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Pharm Induction Drugs Flashcards

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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
Dose Ketamine
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
26
Barbiturates Onset
Rapid: 30secs
27
Propofol Onset
*** rapid injection= LOC in 30 sec
28
Etomidate Onset
within 1 min IV
29
Ketamine Onset
Onset: 1 min IV, 5 min IM Duration : 10-20 min
30
Redistribution Barbs
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
31
Barbs context sensitive half-life
Prolonged infusion = lengthy , any drug with large redistribution
32
Propofol Context sensitive half-life
40 minutes (on 8hr infusions) **Shorter than all barbs, not as lipid soluble**
33
Barbs Half-time
E 1/2 time of Thiopental > Methohexital Peds: Short half-time d/t ↑ metabolism
34
propofol half-time
0.5-1.5 hrs
35
Etomidate half-time
2-5 hrs
36
Ketamine half-time
2-3 hrs Return of consciousness (ROC): 10 to 20 minutes
37
Protein Binding Induction Drugs
Barbs: 70-85% Etomidate: 76% Ketamine: none
38
Induction Drugs Vd
Propofol: 3.5-4.5L/kg Etomidate: Large Ketamine: 3L/kg
39
Barbs Ionization
Methohexital: normal pH 76% non-ionized Sodium Pentothal (thiopental/ pentothal): normal pH, 61% non-ionized
40
Barbs Lipid solubility
Methohexital
41
Etomidate Lipid Solubility
Water soluble at acidic pH, lipid soluble at physiologic pH
42
Ketamine Lipid Solubility
(5x to 10x than Thiopental) Brain -> not plasma bound -> distributed to tissues Largest
43
Barbs Metabolism
99% hepatocytes Methohexital: Faster metabolism than thiopental and more rapid recovery from induction
44
Etomidate Metabolism
Hydrolysis hepatic microsomal enzymes ‣ Plamsa esterases
45
Propofol Metabolism
Hepatic: CYP 450 Metabolites: Water soluble sulfate and glucoronic acid excreted by kidney
46
Ketamine Metabolism
Hepatic, CYP 450 ACTIVE METABOLITE: Norketamine (1/3 potency of parent, causes prolonged analgesia)
47
Barbs Interactions
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
Ketamine Interactions
Volatile anesthetic → hypotension NDNMB drugs → enhanced- cholinesterase Succinylcholine → prolonged
49
Excretion Induction drugs
All kidney Etomidate: ‣ 85% in urine ‣ 10-13% in bile (GI)
50
Clearance Propofol
30-60 mL/kg/min Plasma (lungs) > Hepatic flow Tissue uptake > CYP 450
51
Clearance Etomidate
Clearance 5x faster than thiopenthal ***wake up fast
52
Clearance Ketamine
High hepatic clearance : 1 L/min
53
CNS Barbs
‣Cerebral vasoconstrictor (helps with seizures) ‣decreases CBF and decreases CMRO2 by 55% ****NO ANALGESIA****
54
CNS Methohexital
‣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
CNS Propofol
↓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
CNS Etomidate
‣ ↑ 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
CNS Ketamine
‣ ↑ 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
Induction CNS summary
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
CV Barbs
‣ Lack of baroreceptor response esp. in hypovolemia, CHF, Beta blockade ‣ Histamine release causes BP drop
60
CV Sodium Pentothal (thiopental/ pentothal)
Normovolemia, 5 mg/kg infusion of thiopental: ‣ ↓ 10 - 20 SBP ‣ ↑ 15-20 HR ‣Previous exposure to thiopetnal can induce anaphylactoid response
61
CV Propofol
‣ ↓ 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
CV Etomidate
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
CV Ketamine
‣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
CV Induction Summary
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
Resp Barbs
‣ 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
Resp Propofol
‣ 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
Resp Etomidate
‣ 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
Resp Ketamine
‣ ↑ 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
Barbs Additional Info
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
‣Other Oxybarbituates:
Phenobarbital ‣ Pentobarbital ‣ produces excitatory phenomena: Hiccups and myoclonus
71
‣Other Thiobarbituates:
‣Thiomylal- more potent, replaced an oxygen with a sulfur atom ‣Fat Blood partition coefficient is 11
72
Propofol Hepatic/renal side effects
‣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
Propofol syndrome
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
Propofol other info
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
Etomidate Other Info
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

A&P Texas Wes (8 decks)

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