RE3: Chapter 27: Anesthesia for Thoracic Surgery Flashcards
What is FEV1 and what is normal?
A forced expiratory volume in 1 sec
Normal is > 2L
What are some post-op complications that can occur after lung resection?
Both cardiac and pulmonary complications such as dysrhythmias, myocardial infarction, PE, pneumonia, and empyema
**None of these complications can be predicted by preoperative studies of pulmonary function!
What is DLCO?
What is predictive of increased complications?
Lung carbon monoxide diffusing capacity
<40% = high risk
What is PPO FEV1?
Predicted Postop Function Test
Calculated by multiplying current FEV1 x Fraction of the functioning lung or the fraction of lung segments that will remain
What are factors that characterize average risk of postoperative complications?
FEV1 > 2L or 80% of predicted PPO FEV1 >80% of predicted PPO FEV1 + PPO DLCO both > 40% VO2max > 15mL/kg/min Ability to climb 3 flights of stairs
What are factors that characterize ELEVATED RISK of post-operative complications?
FEV1 <2L or < 40% of predicted PPO FEV1 < 40% of predicted PPO DLCO < 40% of predicted PPO product, (FEV1 x DLCO) < 1650 VO2max < 10mL/kg/min Inability to climb 1 flight of stairs Oxygen desat > 4% during exercise
In patients with high-risk cardiac disease, how many weeks should lung surgery be delayed to allow for off-bypass coronary revascularization?
6 weeks
*However with off-pump bypass coronary revascularization, the two procedures can be more easily performed in a single surgical encounter.
What are “The 4 M’s” to consider in lung cancer pts?
Mass effects
Metabolic effects
Metastases
Medications
What should there a high suspicion of with lung cancer patients?
Hormonal abnormalities (secretion of endocrine-like substances, Cushing disease, hypercalemia = poor prognosis, Lambert-Eaton myasthenia syndrome (LEMS).
What is the lung fxn testing: 80-40-15 rule?
- FEV1 and DLCO > 80% predicted = no additional testing; if < 80% or dyspnea present, diffusing capacity and post-op fxn should be predicted
- PPO FEV1 and DLCO < 40% predicted = increased risk; exercise testing should be evaluated
- VO2max < 15mL/kg/min = increased risk
What does a CXR show with COPD?
Hyperinflation
Increased AP diameter
Diaphragm flattening
*CRX does NOT provide abundant info regarding the degree of COPD
Pulmonary disease can cause what changes to the heart?
Right ventricular and atrial hypertrophy
What is the best initial tool for assessing pulmonary hypertension?
Echocardiography
Carbon dioxide (CO2) retention with an arterial partial pressure (PaCO2) greater than _______ is an indicator of poor ventilatory function.
45mmHg
What 2 things are predictive of increased complications following thoracic surgery?
Preoperative hypoxemia (SpO2 < 90%) Desaturation during exercise
Why is it important to assess pulmonary function tests after bronchodilators?
Because it would represent the patient’s lung function once optimized on medications
What is a valuable test for post resection lung function?
Split lung function test of ventilation and perfusion
What type of pulmonary disease are lung volume reduction surgery most useful in?
Heterogeneous emphysema (particularly when the emphysema is in the lobe being removed)
What area of the lung does removal not decrease overall lung function?
Lower lobectomy
It is appreciated more often with upper lobectomy rather than lower lobectomy.
What is diffusion capacity?
Tests the lung’s ability to allow transport of gas across the alveolar-capillary membrane.
What gas is used to measure diffusing capacity?
Carbon monoxide
How is diffusing capacity performed?
Pt inhales small amt of CO.
Holds breath for 10sec
Exhales
Amount of CO in exhaled breath is measured
After subtracting the amt of Co that should be expired with dead space air, the amt exhaled provides an indicator of the diffusion of gases in the lung.
What DLCO predicts increased complications?
< 40%
What is the predicted postop product?
DLCO x FEV1
What is VO2max?
Maximal oxygen consumption during exercise testing.
Strong predictor of outcomes
What is an VO2max indicator associated with increased mortality?
< 10mL/kg/min or 40% of predicted
What can be used to roughly estimate VO2max?
Patient’s physical ability to climb 5 flights of stairs = VO2 > 20mL/kg/min
*The inability to climb 1 flight of stairs suggests VO2 < 10mL/kg/min
Should advanced age be considered a contraindication for lung resection surgery?
NO
Smoking is another strong predictor of perioperative complications. When should a patient stop smoking before surgery?
8 weeks
Short term smoking cessation (less than 1 month) may increase mucous production
When should exercise testing be performed?
If PPO FEV1 and DLCO are < 40% of predicted normal
What leads help detect > 85% of ischemia?
