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Pharmacology > Etomidate/Propofol/Ketamine > Flashcards

Etomidate/Propofol/Ketamine Flashcards

1
Q

In a perfect world

A

drugs are stable in aqueous solution; water soluble
minimal CV or respiratory depression
Lack of hypersensitivity reactions
rapid and smooth onset of action
rapidly metabolized
produce a steep dose-response relationship
quick return to baseline mental status

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2
Q

Propofol

A 
insoluble; requires a lipid  vehicle for emulsification
10% soybean oil
2.25% glycerol
1.2% lecithin 
supports bacterial growht
not chiral
pain on injection
no antagonist
a rapid return to consciousness with minimal residual side effects is one of the most important advantages
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3
Q

pH of Diprivan

A

7-8.5

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4
Q

pKa of Diprivan

A

11

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5
Q

Diprivan contains

A

0.05% EDTA- ethylenediaminetetraacetic acid

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6
Q

pH of propofol

A

4.5-6.4

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7
Q

pKa of propofol

A

11

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8
Q

Propofol contains

A

0.025% sodium metabisulfite or benzyl alcohol

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9
Q

MOA of Propofol

A

Selective modulator of GABAa Receptor
GABA is major inhibitory transmitter in CNS
spinal motor neuron excitability not altered

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10
Q

Pharmacokinetics of Propofol

A

Clearance exceeds hepatic BF
context sensitive half-time infusions less than 40 mins
Not influenced by hepatic or renal dysfunction
decreased rate of plasma clearance in patients older then 60

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11
Q

Active metabolite of Propofol

A

4-hydroxypropofol

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12
Q

What do propofol reversibly bind to

A

erythrocytes and plasma proteins (50%)
plasma albumin (48%)
Free (2%)

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13
Q

Increase in free fraction of Propofol seen in

A

severe hepatic and renal disease

pregnancy

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14
Q

PD of Propofol (CNS)

A

rapid and pleasant loss and return to conciousness
may induce myoclonus secondary to disinhibition of subcortical centers (less then etomidate)
neuro protectant

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15
Q

PD of Propofol (CV)

A

may cause mild to moderate decrease in BP secondary to

  • decrease in sympathetic tone and vasodilation (primarily)
  • CNS cardiac and baroreceptor depression
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16
Q

PD of Propofol (Resp)

A

respiratory depression common in induction doses
DD with induction secondary to decreased sensitivity of respiratory center to O2
minimal bronchodilation

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17
Q

Propofol Induction Dose

A

Adult dose: 1.5-2.5 mg/kg
decrease dose in elderly
increase dose in pediatrics
effects exaggerated with CV disease

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18
Q

Continuous Infusion of Propofol

A

IV sedation
prompt recovery without residual sedation- great for endoscope
25-100ug/kg/min
minimial/ no analgesic properties
can be used in conjuction with anxiolytic and opioid

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19
Q

Maintenance of Anesthesia (Propofol)

A

associated with minimal PONV
100-300ug/kg/min
used in conjuction with a short acting opioid

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20
Q

Other applications of Propofol

A 
antiemetic 
10-15mg IV; followed by 10 ug/kg/min infusion
Antipruritic
10 mg IV related to intrathecal opioids, cholestasis
Anticonvulsant
1mg/kg
Attenuate bronchoconstricction*
effects intracellular Ca++ homeostasis
Analgesic (neuropathic pain)
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21
Q

Contraindications of Propofol

A

Hypersensitivity (maybe lechithin allergy)
lipid metabolism disorder
sulfate allergy (more common in asthmatics)
use caution in elderly, debilitated and cardiac-compromised patients

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22
Q

PRIS

A

propofol infusion Syndrome
not seen in long term, high dose infusions of propofol
not seen in anesthesia
associated with significant morbidity and mortality
exact mechanism of action unknown
more common in adults, but children as well

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23
Q

Risk Factors of PRIS

A 
> 4mg/kg/hr
> 48 hours
critical illness
high fat low carb intake
concmitant catecholamine infusion
steroid administeration and inborn errors of mitchondrail fatty acid oxidation
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24
Q

