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Flashcards in Volatile Anesthetics Deck (94):
1

The depth of general anesthesia depends on partial pressure exerted by inhalational agent in the patient's brain. This brain P depends on _______ partial pressure which depends on _________ partial pressure which depends on partial pressure of agent in the inspired gas.

Arterial
Alveolar

2

What is the path an inhalational agent takes from the vaporizer to the brain?

Vaporizor->circuit->Lungs->Blood->Brain
and then it goes back out

3

What is Relative affinity of an anesthetic for two phases and therfore the Partitioning of that anesthetic between the two phases is called...

Solubility

4

In a mixture of gases, each gas has a ______ ______ which is the pressure which the gas would have if it alone occupied the volume.

Partial pressure

5

What factors can we change to influence the amount of Inspired agent?

increase concentration
Increase FGF
(decrease the volume of the circuit and decrease the absorption by the machine are also listed but these are difficult to change)

6

What is a formula that describes alveolar partial pressure?

Input into alveoli - uptake into blood

7

How can we increase PA?

Increase ventilation
Increase concentration

8

What are two ways to increase initial concentration and uptake?

Concentration effect
Second gas effect

9

What is the definition of concentration effect?

Impact of the inspired partial pressure of the agent increases the rate of rise of the partial pressure of the alveolus
(the higher the concentration of gas used the faster the alveolar concentration of that gas....or.... At 100 percent inspired concentration, the uptake of anesthetic creates a void, which draws gas down the trachea. This additional inspiration replaces the gas taken up.)

10

what is the second gas effect

High volume of uptake of one gas accelerates the rate of increase of the PA of the companion gas
(During induction of general anesthesia when a large volume of nitrous oxide is taken up from alveoli into pulmonary capillary blood, the concentration of gases remaining in the alveoli is increased.)

11

What three factors affect anesthetic uptake?

Solubility, cardiac output, alveolar-venous difference

12

What is the formula for uptake?

Uptake = soulbility x CO x (PA-PV)

13

RElative affinity of inhale anesthetic for two phases at equilibrium?

Solubility

14

What happens to ithe PA/PI rise if soulbility is increased? How would this affect induction?

decreases PA/PI making induction slower, Halothane is given as the example for this

15

Rank the Partition coefficients from lowest to highest of Halothane, Sevoflurane, Desflurane, Nitrous Oxide and Isoflurane.

Desflurane (0.42)

16

The more soluble an anethesthetic agent is in the blood, the _____ the drug goes into the body, and the ________ the patient becomes anesthetised.

Faster
Slower

17

How can you compensate for a more soluble agent to speed induction?

YOu can increase concentration, but it there are limits

18

Increased cardiac output has what effect on the rate of rise in PA/PI?

decreases

19

Increased cardiac output is more a concern for (soluble/insoluble) agents.

soluble. ON insoluble agents there is less of an effect

20

How does cardiac output influence its effect on uptake?

greater pulmonary blood flow remove more anesthetic and lowers PA. the alveoli will saturate faster if it is seeing less blood flow

21

What is responsible for alveolar venous difference?

absorption by the tissues

22

If gases were not absorbed by tissue what would the arterial venous difference be?

0

23

Why do muscle and fat take longer for uptake and washout of gases compared to VRG?

Less blood flow
(VRG is 10% of body mass and receives 75% of bf, whereas fat is 20% and receives only 6% of bf)

24

How do we get rid of anesthetic gases?

biotransformation (small amount)
transcutaneous loss
EXHALATION

25

Which agent is the most metabolized?

Halothane

26

Which agent is the least metabolized?

Nitrous

27

Is there a concentration effect for elimination?

no

28

What are the partial pressures in the tissue during recovery?

All tissues have varying amounts

29

What changes pharmacokinetics of inhalational agents?

Age
Lean muscle
Body fat
Hepatic function
Pulmonary gas exchang
Cardiac output

30

What MAC prevents movement in 95% of the population?

1.3

31

how does MAC change per decade?

6% decrease per decade

32

What is the definiton of MAC awake?

end tidal concentration of an anesthetic agent at which 50% of patients appropriately respond to verbal commands. It only applies to inhalation agents. ~10% of MAC

33

What may affect MAC awake?

Adjuctive needs
age
hypothermia
Sedatives

34

What is MAC bar?

concentration required to block autonomic reflexes to nociceptive stimuli.
1.3 MAC

35

What factors increase mac?

Hyperthermia
Drug-induced increase in catecholamines
Hypernatremia

36

How does chronic alcohol abuse affect MAC?

no change

37

What are some factors that may decrease MAC?

OPIOIDS
Acute alcohol intoxication
Pregnancy
Lithium
Neuraxial opioids
Others:
Pre op meds
increased age
Hypothermia
A-2 agonists
PaO2<40

38

Which inhaled anesthetics were available in 1840s?

Nitrous oxide
Ether
Chloroform

39

Which anesthetics became available in 1951?

Halothane
floroxene

40

When did isoflurane become available? Des? Sevo?

1981, 1992 and 1994

41

how do anesthetic gases affect cerebral blood flow?

Increase vasodilation, decrease vascular resistance, increase CBF and ICP

42

Which causes more CBF, halothane or isoflourane?

