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Flashcards in IV Anesthetics Deck (77):
1

How quickly must you use Propofol after opening?

6 hrs (due to emulsion amendable to bacterial growth)

2

Describe propofol metabolism

Rapid liver metabolism, inactive compound excreted by kidney

clearance > hepatic blood flow = extrahepatic metabolism

~30% metabolized in lungs

3

Typical wake up time after propofol bolus?

8-10 min (DOA 3-8 min)

4

Rapidity of wake up from propofol likely 2/2 what?

redistribution from highly perfused (brain) to poorly perfused (fat/muscle) tissues

5

Induction dose of propofol

1-2.5 mg/kg IV

6

Protein binding % of propofol

97%

7

MOA of propofol

increase chloride current via GABAa receptor

8

Major CNS effects of propofol?

- hypnotic
- decrease CBF/CMRO2/ICP/IOP

NOT AN ANALGESIC

9

CV effects of propofol (HR, SVR)

Large decrease in MAP via vasodilation (arteries and veins)

Decrease preload and afterload

Inhibits baroreflex = only small increase in HR

10

Respiratory effects of Propofol (RR, Vt, CO2/O2 response)

Induction dose = Respiratory depressant, apnea

Maintenance dose = reduce minute ventlation (decrease RR and Vt)

blunt CO2/O2 vent response

reduce upper airway responsiveness (less laryngospasm)

11

post-surgical benefit of propofol

anti-emetic

12

Pt with unexpected tachycardia during propofol anesthesia...what should you look for?

Labs- BMP

metabolic acidosis possible (propofol infusion syndrome)

13

How can you reduce injection pain with propofol?

1. pre-medicate with opioid
2. co-administer with lidocaine (50-100mg IV)
3. Dilution
4. use larger veins

14

What factors would decrease the required induction dose of propofol?

old age

pre-med with opioids/benzos

reduced CV reserve

15

What factors increase the required induction dose of propofol?

age (children need upwards of 2.5-3.5mg/kg IV)

16

Continuous propofol infusion rate for maintenance of anesthesia

100-200ug/kg/min (if combined with NO or opioids for analgesia)

17

Continuous propofol infusion rate for sedation

25-75 ug/kg/min

18

anti-emetic dosing of propofol

10-20mg IV

19

Difference between propofol and fospropofol

fospropofol (Lusedra) = water-solubule pro drug of propofol used for MAC

20

biproducts of fospropofol

propofol + phosphate + formaldehyde

21

difference between propofol and fospropofol duration

fospropofol = longer onset/ofset duration (due to prodrug form)

22

Major barbiturates used in IV induction

thiopental

methohexital

23

Major effects of barbiturates in anesthesia

hyponotic

sedative/general anesthetic

anticonvulsant

NOT AN ANALGESIC

24

Downfall of barbiturates (thopental/methohexital) re: solution

alkaline Na salt w/ pH > 10 --> precipitation with injected with acidic drugs (like neuromuscular blocking drugs)

25

Metabolism of barbiturates

exception?

hepatic metabolism via oxidation and N-dealkylation/desulfaration

exception = phenobarbital (renal excretion)

26

clearance of methohexital vs thiopental?

methohexital = more rapid than thiopental (quicker duration of action)

27

MOA of barbiturates

enhancement of inhibitor neurotransmiter (GABAa)

inhibition of excitatory transmission (unclear specific target)

28

Major CNS effects of barbiturate

Cerebral vasoconstric
Decrase CBF
Decrease ICP
Decrease CMRO2

= Flat line EEG (except methohexital = increase epileptic foci)

GREAT FOR USE IN SPACE OCCUPYING IC LESIONS

29

CV effects of barbiturates

Decrease BP (vasodilate, decrease sympathetic outflow)

compensatory increase in HR (blunt hypotension)

Decrease CO 2/2 decrease VR (pooling of blood in capacitance vessels)

30

Which patients will have exagerated CV response to barbiturates?

- hypovolemia
-cardiac tamponade
-cardiomyopathy
-CAD
- cardiac valve disease

(** can't compensate for decreased SVR with increased CO)

31

Respiratory effects of barbiturates

- resp depressant = decreased minute vent (decreased Vt and RR)

decrease vent response to CO2/O2

LESS reduction in upper airway response (don't use without NM blockers for DL)

32

Major side effects of barbiturates

1. arterial injection = pain, tissue damage from vasoconstriction

2. sub-cut injection = pain/local tissue irritation

USE DILUTE PREPS! (2.5% thiopental, 1% methohexital)

33

Induction dose of thiopental

3-5mg/kg IV

34

Induction dose of methohexital

1-1.5mg/kg IV

35

Benzos commonly used in anesthesia

diazepam, midazolam, lorazepam

36

Desired effects of benzos

anterograde amnesia
anxiolysis

= GREAT PREMEDICATION

Also- anti-epileptic

37

quickest onset benzo? why?