Lead II and V5
What are the 5 steps of preoperative respiratory regimen?
- Stop smoking
- Dilate airways with drugs
- Losses secretions (hydration)
- Remove secretions (Chest PT, coughing)
- Increase patient participation (educate, cough, exercise, lose wt)
For a thoracotomy, what arm is preferred for an art line?
the dependent arm - more easily stabilized
What does an ART line placed in the RIGHT arm detect during mediastinoscopy?
Compression of the innominate artery and helps prevent a decrease in CBF
What other monitor would be helpful in detecting compression of the innominate artery?
Pulse ox on RIGHT hand
Why might a CVP be indicated for a thoracotomy?
Volume status is unclear
Fluid status shifts
What is associated with increased CVP?
Greater lung injury and prolonged ventilation post-op
Where should a subclavian puncture be done to monitor a CVP?
Same side as the planned thoracotomy to decrease risk of a pneumo with DLT
Are PAPs helpful in predicting postop complications or improve pt outcomes?
No. Studies have shown that right heart catheterization may PROMOTE cardiac complications.
What does PAP show?
An estimation of LV pressures with improvement of cardiac performance with fluids and CV drugs
Where do more than 90% of pulmonary artery catheters float?
Into the Right lung
What may alter the resistance in pulmonary artery vessels and reduce correlation between pulmonary artery occlusion pressure and LV pressure?
Lung pathology or HPV
What would a PAP show during a right thoracotomy?
The catheter will likely be in the nondependent, collapsed lung and give a false low reading for CO. (Be sure the PAP is not situated in a vessel that will be clamped during resection)
Where is an Axillary roll placed in the lateral decubitus position?
It is placed beneath the torso just CAUDAL to the axilla to prevent compression of the neurovascular bundle and forward rotation of the humeral head.
In the spontaneously breathing, upright patient, explain lung perfusion and ventilation.
Perfusion increases from apex to base. Flow reaches very low rates in the apex and is greatest in the base
Ventilation also increases from apex to base.
*However, the increase in both ventilation and perfusion from apex to base is NOT PARALLEL
Where are pleural pressures most negative in the upright patient?
At the apex of the lung and keeps the alveoli distended. The dependent alveoli are less distended = more compliant. Therefore, most of a tidal breath is distributed to the dependent alveoli!
Where is gas exchange more efficient in the upright, spontaneous breathing patient?
The dependent lung
Where in the awake lateral patient is perfusion and ventilation the greatest?
Perfusion is greatest in the dependent lung (dependent on gravity)
Ventilation is greatest in the dependent lung (due to contraction of the diaphragm causes more tidal volume to fill the dependent lung)
What is zone 1 in the upright lung?
PA > Pa > Pv (NO FLOW)
Collapsible vessels are held closed and no flow occurs (alveolar dead space)
What is zone 2 in the upright lung?
Pa > PA > Pv (SOME FLOW) (Arterial exceeds alveolar pressure, but alveolar exceeds venous)
Constriction occurs at downstream end of each collapsible vessel and the pressure inside the vessel at this point = alveolar pressure, so the pressure gradient causes flow arterial to alveolar. Gradient increases with distance down the lung = increased blood flow.
What is zone 3 in the upright lung?
Pa > Pv > PA (LOTS OF BLOOD FLOW) (Venous exceeds alveolar pressure)
Collapsible vessels are held open. Flow is arterial-venous and constant perfusion of alveoli.
How much does pleural pressure (Ppl) increase per cm of lung dependency in the upright lung?
Pleural pressure increases 0.25cm H2O per cm of lung dependency.
Where on the compliance curve are small/dependent alveoli in the upright lung?
On the steep portion - therefore more ventilation is delivered to the dependent alveoli.
What does the upright lung regional slope on the compliance curve equal?
Regional compliance
In the awake lateral patient, the small dependent alveoli lie where on the compliance curve?
On the steep portion (same as in the upright position)
In the awake lateral position, what part of the lung lies on the flat portion of the compliance curve and what part of the lung lies on the steep portion of the compliance curve?
Nondependent lung lies on the flat portion of the curve
Dependent lung lies on the steep portion of the curve (greatest perfusion and greatest compliance)
What happens to the FRC with induction of anesthesia?
FRC decreases.
Cephalon displacement of the diaphragm with abd contents causes a further decrease in FRC
What zone is affected by the decrease in FRC with anesthesia?
Zone 3 is reduced!
In the anesthetized patient, where on the compliance curve is the nondependent and dependent lung?
Nondependent lung is MORE COMPLIANT and shifts down to the STEEPER portion of the curve.
Dependent lung is LESS COMPLIANT and shifts down to the FLATTER portion of the curve.
