Mod XI - M&M25 - Miller66 - Thoracic:

Question 1

_{ANESTHESIA FOR THORACIC SURGERY}

Don’t forget to go over the reading assignment for additional procedures not covered in this lecture

Answer 1

M&M25 - Miller66

Question 2

_{ANESTHESIA FOR THORACIC SURGERY}

OBJECTIVES

Answer 2

• Describe indications, components, and preoperative assessment for thoracic surgeries
• Identify potential anesthetic and surgical complications
• State contraindications for OLV/DLT.
• Be able to identify mispositioning of DLT based on case scenarios
• Describe basic principles of postoperative pain management for thoracic surgery patients

Question 3

_{ANESTHESIA FOR THORACIC SURGERY}

lung isolation techniques have been in existence for as long as ET intubation itself - “Closed endobronchial anesthesia”, aka lung isolation technique, first performed in

Answer 3

1928

Question 4

_{ANESTHESIA FOR THORACIC SURGERY}

Closed endobronchial intubation, with the use of a bronchial blocker was 1st performed in

Answer 4

1936

Question 5

_{ANESTHESIA FOR THORACIC SURGERY}

First use of a double-lumen endotracheal tube (DLT) in

Answer 5

1950

DLT technology continuously evolving

Question 6

_{ANESTHESIA FOR THORACIC SURGERY}

DLT technology continuously evolving. However, what continues to be a its main concern?

Answer 6

Maintaining effective gas exchange in the face of ventilation perfusion mismatches

Question 7

_{ANESTHESIA FOR THORACIC SURGERY}

Two important anesthetic techniques for thoracic surgery

Answer 7

Lung isolation to facilitate surgical access within the thorax

Management of one-lung ventilation (OLV)

Question 8

_{ANESTHESIA FOR THORACIC SURGERY}

Benefits of OLV

Answer 8

Provides quiet surgical field

(This is very important in thoracoscopic surgeries)

Thoracic surgeons consider lung separation an absolute requirement for pulmonary surgery

Surgery can be performed on a lung while it’s being ventilated

Thoracic surgery alone is not an absolute indication for OLV

Question 9

_{ABSOLUTE AND RELATIVE INDICATIONS FOR OLV}

ABSOLUTE INDICATIONS FOR OLV

Answer 9

Lung isolation to prevent contamination/infection of health lung

Regulate distribution of ventilation to one lung

Unilateral lung lavage

Most common thoracic surgeries create relative indication for lung separation

Question 10

_{ABSOLUTE AND RELATIVE INDICATIONS FOR OLV}

RELATIVE INDICATIONS FOR OLV

Answer 10

Most common thoracic surgeries create relative indication for lung separation, in that they can safely accomplished without it

Surgical exposure for thoracic procedures- high Priority

^•TAA

^{•Pneumonectomy}

^{•Thoracoscopy}

^{•Upper lobectomy}

^{•Mediastinal exposure}

Surgical exposure-medium (lower) priority

^{•Middle and lower lobectomies & segmental resections}

^{•Esophageal resection}

^{•Procedures on the thoracic spine}

Severe hypoxemia r/t unilateral lung disease​

Question 11

METHODS OF LUNG ISOLATION

Answer 11

1.DOUBLE-LUMEN TUBES

^{•Bifurcated tube with both an endotracheal and an endobronchial lumen}

^{•Can be used to achieve isolation of either right or left lung}

2.SINGLE-LUMEN TUBES

^{•Tube is advanced into the contralateral mainstem bronchus for ventilation while the surgical side is collapsed}

3.BRONCHIAL BLOCKERS

^{•Blockade of a mainstem bronchus to allow lung collapse distal to the occlusion}

Question 12

_{METHODS OF LUNG ISOLATION}

What the most common type of lung isolation?

