Oral Review Flashcards
Components of the upper airway:
Nasal passages Oral cavity: teeth, tongue, soft and hard palate Pharynx Tonsils Uvula Epiglottis Vocal cords
Components of the lower airway:
Trachea Carina Bronchi Bronchioles Terminal bronchioles Respiratory bronchioles Alveoli
Boundaries of the pharynx:
Nose to cricoid cartilage
Naso/oropharynx divided by soft palate
Oro/laryngopharynx divided by epiglottis
Innervation of the airway:
Sensory:
Glossopharyngeal: posterior 1/3rd tongue, oropharynx to vallecula
Internal branch of SLN: vallecula to vocal cords
Recurrent LN: subglottic mucosa
Motor:
Recurrent LN: posterior cricoarytenoid, arytenoid, lateral cricoarytenoid, vocalis, thyroarytenoid
External branch of SLN: cricothyroid
Muscles that close and open glottis:
Posterior cricoarytenoid (abducts; Pulls Cords Apart)
Arytenoid
Lateral cricoarytenoid
Muscles that put tension on vocal cords:
Cricothyroid
Vocalis
Thyroarytenoid
S/s of esophageal intubation:
No breath sounds
No ETCO2
Low SpO2
S/s of endobronchial intubation:
High peak airway pressures
Uneven chest rise
No breath sounds on left
Low SpO2
Describe the cricoid cartilage:
Only complete ring of of cartilage in the trachea
Signet-shaped
Narrowest part of peds airway
Located inferior to the thyroid cartilage and cricothyroid membrane
Sellick’s Maneuver:
Used for rapid sequence intubation to prevent aspiration of gastric contents
Have an assistant hold pressure on the cricoid cartilage as you induce patient and hold firm until ET tube placement is confirmed
Advantages of an LMA:
Less anesthesia requirements for airway tolerance
Improved hemodynamic stability for induction/emergence
Easier and faster to insert
Can be woken up with LMA in place
Disadvantages of an LMA:
Does not protect against aspiration
Lower seal pressure
Cannot mechanically ventilate
Increased risk for gastric insufflation
Contraindications for an LMA:
Full stomach: bowel obstruction, GERD, gastroparesis Non-fasting Pregnant Trauma Acute abdomen Thoracic injury Autonomic neuropathy Low pulmonary compliance
Extubation criteria:
TV > 6ml/kg
VC > 10 ml/kg
RR 90%
Sustained head lift for 5+ seconds
When is an ETT necessary?
Pregnant Aspiration risk Long case Can't access airway during case Head/chest/neck/abd surgery Need for controlled ventilation Airway compromise or disease
What are airway adjuncts for difficult airways?
LMA Lightwand Transtracheal jet ventilator Glidescope Bullard Bougie
What are potential hazards of airway management?
Damage to teeth, lips or soft tissue Laryngospasm Bronchospasm Aspiration/vomiting Endobronchial or esophageal intubation SNS stimulation Hypercarbia/hypoxemia
What triggers laryngospasm?
Foreign objects (vomit, blood, secretions) in the airway
Pain
Pelvic/abdominal visceral stimulation
Loud noises
What muscles cause laryngospasm?
Lateral cricoarytenoids
Thyroarytenoids
Cricothyroid
How do we treat laryngospasm?
Jaw lift
100% FiO2 and positive pressure ventilation
Suction/remove stimulation
Succs 20-40mg
Pre-op airway assessment should include:
Overall appearance of head/neck Mallampati score Range of motion Thyromental distance Dentition Mouth opening H/o difficult airway Planned surgery
When should nasal intubation be avoided?
Epistaxis/anticoagulated
Nasal/basal skull fx
Adenoid hypertrophy
Large turbinates
What are potential hazards of an oral airway?