In the lateral anesthetized patient, where is the ventilation preferentially distributed?
To the non-dependent lung
In the lateral anesthetized patient, where is the blood flow preferentially distributed?
To the dependent lung (gravity)
On the anesthetized, paralyzed, lateral patient, what further happens to the FRC?
FRC further declines b/c of abd contents
Where is ventilation favored in the anesthetized, paralyzed lateral patient?
Non-dependent lung and V/Q mismatch worsens
What can be done to help restore FRC on the anesthetized, paralyzed lateral patient?
Add PEEP
With the anesthetized, open chest, lateral patient, where is ventilation the best?
Non-dependent lung (reduced resistance to the non-dependent lung by detaching the lung from its pleural connection with the chest wall and mediastinum also shifts downward b/c of loss of negative intrapleural pressure in the non-dependent lung, which helps to distend it.)
What paradoxical respiration in the anesthetized, open chest patient cause?
Compromises fresh gas exchange in the dependent lung as the VT moves to and fro between the lungs
What can be done to diminish the effects of mediastinal shift and paradoxical respirations?
Positive pressure ventilation
What is the less ventilated/better perfused dependent lung contribute to in the lateral one lung ventilation pt?
Physiologic shunt because blood flows through atelectatic areas without acquiring O2.
What position exhibits the most significant regional areas of disparity between V and Q?
The lateral, anesthetized, paralyzed, open chest patient
In the anesthetized open-chest, OLV, any perfusion to the nondependent lung creates a shunt, but HPV reduces the shunt by _____% by diverting much of that blood towards the dependent lung.
50%
What are ABSOLUTE indicators for OLV?
- Isolation of one lung to avoid spillage or contamination/infection/massive hemorrhage
- Control of the distribution of ventilation
- Unilateral bronchopulmonary lavage
What are RELATIVE indicators of OLV?
- Surgical exposure
- Post CPB/pulmonary edema/hemorrhage after removal of totally occlude get unilateral PE
- Severe hypoxemia related to unilateral lung disease
What are the 3 types of DLTs?
Carlens
White
Robert Shaw
How is the DLT size determined?
Most commonly sized for females and males?
Sizing of DLTs are determined by the patient height
Females: 34F-37F
Males: 39F-41F
What is more commonly used in practice, right or left-sided DLTs?
Left-sided DLTs are more common and can be used for right and left thoracotomies.
What is the most common complication of DLT use?
Malpositioning of the tube
Additional complications include damage to the VCs or arytenoid cartilage, bronchial rupture, delivering entire TV to one lung = barotrauma, rupture of thoracic aneurysm
What are some contraindications for the use of DLTs?
Internal lesions of the trachea of main bronchi
Compression of the trachea of main bronchi by an external mass
Descending thoracic aortic aneurysm
Difficult airway
How much air is placed in the tracheal cuff? In the bronchial cuff?
Tracheal cuff 5-10ml
Bronchial cuff 1-2ml
How do you insert a DLT?
A lubricated DLT is advanced with the distal curve concave anteriorly until the VCs are passed.
Stylet is removed
Tube is then rotated 90 degrees TOWARDS the bronchus to be intubated.
Tube is advanced to approx 27cm in females and 29cm in males or until resistance is met.
What is the best way to verify placement of a DLT?
Flexible FO bronchoscopy
Insert scope into tracheal lumen to visualize carina and endobronchial cuff (1-2mm beyond the carina)
Insert scope into the bronchial lumen to visualize if the tip is obstructed.
For left-sided, visualize the LUL bronchus distal to the tube tip
For right-sided, visualize the RUL bronchus is aligned with ventilation port
Why should the DLT be verified by bronchoscopy after the patient is positioned laterally?
DLT will commonly withdraw from bronchus by 1 cm
If a DLT is too far on the left side, what breath sounds are heard?
Both bronchial and tracheal lumen, only the LEFT is heard
If DLT is too far on the RIGHT side, what BS are heard?
Bronchial lumen - BS in the right middle and lower lobes
Tracheal lumen - BS in the left lung or right upper lobe (depending on depth of tracheal cuff)
What is a bronchial blocker(BB)?
BB consist of catheters with an inflatable balloon that blocks the bronchus of the operative lung and are guided into the appropriate bronchus with the aid of a bronchoscope.
What are some advantages and disadvantages of BB?
Advantages: more useful in patients with difficult airways, beneficial for pts already intubated, used in pediatric lung separation
Disadvantages: requires more time to position, greater incidence of becoming malpositioned, no suctioned through BB
What is HPV?
Hypoxic pulmonary vasoconstriction (HPV) is a mechanism that increases vascular resistance in hypoxia areas of the lungs and this diverts some blood flow to areas of better ventilation and oxygenation. With OLV, the blood is shunted from the non-ventilated lung to the ventilated lung.