midazolam (versed)

most lipid soluble (rapid distribution to brain, then redistribution to inactive tissue sites)

38

MOA of benzos

activate GABAa, increase Cl current, hyperpolarize neuron, reduce excitability

most in cerebral cortex, post-synaptic nerve endings

minimal effects outside CNS

39

most potent benzo

Midazolam = higher affinity for benzo receptor (x2 diazepam)

40

CNS effects of benzos

decrease CBF and CMRO2 (less than barbs and propofol though)

ceiling effect

not neuroprotective like barbs

41

CV effects of benzos

minimal decrease in BP (Midazolam>diazepam)

worse in volume depleted patients

42

Resp effects of benzos

minimal vent depression...increased with opioids

43

Clinical uses of benzos

1. preop medication
2. IV sedation
3. IV induction of anesthesia
4. suppress seizure activity

44

Versed dosing for premedication (IV)

1-2mg IV

45

PO premedication dosing of Versed in peds

0.5mg/kg PO 30 min before induction

46

Induction dose Versed

0.1-0.3mg/kg IV

facilitate with small dose opioid (fentanyl 50-100ug IV) 1-3 min pre benzo dosing

47

Major desired effect of Ketamine

ANALGESIA

dissociative anesthesia

48

Ketamine onset, ofset

rapid, high lipid solubility

rapid, redistribution to inactive tissue

49

protein binding of ketamine

low 12% (unique)

50

Major MOA of ketamine

inhibition of NMDA receptor

51

Side effects of katamine

- open eyes, dilated, nystagmus
-lacrimation/salvation increased (premedicate with anticholinergic)

52

How can you diminish emergence reactions with ketamine?

benzos

less reactions in kids

53

CNS effects of ketamine

Vasodilate cerebral vessesls = increase CBF
Increase CMRO2

DO NOT USE IN PATIENTS IWTH INCREASED ICP/INTRACRANIAL PATH

54

CV effects of Ketamine

blunt them how?

significant/transient increase in BP, HR, CO 2/2 sympathetic outflow increase

blunt w/ opioids, benzos, inhaled anesthetics

55

Why may ketamine be a poor choice in critically ill patient?

Direct myocardial depressant

critically ill = decreased ability to increase sympathetic output = blunt increase bp/hr/co = cardiogenic shock issues

56

Respiratory effects of ketamine

No significant resp depression

large bolus doses can cause transient hypovent/short apnea

bronchodilation = good for asthma

laryngospasm possible = increased salivation (DON'T ASSUME AIRWAY IS PROTECTED)

57

Induction dose Ketamine

1-2mg/kg IV

4-6mg/kg IM

58

Maintenance dose Ketamine

Alone - 30-90ug/kg/min IV

With 50-70% NO - 15-45ug/kg/min IV

59

Analgesic dose ketamine

0.2-0.8mg/kg IV

60

Etomidate effects

hyponotic

NO ANALGESIA

61

Typical concentration of etomidate

2mg/ml solution

62

Major metabolism site of etomidate

serum esterase, excreated into urine/bile

63

Relative duration of etomidate

Dose dependent, linear

100sec unconsciousness per 0.1mg/kg given

64

MOA of etomidate

GABA like effects, potentiate GABAa receptor effects

65

CNS effects of etomidate

potent cerebral vasoconstrictor

decrease CBF and ICP

NOT NEUROPROTECTIVE

66

CV effects of etomidate

CV stability after bolus injection

BP decrease modest/absent

hypovolemia = some decrease in SVR

Minimal change in HR or cardiac contractility

67

resp effects of etomidate

resp depressant (less than barbiturates)

apnea (after bolus doses ) possible

increased resp effects w/ opioids/inhaled anesthetics

68

worrisome side effect of etomidate

adrenocortical suppression (dose dependent inhibition of AaB-hydroxylase)

lasts 4-8 hrs after induction dose

69

Induction dose of Etomidate

0.2-0.3mg/kg IV

70

What is dexmedetomidine?

highly selective alpha-2 blocker

71

Context sensitive half time of dexmedetomidine?

Significant increase w/ dose
10 min after 4 min inffusion

250min after 8hr infusion

72

MOA of dexmedetomidine?

hyponosis from stim of alpha-2 in locus ceruleus

analgesia from SC level

73

CNS effectts of dexmedetomidine?

decrease CBF

no signifcant change in ICP or CMRO2

74

CV effects of dexmedetomidine

- moderate decrease in HR and SVR

Bolus dose = transient increase in SVR, decrease HR (peripheral activation of alpha-2)

75

respiratory changes of dexmedetomidine

- small decrease in Vt
-no change in RR

76

Major uses of dexmedetomidine?

1. short term sedation for intubated/ventilated patients (ICU)
2. adjunct to general anesthesia
3. sedation for awake fiberoptic intubation
4. in conjunction with regional anesthesia

77

Dexmedetomidine dosing

0.5-1ug/kg IV (initial over 10-15 min) + infusion 0.2-0.7 ug/kg/hr