Bleeding
Tissue damage
Laryngospasm
Causes of obstructed airway:
Tongue Laryngospasm Bronchospasm Mucous plug in ETT Kink in ETT
S/s of obstructed airway:
Low O2 sat
No ETCO2
No chest rise
High pitched, snoring, or no noise
Indications of a good mask case:
Easy airway Good mask seal (no heavy beard) Easy to ventilate No aspiration risk Short case, non-head/neck No repositioning (will have access to airway entire case) No airway bleeding/secretions
Steps if awake intubation is unsuccessful:
Cancel case, consider feasability of other options, or surgical airway
If unable to intubate but have adequate mask ventilation, next steps in difficult airway algorithm are:
- Call for help, consider return to spontaneous breathing, or waking patient up
- Try non-emergency adjuncts: LMA, glidescope, mask case, FO intubation, retrograde, etc
- If still unable to intubate, consider surgical airway, mask case, or local/regional
If unable to intubate or mask ventilate, next steps in difficult airway algorithm are:
- Attempt an emergency non-surgical airway: LMA, combitube, bronchoscope, transtracheal jet ventilation
- Emergency invasive airway: cricothyrotomy, tracheostomy, ETT passed through LMA if able to ventilate
NPO guidelines:
2 hrs: clear liquids
4 hrs: breast milk
6 hrs: light meal/milk/formula
8 hrs: heavy meal
Steps to resolve difficult mask ventilation:
Reposition airway
Oral/nasal airway
Call for help so you can two-hand the mask
Standard ASA monitoring:
Qualified anesthesia personnel
Oxygenation (FiO2, O2 analyzer, pulse ox)
Ventilation (auscultation, observation, ETCO2)
Circulation (ECG, HR, BP, pulse ox, a-line, pulse)
Temperature
Two major goals of anesthesia maintenance:
Maintenance of hemodynamic stability
Prevention of recall
Emergence procedure:
Reverse when 1+ twitch has returned Turn off gas, turn up O2 (100%) Switch to manual ventilation, open APL - check for spontaneous breathing Suction Check to see if pt is following commands Suction again Deflate cuff, extubate with a PPV breath
Purpose of BIS monitoring:
Guides administration of anesthetic to prevent recall
Describe EEG waves awake and under anesthesia:
Awake: low amplitude, high frequency
Anesthetized: high amplitude, low frequency
Benefits of using BIS:
Less risk of awareness
Faster wake-up/recovery
More cost-effective use of drugs
Better clinical decision making and management of response to surgical stimuli
What can cause oscillations/alterations in the BIS waveform?
Ischemia
Severe hypoxia
Hypothermia
Artifacts
BIS values and anesthesia correlations:
100: awake/resting
100-70: conscious sedation, emergence, response to surgical stimuli
70: light hypnosis; decreased chance of recall
60: moderate hypnosis; GA maintenance
40: deep hypnosis; high dose opioids, barb coma, profound hypothermia
0: isoelectric EEG
Therapeutic range for BIS:
60-80 for light hypnosis, 56-60 for moderate hypnosis/GA
Why do we use PNS?
Wide variability in dose requirements Facilitates timing of intubation Allows titration to effect Assesses readiness for reversal Differentiates type of block Facilitates early detection of pseudocholinesterase deficiency
Most common nerve/muscles used for twitch monitoring:
Ulnar + adductor pollicis
Facial + orbicularis oculi
Posterior tibial on top of foot
Order of muscle resistance to NMB:
Vocal cords Diaphragm Orbicularis oculi Abdominis rectus Adductor policis Masster Pharyngeal Extraocular
Which muscle best reflects diaphragm paralysis?
Orbicularis oculi
Advantages/disadvantages to monitoring adductor pollicis:
Disadv: diaphragm may still be moving at 0/1 twitch
Adv: If 4 twitches in AP, diaphragm has no residual blockade
Describe single twitch:
Single stimulus at 0.1 or 1 Hz. Used to determine baseline strength of response.
Describe TOF:
Four twitches, 2 Hz, no more than every 12 seconds.
Used to determine level of blockade in NDMR by looking at ratio of 1st twitch to 4th.
With DMR, will see even decrease in amplitude across all 4 twitches.
Describe tetanic stimulation:
50-200Hz delivery for 5 seconds
Not blocked or DMR: sustained contraction
NDMR: will note fade in contraction
Antagonizes NMB in tested muscle so subsequent twitches will be greatly increased in amplitude
Describe post-tetanic count:
Single twitches at 1Hz, 3 seconds after tetany
1 = intense blockade
3 = moderately intense
More during surgical block
Describe double burst stimulation:
2 trains of 3 at 50Hz, separated by 750ms
Evaluate ratio of 1st to 2nd
Easier to determine ratio
TOF twitches, corresponding % blockade, and clinical implications:
0: 100% - intubation
1: 90% - surgical block
2: 80-90% - surgical block
3: 75-80% - needs reversal or redose
4:
TOF ratio and patient responses:
TOF 0.4: can lift head/arm
TOF 0.6: lift head 3 sec, open eyes, stick out tongue
TOF 0.75: cough, lift head 5 sec, weak grip
TOF 0.8: normal inspiratory force/capacity
Distribution of body fluid:
Total body water = 60% of body weight
Intracellular = 40% of body weight (2/3rd of water)
Extracellular = 20% of body weight (1/3rd of water)
Plasma = 4% of body weight (20% of ECF)
Interstitial = 16% of body weight (80% of ECF)
How to assess volume status:
Skin turgor Mucus membranes Lung sounds Sunken eyes VS: tachycardia, hypotension Urine output Hct (elevated in dehydration) BUN/Creatinine
Components of intraoperative fluid requirements:
Maintenance fluid
NPO deficit replacement
Blood loss
Evaporative/3rd space loss
What do maintenance fluids compensate for?
