Principles of Anesthesia Practice I Unit I Flashcards
1
Q
What are the clinical indications for neuraxial anesthesia?
A
Surgical procedures involving the lower abdomen, perineum, and lower extremities, Orthopedic surgery, Vascular surgery on the legs, Thoracic surgery (adjunct to GETA)
2
Q
What are the benefits of neuraxial anesthesia?
A
Decreased narcotic usage, less bleeding, lower respiratory complications, lesser chance of PONV, decreased thromboembolic events and less chance of post-op ileus
3
Q
What are the “other” neuraxial anesthesia benefits listed in lecture?
A
Better/faster mental alertness, less urinary retention (can vary based on the patient), quicker to eat/void/ambulate, avoid unexpected admission to hospital d/t GA, quicker PACU DC (variable based on hospital policy), blunts stress response from surgery and pre-emptive analgesia/anesthesia
4
Q
What are some relative contraindications to neuraxial anesthesia?
A
Deformities of spinal column
Spinal stenosis, kyphoscoliosis, ankylosing spondylitis
Preexisting disease of the spinal cord
Exacerbate a progressive, degenerating disease like MS or post polio syndrome
Chronic headache/backache
Inability to perform SAB/Epidural after 3 attempts
5
Q
What are absolute contraindications to neuraxial anesthesia?
A
Coagulopathy (INR greater than 1.5, platelets less than 100,000 or PT/PTT x2 from baseline), coagulation disorder or on anticoagulants, patient refusal, evidence of dermal site infection, severe valvular disease, HSS (idiopathic hypertrophic subaortic stenosis), surgery duration greater than duration of LA, increased ICP, severe CHF (EF less than 30-40% and/or preload dependence)
6
Q
What is the pneumonic to remember the intrinsic/extrinsic pathways?
A
E: for 37 cents you can purchase this pathway (factors 3 and 7)
I: you can’t buy the intrinsic pathway for 12$, but you can buy it for 11.98 (factors 8, 9, 11 and 12)
7
Q
What is the pneumonic to remember the common pathway?
A
The common pathway can be purchased at the five and dime for one or two dollars on the 13th of the month (factors 1, 2, 5, 10 and 13)
8
Q
At what mean valve area is aortic/mitral valvular disease severe? Critical?
A
Severe = 0.7 - 1.0 cm sq
Critical = less than 0.7 cm sq
in general, if less than 1.0 cm sq, it is severe disease and a contraindication to anesthesia
9
Q
Describe the onset, spread, nature of block, motor block and chances of hypotension with spinal vs epidural
A
Spinal: Rapid onset, higher spread, dense/more profound nature of block and motor block with likely hypotension
Epidural: Slow onset, more controlled spread (reliant on volume of LA), the nature of the block is segmental with minimal motor block and less chance of hypotension than spinal
10
Q
What type of neuraxial anesthesia is limited to the L3-S1 region?
A
Spinal
11
Q
What type of neuraxial anesthesia requires more skill to place?
A
Epidural
12
Q
What type of neuraxial anesthesia is dose based?
A
Spinal
13
Q
What type of neuraxial anesthesia is volume based?
A
Epidural
14
Q
What type of neuraxial anesthesia is dose based? Volume base?
A
Dose = spinal
Volume = epidural
15
Q
Describe the difference in concentration of an LA with spinal vs epidural
A
Spinal = concentrated and fixed
Epidural = varies
16
Q
Describe the incidence rate LA toxicity (in general terms) of spinal vs epidural
A
Spinal = little to no chance of LA toxicity
Epidural = carries risk of LA toxicity
17
Q
How does gravity influence a spinal? Epidural?
A
Spinal = depends on the baricity of the LA
Epidural = depends on the patient position
18
Q
How would you manipulate the dermatome spread of an epidural vs spinal?
A
Spinal = the baricity, patient position and dose to dictate spread
Epidural = incremental dermatome spread based on volume, generally 1-2 ml per segment
19
Q
How many vertebrae are there? Describe how many are at each level
A
33
Cervical = 7
Thoracic = 12
Lumbar = 5
Sacral = 5
Coccyx = 4 total
20
Q
What drug can mitigate epidural related hypotension?
A
Zofran
21
Q
The symptoms of severe valvular disease include angina, syncope and heart failure/SOB, which are correlated with what survival lengths?
A
Angina = 5 year survival
Syncope = 3 year survival
Failure/SOB = 2 year survival
22
Q
What structures link the the anterior/posterior segments of the vertebrae?
A
The lamina and pedicle
23
Q
What space houses the spinal cord, nerve root and the epidural space?
A
The vertebral foramen made up by the connections between each vertebrae
24
Q
What is the primary spinal landmark used in neuraxial anesthesia?
A
The spinous process
25
Which vertebrae have a caudal orientation? Horizontal?
Caudal = cervical and thoracic
Horizontal (ish) = lumbar
26
In relation to the intervertebral foramen, what makes up the anterior/posterior aspects?
Anterior = vertebral body and intervertebral disc
Posterior = facet joints
27
What occurs with disc degeneration?
Narrowing of the foramen which can press on the spinal nerves causing pain/weakness/NT
28
At what level is the vertebral prominens?
C7
29
At what level is the root of spine of scapula (spinous process of scapula)?
T3
30
At what level is the inferior angle of the scapula?
T7
31
At what level is the superior aspect of the iliac crest?
L4
32
At what level is the posterior superior iliac spine?
S2
33
At what level does the intercristal line usually occur in adults? Infants?
Adults = L4
Infants = L5-S1
34
What is the caudal access point for neuraxial anesthesia?
The Sacral Hiatus
35
What is the incomplete part of the sacrum bridged only by ligaments?
S5
36
What landmarks help guide accessing the sacral hiatus for caudal anesthesia?
The sacral cornu
37
Where does the spinal cord originate and end?
Originates in the medulla and ends at the conus medullaris, roughly about L1 or L2
38
Per lecture, where does the spinal cord end in adults? Infants?
Adults = L1
Infants = L3
39
Describe the origin and endpoint of the cauda equina
Origin = tip of the conus medullaris and ends around S5 after the dural sac has ended
40
What levels would you find the cauda equina?
L2 - S5
41
What makes up the cauda equina?
Nerve roots and the coccygeal nerve
42
What is the end point of the dural sac in adults? Infants?
Adults = S2
Infants = S3
43
Where does the subarachnoid space end?
At the end of the dural sac (so S2 in adults, S3 in infants)
44
Describe the filum terminale
A continuation of the pia mater that extends from the conus medullaris to the tail bone and anchors the spinal cord in place
45
Describe the internal and external filum terminale
Internal = begins at the conus medullaris and extends to the dural sac (L1 or L2 to S2)
External = starts from the dural sac and extends into the sacrum (S2 to S5)
46
What is the primary blood supply for the motor function of the cord?
Anterior spinal artery
47
What is the primary blood supply for the sensory function of the cord?
The posterior (2 of them) spinal arteries
48
What do most of the anterior/posterior spinal arteries originate from?
Vertebral arteries
49
Why are the posterior spinal arteries more resistant to ischemia?
The have much more collateral circulation than the anterior spinal artery (from the subclavian and intercostal arteries)
50
Where is the anterior spinal artery most likely to receive additional branches of blood vessels from?
the intercostal and iliac arteries
51
What are common causes of spinal cord ischemia?
Profound hypotension, mechanical blockage, blood vessel disease (vasculopathy) and bleeding
52
What crucial connection helps supply blood to the lower 2/3 of the spinal cord?
The great radicular artery (artery of adamkiewicz)
53
Where can the great radicular artery emerge from?
