Principles of Anesthesia Practice I Unit II Flashcards
1
Q
How should joints be aligned?
A
In as natural a position as possible, pressure points should be padded
2
Q
What safety measures must be used in the abdominal/pelvic area?
A
Safety belts/straps, take care to avoid placing them too tightly
3
Q
What is the timeframe for nerve injury to occur?
A
Short, it does not take long for injury or irreversible damage to occur
can occur in as little as 30 minutes
4
Q
What is the most common surgical position?
A
Supine
5
Q
What are the pathophysiology considerations of the supine position?
A
Increased venous return, preload, SV and CO, decrease in Vt and FRC
6
Q
Describe the correct positioning of arm abduction
A
Out to the side less than 90 degrees, padded arm boards, arms should be supine (palms up) elbows padded and arm secured with a strap
7
Q
Describe the correct positioning of arm adduction
A
Tucked alongside the body, arms held alongside the body with a draw sheet, hands/forearm are supine (palms up) or neutral (palms towards body), elbows are padded, may tuck one arm if surgeon must stand on side of patient
8
Q
Complications of supine?
A
Backache, Pressure alopecia, Brachial plexus or axillary nerve injury if arms abducted > 90 degrees, Ulnar nerve injury if hand/arm is pronated (palm down), Stretch injury when neck is extended and head turned away (brachial plexus)
9
Q
What methods can you use to help prevent a patient in trendelenburg from sliding?
A
Use a non-sliding mattress/pad, use a mark on the sheet to measure movement, avoid bean bags
10
Q
Pathophysiology of trendelenburg?
A
Increase: CO (more venous return), ICP/IOP (edema of face, conjunctiva, larynx and tongue a concern) and intra-abdominal pressure
Decrease: FRC and pulmonary compliance and diaphragm shifts up
May need higher ventilation pressures and risk of endobronchial intubation as abdominal contents push the carina cephalad
11
Q
What methods can you use to help prevent a patient in reverse trendelenburg from sliding?
A
Use of non-sliding mattress/pad, use of a footrest
12
Q
Pathophysiology of reverse trendelenburg?
A
Hypotension risk (blood pools in the lower extremities), downward displacement of abdominal contents and diaphragm, decreased perfusion to the brain
13
Q
What steps must be taken to secure a patient in the sitting position?
A
Stabilize the head (head rest or pins), hips are flexed less than 90 degrees with knees slightly flexed, feet are supported to prevent sliding, compression stockings to maintain venous return, keep at least 2 fingers distance between chin and sternum
14
Q
Why is beach chair position used frequently in shoulder cases?
A
Less severe hip flexion and slight leg flexion
15
Q
Risks of the sitting position?
A
Cerebral hypo-perfusion and air embolism, Pneumocephalus, Quadriplegia and spinal cord infarction, Cerebral ischemia, Peripheral nerve injuries (big one is sciatic nerve injury)
16
Q
Pathophysiology considerations of sitting position?
A
Hypotension risk (venous pooling), decreased MAP/CI and cerebral perfusion pressure
17
Q
Describe what is entailed in supporting/placing a patient in the prone position
A
Arms are tucked or stretched less than 90 degrees with elbow flexion, head is supported face down with a pillow/headrest/rigid fixation with care taken to minimize pressure on eyes/nose/mouth/ears, avoid compression of breasts/abdomen/genitalia, legs padded and slightly flexed at the knees/hips, stockings to prevent venous pooling.
intubate supine then prone the patient, EKG leads go on the back
18
Q
What are the risks of prone positioning?
A
Facial and airway edema, nerve injuries, post-op visual loss d/t ischemia, ET tube dislodgement, loss of monitor and/or IV lines
19
Q
What causes ulnar nerve injury in prone positioning? Brachial plexus injury?
A
Ulnar = if elbows are not padded
Brachial = if arms are abducted greater than 90 degrees
20
Q
Prone pathophysiology considerations?
A
Edema of face, conjunctiva, larynx, and tongue, increased abdominal pressure (this reduces venous return from the inferior vena cava which reduces CO), improved ventilation (ventilation and perfusion shifts to the dependent areas of the lung)
21
Q
Describe lithotomy position
A
Patient is supine with legs up in padded or candy cane stirrups, arms tucked or on arm boards, if either trendelenburg is needed use a non-slide mattress, hips flexed 80 - 100 degrees and legs abducted 30-45 degrees from midline with knees flexed, lower extremities must be raised/lowered in synchrony (this prevents torsion to the lumbar spine), ensure fingers/hands are free of the foot of the bed when lowered, with longer surgeries try to periodically lower the legs
22
Q
Lithotomy pathophysiology considerations?
A
Increased venous return/CO and ICP, increased intraabdominal pressure (diaphragm moves up), decreased lung compliance and Vt
23
Q
Describe lateral decubitus position
A
Lies on the non-operative side (dependent) requiring anterior/posterior support with rolls/bean bags, adequate head support (ensure neutral position, check dependent ear regularly), dependent leg is slightly flexed, arms are in front and must be supported and abducted less than 90 degrees, axillary role placed between the chest wall and bed caudal to the axilla (prevention of brachial plexus injury) and pad between the knees
24
Q
What side of the patient is down in right lateral decubitus?
A
Right side is down (dependent)
25
In lateral decubitus, what must be done if the bed is flexed?
You must use a kidney rest, or place the point of the bed under the iliac crest (this prevents inferior vena cava compression and allows for lung expansion of the dependent lung)
*Watch carefully for ET tube dislodgement, caution the use of an LMA*
26
Lateral decubitus pathophysiology concerns?
Venous pooling, V/Q mismatch (inadequate ventilation to the dependent lung and decreased blood flow to the non-dependent lung, think back to his Schmidtness and those concepts)
27
What is the basic MOA of most nerve injuries?
A result of stretch, pressure or ischemia though the exact MOA is unclear
28
What is the basic timeframe for nerve injuries to occur?
In as little as 30 minutes
29
What type of nerve is most commonly injured?
Sensory, though it may be combined sensory and motor, it may also be temporary or permanent
30
T/F: nerve injuries can occur with optimal positioning
True
31
What changes can alter waters ability to auto-ionize?
Changes in relative concentrations of fluids and e-lytes
*this ensures optimal enzymatic function*
32
Who noted the loss of carbonate of soda in cholera patients?
O'Shaughnessy in 1831
33
What are the definitions of acidemia and alkalemia?
Acidemia = Excess production of H+ (in relation to hydroxyl ions)
Alkalemia = Excess production of OH- (in relation to hydrogen ions)
34
What exactly is measured on the pH scale?
The hydrogen ion concentration
35
What are the 3 primary substances the body manipulates to manage pH?
CO2 entering/leaving via the lungs
HCO3 enter/leaving via the kidneys (in the PT)
H+ being reabsorbed in the distal tubule and the collecting duct
36
Write out the henderson-Hasselbalch equation
pH = 6.1 + log (serum bicarb / 0.03 x PaCO2)
37
What is the definition of a substance that can either donate or receive a proton depending on the other substrate? What is an example of this in the body?
Amphoteric, and water is the classic example of this
In the presence of HCl (strong acid) it donate a proton to water (a base in this scenario)
In the presence of KOH (a strong base) it receives a proton from water (an acid in this scenario)
38
What is the relationship of pKa (or strength of the acid) to the degree of dissociation in water?
In general, strong acids have a lower pKa (lactic acid has a pKa of 3.4) completely dissociate compared to a weak acid like carbonic acid which has a pKa of 6.4 and only partially dissociates
39
What 3 rules govern the body and its behavior in regards to ions and pH management?
The body wants to remain electrically neutral, the dissociation equilibria and mass of conservation
40
What are the most abundant ECF strong ions? The others?
