Thoracic II

Question 1

What are some general causes of hypoxia?

Answer 1

Common Causes

• Inadequate O₂ supply (low FiO2)
• Hypoventilation
• V:Q inequities resulting from
  
  • Atelectasis, compression, pulm edema
  • Decreased O₂ carrying capacity
  • Related to anemia
• Left shift of O₂-Hgb dissociation curve
  
  • Caused by: hypothermia, decrease in 2,3 DPG (ie banked blood), alkalosis, hypocarbia.
• Review O2-Hgb curve
  
  • Normal adult P50= 26.5 partial pressure of O2
  • CADET faces RIGHT (right shift= release O2; left shift= love, hold onto O2)
    
    • ⇑ CO2
    • ⇑ Acidosis
    • ⇑ DPG
    • ⇑ Exercise
    • ⇑ Temperature
• Review arterial O2 content calculation
  
  • CaO2= (1.34 x Hgb x Sao2) + (PaO2 X0.003)
    
    • remember Hgb most important portion of oxygen carrying capacity in blood

Question 2

What are some mechanisms of hypoxemia during anesthesia?

Answer 2

• Mechanical failure
  
  • Most common cause:
    
    • disconnect from 02 supply elbow of ETT (most common)
    • followed by empty cylinders
    • failure of pipeline (least common)
• Esophageal intubation
• Hypoventilation/hyperventilation
• Decreased FRC
• R to L Shunt
• Pulmonary embolism, ARDS

Question 3

What are some potential hazards of O2 therapy?

Answer 3

• Hypoventilation
  
  • Leads to CO2 retention → hypoventilation in pts with COPD
• Oxygen toxicity-
  
  • Avoid FiO2 100% for periods >12 hours
  • 80% >24H
  • 60%>36H
  • Can cause:
    
    • sub-sternal pain,
    • mild carinal irritation,
    • cough,
    • impairment of ciliary motion,
    • alveolar epithelial damage
    • interstitial fibrosis
• Retrolental fibroplasia
  
  • Newborns with high concentration of O2
• Fire hazard
  
  • Oxygen supports combustion
• Absorption Atelectasis
  
  • Atelectic shunting due to sum of the partial pressures in alveolar gas (760mmHg) greatly exceeds the pressure venous blood (147mmHg), gases diffuse into the blood and a rapid collapse of the alveoli occurs
• Free radical damage from hyperoxia which can be damaging at cellular level
• FiO₂ = fraction of inspired gas mix that is O₂
• Clinical Goal = SaO2 >90%

Question 4

What are 3 main components for lung protective ventilation?

Answer 4

1. low tidal volume (assumed to reduce stress and strain of the lung)
   
   1. (1) low tidal volume, a small tidal volume is reasonable, and a volume of 6 to 8 mL/kg/body weight, as is generally suggested, is the same size of what a normal subject is breathing spontaneously when awake
2. recruitment maneuver (assumed to reopen any collapsed alveoli)
   
   1. breath hold at end inspiration to 20cmH2o for 15-20 seconds
3. PEEP (assumed to keep a recruited lung open during ongoing anesthesia and surgery)
   
   1. PEEP, opening up and keeping the lung open is also reasonable and even important. Both a recruitment maneuver and PEEP will achieve this.

• These three tools have been adopted from intensive care, and one may ask whether they are equally useful in the mechanically ventilated, essentially lung healthy, anesthetized patient.

Question 5

What is peep and its effect? CPAP and its effect?

Answer 5

Positive-end expiratory pressure (PEEP)

• small positive A/W pressure at the end of expiration
• Uses
  
  1. Increases FRC
  2. Prevent A/W closure
  3. Improves oxygenation
  4. Aids ventilation in ARDS

Continuous positive airway pressure (CPAP)

• Positive pressure applied continuously to the A/W
• Uses
  
  1. S/P extubation to improve oxygenation
  2. Sleep disorders
  3. OLV to non-dependent lung

Question 6

What are some physiologic considerations of one-lung ventilation?

Answer 6

• Hypoxic pulmonary vasoconstriction
• Lateral Decubitus Position
• Open Chest
  
  • One-lung Ventilation

Question 7

What is hypoxic pulmonary vasoconstriction?

Answer 7

• Local reaction occurring in hypoxic areas of the lung
• Vasoconstriction in response to hypoxia in pulmonary arteries
  
  • thought to be able to decrease the blood flow to the nonventilated lung by 50%
    
    • this prevents hypoxemia
    • precapillary vasoconstriction is helpful
• Onset and resolution are rapid based on changes in PaO2 (reflex initiated when PaO2<100mmHg)
  
  • Occurs in 2 phases
    
    • 1) initial phase within minutes
    • 2)Delayed phase at 40 minutes
• Triggered by alveolar hypoxia, not arterial hypoxia
• May be inhibited by calcium channel blockers, volatile agents and vasodilators ​
• HPV is effective in ⇣ shunt flow (we like HPV with OLV)

Question 8

What is the mechanism for hypoxic pulmonary vasoconstriction?

Answer 8

• Exact mechanism is unclear
• Hypoxia induced vasoconstriction in pulmonary vessels is different from other vessels which vasodilate in the presence of hypoxia
• Possible mechanism
  
  • Due to direct action of alveolar hypoxia on pulmonary smooth muscles sensed by the mitochondrial electron chain with reactive O2 species serving as a second messenger to increase calcium and smooth muscle vasoconstriction
  • Endothelial derived molecules modulate the primary response
  • Other humoral and neurogenic influences are probably involved

Question 9

What are some factors that inhibit HPV?

