Case 12 - One lung ventilation Flashcards
Patient is going to undergo surgery for a lung tumor. what informatin regarding the lung tumor and surgery would you like to know?
1) symptoms the patient is experiencing
- arm pain - pancoast tumor
- swelling of ipsilateral head, neck, arm - SVC syndrome
- weakness - Lambert-Eaton syndrome
- dyspnea or SOB - compression of airway?
2) functional tumor (neuroendocrine secreting tumor)
- ACTH
- carcinoid
- phenochromocytoma
- lambert-eaton syndrome
3) Imaging studies
- location of tumor site
- is there compression of trachea or mainstem bronchi?
4) PFTs
* is obstructive airway disease reversible with bronchodilator?
5) predicted postop lung function
What is considered high risk surgery in terms of predicted pooperative lung function (PPO)?
Lung Mechanics
- PPO FEV1 < 40% - high risk
- RV/TLC > 50% - high risk
Gas Exhcnage
- diffusion capacity for CO (DLCO)
- PPO DLCO < 40% - high risk
Cardiopulm reserve
- VO2 max < 10 ml/kg/min - high risk
- decrease of SaO2 of 4% with exercise - high risk
- inability to climb more than 1 flight of stairs - high risk
**if still unsure, can do a split lung function test to allow calculation of PPO lung function**
when can pulse-oximetry become inaccurate or faulty?
- low perfusion states (dec CO) or shock
- excessive vasoconstriction (pressor therapy)
- intravascular dyes
- dyshemoglobins (CO, methoglobinemia)
- nail polishes
what are indications for one-lung ventilation
1) prevent contamination of good lung
- bleeding
- infection / pus spillage
2) Bronchopulmonary lavage
- protect other lung from saline administration
- do not want to drown both lungs at once
3) bronchopulmonary fistula
* all your TV going though fistula into pleural space
4) rupture bullae resulting in pneumothorax
* do not want all your TV going to ruptured lung
5) surgical exposure
- VATs
- pneumonectomy
- descending thoracoadmonial aortic aneurysm repair
What are the pros and cons of a bronchial blocker compared to a DLT?
PROS and CONS of bronchial blocker
Pros
- can be placed through single lumen tubes
- elminates need of changing from SLT to DLT in beginning of case
- avoids need of changing from DLT to SLT at end of case
Cons
-
more likely to dislodge than a DLT
-
especially if placed on right side
- right main stem has a small distance (1.5-2 cm)
- can occlude RUL, or fall back into trachea
-
especially if placed on right side
-
small lumen of bronchial blocker - takes longer to collapse lung
- deflate blocker and disconnect patient from anesthesia breathing circuit to faciliate lung collapse. followed by inflation of blocker and OLV
What are the advantages of a L-DLT over a R-DLT? Depending on the surgery, which one would you choose?
Airway anatomy
- L main stem is 5-6 cm in length
- R main stem is 1.5 - 2 cm in length
DLT
- R-DLT is more likely to accidentally occlude the RUL bonchus than a L-DLT
Which tube would you choose?
1) always choose L-DLT unless contraindicated
- in diseased left main stem bronchus
- if bronchus is part of surgical field
2) place DLT on side ipsilateral to pulmonary resection
- left side surgery = L-DLT
- right side surgery = R-DLT
- do not need to worry about obstruction of upper lobe bronchus because this side needs to be deflated anyway for surgical exposure
you finish surgery, and the upper lobe (LUL or RUL) does not re-inflate. What can you do?
anatomy
- R-DLT can occlude RUL
- L-DLT (with deep placement) can occlude LUL
Tx
- deflate bronchial cuff and ventilate through tracheal lumen
- withdraw tube so L-DLT is proximal to LUL or R-DLT side opening is aligned with RUL
- withdraw DLT into trachea and ventilate
what is the benefit of a large size DLT vs a small size DLT?
* choose the largest size DLT that an easily pass the glottis
Advantages of large DLT
-
less air required to inflate endobronchial tube cuff
- less air = less tissue pressure ischemia
- large lumen facilitates suctioning
- malposition of tube is less likely (stays in place)
How do you assess for correct position of DLT? (what are the different scenarois you can find when you first clamp tracheal lumen, and then clamp endobronchial lumen)
- place the DLT at a shallow distance
- inflate tracheal balloon and ventilate to verify DLT is in the airway and did not slip out
- use FOB to guide DLT into correct mainstem
Clamping the tracheal Lumen and ventilation through endobronchial lumen (both cuffs up)
1) unilateral breath sounds on correct side -> GOOD
2) b/l breath sounds -> DLT is proximal to carina
3) unilateral breath sounds in opposite bronchs -> DLT is on wrong side
Clamping endobronchial lumen, ventilating through tracheal lumen (both cuffs up)
1) unilateral breath sounds opposite the bronchus intended for intubation -> GOOD
2) difficult to ventilate/ unable to hear breath sounds
- –> Shallow - DLT is proximal carina and endobronchial cuff is blocking tracheal flow
- –> Deep - DLT is too deep, and tracheal lumen is abutted against carina or even in the same bronchi as the bronchial cuff
What are complications associated with lateral decubius position during thoracic surgery?