Most common = Na+ and Cl -
Others = K+, SO42-, Mg2+, Ca2+
41
Describe the strong ion difference equation
Total strong cations - strong anions
42
Is SID + or - in the ECF? How can it be used in clinical pH management?
In the ECF, SID is always positive (meaning there will be more cations than anions in the ECF). SID is an independent predictor of pH
*remember, a cell tends to be more negative, and will have more anions, this needs to be balanced out by a more + ECF*
43
For THIS class, if PaCO2 and HCO3 change in the same or opposite directions, what is the acid/base disorder?
Same direction = primary disorder with secondary compensation
Different direction = mixed acid/base disorder
44
Identify this acid/base disorder: pH 7.33, PCO2 48, HCO3 26
Respiratory acidosis, body is attempting to compensate
45
Identify this acid/base disorder: pH 7.58, PCO2 35, HCO3 29
Metabolic alkalosis
46
Identify this acid/base disorder: pH 7.28, PCO2 46, HCO3 18
Mixed acid/base disorder
47
Identify this acid/base disorder: pH 7.48, PCO2 32, HCO3 22
Respiratory alkalosis
48
For this class, what is a normal pH, PCO2 and HCO3 (not the range, the "middle of the road number")?
pH = 7.4
CO2 = 40
HCO3 = 24
49
What are some CV consequences of acidosis (include the pH level these changes occur if applicable)?
Impaired contractility (at a pH of 7.2), decreased arterial pressure, sensitive to re-entry dysrhythmias, decreased threshold for v-fib and decreased responsiveness to catecholamines (at a pH of 7.1)
*think back to ICU days, this is why you can throw boatloads of pressors at acidotic patients and their BP still sucks, their low pH doesn't allow the catecholamines to work because they denature in the acidic environment*
50
CNS consequences of acidosis?
Obtundation and coma
51
Pulmonary consequences of acidosis?
Hyperventilation, dyspnea and respiratory muscle fatigue
52
What is the definition of respiratory acidosis?
An acute decrease in alveolar ventilation results in increased PaCO2
*this definition usually requires that pH drop below 7.35 and is indicative of some measure of respiratory failure*
53
What are the 3 categories of respiratory acidosis?
Central ventilation control issues, peripheral ventilation control issues and VQ mismatch
54
What are some examples of central ventilation control issues?
Drug-induced ventilatory depression, permissive hypercapnia
*think drug related, like excess opioids or propofol*
55
What are some examples of peripheral ventilation control issues?
Neuromuscular blockade related to a high epidural/spinal, pneumo/hemothorax
56
What are some VQ mismatch causes?
Abdominal splinting, retained secretions, atelectasis
57
What are some obstructed breathing issues that can cause acute respiratory acidosis?
Obstruction of: supraglottic, glottic, subglottic airway. Bronchospasm can also cause it.
58
What is the difference in the rate of bicarb change in acute vs chronic hypercarbia?
Acute = a 10:1 ratio (for every increase in 10 of PaCO2, bicarb goes up by 1)
Chronic = a 10:3 ratio (for every increase in 10 of PaCO2, bicarb goes up by 3)
59
If your PaCO2 is 80 mmHg, what is the expected HCO3 level for acute vs chronic hypercarbia?
Acute = 28 mEq/L
Chronic = 36 mEq/L
60
Why is using bicarb to reverse chronic hypercarbia potentially dangerous?
The excess bicarb causes CNS irritability which increases seizure risk
61
What are some causes of metabolic acidosis?
Increased production of acid, decreased excretion of acid, acid ingestion or Renal/Gi bicarb losses
*It can also be associated with alterations in transcellular ion pumps, increase in iCal and a right shift of the OxyHgb curve*
62
What formula allows you to determine if your current level of bicarb is adequate for your current PaCO2?
1.5 x HCO3 +8
63
If your bicarb is 12, what level of CO2 can you adequately buffer?
1.5 x 12 + 8 = 26
64
If your bicarb level is 31, what level of CO2 can you adequately buffer?
1.5 x 31 + 8 = 54.5
65
What is the ratio of change in base excess to change in partial pressure of CO2 in acute metabolic acidosis?
1:1.2 change, for every decrease of 1 in the base excess, PaCO2 should drop by 1.2 mmHg
66
Bicarb loss being countered by the net gain of chloride ions is what kind of acidosis?
Hyperchloremic metabolic acidosis
67
Electrical neutrality is maintained by what 3 ions in the simple anion gap equation?
Na, bicarb and chloride
*alterations can occur from NaCl infusions, diarrhea and early renal failure*
68
What is the simple anion gap and conventional anion gap equations?
Simple: Na+ - (Cl- + HCO3-) = 12-14 mEq/L
Conventional: (Na+ + K+) - (Cl- + HCO3-) = 14-18 mEq/L
69
What are the normal ECF Na, K, Cl and HCO3 levels (these are important for anion gap equations)?
Na = 140, Cl = 105, Bicarb = 24, K = 4
70
What is the limitation of anion gap equations in estimating electrical neutrality/the level of acidosis?
They generally underestimate the disturbance because they don't take into account other electrically active compounds (albumin, phosphates) and if you have hypoalbuminemia or hypophosphatemia, then the disturbance is greater than what the anion gap equation predicts
71
What causes a high anion gap?
Excess acid in the ECF, can be caused by lactic acidosis, ketoacidosis, renal failure or poison
*remember, acids dissociate into H+, H+ then combines with bicarb to make carbonic acid which then dissociates into H2O and CO2, this process depletes your bicarb reserves*
72
What is the mnemonic for anion gap acidosis causes?
CATMUDPILES - I'm too lazy to type all this out, here's the picture
73
Lactic acidosis is generally a marker of critical illness, such as a mix of over production vs inadequate clearance or persistent acidosis. What process contributes to an excess lactic acid production?
Degradation products of glucose metabolism from substances like catecholamines, lactate to pyruvate and gluconeogenesis. This can also contribute to moving from aerobic to anaerobic metabolism further worsening the lactic acidosis
74
What SVO2, CVP and SV levels indicate type A vs type B lactic acidosis?
Type A: SVO2 less than 70%, CVP less than 5, SV less than 0.7 ml/kg
Type B: SVO2 greater than 70%, CVP greater than 5, SV greater than 0.7 ml/kg
*For type A, think fluid, early infection or cardiac failure. For type B, think poison, liver failure, late stage sepsis, arterial thrombosis or abdominal ischemia of some sort*
75
For type A lactic acidosis, what should you suspect if the Hgb is low?
Likely hemorrhagic shock
76
For type A lactic acidosis with a normal Hgb, what should you suspect if the CRP/WBCs are high? If CRP/WBCs are normal?
Normal = consider cardiogenic shock (start inotropes, IABP or pericardial drain)
High = likely sepsis, check for a UTI, or intra-abdominal source. Do they have a long-term catheter of some sort?
77
For type B lactic acidosis, what are some common causes of poisoning?
Metformin, sodium nitroprusside, cyanide and carbon monoxide
78
For type B lactic acidosis, what should be on your differential diagnosis list if all pulses are intact? If they are not?
Intact = Consider bowel or splanchnic ischemia (get some imaging, prep for ex-lap or bowel resection)
Not intact = consider arterial thrombosis, prep for angiography and revascularization
79
What lab values indicate lactic acidosis?
Lactate greater than 3 mEq/L and pH less than 7.35
*if this occurs, per the decision tree, check an SVO2, CVP and SV*
80
Treatment of ketoacidosis vs lactic acidosis?
KA = insulin and fluids
LA = depends on the cause, in general, improve tissue perfusion, fluid resuscitate and DC metformin. If renal failure is a component, dialyze
81
Why is treatment of acidosis with bicarb controversial?