Signs of PRIS

A 
high anion gap metabolic acidosis
cardiac failure
persistent bradycarida refractory to treatment
fever
severe hepatic and renal disturbances
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25
Clinical Features of PRIS (CV)
hypotension, bradycardia, widening QRS, VTACH or FIB, asystole, ischemic EKG, arrhythmia, heart failure
26
Clinical Features of PRIS (Resp)
hypoxia, pulmonary edema
27
Clinical Features of PRIS (Renal)
acute kidney injury, hyperkalemia
28
Clinical Features of PRIS (musculoskeletal)
rhabdomyolysis
29
Clinical Features of PRIS (metabolic)
hyperthermia, high anion gap metabolic acidosis, urine discoloration
30
Clinical Features of PRIS (hepatic)
hepatomegaly, abnormal LFTs, steatosis, lipidemia, hypertryceridemia
31
Propofol Abuse
addictive properties well-being on emergence, develop a tolerance incidence markedly increased over past ten years 18% of academic centers reported incidence of abuse or diversion significant mortality rate among anesthesia providers not a controlled substance (facility dependent)
32
Etomidate
Carboxylated Imidazole | Viewed as an alternative to propofol for IV induction, esp in the presence of an unstable cardiac patient
33
Ph and Pka of Etomidate
water soluble in an acidic pH and lipid soluble in physiologic ph 8.1 pka 4.2
34
MOA of Etomidate
administered as a single Isomer R+ isomer 5x more potent selective modulator of GABAa receptors
35
Pharmacokinetics of Etomidate
Large Vd suggest significant tissue uptake moderate lipid solubility as a weak base 75% bound to plasma albumin prompt emergence secondary to redistribution to tissues and rapid metabolism metabolized by hydrolysis (plasma esterases and mircrosomal enzymes in liver)
36
Pharmacodynamics of Etomidate
onset occurs rapidly; within one arm to brain circulation return to consciousness 5-15 mins CBF and CMRO2 both decreased (decreased toin ICP while maintain CPP) involuntary myoclonic movements common (can involve a single muscle or groups, so severe can be mistaken for seizures... secondary to distribution to deep cerebral and brainstem decreases amplitude and increases latency maintain hemodynamic stability (advantage over propofol) - acts on alpha2 B adrenergic receptors which mediates increases in BP minute volume decreases but RR increases
37
Clinical Uses of Etomidate
differs from most IV anesthetics in that cardiac depressive effects are minimial in doses required to produce anesthesoa NOT AN INFUSION induction doses up to 0.3mg/kg result in minimal changes in: HR, SV, CO doses >0.45mg/kg results in decreased B/P and CO, apnea may occur with rapid injection
38
Induction Dose of Etomidate
Adult Induction Dose- 0.2-0.4mg/kg involuntary myoclonic movements common no analgesic properties
39
Side Effects and complications of Etomidate
spontaneous myoclonus due to disinhibitation of subcortical structures; administration of fentanyl or benzo can decrease incidence causes adrenocortial suppression Increased incidence of postoperative nausea and vomitting incidence of allergic reaction is very low minimal pain on injection may activate seizure foci in specific populations; however has been shown to terminate status epilecpticus
40
What enzyme is inhibited with etomidate administration
11B-hydroxylase- inhibits conversion of cholesterol to cortisol
41
Etomidate is Contraindicated in what patient population
porphyrias
42
Ketamine
Phencyclidine produces "dissociative anesthesia" potent amnestic and analgesic does not produce significant respiratory depression does not require a lipid vehicle for dissolution
43
ph and Pka of ketamine
ph 3.5 to 5.5 | pka 7.5
44
Pharmacokinetics of Ketamine
not significantly bound to plasma proteins (12% ) rapid distribution to tissues highly lipid soluble, rapid transfer to BBB demethlyation of ____ by CYP 450 microenzymes elimination half-life 2-3 hours
45
MOA of Ketamine
binds non-competitely to the phenylcyclidine site of N-methyl-D apartate (NMDA) receptors (antagonist-glutatmate) resulting in depressive effect on the medial thalmic nuclei Weak actions on GABAa receptors
