Anesthesia Pharmacology Flashcards
1
Q
The anesthesia provider should do the following 5 things prior to induction?
A
- Perform and document a thorough pre anesthesia assessment and evaluation
- Obtain and document informed consent for the planned anesthetic from the patient or legal guardian
- Formulate a patient specific plan for anesthesia care
- Implement and adjust the plan based on the patient’s physiologic response… intervene to maintain optimal physiologic condition
- Monitor, oxygenate, ventilate, CV, temp NMBs, positioning
2
Q
Pharmacodynamics
A
- The action of the drug on the body
- “Relationship between the concentration of the drug and the magnitude of effect”
- Nature of the drug (racemic, oral, IV)
- receptors and binding sites
- therapeutic index
3
Q
Pharmacokinetics
A
- The effects of the body on the drug
- “Relationship between the drug dose and the time course of drug levels in the bloodstream”- for anesthesia- At the receptor site of desired action*
- binding, permeability, elimination, distribution
4
Q
Agonists
A
Cause desired action at the receptor
5
Q
Antagonists
A
Have affinity for receptor but NO efficacy
-No action at the receptor
6
Q
Competitive Antagonism
A
- shifts agonist-concentration effect curve to the right
- tend to bind at the same site as agonists
7
Q
Non-competitive antagonists
A
- May bind irreversibly to the receptor
- Lowers the number of active receptors available
- less effect seen
- tend to bind to another (allosteric) site which changes the desired receptor site
8
Q
ED/C50 and ED/C95
A
The dose (concentration) of drug needed to obtain 50% or 95% of the maximal effect
9
Q
During anesthesia induction, why do we give 2-3 times the ED95 of drugs?
A
-to achieve rapid onset, knowing it will take a longer time for the effect-site concentration to drop low enough for the effect of that drug to wear off
10
Q
Potency
A
- function of affinity for the receptor and function at the receptor
- high affinity with low potency= low potency
- low affinity with higher potency= HIGH potency
11
Q
Therapeutic Index
A
Toxic Dose (TD50)/ Effective dose (ED50)
- high TI indicates relatively safe drug
- anesthesia drugs have low TI- less safe
12
Q
Dissociation constant
A
- describes the propensity for a drug-receptor complex to break apart
- relatively more important for anesthesia drugs
13
Q
Clearance
A
Rate of elimination/ plasma drug concentration
-clearance by an organ is equal to the extraction capability of the organ X the blood flow to the organ
14
Q
First order Clearance
A
- clearance of drugs with first order kinetics is constant regardless of plasma concentration
- constant T1/2, 50% decrement per time interval
15
Q
Zero order Clearance
A
- clearance of drugs with zero order kinetics is not constant and depends upon plasma concentration
- constant elimination, units eliminated/time (EtOh)
16
Q
T 1/2 life
A
- varies directly with the Vd and inversely with clearance
- higher Vd= takes longer to clear
- higher clearance= shorter 1/2 life
17
Q
Phase 1 metabolism
A
converts parent drug to more polar substance (hydrophobic to hydrophilic)
18
Q
Phase 2 metabolism
A
conjugate drug with polar moiety making it more water soluble and excretable
19
Q
CYPS: p450, p2D, P3A
A
response for most drug metabolism
20
Q
Enzyme induction
A
- stimulation of drug metabolizing enzymes in the liver, usually phase 1 enzymes
21
Q
Phase I Reactions- p450 dependent reactions
A
- P450 dependent reactions (primarily oxidative reactions):
- Hydroxylation- amphetamines, barbs, dilantin, warfarin
-N-deakylation- caffeine, morphine, tehophylline
-O-deakylation- codeine
-N-oxidation- acetaminophen, nicotine
S-oxidation- cimetidine, chlorpromazine
-Deamination, diazepam
22
Q
Phase I Reactions- p450 Independent reactions
A
- Amine oxidation- epinephrine
- Dehydrogenation- chloral hydrate, ethanol
23
Q
Phase I reactions- hydrolyses
A
- esters, aspirin, procaine, succinylcholine
