Thoracic Anesthesia Flashcards
What does V/Q mismatching lead to?
HYPOXIA
Awake Patient
Spontaneous respirations, upright position, & closed chest Lungs apex maximally dilated 1° ventilation occurs at base Perfusion also prefers the base V/Q match preserved
Awake Patient in the Lateral Decubitus Position
Spontaneous respirations, lateral decubitus position, & closed chest
V/Q matching preserved
Dependent lung receives > ventilation & perfusion than the upper (non-dependent) lung
Diaphragm displacement cephalad
Anesthetized Paralyzed Patient in the Lateral Decubitus Position
Positive-pressure ventilation, lateral decubitus position, & closed chest Paralysis = PPV Non-dependent lung ↓resistance ↓FRC V/Q mismatch Dependent lung ↑perfusion Non-dependent lung ↑ventilation
Anesthetized Patient Spontaneous Respirations in the Lateral Decubitus Position w/ Open Chest
Spontaneous breathing, lateral decubitus position, & open chest (ex: trauma)
V/Q mismatch ↑shunt
Dependent lung ↑perfusion
Upper long collapse → progressive hypoxemia
- Mediastinal shift
- Paradoxical respirations
Anesthetized Paralyzed Patient in the Lateral Decubitus Position w/ Open Chest
Positive pressure ventilation, lateral decubitus position, & open chest (2 lung ventilation)
PPV worsens V/Q mismatch
Non-dependent lung ↑ventilation > perfusion
Dependent lung ↑perfusion > ventilation
HPV
Hypoxic pulmonary vasoconstriction
Diverts blood AWAY from hypoxic lung regions
↓blood flow to the non-ventilated lung
Improves arterial oxygen content → improves hypoxemia
↓shunt
Normal Pulmonary Blood Flow
Average BOTH lungs being non-dependent (upper)
40%
60%
What factors inhibit HPV?
↑pulmonary vascular resistance (↑PAP, volume overload, mitral stenosis)
Hypocapnia (alkalosis or ↓CO2)
↑↓mixed venous PO2
Vasodilators - Nitroglycerin, sodium nitroprusside, β agonists (Dobutamine), Ca2+ channel blockers
Pulmonary infection
Inhalational anesthetics 1 MAC = 4-6% ↑intrapulmonary shunt
Hypothermia
One-Lung Ventilation
Advantages
Improved operating conditions & visibility
Facilitates access to the aorta & esophagus
Prevents cross-contamination w/ abscess, secretions, & blood
Press anesthesia gases loss w/ bronchopleural fistula
One-Lung Ventilation
Relative Contraindications
Difficult airway w/ poor larynx visualization Lesion in the bronchial airway precluding bronchial intubation Thoracic aortic aneurysm Pneumonectomy Lobectomy Thoracotomy or thoracoscopy Sub-segmental resections Esophageal surgery
One-Lung Ventilation
ABSOLUTE Contraindications
Pulmonary infection Copious bleeding on one side Bronchopulmonary fistula Bronchial rupture Large lung cyst Bronchopleural lavage
Adult Trachea
11-12cm
Begins at cricoid cartilage (C6)
Bifurcates at the sternomanubrial joint (T5)
R Bronchus
Wider (more common to R mainstem)
Diverges away from trachea at 20-25° angle (less acute as compared to L)
RUL orifice sits only 1-2cm to carina
R double-lumen ETT has Murphy eye to ventilate RUL
L Bronchus
Narrower
Diverges away from trachea at 40-45° angle
LUL orifice sits about 5cm distal to the carina
Double-Lumen Tube Sizing
Short 4’6”-5’3” → 35-37Fr
Medium 5’3”-5’7” → 37-39Fr (most commonly used size 39Fr)
Tall >5’7” → 41Fr
DLT Insertion Technique
Curved bladed provides optimal space
Insert w/ blue bronchial tube upward
Rotate 90° towards side to be intubated after tip enters the larynx
Insertion depth 28-29cm at the teeth
Tracheal Cuff
5-10mL air
Bronchial Cuff
1-2mL air
When to check DLT placement w/ fiberoptic scope?
After initial placement
Re-check after positioning patient for surgery in the lateral decubitus position
Where to clamp the DLT?
