Flashcards in Week 2 Pre-op Assessment And Airway Mgmt Deck (46):
What is anesthesia?
Reversible, drug, induced depression of the central nervous system resulting in loss of response and perception of all external stimuli
What types of anesthesia are there?
*multiple different methods to accomplish similar goals
What are the components of the anesthetic state
*regional anesthesia breaks this definition slightly, but most components still apply
What are the common inhaled anesthetics?
How is inhaled anesthesia measured?
MAC: MInimun Alveolar Concentration
-stands for alveolar parietal pressures of a gas in 50% of humans do not respond to surgical stimulus
-dosing for inhaled anesthesia
-typically want at least 1 full MAC prior to incision
-measured at end-tidal concentration
What affects MAC values?
-will change depending on the pt
-infants will have the highest MAC requirement (even more than neonates)
-as people get older, MAC values decreases
-hair color is a factor (females with red hair have a higher MAC value)
what part of the nervous system do inhaled anesthestics work?
-reticular activating system
-GABA receptors subtype - A
What is the Meyer-Everton Rule?
-because inhalation agents act through the lipid-rich CNS cells, anesthetic potency increases with lipid solubility
Higher lipid content for inhaled anesthetic = higher potency
What are the MAC values of main inhaled anesthetics
Isoflurane: 1.2% is about 1 MAC
Sevoflurane: 2.0% is about 1 MAC
Desflurane: 6.6% is about 1 MAC
Nitrous: can’t get to 104%, can’t actually get to a full MAC
What is the purpose of the pre-op evaluation?
-Standard 1 from AANA
-CRNA is obligated to complete evaluation
-you are looking for pt factors that could alter your anesthetic plan and management
What is the purpose of the PAC clinic?
-Preanesthetic Assessment Clinic
-obtain medical history and physical exam
-promote patient teaching
-organize and coordinate meeting with other physician appointments relevant to surgery
-complete any other pre-op diagnostics
What are some key items to be looked at during chart review pre-op?
-anesthesia history (pt and family)
-stress test, echos
What is acceptable H & H in healthy pt without systemic disease?
-evaluate and treat each pt individually for the etiology and duration of their anemia
When are some examples that a coagulation screen is indicated?
-pt on anticoagulation, signs of bleeding, **esp with doing a spinal or epidural***
What are key points in patient interview?
-Name, bday, procedure, allergies, airway, NPO time
-quick head to toe run through of medical problems
-establish CRNA-patient relationship
What is the purpose of the pre-op assessment?
-establish trusting relationship
-modify parts of your plan to account for the pt risks associated with their co-morbidities
When does an airway assessment need to be done?
It needs to be done on every patient, for every procedure, regardless of the anesthetic plan
Why do we assess the airway?
-want to identify patients we may have trouble securing the airway ahead of time
What are you looking for during an upper airway assessment?
-size of mouth opening/able to under bite
-condition of teeth and surrounding tissue
-size of mandible and neck
What is Cormack view?
Grading system commonly used to describe laryngeal view during direct laryngoscopy.
-most glottic opening can be see with grade 1
What are oral indicators that a pt may be a difficult airway?
-length of upper incisors: 2 front teeth long with be more difficult
-relation of maxillary and mandibular incisors during normal jaw closure: over bite/underbite
-relation of maxillary and mandibular incisors during voluntary protrusion of mandible: can’t do, limited mobility
-interincisor distance: less than 4cm or 2 finger widths will be more difficult
-visibility of uvula: difficult if not visible while pt sitting
-shape of palate: high, narrow=less room. Want to see flat and open
-compliance of mandibular space
What are neck indicators that a pt may be a difficult airway?
-thyromental distance: less than 3 fingerbreadths = difficult
-length/thickness of neck: short and thick will be difficult
-ROM of head and neck: pt cannot touch tip of chin to chest or unable to extend neck
What is Three Axis Theory/2 Curve Theory?
*need to look up
What is the ASA definition of “difficult to ventilate”?
When signs of inadequate ventilation can not be reversed by mask ventilation or the patient oxygen saturation can not be maintained about 90% with mask ventilation.
What is the ASA definition of “difficult to intubate”?
A trained anesthesia provider, using conventional largyoscopy, requires more than 3 attempts or more than 10 minutes to complete tracheal intubation.
What percentage of difficult intubation are picked up even with proper evaluation?
What are some causes of unknown difficult intubation?
-pre-op assessment inadequate
-not as skilled anesthetist
What is the “Lemon Law”?
-Evaluate the 3-3-2 rule
-measurement of Atlanta-occipital angle
What this the 3-3-2 rule?
3: minimum distance the mouth should open
3: distance from the tip of mandible to the laryngeal cartilage
2: distance from the floor of the mouth to the prominence of the laryngeal cartilage
*all distances are measured in fingers
What is the thyro-mental distance?
-measure from upper edge of throid cartilage to chin with the head fully extended
-a short thyromental distance = an anterior larynx
- >7cm is usually = easy intubation
- <6cm = difficult airway
What are signs a mask ventilation is going to be difficult?
What are signs laryngeal visualization is going to be difficult?
Defined by 4 D’s
-Disproportion (of facial structure)
What are the 3 possible options for intubation?
-quick look: bolus of propofol and look
-induction and paralysis
When would an awake intubation be indicated?
If there is significant risk of complication if sedatives and/or muscle relaxants are administered prior to airway control
What are the 2 common techniques of pre-oxygenation?
1. Tidal Volume Breathing (TVB): 100% FiO2 3-5 minutes
2. Deep Breaths (DB): 4 times within 0.5 minutes. (4 vital capacity breaths at 100%FiO2)
Why do we pre-oxygenate?
-removes nitrogen stores in blood and replaces with oxygen. Body can only use O2 attached to hemoglobin. Bc O2 dissolved in blood, hemoglobin can pick up more O2 even though apnic. Pre-oxygenation extends our ability for apnic times
When does intubation become an emergency situation?
When you are unable to ventilate or ventilation not adequate
What are some tools to assist with difficult intubation?
-fiber optic intubation
-blind oral/nasal intubation
-invasive airway access
What are subglottic interventions and emergency invasive airway access examples?
-needle cricothyrotomy with transtracheal jet ventilation
What are some challenges with the unexpected difficult airway?
-experienced help may not be immediately available
-special equipment may not be immediately available
-a general anesthetic has usually been administered
-a long acting relaxant may have been given
-backup airway management plans may be poorly thought out
What is the purpose of the difficult airway cart?
For unknown/unplanned difficult airway. Have everything you would need (ie: bronchoscope,different tubes, stylets....)
What are requirements for tracheal extubation?
-acceptable hemodynamic status
-ability to maintain a patent airway
-adequate muscle strength
-adequate respiratory muscles
-ability to maintain adequate oxygenation
What is STOP-BANG?
Neck circumference >40cm
High risk >3
What is ASA class?
*classification system for assessing the fitness of a pt before surgery
-class I: healthy pt
-class II: mild to moderate systemic disturbance
-class III: severe systemic disease that limits activity
-Class IV: severe disease that is constantly life threatening
-class V: moribund pt, undergoing surgery as a resuscitate effort despite minimal chance of survival
-class VI: declared brain dead pt whose organs are being recovered
-emergency operation (E): emergency surgery required
What is the CRNA role in informed consent?
● The CRNA shall obtain or verify that an informed
consent has been obtained by a qualified provider