Surgery - Hypotension

Front 1

Describe the diagram of blood pressure control

Back 1

Front 2

Systemic blood pressure
-define

Back 2

-pressure exerted on walls of vessels

Front 3

Blood pressure
-determined by

Back 3

-cardiac output
-systemic vascular resistance
-total blood volume

Front 4

Blood pressure =

Back 4

= (CO x Systemic vascular resistance) + central venous pressure

Front 5

Mean arterial pressure (MAP) is representative of:

Back 5

-tissue perfusing pressure

Front 6

Mean Arterial Pressure (MAP) is determined by:

Back 6

-volume of blood within the arterial system at any point in time

Front 7

MAP is stable when:

Back 7

-when CO = peripheral run-off

Front 8

Total peripheral resistance =

Back 8

= MAP / peripheral run-off

Front 9

Effect of CO inrease and SVR remaining the same:

Back 9

-arterial blood volume rises and MAP rises

Front 10

Peripheral run-off occurs when?

Back 10

-diastole

Front 11

Equation for caluculating approximate MAP

Back 11

MAP = Pdias + 1/3 (Psys - Pdias)

Front 12

Hypotension
-MAP

Back 12

< 60 mmHg

Front 13

Hypotension
-MAP for acute renal injury

Back 13

< 55 mmHg

Front 14

Hypotension
-systolic BP

Back 14

< 90 mmHg

Front 15

Systolic BP measured how?

Back 15

-doppler

Front 16

When is hypotension common in cats and dogs?

Back 16

-during anesthesia

Front 17

Blood pressure depends on:

Back 17

-total blood volume
-cariac output
-systemic vascular resistance

Front 18

Hypotension
-causes

Back 18

-hypovolemia due to hemorrhage or dehydration
-total blood volume redistribution due to change in positioning or disease processes (GI sequestration, endotoxemia)
-Reduced cardiac output caused by heart disease, arrhythmias
-Reduced SVR due to loss of sympathetic tone caused by drugs (sympatholytics, inhalants, local anesthetics)
-reduced SVR due to vasodilation caused by sepsis or anaphylaxis

Front 19

Cardiac output =

Back 19

= HR x SV

Front 20

Stroke volume is a function of:

Back 20

-preload
-afterload
-contractility

Front 21

Hypotension
-treatment is most effective when:

Back 21

-directed toward the root cause of the problem

Front 22

Hypovolemia
-define

Back 22

-inadequate circulating blood volume

Front 23

Hypovolemia
-causes

Back 23

Decreased preload state
-hemorrhage
-acute GI loss (vomiting, diarrhea)
-dehydration

Front 24

Relative hypovolemia may occur due to:

Back 24

-presurgical fasting combined with peripheral vasodilation induced by general anesthesia

Front 25

Hypovolemia
-treatment approach

Back 25

-decrease anesthetic depth by reducing inhalant concentration
-Give IV crystalloid bolus such as LRS (3-10 mg/kg)
-repeat once if not effective the first time
-Give IV colloid such as hetastarch (2--5 mL/kg)

Front 26

Colloids
-effect vs. crystalloids

Back 26

More likely to increase MAP
Longer half life within the vascular space
-2/3 of crystalloid distribute to extravascular fluid within 60 mins

Front 27

Colloids
-typically given why

Back 27

-replace low total protein/albumin

Front 28

Hypovolemia
-treatment of severe dehydration, sepsis, acute blood loss

Back 28

Need a rapid/large volume fluid replacement
-shock dose of crystalloids at 25% dosage increments and reevaluate status
-colloid bolus as volume replacer at 5 mL/kg/hr and reassess

Front 29

Shock bolus
-dog

Back 29

-80-90 mL/kg IV

Front 30

Shock bolus
-cat

Back 30

-50-55 mL/kg IV

Front 31

Hypovolemia
-purpose of hypertonic saline

Back 31

-resuscitate rapidly at minimal volume

Front 32

Hypovolemia
-using hypertonic saline

Back 32

-4 mL/kg IV
-only sustained effect if followed by a colloid

Front 33

Hypovolemia
-replacement of blood loss

Back 33

-Crystalloids = 3x amount of blood lost

-Colloids = equal amount to blood lost

Front 34

Vasodilation
-causes

Back 34

-anesthesia
-endotoxemia
-septicemia
-adrenal insufficiency (Addisons)

Front 35

Vasodilation
-anesthetic agents

Back 35

Alpha-adrenergic agonists
-acepromazine

Isoflurane
Sevoflurane

Neuroaxial block
-local anesthetic epidural

Front 36

How does a local anesthetic epidural cause vasodilation?

Back 36

-migrates cranially in the epidural space to the thoracolumbar region
-blocks sympathetic nerve trunks ---> vasodilation

Front 37

Vasodilation
-treatment

Back 37

Administer a vasopressor
-ephedrine
-dopamine
-phenylephrine
-norepinephrine
-vasopressin

Front 38

Ephedrine
-MOA

Back 38

-indirect sympathomimetic causing NE release
-alpha and beta effects
--inc. CO and inc. vascular tone

Front 39

Dopamine
-MOA

Back 39

-dopaminergic, alpha, and bets adrenergic agonists

Front 40

Phenylephrine
-MOA

Back 40

-alpha adrenergic agonist

Front 41

Phenylephrine
-why not normally used as a vasopressor in hypovolemia

Back 41

-specific vasoconstrictor -----> dec. in tissue perfusion

Front 42

Norepinephrine
-MOA

Back 42

-alpha and beta adrenergic agonist

Front 43

Vasopressin
-indicated for use when?

Back 43

-sympathomimetic nonresponsive hypotension

Front 44

Hypotension with reduced cardiac output
-cause

Back 44

Reduced cardiac contractility
-anesthetic drug effects
-primary heart disorder

Front 45

Hypotension with reduced cardiac output
-treatment

Back 45

Administer positive inotrope
-Dobutamine
-Dopamine
-Ephedrine

Front 46

Dobutamine
-MOA

Back 46

-beta 1 & 2 receptor agonist

Front 47

Dopamine
-MOA

Back 47

-beta receptor agonist at higher range

Front 48

Ephedrine
-MOA

Back 48

-increase contractility and heart rate

Front 49

#1 Positive ionotrope to use

Back 49

-dobutamine

Front 50

Hypotension with bradycardia
-causes

Back 50

-excessive vagal tone
-other causes of bradycardia

Front 51

Hypotension with bradycardia
-treatment

Back 51

-determine other causes of bradycardia and treat
-administer anticholinergic to increase heart rate (atropine, glycopyrrolate)

Front 52

Hypertension
-pressure definition

Back 52

-dog = systolic BP > 180 mmHg

-cat = systolic BP > 240 mmHg

Front 53

Hypertension
-causes

Back 53

Physiological
-similar to causes of tachycardia
-inc. CO2
-pain
-light anesthesia

Pathological:
-chronic renal disease
-iatrogenic
-pheochromocytoma
-hyperthyroidism

Front 54

Hypertension
-treatment

Back 54

-check depth of anesthesia to make sure animal isn't too light
-administer opioids to improve pain analgesia
-make sure ventilation is adequate and CO2 absorpbant in the circle is fresh, institute IPPV if necessary
-discontinue sympathomimetics if iatrogenic cause suspected
-administer alpha-adrenergic antagonist for vasodilation
-administer beta-adrenergic antagonist to slow heart rate

Front 55

Alpha-adrenergic anatgonist for vasodilation

Back 55

-Acepromazine

Front 56

Beta-adrenergic antagonist to slow heart rate

Back 56

-Esmolol