quiz 5 Flashcards
(80 cards)
1
Q
Agents with a _____ pKa value will have a _____ onset because a ______ fraction of the molecules will exist in the uncharged form and thus will more easily diffuse across nerve membranes.
A
lower
faster
greater
2
Q
range of LA pKa’s? lowest and highest drug?
A
7.6 - 9.1
- mepivicaine
- Chloroprocaine
3
Q
the lower the pKa = ?
A
faster onset
4
Q
weak base + acid becomes?
A
more ionized
5
Q
weak base + base becomes?
A
more non-ionized
6
Q
More non-ionized the ______ the drug b/c ?
A
quicker
-non-ionized gets into cell
7
Q
MOA of LA’:
A
- Block nerve conduction by impairing propagation of the action potential in axons.*
- Decrease the rate of rise of the action potential such that the threshold potential is not reached.
- Interact directly with specific receptors on the Na+ channel, inhibiting Na+ ion influx
8
Q
lipid solubility effects?
A
increases potency (some increase in DOA too)
9
Q
protein binding effects?
A
higher protein binding = longer DOA
10
Q
_______ fibers are more easily blocked than _____ ones.
A
Thin
thick
11
Q
_______ fibers are more readily blocked than ______ ones. Why?
A
Myelinated
unmyelinated
-produce block only at Node of Ranvier
12
Q
Fibers for Sharp/fast pain, temp, touch (fine sensation)
A
C fibers
13
Q
Fibers for pressure touch
A
A beta
14
Q
Fibers for proprioception
A
A alpha
A beta
15
Q
Fibers for motor control?
A
A alpha
A gamma
16
Q
which fiber unmyelinated?
A
C fibers
17
Q
Sequence of blockade in order?
A
-ATP TP MVP
ATP - autonomic, touch, pain
TP - Temp and pain
MVP - motor, Vibration, pressure (deep)
18
Q
Esters:
- Broken down by?
- metabolite?
- half-life?
A
plasma cholinesterase
PABA (p-aminobenzoic acid)
1 minute in circulation
19
Q
Amides:
- Broken down by?
- concerns?
- half-life?
A
- Through N-dyalkylation followed by hydrolysis
- severe hepatic disease
- 2-3 hours
20
Q
CSF has a specific gravity of ?
A
1.003–1.009
21
Q
difference b/w hyper/hypo/isobaric
A
hyper - floats downward
hypo - floats upward
iso - stays put
22
Q
what does epi do for LAs?
A
- Prolong duration of anesthesia
- Decrease systemic toxicity by decreasing the rate of absorption
- Increases intensity of block.
- Decreases surgical bleeding.
- Assist in evaluation of test dose. To assure correct location
23
Q
when not to add epi:
A
- Peripheral nerve blocks in areas with poor collateral circulation (e.g. finger, toes).
- IV regional technique (bier block).
- History of severe uncontrolled HTN, CAD, arrhythmia, hyperthyroid, utero-placental insufficiency.
24
Q
adding Bicarb:
A
- Raises the pH and increases the concentration of non-ionized (free) base.
- Increases the rate of diffusion across the nerve membrane and speeds onset of neural blockade.
- 1mEq added to each 10ml of lidocaine or mepivacaine.*
- 0.1mEq added to each 10ml of bupivicaine (to avoid ppt of the drug).*
25
adding an opioid:
- Addition of 50-100ug of fentanyl to the local anesthetic shortens the onset, increases the level and prolongs the duration of a regional block.
- A selective action at the dorsal horn of the spinal cord modulates pain transmission.*
- Action is synergistic with the action of the local anesthetic
26
when can an Amide cause an allergic reaction?
If a methyl-paraben preservative is used, it may produce allergic reaction in someone allergic to PABA
27
when can an Ester cause an allergic reaction?
- may cause allergic reaction due to metabolite similar in structure to PABA.
- Also may produce allergic reaction in persons sensitive to sulfonamides or thiazide diuretics.
28
Result of accidental intravascular injection or overdose of local anesthetic. Can be minimized by :
- Aspiration prior to injection
- Use of epi-containing solutions for test dose
- Use of small incremental volumes to establish the block
- Use of proper technique during IV regional (bier block)
29
CNS Toxicity:
Lightheadedness
Tinnitus
Metallic taste
Visual disturbance
Numbness of tongue and lip
May progress to:
- Muscle twitching
- Loss of consciousness
- Grand mal seizure
- Coma
- death
30
what to do if pt starts to seize?
blow of co2 (convusive threshold higher in lower pt co2)
31
treatment of CNS toxicity?
-Administer o2
- Midazolam 1-2 mg
- Thiopental 50-200mg
- Propofol
32
CV toxicity:
Decreased contractility
Decreased conduction
Loss of peripheral vasomotor tone
33
Intravascular injection of _________ or ________ may
result in cardiovascular collapse that is refractory to
therapy because of the high degree of tissue binding of
these agents
bupivacaine
etidocaine
34
Lipid emulsion therapy dosing:
Bolus 1.5ml/kg over 1 minute
continuous infusion 0.25 ml/kg/min
repeat bolus to 3ml/kg q3-5mins
35
review slide 35
review it!!
