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A&P Texas Wes > Pharm Induction Drugs > Flashcards

Pharm Induction Drugs Flashcards

1
Q

Methohexital
(brevital) & Sodium Pentothal
(thiopental/ pentothal)

Structure/Composition

A

‣ S (-) isomer much more potent than R (+) but are marketed only as a Recemic mixture

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2
Q

Propofol

Structure/composition

A

Constitution of 1% Propofol (10 mg/ml)
‣10% soy bean oil
‣ 2.25% glycerol
‣ 1.2% purified egg phosphatide (lecithin)
Found in yolks
PROBLEMS: ↑ bacterial growth, ↑ triglycerides in prolonged gtts, pain on injection

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3
Q

Etomidate

Structure/Composition

A

Only carboxylated imidazole containing compound

35% propylene glycol

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4
Q

Ketamin

Structure/Composition

A

Phencyclidine Derivative (PCP)
“angel dust”

Preservative: Benzethonium Chloride, inhibits nicotinic ACH receptors which causes SNS stimulation → CV consequences

S (+) Ketamine: More analgesia than R isomer (2x greater than racemic and 4x greater than R (-), ↑ metabolism and recovery, less salivation, Lower incidence of emergence delirium
R (-) Ketamine: Inhibits uptake of catecholamines into the postganglionic nerve endings (cocaine like effect), Less fatigue, Less cog impairment

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5
Q

Structure/Composition
Summary of Induction drugs

A

BARBS and ketamine are racemic mixtures
Propofol and Etomidate both burn on injection d/t propylene glycol
Ketamine also has preservative but it causes SNS stimulation

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6
Q

Methohexital Category

A

Oxybarbituate

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7
Q

Sodium Pentothal (thiopental/pentothal)

Category

A

Thiobarbituate

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8
Q

Barbiturates MOA/Receptor

A

‣Potentiate GABAachannel activity ; directly mimics GABA
‣Acts on glutamate, adenosine, and neuronal nicotinic acetylcholine receptors.

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9
Q

Propofol MOA/Receptor

A

GABAa Receptor agonist
↑ Cl- conductance to produce hyperpolorization of postsynaptic membrane

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10
Q

Etomidate MOA/Receptor

A

Selective modulator of GABAa Receptor

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11
Q

Katamine MOA/Receptor

A

Non- competitive binding to N-methyl-D- Aspartate (NMDA)
Opioid receptors (mu, kappa, delta, and weak sigma)
GABA a (weak)
and LOTS of others…

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12
Q

Induction Drugs Receptor Summary

A

All effect GABAa
KETAMINE has lots of active sites

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13
Q

Indication for Barbiturates

A

PREVIOUS USES:
‣Premedication for hangovers
‣ Grad-mal seizure (use benzo now)
‣ Rectal Admin for young/ uncooperative (but now we use PO versed)
‣Increased ICP, cerebral protection, induction

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14
Q

Indication for propofol

A

1.induction drug of choice
2. PONV and CINV
2. Continuous gtt: Propofol only or TIVA w/ other anesthetic drugs, ICU 2% solution to ↓ lipids admin.
3. Agent of choice in brief GI endoscopy procedure
4. Mechanical ventilation in ICU/post-op
5. Antipruritic effects
6. Anticonvulsant

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15
Q

Indication for Etomidate

A

Induction

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16
Q

Indication for Ketamine

A
  1. induction
  2. Withdrawals (potential for abuse tho)
  3. Good for hypovolemic pt. d/t SNS effects
  4. Asthmatics and MH d/t bronchodilator effects
  5. CAD cocktail (see PP slide 30)
  6. Peds / uncooperative pt : IM
  7. Burn dressing changes, debridement, skin grafts
  8. Reversal of opioid tolerance
  9. Psych disorders
  10. Restless leg syndrome (PO dose)
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17
Q

Dose Considerations Barbs

A

Dosed on LEAN body weight: use IBW

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18
Q

Dose Considerations Propofol

A

PEDS: ↑ dose d/t larger distribution volume and clearance rate.
Elderly: ↓ dose 25-50%
Conscious Sedation:
‣ min. analgesia, amnesia, anticonvulsant, prompt recovery w/o residual sedation, ↓ PONV, use Versed or Opioid as adjunct,

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19
Q

Dose Considerations Etomidate

A

Rapid IV injection -> apnea

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20
Q

Dose Considerations Katamine

A

Induction: ↑salivation,
‣give antisialogogue Glycopyrrolate (0.2 mg) > atropine/scoplamine
‣ Give versed IV 5 minutes prior to inhibit SE of emergence delirium

