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Anesthesia > Pathophysiopathy of anesthesia: cardiovascular and other systems > Flashcards

Pathophysiopathy of anesthesia: cardiovascular and other systems Flashcards

1
Q

Medulla

A

-controls sympathetic and parasympathetic NS output
>receives feedback from various systems to maintain appropriate CO

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2
Q

Sympathetic NS

A

-release catecholamines (EPI/NE)

-changes mainly affects arteries, arterioles, great veins

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3
Q

Parasympathetic NS

A

-Release Ach
-Changes mainly affects cardiac rate and rhythm

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4
Q

Ultra short Acting BP control- autoregulation

A

**Basal vasomotor control
NOTE: not affected by anesthesia, but can by disease

-Organs sense tissue oxygen demands= increase/decrease blood flow to match

-Sense accumulation of K, H, CO2, adenosine, lactate

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5
Q

Ultra short Acting BP control- endothelium derived factors

A

-Local vasodilators: NO, PGI2

-Local vasoconstrictors: endothelins, thromboxane A2

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6
Q

Short term BP control

A

**Reflexes- important for anesthesia because reflexes are blunted by inhaled and injectable anesthetic drugs

  1. Baroreceptor reflex
  2. Chemoreceptor reflex
  3. Bainbridge reflex
  4. Frank-Starling relationship
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7
Q

Baroreceptor reflex

A

-stretch receptors in carotid sinus and aortic arch
-sense changes in BP and result in changes in HR

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8
Q

Chemoreceptor reflex

A

-Carotid and aortic bodies: perfusion, CO2, O2 blood levels and blood pH

-Feedback to brainstem to adjust ventilation and sympathetic activity

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9
Q

Bainbridge relfex

A

-stretch receptors in R atrium

-sense increased pressure in the right atrium (increased venous return) and results in increased HR

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10
Q

Frank-Starling Relationship

A

-increased venous return stretches myocardium

-leads to increase myocardial contractility and increased SV

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11
Q

Tissue perfusion pressure

A

Perfusions pressure is what provides adequate blood flow to tissues
-MAP minus pressure within the tissues
-MAP >60mmHg to provide adequate tissue blood flow to major organs

**Changes in perfusion pressure leads to immediate effects on organ function

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12
Q

Brain perfusions

A

Cerebral perfusions pressure (CPP)= MAP- intracranial pressure (ICP)

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13
Q

Kidney perfusion

A

Renal perfusions pressure= MAP- glomerular capillary pressure

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14
Q

Regulation of brain and kidney perfusion

A

Autoregulation zone= range of MAP where organs maintain perfusion pressure to optimize tissue perfusion

-Map< 60mmHg = results in being outside autoregulatory zone, perfusion becomes dependent on systemic BP

GOAL: maintain MAP >60mmHg

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15
Q

Coronary artery perfusion

A

Myocardial perfusion occurs in diastole= depends on diastolic arterial pressure (DAP)

**Coronary artery perfusion=DAP- right arterial pressure

DAP<40 = reduced coronary artery perfusions (<20mmHg) leading to myocardial ischemia

GOAL: maintain DAP >40mmHg

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16
Q

Anesthesia effects on vasculature (vasodilators)

A

Reduce systemic vascular resistance

  1. inhaled anesthetics= dose dependent decrease in SVR. increasing with depth of anesthesia
  2. Acepromazine= alpha 1 adrenergic blockade causes decrease in SVR
  3. Meperidine/morphine IV= histamine released leading to vasodilation
  4. Propofol and alfaxalone= preferential venodilation. Seen after IV boluses

**Effects are additive when used together

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17
Q

What can anesthesias vasodilator effects cause?

A

Hypotension

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18
Q

Anesthesia effects on vasculature (vasoconstrictors)

A

Increase SVR
1. alpha 2 adrenergic agonists= direct action on peripheral alpha 2 adrenergic receptors causing SVR
2. Ketamine and NO= sympathomimetic action that released endogenous catecholamines which increase SVR

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19
Q

What can anesthesias vasoconstrictors effects cause?