Answer 9

• Factors known to decrease Hypoxic pulmonary vasoconstriction and thus worsen the right to left shunting

Avoid drugs or events that will inhibit HPV:

1. Hypervolemia/hypovolemia
2. Excessive tidal volume or PEEP
3. Hypocapnia
4. Hypothermia
5. Acidosis
6. Volatile agents > 1 MAC
   
   • Usually okay at 1 MAC
     
     • Nitrous Oxide has a clinically insignificant effect
       
       • Associated with increased postthoracotomy radiographic atelectasis in dependent lung compared to air/o2 mixture.
       • Avoid N2O during thoracic anesthesia
     • IV anesthetics minimal inhibition of HPV
7. Vasoactive medications
8. Vasodilators (inhibit HPV):
   
   1. Nitroglycerin,
   2. Nitroprusside,
   3. Dobutamine,
   4. Calcium channel blockers,
   5. B2 agonists (isoproterenol)

• At doses less than or equal to 1 MAC, modern VA (iso, sevo, des) are weak, equipotent inhibitors of HPV
  
  • Inhibition of HPV response by 1 MAC of volatile is approximately 20% of total HPV response, and could only account for 4% net increase in total arteriovenous shunt during OLV, which it too small to be detected clinically
• Volatile causes less inhibition of HPV when delivered to active site of vasoconstriction via pulmonary arterial blood than via alveolus
  
  • During OLV, VA only reaches the hypoxic lung pulmonary capillary via mixed venous blood. No clinical benefit in oxygenation during OLV has been shown for TIVA
    
    • Sevo group had significantly less postop pulmonary complications and lower 1 year mortality.

Question 10

What are some factors that decrease blood flow?

Answer 10

• Shunt is Increased by decreasing blood flow to the ventilated lung
  
  • High mean airway pressures
  • Low FiO2
  • Vasoconstrictors
  • Intrinsic PEEP

Question 11

Review of preop evaluation for thoracic patient?

Answer 11

1. All patients: assess functional capacity, spirometry, discuss postoperative analgesia, discontinue smoking
2. Patients with ppoFEV1 or DLCO < 60%: exercise test
3. Cancer patients: consider the 4 Ms: mass effects, metabolic effects, metastases, medications
4. COPD patients: arterial blood gas, physiotherapy, bronchodilators
5. Increased renal risk: measure creatinine and blood urea nitrogen levels
6. Review initial assessment and test results
7. Assess difficulty of lung isolation: examine chest radiograph and computed tomographic scan
   
   • most useful predictor of difficult endobronchial intubaiton is chest imaging
   • distal airway problems may only be detected by CT.
     
     • can detect “saber-sheath” trachea, which can cause obstruction of tracheal lumen for a left-sided DLT during ventilation of dependent lung for a left thoracotomy
     • extrinsive or intrinsic compression of intraluminal obstruction of mainstem bronchus can interfere with placement and may only be evident with CT.
8. Assess risk of hypoxemia during one-lung ventilation

Question 12

Considerations for premedication for thoracic cases?

Answer 12

• Typically avoided
• Small amount of short acting BZD if need for line placement
• Consider anti-sialogogue (Glycopyrolate)
  
  • Can aid in visualization with FOB
• Empiric antibiotic coverage at induction (routine prophylaxis is Cephalosporin)

Question 13

What might you need for the room setup for thoracic surgery?

Answer 13

• Note frequent lateral position
  
  • Must anticipate need for invasive monitoring at the outset
  • Monitoring Requirements – based on degree of disease and the type of procedure
• ECG, BP, pulse oximetry, temperature probe
• I-stat for PaO2 and PaCO2 monitoring
• A-line: continuous BP and blood sampling
  
  • ABGs on Room air and throughout case
    
    • Need baseline PaO2 to help predict how they will do on OLV
      
      • Pao2 >400 with Fio2 1.0 is unlikely to desat during OLV
      • PaO2 of 200 is prone to desat during OLV although both may have SPO2 values of 99-100%
    • ETCO2 is less reliable indicator of PaCO2 during OLV than during TLV
      
      • PaCO2 PETCO2 gradient tends to increase during OLV
• CVP/ PA +/-
• 2 large bore IV’s are a MUST
• Sidestream spirometry- watch flow volume loops and I/E volumes
• FOB and difficult airway cart in room
  
  • Cook exchange catheter
• TEE
  
  • TEE that apply to thoracic surgery include hemodynamic instability (Fig. 53.11), pericardial effusions, cardiac involvement by tumor, air emboli, pulmonary thromboendarterectomy, thoracic trauma, lung transplantation, and pleuropulmonary disease
  • On rare occasions, can detect undiagnosed PFO with reversal of flow caused by high peep intraop (causes increase RAP)
• Non-invasive CO monitors???- unreliable with open chest
• IV pumps for precise fluid/ pressor management
• Consider CV drug box

Question 14

What effect can OLV have on ETCO2 and PaCO2?

Answer 14

• ETCO2 is a less reliable indicator of PaCO2 during OLV than during TLV
• PaCO2- PETCO2 gradient tends to increased during OLV
  
  • PETCO2 is less directly correlated with alveolar MV during OLV, because PETCO2 also reflects lung perfusion and cardiac output
    
    • it gives relative changes in perfusion of the two lungs independently during position changes and OLV
      
      • when turned lateral, PETCO2 of independent lung will fall relative to dependent lung, reflecting increased perfusion to dependent lung and increased deadspace to independent lung
        
        • however, excretion of CO2 will be higher from independent lung because of increased fractional ventilation
• WIth onset OLV, PETCO2 of the dependent lung will fall transiently as all of the MV is transferred to this lung.
  
  • THEN PETCO2 will rise as fractional perfusion to dependent lung increases due to collapse of lung and pulmonary vasoconstriction to nonventilated lung.
  • If no correction in MV, then net result will be increased baseline PaCO2 and PETCO2 with increased gradient.
    
    • severe >5 mmHG or prolonged decreases in ETCO2 can indicate a maldistribution of perfusion b/w ventilated and nonventilated lung and may be early warning sign of patient that will desat during OLV

Question 15

What monitoring may be indicated during thoracic cases?

Answer 15

• Pretty much everyone including healthy patients without special intra-operative conditions (ex. VATS)
  
  • Arterial catheter
    
    • We almost always do an art line- pretty much all thoracic surgery has a risk of great vessel/ heart compression
• Add CVP +/- PA cath
  
  • pneumonectomy cases, complex procedures, or redo thoracotomies
    
    • may need for vasoactive gtt
  • R IJ CVP preferred (lower risk pneumo)
  • CVP unreliable in SVC syndrome
    
    • also unreliable in lateral position with chest open
• Sick patients with significant cardiopulmonary disease who will likely undergo further compromise with special intra-operative needs.
  