Answer 12

DOUBLE-LUMEN TUBES

• Bifurcated tube with both an endotracheal and an endobronchial lumen
• Can be used to achieve isolation of either right or left lung

Question 13

_{METHODS OF LUNG ISOLATION}

Placement options for Double-lumen tube (DLT)

Answer 13

1. Direct laryngoscopy
2. Via tube exchanger
3. Fiberoptically

Question 14

_{METHODS OF LUNG ISOLATION}

Advantages of Double-lumen tube (DLT)

Answer 14

Easy to place successfully
Repositioning rarely required
Bronchoscopy to isolated lung
Suction to isolated lung
CPAP easily added
Can alternate one-lung ventilation to either lung easily
Placement still possible if bronchoscopy not available
Best device for absolute lung isolation

Question 15

_{METHODS OF LUNG ISOLATION}

Disadvantages of Double-lumen tube (DLT)

Answer 15

Size selection more difficult
Difficult to place in patients with difficult airways or abnormal tracheas
Not optimal for postoperative ventilation
Potential laryngeal trauma
Potential bronchial trauma

Question 16

_{METHODS OF LUNG ISOLATION}

Placement options for Bronchial Blockers (BB)

Answer 16

1. Arndt
2. Cohen
3. Fuji
4. EZ Blocker

Question 17

_{METHODS OF LUNG ISOLATION}

Advantages of Bronchial Blockers (BB)

Answer 17

Size selection rarely an issue
Easily added to regular ETT
Allows ventilation during placement
Easier placement in patients with difficult airways and in children
Postoperative two-lung ventilation by withdrawing blocker
Selective lobar lung isolation possible
CPAP to isolated lung possible

(Often used when lung isolation requirements were not anticipated at the begining of the case; so rather than switching out for a DLT, the decision was made to place a BB)

Question 18

_{METHODS OF LUNG ISOLATION}

Disadvantages of Bronchial Blockers (BB)

Answer 18

More time needed for positioning
Repositioning needed more often
Bronchoscope essential for positioning
Limited right lung isolation due to RUL anatomy
Bronchoscopy to isolated lung impossible
Minimal suction to isolated lung
Difficult to alternate one-lung ventilation to either lung

(Also have a higher incidence for being dislodged when compared to DLT)

Question 19

_{METHODS OF LUNG ISOLATION}

Which lung isolation technique is used when a DLT is not an option?

A. BB

B. SLT

Answer 19

A. BB

(These are not commonly used in the clinical setting, but are used moe often than single lumen tubes (SLT) when a DLT is not an option)

Question 20

_{METHODS OF LUNG ISOLATION}

The final option for lung isolation is to use either an SLT or an endobronchial tube that is advanced into the contralateral mainstem bronchus, protecting this lung while allowing collapse of the lung on the side of surgery

Why is this technique rarely used today in adult practice (except in some cases of difficult airways, carinal resection, or after a pneumonectomy),

Answer 20

Limited access to the surgical lung for bronchoscopy, suctioning or CPAP

owing to the limited access to the nonventilated lung and the difficulty in positioning a standard SLT in the bronchus

Question 21

_{METHODS OF LUNG ISOLATION}

Advantages of Endobrochial tube

Answer 21

Like regular ETTs, easier placement in patients with difficult airways
Longer than regular ETT
Short cuff designed for lung isolation

Question 22

_{METHODS OF LUNG ISOLATION}

Disadvantages of Endobrochial tube

Answer 22

Bronchoscopy necessary for placement
Does not allow for bronchoscopy, suctioning, or CPAP to isolated lung
Difficult one-lung ventilation (right lung)

Question 23

_{METHODS OF LUNG ISOLATION}

Advantages of Endotracheal tube advanced into bronchus

Answer 23

Easier placement in patients with difficult airways

Question 24

_{METHODS OF LUNG ISOLATION}

Disadvantages of Endotracheal tube advanced into bronchus

Answer 24

Does not allow for bronchoscopy, suctioning, or CPAP to isolated lung
Cuff not designed for lung isolation
Extremely difficult right one-lung ventilation

Question 25

_{DOUBLE-LUMEN ENDOTRACHEAL TUBES} The DLT Consists of:

Answer 25

a single tube with two lumens Bronchial lumen (blue cuff) Tracheal lumen

Question 26

_{DOUBLE-LUMEN ENDOTRACHEAL TUBES} Bronchial lumen (blue cuff)

Answer 26

Longer than the tracheal lumen Designed to be inserted into the Right of Left main bronchus Used to ventilate the lung that it is inserted into

Question 27

_{DOUBLE-LUMEN ENDOTRACHEAL TUBES} Tracheal lumen

Answer 27

Terminates in the trachea (mid-trachea) Corresponding port will ventilate the opposite lung

Question 28

_{DOUBLE-LUMEN ENDOTRACHEAL TUBES} Why are Right and left DLT are manufactured?

Answer 28

DLT can be used to achieve isolation of either right or left lung

Question 29

_{DOUBLE-LUMEN ENDOTRACHEAL TUBES} What's the most widely used DLT?

