Anesthesia LO's Flashcards
Std ASA Monitors (5)
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
In what situations is pulse ox inaccurate or misleading? (7)
- 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)
Capnography (importance, ideal meas, 4 parts of wave)
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
What increases exhaled CO2? (8)
- hypoventilation
- exhausted CO2 absorber
- malfunctioning insp or exp valves
- malignant hyperthermia (give dantrolene)
- sepsis
- rebreathing
- admin of bicarb
- insufflation of CO2 from lap surgery
Temp Monitoring in Anesthetized Pt (best locations)
Best core temp monitors - pulm artery, tympanic membranes, bladder
axillary / skin - prone to artifact
esophagus good for indicating trends of heat gain or loss
What decreases exhaled CO2?
- 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)
Important Aspects of Pre-Op History
- 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
Important Aspects of Pre-Op Physical
- airway (Mallampati)
- tongue size
- teeth
- jaw opening
- cervical ROM
- thyromental distance
- neck thickness
- beard?
- listen to heart and lungs
- peripheral pulses
- edema?
OSA Screen
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
Which meds can be continued v. discontinued prior to surgery?
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
ASA Classification
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
Indications for Intubation
- 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
Hypoxia (definition, differential, tx)
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
Hypercarbia (definition, differential and tx)
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
What med can be taken pre-operatively if hx severe post-op nausea?
Scopalamine patch 2-4 hrs before
What meds can be taken pre-operatively to dec chance of aspiration?
H2 antagonists
PPIs
Metoclopramide
What meds can be taken pre-operatively if sig hx allergic rxn?
Diphenhydramine and cimetidine - totally block histamine receptors
What are the major differences b/n pediatric and adult airway?
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
LMA (what is it? when to use it / when to not use it?)
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)
Complications of Intubation
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
How do you verify endotracheal tube placement?
- 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
Predictors of Difficult Mask Ventilation (5)
Age > 55 BMI > 26 beard lack of teeth hx snoring
Predictors of Difficult Intubation (7)
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
Basic Parts of Anesthesia Machine
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)
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
Colors of Flow Meters
Blue - N2O
Green - O2
Yellow - air
What are the two most common positioning injuries?
Ulnar Claw- elbow hyperflexion
Brachial plexus - b/n clavicle and rib
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)