Anywhere from the T9 - L2 regions, highly variable throughout the population
54
Starting from out to in, list the spinal ligaments
Supraspinous, interspinous, ligamentum flavum, posterior longitudinal and anterior longitudinal
55
What layers are skipped when using a paramedian approach?
the supraspinous and interspinous ligaments
56
List the layers traversed during a midline insertion
Skin -> subQ fat -> supraspinous -> interspinous -> ligamentum flavum -> dura mater -> subdural space -> arachnoid mater -> subarachnoid space
57
Common indication for a paramedian approach?
When the interspinous ligament is calcified or the patient cannot flex their spine
58
What angle is ideal for a paramedian approach?
15 degrees off midline, 1 cm lateral and 1 cm below the vertebrae
59
List the meningeal layers from outer to inner
Dura mater, arachnoid layer and pia mater
60
Where is the epidural space?
In between the dura mater and the ligamentum flavum
61
Per lecture, what 2 medications are contraindicated in spinals?
Reglan and zofran
62
What type of neuraxial anesthesia can be placed at any level?
Epidural
63
What angle would you anticipate needing to use for accessing T6/7?
about 40 degrees or a cephalad approach
64
What do spinal nerves exit from?
Intervertebral foramina
65
Per lecture, what is a good anatomic location for thoracic anesthesia (give level and anatomic landmark)?
T7, the inferior angle of the scapula
66
What are the 2 names for the horizontal line drawn across from L4?
Intercristal line or Tuffier line
67
What ligament connects the coccyx and sacrum and covers the sacral hiatus?
Sacrococcygeal ligament
68
In an adult, what is the lowest level you could find CSF? Infant?
Adult = S2
Infant = S3
69
Piercing what ligament indicates entry into the epidural space?
Ligamentum flavum
70
List the layers you want to pierce if you are doing a spinal?
Skin -> subQ fat -> supraspinous ligament -> interspinous ligament -> ligamentum flavum -> dura mater -> subdural space -> arachnoid mater -> then you are in the subarachnoid space
71
What approach is most common with thoracic neuraxial axis?
Paramedian
72
What supplies blood to the anterior 2/3 of the spinal cord?
Anterior spinal artery
73
What is the name for the epidural veins? What distinguishes them from other veins?
Batson's plexus. They are valveless and form a plexus that drains blood from the cord and its linings. Their density increases laterally
74
What do conditions like pregnancy or obesity do to Batson's plexus?
They engorge the veins, increasing the risk of needle puncture
75
What anatomic feature may explain the presence of a unilateral block related to an epidural insertion?
Plica mediana dorsalis
76
What layer would you pierce during a spinal if you kept advancing the needle after entering the sub-arachnoid space?
Pia mater
77
What effects would occur with a spinal vs an epidural if administered in the subdural space?
Spinal = a failed block
Epidural = it can cause a "high spinal" effect, meaning the medication would have a greater than intended effect
78
Of the 3 meningeal layers, which is the most vascular?
Pia mater
79
List how many nerves each group of vertebrae (groups being cervical, thoracic etc) have
Cervical = 8
Thoracic = 12
Lumbar = 5
Sacral = 5
Coccyx = 1
80
What dermatome(s) innervate the anterior and inner surface of lower limbs?
L1 - 4
81
What dermatome(s) innervate the foot?
L5 - S1
82
What dermatome(s) innervate the medial side of the great toe?
L4
83
What dermatome(s) innervate the posterior and outer surface of lower limbs?
L5 - S2
84
What dermatome(s) innervate the lateral margin of the foot and little toe?
S1
85
What dermatome(s) innervate the perineum?
S2 - 4
86
What dermatome(s) innervate the umbilicus?
T10
87
What dermatome(s) innervate the inguinal region?
T12
88
What dermatome(s) innervate the clavicles?
C5
89
What dermatome(s) innervate the lateral parts of the upper limbs?
C5 - 7
90
What dermatome(s) innervate the medial sides of the upper limbs?
C8 - T1
91
What dermatome(s) innervate the thumb?
C6
92
What dermatome(s) innervate the hand?
C6 - 8
93
What dermatome(s) innervate the ring and little fingers?
C8
94
What dermatome(s) innervate the level of the nipples?
T4
95
What supplies the sensory innervation to the face?
CN V (trigeminal nerve), of that nerve, it has 3 branches, the ophthalmic nerve (V1), maxillary nerve (V2) and the mandibular nerve (V3)
96
What is the desired dermatome level for a perianal surgery or saddle block?
S2-S5
97
What is the desired dermatome level for a foot/ankle surgery?
L2
98
What is the desired dermatome level for a thigh/lower leg/knee surgery?
L1
99
What is the desired dermatome level for a vaginal delivery/uterine/hip/tourniquet/TURP?
T10
100
What is the desired dermatome level for a scrotal surgery?
S3
101
What is the desired dermatome level for a penile surgery?
S2
102
What is the desired dermatome level for a testicular surgery?
T8
103
What is the desired dermatome level for a urologic/gynecologic/lower abdominal surgery?
T6
104
What is the desired dermatome level for a C-section/upper abdominal surgery?
T4
105
What is the site of action in a spinal vs epidural?
Spinal = subarachnoid space acting on the myelinated preganglionic fibers of the spinal nerve roots. Also inhibits neural transmission in the superficial layers of the spinal cord
Epidural = diffuses through the dural cuff to reach nerve roots (it can also leak into the para-vertebral area)
106
What factors can affect the spread of a spinal? Which do not?
Affect = baricity, patient position, dose and site of injection, volume of CSF, increased intra-abdominal pressure (obese, pregnant), age
Does not affect = barbotage (repeated aspiration and reinjection of CSF), speed of injection, orientation of bevel, addition of vasoconstrictor and gender
107
What factors significantly affect the spread of an epidural? small effect on spread? No effect?
Significant = LA volume, level of injection and dose, pregnant, old age
Small = LA concentration, position, height
No effect = additives (they can change onset or duration but not spread), direction of the bevel, speed of injection
108
How would a spinal injection most likely spread from the lumbar region? thoracic? cervical?
L = spreads mostly cephalad
T = balanced in both cephalad and caudad direction
C = spreads caudad
109
List the nerve fibers in order of block onset
B -> C -> A delta -> A gamma -> A beta -> A alpha
110
If the level of T8 is blocked what would be the level of motor blockade? Sympathetic blockade?
Motor = T10
Sympathetic = T2 - 6
111
How many levels higher may the sympathetic block be from a spinal?
Sympathetic = 2 - 6 levels higher
112
What nerve fibers blocks first and recovers the slowest?
Beta fibers (sympathetic)
113
What nerve fibers block last and recover fastest?
A-alpha (motor function, proprioception)
114
List the sensations in order of blocked first to last
Temperature is blocked first, followed by pain then touch/pressure
115
What scale is used to evaluate patient movement after a spinal block?
modified bromage scale
116
What are the general CV effects from a spinal?
Everything decreases, pre/afterload, CO, HR
*note that CO initially increases after a spinal d/t the reflex of losing vascular tone, but CO is only briefly increased, it quickly drops*
117
What is the Bezold-Jarisch reflex? What nerve mediates this reflex?
It's a response to ventricular underfilling; it causes significant bradycardia. The vagus nerve
118
What drug can help mediate the Bezold-Jarisch reflex?
Zofran
119
What reflex, other than Bezold-Jarisch, can cause bradycardia after a spinal?
The reverse bainbridge reflex
120
What population is sudden cardiac arrest most likely to occur in after a spinal? Onset?
Young adults with high parasympathetic tone, and generally occurs 20 - 60 minutes after a spinal
121
What are the choice vasopressors in treating spinal related hypotension?
