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Module 20: Global Vet Med > Pyrexia & Fever of Unknown Origin > Flashcards

Pyrexia & Fever of Unknown Origin Flashcards

1
Q

how is body temperature controlled

A

thermoregulatory centre in the hypothalamus (the thermostat)

too hot:

panting, vasodilation, cold seeking behaviour

too cold:

piloerection, shivering, behaviour (curl up)

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2
Q

how does a true fever occur

A

A variety of stimuli including bacteria, endotoxins, viruses, immune complexes, activated complement, and necrotic tissue trigger the release of endogenous pyrogens by the phagocytic system —> mainly the mononuclear cells or macrophages

These endogenous pyrogens include interleukin-1, tumour necrosis factor (TNF), and interleukin-6

They activate prepotic nucleus of the hypothalamus, raising the set point of the thermostat by generating heat through muscle contraction and shivering, and conserving heat through vasoconstriction

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3
Q

when the hypothalamic set point is increased what is the temp

A

rarely >41C

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4
Q

what occurs when the hypothalamic set point is increased

A

body will increase metabolism to adapt to ‘new’ set point

but set point is now variable (alternating cooling and heating)

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5
Q

why are fevers beneficial

A

Fever enhances WBC activity

  • Up to a point

Fever induces acute phase proteins

  • Free radical scavenging

Fever decrease viral excretion

  • Common cold, chicken pox
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6
Q

what are the costs of fever

A

Energy

  • Fever = increased MER

Physiological processes

  • Hemoglobin oxygen dissociation

Collateral damage

WORSE clinical signs

BUT does it matter?

  • Ex. You feel better once you take an aspirin
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7
Q

what is hyperthermia

A

heat generation > heat loss

ex. heat stroke, seizure

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8
Q

is there a set point in hyperthermia

A

no set point

temp can go >41 when cells will die

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9
Q

what are risk factors do hyperthermia

A

URT disease

obesity

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10
Q

what occurs during hyperthermia

A
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11
Q

how is hyperthermia treated and what is contraindicated in these cases

A

goal is to cool 39.5C in 60-90 mins

do not cool too rapidly

  • shivering
  • peripheral vasoconstriction

Cool environment

direct cooling

  • wet towels
  • IVFT

Cardiovascular support

  • IVFT
  • hypernatremia
  • monitor urine output and BP

antibiotics, GI protectants

antipyretics contraindicated

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12
Q

what is the diagnostic approach of FUO

A

History:

  • General history
  • Environment (heat stroke)
  • In contact animals

Clinical exam:

  • Pain?
  • Lymph nodes
  • ANY mass
  • Discharges
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13
Q

what are the causes of acute pyrexia

A

less than 5 days

mild less than 40.5C

mostly infections (bacterial and viral)

others

  • drugs and vaccines
  • inflammatory disease
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14
Q

what are the first stages in a diagnosis of FUO

A

CBC

Serum biochemistry

Urinalysis

Urine bacterial culture and susceptibility

FNA of enlarged organs, masses, or swellings

Second stage:

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15
Q

what are the second stages of diagnosis of FUO

A

Thoracic radiographs

Abdominal ultrasonography

Echocardiography

Serial bacterial blood culture

Immune tests (antinuclear antibody, rheumatoid factor)

Acute phase reactant measurements (ex CRP)

Serum protein electrophoresis

Serological tests or PCR assay

Arthrocentesis (cytological studies and culture)

Biopsy of any lesion or enlarged organ

Bone marrow aspiration

Cerebrospinal fluid analysis

Leukocyte or ciprofloxacin scanning

Exploratory coeliotomy

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16
Q

what is the third stage of diagnosis of FUO

A

Therapeutic trial (antipyretics, antibiotics, corticosteroids)

