Anesthesia LO's Flashcards
(71 cards)
1
Q
Std ASA Monitors (5)
A
1- pulse ox 2- capnography 3- BP cuff q 5 min or invasive monitor 4- body temp measurement (esophageal or rectal) 5- visual EKG display
2
Q
In what situations is pulse ox inaccurate or misleading? (7)
A
- low blood flow conditions
- pt movement
- nail polish
- ambient light
- dysfunctional HgB (carboxy absorbs red not infrared so variable SpO2) and methemoglobin (absorbs them equally so SpO2 of 85%)
- IV dyes (methylene blue has SpO2 of 65%)
- altered relationship b/n PaO2 and SaO2 (any shift in dissociation curve)
3
Q
Capnography (importance, ideal meas, 4 parts of wave)
A
CO2 waveform represents CO2 in expired air - so shows that pt is ventilating (AKA pt is able to get rid of CO2)
on display is end tidal CO2 - want about 30-35 mmHg (this represents the alveolar CO2 - pACO2 which is close to but not exactly equal to PaCO2)
A-B - exhalation of anatomic dead space (no CO2)
B-C - exhalation of alveolar gas so inc CO2 in gas coming out (more gradual slope is bad sign - obstruction or lung disease)
D- end tidal CO2
D-E - inspiration begins (drop/descending in CO2)
Capnograph also tells you if the R ventricle / R heart is working - otherwise CO2 would not be getting to lungs to be expired
4
Q
What increases exhaled CO2? (8)
A
- hypoventilation
- exhausted CO2 absorber
- malfunctioning insp or exp valves
- malignant hyperthermia (give dantrolene)
- sepsis
- rebreathing
- admin of bicarb
- insufflation of CO2 from lap surgery
5
Q
Temp Monitoring in Anesthetized Pt (best locations)
A
Best core temp monitors - pulm artery, tympanic membranes, bladder
axillary / skin - prone to artifact
esophagus good for indicating trends of heat gain or loss
6
Q
What decreases exhaled CO2?
A
- hyperventilation
- hypothermia
- low CO
- dec or cessation of pulm blood flow (can be due to systemic hypotension or PE)
- accidental disconnection or tracheal extubation
- cardiac arrest
- esophageal intubation instead (may have CO2 from stomach in first breath then vanishes)
7
Q
Important Aspects of Pre-Op History
A
- Confirm planned surgical procedure and reason for undergoing surgery
- Acute and chronic medical problems
- Surgical history
- Anesthetic history– does the patient have a personal or family history of anesthetic complications, e.g. post-op nausea/vomiting (PONV), allergic reactions, difficult airway or malignant hyperthermia or pseudocholinesterase def?
- Allergies to medications
- Medication Reconciliation
- Prior substance use
- Pertinent labs, imaging and other diagnostic studies as indicated. (stress test, echocardiogram, PFTs, cardiac catheterization, etc.)
- functional capacity - avg level of exercise
8
Q
Important Aspects of Pre-Op Physical
A
- airway (Mallampati)
- tongue size
- teeth
- jaw opening
- cervical ROM
- thyromental distance
- neck thickness
- beard?
- listen to heart and lungs
- peripheral pulses
- edema?
9
Q
OSA Screen
A
STOP - BANG
S- snoring loudly
T - tired during day
O - observed apneic episodes
P - pressure (High BP)
B - BMI > 35
A - age > 50
N - neck circumference > 40 cm
G - gender (MALE)
High risk of OSA if > 3
10
Q
Which meds can be continued v. discontinued prior to surgery?