Because giving bicarb (think back to Schmidt acid/base lectures) feeds into the carbonic anhydrase equilibrium reaction, increasing bicarb on one side shifts the equation to favor formation of CO2 which can worsen the acidosis in the long run
82
Why is bicarb administration dangerous in chronic metabolic acidosis?
Acute pH changes negates the right shift (decreased oxygen affinity), so Hgb holds onto oxygen more tightly, meaning less is dropped for acidotic tissue which is likely oxygen starved in acidosis = tissue hypoxia
83
What is the formula to determine how much bicarb to give?
0.3 x base deficit (mmol/L) x weight in Kg and divide this by 2
*the other way to think of this, 0.3 x base deficit (mmol/L) x weight in Kg, once that dose is determined, cut it in half. Both ways get you the same thing, just a mildly different way to approach it*
84
Anesthesia management of lactic acidosis?
Likely postpone surgery, if it is urgent/emergent, get as much hemodynamic monitoring in place as you can, give fluids, monitor cardiac function and get an iStat to frequently monitor labs
85
What is the definition of respiratory alkalosis?
Acute increased alveolar ventilation that decreases PaCO2, pH is generally greater than 7.45
86
Respiratory alkalosis causes?
Pregnancy, high altitude, iatrogenic hyperventilation, salicylate overdose
87
S/sx of respiratory alkalosis?
Lightheadedness, visual disturbances, dizziness - all are caused by vasoconstriction
*remember, this vasoconstriction occurs because if you are hypocarbic, the body generally responds with vasoconstriction because it thinks the tissues need less blood flow because there are less metabolic byproducts*
88
Why does hypocalcemia occur in respiratory alkalosis?
There is greater binding of calcium to albumin
89
S/sx of hypocalcemia?
Paresthesia, muscle spasm, cramps, tetany, circumoral numbness, seizures
Trousseau’s sign (carpo-pedal spasm)
Chvostek’s sign (facial muscle twitch/spasm)
90
Anesthesia management of respiratory alkalosis?
It's generally a consequence of pain, anxiety, full bladder or agitation (try to manage them), make sure you don't have poor mechanical ventilation strategy. Therapeutic hyperventilation can also cause this.
91
What is the definition of metabolic alkalosis?
Marked increase in plasma bicarb usually compensated for by an increase in carbon dioxide
92
What are the physiologic processes that can contribute to metabolic alkalosis?
Renal or extrarenal causes, net loss of H or net gain of bicarb (very common if you are on diuretics), excess citrate
*also called volume depletion or volume overload alkalosis*
93
Common causes of metabolic alkalosis? S/sx?
Hypovolemia, Vomiting, NG suction, Diuretic therapy, Bicarb administration and Hyperaldosteronism
S/sx = lightheadedness, tetany and paresthesia
94
Treatment of metabolic alkalosis?
Depends on the cause:
Volume depletion: saline fluid resuscitation
Gastric loss: PPI’s
Loop diuretics: add K+ sparing diuretics
95
Determine pH: PaCO2 of 64, HCO3 of 39 (round to 3 decimal places)
7.408
96
Determine pH: PaCO2 of 31, HCO3 of 32 (round to 3 decimal places)
7.627
97
Determine pH: PaCO2 of 87, HCO3 of 38 (round to 3 decimal places)
7.263
98
Determine pH: PaCO2 of 49, HCO3 of 22 (round to 3 decimal places)
7.275
99
Determine pH: PaCO2 of 46, HCO3 of 29 (round to 3 decimal places)
7.423
100
As a gas passes through a tube, its drop in pressure is a measure of what?
The resistance of the tube (or rather, the resistance the gas had to overcome to move through the tube)
101
Resistance varies with _______ passing through per________
Resistance varies with the *volume of gas* passing through per *unit of time*
102
Write out the flow (Q) formula
Q = P2 - P1 / R
*Q = flow, P = pressure 2 which is the first part of the tube, P1 is the end of the tube and R is resistance*
103
Describe the basics of laminar flow
Flow is smooth/orderly, particles move parallel to the tube walls and flow is fastest in the center where there is less friction
104
What law governs laminar flow through a tube, taking into account varying pressures, diameter, and viscosity of flow?
Poiseuille's law
105
Describe the basics of turbulent flow
Flow lines are not parallel and consist of "eddies." Unlike laminar flow, the turbulent flow rate is the same across the diameter of the tube
*Eddies = composed of particles moving across or opposite the general direction of flow*
106
Describe generalized and localized turbulent flow
General = When the flow of gas through a tube exceeds the critical flow rate
Localized = Gas flow rate is below the critical flow rate but encounters constrictions, curves, or valves
*critical flow rate is the point in which gas either acts laminar when below the critical flow rate or turbulent when above the critical flow rate*
107
How does resistance impact patient breathing while on a ventilator?
Resistance imposes a strain if the ventilation mode has the patient doing some of the work. Changes in resistance also parallel changes in the work of breathing
108
What part of the breathing circuit is most likely to be the greatest point of resistance?
The ET tube
109
Describe compliance
A ratio of the change in volume to the change in pressure and is measured in ml per cm H20
*if you are distensible, then a small change in pressure creates a large change in volume. If you are non-distensible, then a large change in pressure has a small or no change in volume*
110
What are the most distensible components of the breathing circuit?
Breathing tubes and reservoir bags
111
What factors dictate rebreathing?
FGF, dead space and the design of the breathing system
112
What is the relationship of FGF and rebreathing?
Inverse; the more FGF you have the less you should rebreathe. The less FGF you have, the more you should rebreathe
113
What is the factor that determines whether or not the FGF is enough to prevent rebreathing?
Minute volume/ventilation. FGF must exceed this in order for the patient to not rebreathe.
*so if your minute ventilation is 5.5 L/min, and your FGF is 6 L/min, you are not rebreathing*
114
What are the four types of dead space listed in lecture?
Apparatus = volume in a breathing system occupied by gases that are rebreathed without change in composition
Physiologic = anatomical and alveolar dead spaces
Anatomical = conducting airways; adds H2O vapor
Alveolar = volume of alveoli ventilated but not perfused
115
What can decrease apparatus related dead space?
Having the inspiratory/expiratory limb separation as close to the patient as possible
116
What dead space adds H2O vapor?
Anatomical
117
When is the inspired gas composition identical to the FGF?
When no rebreathing is occuring
118
What are 2 physiologic effects of rebreathing?
You reduce heat/moisture loss
119
What are the desirable characteristics of a breathing circuit?
Low resistance to gas flow
Minimal rebreathing
Removal of CO2 at the rate of production
Rapid changes in delivered gas when required
Warmed humidification of inspired gas
Safe disposal of waste gases
120
List the classifications of breathing circuits
Open = No reservoir bag and no rebreathing
Semi-open = Reservoir bag but no rebreathing
Semi-closed = Reservoir bag and partial rebreathing
Closed = Reservoir bag and complete rebreathing
121
What type of breathing circuit is generally used in anesthesia?
Semi-closed
122
What type of circuit is completely dependent on FGF?
Closed
123
What components make up a breathing circuit?
A facemask, LMA, or ETT
A Y-piece with mask/tube connectors
Breathing tubing
Respiratory valves
Reservoir bag
A fresh gas inflow site
A pop-off valve leading to scavenging
Carbon dioxide absorption canister
124
Describe where the anesthesia mask sits on the face
Fits between the inter-pupillary line and in the groove between the mental process and the alveolar ridge
125
What does the anesthesia mask directly connect to?
The Y-piece or connector
126
What are the pros/cons of connectors/adaptors on a breathing circuit?