LOC effect: 30 secs – 1 min (IV); 2 to 5 mins (IM)
Return of consciousness (ROC): 10 to 20 minutes
Full consciousness: 60 to 90 minutes.
Amnesia persists after ROC: 60 to 90 minutes

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21
Q

Dose Methohexital

A

IV 1.5 mg/kg
PR (rectal-kids): 20-30 mg/kg
IV gtt: post-op seizure activity in 1 of 3 patients - lowers the threshold (used in ECT)

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22
Q

Dose Sodium Pentothal
(thiopental/ pentothal)

A

IV: 4 mg/kg
***re-dose after 30 min d/t rapid redistribution

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23
Q

Dose Propofol

A

Induction: 1.5 -2.5 mg/kg ( ↑PEDs, ↓old)
Conscious Sedation: 25 -100 mcg/kg/min
Maintenance: 100 - 300 mcg/kg/min
*** rapid injection= LOC in 30 sec
PONV/ Sub-hypnotic dose: 10-15 mg IV followed by 10 mcg/ kg/min
Antipruritic: 10 mg IV
Anticonvulsant: 1 mg/kg IV

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24
Q

Dose Etomidate

A

IV: 0.3 mg/kg (0.2-0.4)mg

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25
Q

Dose Ketamine

A

INDUCTION: 0.5 -1.5 mg/ kg IV or 4-8 mg/kg IM
Maintenance and sub anesthetic dose: 0.2-0.5 mg/kg IV
Post op sedation and analgesia:
1-2 mg/kg/hr (also used for ped heart case)
Neuraxial analgesia:
Epidural: 30 mg
intrathecal/spinal/ subarachnoid: 5-50 mg

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26
Q

Barbiturates Onset

A

Rapid: 30secs

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27
Q

Propofol Onset

A

*** rapid injection= LOC in 30 sec

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28
Q

Etomidate Onset

A

within 1 min IV

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29
Q

Ketamine Onset

A

Onset: 1 min IV, 5 min IM
Duration : 10-20 min

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30
Q

Redistribution Barbs

A

Rapid redistribution from brain to other tissues
‣after 5 min 1/2 dose available in brain
‣ at 30 minute, 10% of original dose available in brain

‣Initial redistribution to skeletal muscles
‣ Takes 15 minutes to reach equilibrium b/w skeletal
muscles and plasma
‣↓redistribution
‣in shock (↓perfusion)
‣ elderly & women ( ↓ muscle mass)
‣ Drug stored in fat, so redosing and large dosing can have cumulative effects

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31
Q

Barbs context sensitive half-life

A

Prolonged infusion = lengthy , any drug with large redistribution

32
Q

Propofol Context sensitive half-life

A

40 minutes (on 8hr infusions)
Shorter than all barbs, not as lipid soluble

33
Q

Barbs Half-time

A

E 1/2 time of Thiopental > Methohexital
Peds: Short half-time d/t ↑ metabolism

34
Q

propofol half-time

A

0.5-1.5 hrs

35
Q

Etomidate half-time

A

2-5 hrs

36
Q

Ketamine half-time

A

2-3 hrs

Return of consciousness (ROC): 10 to 20 minutes

37
Q

Protein Binding Induction Drugs

A

Barbs: 70-85%
Etomidate: 76%
Ketamine: none

38
Q

Induction Drugs Vd

A

Propofol: 3.5-4.5L/kg
Etomidate: Large
Ketamine: 3L/kg

39
Q

Barbs Ionization

A

Methohexital: normal pH 76% non-ionized

Sodium Pentothal
(thiopental/ pentothal): normal pH, 61% non-ionized

40
Q

Barbs Lipid solubility

A

Methohexital <Sodium Pentothal
(thiopental/ pentothal)

41
Q

Etomidate Lipid Solubility

A

Water soluble at acidic pH, lipid soluble at physiologic pH

42
Q

Ketamine Lipid Solubility

A

(5x to 10x than Thiopental)
Brain -> not plasma bound -> distributed to tissues

Largest

43
Q

Barbs Metabolism

A

99% hepatocytes

Methohexital: Faster metabolism than thiopental and more rapid recovery from induction

44
Q

Etomidate Metabolism

A

Hydrolysis hepatic microsomal enzymes
‣ Plamsa esterases

45
Q

Propofol Metabolism

A

Hepatic: CYP 450
Metabolites: Water soluble sulfate and glucoronic acid excreted by kidney

46
Q

Ketamine Metabolism

A

Hepatic, CYP 450
ACTIVE METABOLITE: Norketamine (1/3 potency of parent, causes prolonged analgesia)

47
Q

Barbs Interactions

A

Enzyme induction when on prolonged gtt
increases metabolism of: anticoagulants, phenytoin, TCA’s, digoxin, corticosteroids, bile salts, vitamin K
Can persist for 30 DAYS!