A
CONTINUE
- statins, HTN meds, diuretics (maybe not loops)
- 1/2 basal insulin
- metformin
- narcotics - esp for addiction
- psych meds including MAOIs (dep or anxiety)
- sz meds
- estrogen / birth control
- inhalers for asthma or COPD
DISCONTINUE
- short-acting insulin
- sulfonylureas
- herbs/supplements
- NSAIDs
- estrogen for HRT or osteoporosis
ASPIRIN
- cont if taken for stent or vascular disease (secondary prevention)
- discont if only for primary prevention, risk of bleeding > risk of thrombosis
11
Q
ASA Classification
A
ASA1 - healthy, non-smoker
ASA2 - mild systemic disease (no functional limitation)
ASA3 - severe disease (some functional limitation) ex - on dialysis, class II CHF
ASA4- severe disease at constant threat to life (functionally incapacitated) es - acute MI, resp failure w/ vent
ASA5- moribund - likely to die in 24 hrs +/- surgery
ASA6 - brain dead organ donor
**E on any above means emergency operation
12
Q
Indications for Intubation
A
- every pt receiving general anesthesia can be intubated but does not HAVE to be intubated
SPECIFIC …
- if need patent airway
- prevent aspiration (only form w/ “protected” airway)
- if need frequent suction
- for pos press vent of lungs
- if operative position other than supine
- operative site near upper airway
- if airway maintenance by mask is difficult
**Mandatory if recently consumed food or SBO undergoing operation
13
Q
Hypoxia (definition, differential, tx)
A
PaO2 < 60 or sat < 90%
- atelectasis (shunt)
- dec FRC –> V/Q mismatch
- dec CO
- alveolar hypoventilation (may be due to anesthetic)
- aspiration (airway closes reflexively, dec surfactant, cap leak)
- PE
- pneumothorax (shunt)
- advanced age
- obesity (hypovent)
- inc oxygen consumption (ex - shivering)
- post-hyperventilation hypoxia (compensate afterwards to replenish CO2 stores)
Tx -
Can do chest tube for pneumothorax
If relative shunt (some alveoli working) then give high inspired O2
If absolute shunt (no alveoli open - no gas exchange) then give PEEP and CPAP to re-inflate
14
Q
Hypercarbia (definition, differential and tx)
A
PaCO2 > 45 mmHg
Hypoventilation
- residual effect of anesthesia meds / inadequate CNS stim
- may be due to inadequate antagonists, potentiation by hypothermia, Mg or aminoglycosides, renal disease so dec excretion, delayed-phases effects of opioids
** Tx - naloxone, anti-cholinesterase, ventilate for them
Reduced ability to take deep breath
- obesity, positioning affecting muscles
- incision site pain
**Tx - incentive spirometry, chest PT, deep breathing exercises
COPD
15
Q
What med can be taken pre-operatively if hx severe post-op nausea?
A
Scopalamine patch 2-4 hrs before
16
Q
What meds can be taken pre-operatively to dec chance of aspiration?
A
H2 antagonists
PPIs
Metoclopramide
17
Q
What meds can be taken pre-operatively if sig hx allergic rxn?
A
Diphenhydramine and cimetidine - totally block histamine receptors
18
Q
What are the major differences b/n pediatric and adult airway?
A
In kids …
- larynx higher in neck
- tongue takes up greater proportion
- epiglottis is larger, stiffer, more posterior so use STRAIGHT blade (miller)
- larger head compared to body so need pillow or rolled towel under occiput
- shorter neck
- narrow nares
In adult narrowest part is vocal cords, in kids narrowest part is cricoid
19
Q
LMA (what is it? when to use it / when to not use it?)
A
LMA - supraglottic airway (seals in hypopharynx above upper esophageal sphincter)
Indications - difficult intubation, if pt is not undergoing neuromuscular block (so cannot intubate)
Contraindications - full stomach (b/c not protected - risk aspiration)
20
Q
Complications of Intubation
A
DURING
- dental injury
- HTN or tachy (reaction to blade)
- cardiac dysrhythmia or ischemia
- aspiration
- esophageal intubation
- cuff leak
- barotrauma
- tracheal tube obstruction
AFTER
- laryngospasm
- pharyngitis, laryngitis, tracheitis (sore throat)
- tracheal stenosis
- vocal cord paralysis
- arytenoid dislocation
- edema or ulceration
21
Q
How do you verify endotracheal tube placement?