Pros: Extends distance between patient and breathing system, Change angle of connection, Allow more flexibility/less kinking
Cons: Increased resistance, Increased dead space, Additional locations for disconnects
127
What is the internal volume of the standard breathing circuit?
400 - 500 ml per meter of length
128
Describe the resistance, distensibility, type of flow and basic characteristics of breathing tubing
It has low resistance, moderately distensible with turbulent flow d/t corrugation. It is large bore, corrugated, plastic and expandable
129
Assuming there are no issues with the circuit valves, where would you expect to find the circuit related/apparatus related deadspace?
At the Y-piece and distal to it
130
What pressure do you use during the circuit pressure check?
30 cm H2O
131
What occurs if the unidirectional valves fail?
The associated limb (expiratory vs inspiratory) becomes dead space
132
What are the basic characteristics of the unidirectional valves
Direct respiratory gas flow in the correct direction
Disks with knife edges, rubber flaps, or sleeves
Low resistance and high competence
Must open widely w/ little pressure
Must close completely and rapidly w/ no backflow
133
What does the inspiratory valve prevent? Expiratory?
I = prevents backflow of exhaled gas
E = prevents rebreathing
134
What is the ideal location for the unidirectional valves?
Near the CO2 absorber canister casing, fresh gas inflow site, and the pop-off valve
135
What are required features of unidirectional valves?
Arrows/directional words, hydrophobic, open/close correctly, clear dome and place between the patient and the reservoir bag
136
What are reservoir bags made of? General shape? Range of volume?
Made of rubber or plastic or latex. Ellipsoidal shape and a volume range of 0.5 - 6.0 L
137
What is the minimum and maximum pressure of the reservoir bag?
30 to 40 - 60 cm H2O
138
What type of reservoir bag has double the distending pressure of rubber bags?
Plastic
139
What are the basic functions of the reservoir bag
Reservoir for anesthetic gases or O2
A means of manual ventilation
Assistance with spontaneous ventilation
Visual/tactile monitor of ventilation
Estimation of volume of ventilation
Protection from excessive positive pressure
140
What is the preferred location of the gas inflow site?
Between the CO2 absorbent and inspiratory valve
141
What is the other name for the APL valve?
Pop-off valve
142
What are the basic functions/characteristics of the APL valve?
Permits gas to leave, user-adjustable, dome valve loaded by a spring and screw cap, controls pressure in the system and releases gas to the scavenging system
143
What occurs if you tighten the APL valve?
As you tighten it, it requires more pressure to open the valve
144
The APL valve adjusts pressure in the system, how many turns (also indicate in what direction) are required to fully open the valve? Fully close it?
1-2 clockwise turns fully closes the valve from open, 1-2 counter-clockwise turns fully opens the valve from closed
145
What occurs to the APL valve on inspiration/expiration during spontaneous, assisted/manual and mechanical ventilation?
Spont = closed on inspiration, open on expiration
Assisted = partially open during both
Mech = bypassed on both
*be careful with the wording here, it is BYPASSED on mechanical, it doesn't matter if the APL valve is open or closed if the patient is on the vent because it is bypassed*
146
What occurs during spontaneous respiration if the APL valve is partially closed?
It mimics CPAP
147
What does the side/center tube of the absorber canister do?
Return gas to the patient
148
What is the product of CO2 coming into contact with the absorber?
Carbonate, water and heat
149
What makes up soda lime?
Calcium hydroxide (~80%)
Sodium hydroxide and potassium hydroxide (~5%)
Water (~15%)
Small amounts of silica and clay
150
When is a CO2 absorber fully exhausted?
When all the hydroxides become carbonates
151
How much CO2 can soda lime absorb?
19% of its weight in CO2
*the exact ratio here is for every 100g you can absorb 26L of CO2*
152
What components make up CaOH lime absorber?
Calcium hydroxide (70%)
Calcium chloride (0.7%)
Calcium sulfate (0.7%)
Polyvinylpyrrolidone (0.7%)
Water (14.5%)
153
What are 3 possible negative outcomes related to CO2 absorbers?
Compound A formation, CO formation and destruction of inhaled gases
154
What are the advantage(s) of LiOH as an absorber? What is it's most common application?
Has much more CO2 absorption capacity, however it is prohibitively expensive and limited to submarine and spacecraft use
155
What are the characteristics of Litholyme?
Lithium chloride catalyst, no reaction with inhaled anesthetic agents
No activators/strong bases
Does not form compound A and CO
No regeneration
pH indicators do not become colorless
Lower exothermic reactivity, reduced risk of fire, and reduced economic/environmental impact
156
What are the characteristics of Spira-lith?
Anhydrous LiOH powder within a nongranular partially hydrated polymer sheet
Larger surface area for reaction
No activators/strong bases
Reduced temperature production
Longer duration of use
Cost-effective
No color indicator
157
What is the only absorber that is not in granular form?
Spira-lith
158
What absorber does not have a chemical indicator?
Spira-lith
159
What is the most common absorbent indicator?
Ethyl violet
160
What absorbers have no activators/strong bases?
Litholyme and Spiro-lith
161
When does color change occur in absorbents?
When the pH drops below 10.3
162
When does bleaching of the CO2 absorber occur?
When the CO2 absorber is exposed to strong fluorescent light over a long period of time. Fairly rare in the OR
163
What change would you expect to see in the capnogram if the CO2 absorber was exhausted?
The baseline of the waveform would increase (shift up)
164
What is the purpose of mesh in the CO2 absorber?
To maximize absorption and minimize resistance
165
Why is excess water in the CO2 absorber detrimental?
It decreases surface area and reduces the efficiency of CO2 absorption
166
What are some characteristics of the mesh in the CO2 absorber?
4 - 8 mesh size, rough/irregular surface
167
What is channeling phenomenon in the CO2 absorber?
This is when an abnormal path of least resistance is present in the absorber. This leads to an uneven pattern of absorption and decreases the functional absorptive capacity
168
How is channeling of the CO2 absorber minimized?
Circular baffles
Placement for vertical flow
Permanent mounting
Prepackaged cylinders
Avoiding overly tight packing
169
What decomposes to create compound A?
Sevoflurane
170
What componet of absorbers are most likely to contribute to compound A formation?
Absorbers containing NaOH and KOH
171
What conditions favor the formation of compound A?
Low FGF, increased absorbent temperature, high sevoflurane concentrations and dehydrated absorbent
172
What gas is most likely to have a reaction to create CO?
Desflurane
173
What conditions favor the creation of CO from desflurane?
High temperature, increased concentration of desflurane, low FGF rates, dry absorbent and strong base absorbents
174
What conditions are favorable to creating exothermic chemical reactions?
A desiccated strong base absorber (baralyme, anhydrous LiOH) that is interacting with sevoflurane
175
With sevoflurane related exothermic reactions, what are the flammable degradation products?
formaldehyde, methanol, and formic acid
176
What are the APSF recommendations to avoid CO2 absorber related incidents?
ALL gas flows turned off after each case
Vaporizers turned off when not in use
Absorbent changed regularly
Change when color change indicates exhaustion
Change all absorbent
2 canister system – change both, not 1
Change absorbent when uncertain about the state of hydration
If using compact canisters, change more frequently
177
What type of injury would most likely occur if the neck is extended with the head turned away whilst supine?
A brachial plexus injury
178
At what pH level is treatment with bicarb indicated? What plasma bicarb level indicates the need for replacement with exogenous bicarb?
pH level of 7.1, and a bicarb level less than 10 mEq/L
179
What type of breathing pattern is associated with a central respiratory problem? Peripheral?
Central = slow and shallow breathing
Peripheral = rapid and shallow breathing
180
What is regeneration of the CO2 canister?
This is when the color indicator starts to turn purple, but once the case is over (and gas is turned off) the color returns to white (it is no longer being exposed to CO2), this means that the absorber is close to being fully exhausted
181
What are the components of a Mapleson circuit?
