Anesthesia for Thoracic Surgery Flashcards
What are major challenges in thoracic surgery?
Physiologic derangements caused by lateral position
Open pneumothorax
Surgical manipulation, interfering with heart/lung function
Risk of rapid, massive blood loss
Necessity for one lung ventilation
How does the lateral position alter normal lung physiology?
Disrupts ventilation/perfusion relationships
In addition to the lateral position, what other factors affect Q/V in thoracic surgery?
Anesthesia, NMBA, opening the chest and surgical retraction
What causes HoTN in the lateral position?
Blood pooling in dependent portions
What nerve injuries can occur in the lateral position?
Brachial plexus and peroneal nerve injuries
What injuries to the body can be caused by the lateral position?
Outer ear ischemia
Axillary artery compression
Monocular blindness
In an upright patient spontaneously breathing with a closed chest, where does maximal ventilation occur?
At the base of the lungs
Where does the most perfusion occur in an upright, spontaneously breathing closed chest patient?
Also favors the bases of the lungs, V/Q matching is preserved
What alveoli of the lungs are the most compliant?
Base alveoli more compliant, they can expand for a greater volume for a given pressure change
How is V/Q matching preserved in a spontaneously breathing patient with a closed chest in the lateral position?
Dependent lung receives more ventilation and perfusion than the upper lung (non dependent)
Gravity provides more perfusion and lower diaphragm on the dependent lung able to contract more efficiently during spontaneous respirations, more TV
What factors further press the diaphragm cephalad?
Supine position
Induction of anesthesia
Paralysis
Surgical position and displacement
What V/Q mis-match occurs in the anesthetized and paralyzed patient in the lateral position with a closed chest?
The dependent lung receives more perfusion while the non dependent lung receives more ventilation
What intervention can help restore V/Q in the paralyzed and anesthetized patient in the lateral position with a closed chest?
PEEP, restores ventilation to the dependent lung to a steeper more favorable portion of the pressure volume curve
Why does V/Q mismatch occur when the anesthetized patient is in the lateral position with an open chest?
Perfusion remains greater in the dependent lung but the upper lung collapse leads to progressive hypoxemia
What can be seen in the anesthetized patient in the lateral position with an OPEN chest without paralysis?
Mediastinal shift and Paradoxical respirations
What causes paradoxical breathing in the anesthetized patient in the lateral position with an OPEN chest without paralysis?
To and Fro gas exchange between the non-dependent lung and the dependent lung
Why does positive pressure ventilation make V/Q worse in the anesthetized and paralyzed patient in the lateral position with an OPEN chest?
Controlled PPV favors the upper lung, more compliant, paralytic further enhances this by allowing the abdominal contents to rise further up on the dependent diaphragm and impede ventilation
What is hypoxic pulmonary vasoconstriction?
Diverts blood away from the hypoxic regions of the lung, helps improve arterial oxygen content, improving hypoxia
What is the blood flow distribution in two lung ventilation when the left lung is non dependent?
Non dependent 35%
Dependent 65%
What is the blood flow distribution in two lung ventilation when the right lung is non dependent?
Non dependent 45%
Dependent 55%
What is the average of both lungs being nondependent?
Non dependent 40%
Dependent 60%
How does HPV affect average of blood flow to the non dependent and dependent lungs during one lung ventilation?
Non dependent 40% –> 20%
Dependent 60% –> 80%
How much shunt is normally present during two lung ventilation in the lateral position?
10% –> assumed to be distributed equally 5% each lung
What factors inhibit HPV?
High pulmonary vascular resistance Hypocapnia High or very low mixed venous PO2 Vasodilators Pulmonary infection Inhaled anesthetics
How much does 1 MAC increase pulmonary shunt?
1 MAC = 4% increase in shunt
What factors send blood to the dependent lung?
Gravity
Surgical interference
HPV
What five factors cause interference in ventilating the dependent lung?
GA Paralysis Circumferential compression 100% O2 (absorption atelectasis) Difficulty removing secretions
What are the benefits of one lung ventilation?
Surgical exposure, access to aorta and esophagus, prevents cross contamination and prevents loss of anesthetic gases with bronchopleural fistula
What are relative contraindications for one lung ventilation?