A
- Visualize it going thru vocal cords
- capnography > 30
- symmetric bilateral chest rise
- bilateral breath sounds (more so right placement in BOTH lungs not 1)
- reservoir bag will have feel of normal lung compliance
- see condensation in mask
22
Q
Predictors of Difficult Mask Ventilation (5)
A
Age > 55 BMI > 26 beard lack of teeth hx snoring
23
Q
Predictors of Difficult Intubation (7)
A
Mouth opening - Inter-incisor distance < 3 cm
Uvula not visible (class III or IV)
short thick neck, neck circumference > 27 in
Inability to bring lower teeth in front of upper teeth
thyromental distance < 3 fingerbreadths
limited flexion or extension of neck
submandibular space w/ mass, stiffness or induration
24
Q
Basic Parts of Anesthesia Machine
A
Pop-off Valve
Flow meter (sep for ea gas)
Vaporizer (for ea volatile anesthetic)
Circle System (gas mix –> pt –> exhale –> CO2 absorber –> fresh gas to pt)
25
Pop-Off Adjustment
Open = no pressure - all gas wasted - pt can exhale freely
Closed = pressure / resistance to exhalation - most gas flows in circle
OPEN WHEN PT EYES OPEN (aka awake) and CLOSE WHEN PT EYES CLOSED
26
Colors of Flow Meters
Blue - N2O
Green - O2
Yellow - air
27
What are the two most common positioning injuries?
Ulnar Claw- elbow hyperflexion
Brachial plexus - b/n clavicle and rib
28
Absorption
Distribution
Context-sensitive half-time
Absorption - from site of admin to bloodstream (solubility, dose, bioavailability, site, first pass)
Distribution - from blood to body (areas of greatest perfusion first - brain, heart, kidneys, liver, glands)
Time required for 50% drug conc dep on duration of infusion (context) not just half-life (ex - fentanyl)
29
4 Goals of General Anesthesia (drugs used for ea)
1- unconsciousness (propofol or etomidate, volatile agents and N2O in kids)
2- analgesia (fentanyl, morphine, ketamine)
3- amnesia (benzo like midazolam)
4- muscle relaxation (sux or rocuronium)
**Volatile agents (sevoflurane) can do all but analegisa
**N2O can do all but muscle relaxation
30
Steps of Induction
1- monitors (EKG, pulse ox, BP)
2- pre-oxygenate (valve OPEN)
**may give midalozam and fentanyl here
3- IV sleep drug (propofol or etodmidate)
4- bag mask ventilate (valve CLOSED)
5- paralyze - muscle relax (do not want reflex against intubation)
**may give phenylephrine here for inc BP
6- intubate then check
31
Pre-oxygenation
Goal = replace nitrogen w/ 100% oxygen for safety margin b/n mask vent and intubation
8 vital capacity breaths of 100% oxygen over 1 min
OR 3 min tidal volume breaths of 100% oxygen
32
What is MAC?
min alveolar conc
min conc of inhaled anesthetic at 1 atm needed to prevent skeletal muscle movement in response to noxious stimuli in 50% people
Reflect partial pressure at site of action
33
How do inhaled anesthetics affect ventilation?
Inc RR but dec tidal volume so minute vent stable
This leads to inc PaCO2 (not as much CO2 expired) / less efficient gas exchange
Less ventilatory response to hypoxemia or hypercarbia
34
How do inhaled anesthetics affect cardio?
Small artery vasodilation --> less systemic vasc resistance
Inc HR
Prolong QT
35
4 Main Effects of Nitrous Oxide
1- expands air-filled cavities (blood-gas partition coef 34X nitrogen so leaves blood 34X faster) --> inc pressure in non-compliant areas and inc volume in compliant areas
2- cerebral vasodilation / inc cerebral flow
3- inc symp tone (diaphoresis, inc body temp, inc catecholamines in plasma, inc R atrial pressure)
4- inactivates methionine synthase to worsen B12 def
36
Factors that Inc MAC
- acute amphetamine use (cocaine or ephedrine)
- chronic alcohol use
- age
- hypernatremia, hyperthermia
- high cardiac output
37
Major Effects of Propofol
CNS - sedation, dec cerebral blood flow, dec ICP
