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Pharmacology Sem 1 > IV Anesthetics > Flashcards

IV Anesthetics Flashcards

1
Q

What ideal drug property does propofol violate?
A. Pain on Injection
B. Context sensitive half-time is 40 minutes
C. Can cause bradycardia & hypotension
D. Two of the above
E. None of the above

A

D. It is water insoluble so causes pain on injection & can cause bradycardia & hypotension
These violate the 7 ideal drug principles: water soluble, no hypersensitivity reactions, fast on, fast off, quick return to mental baseline, limited CV and respiratory issues, steep dose-response relationship

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2
Q

What is the mechanism of action of propofol?

A

Binds allosterically to GABA, allows Cl- to come in and hyperpolarize the cell (inhibitory)

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3
Q

What are the ideal properties of a drug?

A
  1. Water soluble
  2. Limited CV & Respiratory Effects
  3. No hypersensitivity reactions
  4. Quick on (quick onset of action)
  5. Quick off (metabolized quickly)
  6. Steep dose-response relationship
  7. Quick return to baseline mental status
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4
Q

Chemical Structure of Propofol

A

“Snowman” Phenol with two arms

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5
Q

What is the pH and pKa of Propofol?

A

Diprivan: pH:7-8.5 pKa: 11
Propfol: pH: 4.5-6.4 pKa: 11
pH differs due to additives/manufacturing

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6
Q

What is a principle advantage of propofol?
A. it has antiemetic properties
B. antagonist is flumazenil
C. Rapid return to consciousness
D. Not influenced by renal or liver dysfunction

A

C. Rapid return to consciousness

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7
Q 
Which enantiomer of propofol produces bronchodilation?
A. S-enantiomer
B. R-enantiomer 
C. It comes in a racemic mixture
D. Propofol is non-chiral
A

D. Propofol is non-chiral

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8
Q

What is the stability of propofol?

A

Allows for bacterial growth so open vial must be thrown out after 6 hours

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9
Q

What is the best way to prevent pain on injection of any drug?

A

Large bore IV in large

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10
Q

What is the antagonist or reversal agent of propofol?

A

There is none! We are married to its effects

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11
Q

What is the clearance of propofol?

A

0.87, clearance exceeds hepatic blood flow

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12
Q

Propofol Clearance

A

Clearance exceeds hepatic blood flow
-Tissue uptake in the lungs- reduces initial conc. next round of blood comes in and diffuses from lungs back into blood
-extensive hepatic metabolism CYP450
Propofol is not influenced by hepatic or renal dysfunction
Decreased rate of plasma clearance in patients older than 60

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13
Q

Metabolite of propofol

active or inactive?

A

Active: 4-hydroxypropofol

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14
Q

Context sensitive half-time of propofol

A

<40 minutes

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15
Q

Hypersensitivity with propofol

A 
egg lecithin 
sulfite allergies (asthmatics)
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16
Q

What drugs would you not give to patients with porpyphria?

A

Barbiturates, diazepam, & etomidate

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17
Q

Protein binding with propofol

A

98% bound, 2% free (increased in pregnancy, severe hepatic and renal disease)

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18
Q

What drugs produce myoclonus?

A

methohexital, etomidate, propofol (rare)

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19
Q

Neuro effects of propofol

A

Good for neuroprotection (outside of high ICP)

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20
Q

CV effects of propofol

A

hypotension due to decrease in sympathetic tone and vasodilation (primarily)
CNS, cardiac, and baroreceptor depression

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21
Q

Your preceptors asks you why propofol causes hypotension. What do you tell them?

A

Propofol decreases sympathetic tone and vasodilation

Also has CNS, Cardiac & baroreceptor depression

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22
Q

What respiratory effects does propofol have?

A

Respiratory depression common in induction doses
-Dose dependent w/ infusions secondary to decreased sensitivity of respiratory center to CO2
Minimal bronchodilation

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23
Q

Induction dosage of propofol

A

Adult dose 1.5 to 2.5 mg/kg (decrease in elderly, increase in kids, effects exaggerated with CV disease)

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24
Q

When do you decide to give ideal vs. actual body weight dosage?

A

Liphophilic drug would give true body weight whereas drugs that stay in blood stream we’ll error on side of ideal body weight