Difficult airway with poor visualization of the larynx
Lesion in bronchial airway precluding bronchial intubation
What techniques can be used to achieve one lung ventilation?
Double lumen ETT Bronchial blocker (used with single lumen ETT)
Where does the trachea begin in the adult?
C6 (11-12cm long)
What are important characteristics of the right bronchus?
Wider
Diverges away from the trachea at a 20-25 degree angle
Orifice of the RUL sits only 1-2cm to carina
What are important characteristics of the left bronchus?
Narrower than right
Diverges away from trachea at 40-45 degree angle
Orifice of LUL sits about 5cm distal to carina
When using a fiberoptic scope, how can the provider tell the right from the left bronchus?
The provider can see three lumens inside right bronchus
Anterior bronchus
Posterior bronchus
Apical bronchus
Why is it common practice to place a left sided double lumen tube?
When placing a right sided DLT often occludes RUL and can cause atelectasis
What is the most common DLT used in practice?
Robert Shaw
What is the difference between the Robert Shaw DLT and the Carlens and White?
Robert Shaw does not have a carinal hook and is D-shaped
What is the purpose of the carina hook on White and Carlens DLT?
Should hook onto the carina, if inserting tube blindly it can confirm placement
What is the optimal size of DLT for patients?
The largest size that fits in the bronchus with a small air leak detectable when the bronchial cuff is deflated
Why is it necessary for the provider to place the largest DLT possible?
These tubes have small internal diameters which interfere with expiration and cause air trapping and auto peep
What factors determine the size of DLT for a patient?
Height and gender
What size DLT should be used for a female less than 5’3?
35 F (ID 5.0)
What size DLT should be used for a female greater than 5’3?
37 F (ID 5.5)
What size DLT should be used for a male less than 5’7?
39 F (ID 6.0)
What size DLT should be used for a male greater than 5’7?
41 F (ID 6.5)
What is the average depth of insertion for a DLT?
28-29cm
What formula can be used to determine depth of a DLT?
depth = 12.5 + (0.1 x height in cm)
What type of blade is best to use when placing a DLT?
Curved blade provides optimal space to place DLT
How should a DLT be placed?
Passed with distal curvature concave anteriorly, then rotate 90 degrees towards the side that is to be intubates after the tip enters the larynx
What are ways to confirm the DLT is in the correct place?
Pediatric bronchoscope or Clamping and listening to each side
What should occur to the side of the lung that is clamped when ventilating the other lung?
No change in moisture
Ipsilateral hemithorax des not move
Ipsilateral breath sounds disappear
How much air should be added to the tracheal cuff?
5-10mL
How much air should be added to the bronchia cuff?
1-2mL
On a left DLT what breath sounds should be heard when the tracheal lumen is clamped?
Breath sounds on the left side
What is the problem when bilateral breath sounds are heard when the trachea lumen is clamped in a left sided DLT?
Indicates bronchial opening still in trachea and the tube should be advanced
What is the problem when right sided breath sounds are heard when the trachea lumen is clamped in a left sided DLT?
Indicates incorrect entry of the tube into the right bronchus
On a left DLT what breath sounds should be heard when the bronchial lumen is clamped?
Unilateral right sided breath sounds
What is the desired view down the bronchial lumen with a FOI scope?
Bronchial carina and Very slight luminal narrowing
Why might the provider adjust the DLT after visualization of the bronchial lumen?
If excessive luminal narrowing is visualized
What is the desired view down the tracheal lumen with a FOI scope?
Tracheal carina
Left lumen going off to the left side and the upper left surface of left bronchial cuff
Why might the provider adjust the DLT after visualization of the tracheal lumen?
Rightward tracheal carinal deviation
Herniation of bronchial cuff
What is the most common problem encountered when positioning a left endobronchial tube?
Inserting too deeply and excluding the right lung from ventilation
What is the most common problem encountered when positioning a right endobronchial tube?
Excluding the right upper lobe from ventilation
What are the three types of malposition in DLT?
In too far on the left side
Out too far in the trachea
In too far on the right side
What are left endobronchial tubes used for?
Right and Left sided thoracotomy
How is the left lung ventilated during a right thoracotomy?