Clamp on the double-lumen connector piece closer to the circuit
Allows lung deflation via port
DLT Complications
Advanced too deep (L DLT → excludes R lung from ventilation)
Not inserted far enough
Bronchial tube advances on wrong side
R DLT Murphy eye does not properly align w/ RUL
Bronchial cuff herniation across carina
R DLT Indications
Thoracic aortic aneurysm resection
Tumor in the L mainstem bronchus
L lung transplantation or L pneumonectomy (not absolute indication)
L-sided tracheobronchial disruption
R DLT Placement Confirmation
Fiberoptic scope
View down both L tracheal lumen & R bronchial lumen
Ensure the Murphy eye aligns w/ RUL to provide adequate ventilation & prevent atelectasis
Retroflex the fiberoptic scope to visualize the RUL via the Murphy eye
Bronchial Blocker
Advantages
Patients who require intubation postop do not have to exchange ETT to single lumen
Bronchial Blocker
Disadvantages
Blocked lung collapses slowly & sometimes incompletely d/t small channel size w/in the blocker
Apply suction or syringe to pull back air & help deflate the lung
Univent Bronchial Blocker
ETT placed w/ blocker fully retracted
Rotate ETT 90° towards the operative side
Push the bronchial blocker into the mainstem bronchus under direct visualization
High-pressure low-volume cuff → use minimum volume to prevent leak
Lung Resection Indications
Diagnose & treat pulmonary tumors
Necrotizing pulmonary infections
Bronchiectasis
Preop Testing
- CXR
- Chest CT
- EKG/cardiac clearance
- ABG
- PFTs
- Ventilation-perfusion tests
FEV1
Forced expiratory volume in 1 second
> 2L or 80% predicted = low risk
< 2L or 40% predicted = high risk
FEV1/FVC
Normal = 75-80%
High risk patients < 50% predicted
High Risk Pneumonectomy Patients
ABG PaCO2 > 45mmHg on RA & PaO2 < 50mmHg FEV1 < 2L or < 50% predicted FEV1/FVC < 50% predicted Maximum O2 uptake (VO2) < 10mL/kg/min Maximum voluntary ventilation < 50% predicted
Split-Lung Function Tests
Uses radio-labeled albumin to calculate predicted pulmonary function, postop outcome, & survival after pneumonectomy
Predicts isolated lung FEV1 after the other lung removed
Postop FEV1 = preop total FEV1 x % blood flow to the remaining lung
Minimal predicted postop FEV1 necessary for long-term survival = 800-1,000mL
Small Cell Lung Carcinoma
Lambert-Eaton myasthenic syndrome (LEMS) ↑muscle weakness d/t ↓Ca2+ levels at the NMJ
Carcinoid syndrome
Lung Oat Cell Carcinoma
Small cell lung carcinoma
SIADH ↓UOP, hypervolemia, hyponatremia
CHF
Pulmonary edema
Non-Small Cell Lung Carcinoma
Ectopic parathyroid hormone → Ca2+ problems
Patients w/ Lung Cancer
ASSESSMENT
Mass effects - obstructive pneumonia, SVC syndrome, tracheo-bronchial distortion, RLN or phrenic nerve paralysis
Metabolic effects - LEMS, hypercalcemia, hyponatremia, Cushing syndrome
Metastases → brain, liver, bone, & adrenals
Medications - chemotherapy-induced lung/cardiac changes
Thoracotomy
Preop Medications
Bronchodilators
Anticholinergics ↓secretions ↑HR to counteract Vagus nerve stimulation when pleura opened
Thoracotomy
Monitoring & Equipment
Multiple size ETTs
Difficult airway cart w/ pediatric fiberoptic
A-line (place on dependent limb to monitor extremity perfusion) CVP or PA catheter less common PIV x2 Blood warmer & rapid infuser available Type & cross PRBCs
Lateral Decubitus Positioning
Axillary roll to protect brachial plexus
Ensure proper placement
Thoracotomy
Postop Pain Management
Thoracic epidural
One-Lung Ventilation
Anesthesia Management
Baseline ABG prior to one-lung ventilation
Maintain two-lung ventilation until pleura opened
Maximum anesthesia depth w/ chest opening & rib splitting
Operative lung deflated (clamp & open port; apply suction to help deflate as needed)
- 100% FiO2 to dependent lung
- Obtain ABG 15min after one-lung ventilation initiated
- Continue ABG Q30min-1hr
- Volume or pressure controlled
- Vt 5-6mL/kg
- RR 12-15bpm to maintain PaCO2 35-45mmHg
- PEEP 0-5mmHg
What is the greatest risk associated w/ one-lung ventilation?