  • patient with cor-pulmonale undergoing lobectomy or pneumonectomy
  • Arterial catheter
  • CVP + PA cath
    
    • in lateral position with open chest, PA pressures are less accurate since we don’t know if tip lies in dependent of nondepednent lung
  • Probably intra-op TEE
  • mixed venous monitoring

Question 16

Considerations for difficult airway in thoracic case?

Answer 16

• Always review AW/ thoracic assessment, history, xrays, and CT scans!
• Concurrent cancer of the pharynx in the epiglottic area (5-8% of lung ca)
• Radiation to head and neck
• Previous aw surgery
• Awake bronchoscopic exam before surgery if in doubt!
• Establish AW with SLT in a difficult AW first before worrying about OLV; awake intubation is always an option
  
  • Cook catheter exchange
  • alternatively, can use SLT with bronchial blocker

Question 17

Positioning keys for lateral decubitus position?

Answer 17

• Axillary roll under torso caudal to axilla to prevent compression of neurovascular bundle and forward rotation of humeral head
• hyper-abduction is prevented to keep brachial plexus from stretching
• pulse ox or frequent palpation of radial pulse to ensure integrity of circulation to dependent arm
• maintain head alignment to prevent compression jugular veins or vertebral arteries
  
  • this can decrease cerebral circulation
• typically induce in supine position
  
  • inducing in lateral position may be indicated with bronchiectasis or hemoptysis until lung isolation achieved
• when placed in lateral, can expect hypotension
  
  • everytime resposition check oxygenation, ventilation, hemodynamic, line, monitor, and potential nerve injuries
  • to minimize repositoning of tube, turn patients head, neck and endobronchial tube “en bloc” with patient thoracolumbar spine
• pay careful attention to airway devices for robotic surgery. access to airway very difficult in middle of surgery

Question 18

What are the ventilatory changes in lateral position?

Answer 18

V/Q Mismatch

• Awake and spontaneous breathing
  
  • Dependent (lower) lung is both better perfused and better ventilated, but lung volumes (FRC, VC, TV decrease)
  • abdominal content dipslace diaphragm in cephalad direction
  • dependent hemi-dieaphragm starts from high position, contraction of diaphragm leads to increased TV to fill dependent lung
  • V/Q unchanged when awake
• Anesthetized but spontaneous breathing
  
  • Nondependent lung better ventilated and dependent lung is better perfused (V/Q mismatch)
  • Anesthetized patient in the lateral position while the chest is not open and spontaneously breathing:
    
    • Dependent lung: decreased FRC, cephalad displacement of diaphragm by abdominal contents causes decreased FRC in dependent lung and decrease in zone 3. As the dependent lung’s FRC decreases, the volume and compliance also decreases.
    • FRC in nondependent (upper) lung - ventilation if preferentially distributed to nondependent lung, but blood flow is preferentially flowing to the dependent lung leading to a V/Q mismatch.
• Anesthetized, mechanically ventilated patient
  
  • Nondependent lung is overventilated and dependent lung is overperfused (worse V/Q mismatch)
  • Large decrease in FRC
  • Compression from abdominal viscera is no longer countered by force of contracting diaphragm.
  • Ventilation is greater in the nondependent lung due to a path of least resistance causing a V/Q mismatch
    
    • Add PEEP to help restore FRC & improve V/Q

Anesthetized open chest:

• Once the chest is opened, there is a decrease in the resistance of gas flow to the nondependent lung by detaching the lung from the pleural connection to the chest wall.
• Decrease in ventilation to dependent lung.
• Downward shift of mediastinum from loss of intrapleural pressure in nondependent lung.
• Decrease ventilation to the dependent lung from the downward compression of the mediastinum structures.
• Decreased CO & circulatory compromise.
• Positive pressure ventilation minimizes these effects.

Question 19

How do we prevent brachial plexus injury in the lateral position?

Factors that contribute to BP injury?

Answer 19

• Axillary roll b/t chest wall and the bed just caudal to the dependent axilla (never IN the axilla)
• Purpose: ensures weight of the thorax is borne by chest wall and to avoid compression on axillary neurovascular structures.
• ALWAYS check pulse in dep arm
• Never abduct more than 90 degrees, never extend posterior beyond neutral position, or anteriorly more than 90 degrees
• The brachial plexus is the site of the majority of intraoperative nerve injuries related to the lateral position.
  
  • • two varieties: the majority are _compression_ injuries of the brachial plexus of the _dependent_ arm
      
      • also a significant risk of _stretch_ injuries to the brachial plexus of the _nondependent_ arm
• Majority of nerve injuries resolve spontaneously over a period of months
• Traction injury of suprascapular nerve can cause deep, poorly circumscribed pain of posterior and lateral aspects of the shoulder.
  
  • ensuring vertebral alignment from side of table can help prevent the whiplash syndrome

Question 20

Head to toe assessment of patient in lateral position?

Answer 20

Question 21

Anesthetic technique for thoracic surgery?

Answer 21

• GETA with PPV is safest method of anesthetizing patients
• Inhaled Anesthetics (benefits)
  
  • Good Bronchdilators
  • Obtund A/W reflexes
  • Can be delivered with high O2 Concentrations
  • Cardiovascular stable
  • Rapidly eliminated
  • Preserve HPV at 1 MAC
• Intravenous Anesthetics
  
  • Hemodynamic stability
  • Does not diminish regional HPV
  • diminish the need for high volatile dosages

Question 22

Concerns for induction and maintenance thoracic anesthesia?

Answer 22

• Smooth Induction; Anticipate reactive airway!
  
  • Denitrogenate!
  • DLT: frequent bronchospasm trigger
  • Propofol or ketamine
• Inhaled Anesthetics; Judicious Opioids
  
  • Sevo may be the most potent bronchodilator
• Thoracic Epidural Anesthesia; Paravertebral blocks
• Minimize Nitrous Oxide (blebs; bullae)
• PPV with Muscle Relaxation
• Active warming
• Maintain adequate cardiac output
• Consider Dexmedetomidine infusion- improves oxygenation index and decreases shunt fraction in OLV
• The principles of anesthetic management are the same as they are for any asthmatic patient: avoid manipulation of the airway in a lightly anesthetized patient, use bronchodilating anesthetics, and avoid drugs that release histamine.

Question 23

Considerations for the administration of fluids in thoracic anesthesia?

