Exam 2 - Pulmonary CPB / Initiation-Termination / Charting

Question 1

3 layers of pulmonary linings

Answer 1

• Parietal Pleura
• Serous fluid
• Visceral Pleura

Question 2

Inspiration

Answer 2

• Lungs expand
• Negative pressure
• Air pulled in

Question 3

Expiration

Answer 3

• Diaphragm relaxes
• Lungs recoil
• Positive pressure
• Air pushed out

Question 4

Lung Characteristics

Answer 4

• Very elastic
• High surface tension
• Want to collapse
• Surfactant helps decrease surface tension
• Surface tension forces stronger on smaller alveoli

Question 5

Bronchial circulation

Answer 5

• high pressure / low flow
• 1-2% of CO
• Arteries branch off thoracic aorta
• Return venous blood to LA

Question 6

Pulmonary circulation

Answer 6

• Low pressure / high flow
• Deoxy blood to pulmonary caps
• Gas exchange
• Returns O2 blood to LA via pulmonary veins

Question 7

Lungs on CPB

Answer 7

• Stop ventilating and lungs collapse
• Resistance to flow INCREASES
• No pulmonary flow (bypassing)
• Little bronchial flow (due to resistance)
  - vessels are constricted because lungs collapsed

Question 8

Atelectasis

Answer 8

• Collapse of alveoli
• localized or entire lung
• Caused by: blockage of small bronchi w/ mucous
  Obstruction of major bronchus
• Easier to access R lung due to anatomy / more vertical and in-line
• Left side more prone to blockage

Question 9

Lungs post CPB

Answer 9

• Some atelectasis remains to variable degree
• Micro-atelectasis - not detectable clinically
• Can collapse entire lobe to degree
• CPB compromises pulmonary function
  - from days to months

Question 10

Pulmonary problems post CPB

Answer 10

• Atelectasis
• ARDS
• Highly variable for both
• Caused by atelectasis/pleural disruption (lifting)/impaired lung compliance/SIRAB (systemic inflammatory response after bypass)

Question 11

Atelectasis formation

Answer 11

• Air trapped in pulmonary caps
• creates negative pressure and subsequent collapse
• if can’t collapse (fibrosis)… build negative pressure
  - pulls fluid into alveoli….whole lung collapses

Question 12

How quick can atelectasis form

Answer 12

• 5-10 minutes after anesthesia
• anesthetized patient -> relaxed diaphragm
  - increase pleural pressure

Question 13

Resorption atelectasis

Answer 13

• Airway blocked
• low ventilation:perfusion ratio (Q:V ratio)
• normally equal

Question 14

Collapsed lungs during CPB due to no flow

Answer 14

• Re-expansion after CPB not always 100% successful
• Residual atelectasis
• cannula can push on lungs -> collapse
• back of lung collapses under own weight -> supine patient
• heart rests on top of lung -> collapse

Question 15

Prevention of atelectasis

Answer 15

• Cannot do much
• decrease compliment activation
• decrease chance of edema
• anesthesia has more control (inflation/deflation)

Question 16

Surfactant depletion

Answer 16

• anesthesia exposure reduces surfactant
• Lungs on CPB produce cytokines that drop surfactant synthesis
  
  • lungs hurt themselves on CPB

Question 17

Trauma of Lungs on CPB

Answer 17

• Suction can damage carina
• build up of secretions
• Promotes airway collapse
• careful when suctioning lungs

Question 18

What happens when cavity is open on CPB

Answer 18

• Blood / fluid can enter

- lung compresses

Question 19

Supine position on CPB

Answer 19

• decreases FRC (functional residual capacity)

- atelectasis observed in dorsal lung regions post CPB

Question 20

Most common lung complication of CPB

Answer 20

• Compress lung

- open cavity / supine position / IVC cannulation

Question 21

Pre-op risks of atelectasis

Answer 21

• smoking
• chronic bronchitis
• obesity
• cardiogenic pulmonary edema

Question 22

Intraoperative risks of atelectasis

Answer 22

• passive ventilation

- monotonous vent pattern

Question 23

Bypass risks of atelectasis

Answer 23

• surfactant inhibition

- distension / lung ischemia / compliment activation / open cavity / heart resting on left lobe

Question 24

Pump lung

Answer 24

• acute respiratory failure
• lungs congested
• interstitial / alveolar edema
• hemorrhagic atelectasis
• high [neutrophil]

Question 25

Causes of acute lung injury

Answer 25

• embolic load
• compliment activation
• hemodilution
• high pulmonary pressure -> high resistance

Question 26

Which patients benefit from OPCAB

Answer 26

• COPD
• Pulmonary problems
• Increased airway resistance

Question 27

Prevention of micro-emboli overload

Answer 27

• More filtration -> more normal the lungs

Question 28

CPB and pulmonary injury

Answer 28

• CPB -> compliment activation -> pulmonary injury

- hypoxia is not the problem -> still have bronchial circulation

Question 29

Acute bronchospasm on CPB

Answer 29

• Rare
• If on CPB….stay on
• If off CPB….get on

Question 30

Prevention / treatment of acute lung injury on CPB

Answer 30

• Heparin coated circuits
• increase biocompatibility
• limit neutrophil activation
• hemofiltration: Z-buff / MUF / hemoconcentrate
• Corticosteroids / prostaglandins / inhaled NO (more for transplants)

Question 31

Most common complication of lungs post CPB

Answer 31

• acute lung injury (atelectasis)
• common cause is mechanical ventilation
  
  • manipulation of pleura / retraction of lung
• Perfusionists can get rid of pro-inflammatory mediators