Ephedrine (if bradycardic) or Neo (if tachycardic)
122
In general, what are the spinal effects on the pulmonary system?
Minimal to no effects. There may be a small decrease in ERV that may cause patients to feel short of breath
123
What positions may be used with a paramedian approach?
Sitting, lying, or face down (there are far more viable positions for a paramedian approach than a midline approach)
124
What is the cranial and caudal border of the epidural space?
Cranial = the foramen magnum
Caudal = Near the the sacrococcygeal ligament
125
Describe the anterior, lateral and posterior borders of the epidural space
Anterior = the posterior longitudinal ligament
Lateral = on the sides near the vertebral pedicles
Posterior = the ligamentum flavum and close to the vertebral lamina
126
How many paired spinal nerves are there?
31
127
Which blockade requires a greater concentration of LA; sensory or autonomic?
Sensory, as sensory would be either C fibers or a subset of A fibers, they block later than the autonomic (pre-ganglionic B-fibers) which block first.
128
What receptors mediate the Bezold-Jarisch reflex? Where would you find them?
5-HT3 receptors in the vagus nerve and the ventricular myocardium
129
What information does the efferent and afferent aspects of the PNS of the GI tract transmit?
Afferent = transmits sensations of satiety, distension and nausea
Efferent = tonic contractions, sphincter relaxation, peristalsis, and secretion
130
At what level does sympathetic innervation to the GI tract originate?
T5 - L2
131
What information does the efferent and afferent aspects of the SNS of the GI tract transmit?
Afferent = visceral pain
Efferent = inhibits peristalsis and gastric secretion, vasoconstriction and sphincter contraction
132
What occurs to the sympathetic and parasympathetic activity of the GI system when neuraxial anesthesia is administered?
Due to sympathectomy, the SNS is decreased which allows the PNS to take over/become more dominant (causes more rest and digest rather than fight or flight)
133
Due to the sympathectomy from neuraxial anesthesia, what GI effects would you expect to occur?
Sphincters relax, increased peristalsis, smaller contracted gut with active peristalsis, increased chance (20%) of N/V, increased GI blood flow and reduced chance of ileus
134
At what level is sympathetic blockade of the bladder affected?
Above T10
135
How do neuraxial opioids cause urinary retention/incontinence?
They decrease detrusor contraction and increase bladder capacitance, combined allow for retention and incontinence (this is why foley's are generally indicated with neuraxial anesthesia)
136
When is the best time to administer neuraxial anesthesia in order to take advantage of the maximal benefit of suppressing the neuroendocrine surgical response from surgery?
Before surgical stimulus
137
What dictates LAs onset? Potency? Duration?
Onset = pKa
Potency = lipid solubility
Duration = %protein bound
138
What is the relationship of pKa and physiologic pH in regards to onset?
The closer you are to physiologic pH, the faster the onset should be as more of the LA remains in the nonionized state
139
List the routes of administration that have the least to most plasma concentration of an LA
Subq -> Sciatic -> Brachial -> Epidural -> Paracervical -> Caudal -> Intercostal -> Tracheal -> IV
140
If supine, where would you expect to find and iso/hypo/hyperbaric LA?
Iso = same level of injection with some caudal and cephalad movement
Hypobaric = rises above the point of injection or, rather, it floats
Hyperbaric = sinks within the CSF moving below the point of injection
141
If supine, where would you expect to find the greatest concentration of a hyperbaric anesthetic? Hypobaric?
Hypobaric = floats and goes to highest points, so C3 and L3
Hyperbaric = sinks and goes to lowest points, T6 and S2
142
Describe the metabolism/elimination of sub-arachnoid LAs
No metabolism occurs in the CSF, in order for elimination to occur they must be re-uptaken via vessels in the pia mater
143
Do lipophilic or hydrophilic LAs have a faster reuptake rate after a spinal?
Hydrophilic are faster, lipophilic are slower because they have a high affinity for the fat
144
Chloroprocaine has a fairly high pKa, yet has a very fast onset in epidurals (common to use this drug in OB), why is this?
They overcome the higher pKa by having a high concentration of 2-3% to overcome the high pKa (bupivacaine for example has a concentration of 0.5 - 0.75%)
145
How does the dose, in general, of a spinal change from a T10 dose to a T4 dose?
A T4 dose is higher than a T10 dose
146
How much does the inclusion of epi increase the duration of a SAB?
20 - 50% increase in duration
147
What metabolizes 2-3 Chloroprocaine? Is it an amide or ester?
Metabolism = plasma cholinesterase and it is an ester
*remember the trick from pharm, one I is an ester, two I's is an amide*
148
Describe how Epi can be used as a biomarker to determine if you are in an ideal place for an epidural
You use it to check if you are in an vein or not, if you give a small dose of epi, and have no change in HR, you can reasonably say you are not in a vein. If you give the epi, and have an increase in HR, you are likely in or near a vein
149
Why do you use incremental dosing when starting an epidural?
To avoid accidental high spinal (such as if you are in the subdural space) or hypotension from rapid autonomic blockade. It also mitigates LA toxicity concerns
150
What is the ratio of Bicarb and LA for appropriate alkalinization?
1 mEq of bicarb per 10 mL of LA
151
How does alkalization affect LA pharmacokinetics?
It increases the concentration of non-ionized free base, the rate of diffusion and the speed of onset
152
What is the relationship of concentration of an LA to onset/duration of an epidural?
In general, the higher the concentration the faster the onset and shorter duration. The lower the concentration, the slower the onset and the longer the duration
153
How much should the top-up dose be for an epidural? When do you administer it?
50 - 75% of the initial dose, and you give it before the block decreases more than 2 dermatomes
154
How does the degree of spread of an LA compare from the thoracic vs lumbar space?
The thoracic area is smaller which correlates to greater spread whereas the lumbar region is larger and correlates with with lesser spread
155
How does concentration affect an epidural?
Remember, volume is the most important factor in determining the spread of an epidural, so concentration won't change spread but it can affect how dense/strong the block is
156
What concentration would you expect in a walking epidural?
A lower concentration that knocks out pain but does not block the motor related fibers
157
How do opioids, A2 agonists and vasopressors work as neuraxial adjuncts?
Opioids = improve the analgesia/density of block but do NOT affect duration
A2 = improve density, duration and analgesia (must be noted that these are off label uses)
Vasopressors = extend duration only, no effect on analgesia/density
158
What is the target of neuraxial opioids?
The substantia gelatinosa of the dorsal horn (lamina 2)
159
Describe the duration, spread, onset, duration, systemic absorption and respiratory depression of hydrophilic vs lipophilic neuraxial opioids
Hydrophilic: Duration is longer, wider or more rostral spread, longer onset, less systemic absorption because it stays in the CSF with late occuring respiratory depression
Lipophilic: Duration is shorter with limited or less rostral spread, fast onset, more absorption by the body (goes into the fat then can reach circulation) with early respiratory depression
160
What are some dosing strategies to minimize pruritis from neuraxial opioids? Treatment?
Minimize the dose of morphine, less than 300 mcg if possible. You can give Zofran or Nubain too as prophylaxis.
Treatment = Narcan 0.1 (best choice), benadryl 25 - 50 mg or Buprenex
161
What hydrophilic opioid has the higher incidence rate of respiratory depression when given neuraxially?
Morphine
162
What is the incidence rate of urinary retention with neuraxial opioids? Treatment?
30 - 40% and zofran, narcan and phenergan
163
What combination of opioids has a very high incidence rate of urinary retention?
Fentanyl/sufentanil + morphine
164
Describe how our A2 agonists modify neuraxial anesthesia effects as an neuraxial adjunct
They intensify/prolong the block of both sensory and motor by ~1 hour. Watch for hypotension, sedation and bradycardia
165
What effect do constrictors have when mixed with tetracaine? Bupivicaine/lidocaine?