Hypoxemia
One-Lung Ventilation
↑PIP
Check ETT position
Reduce Vt & ↑RR to maintain minute ventilation
Maintain peak airway pressures < 35cmH2O
Plateau airway pressures < 25cmH2O
What patients should not receive PEEP?
COPD
After deflating the lung, expect to see what vital sign change?
ETCO2 ↑1-3mmHg during one-lung ventilation
Response to hypoxemia during one-lung ventilation:
ASSESSMENT & INTERVENTIONS
Confirm ETT placement
↑FiO2 100%
Check hemodynamic status → HoTN ↓SpO2 ↓ETCO2
+ 2-10cmH2O CPAP to the collapsed lung
Periodically inflate the collapsed lung w/ 100% oxygen (inform the surgeon)
+ 5-10cmgH2O PEEP to the dependent lung
Continuous insufflation to the collapse lung w/ 100% FiO2
Early ligation/clamping to the ipsilateral pulmonary artery (when performing pneumonectomy) ↑blood flow to one-lung & improves V/Q match
One-Lung Ventilation Alternatives
Stop ventilation for short period & used 100% FiO2 insufflated at rate > O2 consumption
Apneic oxygenation 10-20min → progressive respiratory acidosis ↑PaCO2 6mmHg 1st min & 3-4mmHg each additional min
High frequency jet ventilation - low volumes w/ high pressure
Emergence
Inflate lung to 30cmH2O
Valsalva requested per surgeon to check for leaks or microbleeding (watch monitor bradycardia)
Thoracostomy tubes places
Exchange DLT to single lumen prior to transporting to ICU when patient remains intubated after surgery (consider tube exchanger w/ DVL)
Thoracic Anesthesia Complications
Hypoxemia or respiratory acidosis Postop hemorrhage Arrhythmias (Afib most common) Bronchial rupture Acute R ventricle failure Positioning injuries
What contributes to the 1° complication postop thoracic surgery developing?
Hypoxemia & respiratory acidosis
Atelectasis & shallow breathing d/t incisional pain
Gravity dependent fluid transudation into the dependent lung
Postop Hemorrhage S/S
Occurs in 3% thoracic surgery
Associated w/ 20% mortality
CT drainage > 200mL/min
Hypotension
Tachycardia
↓Hct
What causes bronchial rupture?
Excessive bronchial tube cuff inflation
Acute RV Failure S/S
Low CO
↑CVP
Oliguria
VATS
Video-assisted thoracoscopic surgery
Uses video camera & surgical instruments inserted via port in the thoracic wall
Typically 3-5 ports
Staplers used to resect lung tissue & divide large blood vessels
VATS
Indications
Lung biopsy Wedge resection Hilar & mediastinal mass biopsy Esophageal & pleural biopsy Pericardiectomy Pneumonectomy
VATS
Advantages
Smaller incision No intraop rib spreading Less postop pain ↓risk postop hypoxemia Faster recovery & discharge from hospital
VATS
Anesthetic Approaches
Local, regional (epidural), or general anesthesia
Two or one-lung ventilation
*General anesthesia most common approach
VATS
Preop Evaluation & Planning
Discuss pain management options w/ patient
Consider conversion to open thoracotomy & consult surgeon Same preop evaluation as thoracotomy
VATS
Intraop Anesthetic Management
GA one-lung ventilation w/ DLT or bronchial blocker Surgeon injects LA prior to placing ports Lateral decubitus position PIV x2 A-line ABG Q30min-1hr Suction lung & gently re-inflate Exchange DLT → single lumen CT placed prior to closing
VATS
Intraop Complications
CO2 insufflation to improve surgical visualization → hemodynamic compromise or gas embolism enters venous circulation (VAE) Tension pneumothorax Hemorrhage Diaphragm or other organ perforation Positioning & DLT complications
Mediastinoscopy
Lymph node or tissue biopsy to diagnose lung carcinoma, thymoma, or lymphoma or to determine intrathoracic tumor resectability
Performed via small transverse incision above the suprasternal notch
Scope similar appearance to laryngoscope inserted anterior to the trachea to biopsy lymph nodes
Mediastinoscopy
Anesthetic Considerations
Chest roll behind back to help facilitate head/neck extension
GETA
Innominate artery supplies R arm & R common carotid
Place A-line and/or Pox on R arm
Absent waveform indicates innominate artery compression → ask surgeon to reposition the scope
BP cuff on L arm