Answer 23

• Fluid Administration
  
  • Prefer colloids vs crystalloids
• Due to hydrostatic effects, excessive fluids can cause increased shunting and pulmonary edema
• Recommend:
  
  • Fluid should be limited to < 3L/first 24hours
  • No fluid for third-space loss
    
    • May only give <1L fluid for entire VATS case

Question 24

When should you bolus a thoracic epidural in a thoracic case?

Precautions?

Answer 24

• Can use to compliment GETA
• Bolus with opioids, opioid and low concentration of local anesthesia
• Continuous infusion of opioid or opioid/local combination
• Post-op analgesia
• Monitor for hypotension if local used
  
  • May be exacerbated by volatile agent
• Consider bolus before incision. It really helps the intra-op and post-op pain. If you do not see a heart rate or pressure spike with incision, then your epidural bolus did well.

Question 25

Recommended anesthetic technique for induction and maintenance of thoracic case?

Answer 25

Induction

• Pre-oxygenate with 100% FIO2
• Narcotic vs. opioid sparing
• Induction agent
• Non-depolarizing muscle relaxant (no histamine release)
• Volatile agent and Lidocaine prior to intubation
• Intubate
• Position

Maintenance

• Inhaled anesthetic
• Opioid vs. opioid sparing
• Non-depolarizing muscle relaxant
• Controlled ventilation
• Extubation vs Tube change

Question 26

Postoperative anaglesia for thoracic case?

Guidelines for heparin and LWMH admin with epidural?

Answer 26

• Epidural analgesia – preferred technique
• Paravertebral blockade– block five interspaces: two above and two below plus at the site
• Parental Narcotics – use judiciously, PCA
• Ketorolac/ NSAIDs as a supplement
  
  • preferred to help with shoulder pain
• Other multimodal strategies- see previous slide
• Options: neuraxial blockade, paravertebral blocks, and antiinflammatories preferred to narcotic-based analgesia. However, only epidural techniques have been shown to consistently have the capability to decrease postthoracotomy respiratory complications in high-risk patients.2 Continuous paravertebral blockade may offer comparable analgesia with a lower rate of block failure and fewer side effects
• Epidural and heparin/ LMWH:** ASRA guidelines suggest an interval o**f 2 to 4 hours before or 1 hour after catheter placement for prophylactic heparin administration.** Low-molecular-weight heparin (LMWH) recommendations and precautions are: (**1) a minimal interval of 12 hours after low-dose LMWH and (2) 24 hours after higher-dose LMWH before catheter placement.

Question 27

Indication for OLV?

Answer 27

• Indication
  
  • selective atelectasis of the lung being operated on
  • Absolute*
    
    • Isolation to avoid spillage or contamination
    • Control of the distribution of ventilation
    • Unilateral bronchopulmonary lavage for pulmonary alveolar proteinosis
  • Relative
    
    • High vs. lower priority surgical exposure
    • Severe hypoxemia due to unilateral lung disease
• Separation via 3 methods
  
  • Double Lumen Tubes
  • Bronchial Blockers
    
    • More common in peds
  • Endobronchial Tubes
    
    • Least common
• Management
  
  • Operative lung CPAP
  • Non-operative PEEP
• Key point here is that one lung is not ventilated but is still perfused leading to a shunt

Question 28

What happens to flood flow distribution during OLV?

Answer 28

• Normal Blood Flow Distribution lateral decubitus position = 40:60 (NONDEP: dependent)
• OLV Blood Flow with HPV = 20:80 – a 50% HPV response
• 1 MAC ISO inhibits HPV by 21%
• Blood Flow 24:76 – INCREASE intrapulmonary shunt by 4%
• Causes a Right-to-Left Intrapulmonary Shunt
  
  • Decreased by HPV
• Check ABG before OLV and 20 minutes after initiating OLV
  
  • CO₂ elimination usually not affected if Ve (minute ventilation) is unchanged
  • Likely to see a transient fall in ETC02 and then rise as we correct minute ventilation of OLV
• Several inhaled—but not intravenous—anesthetics inhibit HPV in isolated lung preparations.
• Studies with no obvious changes in cardiac output indicated that isoflurane and halothane depress the HPV response by 50% at a minimum alveolar concentration (MAC) of 2

Question 29

What causes desaturation with OLV? How can we prevent this?

Answer 29

• Factors to correlate with increased risk for desaturation during OLV
  
  • High percentage of ventilation or perfusion to operative lung as seen on preoperative scan
    
    • During one-lung ventilation (OLV) for thoracotomy or thoracoscopy there is an obligate 20% to 30% shunt through the nonventilated lung.
    • If the operative lung has little perfusion preoperatively because of unilateral disease, the patient is unlikely to desaturate during OLV.
    • Finally, the degree of obstructive lung disease correlates in an inverse fashion with PaO2 during OLV. Other factors being equal, patients with more severe airflow limitation on preoperative spirometry tend to have a better PaO2 during OLV than patients with normal spirometry.
  • Poor Pa02 during 2-lung ventilation especially in the LDP*
    
    • >400 less likely to desat with OLV
    • <200, more likely to have trouble
  • Right-sided thoracotomy
    
    • Larger lung mass
    • In a series of patients, the mean PaO2 during left thoracotomy was approximately 70 mm Hg higher than during right thoracotomy
  • Normal preop spirometry or restrictive dx
  • Supine positon during one-lung ventilation
• Necessitates prophylactic measures
  
  • CPAP to non-ventilated lung (2-5cmH20)
  • PEEP to the ventilated lung
  • Or both

Question 30

Describe the various methods to achieve lung separation.

Answer 30

• Double Lumen Tubes
  
  • Lung separation technique of choice
  • Independent bilateral suctioning
  • Allows for CPAP
• Bronchial Blockers
  
  • Univent tubes
  • Fogarty embolectomy catheters
  • Easily added to Single lumen ETT
  • Easily added to patients with difficult AW or children
  • Decreased ability to suction
  • difficult to place in right lung d/t RUL anatomy
• Endobronchial Intubation
  
  • Easier placement in pts with difficult AW
  • Longer than ETT
  • Requires bronchoscopy for placement
  • Does not allow for CPAP
  • Decreased ability to suction

Question 31

How do you size for a DLT?