A reservoir bag, corrugated tubing, APL valve, fresh gas inlet and a patient connection
182
Compared to a circle system, what is missing from a Mapleson circuit?
CO2 absorber, unidirectional valves and separate inspiratory/expiratory limbs
183
What are the other names for the Mapleson circuit?
CO2 washout circuits or flow-controlled breathing systems
184
Describe where the APL is and where FGF enters in a M-A circuit?
APL is near the patient and the FGF enters near the reservoir bag
*note from here on out, M-A is shorthand for Mapleson A, M-B would be Mapleson B and so on*
185
How do you prevent rebreathing in an M-A circuit?
FGF must be greater than or equal to minute ventilation
186
What must your FGF be to prevent rebreathing during controlled ventilation on a M-A circuit?
20 L/min
187
What is the other name for a M-A circuit?
Magill's system
188
Where is the APL and wheres does FGF enter on an M-B circuit?
Both are near the patient
189
Where is the FGF vented on a M-B circuit?
Through the APL valve during exhalation - very inefficient
190
Where is the reservoir bag on a M-B circuit?
At the end of the system (away from the patient)
191
How much should FGF be to prevent rebreathing during spontaneous and controlled ventilation in a M-B circuit?
FGF should be x2 the minute volume in both scenarios
192
What circuit does the M-C circuit most closely mimic?
The M-B circuit, the only difference is M-C does not have corrugated tubing
193
What circuit is the M-C circuit almost as efficient as?
The M-A circuit
194
What is the primary use of the M-C circuit?
Emergency resuscitation
195
Describe the physical setup of an M-D circuit (include location of the reservoir, APL valve and fresh gas inlet)
A 3-way T-piece for patient connection, fresh gas inlet and corrugated tubing. The reservoir is at the end of the circuit, APL is near the reservoir at the end and the fresh gas inlet is near the patient
196
What circuit can PEEP valves be added to?
M-D
197
What is Bain modification?
The addition of FGF coaxial tubing in M-D circuits
198
Describe an M-E circuit
Its just corrugated tubing attached to a T-piece (this also acts as the reservoir).
*No reservoir bag, APL valve*
199
Primary use of an M-E circuit?
Used in spontaneously breathing pts to deliver O2
200
What is the other name of an M-E circuit?
Ayre's T-piece
201
What circuit does an M-F circuit most closely mimic?
An M-E circuit, it just has a reservoir bag added to it
202
What is the advantage an M-F circuit has relative to an M-E circuit?
Excessive pressure is less likely to develop (even though it doesn't have an APL valve)
203
What is the other name of an M-F circuit?
Jackson Rees circuit
204
What Mapleson systems vent fresh gas through the APL at end expiration?
BC
205
What Mapleson systems drive exhaled alveolar gas away from the patient?
DEF
206
List the Mapleson circuits from least to most efficient for spontaneous ventilation
CB < DFE < A
*so the M-A circuit is the BEST choice for spontaneous ventilation and CB are the worst choice*
207
List the Mapleson circuits from least to most efficient for controlled ventilation
A < BC < DFE
*the M-A is the worst choice for controlled ventilation, and DFE are the best choice*
208
What are the advantages of Mapleson circuits? Disadvantages?
Advantages = Simple, inexpensive, and lightweight, Changes in FGF composition result in rapid changes in the circuit, Low resistance to gas flow, No toxic products d/t lack of CO2 absorbent, No degradation of volatiles
Disadvantages = Require high FGF, do not conserve heat/humidity well, hard to scavenge gas and not suitable for MH risk patients (may be impossible to have enough FGF to remove excess CO2)
209
What Mapleson circuit does NOT have scavenging challenges?
M-D
210
In a circle system, rebreathing and conservation of exhaled gas depends on what?
FGF rate
*Higher FGF = less rebreathing and greater waste gas*
211
Where should the unidirectional valve be to prevent rebreathing?
Unidirectional valve must be located between the patient and the reservoir bag on both limbs
212
Where should the fresh gas inflow islet be to prevent rebreathing?
It must not enter the circuit between the expiratory valve and the patient
213
Where should the APL valve be to prevent rebreathing?
It cannot be located between the patient and the inspiratory valve
214
What circuit system are you most likely to encounter in the OR?
Semi-closed
215
How much of the expired gas is rebreathed in low flow anesthesia in a semi-closed system?
50% of the expired gas after CO2 removal
*some of the waste gas is vented through the APL or waste gas valve*
216
What are some examples of semi-open circuits?
Post-op/ICU vents or scuba gear
217
What rate of FGF would you expect with a semi-open circuit relative to a semi-closed system?
Higher FGF with minimal rebreathing/more venting of waste gas
218
What type of anesthesia uses a closed circuit system?
Think old-school anesthesia - the open drop method
219
What are some of the characteristics of a closed circuit system?
Complete rebreathing, rate of oxygen inflow exactly matches metabolic demand, no waste gas vented and volatiles are added to the circuit in liquid form or via a vaporizer
220
What are the pros/cons of low flow anesthesia?
Pros = you use less volatiles, better retention of temperature/humidity and reduced pollution
Cons = hard to rapidly change anesthetic depth, you can accumulate unwanted exhaled gases (CO, acetone, methane) and the volatile degradation products (CO, compound A)
221
Pros/cons of the circle systems?
Pros = you can use low FGF, eliminate CO2, you have stable inspired gas concentration, conserve moisture/heat/gas and you don't pollute the OR
Cons = complex design, CO/compound A concerns, you can compromise Vt during controlled ventilation (volume can change d/t distensibility of the tubing) and disconnections/misconnections of the system
222
What is a common source of closed malpractice claims on anesthesia providers related to the anesthesia circuit?
Misconnections or disconnections that were not identified by the provider
223
What should you do if you suspect a disconnection of the circle system?
Trace back your circuit to try and identify the disconnection
224
What is an example of a self-inflating manual resuscitator?
The ambu-bag
225
What are the components of self-inflating manual resuscitators?
Self-expanding Bag
T-shaped non-rebreathing Valve
Bag Inlet Valve
Pop-off valve
Excess oxygen venting valve
Oxygen reservoir
226
Common uses of self-inflating manual resuscitators?
Hand ventilation in the absences of an oxygen or air source, patient transport, CPR and your emergency ventilation back up
227
Risks of using self-inflating manual resuscitators?
Barotrauma, gastric insufflation, significant variation of Vt/PIP and PEEP and the nonrebreathing valves generate resistance
228
What type of diseases are bacterial filters of the anesthesia circuit used to prevent?
Airborne diseases/pathogens
229
Where would you find a bacterial filter in the circle system?
The expiratory limb
230
What is the relationship of small pore/compact matrix to a less dense/larger pore size arrangement of bacterial filters?
Small pore has higher airflow resistance but a larger surface area to catch contaminants, large pore has less resistance but less surface area
*both have permanent electrical polarity*
231
What are the characteristics of hydrophobic bacterial filters?
Prevent water penetration, increase resistance at the cost of decreased efficiency
232
Where would you place a combination filter + HME?
Placed at the Y-piece and can be both an inspiratory and expiratory barrier
233
2 common complications of bacterial filters?
Obstruction (sputum, fluid, aerosols) or leakage (such as from the housing of a gas line filter)
234
What part of the breathing system is recommended to have a filter?
The expiratory limb
235
What parts of the breathing system is the addition of a filter optional?
External sampled gas line, inspiratory limb and the airway
236
What type of filter is recommended for the airway?
HMEF (heat and moisture exchange filter)
237
When is an inspiratory limb filter recommended rather than optional?
If suspected contamination has occurred
238
What are the definitions of; humidity, absolute humidity, relative humidity and water vapor pressure?