36
benefits of regional anesthesia:
- venous thrombosis
- pulmonary embolism
- cardiac complications
- vascular graft occlusion
- respiratory depression and pneumonia
- blood loss and transfusion
- allows earlier return of GI function
37
Skin infection at the site of injection increases the risk of?
meningitis or epidural abscess
38
factors that increase the risk of infection include:
- skin conditions such as psoriasis
- underlying sepsis
- diabetes
- immunologic compromise
- steroid therapy
- history of HIV or herpes simplex virus
39
contraindications to Regional anesthesia
- Patient refusal
- Patient lack of cooperation
- Increased intracranial pressure
- Significant preexisting or therapeutic coagulopathy
- platelet count less than 100K and PT, aPTT greater than two times normal values
- Skin infection at the site
- Hypovolemia
- Spinal cord disease
- Pt’s with a fixed volume cardiac state such as IHSS or severe aortic stenosis
- Long surgical time
- Difficult airway
- Musculoskeletal deformities, kyphosis, scoliosis, previous spine fusion
- Preexisting peripheral neuropathies - secondary insult - precise documentation of preexisting deficits
40
Do herbal supplements alone increase risk of spinal hematoma?
no
41
s/s spinal/epidural hematoma?
New onset weakness to lower limbs and sensory deficit
New onset back pain
New onset bowel or bladder dysfunction
Or anesthetic doesn’t wear off, or comes back then gets numb
(Must diagnose and surgically decompress hematoma within 8 hours for best outcome)
42
t12 level surgery?
lower extremities
43
t10 level surgery?
- Hip
- Vagina/uterus
- Bladder/prostate
44
t8 level surgery?
- Lower extremities/TQ
| - Testis/ovaries
45
t6 level surgery?
lower intraabdominal
46
t4 level surgery?
other intraabdominal
47
how many vertebrae each column?
```
7
12
5
5
4
```
48
connects apices of spinous processes.
Supraspinous ligament
49
connects the spinous processes.
Interspinous ligament
50
connects the caudal edge of the vertebra above to the cephalad edge of the lamina below.
Ligamentum flavum
| innermost ligament
51
Spinal needles are placed below ___ as the mobility of spinal nerves reduces the danger of needle trauma.
L2
52
spinal cord meninges
- Pia mater inner most
- Arachnoid – lies between the dura and the pia mater. Middle
- Dura mater – tough fibrous sheath running the length of the cord. Outer
53
Total volume of CSF is ?
Volume of CSF in spinal canal is?
~140 ml.
30-80 ml
54
CSF is formed predominantly by the _____ plexuses of the _________.
choroid
cerebral ventricles
55
Much of the CSF is reabsorbed by the _______ granulations along the ___________ to regulate the CSF pressure to _______ cm H2O pressure.
arachnoid
sagittal sinus
10-20
56
what does adjusting drug volume do?
| what does turbulence do?
will spread further into CSF
turbulence increases the spread of the drug and the level of blockade obtained.
57
what does increased intraabdominal pressure do to meds?
reduces the volume of CSF. Local anesthetic spreads farther
58
difference in baricity is difference in ?
specific gravities of fluids mixed together
59
what makes an LA hyperbaric?
- dextrose 5-8%
| - baricity/specific gravity >1.0015
60
what makes an LA hypobaric?
- mixing drug with sterile water
| - baricity/specific gravity <0.999
61
needles for spinal anesthesia in sizes from ______ gauge and in lengths of _____ inches
22-29
3.5 - 5
62
what level is illiac crest? what is this line called?
as high as L3-L4 to as low as L5-S1
the intercristal line or Tuffier’s line
63
Paramedian approach:
Useful in patients who cannot be maximally flexed or whose intraspinous ligaments are ossified.
Spinal needle is placed 1-1.5 cm lateral to midline of selected interspace.
Needle is aimed medially and slightly cephalad and passed lateral to the supraspinous ligament.
64
Spinal anesthesia is usually administered at interspaces?
L2-L3, L3-L4, or L4-L5
65
Fixation of local anesthetic takes approximately ___ minutes.
20
66
which fibers are more easily blocked?
C fibers
67
2 segments higher than sensory blockade.
Autonomic blockade
68
2 segments higher than motor blockade.
Sensory blockade
69
2 segments lower than sensory blockade.
Motor blockade
70
Neural Block order
Autonomic > Sensory > Motor
71
look at slide 85
do it
72
Risk of bradycardia increases with increasing ______ levels of anesthesia.
sensory
73
Treatment of CV response
Fluid load with 500-1000cc IV prior to spinal blockade if history allows. (15ml/kg 15 mins prior to anesthetic - Dextrose free)
Oxygen mask
Vasopressors - ephedrine is a mixed alpha and beta agonist is the agent of choice for symptomatic brady and hypotension. Direct acting Phenylephrine alpha agonist
Atropine 0.4-0.8
CPR
Epinephrine
74
The clinically important factors effecting level of anesthesia that can be controlled by the anesthetist are:
Total dose of anesthetic
Site of injection
Baricity of the drug (drug choice)
Position or posture of the patient after injection
75
Complications of Spinal Anesthesia
- Failure of block
- Post – dural puncture headache (pg. 1060)
- Nausea – (pg. 1062)
- Urinary retention – (pg. 1062)
- High spinal
- Hypoventilation
- Backache
76
what does an epidural work on once injected
- Nerve roots that are covered by the dural sheath (epidurals need larger doses than spinals b/c uptake through dura)
- Onset of block is slower and intensity is less
- Provider has greater control of sensory and motor blockade
77
two techniques to use in a lumbar epidural?
| differences in thoracic vs lumbar?
loss of resistance
hanging drop
- smaller dose thoracic
- more of an angle thoracic (more cephalad)
78
The test dose for epidurals
consists of 3ml of local with 1:200,000 epi
-little effect if in epidural, rapid effect if in CSF, if in bloodstream, 20-30% HR seen
79
does position effect epidurals?
no
80
All solutions should be injected in increments of ____ ml, every __ minutes and titrated to the desired anesthetic level.
3-5
3