Answer 31

• Patient height is the best predictor of DLT size
  
  • Small (4’6”- 5’3”) – 35-37 FR
• Medium (5’3” – 5’7”) – 37 or 39 FR – most commonly used size
• Tall (> 5’7”) – 41 FR
• Proper size allows or 1-2 mm smaller than patients L bronchus to allow for space of bronchial cuff
• DLT: Males are usually 39F and Females 37F.
• Advantages of LEFT DLT: The right-sided DLT incorporates a modified cuff and slot on the endobronchial lumen that allows ventilation for the right upper lobe
• In adults, depth, measured at the teeth, for a properly positioned DLT, will be approximately 12 + (patient height/10) cm

Question 32

What sided DLT is more likely?

Answer 32

• Usually a Left sided DLT is used.
• Some reasons a Right DLT might be need (See table)
• The anatomic differences between the right and the left mainstem bronchus are reflected in the fundamentally different designs of the right-sided and left-sided DLTs.
  
  • the right mainstem bronchus is shorter than the left bronchus, and the right upper lobe bronchus originates at a distance of 1.5 to 2 cm from the carina,
    
    • techniques using right endobronchial intubation must take into account the location and potential for obstruction of the orifice of the right upper lobe bronchus.
    • The right-sided DLT incorporates a modified cuff and slot on the endobronchial lumen that allows ventilation for the right upper lobe.

Question 33

What are some characteristics of the DLT?

Answer 33

• The DLT is a bifurcated tube with both an endotracheal and an endobronchial lumen and can be used to achieve isolation of either the right or the left lung.
• Tracheal lumen and bronchial lumen (blue)
  
  • tracheal cuff
  • bronchial cuff is bright blue, low-volume, low-pressure endobronchial cuff for easier visualization during fiberoptic bronch
• newer tubes have build in camera and sensors for indirect CO measurement

Question 34

How do you place a DLT?

Answer 34

• Blind placement:
  
  • the DLT is passed by direct laryngoscopy
  • then turned 90 degrees counterclockwise (for a left-sided DLT placement) after the endobronchial cuff has passed beyond the vocal cords.
  • The DLT should pass the glottis without any resistance.
    
    • Seymour showed that the mean diameter of the cricoid ring is approximately the same as that of the left mainstem bronchus.
  • The optimal depth of insertion for a left-sided DLT is correlated with the patient’s height in average-sized adults.
    
    • In adults, depth, measured at the teeth for a properly positioned DLT, will be approximately 12 + (patient height/10) cm
• The direct vision technique
  
  • uses bronchoscopic guidance, in which the tip of the endobronchial lumen is guided into the correct bronchus after the DLT passes the vocal cords using direct vision with a flexible fiberoptic bronchoscope.
• An inadvertently deep insertion of a DLT can lead to serious complications, including rupture of the left mainstem bronchus.

Question 35

How can you verify correct positioning of DLT?

Answer 35

• Auscultation and bronchoscopy should both be used each time a DLT is placed and again when the patient is repositioned.
• Breath-by-breath monitoring of inspired and expired tidal volumes gives early warning of accidental changes in the intraoperative position of a DLT or air leaks during pulm rsx
• 1^ST View through tracheal lumen
  
  • Ensure no bronchial cuff herniation over the carina- should be 5- 10mm below carina
  • Identify the take-off of the RUL bronchus through the tracheal view (3 orifices)
• 2^nd View through bronchial lumen
  
  • Check patency
  • Check orifices of both the left upper and lower lobes
• Must have large hemostat or Kelly clamp in the room
• If lung deflation not achieved despite proper positioning, can place suction to expedite lung deflation
• The breath-by-breath monitoring of inspired and expired tidal volumes gives early warning of accidental changes in the intraoperative position of a DLT, with loss of lung isolation if the expired volume suddenly decreases (there is normally a 20- to 30-mL/ breath difference caused in part by the uptake of inspired oxygen).
• The development of a persistent end-expiratory flow during OLV, which correlates with the development of auto-PEEP, can be seen on the flow-volume loop.91 Also, the ability to accurately measure differences in inspiratory and expiratory tidal volumes is extremely useful in assessing and managing air leaks during and after pulmonary resections.

Question 36

What is the 3 step method for auscultation to confirm correct DLT placement?

Answer 36

A “3-step” method to confirm position of a left DLT by auscultation.

• Step 1, During bilateral ventilation, the tracheal cuff is inflated to the minimal volume that seals the air leak at the glottis. Auscultate to confirm bilateral ventilation.
• Step 2, The tracheal lumen of the DLT is clamped proximally (“clamp the short side short”) and the port distal to the clamp is opened.
  
  • During ventilation via the bronchial lumen, the bronchial cuff is inflated to the minimal volume that seals the air leak from the open tracheal lumen port. Auscultate to confirm correct unilateral ventilation.
    
    • only need 0.6-0.7 mL in bronchial cuff! Only use 3 cc syringe

Step 3, The tracheal lumen clamp is released and the port is closed. Auscultate to confirm resumption of bilateral breath sounds.

Question 37

Complication of DLT?

Answer 37

1. Most common: malpositioning
   
   • A malpositioned DLT will fail to allow collapse of the lung, causing gas trapping during positive-pressure ventilation, or it may partially collapse the ventilated or dependent lung, producing hypoxemia.
   • A common cause of malposition is
     
     • dislodgment of the endobronchial cuff because of overinflation,
     • surgical manipulation of the bronchus, or
     • extension of the head and neck during or after patient positioning.
2. AW trauma or rupture
   
   • Airway trauma can occur from an oversized DLT or when an undersized DLT migrates distally into the lobar bronchus and the main (i.e., tracheal) body of the DLT comes into the bronchus, producing lacerations or rupture of the airway.
   • Airway damage during the use of DLTs can present
     
     • as an unexpected air leak,
     • subcutaneous** emphysema**,
     • massive airway bleeding** into the lumen of the DLT, **or
     • protrusion of the endotracheal or endobronchial cuffs into the surgical field, with visualization of this by the surgeon.
   • If any of the aforementioned problems occur, a bronchoscopic examination and surgical repair should be performed.
3. Tension pneumothorax to ventilated lung during OLV

• *

Question 38

What is a bronchial blocker?