Humidity: Amount of water vapor in a gas
Absolute humidity: Mass of water vapor present in gas in mg H2O/L of gas
Relative Humidity: Percent saturation; amount of water vapor at a particular temp
Water Vapor Pressure: Pressure exerted by water vapor in a gas mixture
239
What term refers to the mass of water vapor in a gas?
Absolute humidity in mg H2O/L of gas
240
What term refers to the % saturation or amount of water vapor at a specified temperature?
Relative humidity
241
At what point has most of the heating/humidification of the inspired gas occurred in the body?
By the mid-trachea
*be careful with the wording here, it said MOST not ALL. All would be asking what is the last point humidification/heating has occurred which would be the carina*
242
What is the isothermic saturation boundary, and where does this generally occur in the body?
At the carina and it is when the gas is heated to body temperature and fully saturated with water
243
What is the absolute humidity of the body?
44 mg/L (100% relative humidity)
244
What happens to cold gas as it enters the body?
D/t the fact it has little capacity to hold water vapor and low absolute humidity, the upper airway transfers large amounts of heat and moisture to the inspired gas
245
________inspired gas may trigger a bronchospasm. MOA?
Cool/cold and the exact MOA is poorly understood
246
Negative effects of underhumidification?
Damages the respiratory tract (which can thicken secretions, decrease ciliary function, impair surfactant and make the mucosa susceptible to injury), the body loses heat (because it has to expend heat to humidify the air) and can obstruct the tracheal tube from the thickened secretions
247
Negative effects of overhumidification?
Water condenses in the airway, reduces mucosal viscosity and increases risk of water intoxication, inefficient muco-ciliary transport, increases airway resistance, risk of pulmonary infection, dilutes surfactant, causes atelectasis and V/Q mismatch and may obstruct sensors
248
Give an example of a passive and active humidifier
Pass = heat/moisture exchanger that may or may not have a filter (generally an HME or HMEF)
Active = a heated humidifier
249
Describe the basics of how an HME/HMEF work
They conserve the exhaled heat/water and return them to the patient
250
Where should an HME/HMEF be placed?
Close to the patient, between the Y-piece and proximal end of the ET tube
251
How does an HME impact ETCO2 reading, resistance and dead space?
It can cause a low ETCO2, increase resistance and dead space
252
What type of HME can reduce efficiency with large Vt?
Hydrophobic models
253
Describe a hygroscopic HME
A paper or other fiber barrier coated with moisture retaining chemicals that absorb water in exhalation and release it during inspiration
*prone to becoming saturated, if this occurs you have increased resistance to respiration and reduced heat/moisture retention*
254
Describe a hydrophobic HME
It is a pleated hydrophobic membrane with small pores and more efficient filtration of pathogens
255
What are the 4 types of humidifiers?
Bubble/cascade, pass-over, counter-flow and inline
256
Where are humidifiers generally placed?
In the inspiratory limb downstream of the unidirectional valve
*condensation can decrease Vt, use of water traps helps mitigate this issue*
257
Describe how a bubble/cascade humidifier works
It creates water vapor through bubbling action (think of the humidity canisters that can be added to a NC)
258
Describe how a pass-over humidifier works
You pass gas over a heated water reservoir, the gas then picks up water vapor as it passes over the heated reservoir
259
Describe how a counter-flow humidifier works
Water is heated outside the vaporizer then pumped into the humidifier and the vapor is then picked up
260
Describe how an inline humidifier works
It makes use of plastic capsules to inject heat/water into the ventilator circuit right before the Y-piece
261
Pros/cons of humidifiers?
Pros = can deliver saturated gas at body temperature or higher and is more effective than HME
Cons = bulky, electrical malfunction/thermal injury, contamination/cleaning issues, more expensive than HME and water aspiration risk
262
What Mapleson circuit has the FGF entering the circuit away from the patient?
M-A
*the others have the FGF inlet close to the patient*
263
On the spectrum of open through closed circuits, which ones have no rebreathing?
Open and semi open
*semi-closed has partial rebreathing, closed has complete rebreathing*
264
What absorbers do not contain NaOH or KOH?
Amsorb, Litholyme and Spiralith
265
What absorber is primarily LiCl?
Spiralith
266
What are the 2 primary functions of the anesthesia face mask?
Preoxygenation and denitrogenation
267
Describe the primary components of the face mask
Body - transparent and provides shape
Seal - inflatable cushion
Connector - 22mm diameter with a circular right with prongs for straps
May have a pacifier, port or scent
268
At what pressure are you likely to have minimal leak from the face mask?
20 - 25 cm H2O
269
When are you most likely to use the two-handed C-technique?
During difficult ventilation, such as obese or an edentulous patient
270
What are the risk factors for difficult mask ventilation?
Male, age over 55, beard, edentulousness, OSA/snoring, BMI greater than 30
271
What are some strategies to overcome difficult mask ventilation?
Use of an OPA/NPA, 2-hand technique, cut the beard, use of tegaderm
272
What should be implemented if, despite the use of several strategies to mitigate this, you are still unable to adequately ventilate a patient using mask ventilation?
Emergency measures - the difficult airway algorithm
273
How does an OPA reduce the work of breathing during spontaneous ventilation?
By lifting the tongue and epiglottis
274
Describe the difference in the size measurements of an OPA vs an NPA (not looking for how you would measure them on a patient, this is more of in the realm of how an IV's size is measured in gauges, like 18 or a 20 gauge)?
OPA size is designated in mm
NPA size is designated in French
*remember, French size increases with the base number, so 14 french is smaller than 16 french*
275
How would you measure an OPA?
Measure corner of the mouth to the angle of the jaw or the earlobe
276
What are the 2 primary ways to insert an OPA?
Insert the airway upside down or tilted to the side, then invert it as you advance , option 2 is the tongue depressor method
277
Im what clinical setting would you expect you would most commonly use a bite block?
In endoscopy (you need to keep the patient from chowing down on the broncho/endoscope)
278
What is the primary advantage of the NPA over the OPA?
The NPA is tolerated in patients with intact airway reflexes and is preferable with loose teeth, oral trauma, gingivitis, limited mouth opening
279
Contraindications to NPAs?
Basilar skull fracture
Nasal deformity
Hx of epistaxis (relative contraindication)
Pregnancy
Coagulopathy
280
What does the design of the NPA most closely mimic?
A shortened tracheal tube
281
What structure of the NPA prevents complete passage into the nose/upper airway?
The flange at the outer end (or the "trumpet" end)
282
How do you size an NPA? What step is important prior to insertion?
Measure from the bony mandible or the nostril to the external auditory meatus and the important step prior to insertion...
283
Complications of OPA/NPA placement?
Airway obstruction, ulceration of nose/tongue, dental/oral damage, laryngospasm, latex allergy (more so with older models) and retention/swallowing
284
What is the most common cause of airway obstruction related to OPA/NPA placement?
Incorrect placement
285
Who created the first supraglottic airway?
Dr. Archie Brain
286
T/F: you are able to spontaneously ventilate with an LMA inserted?
True
*you can also use PPV*
287
Describe the basic characteristics of the LMA classic
Shaped like a tracheal tube proximally
Elliptical mask distally
Sits in hypopharynx and surrounds the supraglottic structure
An inflatable cuff
Latex free, and depending on the model it can be reusable or disposable
288
What LMA size is used for neonates/infants up to 5 kg?
1
289
What LMA size is used for infants between 5 - 10 kg?
1.5
290
What LMA size is used for infants/children between 10 - 20 kg?
2
291
What LMA size is used for children between 20 - 30 kg?
2.5
292
What LMA size is used for children between 30 - 50 kg?
