6. Neuro Flashcards
1
Q
what drugs are used to lower ICP
A
-mannitol
-hypertonic saline (3%)
2
Q
how do hyperosmotic drugs work
A
-transient increase in osmolality of plasma
-draws water from tissues (including brain) into plasma
-eliminated renally
3
Q
what are secondary effects of hypertonic drugs
A
-diuresis
-reduction in blood volume
4
Q
where is mannitol filtered at? what does this mean?
A
-filtered at glomerulus (not reabsorbed in PT)
-so prevents normal osmotic reabsorption of water
5
Q
SE of mannitol
A
-hyperosmolality
-hyponatremia
-hypokalemia
6
Q
dose of mannitol
A
0.25-0.5 g/kg
(some references say up to 1 g/kg)
7
Q
concentration of IV bag of mannitol
A
20% mannitol in 500 mL bag
20 g/100 mL
100 g per bag
8
Q
concentration of mannitol in vial
A
25% mannitol
25 g/ 100 mL
12.5 g/50 mL vial
9
Q
what happens if larger initial doses of mannitol are given?
A
may lead to rebound increase in ICP
10
Q
goal serum osmolality of mannitol
A
300-315 mOsm/L
11
Q
when to stop mannitol
A
if 320 mOsm/L is reached
12
Q
with mannitol, how much fluid is removed from the brain
A
100 mL
13
Q
with mannitol, how long does it take for ICP to be decreased
A
within 30 min (max effect 1-2 hours)
14
Q
with mannitol, how much UOP is there
A
1-2 L within 1 hour
15
Q
with mannitol, what is the duration of hyperosmotic effect
A
about 6 hours
16
Q
what needs to be monitored when giving mannitol
A
-serum osmolality
-UOP
-BP
-serum electrolytes
-may need tx with crystalloids and electrolyte solutions
17
Q
what is needed to be intact to give mannitol? why?
A
-intact BBB
-if disrupted, drug may cross and cause cerebral edema and increase brain size
18
Q
how can mannitol affect the heart
A
can cause symptomatic HF in pts with LV dysfx and poor cardiac reserve
19
Q
when should mannitol be avoided
A
-aneurysms
-arteriovenous malformations
-intracranial hemorrhage until cranium opened
20
Q
how is 3% sodium chloride IV administered
A
central venous catheter
21
Q
initial dose of hypertonic saline
A
1-2 mL/kg over 5 minutes
22
Q
target serum Na of hypertonic saline
A
145-155 mEq/L
23
Q
target serum osmolarity of hypertonic saline
A
<320 mOsm/L
24
Q
how often should serum Na and osmolarity be monitored while on hypertonic saline infusion
A
q6h
25
what can serum Na of 160 mEq/L cause
-renal injury
-pulmonary edema
-seizures
-cardiac dysfx
26
is mannitol or hypertonic saline considered a higher risk
hypertonic saline
27
use of loop diuretics (furosemide)
-sx associated with increased IV volume (pulm edema)
-can be used with mannitol and hypertonic saline for pt with CHF and nephrotic syndrome
28
what corticosteroids are used for ICP
dexamethasone or methylprednisolone
29
how do corticosteroids lower ICP
-causes upregulation of expression of proteins responsible for integrity of tight junctions btw endothelial cells constituting components of the BBB
30
what cause of ICP are corticosteroids useful for
-useful for ICP caused by localized vasogenic edema (brain tumor, craniotomy)
-not for head trauma
31
decadron dose for ICP
-10 mg IV immediately
-then 4 mg IM q6h until subsides
-may switch to PO after
32
what should be monitored with corticosteroids
BG for hyperglycemia
33
use of barbiturates for ICP
give in high doses, esp with increased ICP after acute head injury
34
use of propofol for ICP
-may be helpful
-use w caution for prolonged periods, esp in peds
-avoid high anion-gap metabolic acidosis
35
use of sedatives and opioids in ICP
-use sparingly -leads to hypoventilation -> hypercarbia -> further elevation of ICP
36
what is used for anesthetic induction for ICP
propofol or barbiturates (with modest hyperventilation)
37
paralytics for ICP
NDMR
38
use of sux for ICP
-can increase ICP
-may be used for RSI or diff airway though
39
during maintenance, what periods may require increased anesthetic requirements?