Answer 29

Left DLT

Question 30

_{DOUBLE-LUMEN ENDOTRACHEAL TUBES} Sizing of DLT is determined by:

Answer 30

Patient’s **gender** and **height**

Question 31

_{DOUBLE-LUMEN ENDOTRACHEAL TUBES} Which DLT size is used for females? which size is used for males?

Answer 31

Females: 35-37 Males: 39-41

Question 32

_{DOUBLE-LUMEN ENDOTRACHEAL TUBES} What are the charateristics of internal vs external diameters of DLTs?

Answer 32

Internal diameter of DLT are reduced b/c of the double-lumen External diameters of DLT are large Size 37 Fr = 11 mm external diameter Smallest DLT 25 Fr = 7.5 mm external diameter

Question 33

_{DOUBLE-LUMEN ENDOTRACHEAL TUBES} Why are DLTs are not typically used in children?

Answer 33

**Large external diameters**

Question 34

_{DOUBLE-LUMEN ENDOTRACHEAL TUBES} Which method is suggested by some books to determine proper positioning/size of the DLT? Typically DLT size is simply based on:

Answer 34

CT-scan with a superimposed DLT to predict proper positioning/size This is actually never done in practice Typically DLT size is simply based on gender and height

Question 35

_{Comparative Diameters of Single- and Double-Lumen Tubes} How do external diameters of SLTs and DLTs compared? Why should DLTs never be advanced againts resistance?

Answer 35

Compared with SLTs, DLTs have a large external diameter This is why DLTs should not be advanced against significant resistance

Question 36

_{Selection of Double-Lumen Tube Size Based on Adult Patient—s Sex and Height} What the appropriate Size of Double-Lumen Tube (Fr) for Female \<160 (63 in)\* vs Female \>160 cm in height?

Answer 36

35 Fr. vs 37 Fr

Question 37

_{Selection of Double-Lumen Tube Size Based on Adult Patient—s Sex and Height} What the appropriate Size of Double-Lumen Tube (Fr) for Male \<170 (67 in)\* vs Male \>170 cm in height?

Answer 37

39 Fr. vs 41 Fr

Question 38

_{Comparative Diameters of Single- and Double-Lumen Tubes} Photograph of the cut cross sections of several SLTs and DLTs.

Answer 38

Note that: The external diameter of a 35-Fr DLT is larger than that of an 8.0-mm (internal diameter) SLT, and a 41-Fr DLT is larger than a 10-mm SLT.

Question 39

ANATOMIC CONSIDERATIONS Why are Right and left-sided DLTs designed differently?

Answer 39

To accommodate differences in bronchial anatomy between left and right side must be taken into acount Right side main bronchus is shorter than the left side Distance from carinal bifurcation to right upper lobe takeoff = 1.5-2 cm Distance from carinal bifurcation to left upper lobe takeoff = 4.5-5 cm

Question 40

ANATOMIC CONSIDERATIONS Which main bronchus is shorter?

Answer 40

Right side main bronchus is shorter than the left side Distance from carinal bifurcation to right upper lobe takeoff = 1.5-2 cm Distance from carinal bifurcation to left upper lobe takeoff = 4.5-5 cm

Question 41

ANATOMIC CONSIDERATIONS Right-sided DLTs are made to reduce the chance of obstruction of the orifice of the right upper lobe - Such differences include:

Answer 41

Modifications in the R DLT =\> slot in the endobronchial cuff for ventilation of right upper lobe Note view If FO scope is passed at the end of the endobrochial lumen Note view if FO scope is passed at the tracheal lumen

Question 42

_{RIGHT VERSUS LEFT SIDED DLT} PROS of the RIGHT SIDED DLT

Answer 42

Distorted anatomy of the entrance of left mainstem bronchus (tumor or TAA) Site of surgery involving left mainstem bronchus Left lung transplant, L-pneumonectomy

Question 43

_{RIGHT VERSUS LEFT SIDED DLT} CONS of the RIGHT SIDED DLT

Answer 43

More difficult to use More easily mispositioned Not stocked by many places to reduce the cost of purcahsing an item that is rarely used

Question 44

_{RIGHT VERSUS LEFT SIDED DLT} PROS of the LEFT SIDED DLT

Answer 44

**•Most commonly used** * Quickest/most successfully placed * Repositioning rarely required * Best for absolute lung separation * Large lumen easy for suctioning * Placement still possible w/o bronchoscopy

Question 45

_{RIGHT VERSUS LEFT SIDED DLT} CONS of the LEFT SIDED DLT

Answer 45

* Can be difficult to select proper size * Tear in tracheal cuff during intubation * Potential for laryngeal, tracheal, and bronchial injuries

Question 46

_{RIGHT VERSUS LEFT SIDED DLT} It is also typical to manage some cases that would require a Right side DLT w/ a Left side DLT - (e.g.