A

Can lead to hypertension
*often seen in premedication, but is ultimately reduced by inhaled anesthetics under general anesthesia

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20
Q

Which drugs have minimal effects on vascular?

A

-Opioids and benzodiazepines

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21
Q

Epidurals

A

Local anesthetic can travel to thoracic region of spinal cord= block sympathetic vasomotor nerves

Can result in:
-reduced sympathetic control on vasomotor tone= vasodilation and decreased SVR
**compounded by other vasodilatory anesthetic drugs

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22
Q

How to avoid epidural effects?

A
  1. lowest volume to provide adequate nerve blockade
  2. Slow injection speed= reduced injection pressure to slow forward spread which also prevents bradycardia

Note: effects are temporary but extra case should be taken with large animals (horses can drop!)

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23
Q

Drugs decreasing contractility

A

-inhaled anesthetics, alfaxalone, propofol= decreased Ca availability
-Acepromazine and alpha2 agonists

**dose dependent effects

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24
Q

What other states can reduce contractility?

A

-Hypoxemia
-depleted catecholamines (sepsis)
-Acidosis (pH <7)
-Electrolyte imbalances (increased K, decreased Ca)
-Hypovolemia

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25
Q

Stages of hypertension

A

Prehypertension (SAP 140-150mmHg)

Hypertension (SAP> 160-179 mmHg)

Severe Hypertension (SAP>180mmHg)

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26
Q

Acute hypertension

A

Can lead to a decreased in CO, edema, hemorrhage (brain/lungs)

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27
Q

Sustained hypertension

A

Results in myocardial remodeling, retinopathy, retinal detachment, encephalopathy, renal disease

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28
Q

Treatment of hypertension

A

**depends on underlying reason

  1. due to Sympathetic activation- light plane of anesthesia, nociception, hypercapnia, hypoxemia
  2. due to Diseases- chronic kidney disease, hyperadrenocorticism, hyperthyroidism, pheochromocytoma
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29
Q

Stage of Hypotension

A

**most commonly seen under anesthesia
SAP< 80mmHg, MAP <60 mmHg, DAP < 40 mmHg

Results in reduced vital organ perfusion and O2 delivery

30
Q

What is significant hypotension?

A

Take into account:

  1. Severity
    -Mild/moderate MAP <60 mmHg
    -Severe MAP <35-45 mmHg
  2. Time frame
    How quickly is it falling? How long are thye hypotensive?
31
Q

Sequelae of hypotension

A

-renal damage and poor urine production
-hepatic and GI damage
-increased lactate concentration
-myocardial ischemia, arrhythmias, cardiac arrest

32
Q

Heart rate and rhythm control

A

Controlled by electrical activity balance of autonomic nervous system

33
Q

Parasympathetic impact on heart rhythm

A
34
Q

Sympathetic impact on heart rhythm

A
35
Q

Bradycardia

A

Less than half the resting normal heart rate

Dogs <50bpm
Cats <90 bpm

Bradyarrhytmias= increased parasympathetic tone (usually drug or disease induced)

36
Q

Tachycardia

A

Dogs >180 bpm
Cats >200 bpm

Tachyarrhythmias= incrased sympathetic tone (nociception, anxiety, hypercapnia, hypoxemia, hypovolemia, drugs)

37
Q

Xylazine and ketamine effects on heart rhythm

A

Stimulate alpha and beta 1 receptors= tachyarrhythmias

38
Q

Opiods and alpha 2 adrenergic agonists effect on heart rhythm

A

increase vagal tone =bradyarrhythmias

39
Q

Acepromazine effect on heart rhythm

A

Anti arrhythmic

40
Q

What drugs have minimal to no effect on rhythm of heart?

A

-inhalant anesthetics (until deep plane reached)
-propofol, alfaxalone
-benzodiazepines

41
Q

Monroe-Kellie Doctrine

A

Cranium= brain + blood +CSF

If one increases, one of others must decrease

42
Q

Cerebral metabolic rate

A

Determines cerebral blood flow (including internal carotid, vertebral arteries, circle of willis)

43
Q

How is Cerebral blood flow regulated?