Answer 38

• Blockade of a mainstem bronchus or selective lobar collapse
• More frequent malposition than DLT
• Univent tubes
  
  • Single lumen endotracheal tubes with a BB channel
  • Slower lung collapse!
• Arndt (Cook); Fogarty Catheter
  
  • BB independent of single lumen tubes
• Used with patient with previous oral/neck sx
  
  • Awake SLT via nasal/oral then use BB
• Also used in patient with previous contralateral pulmonary resection
• Inclusion of the bronchial blocker or the distal wire loop of an Arndt blocker into the stapling line has been reported during a lobectomy117 and required surgical reexploration after unsuccessful removal of the bronchial blocker after extubation.
• To avoid these mishaps, communication with the surgical team regarding the presence of a bronchial blocker in the surgical side is crucial.
• Clearly, the bronchial blocker needs to be withdrawn a few centimeters before stapling.
• Another potentially dangerous complication with all bronchial blockers is that the inflated balloon may move and lodge above the carina or be accidentally inflated in the trachea. This leads to an inability to ventilate, hypoxia, and potentially cardiorespiratory arrest unless quickly recognized and the blocker deflated. There is a report of more malpositions with the use of bronchial blockers when compared to DLTs.

Question 39

How can you use a SLT for lung isolation?

Answer 39

• SLT or endobronchial tube that is advanced into the contralateral mainstem bronchus, protecting this lung while allowing collapse of the contralateral lung
• Rarely used:
  
  • difficult airways,
  • carinal resection,
  • previous pneumonectomy
  • Infants and small children
• Bronchoscope used for guidance.

Question 39

Describe the ventilatory management of OLV?

Answer 39

• Maintain two lung as long as possible
  
  • During the period of two-lung anesthesia before the start of OLV, atelectasis will develop in the dependent lung.
    
    • It is useful to perform a recruitment maneuver to the dependent lung (similar to a Valsalva maneuver, holding the lung at an end-inspiratory pressure of 20 cm H2O for 15–20 seconds) immediately after the start of OLV to decrease this atelectasis. Recruitment is important to maintain PaO2 levels during subsequent OLV
• TV (5-6 mL/kg of predicted body weight*)
• PEEP 5-10 cm H2O (caution in patients with severe obstructive disease)
• Respiratory rate (~12/min)to maintain PaCO2 between 35-40 mmHg
• Maintain PIP to <35 cm H20
• Plateau pressures <25 cmH20
• Remember it is harder to maintain Pa02 than PaCo2
• MUST have continuous monitoring of oxygenation and ventilation
• Denitrogenate- very important: The gas mixture in the nonventilated lung immediately before OLV has a significant effect on the speed of collapse of this lung.
  
  • Because of its low blood-gas solubility, nitrogen (or an air-oxygen mixture) will delay collapse of this lung
• Titrate FiO2
• A saturation>90% (PaO2 > 60 mm Hg) is commonly accepted (high 80’s for short intervals)
• Consider Pressure Control Ventilation (PCV) esp for patients at risk for lung injury
  
  • must watch the TVs closely as they can change suddenly
• With the use of intravenous anesthetic techniques or volatile anesthetics at less than or equal to 1–minimum alveolar concentration (MAC) doses, hypoxemia during one-lung ventilation (OLV) occurs infrequently. The use of continuous positive airway pressure (CPAP) or positive end-expiratory pressure (PEEP) as treatment for hypoxemia during OLV should be guided by the individual patient’s lung mechanics.
• The use of large tidal volumes during OLV (e.g., 10 mL/kg) can contribute to acute lung injury, particularly in patients at increased respiratory risk, such as after pneumonectomy.

Question 40

What are some causes of hypoxemia during OLV? How can we troubleshoot hypoxia in OLV?

Answer 40

Causes of Hypoxemia:

• Tube malposition
• Bronchospasm
• Decrease CO
• Hypoventilation
• Decrease FiO2
• Pneumothorax of dependent lung

Treatment of hypoxia in olv

• Check tube placement especially every position change with fiberoptic scope
• Increase FIO2 to 100%
• CPAP to nondependent, nonventilated lung (see notes)
• Perform a recruitment maneuver of the ventilated lung. To eliminate any atelectasis inflate the lung to 20 cm H2O or more for 15 to 20 seconds- watch for hypotension
• PEEP (5-10 cmH2O) to dependent, ventilated lung after recruitment
  
  • Recruits collapsed airways, Increase compliance, increase FRC
• Inform surgeon and go back to two lung ventilation
• Ligation of pulmonary artery in pneumonectomy patients
• Apneic oxygen insufflation to the nondependent lung.
  
  • Application of 3 liters of O2, via a suction catheter to the nonventilated lumen of the DLT
• ECMO as a last resort
• Significant desaturation (SpO2 < 90%) during OLV occurs in 1% to 10% of the surgical population in spite of a high FiO2
• CPAP with oxygen to the nonventilated lung is a reliable method to improve PaO2 during OLV.
  
  • CPAP should be applied to an inflated (recruited) lung to be completely effective.
  • The opening pressure of atelectatic lung regions is greater than 20 cm H2O and these units will not be recruited by simple application of CPAP levels of 5 to 10 cm H2O.
  • When CPAP is applied to an inflated lung, levels of CPAP as low as 1 to 2 cm H2O can be used.
  • Since the normal transpulmonary pressure of the lung at FRC is approximately 5 cm H2O, levels of 5 to 10 cm H2O CPAP applied to a fully recruited lung result in a large-volume lung that impedessurgery particularly during minimally invasive procedures.
  • Lower FiO2 levels of CPAP are of clinical benefit and can be titrated to the ventilated lung in patients at risk of oxygen toxicity using an air/oxygen blender.

Question 41

How do we re-expand the operative lung at the end of surgery?

Answer 41

• At completion, the surgeon will ask you to re-inflate the lung (while camera still in ideally)
  
  • May also test bronchial stump (20 cmH20 pressure in circuit so they can see leaks)
• Manually ventilate the patient up to 30 cm H20 until you see the lung re-inflated
• Place the patient back on your original ventilation settings because you are now ventilating both lungs.
• Chest Tube(s) will be inserted and the surgeon may want to know how much volume you are losing. If your tidal volume is set on 700 mLs and you are only getting back 400 mLs, you are obviously losing 300 mls.
  