Tetra = profound increase in duration
Lido/Bupi = variable increase in duration
166
What is the timeframe to treat an epidural hematoma with evidence of ischemia?
Surgical decompression within 8 hours
167
Does stopping ASA as primary or secondary prophylaxis carry greater risk?
Secondary as 10% of acute CV syndromes are preceded by ASA withdrawal
*secondary events mean that the ASA is being used to prevent a recurrent event, whereas primary is being used to prevent a first event*
168
Guidelines to hold ASA?
High/intermediate risk = hold for 4 - 6 days
Low risk = no need to hold
Central neuraxial = no need to hold
All of the above is independent of the dose (guidelines are the same no matter if the dose is 81 or 325 of ASA)
169
Guidelines to hold NSAIDs?
High risk = hold for 5 half-lives
Intermediate = hold for cervical epidural steroid injection (ESI) and stellate ganglion block
Low = do not need to hold
Central neuraxial = no precautions
170
Guidelines to hold glycoprotein IIb/IIIa antagonists?
Integrilin or abciximab
Hold Integrilin for 4 - 8 hours
Hold Abciximab for 24 - 48 hours
Avoid neuraxial until platelet function has recovered
MOA = inhibits platelet aggregation via surface receptors
171
Guidelines to hold thienopyridine derivatives?
Plavix, Prasugrel or Ticlid
Plavix = hold 5 - 7 days
Prasugrel = hold for 7 - 10 days
Ticlid = hold for 10 days
MOA = inhibits platelet aggregation by blocking ADP transferase
172
Guidelines to hold unfractionated heparin?
Low dose (less than 5k) = hold 4 - 6 hours
Higher dose (less than 20k) = hold 12 hours
Therapeutic dose (greater than 20k or in pregnant patients) = hold 24 hours
MOA = blocking thrombin (factor 2) and factors 9, 10, 11 and 12
*if on UFH greater than 4 days, make sure you have a platelet count before any neuraxial anesthesia*
173
Guidelines to hold LMWH?
Check coags/platelets
Delay 12 hours after a prophylactic dose
Delay 24 hours after a therapeutic dose
MOA = inhibits factor 10a
Check anti-factor 10a if elderly or in renal insufficiency
174
Guidelines to hold a vitamin K antagonist?
Impairs vitamin K-dependent clotting factors: 2, 7, 9, 10
Hold for 5 days, check INR with goal less than 1.5
175
Guidelines for TPA?
Absolute contraindication to neuraxial anesthesia
176
Guidelines to hold DOACs?
Eliquis, Xarelto, Pradaxa
DC 72 hours prior to block, check factor 10a if needing to administer block before the 72 hours are up
MOA = inhibits factor 10a
177
Guidelines for herbal therapies?
Proceed with neuraxial if not on other blood thinners
178
Postdural puncture headache cause? Risk factors?
Failure of the dura to properly seal
Provider risk factors: more common from a Quincke needle, larger diameter needle, using air for LOR or perpendicular position to the spines long axis
Patient risk factors: young, female and pregnancy
179
Postdural puncture headache treatment?
Bed rest, NSAIDs, caffeine, epidural blood patch or Sphenopalatine ganglion block (SGB)
180
Guidelines for epidural blood patch and SPG block?
EBP = only give 48 hours post puncture, inject 10 - 20 cc of patients own blood in to the epidural space (90% success rate) if 2 patches don't work, consider other causes
SPG = soak a cotton swab with lidocaine or bupivacaine and insert the swab into the nose towards the back throat wall and leave it for 5 - 10 minutes
181
Does a spinal or epidural have a higher incidence rate of paresthesia?
Spinal
182
What should the provider do if paresthesia is encountered during a spinal?
Withdraw and redirect the needle, you may be off midline
183
What are appropriate interventions to a patchy spinal block? Unilateral block?
Patchy = avoid repeating spinal (neurotoxicity concerns), consider IV sedation or GA
Unilateral = adjust position, or start IV sedation or GA
184
Causes of post-spinal bacterial meningitis? Common causative organism?
Poor aseptic technique or there is already bacteria in the blood. Organism = streptococcus viridans (commonly found in the mouth and hands)
185
Ideal skin preparation to prevent post-spinal bacterial meningitis?
Alcohol and CHG
186
What factors can increase the risk of cauda equina syndrome?
High Concentration Local Anesthetics: Using 5% lidocaine in SAB
Microcatheters: These catheters deliver the drug on a small area, increasing risk of nerve damage by exposing the area with a high concentration of LA.
Whitacre 25/26 needle have been associated with this syndrome
187
Treatment of cauda equina syndrome?
Supportive care, if compression is a factor proceed with immediate laminectomy (goal is laminectomy within 6 hours)
188
What causes transient neurologic s/sx?
Improper positioning. Higher incidence with high concentration LAs, lithotomy position and outpatient surgeries (knee arthroscopy for example)
189
Treatment of transient neurologic symptoms?
NSAIDs, opioids and trigger point injections
190
What is the ideal method of epidural removal to reduce the chance of fragment retention?
Withdraw the needle and the catheter at the same time to prevent shearing
191
What steps should you take if you meet resistance when dc'ing an epidural?
Reposition patient (ideally in the original position of insertion or in lateral decubitus), apply gentle/continuous traction, or tape the catheter to the skin and gently pull
192
What steps do you take if you see blood in the epidural needle?
Likely too far lateral, withdraw the needle and reposition to midline.
193
What steps do you take if you see blood in the epidural catheter?
If you pull blood when using the catheter, slightly pull it back and flush with saline, continue until no more blood is drawn or if the catheter can't be adjusted further safely
194
What intervention before you insert the epidural catheter can help prevent epidural vein cannulation?
Pre-inject saline, this widens the epidural space and reduces the chances of hitting a vein
195
Risk factors for epidural vein cannulation?
Multiple attempts, pregnant or stiffer catheter. Trauma to the epidural vein during the block may also contribute
196
If unilateral epidural block is suspected, what are some common causes? Treatment/solution?
Inserted too far allowing the catheter to exit through the intervertebral foramen or the catheter tip may be too close to a nerve
Solution = adjust catheter, pull out by 1 - 2 cm, ensure at least 3 cm is left in the epidural space, reposition patient, give more anesthetic and last ditch effort is replace the catheter
197
What type of block is LAST most prevalent in?
Peripheral blocks
198
What can increase the risk of CNS toxicity related to LAST? Decrease?
Increase = hyperkalemia, hypercarbia and metabolic acidosis
Decrease = hypocarbia, hypokalemia and CNS depressants
199
Why is bupivacaine so cardio-toxic?
It has a high affinity for voltage gated Na channels, and dissociates very slowly
200
LAST treatment?
100% oxygen, treat seizures (Benzos > propofol), modified ACLS (minimize epi to less than 1 mcg/kg if possible), and lipid emulsion therapy
201
Describe the dosing guidelines for lipid emulsion therapy
Over 70 kg = 100 ml bolus over 2-3 minutes, followed by a 250 mL infusion over 15-20 minutes. Repeat or double if unstable
Under 70 kg = Start with a 1.5 mL/kg bolus for 2-3 minutes, followed by a 0.25 mL/kg/min infusion. Repeat or double if unstable.
In both scenarios, continue the infusion until 15 minutes after patient becomes stable. 12 ml/kg max
Last ditch effort if all else fails is ECMO
202
What are risk factors for an epidural/spinal hematoma?