Central airway obstruction d/t trachea compression during induction or mediastinoscope manipulation near the trachea
Mediastinal Tumors S/S
Often asymptomatic & discovered incidentally on CXR
Symptomatic masses are usually malignant w/ extensive involvement → airway obstruction, impaired cerebral circulation, anatomy distortion
Frequently associated w/ systemic syndromes
Cough, dyspnea, stridor, jugular distention, exaggerated BP changes associated w/ positioning
SVC syndrome
SVC Syndrome
Progressive mediastinal tumor growth results in SVC compression → obstructs venous drainage into the upper thorax
SVC Syndrome S/S
Venous distension in the neck, thorax, & upper extremities
Facial, conjunctiva, neck & upper chest edema
Mouth & larynx edema associated w/ severe airway obstruction
Mucosal edema & direct compression → cyanosis d/t compromise trachea airflow
Depressed CO d/t impeded upper body VR or direct mechanical heart compression from the tumor
Venous backflow into the upper extremity IV lines
↑ICP
Mediastinoscopy
Relative Contraindications
SVC syndrome Previous medistinoscopy (scar tissue) Airway obstruction & distortion Impaired cerebral circulation Myasthenic syndrome
Mediastinoscopy
ABSOLUTE Contraindications
Inoperable
Coagulopathy (hemorrhage risk)
Thoracic aortic aneurysm
Mediastinoscopy
Preop Considerations
Assess airway compromise S/S including dyspnea, tachypnea, tracheal deviation
CXR & CT scan
Assess tumor size & location
Evaluate tracheal distortion or compression
PFTs obtained in upright & supine position
Flow-volume loops detect airway obstruction
Patient able to lay flat?
SVC obstruction or impaired cerebral circulation
Muscle relaxants, coughing & breath holding, and/or position changes potential to worsen symptoms
Mediastinoscopy
Monitoring & Equipment
PIV x2
Consider placing in lower extremities d/t SVC syndrome
Monitor R radial pulse (doppler, A-line, Pox)
BP cuff on L arm
PNS
Mediastinoscopy
Anesthetic Management
Deep anesthesia to blunt autonomic reflexes
Avoid N2O & monitor for pneumothorax
Innominate, R subclavian, or R carotid artery compression → distal pulse loss & postop neuro deficits
RLN or phrenic nerve injury
Vagal-mediated reflex bradycardia d/t trachea or vessels compression
Mediastinoscopy
Emergence
4/4 twitches
Airway reflexes present
SVC syndrome patients awake to prevent obstruction
Postop CXR on ALL patients to r/o pneumothorax
Mediastinoscopy
COMPLICATIONS
Mediastinal hemorrhage Pneumothorax RLN injury Phrenic nerve injury or L hemiparesis Esophageal injury Air embolism → HOB elevated 30° Dysrhythmias Acute airway obstruction
Mediastinal Hemorrhage
Most common complication
Prevention → limit IVF especially in SVC syndrome patients
↑CVP ↑risk
Pneumothorax
2nd most common mediastinoscopy complication
RLN Injury
3rd most common mediastinoscopy complication NIMS tube provides nerve monitoring - Place w/ video laryngoscope Monitor postop respiratory status Hoarseness or vocal cord paralysis
Acute Airway Obstruction
Prolonged tumor cause tracheal malasia leading to tracheal collapse → GA w/ reinforced ETT
Place patient in lateral, reverse Trendelenburg, prone, or high Fowlers position to help shift mass away from the trachea or SVC & relieve the obstruction
Difficult Intubation and/or Ventilation
Various ETT sizes, establish ability to ventilate BEFORE muscle relaxation, & provide intraop muscle relaxation to prevent coughing/straining
Interventions to implement that ↓respiratory complications incidence in high risk patients undergoing thoracic surgery:
Smoking cessation
Physiotherapy
Thoracic epidural analgesia
Patients undergoing pulmonary resection preop evaluation:
3 parts
- Lung mechanical function
- Pulmonary parenchymal function
- Cardiopulmonary reserve
What patient population is at an increased risk for cardiac complications, particularly arrhythmias, after pulmonary resections?
Geriatric patients
Best predictor post-thoracotomy outcome in the elderly = preop exercise capacity