Answer 46

Left pneumonectomy In this case a Left DLT can be used, but it would to be removed prior to stappling the left maintsem bronchus

Question 47

_{LEFT SIDED DOUBLE-LUMEN TUBES} Blue cuff = ? lumen going where? Blue cuff volume? (mL)

Answer 47

Blue = Bronchial = B Bronchial cuff volume = ( 3 mL)

Question 48

_{LEFT SIDED DOUBLE-LUMEN TUBES} White cuff = ? lumen going where? White cuff volume ?(mL)

Answer 48

White cuff = portion of the tube that will sit in the trachea, just above the carina White cuff volume = 5 mL

Question 49

_{LEFT SIDED DOUBLE-LUMEN TUBES} Why is it important to never over inflate either of the cuffs (Bronchial vs tracheal cuffs?

Answer 49

**Cuff can rupture**, which reduces chances of maintaining OLV **Tissue corrosion** to surrounding the tube can occur

Question 50

_{LEFT SIDED DOUBLE-LUMEN TUBES} **Suction** can be placed in either of the lumens - for what purpose?

Answer 50

To help facilitate **collapse of the lung** during surgery ^{Suction that can be placed in either lumen to help facilitate complete lung collapse}

Question 51

_{LEFT SIDED DOUBLE-LUMEN TUBES} What the purpose of the **Connector**?

Answer 51

Connector that allows for **ventilation of both lungs together**

Question 52

_{PLACEMENT OF A DOUBLE-LUMEN TUBE} Describe inertion of the the DLT:

Answer 52

DLT is passed by direct laryngoscopy, with the stylet in place, just beyond the vocal cords DLT is advanced until endobronchial cuff has passed beyond the vocal cords Remove stylet and turn DLT 90 degrees counterclockwise (for a left-sided DLT placement) Finally, tube is advanced to appropriate depth or until resistance is met, which is usually around 27 to 29 cm at the lip

Question 53

_{PLACEMENT OF A DOUBLE-LUMEN TUBE} Representation of when the Remove stylet and turn DLT 90 degrees counterclockwise (for a left-sided DLT placement)

Answer 53

the Remove stylet and turn DLT 90 degrees counterclockwise (for a left-sided DLT placement)

Question 54

_{PLACEMENT OF A DOUBLE-LUMEN TUBE} Finally, tube is advanced to appropriate depth or until resistance is met, which is usually around 27 to 29 cm at the lip

Answer 54

Finally, tube is advanced to appropriate depth or until resistance is met, which is usually around 27 to 29 cm at the lip

Question 55

_{PLACEMENT OF A DOUBLE-LUMEN TUBE} Based on the Average anatomy of 170 cm patient, optimal depth strongly correlates with

Answer 55

**Patient’s height**

Question 56

_{PLACEMENT OF A DOUBLE-LUMEN TUBE​} As previously noted, the tube is typically inserted to 27 to 29 cm at the teeth/lip - Optional technique - The correct depth can also be calculated by:

Answer 56

Depth = (patient’s height/10) cm + 12

Question 57

_{PLACEMENT OF A DOUBLE-LUMEN TUBE​} What should you do if you meet resistance before the tube had reached the calculated depath?

Answer 57

If you ever meet resistance, you wanna stop advancing the tube You may not actually reach the correctly calculated depth before you meet Resistance

Question 58

_{PLACEMENT OF A DOUBLE-LUMEN TUBE​} Once the tube is in place you must check correct placement - During bilateral lung ventilation, the tracheal cuff is inflated, and auscultation should occur to

Answer 58

Confirm **bilateral ventilation**

Question 59

_{PLACEMENT OF A DOUBLE-LUMEN TUBE​​} Once bilateral breath sounds and chest rise are confirmed, the tracheal lumen is clamped, and the port distal to that clamp is opened The Bronchial cuff is then inflated and auscultation should occur

Answer 59

over the side of the lung being ventilated by the bronchial lumen In the case of this picture, no chest rise would be expected over the right side Chest rise and lung sounds would be expected over the left side

Question 60

_{PLACEMENT OF A DOUBLE-LUMEN TUBE​​} Auscultation alone should not be used to confirm placement of a DLT - What's more?

