Thoracic Anesthesia Flashcards
Challenges in thoracic anesthesia
- physical derangements caused by lateral decubitus
- open pneumo for surgery
- surgical manipulation interfering with heart and lung function
- risk of rapid, massive bleeding
- necessity for one-lung ventilation
lateral decubitus position
- optimal surgical access for many thoracic procedures
- potential for significant alteration in normal respiratory physiology
- disrupts vent/perf relationships
complications with lateral decubitus
- coughing, tachy, HTN during turn to lateral decub
- hypotension from blood pooling in dependent portions
- V/Q mismatching = hypoxemia
- interstitial pulm edema of dependent lung
- brachial plexus and peroneal nerve injury
- mononuclear blindness (pressure on dependent eye)
- outer ear ischemia
- axillary artery compression
awake patient, upright position, spontaneous respirations, closed chest
- apex of the lungs are maximally dilated (zone 1)
- most ventilation occurs at base of lungs
- perfusion also favors base of lungs
- V/Q matching is preserved during spontaneous respirations
awake patient, lateral decubitus position, spontaneous respirations, closed chest
- V/Q matching preserved
- dependent lung receives more ventilation and perfusion than the upper lung (non-dependent lung)
things that cause progressive cephalad displacement of diaphragm during surgery
- supine position
- induction of anesthesia
- paralysis
- surgical position and displacement
anesthetized patient, lateral decubitus position, paralyzed, closed chest
- positive pressure ventilation
- decrease in FRC
- V/Q mismatching
- dependent lung = greater perfusion; not as much ventilation in this situation because abdominal contents are not pressing up and diaphragm is not pulling down more (so not as much ventilation compliance)
- non-dependent lung = greater ventilation
anesthetized patient, lateral decubitus position, paralyzed, open chest
- V/Q mismatching
- perfusion remains greater in dependent lung
- upper lung collapse leads to progressive hypoxemia
- upper lung collapse also leads to –> mediastinal shift and paradoxical respirations
anesthetized patient, lateral decubitus position, paralyzed, open chest, 2 lung ventilation
- positive pressure ventilation
- may worsen V/Q mismatching
- ventilation greater in non-dependent lung
- perfusion greater in dependent lung
Summary of lateral decubitus + open chest on ventilation and perfusion
- V/Q mismatch
- non-depdendent V > Q
- dependent V < Q
- effects of positioning, open chest (mediastinal shift), anesthesia with paralysis
hypoxic pulmonary vasoconstriction (HPV)
- diverts blood away from the hypoxic regions of the lungs
- decreased blood flow to the non-ventilated lung
- helps improve arterial oxygen content, improving hypoxemia
- decreases shunt
Left lung non-dependent blood flow distribution
- non-dependent lung (L) 35%
- dependent lung (R) 65%
Right lung non-dependent blood flow distribution
- non-dependent lung (R) 45%
- dependent lung (L) 55%
average blood flow distribution with both lungs being non-dependent
- non-dependent 40%
- dependent 60%
factors that inhibit HPV
- high pulmonary vascular resistance (increased PAP, volume overload, mitral stenosis)
- hypocapnia
- high or very low mixed venous PO2
- vasodilators - NTG, SNP, beta agonists (dobutamine), calcium channel blockers
- pulmonary infection
- inhalation anesthetics (1 MAC = 4% increase in shunt)
which inhalation agents increase shunt
- isoflurane
- halothane
HPV & OLV
- OLV causes a 50% HPV response
- decreases the blood flow in the non-dependent lung to 20%
- increases the blood flow in the dependent lung to 80%
HPV & Isoflurane
- 1 MAC isoflurane inhibits HPV by 21%
- blood flow 24:76
- therefore the intrapulmonary shunt is increased by 4%
why is OLV beneficial in thoracic procedures
- better operating conditions with collapse of diseases lung
- facilitates access to the aorta and esophagus
- prevents cross-contamination with abscess, secretions, blood
- prevents loss of anesthetic gases with bronchopleural fistula
relative contraindications for OLV
- difficult airway with poor visualization of the larynx
- lesion in bronchial airway precluding bronchial intubation
ABSOLUTE indications for OLV
- pulmonary infection
- copious bleeding on one side
- bronchopulmonary fistula
- bronchial rupture
- large lung cyst
- bronchopleural lavage
RELATIVE indications for OLV
- thoracic aortic aneurysm
- pneumonectomy
- lobectomy
- thoracotomy; thoracoscopy
- subsegmental resections
- esophageal surgery
what three techniques can be used to achieve OLV?