48
Q

Ketamine Interactions

A

Volatile anesthetic → hypotension
NDNMB drugs → enhanced- cholinesterase

Succinylcholine → prolonged

49
Q

Excretion Induction drugs

A

All kidney

Etomidate: ‣ 85% in urine
‣ 10-13% in bile (GI)

50
Q

Clearance Propofol

A

30-60 mL/kg/min
Plasma (lungs) > Hepatic flow
Tissue uptake > CYP 450

51
Q

Clearance Etomidate

A

Clearance 5x faster than thiopenthal
***wake up fast

52
Q

Clearance Ketamine

A

High hepatic clearance : 1 L/min

53
Q

CNS Barbs

A

‣Cerebral vasoconstrictor (helps with seizures)
‣decreases CBF and decreases CMRO2 by 55%
NO ANALGESIA

54
Q

CNS Methohexital

A

‣Lower seizure threshold, induce seizures in temporal lobe resection
‣ Can decrease seizure duration (once pt already has seizure) 35-45% in ECT pts compared to etomidate

55
Q

CNS Propofol

A

↓CMRO2, CBF and ICP
‣Auto-regulatory r/t CBF and PaCO2 maintained
‣ EEG changes similar to thiopental
‣ No SSEP suppression unless nitrous or volatiles added
‣ Causes excitatory movements on induction, does produce myoclonus movements.

56
Q

CNS Etomidate

A

‣ ↑ incidence of myoclonus (50-80%) Greater than all others
‣ alteration in balance of
inhibitory and excitatory
influences of thalamocortical
tract
‣ give benzo or opiod to inhibit
myclonus (FENT 1-2 mcg/kg
IV)
‣ USE CAUTION WITH SEIZURE
PT!!!
‣ ↓ CBF, CMRO2 35-45%
‣ Direct CEREBRAL VASOCONSTRICTOR
‣↓ ICP
‣Similar EEG changes to Thiopental, but has frequent excitatory spikes.

57
Q

CNS Ketamine

A

‣ ↑ ICP
‣ Potent vasodilator, ↑ CBF by 60%
‣ Ceiling effect at 0.5-2 mg/kg IV for ↑ ICP
‣ excitatory activity on EEG
‣ DOES NOT ALTER SEIZURE THRESHOLD
‣ Myoclonus
‣ ↑plitude on SSEP, nitrous reduces this

58
Q

Induction CNS summary

A

Analgesia most to least: Ketamine, propofol, then barbs and etomidate has none

Caution in seizure patients with etomidate and methohexital

MYOCLONUS INCIDENCE:
50% to 80% Etomidate > 17% after Thiopental, 13% after Methohexital, 6% after propofol

59
Q

CV Barbs

A

‣ Lack of baroreceptor response esp. in hypovolemia, CHF, Beta blockade
‣ Histamine release causes BP drop

60
Q

CV Sodium Pentothal
(thiopental/ pentothal)

A

Normovolemia, 5 mg/kg infusion of thiopental:
‣ ↓ 10 - 20 SBP
‣ ↑ 15-20 HR
‣Previous exposure to thiopetnal can induce anaphylactoid response

61
Q

CV Propofol

A

‣ ↓ BP (more than thiopental) d/t inhbition of SNS smooth muscle relaxation, ↓ intracellular Ca+
‣ ↓BP exaggerated in hypovolemia, elderly, LV compromise
‣ Laryngoscopy stimulus can ↑ BP
‣↓ HR d/t ↓ SNS , ↓ baroreceptor reflex
‣ Profound brady and asystole even in healthy patients!!!

62
Q

CV Etomidate

A

CARDIOPROTECTIVE AGENT
‣ Good for patients with low EF
‣Minimal changes in HR, SV, CO, Contractility
‣ SUDDEN HYPOTENSION w/ HYPOVOLEMIA w/ high 0.45 mg/kg IV induction dose
‣ ❌ histamine or intra-arterial damage

63
Q

CV Ketamine

A

‣THINK SNS EFFECTS!
‣ ↑SBP, PAP, CO, MRO2
‣↑ plasma NE and Epi levels
‣ inhibit these effects by admin of
BENZO, volatiles, N20
‣ Can cause sudden ↓BP d/t depletion of catecholamine stores. Direct myocardial suppressant
‣ ephedrine won’t work bcuz indirect action

64
Q

CV Induction Summary

A

Etomidate good for heart cases

Propofol and barbs both cause loss of baroreceptor reflex

propofol has most dramatic low BP effect

Etomidate can cause adrenal suppression s/t inability to convert cholesterol into cortisol will reduce ability to use BP meds unless you give stess dose.

