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74 Cards in this Set
- Front
- Back
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*What is a normal temperature for a cow?
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100.4-102.5
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*What is the normal temperature for a horse?
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99.5-100.8
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*What is the normal temperature of sheep?
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102.2-104
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What is the normal temperature of a pig?
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100.4-104
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What is the normal temperature of a dog? Cat?
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100-102.5= dog and cat
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Core temperature varies with what 5 factors?
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1) Age
2) Ambient temperature -old, young, sick or drugged animals 3) Exertion -increases in temperature are related to intensity 4) Feeding 5) Reproductive cycle |
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Feeding is an important source of heat in what animal?
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Ruminants
-can feed more roughage to increase heat production |
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What are 3 things that can give false readings on a rectal thermometer?
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1) Decreased anal tone
2) Air in rectum 3) Insertion of thermometer into feces |
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Control of core temperature is a balance of _____ and ______.
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Heat produced and lost by body
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What are 6 things that cause body heat production?
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1) Basal metabolic activity
2) Muscle activity -increased movement or shivering 3) Thyroxine 4) Sympathetic stimulation 5) fat metabolism 6) digestion |
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What are 2 ways animals conserve body heat?
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1) Autonomic stimulation
-reduces peripheral circulation & heat loss through skin -piloerection for insulation 2) Behavioral changes -huddling, grouping and seeking shelter from the elements |
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**What are the 4 modes of heat loss?
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1) Conduction
2) Convection 3) Radiation 4) Evaporation |
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What is conduction? Convection?
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Conduction: transfer of heat to another object
Convection: transfer of heat to water or air |
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What is radiation?
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Heat lost from surface by infrared radiation
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What is the dominant source of heat loss when the ambient temperature rises?
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Evaporation
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What are 2 routes of evaporation? What animals perform each?
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1) Respiratory tract (panting)
-dogs, ruminants 2) Skin (sweating): horses and humans |
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What are 2 minor modes of heat loss?
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1) Cutaneous vasodilation
2) Behavioral changes -seeking shade or water sources -decreased activity |
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Explain how body temperature is controlled by the negative feedback system in the anterior hypothalamus.
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-peripheral temperature sensitive neurons relay info to pre-optic area
-acts as a thermostat: 'set point' at which it will maintain core temperature ~transition of core temperature below or above set point will alter behavioral and homeostatic response to lose or acquire heat |
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What 4 things happen when there's activation of warmth sensitive neurons in the skin and mucous membranes?
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1) Increased RR
2) Vasodilation 3) Sweating 4) Attempts to find a cooler environment |
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What are the 4 responses to activation of cold sensitive neurons?
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1) Vasoconstriction
2) Piloerection 3) Increased muscular activity 4) Postural and behavioral changes to conserve heat |
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What is the central thermosensitivity of the body?
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Hypothalamus also responds to changes in blood temperature
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What animals are very susceptible to hypothermia?
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Neonates, cachexic or geriatric animals in cold environments very susceptible
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What causes hypothermia?
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-inability to generate or maintain body heat
-metabolic causes |
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What can be a complicating factor to treating hypothermia in neonates?
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Sepsis
-immune defenses compromised by hypothermia |
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What are 5 clinical signs of hypothermia?
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1) Low rectal temperature
2) Depressed ventilation 3) Absence of shivering -bad sign, means really cold 4) Decreased reflexes 5) Decreased cardiac function & increased intravascular volume |
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Core temperatures < ____ F impair temperature regulation.
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< 94 degrees F
-rate of cellular heat production halves for each 10 degrees F decrease in body temp |
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How do animals that hibernate decrease their body temperature without any ill effects?
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Slowed metabolic and physiologic processes
-decreased RR/HR, loss of consciousness |
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What are 4 causes of hyperthermia?
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1) Increased heat production
2) Absorption of environmental heat 3) Impaired heat loss 4) Drugs & toxins |
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Explain the increase in body temperature with exercise.
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-Elevates core temp when production exceeds heat loss
-proportional to exercise intensity -increases core temp for several hours -temp increases>4F occur in severe ambient temperatures or w/ failure of heat loss mechanisms |
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What is the best way to improve thermoregulation capabilities?
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Training is the major stimulus
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What are 4 ways that training allows for improved thermoregulation?
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1) Decreased heat production and storage
2) More rapid sweating 3) Improved cardiovascular stability in the heat 4) Lower sweat [Na+] |
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How does age affect thermoregulation?
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Older mares reach high core temperature in half the time of younger mares
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What is malignant hyperthermia?
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hereditary defect of the ryanodine receptors
-horses, humans, pigs, dogs |
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What triggers malignant hyperthermia?
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Exposure to halogenated anesthetics or muscle relaxants
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What is the physiology behind malignant hyperthermia?
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-excessive Ca2+ release within the muscle cell
-uncontrolled contraction and metabolism -Marked increase in heat production and temp |
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What animals are at risk of heat stroke?
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Dogs and ruminants
-horses undergoing prolonged exercise in hot and humid conditions |
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What is the physiology behind heat stroke?
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High ambient temperatures and/or humidity--> heat accumulation > heat loss
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How does tissue death result from heat stroke?
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Cellular O2 consumption increases 10% for every degree celsius increase in body temperature
->105.8F oxygen use exceeds supply and tissue death occurs |
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What happens when temperatures reach > 107 degrees fahrenheit? What are the 3 sequelae?
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Control measures fail
-peripheral vasoconstriction -decreased blood pressure -decreased cardiac output |
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What are 5 conditions that can result secondary to heat stroke?
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1) lethargy & shock
2) DIC 3) Liver and kidney damage 4) Myocardial damage 5) Rhabdomyolysis * |
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What is anhidrosis?