Preexisting abnormalities in clotting hemostasis, traumatic or difficult needle placement, indwelling catheters and long-term anticoagulation
203
What is the major sign to watch out for that can indicate an epidural/spinal hematoma?
Pain is the major symptom
204
What are some common causes of arachnoiditis?
Inflammation of the meninges due to; Nonapproved administration of drug into intrathecal or epidural space (medical error), Using non-preservative free solutions, Betadine contamination (wipe off)
All can cause extensive sclerosis of arachnoid membranes and constriction of vascular supply
205
Spinal cord injuries that cause ulnar nerve damage are more common in what patients?
Patient's on anti-coagulation or chronic pain patients
206
What LA is commonly used to anesthetize the skin?
1% lidocaine, usually ~5 ml
207
What is the function of the stylet when doing a spinal?
To prevent microclots
208
What are our cutting needles?
Quincke and Pitkin (both are more likely to cause a post-dural puncture headache than non-cutting needles)
209
Advantages of a pencil-point tip in a SAB?
Drags fewer contaminants into tissue, the click/pop can be sensed, less risk of PDPH (less than 1%) and failure rate of ~5%
210
Common problems encountered during SAB?
Lack of free flow CSF when spinning 360 degrees (generally means you need to advance the needle), no swirl (advance or redirect needle), resistance with injection (in the wrong spot) paresthesia (again, wrong spot, readjust to go more midline) no block (check expiration of LA)
*remember, swirl only occurs if your solution is hyperbaric*
211
Describe the 4 types of epidural needles
Tuohy: most curvature (30 degrees) blunt tip is less likely to puncture subarachnoid space
Hustead: 15 degree curve
Crawford: preferred when catheter placement is difficult or the angle is steep (thoracic epidural). 0 degrees curvature.
Weiss: 15 degree curve and it has the “wings”
212
Describe how to measure distance on a Tuohy needle
Each mark is 1 cm, the hub counts as 1 cm and the window below the hub is another 1 cm mark
213
What are the advantages of multi-orifice catheters?
Lower incidence of inadequate anesthesia d/t better distribution of LA spread
*downside is a higher incidence of inadvertent intravascular placement*
214
What are the characteristics of a flextip or plastic epidural catheter?
Easier to thread, inadvertent SAB puncture is a possibility, stiffer, less expensive
215
If you see 2 marks on a Tuohy needle when you encounter LOR, and thread 5 cm of epidural catheter into the epidural space, what is the distance of skin to epidural? Total amount of catheter threaded?
7 cm skin to epidural space + 5 cm threaded = 12 cm total of epidural catheter threaded/secured at the skin
216
What are the recommendations for an epidural if there is a tattoo on the lumbar spine?
Try to avoid placing the needle through tattooed skin.
If needed, avoid "nicking" the skin
Best to perform this within 5 months of the tattoo application for safety.
217
What are the 2 highlighted steps from the powerpoint that differentiate an epidural from a spinal?
You check for LOR using a special syringe and you use a test dose of 1.5% lidocaine with epi
218
What would occur during the epidural test dose if you cannulated a vein? In the sub-arachnoid space?
Vein = 20% increase in HR
Arach = dense motor block within 5 min of a test dose
*for the arach, replace the catheter. If a patient is on heart medications, watch for an increase in BP rather than HR. If pregnant, avoid giving the test dose during a contraction*
219
If you insert a needle in the L3 epidural space, and want to anesthetize up to T4, how much anesthetic would you give?
1-2 ml per segment, 11 - 22 ml of La
220
What is best practice when injecting LA into an epidural?
Maintain accurate dermatome assessment, aspirate for blood/CSF, inject slowly and no more than 5 ml at a time and monitor closely for ~30 minutes (to watch for unexpected dermatome spread)
221
what are the recommended top up timing doses for lidocaine, chloroprocaine, mepivacaine, bupivacaine and ropivacaine?
Chloroprocaine = 45 min
Lidocaine and Mepivacaine = 60 min
Bupivcaine and Ropivacaine = 120 min
222
What is a common cause of a false + test dose for an epidural?
Contractions during labor can mimic the increase in HR
223
What are the 4 basic types of central neuraxial anesthesia?
Spinal, epidural, CSE and caudal
224
What is pickwick syndrome?
This is when morbidly obese patients experience SOB/dyspnea when laying flat (they lose ERV/FRC and tend to panic)
225
What LA class has more allergy concerns?
Esters d/t PABA
226
What LA class has cross-sensitivity to each other?
Esters (this does NOT occur with amides)
227
Of these spaces, epidural, subdural and subarachnoid, which spaces should not have any veins?
Subdural and subarachnoid
228
Of these spaces, epidural, subdural and subarachnoid, which spaces should contain fat and veins?
epidural
229
In an epidural kit you have glass vials with medications, what medication is the color orange? Red? Blue?
Orange = epi
Red = test dose
Blue = 1% lidocaine for skin infiltration
*white is briefly mentioned in lecture, however Tubog was unsure to the exact nature of it and speculated it was likely another vial of LA*
230
What is the minimum timeframe to get a new set of vitals?
At least q5min
*in practice, it's generally closer to q3min*
231
What steps must you take if you decide to use or not use a monitoring system that is a standard of care?
Omission with reason must be charted
*you have to chart/justify your reasoning, especially if it goes against a standard of care*
232
What conditions/molecules cause a left shift? Right?
Left = less metabolic demands and byproduct creation. Alkalosis, hypocarbia, hypothermia, decreased 2-3 DPG, carboxy-Hgb, fetal Hgb
Right = increased metabolic demands and byproduct creation. Acidosis, hypercarbia, hyperthermia, increase 2-3 DPG
233
How do carboxy-Hgb and Fetal Hgb differ from adult Hgb?
They have a higher affinity to O2 (this is an example of a left shift in oxygen affinity)
234
What PaO2 correlates to a sat of 90%? 75? 50?
90 = PaO2 of 60
75 = PaO2 of 40
50 = PaO2 of 27
235
Describe Beer-Lambert in standard English, not the description on the slide that REEKS of first semester physics
Light absorption and transmission through a solution depends on the concentration of the solutes, and how much gets absorbed is measured at wavelengths proportional to the number of solutes
*so the more solutes you have, such as more Hgb, the less light that should get through*
236
Low concentration and low absorption is correlated with how much light absorption? High concentration/absorption?
Low concentration/absorption = minimal light absorption
High concentration/absorption = significant light absorption
237
What type of saturation monitoring is considered the gold standard if standard oximetry is inaccurate?
Co-oximetry
238
What type of light does deoxy-Hgb like to absorb? Oxy-Hgb?
Deoxy = absorbs more red light
Oxy = absorbs more infrared light
239
What estimates our arterial oxygen saturation when using a pulse oximeter?
The pulsatility of arterial flow
240
In relation to pulse oximetry, what is the AC? DC?
AC = absorption from pulsatile arterial flow
DC = absorption from non-pulsatile arterial, venous and capillary blood. Absorption from tissue also falls into this category
241
What happens to light absorption if the width of the artery increases/decreases?
Increases = more light gets absorbed
Decreases = less light gets absorbed
242
Why does carboxy-Hgb mimic adult-Hgb so well that it fools a pulse oximeter to give us a false normal/high reading?
Carboxy-Hgb absorbs as much light in the 660 nm range as Oxy-Hgb which gives us a falsely elevated SPO2
243
What is the relationship of carboxy-Hgb to changes in SPO2?
Each 1% increase in carboxy-Hgb should increase the SPO2 reading by 1%
*this is a false increase in SPO2*
244
Most smokers have how much carboxy-Hgb?
Greater than 6%
245
What are some examples of signal artifact with SPO2 probes?