- double lumen ETT
- bronchial blocker (used with standard ETT)
- single lumen ETT
characteristics of double lumen endotracheal tubes (DLT)
- longer bronchial lumen which enters either the R or L mainstem bronchus
- shorter tracheal lumen remaining in the distal trachea
- preformed curve that allows preferential entry into the L or R side
- separate bronchial and tracheal cuffs
- tubes specifically designed for L or R side due to differences in anatomy
anatomy of adult trachea
- 11-12 cm long
- begins at C6 (cricoid cartilage)
- bifurcates at the sternomanubrial joint (T5)
anatomy R bronchus
- wider
- diverges away from trachea at 20-25 degree angle
- orifice of RUL sits only 1-2 cm to carina
anatomy L bronchus
- narrower
- diverges away from trachea at 40-45 degree angle
- orifice of LUL sits about 5 cm distal to carina
sizing the DLT
- small = 4’6” - 5’3” –> 35-37 Fr
- medium = 5’3” - 5’7” –> 37-39 Fr (most commonly used size)
- tall = >5’7” –> 41 Fr
- proper size allows for 1-2 mm smaller than patient’s L bronchus to allow for space of bronchial cuff
best predictor of DLT size
height of patient
DLT insertion technique
- laryngoscopy with curved blade provides optimal space to place DLT
- DLT is passed with the distal curvature concave anteriorly, then rotated 90 degrees toward the side that is to be intubated after the tip enters the larynx
- advance DLT until resistance felt (avg insertion dept is 28-29 cm at teeth)
- confirm correct placement (FOB)
protocol for checking DLT placement
- inflate tracheal cuff (5-10 mL of air)
- check for bilateral breath sounds (unilateral breath sounds indicate tube too far down and tracheal opening is endobronchial)
- inflate bronchial cuff (1-2 mL air)
- clamp tracheal lumen
- check for unilateral L breath sounds
- persistence of R sided breath sounds indicate bronchial opening still in trachea and tube should be advanced
- unilateral R sided breath sounds indicate incorrect entry of the tube into the R bronchus
- unclamp tracheal lumen and clamp bronchial lumen
- check for unilateral R breath sounds
- fiberoptic confirmation (check both supine and after LDP positioning)
problems with DLT placement
- in too far
- not far enough
- wrong side
most common problem with L endobronchial tube placement
-inserting too deeply excluding R lung from ventilation
most common problem with R endobronchial tube placement
-exclusion of R upper lobe from ventilation
indications for L endobronchial tubes
- used for R sided thoracotomy –> tracheal lumen is clamped and L lung ventilated through bronchial lumen
- used for L sided thoracotomy –> bronchial lumen clamped and R lung ventilated through tracheal lumen; if surgeon needs to clamp L mainstem for pneumonectomy, move bronchial lumen into the trachea and use as standard ETT
indications for R DLT
- resection of thoracic aortic aneurysm
- tumor in L mainstem bronchus
- L lung transplantation or L pneumonectomy
- L sided tracheo-bronchial disruption
bronchial blockers
- inflatable devices passed alongside or through single lumen ETT to selectively occlude a bronchial orifice
- regular ETT used with inflatable catheter (Fogarty cath), guide wire used for placement
- blocker must be advanced, positioned, and inflated under direct visualization via flexible bronchoscope
univent tube
- single lumen ETT with built-in side channel for retractable bronchial blocker
- ETT placed with blocker fully retracted
- ETT is then turned 90 degrees toward operative side
- bronchial blocker pushed into mainstem bronchus under direct visualization with fiberoptic scope
- cuff of blocker is high pressure, low volume cuff, so use minimum volume to prevent leak
- channel within blocker allows lung to slowly deflate
- channel can also be used for oxygenation and suctioning
major advantage of bronchial blockers
patient who requires intubation post op do not have to redo their laryngoscopy and change out ETT
major disadvantage of bronchial blockers
blocked lung collapses slowly and sometimes incompletely due to small size of channel within the blocker
Fogarty Catheter