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Loss of the ability to sweat
-can be an immune mediated condition that attacks sweat glands |
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What animals are affected by anhidrosis?
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Horses moved from temperate to hot and humid environments
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What are 3 signs of anhidrosis in horses?
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Decreased performance
Thin, patchy hair coat Increased respiratory rate |
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How do you diagnose anhidrosis?
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Injection of epinephrine or terbutaline and observe the size of the sweat patch
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Damage to the temperature regulating regions of the _______ can alter body temperature.
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Hypothalamus
-usually results in increase |
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What are 4 causes of nervous system disease that results in damage to the temperature regulation region of the hypothalamus?
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1) Brain hemorrhage or space occupying masses
2) Infectious or inflammatory disease 3) Degenerative disease 4) Brain surgery in the region of the hypothalamus |
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A central loss of temperature control is characterized by what 4 things?
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1) Lack of diurnal variation
2) Absence of sweating 3) Resistance to anti-pyretic drugs 4) Excessive response to external cooling |
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What is a fever?
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Hypothalamic set point for core body temperature is raised and defended by the same mechanisms that maintain core temperature in healthy animal
-shivering, vasoconstriction |
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Fever is caused by exogenous pyrogens that attach to membrane receptors and cause blood and tissue monocytes to release _______ (+ other cytokines)
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IL-1**
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What does IL-1 do in terms of fever?
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Elevates the hypothalamic set point --> stimulates heat conservation and production
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How do NSAIDs decrease fever?
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IL-1 likely acts in part by producing prostaglandins so it inhibits fever, but doesn't affect a normal animal
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What 3 molecules are pyrogens?
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1) Proteins
2) Breakdown products of proteis 3) LPS from bacterial cell membranes |
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How is a fever triggered on the microscopic level?
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Pyrogens (protein, LPS, etc) are phagocytosed by WBCs which release IL-1
-IL-1 increases body temp w/ in 8-10 minutes |
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What are 7 benefits of fever?
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1) Increased survival
2) Enhanced host defenses -greater Ab production 3) Lymphocyte proliferation, phagocytes, interferon 4) Hypoferremia -inhibits bacterial access to host iron stores 5) Inhibits growth of certain tumours 6) Inhibits growth of some microbes 7) Useful in monitoring disease, treatment response |
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What are 4 disadvantages of fever?
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1) Increase in temp above 5 degrees F may reverse any beneficial effects
2) Protein loss 3) Reduced ability to oxidize fat w/ preferential use of m. proteins -anorexia & increased metabolic rate--> weakness & wasting 4) Extreme fevers can cause CV and neurologic damage |
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What is the critical body temperature for a cat, dog, horse and cow?
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Cat & dog: 106 F
Horse> 105 F Cow > 107 F |
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What are 5 causes of fever?
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1) Infectious disease
2) Neoplasia 3) Noninfectious inflammation -tissue trauma 4) Immune mediated disease 5) Administration of blood components 6) Drug fever 7) Toxins 8) metabolic causes 9) Liver disease |
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What are 2 ways that neoplasia can cause fever?
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-related to secondary infection
-paraneoplastic syndrome: unexplained fever that coincides w/ tumor growth or elimination Fever of unknown origin caused by cancer in up to 40% of people |
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What are 2 immune mediated diseases that cause fever?
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Purpura
Systemic lupus erythmatosus |
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What is the most common complication of administration of blood components?
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Fever
-infectious, immunologic and hemolytic causes -may be first sign of severe reaction |
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What are 3 causes of "drug fever"?
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1) Immune mediated
-lymphocytes produce substances that reset hypothalamic thermostat 2) Bacterial pyrogens (poorly prepared injections) 3) Excessive dosing of certain drugs |
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What is a drug fever?
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it will be a sustained high temperature e.g. horse may look fine with temp of 103
-not in line w/ clinical appearance |
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How does excessive dosing of certain drugs cause a drug fever?
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Uncouple oxidative phosphorylation and energy is dissipated as heat rather than tripped in PO4 bonds
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Does liver disease cause a sustained fever?
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NO, intermittent pyrexia
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What are 2 ways that liver disease causes fever?
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1) Infectious disease w/ release of toxins or host response to infection
2) Severe hepatic disease or PSS decreases Kuppfer cell function (foreign substances enter blood and cause endogenous pyrogen production) |
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What are 3 components of treating fever?
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1) NSAIDs
-block endogenous pyrogens -inhibit prostaglandin production 2) Other antipyretics 3) Artificial cooling - |
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When is artificial cooling a very important component of fever treatment? What are 3 components of performing artificial cooling?
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Important w/ heat stroke or very high fevers
-wet animal, apply ice to head -alcohol baths and fans -cold water per rectum |
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What is a fever of unknown origin?
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Febrile episodes of > 3 weeks w/ no diagnosis after a week of routine diagnostics
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How do you diagnose a fever of unknown origin?
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-chart fever
-examine history -thorough physical exam -appropriate diagnostic tests |
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What are some patterns of intermittent fever?
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Diurnal
peaking late afternoon -pyrogenic infections, occassionally neoplasia |
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What is a remittent fever?
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Cyclical periods of days of fever
-specific infectious diseases -brucellosis, EIA |
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What are 2 causes of sustained fever?
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Drugs and toxins
-animals otherwise bright and alert and eating |
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When you have a fever of unknown origin what should you look for on the blood work?
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1) Infection /inflammation or blood borne parasites
2) WBC, fibrinogen, globulin 3) Body cavity examination -centesis, ultrasound, rads |
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Explain how to collect blood for a blood culture?
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Discontinue antibiotics 48-72 hours prior
-3-5 samples at least 45 minutes apart -Place directly into culture media -samples just before and during fever |