Ambient light (alternating red/infrared usually solves this), low perfusion which reduces signal amplitude, venous blood pulsations, additional light absorbers (IV dyes), additional forms of Hgb or nail polish
246
Under what conditions does a pulse oximeter function best?
When the arterial saturation is greater than 70% it is accurate to +/- 2%
247
What are some disadvantages of a pulse oximeter?
Poor function with poor perfusion, delayed hypoxic event detection, erratic performance with dysrhythmias, inaccurate with different types of Hgb, inaccuracy with dyes, optical interference, nail polish/coverings, motion artifact
248
What areas could you apply a pulse oximeter to that are less sensitive to vasoconstriction?
Tongue, cheek and forehead
*the other advantage here is they reflect desaturation faster*
249
List the phases of Korotkoff sounds
Phase I: the most turbulent/audible (SBP)
Phase II: softer and longer sounds
Phase III: crisper and louder sounds
Phase IV: softer and muffled sounds
Phase V: sounds disappear (DBP)
250
What factors can limit the usefulness of auscultating BP?
Decreased peripheral flow (shock, vasoconstriction), changes in vessel compliance, incorrect cuff size, obesity
251
What does oscillometry measure?
It measures MAP from the maximal amplitude, SBP and DBP are calculated from an algorithm
252
Atherosclerosis, edema, obesity and chronic HTN produce what errors to non-invasive BP readings?
Low SBP and high DBP
253
What are the limitations of non-invasive BP monitoring?
Because they are estimations, they can underestimate MAP during HTN, overestimate MAP during hypotension and underestimate SBP/overestimate DBP
254
How would SBP/DBP change when using a forearm on an obese patient?
Overestimation of SBP and underestimation of DBP
255
What are some limitations of non-invasive BP?
Unsuitable in rapidly changing situations, complications (like compartment syndrome or pain, petechiae, venous stasis and peripheral neuropathy)
256
What are some continuous invasive BP monitoring indications?
Planned pharmacologic manipulation (pressors or cardene), repeated blood sampling, determination of volume responsiveness and for IABP counter pulsation
257
What is the difference between a radial vs brachial arterial catheter?
Brachial is longer
258
Describes the transfixion technique
Same prep/positioning as a radial arterial line, front and back walls are punctured intentionally, the needle is removed, the catheter is withdrawn until pulsatile blood flow appears and is then advanced
*it is not associated with more frequent complications*
259
What are some ways to maximize the arterial waveform?
Limit stopcocks, limit tubing length and use of non-distensible (pressure) tubing
260
What are the basic differences in the arterial waveform taken at the aortic arch vs the femoral artery?
Aortic arch has more "detail", earlier dicrotic notch and less height, the femoral artery has more height, later dicrotic notch and less "detail"
*by detail, I am referring to elements such as the dicrotic notch which is better defined in the aortic arch waveform*
261
Describe what waves make up the arterial line waveform
The fundamental wave and harmonic wave combine to make the summation wave (aortic waveform tracing)
262
What is fourier analysis?
Analysis of the summation of multiple sine waves
263
How many oscillations should you see after a square waveform test?
2
264
What conditions listed in lecture can change the pressure gradient?
Age (loss of distensibility), atherosclerosis, peripheral vascular changes, septic shock, hypothermia
265
Arterial line complications?
Distal ischemia or pseudoaneurysm, hemorrhage/hematoma, arterial embolization, infection, peripheral neuropathy
266
What is the goal of pressure wave form analysis? When can it be done?
Identify the presence of residual preload reserve (in english, seeing if you need fluid or not). It can only be done if the patient is intubated and under positive pressure ventilation
267
Describe the effects of PPV on the left/right sides of the heart
Inspiration: forces blood into the LV from the pulmonary circuit, decreases LV afterload and increases LV preload = increased LV SV, CO and arterial pressure. For the RV, the increased pressure decreases venous return/preload and increases RV afterload and PVR = decreased RV SV
Expiration: the decreased RV SV reduces LV preload, which reduces filling, stroke volume and arterial pressure. The RV preload increases, afterload and PVR decrease which increases RV SV
*the situations above are essentially the opposite of each other*
268
What is the normal systolic pressure variation (SPV)? How much should it increase/decrease?
Normal = 7 - 10 mmHg
Normal increase/up = 2 - 4 mmHg
Normal decrease/down = 5 - 6 mmHg
269
What does increased SPV indicate?
Early indicator of hypovolemia (increased SPV is usually from the "down" portion becoming exaggerated, creating the "swing" waveform that is suggestive of needing fluids)
270
What is the normal PPV?
Pulse pressure variation: normal is less than 13%, greater than 13% indicates the need for fluids
271
What is SVV?
Stroke volume variation, normal is 10 - 13%, greater than 10% indicates the need for fluids (per lecture, the slide is kind of confusing)
272
What values for SPV, PPV and SVV indicate the need for fluids?
SPV = increased or greater than 10 mmHg
PPV = greater than 13%
SVV = greater than 10%
273
What is the difference in duration between a spinal and an epidural?
Spinal duration is limited and fixed
Epidural duration is unlimited, you can run it for as long as you have the catheter in place
274
What dermatome(s) innervate the diaphragm?
C3 - C5
275
When supine, what are the highest points in the spinal cord? Lowest?
Highest = C3 and L3 (this is where hypobaric solutions would go)
Lowest = T6 and S2 (where hyperbaric solutions would sink to)
276
What is the relationship of the concentration of an epidural drug to block density?
The higher the concentration the stronger/more dense the block is
277
What factors does unfractionated heparin inhibit?
Thrombin (factor 2) and factors 9, 10, 11 and 12
278
What are 3 common reasons listed in lecture for failure of a spinal?
Wrong dose, wrong location or wrong position
279
What is the difference between side-stream and mainstream analyzers?
Side-stream, or diverting (more common) the gas is brought to the analyzer
Mainstream or non-diverting = the analyzer is brought to the gas (think fuel cell oxygen analyzer)
280
What are the sampling challenges of mainstream and side-stream analysis?
Mainstream = water vapor, secretions, blood and more interfaces for disconnections
Side-stream = kinking of sampling tubing, water vapor, leaks in the line, slow response time
281
What is the difference between mass spectrometry and raman spectroscopy?
Mass = the abundance of ions at specific mass/charge ratios is determined and is related to the fractional composition and can calculate up to eight different gases
Raman = uses an argon laser to produce photons that when measured in a spectrum identifies each gas and its concentration (not commonly used)
282
How does infrared analysis work?
It measures the energy absorbed from wavelengths of infrared radiation as it passes through the gas, this allows us to measure CO2, NO, water and volatiles. Each gas has a unique infrared transmission spectrum (think of this as a unique infrared fingerprint).
*the limitation of this is that it cannot measure oxygen as oxygen does not absorb infrared radiation*
283
What is the relationship of concentration and infrared light during infrared analysis?
High concentration of gas = less gets through
Low concentration of gas = more light gets through
284
Describe a fuel/galvanic cell vs a paramagnetic analyzer
Oxygen battery that measures the current produced when O2 diffuses across a membrane. The current is proportional to the partial pressure of oxygen. Slow response (30 sec) and is best to monitor O2 in the inspiratory limb
Paramagnetic = Detects change in the sample line d/t the attraction of oxygen by switched magnetic fields. Signal changes correlates with O2 concentration and gives rapid response and breath-by-breath monitoring
285
What does oxygen monitoring in the inspiratory limb measure? Expiratory limb?
I = ensures oxygen delivery to prevent the administration of a hypoxic gas mixture
E = measures the level of denitrogenation and end-tidal O2 (goal of 90%)
286
What are 2 scenarios where you do not want to hyperoxygenate?