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25
What drug would you give to cause respiratory depression for induction?
Propofol causes more than etomidate and ketamine
26
Propofol dose of IV sedation:
25-100 mcg/kg/min minimal/no analgesic properties (give something for pain!) can be used in conjunction with anxiolytic and opioid prompt recovery without residual sedation-great for endoscopy
27
Propofol dose for maintenance of anesthesia: | TIVA (total IV anesthetic) dosage
100-300 mcg/kg/min associated w/ minimal postop n/v used in conjunction w/ short-acting opioid
28
Other applications of propofol & dosages
Antiemetic: 10-15 mg IV; followed by 10 mcg/kg/min infusion Antipruritic: 10 mg IV related to intrathecal opioids, cholestasis Anticonvulsant: 1 mg/kg IV Attenuate bronchoconstriction: effects intracellular Ca++ homeostasis Analgesic (neuropathic pain)
29
Contraindications of propofol
Hypersensitivity (lethicin- found in eggs, peanuts, soybeans) Lipid metabolism disorder Sulfate allergy Use caution in elderly, debilitated and cardiac-compromised patients
30
What does PRIS stand for & what is it?
Propofol infusion syndrome seen in long-term, high dose infusions of propofol associated with significant morbidity and mortality
31
Which of the following patients has a higher likelihood of developing PRIS? A. 85 year old patient undergoing right hip fixation with active liver disease B. Patient intubated in the ICU for shock receiving steroids C. Older patient coming from ICU for intraop procedure who has been receiving propofol for 7 days D. Child who is coming in for tonsillectomy
C.
32
Risk factors of PRIS:
>4mg/kg/hr, >48 hr dose, critical illness, high fat-low carb intake, concomitant catecholamine infusion, steroid administration and inborn errors of mitochondrial fatty acid oxidation
33
Signs of PRIS:
``` high anionic gap metabolic acidosis cardiac failure persistent bradycardia refractory to treatment fever severe hepatic and renal disturbances ```
34
Which of the patient's is not experiencing a symptom of PRIS? A. Patient is bradycardic to 45 and not responsive to atropine administration B. Patient is in septic shock with fever of 104 C. Patient with a pH 7.0, pCO2: 35, bicarb: 14 D. Patient with high ALT/AST E. Patient with drop in urine output to 10cc/shift F. All patients are experiencing symptoms of PRIS
F.
35
What is happening in PRIS?
-Propofol is triggering agent (catechol & steroids already given) Fatty acid and mitochondrial activity impaired- creates oxygen supply-demand mismatch causing tissue necrosis Propofol inhibits oxidative phosphorylation preventing long-chain fatty acids into the cell, inhibits mitochondrial respiratory chain and blocks beta adrenoreceptors and calcium channels
36
Extensive s/s of PRIS:
CV: hypotension, bradycardia, widening QRS, VTACH, VFIB, asystole, ischemic EKG, arrhythmia, heart failure Respiratory: hypoxia, pulmonary edema Renal: acute kidney injury, hyperkalemia Musculoskeletal: rhabdomyolysis Metabolic: hyperthermia, high anion gap met acidosis, urine discoloration Hepatic: hepatomegaly, abnormal LFTs, Steatosis, lipidemia, hypertriglyceridemia
37
Propofol Abuse
Not a controlled substance (facility dependent) addictive properties to propofol b/c you can sleep for 10 minutes and wake up feeling refreshed Can develop tolerance
38
Etomidate pH, pKa
pH: 8.1, pKa 4.2, etomidate is also chiral (administered as single isomer-R+ isomer 5x more potent)
39
Why we would use etomidate over propofol?
Doesn't burn on injection, no CV swings
40
Mechanism of action: etomidate
allosteric agonists
41
Volume of Distribution: etomidate
0.6 mL/kg
42
Etomidate drug class
sedative hypnotic, base
43
Etomidate binding
75% bound to plasma albumin (decrease in albumin increases active fraction significantly)
44
Etomidate metabolism
metabolized by hydrolysis: phase 1 Plasma esterases and microsomal enzymes in the liver
45
Onset of etomidate
rapidly; return to consciousness 5 to 15 minutes
46
Etomidate CNS
CBF & CMRO2 decreased, decrease in ICP while maintaining CPP | Involuntary myoclonic movements common
47
Why wouldn't you want to use etomidate if monitoring neurofunction?
due to CNS effects it decreases amplitude and increases latency also can cause myoclonus
48
Etomidate CV/Resp
maintains hemodynamic stability (advantage over propofol) acts on alpha 2-B adrenergic receptors which mediates increased BP Minute volume decreases but RR increases
49
Clinical Usage/Induction dose
No longer used as infusion d/t adrenal cortical depression | Induction doses up to 0.2-0.4 mg/kg
50
True or false: etomidate has analgesic properties
False; of our sedative hypnotics only ketamine has true analgesic properties (could argue that propofol blunts neuropathic pain)
51
Side effects and complications of etomidate:
- spontaneous myoclonus occurs in >50% of patients admin of benzos or fentanyl can decrease incidence -etomidate causes adrenocortical suppression -increased incidence of postoperative n/v -porphyrias
52
How does etomidate cause adrenocortical suppression
- inhibits conversion of cholesterol to cortisol (11B-hydroxylase) - lasts greater than 8 hours after induction dose - avoid in septic shock