during stimulating periods (incision, dural opening, mayfield pin placement, closure)
40
what can be used during emergence
precedex -> used during asleep and awake cranis
41
fluid management for maintenance of anesthesia
IV fluid iso-osmolar (LR or 0.9% NaCl) maintain euvolemia
42
what to avoid in fluids
dextrose containing solution, can cause CNS ischemia and neuronal injury
43
during crani, what to give during pinning
-opioids: fent 50-100 mcg or remi 25-50 mcg
-prop: 20-50 mg
-esmolol: 0.25-0.5 mg
-lidocaine: 1 mg/kg
44
anesthetic depth during pre-incision prep for crani
light sedation (lines, positioning, skin prep, draping)
45
anesthetic management during incision, raising scalp, and bone flaps
-raise anesthetic level
-brain relaxation (shrinkage) may be needed prior to dural opening (mannitol, 3% NaCl)
46
anesthetic management when opening dura during crani
deep level of anesthesia (very painful, lots of pain fibers)
47
anesthetic management during intracranial procedure part of crani
lighter level due to brain tissue has no pain receptors (depends on procedure)
48
anesthetic management during wound closure of crani
-painful, but not as bad as incision
-opioids, acetaminophen, antihypertensives
49
premedication for cranis
versed 1-2 mg (in 0.5 mg increments)
50
SE of using propofol for induction for crani
-autoregulation and CO2 responsiveness maintained
-reduction in CBF and ICP
-may cause hypotension
51
SE of using methohexital for induction for crani
-activates seizure foci
-less hypotension than prop
52
SE of using etomidate for induction for crani
-does not decrease BP or CO
-preserves CO responsiveness
-single dose inhibits adrenal steroid production up to 24 hour AVOID!!!!!!!!!!!!!!!!!!!!!!!!!
53
SE of using ketamine for induction for crani
-conflicting data on cerebral physiology AVOIDDDD or use with caution!!!
54
for RSI and diff intubation, what NMB agents to give
-give sux for induction
-add in defasciculating dose of NDMR for ICP
55
defasciculating of the NMBs
roc: 2 mg
cisatracurium: 1.5 mg
vec: 0.3 mg
sux: 1.5 - 2 mg/kg
56
if elevated ICP, what should be used for maintenance
IV technique (prop, opioids, precedex) not volatile agents
57
which opioid should be avoided with ICP? why?
morphine -> histamine release
58
glycemic control during crani
110-150 g/dL treat if >180
59
BP goal during emergence
-SBP <160 (can cause postop intracranial hemorrhage)
-avoid hypotension (can cause cerebral hypoperfusion and ischemia)
60
use of long acting opioids (like dilaudid) during emergence of crani
avoid
61
dosing for labetalol
initial dose 0.2 mg/kg, then 0.4, 0.8, 1.6 q10 min
62
max dose for labetalol
do not exceed 200 mg/dose (max dose repeated up to 3 times)
63
how to give esmolol during crani
continuous infusion otherwise rebound HTN
64
how to give nicardipine during crani
need continuous infusion or combination with longer acting agent
65
how to tx hypotension during organ retrieval
-avoid vasoconstrictors!
-inotropes are preferred!
66
for organ retrieval, what are first and second line for inotropes
first: dobutamine, dopamine
second: low dose epi
67
management of heart retreival
minimize / avoid catecholamines
68
risks of catecholamines during heart retrieval
-catecholamine induced cardiomyopathy
-ECG abnormalities and dysrhythmias
69
how to tx diabetes insipidus during organ retrieval
inotropic support with vasopressin (0.04-0.1 units/h)
or
desmopressin (1-4 mcg)
70
what is a seizure
transient alteration of behavior due to disordered, synchronous, and rhythmic firing of populations of brain neurons
71
what is epilepsy
a disorder of brain fx with periodic and unpredictable occurrence of seizures
72
drug classes to tx seizures / epilepsy
-antiepileptic drugs (AEDs)
-antiseizure drugs
-anticonvulsants (basically, all the same thing)
73
MOA of antiseizure drugs
-modulation of Na+, K+, Ca+ channels
-enhance GABA transmission
-modulation of synaptic release through actions of synaptic vesicle protein SV2A (leviteracetam) or Ca channels containing alpha 2 delta subunit
-diminishing glutamate R (AMPA)
74
what do antiseizure drugs do to Na+ channels
prolongation of the inactivated state of voltage gated Na+ channels
75
what do antiseizure drugs do to K+ channels
positive modulation of K channels
76
what do antiseizure drugs do to Ca+ channels