Answer 60

A fiber optic scope should be inserted into the tracheal lumen for inittial positioning, and for any subsequent time the pt's position changes

Question 61

_{PLACEMENT OF A DOUBLE-LUMEN TUBE​​} Through the tracheal view, the blue or bronchial cuff should not herniated out of the left bronchus, and it should be seen at

Answer 61

approximately 5 mm below the tracheal carina in the left bronchus

Question 62

_{PROBLEMS RELATED TO DOUBLE-LUMEN TUBES} The most commonly occuring problem with positioning of the of a DLT is

Answer 62

**Mispositioning**, whereby the tube is either Tip of tube Too proximal, Too distal, or Placed in the incorrect bronchus Any of these could be the reason why the intended lung is not collapsing Fiberoptic broncoscopy should be used to reconfirm and repostition the tube

Question 63

_{PROBLEMS RELATED TO DOUBLE-LUMEN TUBES} Any of the causes of malpositioning could be the reason why the intended lung is not collapsing - What should be used to reconfirm and repostition the tube?

Answer 63

**Fiberoptic broncoscopy**

Question 64

_{PROBLEMS RELATED TO DOUBLE-LUMEN TUBES​} Tracheal and bronchial injuries can occur, and is typically seen when

Answer 64

DLT is too small Undersized DLT migrates too distally than anticipated causing the main body of the DLT to be positioned into a bronchus

Question 65

_{PROBLEMS RELATED TO DOUBLE-LUMEN TUBES​} Hoarseness can occur with

Answer 65

Traumatic intubations Too large DLT causing pressure on surrounding tissue Movement of DLT with inflated cuffs

Question 66

_{BRONCHIAL BLOCKER PLACEMENT} OLV w/ a BB may be desired if DLT cannot be placed, eg. :

Answer 66

Previous oral or neck surgery Difficult intubation Anticipated need for mechanical ventilation post op May be used preferentially in patients with previous oral or neck surgery Used for patients with anticipated postoperative mechanical ventilation

Question 67

_{BRONCHIAL BLOCKER PLACEMENT} How are BB placed

Answer 67

Through a SLT, with the assistance of a bronchoscopy Blockade of a mainstem bronchus Collapse distal to the occlusion Requires the use of a bronchoscopy for correct placement

Question 68

_{VENTILATORY SETTINGS FOR OLV} What are the GOALS of mechanical ventilation for OLV?

Answer 68

Maintain adequate arterial oxygen saturation, Protect the lung, and Optimize surgical field for adequate visualization and manipulation

Question 69

_{VENTILATORY SETTINGS FOR OLV} •Tidal volumes, •Historically

Answer 69

Large TV used Thought behing 10-15 mL/kg of TV was that this will prevent atelectasis

Question 70

_{VENTILATORY SETTINGS FOR OLV} Now understood that high volume predispose the dependent lung to

Answer 70

Volutrauma Which causes the release of local mediators (cytokine inflammatory mediators) Could lead to Acute Lung Injury (ALI) It is now Recommended to keep TV 5-6 mL/kg

Question 71

_{VENTILATORY SETTINGS FOR OLV} It also recommended to keep Peak Inspiratory Pressures (PIP) \< 25 cm H2O - Peak airway pressures \> 40 cmH2O may contribute to:

Answer 71

**"Hyper-inflation injury"**

Question 72

_{VENTILATORY SETTINGS FOR OLV} It's important to determine An appropriate air-oxygen mixture - This value will vary from pt to pt - Be sure to leave room for “reserve” - why?

Answer 72

Some facilities will keep the pt at an FiO2 of 1.0 the entire procedure This can cause atelectasis, and eliminate the reserve intervention in the face of a declining oxygenation If FiO2 less than 1.0 is used, and the pt experiences hypoxemia, increasing the FiO2 to 1.0 would buy the practitionner time to plan another intervention However, if the FiO2 starts out at 1.0, there is no "reserve" Also, on 1.0 FiO2, by the time the SpO2 is falling, the insult that's causing the hypoxiawould be more advanced and the saturation will continue to decline during diagnosis and management of the issue

Question 73

_{VENTILATORY SETTINGS FOR OLV} Volume Control versus Pressure control

Answer 73

Pressure control will curtail sudden increases in PAP, however must watch for rapid changes in tidal volumes

Question 74

_{PHYSIOLOGY OF TWO-LUNG VENTILATION - AFFECT OF POSITION ON GAS EXCHANGE} Effect of positioning on ventilation - Pts are typically placed in which position for thoracic surgery?