- used with standard ETT
- guide wire in catheter is used to facilitate placement through ETT
- does not allow suctioning or ventilation of the isolated lung
indications for lung resection
- diagnosis and treatment of pulmonary tumors
- necrotizing pulmonary infections
- bronchiectasis
preoperative testing for lung resection
- CXR/Chest CT
- EKG
- ABG
- PFTs –> FEV 1 > 2L or 80% predicted is low risk; FEV1 < 2L or 40% predicted is high risk
- ventilation perfusion tests
ABG high risk patient
PaCO2 > 45 mmHg (on room air)
PaO2 < 50 mmHg
FEV1 high risk patient
- most commonly used and most important
- <2L or < 50% predicted
FEV1/FVC high risk patient
-< 50% predicted
maximum O2 uptake VO2 high risk patient
< 10 mL/kg/min
max voluntary ventilation high risk
< 50% predicted
split lung function test
- uses radio-labeled albumin to calculate the predicted pulmonary function, postop outcome, and survival after pneumonectomy
- predicts FEV1 of isolated lung if other lung is removed
- minimal predicted postop FEV1 necessary for long-term survival is 800-1000 mL
chemo that causes cardiomyopathy
- doxorubicin
- cyclophosphamide
- check preop ECHO
chemo that causes pulmonary toxicity
- bleomycin (pulmonary tox with high FiO2)
- mitomycin-C
- cyclophosphamide
chemo side effects
- bone marrow suppression
- check platelets, RBCs, WBCs
small cell lung carcinoma
- paraneoplastic syndrome
- SIADH - oat cell carcinoma of lung may cause low UOP, hypervolemia, hyponatremia, CHF, pulmonary edema
- LEMs - associated with small lung CA; increased muscle weakness due to decreased calcium levels at neuromuscular junction
- carcinoid syndrome
non-small cell lung carcinoma
- paraneoplastic syndrome
- ectopic parathyroid hormone
assessment of patients with lung cancer pneumonic
- Mass effects
- Metabolic effects
- Metastases
- Medications
Mass Effects of patients with lung cancer
- obstructive pneumonia
- SVC syndrome
- tracheo-bronchial distortion
- RLN or phrenic nerve paresis
Metabolic Effects of patients with lung cancer
- LEMs
- hypercalcemia
- hyponatremia
- Cushing syndrome
Metastases of patients with lung cancer
- brain
- liver
- bone
- adrenals
Medications Effects of patients with lung cancer
-chemo induced lung/cardiac changes
premedication of patient for pneumonectomy
- bronchodilators
- anticholinergics - like glyco; decrease secretions; increase HR to counteract interference with vagus nerve stimulation when the pleura is opened
patient equipment/monitoring for pneumonectomy
- airway equipment = multiple ETT (DLT and standard); difficult airway cart
- A line = standard of care for OLV to do ABGs; placed on dependent limb to monitor perfusion to extremity
- CVP = not necessary, but desirable to guide fluid management
- PA Cath = LV dysfunction or severe pulm HTN; not used a lot anymore
pain management for pneumonectomy
-consider thoracic epidural for postop pain management
positioning for pneumonectomy
lateral decubitus; properly placed ax roll to protect brachial plexus
pneumonectomy fluids
- 2 large bore IVs
- avoid over hydration bc do NOT want pulmonary edema
- have blood warmer and rapid infusion device available
- T & C
- PRBCs
OLV management
- ALWAYS get baseline ABG prior to institution of OLV (reference point)
- maintain two lung ventilation until pleura is opened
- need max depth of anesthesia with chest opening and rib splitting
- one lung ventilation –> operative lung deflated
- 100% O2 to dependent lung
- obtain ABG 15 min after OLV is initiated; guide therapy to maintain near baseline
- major adjustments in ventilation usually not necessary
greatest risk for OLV
hypoxemia
what to do if you have high peak inspiratory pressures with OLV
- check ETT position (with FOB)
- reduce Vt and increase RR to maintain minute ventilation
ventilation settings for the dependent lung
- FiO2 100%; can decrease after ABG obtained
- Vt 5-6 mL per kg (OK with OLV)
- RR 12-15 to keep PaCO2 35-45 mmHg or close to preop value
- PEEP 0-5
- PCV most ideal especially for those at risk of lung injury
what to do if hypoxemia occurs during OLV?