Cardio - dec SVR, dec BP, small inc HR
Resp - dec RR, really dec tidal volume, dec ventilatory response to hypoxemia or hypercappnia, dec upper airway reflexes
38
Uses and Side Effects of Benzos
Uses - pre-op (dec anxiety, amnesia, sedation, synergistic w/ propofol or opioids), IV sedation, suppress sz, induction of anesthesia
Side Effects - dec cerebral flow, peripheral vasodilation - dec BP, minimal resp depression (may cause transient apnea if combined w/ other induction drugs)
39
Opioids MAO and Uses
MAO - bind opioid receptors --> act G protein --> inhibitory / hyper polarizing
Inhibit substance P release from primary sensory neurons in dorsal horn of SC which dec pain sensation to brain
Change affective response to brain in forebrain & change reward structures in brain
More effective for slow, unmyelinated C fibers than fast, A delta fibers
More effective if given b/f painful stimulus
Uses - pain relief, sleepiness, suppress cough
40
Opioid Side Effects (8)
- resp depression
- bradycardia, vasodilation
- nausea and vomiting
- pupil constriction (pinpoint)
- urinary retention
- constipation (delay emptying and sphincter spasm)
- muscle rigidity including vocal cord rigidity
- DEC MAC (synergistic w/ volatiles)
41
Amides v. Esters
Amides - not metabolized to PABA (metabolized in liver instead) --> so less likely to have allergies
**slow onset, longer duration, less maximum dose
Esthers - metabolized to PABA by local cholinesterases --> PABA cross reacts leading to greater chance allergies
**rapid onset, shorter duration, higher max dose
42
Mechanism and Complications of Local Anesthetic
MAO - stabilize nerve Na+ channels in inactivated state which blocks conduction of nerve impulses
Local complications - prolonger/ permanent anesthesia or muscle weakness
Systemic complications - (other Na+ voltage gated channels like in neurons, heart)
- agitation, tremor
- drowsy/unconscious
- sz
- vertigo
- tinnitus
- slurred speech
- angina
- SOB
- dysrhythmia
43
How do you prevent systemic affects of local anesthetic?
Co-administer w/ epinephrine to vasoconstrict
** cannot give if unstable angina, dysrhythmia, HTN, placental insufficiency, if nerve block w/o collateral flow
44
What is the max safe dose for lidocaine?
4.5 mg/kg w/o epi (do not exceed 300 mg)
7 mg/kg if w/ epi
45
Depolarizing v Non-depolarizing Neuromuscular Block (MAO, onset, metabolism)
Depolarizing
- mimics Ach to depolarize at NMJ (fasiculations)
- rapid onset (30-60 sec) and short duration (5-10 min)
- slowly hydrolyzed by AchE
- rapidly hydrolyzed by plasma pseudo-cholinesterase
Non-depolarizing
- comp antagonist of Ach at nicotinic receptors; no depolarization (NO fasiculations)
- onset 1-2 min for roc and 3-5 min for vecuronium/pancuronium
- duration is 20-35 min for rocuronium/vec and 60-90 min for pancuronium
46
What drugs dec effect rocuronium?
- calcium
- corticosteroids
- phenytoin
- burn injury
47
Adverse Effects of Sux (8)
- cardiac dysrhythmia, bradycardia
- fasiculations
- hyperkalemia (released from muscle cells during fasiculations)
- myalgias (can prevent w/ pretreating w/ roc)
- myoglobinuria
- inc intraocular pressure
- inc intragastric pressure
- trismus in kids esp
48
Adverse Effects of Non-depolarizers
Mainly dysrhythmia, inc HR, inc SVR
49
Contraindications to Sux (6)
24 hrs after major burns, trauma, SC injury or denervation (worry about hyperkalemia)
worry about hyperkalemia in boys if undiagnosed Duchenes Muscular Dystrophy
ICU pts or pts immoble for long periods - inc extra-junctional receptors --> inc K+ release
Narrow angle glaucoma (inc pressure)
malignant hyperthermia hx
plasma pseudocholinesterase def
50
How do you reverse a non-depolarizing block? What happens if reversal is incomplete?