3
293
What LMA size is used for adults between 50 - 70 kg?
4
294
What LMA size is used for adults between 70 - 100 kg?
5
295
What LMA size is used for adults over 100 kg?
6
296
What problem would likely occur if the LMA was too small? Too big?
Small = gas leaks during positive pressure ventilation
Big = won't seal/sit over the glottis, greater chance of sore throat and can press on the lingual, hypoglossal and/or recurrent laryngeal nerves
297
Describe the basic steps of inserting an LMA
Well lubricated (HAWK TUAH); cuff down
Held like pencil
Upward against the hard palate
Follows the posterior pharyngeal wall
Smooth motion
Should feel it curve around downward in the airway then come to a stop
298
If your LMA has a balloon that is inflated after insertion, what physical changes would you see to the patient after inflation?
The neck may bulge and the LMA may slightly rise
299
What can you do if you have difficulty during LMA insertion?
Lift the jaw, pull tongue forward, slightly inflate the balloon or try a different insertion technique
300
What differentiates an LMA unique from the LMA classic?
It is made of PVC, stiffer/less compliant cuff and is single use only. Insertion is the same as the LMA classic
301
What differentiates an LMA proseal from the LMA classic?
Wire reinforced but shorter. Is the first 2nd generation LMA with a hole that allows for gastric access
302
What feature differentiates 1st gen and 2nd gen LMAs?
The presence of a gastric port
303
What LMAs are most likely to be MRI incompatible? Why?
LMA classic - most have a metal spring in them and the LMA proseal is wire reinforced
304
What LMA is made of medical grade thermoplastic elastomer?
IGEL
305
What LMA is cuff-less (non-inflatable)?
IGEL
*It can also act as a conduit for intubation*
306
Pros/cons of LMAs?
Pros: Ease and speed of placement, Improved hemodynamic stability, Reduced anesthetic requirements, No muscle relaxation needed, Avoidance of some of the risks of tracheal intubation
Cons: Smaller seal pressures than ETTs, No protection from laryngospasm, Little protection from gastric regurgitation and aspiration (more so in First-generation LMAs)
307
Per lecture, what LMA provides the best gastric regurgitation protection?
IGEL
308
T/F: you can place an LMA just using propofol for induction
True, LMA insertion does not require paralysis
309
What is the light source of a DL (DL = direct laryngoscope from here on out)?
Either a light bulb or a fiberoptic source
310
What is the most common size of MAC blades used to intubate adults?
Size 3 or 4
311
What is the most common size of Miller blades used to intubate adults?
Size 2 or 3
312
What blade "Has been shown to cause greater cervical spine movement?"
MAC
313
What blade has less "force", less head extension and less C-spine movement?
Miller
314
What blade is better for smaller mouths and longer necks?
Miller
315
Why is a MAC blade generally associated with an easier time intubating?
Because use of this blade requires the patient to be able to open their mouth more or have a larger mouth opening.
*So this "easier time intubating" has nothing to do with the function of the blade, but rather the anatomic conditions present that allow you to use a MAC*
316
What is the goal when using a MAC blade?
To visualize the epiglottis, then advance the tip into the vallecula
317
What is the goal when using a Miller blade?
To visualize the epiglottis, then directly lift the epiglottis
318
T/F: you can use a miller like a MAC, and use a MAC like a miller blade?
True
319
Describe the sniffing position
35 degree lower cervical flexion; 80 to 90 degree head extension at the atlanto-occipital level
Create an imaginary horizontal line connects the external auditory meatus and sternal notch
320
What side off the mouth should you insert your blade?
Same side of your dominant hand, this is generally the right side for most people.
*blade is generally held in your non-dominant hand*
321
What devices should you consider using for a difficult airway?
Fiberoptic scope or a video largynoscope. An OPA may also help
322
Alignment of what axis's create ideal conditions to intubate?
Alignment of the oral/pharyngeal/laryngeal axis
323
Describe how to correctly displace the larynx during intubation
BURP: backwards, upwards, rightwards pressure
324
What position can help optimize intubation for an obese patient?
Ramped position (use a wedge or pillows to accomplish this)
*create an imaginary line from the ear to the sternal notch with an obese patient to help guide correct positioning*
325
What type of filter is recommended for the expiratory limb?
A pleated mechanical filter
326
What are the 2nd gen LMAs?
LMA proseal and IGEL
327
Describe the Shikani optical stylet
A stainless steel lighted stylet with a malleable distal tip. Has an eye piece for visualization and an oxygen port for oxygen insufflation
328
Where should the tip of a shikani optical stylet be during insertion?
Anterior at all times to avoid injury
*same as a bougie*
329
What are some functions, other than intubation, of a shikani optical stylet?
As a light wand, to check ET tube or DLT placement
330
Pros/cons of the shikani optical stylet?
Pros = Easy to use for routine and difficult intubations, Trachea is visualized, esophageal intubation should not occur, Decreased incidence of sore throat, Results in less c-spine movement over conventional laryngoscopy
Cons = Longer intubation time, cannot be used with nasal intubation and cannot be adjusted into a precise direction compared to a traditional malleable stylet
331
What are the 4 types of video larygnoscopes?
Glide-scope, Co-Pilot, King and McGrath
332
Pros/cons of video laryngoscopes?
Pros: Magnified anatomy, Some scopes have curved/straight blades to mimic laryngoscopes, Operator and assistant can see, May result in decreased c-spine movement, Further distance from infectious patients, Demonstrates correct technique in legal cases
Cons: Requires video system, Portability varies, Strongest predictors of failure: altered neck anatomy with presence of a surgical scar, radiation changes, or mass
333
What video laryngoscope is this?
King
334
What video laryngoscope is this?
McGrath
335
What video laryngoscope is this?
Glide-Scope
336
What video laryngoscope is this?
Co-Pilot
337
What is the most frequent anesthesia related claim?
Dental injury
338
What teeth are most likely to be injured during laryngoscopy?
The upper incisors or restored/weakened teeth
339
Common complications of laryngoscopy?
C-spine injury (d/t aggressive head positioning or poor head stabilization), Damage to other structures (think violent movements with the laryngoscope) and swallowing/aspirating foreign body (light bulbs or teeth)
340
What soft structural damage can occur with violent laryngoscopy?
Abrasions/hematomas, lingual and/or hypoglossal nerve injury, arytenoid subluxation or anterior TMJ dislocation
341
What factors can affect the resistance of a breathing system?
Diameter of the tube, the length of the tube, configuration changes and connectors
342
What are the manufacturing requirements of breathing tubes?
Low cost, non-toxic to tissue, easily sterilized, non-flammable, smooth/non-porous to allow passage of instruments (and discourage secretion adhesion), ability to maintain shape, sufficient wall strength, conforms to patient anatomy, lack of reaction with anesthetic agents/lube and latex free
343
Describe the basic design of the breathing tube
Both walls are circular to decrease kinking, can be shortened on the machine end, has a slanted bevel and murphy eye
344
What is the purpose of the bevel and the murphy eye on a breathing tube?
Bevel = helps view the larynx
Murhpy eye = provides alternate pathway for gas flow
345
What is the primary purpose of a RAE tube?
To allow for surgery around the head/neck (the tube curls away from the surgical field as opposed to a standard ET tube. This tube can curl down towards the feet or curl up towards the forehead depending on the surgical field)
346
What does RAE stand for in RAE tube?
Ring-Adair-Elwin
347
What type of breathing tube is this?
RAE tube
348
Pros/cons of a RAE tube?
Pros: Facilitate surgery around head and neck, Temporarily straightened during insertion, Increased tube diameter along with increased distance from tip to curve, and easy to secure
Cons: Difficult to pass suction or a scope, increases airway resistance d/t the bend
349
What are the other names of the armored breathing tube?
