shear early and repeat
      • Monitor appetite and water intake
      • Diagnose early and treat aggresively
  • Questions?