Anesthesia for Thoracic Surgery 1 Flashcards
Challenges associated with thoracic surgery include:
physiologic derangements caused by lateral decubitus position
problem of an open pneumothorax
surgical manipulations interfering with pulmonary and heart function
risk of rapid, massive bleeding
necessity for one-lung ventilation
The lateral decubitus positioning provides
optimal surgical access for many thoracic procedures
The lateral decubitus positioning has the potential for
significant alteration in normal respiratory physiology
disrupts ventilation/perfusion relationships
Complications with lateral decubitus positioning includes:
brachial plexus & peroneal nerve injury
monocular blindness–> minimize pressure on dependent eye
outer ear ischemia–> flat or in donut
axillary artery compression
Pulmonary & CV complications with lateral decubitus positioning includes:
coughing, tachycardia, hypertension during turn to lateral decubitus position
hypotension from blood pooling in dependent portions
V/Q mismatching= hypoxemia
interstitial pulmonary edema of dependent lung
When the table is flexed,
ensure position of tube hasn’t moved because if it is tight, it can be pulled out
Describe ventilation and perfusion in the awake patient who is upright, has spontaneous respirations & a closed chest:
apex of lungs are maximally dilated
most ventilation occurs at the base of the lungs
perfusion also favors the base of the lungs
V/Q matching is preserved during spontaneous respirations
V/Q matching is best preserved in zone 3
Describe ventilation & perfusion in the lateral decubitus position in the spontaneously breathing, closed chest patient.
V/Q matching is preserved
dependent lung receives more ventilation and perfusion than the upper lung (non-dependent lung)
non-dependent lung is now zone 1
Factors that cause diaphragm displacement include:
surgical position
paralysis
supine position
induction of anesthesia
Describe the V/Q matching in the anesthetize patient who is in the lateral decubitus position, paralyzed and has a closed chest.
Positive pressure ventilation decrease in FRC V/Q mismatching dependent lung= greater perfusion non-dependent lung= greater ventilation
Describe the V/Q matching for the anesthetized patient in the lateral decubitus position with an open chest
V/Q mismatching
perfusion remains greater in dependent lung
upper lung collapse leads to progressive hypoxemia–> mediastinal shift impedes ventilation to lower lung, paradoxical respirations
Describe V/Q matching of the anesthetized patient in the lateral decubitus position, paralyzed with open chest (2 lung ventilation).
Positive pressure ventilation
may worse V/Q mismatching
ventilation greater in non-dependent lung
perfusion greater in dependent lung
The following have an effect on V/Q matching:
positioning
open chest- mediastinal shift
anesthesia with paralysis
Describe the V/Q match in the lateral position.
non-dependent V> Q
Dependent V
Hypoxic pulmonary vasoconstriction works by
diverting blood away from the hypoxic regions of the lung
decrease blood flow to the non-ventilated lung
Hypoxic pulmonary vasoconstriction ________ shunt
decreases
Hypoxic pulmonary vasoconstriction helps improve
arterial oxygen content improving hypoxemia
Describe blood flow distribution of the nondependent & dependent lungs in the lateral decubitus position.
Nondependent: 40%
Dependent: 60%
Factors that inhibit HPV include:
high pulmonary vascular resistance (increased PAP, volume overload, mitral stenosis) hypocapnia high or very low mixed venous PO2 vasodilators pulmonary infection inhalation anesthetics
Vasodilators that inhibit HPV include
nitroglycerin
nitroprusside
beta agonists (dobutamine)
calcium channel blockers
1 Mac of anesthetic causes a ________ in shunting
5% increase
One lung ventilation blood flow with hypoxic pulmonary vasoconstriction is
20% in nondependent
80% in dependent
1 MAC of isoflurane ______ hypoxic pulmonary vasoconstriction by ____
inhibits by 21%
One lung anesthesia is beneficial for
better operating conditions with collapse of the disease lung
facilitates access to the aorta & esophagus
prevents cross-contamination with abscess, secretions, bblood
prevents loss of anesthetic gases with bronchopleural fistula
Relative contraindications for one-lung anesthesia include
difficult airway with poor visualization of the larynx
lesion in bronchial airway precluding bronchial intubation
Absolute indications for one-lung ventilation include:
pulmonary infection copious bleeding on one side bronchopulmonary fistula bronchial rupture large lung cyst bronchopleural lavage
Relative indications for one-lung ventilation include
thoracic aortic aneurysm pneumonectomy lobectomy thoracotomy; thoracoscopy subsegmental resections esophageal surgery
Techniques for achieving one lung ventilation include
double-lumen endotracheal tubes bronchial blocker (used with standard single-lumen endotracheal tube) single-lumen endotracheal tube
Shared characteristics of double-lumen endotracheal tubes include
longer bronchial lumen which enters either the right or left mainstem bronchus
shorter tracheal lumen remaining in the distal trachea
performed curve that allows preferential entry into the left or right side
separate bronchial and tracheal cuffs
tubes specifically designed for L or R side due to differences in anatomy
Describe the anatomic considerations of the adult trachea for DLT
11-12 cm long
begins at C6 (cricoid cartilage)
bifurcates at the sternomanubrial joint (T5)
Describe anatomic considerations for the right bronchus when using the double lumen tube.
wider
diverges away from trachea at 20-25 angle
orifice of RUL sits only 1 to 2 cm to carina
Describe anatomic considerations for DLT for the left bronchus.
narrower
diverges away from trachea at 40-45 degree angle
orifice of LUL sits about 5 cm distal to carina
The stylet goes through the ________ of the double lumen tube
bronchial side
The ______ is more difficult to place for the double lumen tube.
the right
The best predictor of DLT size is
patient height
For someone who is 4’6” to 5’3” the size of the DLT is
35-37 french
For someone who is 5’3” to 5’7”, the DLT size is
37 or 39 FR- most commonly used size
For someone who is taller than 5’7”, the DLT used is a
41 FR
Proper size of the DLT allows for
1-2 mm smaller than patients left bronchus to allow for space of bronchial cuff
Describe the insertion technique of the double lumen tube.
laryngoscopy with curved blade provides optimal space to place DLT
DLT is passed with the distal curvature concave anteriorly, then rotated 90 degree towards the size that is to be intubated after the tip enters the larynx
advance DLT until resistances felt
confirm correct placement
The average insertion depth of the DLT is
28-29 cm at teeth
Correct position of the double lumen tube when one tube is clamped includes:
ipsilateral breath sounds disappear
ipsilateral hemothorax does not move
no change in moisture
contralateral breath sounds remain
contralateral hemothorax rises & falls
contralateral respiratory gas moisture disappears on inhalation and reappears on exhalation
breathing bag has the expected compliance for one-lung ventilation
The protocol for checking placement includes:
inflate tracheal cuff check for bilateral breath sounds inflate bronchial cuff clamp tracheal lumen check for unilateral LEFT breath sounds unclamp tracheal lumen & clamp bronchial lumen check for unilateral RIGHT breath sounds fiberoptic confirmation (check both supine & after LDP)
The tracheal cuff should be inflated to
5-10 mL of air
The bronchial cuff should be inflated with
1-2 mL of air
When checking for bilateral breath sounds, if unilateral breath sounds are heard, this indicates
tube too far down & tracheal opening is endobronchial
When checking for unilateral LEFT breath sounds, persistence of right-sided breath sounds indicate
bronchial opening still in trachea & tube should be advanced
When checking for unilateral LEFT breath sounds, if unilateral right sided breath sounds are heard instead, this indicates
incorrect entry of the tube into right bronchus