1) coughing, tachy, HTN while turning to lateral decub
2) v/q mismatching –> hypoxemia
- awake spont breathing
- better v/q of dependent lung: depenent blood flow + better diaphragm contraction of dependent lung (better ventilation)
- anesthesized and paralyzed
- ventilation better in non-dependent lung
- blood flow better in dependent lung
- v/q mismatch as a result
3) Down-lung syndrome
- transduation of fluid in dependent lung (gravity) -> interstital pulm edema.
- assoc with prolong position time + large amounts of IVF
4) brachial plexus injury (lying on axilla)
5) outter ear ischemia (pressure ischemia)
6) monocular blidnes (pressure ischemia)
why is there a V/Q mismatch, with resultant hypoxemia, in a patient that is anesthezied and paralyzed in a lateral decub position during two lung vent?
anesthesized + paralyzed in lateral decub: two lung
Overall - V/Q mismatch
- Better ventilation of non-dependent lung
- Better perfusion of depedent lung
Ventilation
-
ventilation is improved in non-dependent lung
- abdominal contents push up on diagraphm of dependent lung (dec compliance)
- downward pressure of mediastinum onto dependent lung (dec compliance)
- result = non-depn lung operates at a more compliant (steeper) portion of compliance (volume-pressure) curve
- dependent lung operates at a lower portion of compliance curve
Perfusion
- due to gravity, more blood flow to depenent lung
what happens to ventilatoin and perfusion in a patient that is anesthezied and paralyzed in a lateral decub position during OLV? Is there still an intrapulmonary shunt during OLV?
Anes + paraly in OLV
Overall:
- better ventilation of dependent lung
- better perfusion of depdent lung
Ventilation
- non-depedent lung clamped -> all gas flow enters dependent lung
Perfusion
- gravity dependent
- HPV initiated by alveolar hypoxia of non-depdent lung –> direct blood flow to ventilated (dependent lung)
Shunt
- alveolar hypoxia in non-dependent lung 2/2 atelectasis (lung collapse) is sensed and stimulates HPV
- still have some shunt, but HPV will reduce shunt by 50%, thus improving PaO2
-
PaCo2 is not affected
- diffuses readily across alveolar-capillary membrane in ventilated lung
What are anesthetic factors that can inhibit hypoxic pulmonary vasoconstriction, and therefore worsen intra-pulmonary shunt.
HPV
- occurs due to sensing low alveolar hypoxia
Factors Inhibiting HPV
- possibly potent inhaled anesthetics
- vasodilators (NTG, SNP)
- B2 adrenergic agonists (Isoproternol)
Factors that do not affect HPV
- opioids
- BZD
- Ketamine
During OLV, patient becomes hypoxemic. What will your management be for hypoxia during OLV?
Tx of Hypoxia during OLV
1) Notify Surgeon
2) FiO2 100%
- start at 100%, reduce as necessary to maintain SaO2
- bleoymycin - lowest Fio2 possible with adequate oxygenation 2/2 risk of O2 toxicity
3) Check Insp Pressure and BP
* listen for BS; Rule Out Pneumo and bronchospasm
4) recruitment maneuavers + PEEP 5-10 cm H2O
- helps return FRC to normal (prevent atelectasis)
- too much PEEP = bad -> will increase dependent lung PVR and divert flow away from good lung
5) Search causes of hypoxemia (machine to patient)
- kinking of circuit or DLT
- secretions
- DLT malposition
- pneumothorax or bronchospasm
- low CO (sepsis, anaphyl, PE, acute MI with CHF)
- hypoventilation (hypercarbia; A-a equation)
6) Add CPAP 5-10 cm H2O to nondendent lung
- open alveoli -> participate in gas exchange with blood flow that flows into non-depn lung
- Cannot do in VATs cases
7) clamp nondependent pulmonary Artery if accessable during sx
8) accept lower SaO2
What Tidal volumes will you use during OLV? Why will you need to provide PEEP?
OLV ventilation
- TV 5-8 mL/Kg to avoid barotrauma, volumtrauma, acute lung injury of the one lung
-
Add PEEP 5-10cm H2O
- low tidal volume associated with atelecatsis because airway pressure is low -> not enough pressure to open parts of lungs
- maintain PaCO2 around 40
- increase RR as needed
- Start at FiO2 100% and reduce to maintain adequate SaO2