The tracheal lumen is clamped and the bronchial lumen ventilates the left lung
How is the right lung ventilates during a left thoracotomy?
The bronchial lumen is clamped and the tracheal lumen ventilates the right lung
What should the provider do if a left DLT is used on a left thoracotomy and the surgeon needs to clamp the left mainstream for pneumonectomy?
Move the bronchial lumen into the trachea and then use as a standard ETT
What are indications for a Right DLT?
Resection of a thoracic aortic aneurysm
Tumor in the left mainstream bronchus
Left lung transplant or pneumonectomy
Left sided tracheo-bronchial disruption
What should be seen with FOI scope in the bronchial lumen when a right DLT is used?
Bronchial carina and right upper love bronchial orifice
What is a bronchial blocker?
Inflatable device that is passed along or through a single lumen ETT to selectively occlude a bronchial orifice
What is a univalent tube?
Single lumen ETT with built in side changes for retractable bronchial blocker
What should be used to watch and confirm bronchial blocker placement?
Flexible bronchoscope
What are the advantages to bronchial blockers?
Patient who requires intubation post op do not have to redo their laryngoscopy and change out ETT
What is a major disadvantage to bronchial blockers?
Blocked lung collapses slowly and sometimes incompletely due to small size of channel within the blocker
How is a bronchial blocker placed?
ETT passed normally then turned 90 degrees toward operative side, bronchial blocker pushed to the mainstream bronchus under direct visualization with FO scope
What type of cuff does a bronchial blocker have?
High pressure low volume cuff
How much air should be added to a bronchial blocker?
6-8mL
What can the channel of the bronchial blocker be used for?
Allows lung to slowly deflate and can be used for suctioning or insufflating oxygen
What is a fogarty catheter used with?
Standard ETT, guide wire in catheter is used to facilitate placement through ETT
What is a disadvantage of a Fogarty catheter compared to a bronchial blocker?
The Fogarty catheter does not allow suctioning or ventilation of the isolated lung
What are indications for lung resection?
Diagnosis and treatment of pulmonary tumors
Necrotizing pulmonary infections
Bronchiectasis
What are majority of tumors related to in the lungs?
90% Carcinoma
8-10% Adenoma
Benign mass 1-2%
What two categories are malignant tumors of the lungs divided into?
Small cell (oat cell) 20% Non-small cell 80%
What are environmental factors that could increase the likelihood of lung tumor development?
Nickel, Asbestos and Uranium exposure
What is the procedure of choice for cancer in the lung?
Lobectomy, entering at the 5-6th intercostal space
What is the most common complication related to post op lung surgery?
CV in nature
What FEV1 indicates a low risk for patients undergoing a pulmonary procedure?
Greater than 2L or 80% predicted
What FEV1 indicates a high risk for patients undergoing a pulmonary procedure?
Less than 2L or 40% predicted
At what points during and after pulmonary surgery do complications generally occur?
Perioperative due to ischemia from hemodynamic changes MI possible
POD 3 from hypoxia due to uneven pain medication or withdraw
What arterial blood gas may indicate a high risk patient for a pneumonectomy?
PaCO2 greater than 45mmHg on room air or PaO2 less than 50mmHg
What FEV1/FVC may indicate a high risk patient for a pneumonectomy?
Less than 50% predicted
What maximum O2 uptake may indicate a high risk patient for a pneumonectomy?
Less than 10mL/kg/min
What maximum voluntary ventilation may indicate a high risk patient for a pneumonectomy?
Less than 50% of predicted
What are split lung function test used for in the pre op evaluation?
Uses radio labeled albumin to calculate the predicted pulmonary function, postoperative outcome and survival after pneumonectomy
How can the provider predict post op FEV1?
Pre op total FEV1 x % blood flow to remaining lung
What is the minimal predicted post op FEV1 necessary for long term survival?
800-1000mL
What additional pathologies are associated with small cell lung carcinomas?
SIADH
Lambert eaton myasthenic syndrome
Carcinoid syndrome
What symptoms of SIADH develop in small cell lung carcinomas?
Oat cell carcinoma of the lungs may cause low urine output, hypovolemia, hyponatremia, CHF and pulmonary edema
What symptoms are associated with Lambert-Eaton Myasthenia Syndrome?