46
Pharmacodynamics of Ketamine
produces a "dissociative state" patient is cataleptic increased CBF CMRO2 and ICP increased produces nystagmus increase IOP increases HR BP and SVR (SNS nervous activation) maintain spontaneous respirations bronchodilator, not effective as sole agent
47
Ketamine as an Induction Agent
Best for : hypovolemic patients (trauma), Adult induction Doses (induction 2-3 minutes IV) 1-2.5mg/kg IV 4-8 mg/kg IM (<10 minutes) 10 mg/kg orally (<10 minutes) does not produce pain or irritation in injection bronchodilation useful for patients in asthma induction of anesthesia in patients with CAD is complicated
48
Clinical Uses of Ketamine
trauma patients benefit from favorable cardiovascular effects provides analgesic effects at sub anesthetic doses 0.2-0.5mg/kg (somatic > visceral) OB anesthesia without neonatal depression chronic pain syndromes used for burn patients
49
Ketamine Dart
good for pediatric patients with asthma
50
Ketamine Side Effects and Complications
produces effects similar to sympathetic nervous system stimulation potent cerebral dilator; patients with intracranial pathology are considered vulnerable to sustained increase ICP tolerance may develop pulmonary arterial blood pressure, heart rate , CO and cardiac work and myocardial oxygen requirements all increased apnea after administeration of succinylcholine prolonged enhancement of nondeplorizing neuromuscular blocking agents in patients are risk for MI during periop period, medications that block preconditioning should be avoided increased oral secretions
51
Ketamine and Emergence Delirium
incidence 5-30%; Partially dose dependent emergence associated with visual, auditory, proprioceptive and confusional illusions frequently have morbid content and vivid color factors: age > 15 female history of personality problems or frequent dreams occurs less frequently with repeated doses adminstering with benzos five minutes prior to surgery can decrease incidence (midazolam > diazepam) atropine can increase incidence
52
Dextromethorpan
low affinity NMDA antagonist commonly found in cough medicines as an antitussve psychoactive effects increase abuse potential
53
Dextromethorpan (chemical structure)
D-isomer of the opioid agonist levomethorphan
54
Excessive intake of Dextromethorpan
hypertension, tachycardia, somnolence, agitation, slurred speech, ataxia, diaphoresis, skeletal muscle rigidity, seizures, coma
55
Dexmedetomidine
alpha2 adrenergic agonist alpha2 antagonist (shorter then acting than clonidine) more selective for alpha2 then alpha1 differs from GABA drugs in that it produces sedation by decreasing sympathetic nervous system activity (inhibits NE release)
56
Where are highest density of dexmedetomidine receptor?
pontine locus cerulus
57
Atipamezole
is the specific and selective reversal agent of dexmedetomidine
58
Dexmedetomidine Pharmacokinetics
highly protein bound undergoes extensive hepatic metabolism half life 2-3 hours
59
Dexmedetomidine Clinical Uses
pre-treatment: attenuates hemodynamic response to tracheal intubation, decreases MAC and opioid requirements, increases hypotension TIVA- 0.5-1ug/kg bolus over 15 minutes 0.2-0.7 ug/kg/hr infusion severe bradycardia/asystole may follow administration intranasal preop anxiolysis in peds patietnts
60
Scopolamine
anticholinergic only anticholinergic drug for sedation decreases activity of the reticular activating system preop sedation (0.3-0.5mg IV/IM) enhances effects of concomitantly administered (opioids and benzos) strong antisialagogue effect less lilkely to produce cardiac effects commonly administered transdermal for N/V
61
Side effects of Scopolamine
mydriasis cycloplegia central anticholinergic symptom overdose- characteristics of muscarinic cholinergic blockade
62
Scopoloimine reversal
physostigmine (anticholinesterase) 15-60ug/kg IV repeat as required

Pharmacology (14 decks)

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