17
Q

how can antibiotics be used to treat pyrexia

A

safe relative to NSAIDs/steroids

use first line antibiotics

  • Amoxicillin, ampicillin, 1st generation cephalosporins

Avoid TMPS

  • Certain dogs can have pyrexic reactions to these drugs

Avoid second line antibiotics if possible

  • Fluoroquinolones, cefovecin (convenia)
18
Q

how can NSAIDs be used to treat pyrexia and when are they use

A

Direct anti-pyretic effect

  • COX-2 inhibition at thermoregulatory centre

Useful if

  • Temp >40ºC
  • Patient showing adverse effect of fever
  • Animal that has been anorexic for 3-5 days
  • Obese patients can’t shed heat as easily
  • Brachycephalic breeds
  • Hot environment
19
Q

when should you be warely about using NSAIDs to treat pyrexia

A

Beware of

Patients with renal, GI, liver disease

20
Q

what are the risks of anti-pyretic therapy

A

Delays diagnosis

  • Proven in small animals!

Side effects of drugs

  • Gastric ulceration
  • Liver failure
  • Renal failure
  • Blood dyscrasias
21
Q

when would corticosteroids be used as anti-pyretic therapy and when should they not be

A

Same indications as NSAIDs

Maybe more effective

  • Immune mediated disease
  • Lymphoma (short term only)

But not if the patient has an infection!

  • Exclude infectious causes of pyrexia before using corticosteroids
22
Q

what are the common causes of fever of unknown origin

A

immune mediated 30-40% (esp steroid responsive meningitis-arteritis (SRMA), immune-mediated polyarthritis (IMPA)

neoplasia 20-30%

infectious 15-20%

other 7-12%

no diagnosis 20%

23
Q

what are the causes of FUO in cats

A

Different group of things associated

Feline infectious peritonitis is high on the list compared to inflammatory, neoplastic and more rare immune mediated diseases

24
Q

what is steroid responsive arteritis-meningitis

A

Head/neck pain

  • Low head carriage
  • General depression
  • Common in Springer Spaniel

Pyrexia

  • Very high
25
Q

how is SRAM diagnosed

A

CSF tap

26
Q

how is SRAM treated

A

prednisolone

27
Q

what is immune mediated polyarthritis

A

Shifting lameness — not necessarily easy to spot

General depression

Pyrexia

Joints may be swollen (not easy to tell)

28
Q

how is IMPA diagnosed

A

Diagnosed by joint taps

Do at least 6-8 taps and if all clear can rule it out

Do L+R carpi, stifle and shoulder

Elbows and hocks useful

Visual inspection of joint fluid can be he

29
Q

what are the signs of endocarditis

A

Signs

Pyrexia

Joint swelling

Arrhythmias

Murmur

30
Q

how is endocarditis diagnosed

A

blood culture

US

31
Q

how is endocarditis treated

A

aggressive long term antibacterial therapy

32
Q

assuming you have no diagnosis for a fever what should you do

A

Repeat hematology and biochemistry

  • Retroviruses, FCoV — cats
  • Tick borne diseases — dogs
  • Toxoplasma/neospora
  • Acute phase proteins

Repeat urinalysis

  • Culture (need sterile sample)
  • UTI? Pyelonephritis?

Repeat imaging

  • Thorax, abdomen and spine

Fine needle aspiration of any mass

  • Any mass!
  • Normal lymph nodes

Echocardiogram

  • Blood cultures

Joint taps

CSF taps

33
Q

describe a phased approach to a prolonged fever

A
34
Q

what are acute phase proteins and what are they useful for

A

part of innate immune system

measured in 1ml of serum

most sensitive blood test for detecting inflammation

35
Q

how are acute phase proteins produced

A

The bacteria and LPS membrane stimulate the production of inflammatory cytokines

These increase the production of proteins that are specifically there to help scavenge products of inflammation

Mop up the bad things that happen during infections

Use them to monitor response

Using the temperature or WBC are too insensitive

Module 20: Global Vet Med (21 decks)

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