Pre-term infants and patients on chemo drugs like bleomycin (high oxygen concentrations increases the likelihood of being exposed to oxygen related free radicals)
287
Describe the difference in mechanical and electrical pressure gauges
M = require no power/always on, it does not record data, no alarm system and you have to routinely check/scan it
E = built within the machine, has alarms and is sensitive to small changes
288
Where is a disconnection of the ventilatory circuit most likely to occur?
70% occur at the Y-piece
289
What is the primary purpose of the low pressure alarm?
To check/alert for circuit disconnection/leaks
290
What are some causes of sub-atmospheric alarms?
Suction scavenging system malfunctions, breathing against a blocked circuit, inadequate FGF, misplaced NGT/OGT suction and moisture in the CO2 absorbents
*these are dangerous because they can cause pulmonary edema, atelectasis and hypoxia*
291
What is the difference between high pressure and continuing pressure alarms?
High pressure is an obstruction of some sort, like coughing, kinked ET tube, endobronchial intubation or reduced lung compliance
Continuing pressure = fresh gas continues going into the circuit but can't leave causing pressure to exceed 10 cm H20 for greater than 15 seconds. This is caused by a faulty APL valve, scavenging system occlusion, activation of oxygen flush system or malfunctioning peep
292
What is the alternative to electrical nerve stimulation and why is it not commonly used?
Magnetic because it is bulky/heavy, no TOF stimulation and it's hard to achieve supramaximal stimulation
293
How do muscle fibers typically respond to supramaximal stimulation?
An all or none pattern, this response depends on how many muscle fibers are activated, if you activate enough, then you would get the twitch
294
What is the gold standard nerve for nerve stimulation?
Ulnar nerve
295
Describe how the diaphragm paralyzes relative to a smaller more peripheral muscle
It paralyzes faster and also recovers faster
296
What muscle reflects the extent of neuromuscular block of the laryngeal adductor and abdominal muscles better than the adductor pollicis?
The corrugator superfilii (this is a small muscle of the face)
297
What does hertz measure?
The amount of stimuli per timeframe, 1 Hz = one stimuli per second, 0.1 Hz = one stimuli every 10 seconds
298
What responses to stimuli do you compare when determining a TOF ratio?
The 4th response and the 1st response (4th response / 1st response)
299
Describe the TOF ratio in depolarized vs non-depolarized block
Depolar = no fade, ratio of 1
Non = exhibits fade, so ratio is going to be less than 1
300
In a nondepolarizing block when would the TOF ratio (or fade) be smallest? Greatest?
Smallest = early in the block (soon after drug administration) as your likely wouldn't get a 4th twitch, so the ratio would be 0
Greatest = late in the block, as the 4th twitch gets closer and closer to the first twitch you start to approach a 1:1 ratio
*at full recovery, the TOF ratio is likely either at 1 or very close to 1*
301
What is DBS 3,3 and DBS 3,2?
Both are modes of double burst stimulation, the first using 2 bursts of 3 impulses, the other using 2 bursts of 3 then 2 impulses respectively
*this is the "ideal" way to measure/compare muscle twitches but is not used much in clinical practice*
302
How do non-depolarizers and depolarizers respond to tetanic stimulation?
Depolarizer = no change in response/sustained muscle contraction
Non = One strong sustained muscle contraction followed by fade
303
Describe intense, deep and moderate non-depolarizing block. Include drug treatment.
Intense = period of no response. Neostigmine reversal is impossible, use 16 mg/kg of sugammadex
Deep = no TOF, but at least one post-tetanic response. Neo reversal is likely impossible, use 4 mg/kg of sugammadex
Moderate = gradual return of TOF, use neo after 4/4 TOF or 2 mg/kg of sugammadex
304
Describe phase I and II depolarizing blocks
Phase I = no fade, TOF ratio is 1.0
Phase II = fade is present or post-tetanic facilitation occurs (mimics non-depolarizing block, occurs d/t abnormal plasma cholinesterase activity or multiple/large dose of sux)
305
What is the minimum blockade goal for surgery?
Moderate level of blockade with 1-2/4 twitches
306
Describe the Hz range of Alpha, Beta, Delta and Theta signals
Alpha = 8 - 13 Hz
Beta = greater than 13 Hz
Delta = less than 4 Hz
Theta = 4 - 7 Hz
307
List Alpha, Beta, Delta and Theta signals in order of increasing Hz
Delta (less than 4) Theta (4-7) < Alpha (8-13) < Beta (greater than 13)
308
What is the basic difference between an EEG and processed EEG?
Processed EEG condenses down to 4 channels, 2 per hemisphere.
309
Describe the basics of the BIS monitor
It is a form of processed EEG using a computer generated algorithm to estimate anesthetic depth. Designed to help prevent intraoperative awareness
310
What must you do before doing a surgery that involves SSEPs?
Check a baseline before administering an anesthetic
311
What are SSEPs, BAEPs and VEPs?
S = somatosensory-evoked potentials
B = brainstem auditory-evoked potentials
V = visual-evoked potentials
312
What do SSEPs monitor? Which are more commonly monitored in the OR?
The response to stimulation of peripheral mixed nerves (both motor and sensory). Short-latency SSEPs are more commonly monitored
313
What is the basic difference in BAEPs and VEPs?
B = monitors response to auditory stimuli
V = monitors response to visual stimuli
314
What is the most common MEP?
Transcranial motor-evoked potentials (this monitors stimuli along the motor tract via transcranial electrical stimulation)
315
Why is electromyography used during high nerve damage risk surgery?
Because it allows for early detection of surgically induced nerve damage and assessment of the level of nerve function during the surgery
316
What fibers transmit heat information? Cold?
Heat = C-fibers
Cold = A-delta fibers
317
What is the primary thermoregulatory control center?
Hypothalamus
318
What 3 factors characterize the thermoregulatory threshold?
Threshold = temperature where a response will occur
Gain = the intensity of the response
Response = sweating, vasodilation, vasoconstriction and shivering
319
How much does anesthesia decrease temperature? How much is lost per hour?
Induction = 0.5 to 1.5 degrees celsius d/t vasodilation and heat loss d/t redistribution
you lose 0.3 degrees celsius/hour, GA decreases metabolic rate by 20-30%
320
How does neuraxial anesthesia affect temperature?
It inhibits the thermoregulatory control center, this decreases the thresholds that trigger peripheral vasoconstriction and shivering. It also impairs thermoregulatory defenses (like vasodilation, sweating, vasoconstriction, shivering)
321
Describe heat loss via radiation, convection, evaporation and conduction
Radiation = heat loss to the environment (40%)
Convection = loss of heat to the air (30%)
Evaporation = latent heat of vaporization of water from open body cavities and the respiratory tract (10%)
Conduction = heat loss due to direct contact with a much colder material
322
Complications of hypothermia?
Coagulopathy, increased need for transfusion and increased blood loss, decreased O2 delivery, x3 increase in cardiac outcomes, shivering, decreased drug metabolism and post-op thermal discomfort
323
Benefits of hypothermia?
Protective against cerebral ischemia, reduces metabolism (8% per degree celsius decrease), improved outcomes s/p cardiac arrest, helpful during neurosurgery when brain tissue ischemia is expected and more difficult to trigger MH
324
How much does a blanket reduce heat loss?
By 30% (does NOT increase body temperature)
325
Forced air warming uses what method to prevent heat loss?
It uses convection (transfer of heat via the air) to transfer heat to the patient
326
What is the gold standard for temperature monitoring?
Pulmonary artery temperature monitoring
327
What temperature does the the tympanic membrane reflect? Risk of using this method?