  • This should improve when the chest tube(s) is connected to suction.

Question 42

Process for emergence and extubaiton during thoracic case? Guidelines for extubation?

Answer 42

Emergence and Extubation

• Inflate lung to ~30 cm H₂O pressure
  
  • to reinflate the atelectatic area and check for air leaks
• Check Chest Tube patency
  
  • Chest tube to water seal only
• Prompt extubation
  
  • if patient meets the necessary requirements and does not pose a risk for PPC
• Switch to a single lumen ETT
  
  • if needed for transfer to ICU
• After lung resection surgery, it is usually possible to wean and extubate patients with adequate predicted postoperative respiratory function in the operating room provided they are “AWaC” (alert, warm, and comfortable).

Tracheal Extubation

Criteria:

1. Hemodynamic Stability
2. RR not greater than 20-30/min (adult) with normal PaCO2
3. Adequate PaO2 (>60) with FiO2 < 40-50% and PEEP < 5-10
4. Adequate mentation (GCS >13)
5. *Acute phase of disease is resolved and adequate cough is present

Question 43

Complications of thoracotomy?

Answer 43

RESPIRATORY FAILURE

• Hemorrhage
• Vocal Cord Damage from the DLT insertion.
• Infection
• Trauma to surrounding organs.
• Pneumothorax
• EXTREMELY PAINFUL SURGERY

Question 44

Questions to ask yourself before thoracic procedure?

Answer 44

• Is OLV required/recommended? Is one method preferred to another?
• Any special monitoring considerations?
• How will the patient be positioned?
  
  • HPV worse in supine position
• Any major potential intra-operative or early postoperative complications (bleeding, etc.) anticipated?
• Postoperative management concerns:

e.g. should this patient remain intubated or is early extubation the goal?

Question 45

Anesthesia considerations during Mediastinoscopy

Answer 45

• Mediastinoscopy
  
  • is the standard method for the evaluation of mediastinal lymph nodes in the staging of NSCLC, to in the diagnosis of anterior/superior mediastinal masses, stage SCLC
• 2 to 3 cm is made in the midline of the lower neck in the suprasternal notch.
• mediastinoscope inserted toward the carina
• innominate artery immediately anterior to the mediastinoscope
  
  • worried about compression
• Anesthetic management of a patient with an anterior or superior mediastinal mass should be guided by the patient’s symptoms, the preoperative computed tomography (CT) scan, and the echocardiography findings.
• Compression to innominate artery can cause poor flow to right carotid artery
  
  • innominate artery supplies not only the right arm but also the right common carotid
  • Poor Cerebral perfusion results
• Central airway obstruction due to compression of the trachea may occur during induction of anesthesia or during the manipulation of the mediastinoscope near the trachea
• Technique: GA with ETT and Controlled Ventilation
  
  • Plan to extubate in the OR
• Monitor a-line/ pulse OX on right arm
  
  • if absent waveform ask surgeon to reposition mediastinoscope
• BP on left
• Morbidity related to mediastinoscopy ranges from 2% to 8%. The most severe complication of mediastinoscopy is major hemorrhage, which may require emergent thoracotomy. Other potential complications include airway obstruction, compression of the innominate artery, pneumothorax, paresis of the recurrent laryngeal, phrenic nerve injury, esophageal injury, chylothorax, and air embolism

Question 46

Complications of mediastinoscopy?

Answer 46

• Major complications include:
  
  1. Hemorrhage
  2. Pneumothorax
  3. RLN injury
     
     • can be permanent in ~50% of the cases
  4. Phrenic nerve injury/ Left Hemiparesis
  5. Esophageal injury
  6. Air embolism- risky if spontaneously beathing due to negative intrapulmonary pressure
     
     • Want controlled ventilation because negative pressure created during spontaneous ventilation can increase r/f air embolism
  7. Dysrhythmias
• When mediastinoscopy causes injury to the recurrent laryngeal nerve, it can be permanent in approximately 50% of the cases. If injury to the recurrent laryngeal nerve is suspected, the vocal cords should be visualized while the patient is spontaneously breathing. If the vocal cords do not move or are in a midline position, consideration has to be given to the problem of postoperative laryngeal obstruction.

Question 47

What is a VATS procedure? Why is it done?

Answer 47

• Video-assisted thoracoscopic surgery
• procedure of choice for the diagnosis and management of diseases of the pleura, nondiagnosed peripheral pulmonary nodules, and interstitial lung disease, lung biopsies, pleurectomies, and other various pulmonary disorders
• Thoracoscopic lobectomy is performed with a limited number of ports (one to three)
  
  • access incision of approximately 5 cm in length.
  • The advantage of the VATS technique is that the ribs are not spread
    
    • Less pain
  • commonly performed in the lateral decubitus position
• Thoracoscopic surgery can be performed under
  
  • local, regional, or general anesthesia with two-lung ventilation or OLV
• Patients with underlying lung disease have a decreased risk of respiratory complications when pulmonary resections are performed with video-assisted thoracoscopic surgery (VATS)
• VATS indications:

1. To biopsy suspicious lymph nodes or nodules on the lung or pleura.
2. To clean fluid or infectious tissues out of the pleural space.
3. Pulmonary resections.
4. Lobectomy for lung cancer.
5. To remove mediastinal masses.
6. To do a Sympathectomy.
7. To resect abnormal lung tissue for lung volume reduction surgery and many other thoracic procedures.

Question 48

Anesthetic technique for VATS? Advantages to VATS?

Answer 48

• Technique:
  
  • General Anesthesia with OLV placed in left main stem bronchus
  • Smooth IV induction and inhaled/ balanced anesthetic
  • A-line
  • Lateral decubitus position
• Advantages :
  
  • less post-op pain
  • shorter hospital stay
  • improved post-op pulmonary function
• Post-op paravertebral blocks
• Always possibility for conversion to open thoracotomy with massive bleeding

Question 49

What is empyema? Bronchopleural fistula?

Important considerations for empyema?

Answer 49

• Accumulation of pus in the pleural cavity
  
  • Leads to erosion of the bronchus and development of a bronchopleural fistula\
  • May be septic on presentation
  • Absolute Indication for Isolation of the infected lung with a DLT or a BB
  • Decortication in empyema may have massive blood loss
• Pt with BPF may present with subcutaneous emphysema, dyspnea, tracheal deviation, persistent air leak (note chest tube bubbles) and purulent drainage
  
  • Diagnosis made by bronchoscopy
  • Definitive operation of the bronchopleural fistula is closure of the fistula.