Anticholinesterase inhibitor like neostigmine - dec metabolism of Ach so more Ach to outcompete rocuronium
QUARTERNARY - no CNS (just peripheral)
Side effects - muscarinic (brady, hypotension, inc GI motility, urination, sweating, laryngospasm, bronchospasm)
Can give w/ glycopyrrolate or atropine to dec muscarinic effects
If incomplete ... AIRWAY AT RISK (pharyngeal muscles too weak to prevent aspiration and cough)
51
Train of 4's Testing
4 consecutive 2 Hz stim < 10 sec apart
For non-depolarizing ... there is a fade response so meas TOF ratio (height last twitch / height of first twitch)
For depolarizing ... there is a uniform response; all twitches same magnitude so meas TOF count (# twitches)
If depolarizing drug if used and it becomes a fade then you know you are in phase II
More drug = less twitches
if 0 twitches DO NOT UNBLOCK/ REVERSE because you do not know where you are in blockade sequence)
52
TOF # and Suppression Correlations
0/4 - excessive blockade; difficult to predict; DO NOT REVERSE
1/4 - 90% suppression
2/4 - 80% suppression
3/4 - 75% suppression
4/4 - can then do tetanus test ... repetitive stim for 5 sec ... if full tetanus then no block ... if tetanus fades then there is residual block
53
What nerves are used for TOF monitoring?
Ulnar - adductor pollicus
- similiar to larynx muscles if sux
- more intense blockade than larynx muscles if roc
Facial - orbicularis oculi
-more similar to larynx muscles than ulnar
54
Phase I and Phase II of Depolarizing Blocks
Phase I - depolarization; sux binds Ach receptors to depolarize motor end plate; Ach cannot bind b/c receptors are OCCUPIED
Phase II - desensitization; post-synaptic membrane repolarizes but it de-sensitized so still does not respond to Ach
55
Crystalloids v. Colloid v. Blood
Crystalloid - doesn't stay intravascular; electrolyte content causes 2/3 to become interstitial
Ex) normal saline (.9% NaCl hypertonic), LR (hypotonic), D5W (glucose metabolized)
Colloid - does not easily cross endothelial barrier so stays endovascular; no electrolytes
Ex) albumin, dextran, hydroxyethyl starch
Blood - rarely used as first resort b/c in high demand and risk transfusion reaction; inc oxygen carrying capacity
56
Blood Transfusion Complications (8)
- Hep C or HIV
- tranfusion reactions (febrile, allergic, hemolytic)
- ARDS w/in 4 hrs
- suppression of cell-mediated immunity
- citrate overload can lead to metabolic alkalosis
- platelet and leukocyte microaggregation during storage - use 170 micron filter
- hypothermia leading to inc oxygen demand if blood temp is too low
- dilution thrombocytopenia
- DIC
57
Indications for Platelet Transfusion
Platelets < 50,000
1 unit --> inc 5000-10,000 in first hr
58
Indications for FFP Transfusion ( + what is it?)
**Contains all coagulation factors but no platelets
- If PT/PTT 1.5X longer than normal
- reversal of warfarin
- correction of coag factor deficit
59
Tissue Layers for Spinal v. Epidural
Spinal - skin --> superficial fascia --> supraspinous ligament --> interspinous ligament --> ligamentum flavum --> epidural space (POTENTIAL SPACE W/ VENOUS PLEXUS) --> dura mater (hear POP) --> arachnoid --> now in subarachnoid space (CSF)
**Get CSF back in
Epidural - stop b/f popping thru dura (use Tuohy needle that cannot easily pop and shorter catheter)
**Do not get CSF back
60
What is in the epidural space?