53
Dislikes about etomidate
Adrenal cortical suppression, postop N/V, could take 15 min. to wear off
54
Ketamine (phenycylidine) pKa, PH
base: pH 3.5-5.5, pKa 7.5
55
Function of Ketamine:
provides "dissociative anesthesia" Potent amnestic and analgesic cataleptic state where eyes remain open with a slow nystagmic gaze
56
Chirality of ketamine
comes in racemic mixture
57
Pharmacokinetics of ketamine
not significantly bound to plasma proteins (12%); rapid distribution to tissues highly lipid soluble, rapid transfer to BBB
58
How is ketamine metabolized?
Demethylation of ketamine by CYP450 microenzymes-phase 1 | metabolism dependent on hepatic flow
59
Metabolite of ketamine
Norketamine
60
Elimination half-life of ketamine
2-3 hours (d/t active metabolite)
61
Mechanism of action of ketamine
binds non-competitively to the phenylcyclidine site on NMDA receptors (antagonist- glutamate) exerts effects on opioid, monoaminergic, muscarinic, VG Na+ receptors, Ca2+ channels and nAChr channels weak actions on GABA receptors
62
An elderly patient with HTN & asthma is coming in for a general anesthetic procedure involving the eye. What would be your drug of choice for intraop sedation?
Propofol (have good window d/t baseline CV status), do not use ketamine as contraindicated in intraocular procedures due to increased IOP
63
Which drug is contraindicated in a patient with a closed head injury?
Ketamine b/c it raises CBF, CMRO2, and ICP although can be attenuated w/ opioid and benzodiazpines
64
What drug may cause a more difficult airway placement?
ketamine b/c it causes increased secretions which may block view
65
``` Ketamine causes a ____ in the sympathetic nervous system to get a _____ in HR, BP, and SVR A. Increased, decrease B. Increase, Increase C. Decrease, increase D. Decrease, decrease ```
B.
66
What patient would ketamine best drug to use for? A. patient post MVA with a closed head injury B. Patient with CAD C. Patient with hypovolemic shock secondary to MVA D. patient with chronic pain
C. good induction agent for patients in hypovolemic shock as it increases sympathetic nervous system and causes increase in BP, HR
67
Induction dose of ketamine
1-2.5 mg/kg IV 4-8 mg/kg IM (<10 minutes) 10 mg/kg orally (10-20 minutes)
68
What dose would you use to provide analgesia with ketamine?
0.2-0.5 mg/kg
69
To provide more stable hemodynamic effects while avoiding unwanted emergence reactions
we could give subanesthetic doses of ketamine combined with propofol
70
Side effects of ketamine:
potent cerebral dilator: avoid in patients where increased ICP would be concerning (intraocular) tolerance can occur -pulmonary arterial BP, HR, CO, Cardiac work, and myocardial O2 requirements increased -increased oral secretions -enhances non-depolarizing NMJ blockers -Apnea after admin of succ is prolonged d/t inhibition of plasma cholinesterases
71
emergence delirium
incidence: 5-30%; partially dose dependent - associated w/ visual, auditory, proprioceptive, and confusional illusions - could have morbid content and vivid color
72
Which patient is at higher risk for emergence delirium? A. 14 year old male undergoing baclofen pump placement B. 60 year old male veteran undergoing a toe amputation C. 46 year old cancer patient with history of depression undergoing mastectomy D. Emergence delirium is rare & most likely will not be experienced
B.
73
MOA of Dextromethorphan
low-affinity NMDA antagonist
74
Dexmedetomidine mechanism of action
Alpha2 antagonist (more selective for A2 than A1) high density of these receptors found in pontine locus ceruleus -differs from GABA drugs in that it produces sedation by decreasing sympathetic nervous system activity inhibits norepinephrine release
75
What is the reversal of dexmedetomidine
Atipamezole
76
Binding, metabolism and half-life of dexmedetomidine
highly protein bound undergoes extensive hepatic metabolism half-life 2-3 hours
77
Clinical uses of dexmedetomidine:
pretreatment: attenuates hemodynamic response to tracheal intubation, decrease MAC & opioid requirements, increases hypotension
78
Side effects of dexmedetomidine:
severe bradycardia/asystole
79
Dosage of dexmedotimidine
TIVA: 0.5-1 mcg/kg bolus over 15 minutes | 0.2-0.7 mcg/kg/hr infusion (up to 24 hours)
80
Scopolamine Class
anticholinergic (only anticholinergic used for sedation)
81
How does scopolamine cause sedation
decreases activity of the reticular activating system
82
Preop sedation dosage
0.3-0.5 mg IV/IM
83
Scopolamine pearls
strong antisialagogue effect-reduces rate of saliva transdermal for N/V Cross BBB and has least effect on HR synergistic w/ opioids/benzos
84
Scopolamine side effects
Mydriasis (Bella Donna) pupil dilation- check your pupils Cycloplegia- inability to focus for near vision Central anticholinergic symptom- can become unconscious Overdose- characteristic of muscarinic cholinergic blockade (dry mouth, difficult swallowing, blurred vision, tachy, can't sweat)
85
Scopolamine reversal
Physostigmine- anticholinesterase 15-60 mcg/kg IV Repeat as needed

Pharmacology Sem 1 (14 decks)

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