- confirm tube placement and increase FiO2 to 100%
- check hemodynamic status
- adjust Vt and/or RR
- add 2-10 cmH2O CPAP to collapsed lung
- periodically inflate collapsed lung with 100% O2 (inform surgical team)
- add 5-10 cmH2O PEEP to dependent lung
- continuous insufflation to collapsed lung with 100% O2
- early ligation/clamping of ipsilateral pulmonary artery
OLV alternatives
- stop ventilation for short periods and employing use of 100% O2 insufflated at a rate greater than O2 consumption
- HFJV - low volume, high pressure
emergence for OLV
- inflate lung to 30 cmH2O pressure/may need valsalva
- if stapling bronchus check for leaks
- to re-inflate collapsed lung, check for microbleed
- thoracostomy tubes may be placed
- standard extubation criteria for patients you anticipate extubating at end of procedure
- if patient to remain intubated, must change out to single-lumen ETT prior to transporting to unit
complications from thoracic anesthesia
- hypoxemia/respiratory acidosis (#1 complication)
- postop hemorrhage
- arrhytmias
- bronchial rupture
- acute RV failure
- positioning injury
VATS (video assisted thoracoscopic surgery)
- use of video camera and surgical instruments inserted through ports in the thoracic wall
- usually 3-5 ports
- staplers also used to resect lung tissue and divide large blood vessels
indications for VATS
- lung biopsy
- wedge resection
- biopsy of hilar and mediastinal masses
- esophageal and pleural biopsy
- pericardiectomy
advantages of thoracoscopic over thoracotomy
- smaller incision
- no intraoperative rib spreading
- less post op pain
- less risk of postop hypoxemia
- faster recovery and discharge from hospital
thoracoscopic surgery types of anesthesia
- local
- regional
- GA
- two lung ventilation
- OLV
preop planning for thoracoscopic procedures
- discuss pain management options with patient
- PCA for chest tube pain
- NSAIDs usually sufficient
- consult with surgeon about likelihood of proceeding to thoractomy
- otherwise preop considerations are same as thoracotomy
intraoperative anesthetic considerations for thoracoscopic procedures
- GA/OLV with DLT or bronchial blocker (deflate ASAP because with robot and insufflation much more limited space)
- infiltration with LA by surgeon prior to placement of ports
- lateral decub
- routine monitors
- minimum of one large bore PIV (better to have two)
- a line usually placed
- end of proceudre lung is suctioned and gently re-inflated; change DLT to standard ETT if patient cannot be extubated
- chest tube placed prior to closing
intraoperative complications during VATS
- CO2 insufflation used to improve surgical visualization (gas embolism, hemodynamic compromise)
- tension pneumo
- hemorrhage
- perforation of diaphragm or other organs
- complications related to positioning and DLT
mediastinoscopy
- procedure is usually performed with lymph node or tissue biopsy to either establish a diagnosis or determine the resectability of an intrathoracic tumor
- performed through small transverse incision just above suprasternal notch
- blunt dissection along pre-tracheal fascia permits biospy of paratracheal lymph nodes to the level of the carina
mediastinoscopy anesthetic considerations
- compression to innominate artery can cause poor flow to the right carotid –> poor cerebral perfusion
- central airway obstruction due to compression of the trachea may occur during induction of anesthesia or during the manipulation of the mediastinoscope near the trachea
- technique –> GA with ETT and CV
- moniotr a line/pulse ox on R arm to monitor innominate artery (if absent waveform ask surgeon to reposition scope)
- BP on left
what does the innominate artery supply?