When the left lung is the non-dependent lung, what is the distribution of blood flow between the non-dependent and dependent lungs?
35% : 65%
When the right lung is the non-dependent lung, what is the distribution of blood flow between the non-dependent and dependent lungs?
45% : 55%
What is the average OLV blood flow distribution between the non-dependent and dependent ratio?
40% : 60%
What are factors that reduce the effectiveness of HPV?
Alkalosis Excessive TV or PEEP Hemodilution Hypervolemia Hypocapnia Hypothermia Prostacyclin Shunt fxn < 20% or > 80% Vasodilators, phosphodieserase inhibitors and calcium channel blockers Volatile anesthetics > 1.5MAC
Overdistension of alveoli may reduce perfusion to well-ventilated lung areas by creating what?
Zone 1
What % can HPV decrease the shunt fraction during OLV?
50%
What triggers HPV?
Alveolar hypoxia (NOT arterial hypoxemia)
What analgesic options are best indicated for thoracotomies?
- Thoracic epidural is one of the most effective methods (placed around T6 to T8)
- Paravertebral blocks placed at level of incision plus one or two intercostal interspace so above and below
What ventilation modes are best utilized in one-lung ventilation?
- TV (6mL/kg on the left and 8mL/kg on the right)
- Adding PEEP
- Limiting PIP < 25cm H2O
- Allowing permissive hypercapnia (PaCo2 maintained below 60-80)
- Alveolar recruitment
- FiO2 should be maintained at the lowest level to support adequate SpO2
What can be done to improve PaO2 during OLV?
- First, always check positioning of the DLT!
- CPAP to nondependent lung / non-ventilated lung (Mapleson C)
- Deliver low flow O2 through a small catheter to the nondependent lung
- Add PEEP to dependent lung
- Use PC setting
- Intermittent reinflation of the nondependent lung
- Early ligation of PA will improve oxygenation
What should be done with discontinuing OLV?
Deflate bronchial cuff following lung reexpansion
Slow breaths achieving PIPs 30-40cm H20
What are the “4 T’s”?
Thymoma
Thyroid
Teratoma
“Terrible” Lymphoma
What is the goal in managing tumors of the anterior mediastinum?
Maintenance of spontaneous ventilation
Avoid GA
What are S/S of mediastinal mass?
Asymptomatic or characterized by vague signs such as dyspnea, cough, hoarseness or chest pain. Wheezing may be present and symptoms may be positional.
What should be done in the case of mediastinal mass requiring placement of ETT?
Awake FOI and place the ETT beyond obstruction while maintaining spontaneous ventilation.
Why would the use of helium/O2 mixture be beneficial with mediastinal masses?
Low density gas decreases turbulence past the stenotic area improving the flow and decrease WOB
How should patients with vessel involvement be treated?
Receive only local anesthesia, remain in the sitting position and maintain spontaneous ventilation. CPB must be on standby.
What are s/s of SVC syndrome?
Venous engorgement of the upper body caused by compression of the SVC.
S/S include: dilation of collateral veins of the upper part of the thorax and neck, edema and rubor of the face, neck and upper torso and airway, edema of the conjunctiva with or without proposes, SOB, headache, visual distortion or altered meditation
Where should IV lines be place in a patient with SVC syndrome?
Lower extremities (insertion above the SVC could delay the drug effect as a result of slow distribution)
What is a mediastinoscopy?
It involves passing a scope into the mediastinum via an incision above the sternal notch. The scope is passed anterior to the trachea.
What are complications of a mediastinoscopy?
Pneumothorax Hemorrhage resulting from tearing of major vessels Arrhythmias Bronchospasm Recurrent nerve palsy Laceration of the trachea or esophagus Chylothorax
What is a Bullae?
Air filled spaces of the lung tissue resulting from the destruction of alveolar tissues and consolidation of alveoli into large pockets.
Increases in size with PPV
During GA, how can you reduce the risk of rupture of bullae?
Spontaneous ventilation maintained until chest is opened
What vent settings are recommended for removal of bullae?
Small TV
High RR
High FiO2 with low PIPs 10-20cm H2O or jet ventilation
What should be avoided with bullae?
N20
What nerves are vulnerable to damage following thoracic surgery?
Phrenic
Left RLN
Spinal cord
How much CT drainage necessitates surgical reexploration?
Generally, blood entering the pleural space drains into CT at a rate of less than 500mL/day. CT drainage > 200mL/her needs surgical exploration.
Are dysrhythmias common after thoracic surgery?
What can you do to prevent them?
Yes, Supraventricular dysrhythmias are relatively common
Prevent with Beta-blockers and don’t fluid overload
