Chapters 154-160 Thoracic anesthesia Flashcards
Where is the highest amount of resistance in the airways
80% of the airway resistance comes from the large central airways; 20% from the peripheral bronchioles
What are the parasympathic receptors that regulate bronchial tone?
M1 and M3 enhance parasympathetic tone and M2 is inhibitory
What do volatile anesthetics do to help attenuate bronchospasm?
1) depress airway reactivity
2) depress bronchoconstriction by directly relaxing bronchiolar smooth muscle
In a severe asthmatic what do you need to be considered about when using neuromuscular blockade?
When you reverse a patient the muscarinic action of cholinaterase inhibitors can precipitate a bronchospasm. You should use large dose of anticholinergics in this setting (atropine, glycopyrrlate)
Why is sux a relative contraindication in a patient with carcinoid
it maybe causes release of active tumor agents by increasing the intrabdominal pressure; does not have any intrinsic releasing properties
Why do you want to give a large dose of antimuscarinic drugs not a small dose when trying to treat bronchospasm?
because antimuscarinic drugs are nonselective, at low doses they may block the beneficial effects of B2 more than blocking the M1 an M3 bronchoconstricting effects.
What regional technique can you use to block the gag reflex?
Use bilateral glossopharyngeal nerve blocks. 3 mL of 2% lidocaine into the midpoint of bilateral posterior tonsillar pillars.
During apnea, how much with Co2 go up in the first minute and thereafter?
PCO2 increases 4-6 mmHg in the first minute and then 2-4 every minute thereafter
What are some absolute indications for DLT?
1) isolation of 1 lung to prevent soilage (bleeding, infection)
2) control ventilation in setting of brochopleural fistula
3) with surgical opening of major airway’
4) unilateral lavage for pulmonary alveolar proteinosis
5) VATS or minimally invasive cardiac surgery
What are advantages to using a DLT?
1) ease of placement (relatively)
2) rapid conversion of ventilation 1 to 2 lungs
3) able to suction both lungs
4) CPAP to nonventilated lung
Why are placement of right sided DLT more difficult?
the left main bronchus is 5.0 cm until the bifurcation. On the right side the upper lobe departs within 2 cm of the main carina.
In the lateral position which lung is better ventilated and which lung is better perfused?
Dependent lung is better perfused because of gravity, but because the dependent lung is compressed by the mediastinum and abdominal contents, the nondependent lung is better ventilated.
What do systemic vasodilators do to hypoxic pulmonary vasoconstriction?
nitroglycerin, calcium channel blocks, beta blockers will inhibit HPV
Why do you need to be conserned about PRV during single lung ventilation?
the PVR of the dependent lung during OLV determines the ability of that lung to accept the flow from the nondependent lung.
Why might after lung resection would you see white out in the dependent lung after surgery?
pericapillary transudate in the dependent lung causes collapsing alveoli and increases PVR in that lung
What steps should you take if your patient starts to desaturation during OLV?
1) make sure FiO2 is 1.0
2) recheck tube with fiberoptic scope
3) CPAP to non-dependent lung
4) PEEP to dependent lung
5) ask surgery to ligate the pulmonary artery if that is part of the surgical procedure
6) intermittent bilateral ventilation
Why can adding PEEP to non-dependent lung actually be delirious?
PEEP to dependent lung can cause small intralveolar vellels to collapse, increase PVR and shunt more blood to the non-dependent lung
What are different techniques that can be utilized for positive pressure ventilation in the setting of bronchopulmonary fistulas to reduce the trans-fistula gas flow?
SLT- increased RR, low TV, increase inspiratory time, no PEEP
timed occlusion of the chest tube during inspiration
SLT with selective mainstem bronchus intubation
DLT
DLT with different ventilator for each lung
Bronchial blocker
HFO
What are Pros and cons of using SLT with bronchopulmonary fistula?
Pro- easy
Con- only useful with small airleak, difficult to keep airway pressures low
What are Pros and cons of using time occlusion of the chest tube with inspiration with bronchopulmonary fistula?
Pro- increases pleural pressure during inspiration to decrease the pressure gradient; can be added to other technique
Con- requires special tools
What are Pros and cons of using DLT with different ventilators for each lung with bronchopulmonary fistula?
Pro- protects other lung from infection, allow for optimal ventilatory mode for each lung, can be combined with bronchial blocker or HFO
Con- complex, may be difficult to ventilate disease lung while minimizing TV loss
What are Pros and cons of using bronchial blocker with bronchopulmonary fistula?
Pro- highly selective isolation, maximizes good lung to be ventilated
Con- requires skills, can be dislodged
In high frequency jet ventilation- what is active- inspiration, expiration or BOTH?
inspiration- active
expiration- passive
In high frequency osillation- what is active- inspiration, expiration or BOTH?
inspiration and expiration are active processes.