- R common carotid
- R arm
S/S associated with mediastinal masses
- most are asymptomatic and discovered incidentally CXR
- symptomatic masses are usually malignant are large with extensive involvement –> airway obstruction, impaired cerebral circulation, distortion of anatomy
- frequently associated with systemic syndromes
- other s/s = cough, dyspnea, stridor, jugular distention, exaggerated changes in BP associated with postural changes
syndromes associated with mediastinal tumors
- Myasthenia gravis (thymoma)
- cushing’s (thymoma, carcinoid)
- hypercalcemia (parathyroid adenoma)
- hypertension (pheochromocytoma)
- myasthenic syndrome (lung cancer)
SVC syndrome
- progressive mediastinal tumor growth may result in compression of the SVC
- obstructs venous drainage in the upper thorax
SVC Syndrome clinical manifestations
- caval obstructions –> venous distention in neck, thorax, upper extremities
- edema of face, conjunctiva, neck and upper chest
- external edema may be accompanied by edema of the mouth, larynx, and associated with severe airway obstruction
- cyanosis - mucosal edema and direct compression can severely compromise airflow in trachea
- CO may be severely depressed due to impeded venous return from upper body or by direct mechanical compression on the heart from tumor
- venous backflow into upper extremity IV lines
- evidence of increased ICP
relative contraindications to mediastinoscopy
- SVC syndrome
- previous mediastinoscopy
- obstruction and distortion of airway
- impaired cerebral circulation
- myasthenic syndrome
absolute contraindications to mediastinoscopy
- inoperability
- coagulopathy
- thoracic aortic aneurysm
preop considerations for mediastinoscopy
- assess for evidence of airway compromise –> dyspnea, tachypnea, tracheal compression or deviation
- preop CXR and CT scan are essential to assess size and location of tumor and to evaluate tracheal distortion or compression
- if airway compression is present, obtain PFTs in upright and supine positions (flow-volume loops detect airway obstruction)
- may patients will favor the upright position
- assess for evidence of SVC obstruction
- worsening of symptoms may be precipitated by muscle relaxants, coughing and breath holding, position changes
mediastinoscopy monitoring
- large bore PIV x 2 may need to place in lower extremities if S/S of SVC
- monitor R radial pulse; doppler arterial pressure line, pulse oximeter on R hand finger
- BP cuff monitoring in L arm
- PNS
mediastinoscopy complications
- acute airway obstruction (use reinforced tube)
- anticipate difficulties with intubation and ventilation (have many ETTs available, establish ability to ventilate before muscle relaxation, muscle relaxation intraop or to prevent coughing or straining)
- venous air embolism (HOB often 30 degrees elevation)
- mediastinal hemorrhage
anesthetic management of mediastinoscopy
- deep anesthesia to blunt autonomic reflexes
- monitor for pneumo, avoid N2O
- monitor for instrument pressure against innominate, T subclavian or R carotid arteries (loss of distal pulse, postop neuro deficits)
- observe postop respiratory status closely
- vagally-mediated reflex bradycardia from compression of trachea or great vessels
what to do if airway obstruction or SVC obstruction occur
- place patient in lateral, reverse T, prone or high fowlers position
- may cause mass to shift away from the trachea or SVC and relieve the obstruction
emergence for mediastinoscopy
- prior to extubation have full TOF, full return of airway reflexes, patients with SVC syndrome must be fully awake as they can easily obstruction
- postop CXR on all patients to rule out pneumo
major complications of mediastinoscopy
- hemorrhage
- pneumothorax
- RLN injury
- phrenic nerve injury/Left hemiparesis
- esophageal injury
- air embolism
- dysrhythmias