- amides, indomethacin, lidocaine, procainamide
24
Q
Phase I reactions- reduction
A
-clonazepam, dantrolene, nalaxone
25
Phase II reactions- Glucuronidation
-acetaminophen, diazepam, digoxin, morphine
26
Phase II reactions- Acetylation
-Clonazepam
27
Phase II reactions- sulfation
-acetaminophen, methyldopa
28
Phase II reactions- methylation
-dopamine, epinephrine, histamine, norepi
29
CYP inducers
- speed up metabolism
| - phenobarbital, dilantin, rifampin, carbamazepine, ethanol, barbiturates, st. johns wort
30
CYP inhibitors
- slow down metabolism
| - cimetidine, grapefruit juice, amiodarone, mtronidazole, omeprazole, SSRI's, diltiazem, erthyromycin
31
Low molecular weight drugs MW <100
- can get more places and have less specific actions and more side effects
examples: sux, morphine, fentanyl, acetaminophen, NaCl, dextrose
32
High molecular weight drugs MW >100
- are often poorly absorbed and distributed
| examples: rocuronium, cistatcurium, cefazolin, dextran
33
Plasma binding (Albumin, AAAG1)
-effectively eliminates drugs from the concentration gradient which determine drug movement and action
34
Water solubility
-is a function of electrostatic charge of the molecules
35
Lipid Solubility is inversely proportional to:
-to the charge
36
What aspect is most important in the cessation of our anesthesia drugs?
- redistribution from active sites and removal of administration are most important
- NOT metabolism
37
Volume of Distribution
- Units of drug in body/units of drug in plasma
- low Vd means most of the drug is in the plasma and very little has moved elsewhere
- high Vd means drug moves throughout the body and less remains in plasma
- be aware of protein binding effect on Vd
- cardiac output, differential circulation, recirculation and pulmonary intake all effect this
38
Context sensitive half-times
- time required for plasma concentration of a drug to decrease by 50% after d/c administration
- longer infusions=more drug into tissues
- drug accumulates at different rates based on physiochemical properties of the drug
- drug removed by: redistribution from site of action, metabolism into inactive form, excretion
- beware of active metabolites
39
Remifentanyl has _______ CSHT
very short, stable context sensitive half time, predictable and rapid emergence
40
Propofol and fentanyl have _____CSHT
longer CSHT, less predictable and longer emergence
41
Active metabolites
-codeine and tramadol designed as prodrugs with active metabolites which cause desired action
42
4 major options for anesthesia
1. Monitored Anesthetic Care (MAC) with or without local anesthesia
2. Peripheral nerve block (inter scalene, femoral) with or without a MAC
3. Regional (conductive) anesthesia (spinal or epidural)
4. General anesthesia (with or without intubation, LMA, I gel, mask)
43
What are the 4 major components associated with providing general anesthesia?
1. Anxiolysis
2. Analgesia
3. Hypnosis
4. Paralysis
44
MAC
- support VS, monitor respiratory depth and pattern
- provide other meds as needed
- physical and physiological support
45
Is MAC= conscious sedation?
No, an unconscious patient is not in a MAC state
46
Peripheral Nerve Blocks
1. Good for extremity anesthesia
2. Allow for conscious patient
3. Beneficial if unable to perform more invasive anesthesia
4. Unpredictable sensory and more effects
5. Verify with surgeons*
47
Regional Anesthesia- Spinal/Subarachnoid block (SAB)
- rapid placement
- rapid onset high quality sensory and motor blockade
- less pain during surgery, some residual after
- less PONV
48
Regional Anesthesia- Epidural/Caudal
- lower risk for PDPH?
- less systemic hypotension than SAB
- extended blockade via indwelling catheter
- post operative analgesia
49
Potential increased risks with SAB, epidural/caudal
- hypovolemia
- increased ICP
- coagulopathy
- sepsis
- infection at puncture site
- pre-existing NM disease
50
General Anesthesia- 4 stages
1. Induction
2. Airway management
3. Maintenance
4. Emergence