Increased muscle weakness due to decreased calcium levels at the neuromuscular junction
What pathology is associated with Non-small cell lung carcinomas?
Ectopic parathyroid hormones
What electrolyte abnormality is associated with ectopic parathyroid hormones?
Hypercalcemia
What class of drugs will need to be altered in patients with small cell lung carcinoma?
Non depolarizing NMBA if Lambert Eaton Myasthenic syndrome is present
What are the four M’s that should be considered on assessment in patients with lung cancer?
Mass effect
Metabolic effects
Metastases
Medications
What mass effect is associated with lung cancer?
Obstructive pneumonia, SVC syndrome, tracheobronchial distortion, RLN or phrenic nerve paresis
What metabolic effects are associated with lung cancer?
Lambert-Eaton syndrome
Hypercalcemia
Hyponatremia
Cushings syndrome
Where are the most common metastatic sites for lung cancer?
Brain
Liver
Bone
Adrenals
Why should the provider be concerned if a patient is on medications for lung cancer?
Chemo induced lung and heart changes
What medications can be given prior to lung surgery to optimize the patient?
Bronchodilators & Anticholinergics
Why are anticholinergics beneficial to give prior to lung surgery?
To dry up secretions and increase HR to counteract interference with vagus nerve stimulation when the pleura is opened
What additional monitor is considered a standard of care in one lung ventilation?
Arterial line
Where is the arterial line typically placed in patients undergoing one lung ventilation?
Placed on dependent limb to monitor perfusion to extremity
When might a PA cath be considered in patients undergoing one lung ventilation?
LV dysfunction or severe pulmonary HTN
What can be done to prevent a brachial plexus injury while patients are lying in the lateral position?
Axillary roll
What lab needs to be collected prior to initiating one lung ventilation?
ABG, this will be used as a reference point throughout the case
When will the provider switch from two to one lung ventilation?
Maintain two lung ventilation until the pleura is opened
How often should ABGs be collected with one lung ventilation?
Q15m to guide therapy to maintain near baseline
What is the greatest risk during one lung ventilation?
Hypoxemia
What should be done if high peak inspiratory pressure occur during one lung ventilation?
Check ETT position and Reduce TV (increase RR to maintain minute ventilation)
What ventilation parameters should be set for one lung ventilation?
Start with 100% fiO2, titrate down with ABG
TV 5-6mL/k
RR 12-15 to keep PaCo2 35-45mmHg
Peep 0-5cmH2O
What patients should not be given PEEP during one lung ventilation?
Patients with COPD
What should airway pressure be kept at during one lung ventilation?
Peak airway pressures less than 35cmH2O
Plateau airway pressures less than 25cmH2O
How much is the ETCO2 gradient during one lung ventilation?
1-3mmHg
What ventilation mode places a patient at risk for injury during one lung ventilation?
Pressure control especially in patients with bullae, pneumonectomy and post lung transplantation
What should be avoided in order to prevent a decrease in blood flow to the dependent lung during one lung ventilation?
High mean airway pressures Vasoconstrictors Low FiO2 Intrinsic PEEP Decreased CO, hypotension
If a patient becomes hypoxic during one lung ventilation and tube placement has been confirmed what can be done to counteract the effects?
Add 2-10cmH2O PEEP to the collapsed lung
Periodically inflate collapsed lung with 100% O2
What are additional alternatives can be used to treat a hypoxic patient during one lung ventilation?
Stopping ventilation for short periods of time and employing the used of 100% O2 greater than O2 consumption
HFJV-low volumes, high pressure
Why is it necessary to perform the valsalva maneuver on a patient prior to emergence after pulmonary surgery?
Stapling bronchus, checking for leaks
To re-inflate collapsed lung and check for microbleeding
What is the number one complication from thoracic anesthesia?
Hypoxia, respiratory acidosis
What factors contribute to Hypoxia and Respiratory acidosis in post op thoracic surgery patients?
Atelectasis and shallow breathing (splinting due to incisional pain)
Gravity dependent transudation of fluid into dependent lung
What are signs of post op hemorrhage post thoracic surgery?
Chest tube drainage greater than 200mL/min
HoTN, tachycardia and decreased Hct
What is the most common arrhythmia post thoracic surgery?