Reinforced, anode or spiral embedded tubes
350
Pros/cons of armored tubes?
Pros: resistant to kinks/compression and is good for head/neck/tracheal surgery
Cons: need a stylet or forceps to insert, difficult to use for nasal intubation, cannot be shortened and can be permanently damaged from biting
351
What kind of breathing tube is this (include all applicable names)?
Armored tube, reinforced, anode or spiral embedded tube
352
What is the primary component making up a laser resistant breathing tube?
Metallic, silicone or a metal mixture
353
Primary purpose of a laser resistant breathing tube?
It's in the name; reflect the laser beam
354
What feature of laser resistant breathing tubes would allow the surgeon to know if they had punctured/ruptured the inflatable cuff?
There are methylene blue crystals in the cuff that dissolve when saline is put into the cuff, if the cuff ruptures, the dye quickly spreads alerting the surgeon to cuff rupture
355
In what order do you fill the cuffs of a laser resistant breathing tube?
Distal cuff (smaller balloon) first then the proximal cuff (larger balloon)
356
What breathing tube is this?
Laser resistant
*the trick here is either look at the surface of it which appears metallic or the easier option is to notice how there are two cuffs at the end of the tube, a hallmark of laser resistant tubes*
357
What side of the breathing tube will have the cuff? How are they read?
On the bevel side, and it is read from patient side to machine side
358
What are the safety standards for the markings on breathing tubes?
Must include oral or nasal or both, size of the internal diameter in mm, manufacturer, graduated markings in cm from the patient end, cautionary note that they are single use and a radiopaque marker at the patient end
359
What is the ideal pressure/volume of the inflatable cuff?
18 - 25 mmHg which is about 8 - 10 cc of volume
360
Why are high-volume low pressure cuffs our primary cuff rather than low-volume high pressure cuffs?
The high volume/low pressure adapt to the tracheal wall, and because of the lower pressure they are far less likely to cause ischemia
361
Pros/cons of high-volume/low-pressure cuffs?
Pros: easy to regulate pressure and pressure applied to the trachea is less than mucosal perfusion pressure
Cons: More difficult to insert, may obscure the view of the tube tip and larynx, Cuff is more likely to be torn during intubation, More likely to have a sore throat, May not prevent fluid leakage, Easy to pass NGT, esophageal stethoscopes around cuff
362
What 2 factors from low-volume/high pressure cuffs contribute to the high incidence of mucosal ischemia?
It requires a large amount of pressure to achieve a seal and it distends/deforms the trachea
363
Pros/cons of low-volume/high-pressure cuffs?
Pros: better aspiration protection, better visibility during intubation and lower incidence of sore throat
Cons: High incidence of mucosal perfusion injury and if the breathing tube is needed post-op you MUST swap it out for a low-pressure cuff
364
What 4 factors can change the cuff pressure (include if they increase or decrease pressure)?
Nitrous (increase) hypothermic cardiopulmonary bypass (decrease) increase in altitude (increase) and coughing/straining/change in muscle tone (increase)
365
What are common causes of trauma from ET tubes?
Excessive force/repeated attempts (varies with skill, difficulty of airway and amount of muscle relaxation), not keeping the stylet inside the tube and not following guidelines for nasal intubation (not using vasoconstrictors or dilating the nose prior to nasal intubation)
366
What 2 steps should be done to minimize trauma during nasal intubation?
Use nasal vasoconstrictors and pre-dilate the nasal passage
367
What populations are bronchial intubations more common in?
Kids and females
*their right mainstem is less of a deviation from the trachea, making it easier to intubate*
368
At what distance should the tube be secured at in females vs males?
Female = 21 cm, Male = 23 cm
*both at the teeth*
369
How does distance to the carina change with trendelenburg or laparoscopy?
Distance to carina decreases
*this can cause inadvertent bronchial intubation*
370
Where can upper airway edema occur?
Anywhere along the ET tube
371
Why is upper airway edema very dangerous in young children?
Because their cricoid cartilage completely surrounds the subglottic area, meaning they have no ability to stretch the airway (or rather the airway has no ability to expand in an emergency)
372
Timeframe for upper airway edema to occur?
As soon as 1-2 hours post op up to 48 hours
*you can minimize this by avoiding irritating stimuli. Maintain appropriate anesthetic depth and avoid doing surgery if the patient has or has recently had a URI*
373
What is a vocal cord granuloma?
A mass that forms after trauma related to an ET tube insertion
*more common in adult females*
374
Common causes of vocal cord granuloma?
Trauma during insertion, too large of a tube, infection or excessive cuff pressure
375
S/sx of vocal cord granuloma? Treatment?
Persistent hoarseness, feeling of throat fullness, chronic cough, intermittent loss of voice
Tx = laryngeal evaluation and voice rest
376
What indicates you are in the correct position when using a bougie?
You feel a clicking sensation with the bougie (the clicking sensation comes from contact with the tracheal rings)
*Be sure to keep the tip anterior when inserting*
377
Primary purpose of the Magill forceps?
To help guide the tube during a nasal intubation
*take care to not damage the cuff or being lodged in the Murphy eye*
378
Common indications for lung isolation?
Thoracic surgery, control of contamination or hemorrhage or a unilateral pathology (fistula, ruptured cyst)
379
What angle does the R/L mainstem deviate from the trachea?
R = 25 degrees, L = 45 degrees
380
Average length from the carina to the take-off point in the R/L mainstem bronchus
R = 2.5 cm, L = 5.5 cm
381
Other than its deviation from the trachea, what other factor makes it easier to intubate the right mainstem?
It has a straighter and larger diameter
382
What is the trick to easily differentiate adult vs kids sized DLTs?
Adults = odd, kids = even
Adults sizes: 35, 37, 39, 41 French
Kids sizes: 26, 28, 32 French
383
What is the most commonly used DLT? When do we use the other?
A Left DLT
A right DLT is commonly used in; left pneumonectomy, left lung transplant, if left mainstem bronchus stent is in place or a left tracheo-bronchus disruption
384
Describe the process of inserting a DLT
Similar to a standard ET tube: advance through the larynx with angle tip anterior, once the bronchial cuff passes the cords rotate the tube 90 degrees (bronchial portion pointed towards its bronchus), verify location via fiberoscopy (ensuring the blue cuff is just below the carina) and inflate under direct visualization, ensure no cuff herniation and isolate a lung to confirm function
385
Common DLT complications?
Tube malposition - leading to unsatisfactory collapse, hypoxemia (adjust or reinsert tube), if there are patient comorbidities at play, you may need PEEP to the dependent lung or consider intermittent 2 lung ventilation
*in general, the dependent lung is the ventilated lung*
386
What should you do if the DLT is in the wrong mainstem? If too proximal?
Wrong mainstem = remove and reinsert
Too proximal = use fiberoptic and advance to the correct position
387
When is a DLT not advisable/not the first choice to isolate a lung?
Nasal intubation, Difficult intubation, Patients with tracheostomy, Subglottic stenosis, Need for continued postoperative intubation, If a single-lumen tube is already in place - critically ill pts
388
What is the primary advantage of a bronchial blocker over a DLT?
You can block a segment of a lung without isolating the entire lung
389
Common bronchial blocker difficulties?
Right upper lobe bronchus takeoff is high, tracheal bronchus insertion is common (only if this anatomic feature is present), fixation by staples during surgery or perforation by suture needle or instrumentation
390
What anatomical feature would explain seeing 3 lumens when viewing the R/L mainstem?
The presence of a tracheal bronchus
391
What absorbents do not contain NaOH and/or KOH?
Amsorb, Litholyme and spiralith
392
What absorbent do contain NaOH and/or KOH?
Sodasorb, Medisorb and Dragersorb