Answer 74

**Lateral decubitus position** Gravitational effects on gas and blood flow =\> Result of differences in ventilation and perfusion in different lung segments

Question 75

_{PHYSIOLOGY OF TWO-LUNG VENTILATION - AFFECT OF POSITION ON GAS EXCHANGE} Normal V/Q ratio =

Answer 75

0.8 (ventilation 4L/min; perfusion 5L/min)

Question 76

_{PHYSIOLOGY OF TWO-LUNG VENTILATION - AFFECT OF POSITION ON GAS EXCHANGE} Position changes can result in changes in ventilation/perfusion, especially in the anesthetized and paralyzed pt When the anesthetized pt is placed in the lateral decubitus position, the ventilation/perfusion ration is

Answer 76

DECREASED V/Q ratio So there is physiologic shunting increased to 20-30% vs normal shunt = 3-5%

Question 77

_{PHYSIOLOGY OF TWO-LUNG VENTILATION - AFFECT OF POSITION ON GAS EXCHANGE} Why is V/Q ratio DECREASED in the lateral decubitus position?

Answer 77

Increased of the compliance of the Nondependent lung, It becomes easier to ventilate Aslo noted is decreased perfusion of the Nondependent lung The displacement of the relaxed diaphragm by abdominal viscera, and the downward gravity of the mediastinum result in DECREASED compliance of the Dependent lung Perfusion the Dependent lung is increased

Question 78

_{PHYSIOLOGY OF TWO-LUNG VENTILATION - AFFECT OF POSITION ON GAS EXCHANGE} Further reduction in movement of dependent hemithorax in lateral decubitus position d/t:

Answer 78

Utilization of bean bag or axillary roll

Question 79

_{PHYSIOLOGY OF TWO-LUNG VENTILATION - AFFECT OF POSITION ON GAS EXCHANGE} During Two-lung ventilation, when the pt is in the lateral decubitus position, the Distribution of blood flow between nondependent and dependent lung is:

Answer 79

**40%:60%**

Question 80

_{PHYSIOLOGY OF TWO-LUNG VENTILATION - AFFECT OF POSITION ON GAS EXCHANGE} When One-lung ventilation is initiated, lateral decubitus, the Distribution of blood flow between nondependent and dependent becomes:

Answer 80

**20%:80%**

Question 81

_{PHYSIOLOGY OF TWO-LUNG VENTILATION - AFFECT OF POSITION ON GAS EXCHANGE} During Two-lung ventilation, when the pt is in the lateral decubitus position, the Distribution of blood flow between nondependent and dependent lung is 40%:60% When One-lung ventilation is initiated, lateral decubitus, the Distribution of blood flow between nondependent and dependent is reduced to 20%:80% Why?

Answer 81

**Hypoxic pulmonary vasoconstriction (HPV)** HPV reduces blood flow to the non-dependent lung by 50% in an effort to reduce the physiologic shunting Without autoregulation of pulmonary blood flow, (aka without HPV), a large physiologic shunt of 40% would occur

Question 82

The Reflex intrapulmonary feedback mechanism that improves gas exchange and arterial oxygenation is known as:

Answer 82

HYPOXIC PULMONARY VASOCONSTRICTION (HPV) It is Present in most mammals

Question 83

_{HYPOXIC PULMONARY VASOCONSTRICTION (HPV)} In response to Hypoxia, normal tissue will vasodilate - With HPV, Alveolar hypoxia leads to:

Answer 83

Increased pulmonary vascular resistance (PVR) and vasoconstriction to reduce blood flow to nonventilated lung (non-dependent lung) This reduces perfusion during OLV Blood is then redirected towards the dependent, more perfused lung

Question 84

_{HYPOXIC PULMONARY VASOCONSTRICTION (HPV)} When is HPV initiated? When does its maximum effect occur? when does it return to baseline?