fat, lymphatics, blood vessels
61
Spinal v. Epidural (adv and disadv)
Spinal - easier to do and more comfortable for pt, more intense drugs so less amount of drug
Epidural - less headache, less hypotension, can leave catheter in post-op to inc drug
62
Contraindications and Complications from Neuroaxial Blocks
Contraindications
- infection at planned site of needle puncture
- inc ICP
- bleeding diathesis (AKA prone to bleed - hypo coag)
Relative Contraindications
- general systemic infection - risk abscess or meningitis
- pre-existing neuro disease
- Mitral or aortic stenosis / cannot withstand dec SVR
- abnormal coagulation
Complications
- neuro
- hypotension from symp NS block (give ephedrine)
- bradycardia / asystole (give atropine)
- headache (COMMON) - loss of CSF in spinal --> downward brain displacement --> stretch on supporting structures @ 12-48 hrs
- apnea (dec breathing motor) - O2 and CPAP
- nausea
- urinary retention
- back ache / root irritation
Specific Complications for Epidural
- hematoma or abscess
- dural puncture
- systemic absorption into vessels
- nerve injury
63
Locations for Brachial Plexus Blocks
Interscalene - (C3 to C7) for shoulder / proximal arm surgery
Supraclavicular - (at level of upper, middle, lower trunks) rapid onset and dense block for surgery of distal 2/3 arm
Infraclavicular - (at cords - lateral, medial, posterior) also for surgeries of distal 2/3 of arm and good for catheter stability if needed
Axillary - (at level of individual nerves - radial, median, ulnar, musculocutaneous) - may require mult injections
**May need to separately block intercostobrachial nerve for tourniquet placement - not part of plexus
64
Location for Lower Extremity Blocks
Lumbar plexus - usually in addition to GA for pain control; in psoas compartment
Femoral - anterior thigh and knee
Fascia Iliaca - lateral femoral cutaneous block; sensory to lateral thigh
Obturator - medial distal thigh
Saphenous nerve and adductor canal - saphenous is terminal sensory nerve of femoral; for superficial/medial lower leg and ankle
Sciatic - complete anesthesia of leg below knee; can use anterior or posterior approach
Popliteal - can block sciatic from this pt on
Ankle block - must inject to block 5 separate nerves (superficial and deep peroneal, tibial, sural, saphenous nerve) for surgery on foot and toes
65
Differential for Hypotension (11)
- Hypovolemia (inadequate replacement post-op)
- Hypovolemia secondary to internal bleeding - dec Hct
- Hypovolemia secondary to inc cap permeability (sepsis, burns, transfusion -related lung injury)
- Cardiogenic - dec contractility due to residual anesthetic, acute MI, pulmonary edema (give inotropes)
- Dec SVR - residual anesthesia or sepsis
- adrenal insufficiency
- cardiac dysrhythmia
- PE
- arterial hypoxemia
- pneumothorax
- tamponade
66
Signs on Bronchospasm
- wheezing
- inc peak inspiratory pressure / dec tidal volume
- slower upslope of capnogram
- if severe ... no breath sounds and difficult to ventilate
67
Algorithm for Pre-Op Cardiac Eval for Non-Cardiac Surgery
1- is it an emergency? is yes - optimize and operate
2-do they have symptomatic valve disease, arrhythmia, recent MI, decomp CHF or unstable angina? do not operate at this time
3- if not ... do they have > 4 mets? (flight of steps); if yes --> OR w/o further tests
4 - if not... assess cardiac risk
- ischemic heart disease
- heart fail
- CVA/TIA hx
- Creat > 2 mg/dL
- insulin dep DM
- vascular above inguinal lig, thoracic or intra-peritoneal surgery
if 0-1 factors ... low risk (< 1%) --> OR
if 2+ factors ... elevated risk --> do echo, CXR, EKG
68
Risk Factors for Post-op N and V (9)
- prior hx
- hx motion sickness
- female
- non smoker
- use of intra or post operative opioids
- volatiles and nitrous oxide
- large dose of neostigmine
- surgery duration
- surgery type (gyn, eye muscles, middle ear, chole, laparoscopic)
69
Tx options for post -op nausea and vomiting
Ondansetron - serotonin receptor antagonist
Perphenazine - works at hypothalamus
Droperidol (careful QT prolongation)
Metclopromide - inc motility
Scopolamine
Propofal at 1/10 induction dose
Dexamethasone
Aprepitant - NK1 antagonist
70
Complications from Post- Op Pain
"PaGE the ICU"
P- pulm (atelectasis and eventually, pneumonia)
G- GI (ileus)
E - endocrine (inc catecholamine release - hyperglycemia, sodium and water retention, protein catabolism)
I- immune function dec
C- cardio /coag ( hypertension, tachycardia, MI, dysrhythmia, DVT)
U- urinary retention
71
Parts of Anesthetic Plan
1- Will sedative-hypnotic premedication be useful?
2 - Prophylaxis against PONV (Post-operative nausea and vomiting)
3- What type(s) of anesthesia will be employed?
- General
- Regional
- Sedation/MAC
4- Are there special intraoperative management issues?
- Non-standard monitors
- Positions other than supine
- Relative or absolute contraindications to specific drugs
- Fluid management
- Potential need for blood transfusion
5 -How will the patient be managed postoperatively?
- Management of acute pain
- Need for mechanical ventilation or hemodynamic monitoring