Halothane can increase CBF by 166%d

43

What are inhaled anesthetics effect on siezures?

They will block siezure activity

44

What is burst suppression for isoflorane?

1.5 MAC. This will sacrifice blood pressure. all volatile agents cause burst supression at >2 MAC

45

what effect do inhaled anesthetics have on CSF production?

Sevo at 1 MAC may depress CSF production by up to 40%

46

Which hair color is associated with an increased mac?

red

47

what is the maximum for inhaled anesthetics for Evoked potential?

.5 MAC

48

How do inhaled anesthetics affect EEG

all may abolish EEG activity

49

How do inhaled anesthetics affect Cerebral blood flow?

All cause it to increase

50

What affects the tissue uptake of anesthetic gases?

Tissue solubility
Tissue blood flow
Difference between partial pressure of blood and the specific tissue

51

HOw do Inhaled anesthestics affect Cerebral perfusion pressure?

All decrease

51

HOw do Inhaled anesthestics affect Intercranial pressure?

Increased in all. Halogenated agents may increase it or remain the same

52

HOw do Inhaled anesthestics affect cerebral metabolic demands?

Nitrous increase all others decrease

53

HOw do Inhaled anesthestics affect CO2 reactivity?

No change

54

What effects do volatiles have on SVR and BP

Decrease SVR and BP

55

What effect do nitrous have on BP?

No change or slight increase

56

What effect do desflurane have on HR?

Causes tachycardia (and may cause HTN) due to stimulation of SNS

57

How do Iso and Sevo cause an increase in HR?

baroreceptor mediated

58

What effects do volatile have on CO?

decrease

59

What effect does Nitrous have on CO?

slight increase due to sympathomimetic activity

60

HOw do volatiles affect PVR?

decrease

61

what is coranary steal? which agent is associated with it and why?

Coronary steal is the diversion of blood from a myocardial bed with limited or inadequate perfusion to a bed with more adequate perfusion. Isoflurane has been associated with this because it is a potent coronary vasodilator (why the others are weak coronary vasodilators). However, no studies demonstrate an increas in ischemia with the use of ISO

62

what happens with administering halothane with epinephrine?

May cause arrhythmias

63

How do inhaled anesthetics affect MAP?

Nitrous remains the same or increases. All others decrease

64

How do inhaled anesthetics affect systemic vascular resistance?

Nitrous increases. Other decrease, except sevo stays the same

65

How do inhaled anesthetics affect Heart rate?.

Increase

66

How do inhaled anesthetics affect Miocardial function?

all decrease

67

How do volatile agents affect Vt, RR and MV?

RR increases, Vt and MV decrease--rapid shallow breathing

68

at what MAC do des and Sevo produce apnea?

1.5-2 MAC

69

How do volatile drugs affect AW resistance? Which is the exception?

Decrease AW resistance, except Des

70

HOw does anesthesia affect FRC?

decreases

71

HOw do inhaled anesthetics affect the kidneys?

decrease renal blood flow, GFR and urine output. May also lead to nephrotoxicity

72

How do the inhaled anesthetics affect the liver?

decrease hepatic blood flow and clearance, and can cause hepatic toxicity

73

What effects do inhaled drugs have the uterus?

decrease uterine smooth muscle contractility and blood flow.
helpful to remove retained placenta
May increase blood loss during delivery

74

Can inhaled drugs cross the placenta?

Yes

75

What effects do inhaled drugs have on skeletal muscle?

Ether derived drugs pruduce muscle relaxation and potentiate paralytics
Nitrous does not produce relaxation and may produce rigidity

76

How do volatile anesthetics lower body temp?

Lower the core temp set point at which thermoregulatory vasoconstriction is activated
Vasodilation redistributes blood flow from central to peripheral compartments
Metcabolic oxygen consumption is decreased-decreases heat generation

77

Which produces more compound A? baralyme or soda lime?

Baralyme

78

Which volatile agent leads to carbon monoxide?

Des--from dry dessicated absorber

79

What leads to nephrotoxicity from volatiles/

an inactive flouride metabolite--methoxyflurane

80

What are the two types of halothane hepatitis?

Mild self limiting form and a more rare life threatening hepatic necrosis

81

what % of halothane is metabolized by liver?

20%

82

What is the preservative used with halothane?

thymol

83

how much of Isoflurane is metabolized?

0.2%

84

Isoflurane has ____ cardiovascular changes at 1 MAC

minimal

85

Why is isoflurane a good choice for EEG?

2 MAC = isoelectric EEG

86

What patient should you avoid use of Des?

reactive Airways

87

Is des used with LMA?

No--AW irritant

88

Which volatile agent is least AW irritant?

Sevo

89

HOw much is Sevo metabolized?

2-5%. Associated with Compound A formation and renal tubular injury

90

How does nitrous affect PVR?

increases

91

How does Nitrous affect CMRO2?

Increases

92

When shoudl nitrous be avoided?

enclosed air spaces--34x as soluble as nitrogen
Avoid with:
laparoscopic surgery
Working on bowels
Eye surgery with the gas buble

93

What is the rule for sevo at low flows?

you can use low flows for 2 MAC hours