Answer 84

Within second of hypoxia Maximum effect after ~15 minutes May not return to baseline for several hours following prolonged OLV

Question 85

_{INHIBITION OF HYPOXIC PULMONARY VASOCONSTRICTION} Can be caused by:

Answer 85

**•Volatile anesthetics inhibit HPV in dose-dependent fashion** ^{•Higher doses = more inhibition •Halothane > Enflurane > Isoflurane •Doses < 1 MAC = weak inhibition of HPV •Nonventilated lung à reduced delivery of inhalational agents to alveoli àless inhibition of HPV} **•Vasodilators** ^{•Nitroglycerin, Nitroprusside, Phosphodiesterase inhibitors, beta blockers, calcium channel blockers} **•Nitrous Oxide** Very high/very low pulmonary artery pressures Hypocapnia = Vasodilation High mixed venous PaO2 ^{Also low PaO2, why?} Excessive PEEP Pulmonary infection Increased cardiac output

Question 86

_{INHIBITION OF HYPOXIC PULMONARY VASOCONSTRICTION} How do volatile anesthetics inhibit HPV

Answer 86

in dose-dependent fashion •Higher doses = more inhibition

Question 87

_{INHIBITION OF HYPOXIC PULMONARY VASOCONSTRICTION} Which volatile anesthetics inhibit HPV the most?

Answer 87

Older agents •Halothane \> Enflurane \> Isoflurane

Question 88

_{INHIBITION OF HYPOXIC PULMONARY VASOCONSTRICTION} How do Modern volatile anesthetics inhibit HPV?

Answer 88

At Doses \< 1 MAC = modern agents are weak inhibition of HPV Cause only a 4% increase in the shunt that would be expected with a normal HPV response •Nonventilated lung =\> reduced delivery of inhalational agents to alveoli àless inhibition of HPV

Question 89

_{INHIBITION OF HYPOXIC PULMONARY VASOCONSTRICTION} How do Vasodilators such as Nitroglycerin, Nitroprusside, etc affect HPV ^{(Phosphodiesterase inhibitors, beta blockers, calcium channel blockers)}

Answer 89

Can reduce HPV by causing the opposite effect Which is vasodilation in the non ventilated pulomonary vasculature

Question 90

_{INHIBITION OF HYPOXIC PULMONARY VASOCONSTRICTION} Why is Nitrous Oxide generally avoided?

Answer 90

Nitrous Oxide can cause an increase in PVR Which can either cause or exacerbate Pulm HTN, thus opposing HPV

Question 91

_{INHIBITION OF HYPOXIC PULMONARY VASOCONSTRICTION} Why does low PaO2 inhinbits HPV?

Answer 91

...

Question 92

_{INHIBITION OF HYPOXIC PULMONARY VASOCONSTRICTION} How to Very high/very low pulmonary artery pressures affect HPV?

Answer 92

Low PAP as in those seen with hypovolemic pts can trigger an adrenergic vasoconstriction, which reduces blood flow to the well ventilated lung Increase PAP will increase PVR, which will vasoconstrict the pulmonary vasculature, potentially reducing flow to ventilated lung and exacerbating hypoxemia

Question 93

_{INHIBITION OF HYPOXIC PULMONARY VASOCONSTRICTION} How does Hypocapnia affect HPV?

Answer 93

Hypocapnia causes vasodilation Hypocapnia causes reduced pulmonary vascular resistance and vasodilation, which oppose HPV

Question 94

_{INHIBITION OF HYPOXIC PULMONARY VASOCONSTRICTION} How does High PaO2 affect HPV?

Answer 94

High PaO2 can cause atelectasis which further induces hypoxemia

Question 95

_{INHIBITION OF HYPOXIC PULMONARY VASOCONSTRICTION} How does Excessive PEEP affect HPV?

Answer 95

Excessive PEEP can potentially reduce perfusion into well ventilated areas This can cause zone 1 ventilation/perfusion ratio, where more of the lung enters into a death space ventilatory pattern

Question 96

_{INHIBITION OF HYPOXIC PULMONARY VASOCONSTRICTION} How does Increased cardiac output inhibits HPV?

Answer 96

Increased cardiac output is an interesting inhibitor of HPV Thought to potentially recruit constricted vessels, thereby increasing the shunt

Question 97

_{HYPOXEMIA DURNG ONE-LUNG VENTILATION} Hypoxemia during OLV is defined as:

Answer 97

PaO2 \< 90% Acceptable saturation = \>90% Brief periods of saturation in high 80% acceptable in patients without significant comorbidities Lower acceptable saturations will be higher in pts with organs that are highly susceptible to hypoxemia, including those with CV or cerbrovascular disease

Question 98

_{HYPOXEMIA DURING ONE-LUNG VENTILATION} Hypoxemia is set to now occur in about what % of pts under OLV?