Approximates the temperature of the hypothalamus, the risk is perforation
328
What temperature does the nasopharyngeal reflect? Risk of using this method?
Brain temperature (more prone to error), the risk is epistaxis
329
What is the correct placement of the esophageal temperature probe? Advantages?
Placement in the distal 1/3 - 1/4 esophagus. It is safe, easily accessible, artifact-resistant and an accurate site
330
What is the normal OR temperature range?
18 - 21 degrees C, 65 - 70 F
331
What are some general effects of hypercarbia?
Respiratory acidosis, increased cerebral blood flow (watch ICP), increases pulmonary vascular resistance, K shifts to the intravascular space (think DKA patients, their potassium tends to be sky high, then you fix the DKA and they become hypokalemic)
332
What are some general effects of hypocarbia?
Respiratory alkalosis, decreases CBF, decreases pulmonary vascular resistance, K shifts to the intracellular space (think of when you fix DKA) and blunts normal urge to breath
333
Why can mild hypercarbia be useful when trying to recover someone from anesthesia?
Our drive to breath is primarily CO2 related, if you make your patient hypercarbic you can hopefully stimulate their drive to breath
334
What equation calculates physiologic dead space?
Bohr equation
335
What is the difference between anatomic and physiologic dead space?
Anatomic = the conducting zone, 150 cc for this class
Physiologic = is the total dead space of the anatomic + alveolar dead space
336
What conditions can increase alveolar dead space?
Hypovolemia, pulmonary hypotension, PE, ventilation of nonvascular airspace, obstruction of precapillary vessels, external obstruction, overdistension of the alveoli
337
What is the difference between capnometry and capnography?
Capnometry = Measurement and quantification of inhaled or exhaled CO2 concentrations
Capnography = graphical display of the measurement of CO2, detects CO2 breath by breath
338
Describe the basic difference of high/slow speed capnography
High speed = interpret the details of each breath
Slow speed = the inspired/expired trend
339
Which of these waveforms is high speed interpretation? Slow speed?
High = The individual waveforms on the left
Slow = The trend of inspired/expired CO2 on the right
340
What is the rate of side-stream analysis?
50 to 200 ml/min
341
What is #1?
The respiratory baseline, phase I
342
What is #2?
The expiratory upstroke or phase II
343
What is #3?
The alpha angle
344
What is #4?
The alveolar plateau or phase III
345
What is #5?
The beta angle
346
What is #6?
Where ETCO2 is measured
347
What is #7?
The inspiratory downstroke or phase 0 (some textbooks have it labeled as phase IV)
348
What can increase PETCO2?
Increased CO2 production (increased metabolic rate, many causes). Another one is bicarb administration, (remember it will dissociate into water and CO2 after combining with H+), decreased alveolar ventilation (such as a high spinal or COPD) and equipment malfunction
349
What can decrease PETCO2?
Decreased CO2 production (cardiac arrest, PE, hypotension) hyperventilation and equipment malfunction
350
What is the difference in mmHg between PaCO2 ands ETCO2?
Difference of 5 mmHg
351
What are some examples of breathing patterns that fails to deliver alveolar gas at the sampling site which increases the PaCO2 ETCO2 difference?
Neonate/infant breathing, COPD and bronchospasm
352
What VQ problems can exaggerate the PaCO2 ETCO2 difference?
PE and endobronchial intubation
353
What is the most common method capnographs use to measure CO2?
Infrared absorption (same concepts as before, the more infrared light that gets absorbed is directly proportional to the amount of CO2 present, the other way to look at this is the more CO2 you have, the less light that gets through to the detector)
354
How close must a capnograph be to the actual CO2 value?
+/- 12%
355
What should your differential diagnosis of the loss of ETCO2 include?
Esophageal intubation, accidental extubation, disconnection or failure of the sampling line/device, apnea, bronchospasm, or cardiac arrest
356
What are the inspiratory and expiratory segments of the capnograph waveform?
Inspiratory – Phase 0
Expiratory – Phases I, II, and III
357
What occurs during each phase of the capnograph waveform?
I = exhalation of the anatomic dead space (no CO2)
II = expiratory upstroke, starting to get some gas with CO2 (mix of alveolar and dead space gas)
III = plateau phase, primarily expiring alveolar gas with more CO2
0 = inspiratory downstroke, inspiration of fresh gas
358
What is the occasional phase IV?
This is occurs in pregnant/obese patients, lung units with less CO2 close which allows regions with more CO2 to contribute to the expired gas and briefly increasing the waveform (occurs very close to the beta angle)
359
What are the angle measurements of the alpha and beta angle?
Alpha = 100 - 110 degrees
Beta = 90 degrees
360
What increases the alpha angle?
Expiratory airflow obstruction such as COPD, bronchospasm or kinked ET tube
361
What increases the beta angle?
Malfunctioning inspiratory unidirectional valves, rebreathing, and low tidal volume with rapid respiratory rate
362
What is occurring in this waveform?
Mechanical ventilation
363
What is occurring in this waveform?
Spontaneous ventilation
364
What is occurring in this waveform?
Inadequate seal around the ET tube
365
What is occurring in this waveform?
Faulty inspiratory valve
366
What is occurring in this waveform?
Sample line leak
367
What is occurring in this waveform?
Hyperventilation
368
What is occurring in this waveform?
Hypoventilation
369
What is occurring in this waveform?
Airway obstruction
*The shark-fin appearance is a classic graphical sign of airway obstruction*
370
What is occurring in this waveform?
Cardiac oscillations
*common in pediatrics*
371
What is occurring in this waveform?
Rebreathing from soda lime exhaustion
*be VERY careful here, this looks very similar to faulty inspiratory valve, the key difference is the faulty inspiratory valve has that 90-degree angle right before phase 0, that angle is absent here*
372
What is occurring in this waveform? What is the name of the distinctive pattern before the beta angle?
NMBD's are wearing off, the notch is the curare cleft
373
What is occurring in this waveform?
Over breathing, the normal ventilator breaths are here, the waveform in between them is a patient spontaneous breath
374
Assuming the patient is currently hemodynamically stable, and has received anesthetics/paralytics, what would be a reasonable explanation for this waveform?
Esophageal intubation
375
What spot for SPO2 monitoring may be helpful with an epidural?
Toes
376
What is the acceptable deviation range for non-invasive BP cuffs?
+/- 5 mmHg, though deviations of up to 20 mmHg are acceptable
377
What would you expect to see after a square waveform test if the line was over-dampened? Under?
Over = less than 2 or no oscillations
Under = more than 2 oscillations and of greater amplitude
378
What are 3 surgical scenarios where you would turn up the OR temperature to try and keep the patient warm?
Liver transplant, pediatric surgery and major trauma
379
What nerves are affected by cauda equina syndrome?
L2 - S4 and the coccygeal nerves
380
What changes would you expect to MAP if the art-line is over-dampened?
The MAP should still remain fairly accurate
381
What oxygen analyzer is used in most side-stream sampling multi-gas analyzers?
Paramagnetic
382
With spinal anesthesia, what factor is most important in dictating the spread of a hypo/iso/hyper-baric solution?
Hypo and Iso = the dose
Hyper = the baricity
383
First effects of a spinal?
Autonomic gets knocked out first, so hypotension and bradycardia
384
What nerves does the modified bromage scale measure?
Lumbosacral
385
Per lecture, what method of fluid management does work in the prevention of spinal anesthesia related hypotension?
Co-loading IV fluid
386
What patient position must you try to avoid if you have given a hyperbaric spinal?
Trendelenburg
*hyperbaric sinks, if you go trendelenburg the medication could begin to sink towards the head*
387
Describe spread from an epidural
It is both cephalad and caudad from the catheter insertion site
