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ANESTHESIA > 22b – Pathophysiology of Anesthesia: Other Systems > Flashcards

22b – Pathophysiology of Anesthesia: Other Systems Flashcards

1
Q

Monroe-Kellie Doctrine (CNS)

A
  • Cranium=brain (80%) + blood(10%) + CSF (10%)
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2
Q

Cerebral metabolic rate determines

A
  • Cerebral blood flow
    o Blood supply=internal carotid, vertebral arteries, circle of Willis
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3
Q

What is the cerebral blood flow range?

A
  • Autoregulated over MAP 50-150mmHg to maintain perfusion based on CMR
    o Outside of range=CBF depends on systemic BP
  • *CBF also changes with PaCO2 and PaO2 levels
    o Prolonged hypoperfusion=severe neurological deficits
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4
Q

What do inhaled anesthetics do to CMR?

A
  • Decreases it by 60%
    o Dose-dependent due to blunting autoregulation
    o <1.0 MAC=minimal changes
    o >1.0 MAC=direct cerebral VASODILATION=increased CBF and intracranial pressure
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5
Q

What does ketamine do to the CNS?

A
  • Increase CMR and CBF
  • Mitigated by GABA agonists like diazepam)
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6
Q

What does propofol and alfaxalone do to the CNS?

A
  • Mild decrease in CMR and CBF
  • *maintains autoregulation=GREAT for patients with neurological disease
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7
Q

What do opioids, benzodiazepines, alpha2-adrenergic agonists do to CNS?

A
  • Minimal changes
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8
Q

What does acepromazine do to CNS?

A
  • Increased CBF and intracranial pressure from vasodilation
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9
Q

Cats have a unique blood flow

A
  • Cortex and retinal blood supply=mainly from maxillary artery (branch of external carotid)
  • No collateral blood supply be vertebral artery
  • *careful with mouth gags!
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10
Q

Spring loaded mouth gags for cats

A
  • Jaws help open (>42mm) for prolonged time
    o Compressed maxillary artery=brain does not receive blood flow=BLINDNESS (temporary or permanent)
  • *use smaller mouth gags (<20-30mm)
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11
Q

Renal system review

A
  • Receives 20-25% CO
  • Renal blood flow (RBF) mainly controlled by SNS through renal artery vasoconstriction!
    o Vasodilation controlled by prostaglandins (COX-2)
    o NO PNS innervation
  • RBF autoregulated over MAP 80-180mmHg
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12
Q

Kidney functions that are important for anesthesia

A
  • Fluid, electrolyte and acid-base balance
  • BP (RAAS)
  • Excretion of waste products and drugs
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13
Q

What do all inhaled anesthetics do to the renal system?

A
  • Dose-dependent decrease in RBF and GFR
    o Post-general anesthesia oliguria (increases over time)
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14
Q

What do IV anesthetics, acepromazine, opioids and benzodiazepines do to renal system?

A
  • Minimal RBF, GFR effects
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15
Q

What do alpha2 adrenergic agonists do to renal system?

A
  • 30% decreases RBF but maintain GFR
    o Promotes diuresis (ADH suppression)
  • *catheter in horses=always
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16
Q

What do NSAIDs do to renal system?

A
  • Decrease COX-2 production of prostaglandins =blunts vasodilation of afferent arteriole
    o *Inhibits ability to control RBF in face of hypotension
17
Q

What can renal disease do with anesthesia?

A
  • Can see prolonged drug effects=’hangover’
18
Q

Hepatic system review

A
  • 25% of CO
    o Majority from portal vein (70%) and hepatic artery (30%)
19
Q

What parts of the hepatic system are important for anesthesia?

A
  • Blood reservoir
  • CHO metabolism
  • Plasma oncotic pressure
  • Coagulation factor production
  • Xenobiotics biotransformation and biliary excretion (drug metabolism and exertion)
  • Thermoregulation
20
Q

What do inhalant/injectable anesthetics and sedatives do to the hepatic system?

A
  • MINIMAL hepatic blood flow
21
Q

What can cause low hepatic perfusion?

A
  • Increased sympathetic tone (stress)
  • Surgical procedures near liver (up to 60% reduced blood flow)
  • Positive pressure ventilation (reduces venous return)
22
Q

All drugs undergo some degree of liver metabolism (liver disease)

A
  • Relay on biotransformation and biliary excretion
  • *if liver failure/injury=hangover!
    o Use drugs with reversal agents or short effects
23
Q

What drugs cause dogs to vomit?

A
  • Mu-opioids
    o Hydromorophone
    o Morphine
24
Q

what drugs cause vomiting in cats?

A
  • Alpha2 adrenergic agonists
    o Xylazine
    o Dexmedetomidine
25
Q

What are some drugs with anti-emetic effects?

A
  • Acepromazine
  • Maropitant
26
Q

What species are at risk of post-operative nausea and ileus?

A
  • Rabbits, horses, ruminants
  • *many drugs implicated
    o Interrupt normal intestinal function/motility
27
Q

Anesthesia can cause regurgitation during anesthesia from

A
  • Decreased lower esophageal sphincter pressure
28
Q

What drugs can cause regurgitation during anesthesia?

A
  • Sedatives
  • Opioids
  • IV anesthetics
  • Inhalant anesthetics
  • Anticholinergics
29
Q

What patients are at high risk of regurgitation during anesthesia?

A
  • Brachycephalic breeds
  • Ruminants
  • Increased intra-abdominal pressure
30
Q

What are high risk procedures for regurgitation during anesthesia?

A
  • Intra-abdominal
  • Orthopedic
31
Q

What are some complications with regurgitation during anesthesia?

A
  • Esophagitis
  • Esophageal structure
  • Aspiration pneumonia
32
Q

What does anesthesia do to skeletal muscles?

A
  • Can lead to poor skeletal
  • *can get post-anesthetic myopathy or neuropathy
    o Mostly in large animals (if over 2hrs or hypotension)
33
Q

What are 2 types of post-anesthetic myopathy or neuropathy?

A
  • Compartmental (localized): local perfusion, 1-2 muscles
  • Generalized (whole body): generalized hypoperfusion, many muscles
  • *difficulty or inability to stand during recovery
34
Q

How do you treat post-anesthetic myopathy or neuropathy?

A
  • Supportive care
    o Fluid
    o Analgesics
    o Slings
35
Q

What is the major cause of myopathy or neuropathy?

A
  • Poor positioning/padding during anesthesia
36
Q

What does lose of muscle tone under anesthesia remove?

A
  • Protective guarding to sites of injury
    o Provide support to whole body! (especially injuries)
    o Positioning=ensure no strain on delicate structures

ANESTHESIA (27 decks)

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