Atrial fibrillation
What are additional complications that can occur post operatively after thoracic surgery?
Bronchial rupture
Acute right ventricular failure
Positioning injuries
What is a video assisted thoracoscopic surgery?
Use of a video camera and surgical instruments inserted through ports in the thoracic wall
What are advantages of a VAT over thoracotomy?
Smaller incision and no intraoperative rib spreading
Less risk post op hypoxemia
Faster recovery and discharge from hospital
What complications are associated with thoracoscopic procedures?
CO2 insufflation used to improve visualization compresses lung Tension pneumo Hemorrhage Perforation of diaphragm Positioning and DLT
What part of the lung is a mediastinoscopy performed?
Extra pleural, shouldnt have some of the complications associated with an open pleural cavity (pneumothorax)
What is a mediastinoscopy?
Procedure performed with lymph node or tissue biopsy to determine a diagnosis or respectability of an intrathoracic tumor
How is a mediastinoscopy performed?
Small transverse incision just above suprasternal notch. Blunt dissection along pre-tracheal fascia permits biopsy of paratracheal lymph nodes ago the level of the carina
What structures could be disturbed during a mediastinoscopy?
Right carotid and subclavian
RLN
Phrenic and Vagus nerve
What are the borders of the mediastinum?
Anterior border is the sternum
Posterior border is the thoracic vertebrae
Lateral border is the pleural sacs and thoracic inlets
Inferior border is the diaphragm
What is the result of majority of lymph node masses in the middle mediastinum?
90% of lymph node masses in the middle mediastinum result from metastatic spread of malignancies
What symptoms are usually associated with large mediastinal tumors?
Airway obstruction, impaired cerebral circulation and distortion of anatomy
What systemic syndromes is a mediastinal tumor often associated with?
Myasthenia graves Cushing's syndrome Hypercalcemia (parathyroid adenoma) HTN (pheochromocytoma) Myasthenic syndrome (lung CA)
What are additional symptoms that are associated with mediastinal tumors?
Cough, dyspnea, stridor, jugular distention, exaggerated changes in BP associated with postural changes
What is superior vena cava syndrome?
Progressive mediastinal tumor growth may result in compression of the SVC
Obstructed venous drainage in the upper thorax
Why might someone with SVS have an increased ICP?
Greater CVP
What are the absolute contraindications to a mediastinoscopy?
Inoperability
Coagulopathy
Thoracic aortic aneurysm
Why is inspiration impaired in patients with an extra thoracic mass?
With inspiration as negative intrapleural pressure increases, the mass closes in on itself and narrows the lumen for inspiration
Why do patients with intrathoracic masses have a difficult time exhaling?
As they generate positive pressure, the mass collapses on itself and exhalation is impaired
Where might the provider place IV if the patient has SVS ?
Lower extremities
What is the most common complication of a mediastinoscopy?
Mediastinal hemorrhage, surgical bleeding more likely in patients with increased CVP
What complications are associated with a mediastinoscopy?
Acute airway obstruction
Anticipated difficulties with intubation and ventilation
VAE
Mediastinal hemorrhage
What type of ETT may be used in patients with mediastinal tumors?
ETT with coil inside to prevent collapse, if placed near carina flow can still be maintained
Why should the provider avoid giving NMBA on induction in patients with known mediastinal tumors?
Collapse of smooth muscle around the tumor causes a loss in airway
What is the second most common injury in a mediastinoscopy?
Pneumothorax, avoid N2O use
What is the third most common injury in mediastinoscopy?
RLN injury, monitor for post op respiratory compromise
What can cause a vagal response during a mediastinoscopy?
Compression of trachea or great vessels causing reflex bradycardia
What should the provider do if SVC obstruction occurs during Mediastinoscopy?
Place the patient in the lateral reverse trendelenburg, prone or hight fowlers position
The goal is to cause the mass to shift away from the trachea or SVC and relieve the obstruction
What criteria need to be present prior to extubating a patient after a mediastinoscopy?
Full TOF
Full return of airway reflexes
Patients with SVC syndrome must be fully awake as they can easily obstruct
Why is a post op CXR required in patients who have had a mediastinoscopy?
To rule out pneumothorax