Question 50

What causes a bronchopleural fistula?

Intraop challenges?

If a lung is chronically collapsed, what are some considerations during lung re-expansion?

Answer 50

• A bronchopleural fistula may be caused by:
  
  • (1) rupture of a lung abscess, bronchus, bulla, cyst, or parenchymal tissue into the pleural space;
  • (2) the erosion of a bronchus by carcinoma or chronic inflammatory disease; or
  • (3) stump dehiscence of a bronchial suture line after pulmonary resection
• The underlying principle of management of a patient with a bronchopleural fistula is to secure lung isolation before positive pressure ventilation repositioning the patient for surgery.
• The patient with a bronchopleural fistula presents several intraoperative challenges for the anesthesiologist. These include:
  
  • (1) the need for lung isolation to protect healthy lung regions,
  • (2) the possibility of tension pneumothorax with positive-pressure ventilation, and
  • (3) the possibility of inadequate ventilation due to air leak from the fistula.
• Preoperatively, it is useful to estimate the loss of tidal volume through the bronchopleural fistula, which may be done in two ways.
  
  • First, one should determine whether air bubbles flow intermittently or continuously through the chest tube.
    
    • If air bubbles flow intermittently, then the fistula is small.
    • In contrast, when a patient has a large bronchopleural fistula or bronchial rupture, air will bubble continuously through the water-seal chamber of the chest-tube drainage system.
  • Second, the size of the bronchopleural fistula may be quantified by the difference between inhaled and exhaled tidal volumes.
    
    • In a nonintubated patient, this may be determined with a tight-fitting mask and a fast-responding spirometer.
    • In an intubated patient, it is determined by direct attachment of the spirometer to the ETT. The larger the air leak, the greater the need to isolate the bronchopleural fistula with the use of a lung isolation device (a DLT or an independent bronchial blocker).
• If the lung has been chronically collapsed, expansion should be done gradually to avoid the development of pulmonary edema upon reexpansion. Extubation in the operating room is encouraged if the patient meets standard criteria for extubation

Tracheal Resection

Question 51

Technique for tracheal resection?

Answer 51

• Surgical procedure for tracheal obstruction
• Technique
  
  • General anesthesia
  • Single lumen ETT tube place with fiberoptic bronchoscope
  • Tube placed beyond the obstruction if possible or placement of a catheter to ventilate via HFJV
    
    • TIVA needed
  • After repair ETT is placed and head is flexed.
  • Caution with ETT cuff : make sure it is not sutured during closure of trachea
• Post-op
  
  • Head of bed elevated and head and neck flexed to prevent tension of the suture line

Question 52

Considerations for mediastinal mass?

Answer 52

• Tumors of the mediastinum include thymoma, teratoma, lymphoma, cystic hygroma, bronchogenic cyst, and thyroid tumors
• Can cause obstruction of major airway or great vessels
  
  • Obstruction often distal to ETT
  • May be unable to forcibly pass ETT past obstruction
• A history of supine dyspnea or cough = possibility of airway obstruction upon induction of anesthesia
• MAINTAIN SPONTANEOUS VENTILATION until airway SECURED! (Awake intubation, inhalational induction or ketamine are options)
• Rigid bronch must be available and surgeon must be at bedside for induction
• ECMO is a rescue option with loss of AW

Question 53

Managmeent of esophageal surgery?

Answer 53

• Variety of approaches
  
  • Transthoracic Approach
    
    • Two-phase procedure:
      
      • 1^st phase: pts supine, creation of neoesophagus tube using stomach
      • 2^nd Phase: right sided thoracotomy in left lateral position, esophageal reconstruction through thoracic route
• Esophagectomy a major surgical procedure → a/w high M&M rates
• Management
  
  • similar to thoracotomy:
    
    • multimodal anesthetic management protocol using fluid restriction
    • early extubation
    • thoracic epidural analgesia
    • vasopressor/inotrope infusions to support blood pressure
• Very important to maintain bp for esophagogastric anastomosis
• Postop respiratory complications are very high

Question 54

Complications of thoracic surgery?

Answer 54

• Cardiac herniation
• Pulmonary torsion
• Hemorrhage
• Bronchial disruption
• Resp insufficiency
• Intra-op pulm edema
• R heart failure
• Neural injuries
  
  • Phrenic nerve
  • Vagus nerve
  • Recurrent laryngeal nerve
  • Spinal cord ischemia
• Pain is also an issue pot-op
• Shoulder Pain
• Ipsilateral shoulder pain is very common after thoracic surgery. It has been documented in 78% of patients immediately postoperatively.357 In 42% of patients this pain was judged to be clinically relevant.
  
  • By postoperative day 4, 32% of patients had shoulder pain, but only 7% had clinically relevant shoulder pain.
  • Shoulder pain occurred after both open and VATS surgery; the incidence may be decreased after VATS.
  • This pain was felt to be of two major types:
    
    • 1. Referred pain (55%). This is thought to originate from phrenic nerve afferent fibers and related to diaphragmatic or mediastinal irritation.
    • 2. Musculoskeletal (45%). This pain was associated with tenderness of the involved shoulder muscles and pain with movement.
      
      • Of the two types, the musculoskeletal pain was more intense and more difficult to treat.
  • Shoulder pain is not treated by any of the common regional blocks performed for thoracic surgery (e.g., thoracic epidural analgesia, paravertebral block). Shoulder pain is most responsive to antiinflammatories. Phrenic nerve infiltration and interscalene brachial plexus block358 have had some success but carry a risk of causing diaphragm dysfunction.
• Postthoracotomy Neuralgia and Chronic Incisional Pain In one prospective study, chronic postoperative pain at 6 months was documented in 33% of patients after thoracotomy and 25% after VATS.359
  
  • In this study, chronic pain was not associated with preoperative psychosocial measurements found to correlate with chronic postoperative pain in other types of surgery.
  • Chronic pain was associated with acute postoperative pain. This suggests that chronic pain after thoracic surgery may be partially preventable by intensive management of acute postoperative pain.