Answer 98

5-10%

Question 99

_{HYPOXEMIA DURING ONE-LUNG VENTILATION} Previously, hypoxemia occurred frequently, 20-30% of cases. Now 5% - Improvement is the result of:

Answer 99

Improvement in lung isolation Anesthetic agents Better understanding of the physiology behind OLV

Question 100

_{HYPOXEMIA DURING ONE-LUNG VENTILATION} What are anesthetic goals of OLV?

Answer 100

Maximize pulmonary vascular resistance in nonventilated lung (or non-dependent lung) while minimize PVR in ventilated or dependent lung Thinking about the physiology behind this will help you remember

Question 101

_{HYPOXEMIA DURING ONE-LUNG VENTILATION} First step if hypoxemia occur during OLV is to

Answer 101

Check for tube malpositioning A large portion of hypoxemic episodes are remedied by tube repositioning

Question 102

_{HYPOXEMIA DURING ONE-LUNG VENTILATION} Beside tube malpositioning, other causes of hypoxemia during OLV include:

Answer 102

Bronchospasm Decreased cardiac output Hypoventilation Low FiO2 Pneumothorax of dependent lung

Question 103

_{PREDICTION OF HYPOXEMIA DURING OLV} Factors That Correlate with an Increased Risk of Desaturation and hypoxemia During One-Lung Ventilation include:

Answer 103

1. High percentage of ventilation or perfusion to the operative lung on preoperative scan 2. Poor PaO2 during two-lung ventilation, particularly in the lateral position intraoperatively 3. Right-sided thoracotomy 4. Normal preoperative spirometry (FEV1 or FVC) or restrictive lung disease 5. Supine position during one-lung ventilation In these pts, it could be anticipated that prophylactic measures would need to be employed

Question 104

_{PREDICTION OF HYPOXEMIA DURING OLV} The most important predictor of hypoxemia during OLV is:

Answer 104

the PaO2 during Two-Lung Ventilation, specifically in the lateral position

Question 105

_{PREDICTION OF HYPOXEMIA DURING OLV} Normal preoperative spirometry (FEV1 or FVC) or restrictive lung disease

Answer 105

Perfusion scans and spirometry can be used to help predict the potential for hypoxemia during OLV Perfusion to the operative lung is inversely proportional to the physiologic shunting Pts with a lower FEV1 such as those with obstructive lung disease have be shown to experience less hypoxemia than pts with normal spirometry or pts with restrictive lung disease This is thought the be the result of intrincic or **auto-peep** that helps keep the pt airway patent during OLV

Question 106

_{PREDICTION OF HYPOXEMIA DURING OLV} Right sided thoracotomy are also a/w higher incidences of hypoxemia - why?

Answer 106

This is b/c the **right lung is larger** than the left, so perfusion is higher to the right

Question 107

_{PREDICTION OF HYPOXEMIA DURING OLV} Supine position with OLV has also been show to have less favorable outcomes than the lateral position - why?

Answer 107

This is d/t to the gravitational changes that occur with ventilation and perfusion

Question 108

Therapies for Desaturation during One-Lung Ventilation

Answer 108

Severe or precipitous desaturation: resume two-lung ventilation (if possible). Gradual desaturation Ensure that delivered FiO2 is 1.0. Check position of double-lumen tube or blocker with fiberoptic bronchoscopy. Ensure that cardiac output is optimal; decrease volatile anesthetics to \<1 MAC. Apply a recruitment maneuver to the ventilated lung (this will transiently make the hypoxemia worse). Apply PEEP 5 cm H2O to the ventilated lung (except in patients with emphysematous pathology). Apply CPAP 1-2 cm H2O to the nonventilated lung (apply a recruitment maneuver to this lung immediately before CPAP). Use intermittent reinflation of the nonventilated lung. Partial ventilation techniques of the nonventilated lung: Lung oxygen insufflation Lobar insufflation Lobar collapse (using a bronchial blocker) Use mechanical restriction of the blood flow to the nonventilated lung PEEP, positive end-expiratory pressure; CPAP, continuous positive airway pressure.

Question 109

_{Therapies for Desaturation during One-Lung Ventilation} Re-inflation of the non-ventilated lung can cause HPV to

Answer 109

be more effective HPV has a pre-conditionning effect HPV response to a second hypoxic challenge after re-expansion will be greater than the first