A
44
Q

What does neuronal function depend on?

A
45
Q

Inhaled anesthetics on CNS

A

Decreases CMR by 60%
-dose dependent effects on CBF due to blunting autoregulation
*minimal changes= <1.0 x MAC
*Direct cerebral vasodilation= >1.0 x MAX= increase in CBF and ICP

46
Q

Ketamines effect on CNS

A
47
Q
A
48
Q
A
49
Q
A
50
Q

Cats unique blood flow

A

-Cortex and retinal blood supply is mainly due to maxillary artery. None from vertebral artery

-Use of spring loaded mouth gags to keep jaws open. This was causoing compression of maxillary artery= reduced blood flow= blindness

**instead use needle caps to make small mouth gags

51
Q

Renal blood flow

A

-Receives 20-25% CO
-controlled by sympathetic NS through renal artery vasoconstriction
>vasodilation controlled by prostaglandins (COX2)
-NO parasympathetics

52
Q

Autoregulation of renal blood flow

A

Autoregulated over MAP 80-180 mmHg

-protects against hyper and hypotensive states to maintain GFR

53
Q

Importance of kidney function in anesthesia

A
54
Q

Inhaled anesthetics effects on renal system

A

Dose dependent decrease in RBF and GFR
-post general anesthesia oligouria (urine output <0.5)

55
Q

IV anesthetics, acepromazine, opioids, benzodiazepines effect on renal system

A

Minimal RBF and GFR effects

56
Q

NSAIDs effect on renal system

A

Decreasing COX-2 production of prostaglandins
-blunts vasodilation of afferent arterioles
-inhibits ability to control RBF in the face of hypotension

57
Q

Animals under anesthesia effects on renal system

A

Can see prolonged drug effects= hangover

58
Q

Hepatic system Blood flow

A

Liver recieves 25% CO= majority of blood flow from portal vein (70-75%), rest is from hepatic artery (30%)

59
Q

Importance of hepatic system during anesthesia

A

-blood reservoir
-carbohydrate metabolism
-plasma oncotic pressure (albumin and plasma proteins)
-coagulation factor production
-Xenobiotics-biotransformation and biliary excretion
-thermoregulation

60
Q

Inhalant/injectable anesthetics and sedatives effect on hepatic system

A

minimal changes in hepatic blood flow

61
Q

What causes low hepatic perfusion?

A

-increased sympathetic tone from stress
-surgical procedures near liver (up to 60% reduced blood flow)
-positive pressure ventilation (reduced venous return)

62
Q

Drugs and liver metabolism

A
63
Q

Effects of liver disease on hepatic system when under anesthesia

A

Use drugs that have reversal agents or short effects

64
Q

Premedication drugs causing vomiting

A
65
Q

Regurgitation during anesthesia

A

From decreased lower esophageal stricture pressure
-from sedatives, opioids, IV anesthetics, inhalant anesthetics, anticholinergics

66
Q

What puts animals at high risk for regurgitation?

A

-brachycephalics, ruminants, or increased intra-abdominal pressure

-high risk procedures: intra-abdominal and orthopedic

67
Q

Complications from regurgitation

A
  1. esophagitis
  2. Esophageal structure
    3.aspiration pneumonia
68
Q

Anesthesias effect on skeletal muscle

A

Disrupts normal control of blood flow and can lead to poor skeletal muscle perfusion
-Post-anesthesia myopathy or neuropathy seen in large animals, from prolonged anesthesia or hypotension
-Treatment: supportive care (fluids, analgesics, slings)

69
Q

Types of post anesthetic myopathy or neuropathy

A
  1. Compartmental (local) = local hypoperfusion (1-2 muscles)
  2. Generalized (whole body)= general hypoperfusion (many muscles)
70
Q

Support and positioning during anesthesia

A

-Best way to avoid myopathy and neuropathy
*important to remember that animals lose muscle tone under anesthesia which means they remove protective guarding at sites of injury

-ensure no strain on delicate structures (nerve plexus, eyes)

Anesthesia (24 decks)

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