Then Ketamine will cause increased circulation of epi and norepi, but eventually will run out of catecholamine stores

65
Q

Resp Barbs

A

‣ Dose dependent depression of ventilatory centers (medullary and pontine)
‣ Less sensitive to CO2 (may need CO2 increased to initiate spontaneous respiration)
‣ Return to spontaneous ventilation → slow frequency, decreased Vt.

66
Q

Resp Propofol

A

‣ Dose Dependent apnea
‣Synergistic with opioids!! = ↑ resp depression
‣ Maintain hypoxic pulm vasoconstriction response.. V/Q mismatch
‣ Painful surgicial stimulation inhibits ventilatory depression
‣Bronchodilator effects = GOOD

67
Q

Resp Etomidate

A

‣ Ventilation depression < barbs
‣ Rapid IV injection = apnea
‣ Vt decreases are offset by compensatory ↑ in Resp rate (transient 3-5 min)
‣ Stimulates CO2 medullary centers

68
Q

Resp Ketamine

A

‣ ↑ pulm artery pressure up to 44 mmHG
‣ no depression of ventilation
‣PaCO2 ventilation response maintained
‣ upper airway reflexes and tone maintained = ↑ of laryngospasms
‣ ↑ salivation and tracheobrochial mucous secretions
‣ ↑ bronchodilation (no histamine release)

69
Q

Barbs Additional Info

A

KIDNEYS: causes transient ↓ RBF and GFR
INTRA ARTERIAL INJECTION:
‣immediate intense vasoconstriction,
‣causes pain along length of artery,
‣obscure distal pulses,
‣ blanching of extremity then cyanosis
‣ gangrene and permanent nerve damage
TREATMENT: Vasodilators ( lidoaine/ papaverine), adequate perfusion

‣When Somatosensory Evoked Potential (SSEP) monitoring is required, BARBS desired b/c do not effect the neuron transmission when doing SSEP’s

70
Q

‣Other Oxybarbituates:

A

Phenobarbital
‣ Pentobarbital

‣ produces excitatory phenomena: Hiccups and myoclonus

71
Q

‣Other Thiobarbituates:

A

‣Thiomylal- more potent, replaced an oxygen with a sulfur atom

‣Fat Blood partition coefficient is 11

72
Q

Propofol Hepatic/renal side effects

A

‣Liver transaminase and creatinine concentrations remain normal
‣ Prolonged Gtt’s can cause:
‣Hepatocellular injury
‣ PROPOFOL INFUSION SYNDROME
‣ green urine d/t phenols, NO alteration in renal fx.and
‣ Cloudy urine d/t uric acid crystallization

73
Q

Propofol syndrome

A

PROPOFOL SYNDROME:
‣ Gtt’s > 75 mcg/mg/min for > 24 hrs
‣ S/sx: Lactic acidoses, Brady-dysrhthmias, Rhabdo.
‣ SEVERE refractory brady in PEDS
‣ DX: ABG and serum lactate
‣ Reversible in early stages
‣ Cardiogenic shock → ECMO

74
Q

Propofol other info

A

OTHER: INHIBITS PLATELET AGGREGATION, and ↑IOP

Other Preparations on market (not common)
Ampofol
*Low-lipid emulsion with no preservative.
*Higher incidence of pain on injection.
Aquavan
*Prodrug that obviates pain on injection.
*By-product → unpleasant dysesthia
*Slower onset, larger Vd, and higher potency.
Nonlipid with Cyclodextrins
*In clinical trials

Plasma Levels: unconscious to induction: 2-6 mcg/ml; Awakening 1-1.5 mcg/ml

PONV MOA: Depresses subcortical pathways and has a direct depressant effect on emetic center

Other benefits:
Antipuritic (esp for people that have had neuraxial opioids or cholestasis), anticonvulsant, analgesia at low doses, potent antioxidant (helps liver), BRONCHODILATOR

75
Q

Etomidate Other Info

A

no hangover effect or cummulative effects d/t fast clearance

‣ No analgesia, so you will need multimodal anesthesia (need opioid use with laryngoscopy/ traceal intubation)

‣ Adrenocorotical Suppression: Dose depenedent, inhibits the conversion of cholesterol to cortisol,
‣↓ STRESS RESPONSE
‣↓ BP
‣↑Mechanical ventilation
time
‣ USE CAUTION w/ Sepsis
and hemorrhage

76
Q
A

A&P Texas Wes (8 decks)

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