inhibition of Ca channels
77
how do antiseizure drugs affect GABA
-enhance GABA transmission through actions on GABA R, modulation of GABA metabolism, and inhibition of GABA reuptake
78
which antiseizure drugs rely on renal elimination
-gabapentin
-levetiracetam
79
which antiseizure drugs induce CYP enzymes
-phenytoin
-carbamazepine
80
how do the antiseizure drugs of phenytoin and carbamazepine affect NMBs
-cause relative resistance to NMBs due to accelerated clearance of these drugs
- so need to give more NMBs
81
metabolism of phenytoin
-capacity limited (based on liver)
82
how do small changes of dosing in phenytoin affect the total concentration
small changes in dose lead to larger magnitude change in concentration (can easily lead to toxic concentration)
83
what dose of phenytoin exceeds the maximal clearance of the liver
300 mg/day
84
therapeutic range of phenytoin
10-20 mg/dL (free 1-2 mg/dL)
85
how to manage antiseizure drugs and surgery
continue antiseizure med periop
86
what are parenteral antiseizure drugs
-levetiracetam
-phenytoin and fosphenytoin
-valproate
-phenobarbital
87
dose of carbamazepine
2-4 times / daily
88
dose of valproic acide
1-3 times /daily
89
dose of phenytoin
1-2 times / daily
90
dose of levetiracetam
2 times / daily
91
which anesthetic drugs can induce seizures
-methohexital
-etomidate
-meperidine (metabolite normeperidine can cause seizures)
-laudanosine (metabolite of atracurium and cisatracurium)
92
what drugs can cause epileptiform EEG activity in pts w/o epilepsy but also suppress such activity
-alfentanil
-ketamine
-enflurane
-isoflurane
-sevo
93
causes of seizures in a periop pt
-drug and alc withdrawal
-acute neurologic injury
-intracranial and cerebrovascular surgery
-periop stroke (ischemic or hemorrhagic)
-CNS tumors
-metabolic derangements (hyponatremia, hypocalcemia, sepsis, hypoglycemia)
94
if seizure pt is hypoglycemic, what should you give
50 mL 50% glucose
95
drugs used to tx motor seizures
-fosphenytoin
-levetiracetam
-valproic acid
-propofol
-benzos
96
what is fosphenytoin
water soluble prodrug for IV or IM administration (better tolerated than phenytoin)
97
loading dose of fosphenytoin
15-20 phenytoin equivalents (PE) / kg infused at a rate of 150 mg/min
98
how to dose of phenytoin
15-20 mg/kg IV limited loading dose rate of 50 mg/min
99
SE of phenytoin
-hypotension
-asystole, widened QRS, prolonged QT, arrhythmias
100
how can phenytoin NOT be administered
IM
101
what can happen with extravasation or intraarterial injection of phenytoin
-"purple glove syndrome"
-skin necrosis
-compartment syndrome
-gangrene
102
dosing of levetiracetam
2000-3000 mg IV over 15 min
103
what is status epilepticus
continuous or intermittent seizures for more than 5 min w/o recovery or consciousness -after 5 min, less likely to spontaneously terminate -more likely to cause neuronal damage
104
first and second line tx for status epilepticus
first: benzos second: antiseizure drug
105
onset of benzos for status epilepticus
fast
106
DOA of benzos for status epilepticus
short lived
107
onset of diazepam to tx status epilepticus
2 min
108
DOA of diazepam for status epilepticus
15-60 min
109
adult dose of diazepam for status epilepticus
5-10 mg or 0.15-0.25 mg/kg (no faster than 5 mg/min)
-repeat in 5 min if seizure persists
110
onset of lorazepam for status epilepticus
3 min (slightly slower than diazepam)
111
DOA of lorazepam for status epilepticus
12-24 hr (longer than diazepam)
112
adult dose of lorazepam for status epilepticus
2-4 mg or up to 0.1 mg/kg
113
adult dose of midazolam for status epilepticus
0.1-0.2 mg/kg up to 4 mg q5min until seizure controlled
114
sedation drugs to avoid epileptiform activity
-thiopental
-opioids
-benzos
115
maintenance drugs to avoid epileptiform activity
-iso
-des
-sevo
-prop
116
agents to avoid during electrocorticography
-benzos
-volatile agents
-barbiturates
-prop
117
agents that are okay to use during electrocorticography
-opioids
-nitrous oxide
-droperidol
-diphenhydramine
-precedex
118
agents that enhance electrocorticography
-high dose short acting opioids
-methohexital
-etomidate
119
drugs that may be epileptogenic
-ketamine, enflurane, etomidate, opioids
-methohexital
- metabolites (meperidine, atracurium)
-sevo (dose concentration related)