Insensible loss from respiratory tract, GI fluids, skin/perspiration, feces/urine
How do we determine maintenance fluid requirements?
4ml/kg first 10kg
2ml/kg 2nd 10kg
1ml/kg after first 20kg
How do we calculate fluid deficit and replace it?
Maintenance requirements * hours NPO
1/2 in first hour
1/4 in 2nd and 3rd hours
If extra deficit (bowel prep, etc) replace before induction
How to gauge blood loss from surgical gauze:
Soaked 4x4 is 10ml
Soaked lap tape is 100-150ml
EBV in various age groups:
Adult male 75 ml/kg Adult female 65 ml/kg Child 70 ml/kg Infant 80 ml/kg Neonate 85 ml/kg Preemie 90 ml/kg
Calculation for ABL:
ABL = (EBV * % drop in Hct allowed) / Hct
Evaporative/third space losses by type of surgery:
Minimal - 0-2ml/kg/hr - eyes, lap chole, hernia
Moderate - 3-5ml/kg/hr - open chole, appy
Severe - 6-9ml/kg/hr - bowel sx, hip replacement
Emergency - 10-15ml/kg/hr - GSW, MVC, trauma, major burns
How is blood loss replaced?
3: 1 with crystalloids
1: 1 with colloids
Hypotonic IV fluids:
D5W: osmo 253, causes free water intox/hyponatremia
Isotonic IV fluids:
NS, LR: osmo 300, replaces water/electrolytes, stays in vascular space
Hypertonic IV fluids:
2NS: osmo 432
3% NS: osmo 1026
Draws fluid into the vessels from the interstitial space
Describe LR:
Isotonic, provides 100ml free water per liter
Most physiologic solution
Avoid in renal failure d/t K+
Do not give with blood (will clot)
Contains per liter: Na+ 130, K 4, Cl 110, Ca 2.7, Lactate 27
Describe NS:
Isotonic
Can cause hyperchloremic acidosis in large volumes
Good for diluting PRBCs
Describe albumin:
Obtained from fractionated human plasma
No coag factors or antibodies
5% (what we use) or 25%
Half-time of 3-6 hours
Describe hetastarch/hespan 6:
Non-antigenic, cheaper than albumin, equally effective
Excreted renally
Can cause coagulopathy with dilutional thrombocytopenia
Describe dextran:
70 for volume expansion, 40 for prevention of thrombosis
Synthetic water soluble colloid that degrades to glucose
Anaphylaxis, platelet inhibition at > 20ml/kg, noncardiac pulm edema, interferes with cross-matching
Benefits of crystalloid volume replacement:
Cheaper
Supports UOP better
Less likely to cause pulm edema
No coag/antigen problems
Benefits of colloid volume replacement:
Better at restoring severe volume deficits
Longer half-time
Better with low protein
Indications for transfusion:
Need to increase O2 carrying capacity
Need to expand vascular volume
Age, co-existing disease, CV status, Hgb/Hct, blood loss, etc.
Rarely need to transfuse > Hgb 10, almost always need to
Risks of blood transfusion:
Pulm edema ARDS Increased ICU stay Hemolytic reaction ABO reaction Bacterial sepsis (platelets) Infectious disease Hyperkalemia Hypocalcemia Citrate toxicity Dilutional thrombocytopenia/coagulopathy
Describe PRBCs:
Type-specific good enough for 98.9% of people
1 unit will inc Hgb 1g/L, Hct 3-5%
Has an Hct of 70%
Reconstitute with NS
Anticoagulated with citrate, which will bind calcium
Describe platelets:
1 unit is from 1 unit whole blood centrifuged
Not ABO typed
1 unit will inc platelet count by 7-10k
Can become bacterially contaminated
Describe FFP:
Contains all clotting factors, fibrinogen, and plasma proteins
Must be ABO compatible
Used to reverse warfarin, supplement coag factors, supplement for massive transfusion; not for fluid volume expansion
1 unit will inc clotting factor level by 2-3%
Describe cryo:
Precipitate remaining after FFP is thawed
Contains 8, 13, vWF, and fibrinogen
Must be ABO compatible
Treats hemophilia A, von Willebrand’s disease
