Anaesthesia for thoracic surgery Flashcards
What happens when the thorax is opened?
negative pressure is removed in the pleural space, when the chest wall expands there will be little or no air entry into the lungs as the pressure inside the lungs is the same as atmospheric pressure
What do you need to do during thoracic surgery once the thorax has been opened?
IPPV
What happens to the lungs after the thorax is opened?
total lung capacity, vital capacity and functional residual capacity is decreased
What is functional residual capacity?
gas left in the lungs after expiration
What are the specific anasesthesia considerations for thoracic surgery?
- painful
- sternotomy more painful than lateral thoracotomy
- thoracoscopy is less invasive and should be less painful
Why is thoractomy painful?
- skin incision
- nerve damage
- retraction of the ribs allow surgical access
- inflammation at the site of surgery
- leads to hyperalgesia
unwilling to move chest wall due to pain effecting ventilation on recovery
What respiratory reasons causes the need for thorax surgery?
-respiratory system reasons for opening the thorax such as lung lobe torsion, bulla, neoplasia and abscess
What considerations are there for conditions associated with thoracic surgery?
- pre-existing pneumothorax
- hypoventilation
- hypoxaemia
What cardiovascular conditions causes the need for thoracic surgery?
- patent ductus arteriosus
- persistent right aortic arch
- pericardectomy
- hear surgery
What are the considerations when performing cardiovasuclar thoracic surgery?
cardiovascular changes, bleeding, hypotension, risk of arrythmias
What is PDA? (patent ductus arteriosus)
when the foetal attachment of the heart doesn’t close and causes abnormal circulation hypotension
What other reasons other than respiratory and cardiovascular are there for thoracic surgery?
oesophageal foreign body or thoracic duct igation
What complcations can arise from oesophgeal foreign body or thoracic duct ligation surgery?
- aspiration
- regurgitation
- septic complications
How can you prepare for thoracic surgery?
- check the patients blood type
- make sure bloods are available for trasnfusion if needed
- fluids/drugsto treat hypotension
- O2;IPPV for hypoventilation
- ECG, pulse ox, arterial lines, blood pressure
- pre-oxygenate
- reduce stress
What is the aim for pre-anaesthesia?
- minimise CVS depression
- get analgesia on board
- avoid alpha2agonists, and acepromazine
- are inotropes likely indicated?
- prepare CRIs
What is an inotrope?
adrenaline
What is etomidate?
an intravenous, ultra-short acting and norbarbituate drug
What are the advantages of using etomidate as an inction agent?
minimal cardiopulmonary depression, minimal change in heart rate, mean arterial blood pressure or myocardial performance
What is fentanyl?
potentent anaesthetic sparing substance
What is the onset of action for fentanyl?
5 minutes
What is the duration of action for fentanyl?
20-40 minutes
What can you do after administering fentanyl intra-operatively?
turn down inhlation agent
Why might you need to use a double lumen endotracheal tube or a endobrachial blocker?
if a pathology only affects one lung
What are the disadvantages of using a single lumen ET tube advanced into one bronchus?
-may not achieve one ling ventilation
- risk of contamination between lungs
- difficult in big dogs due to tube length
What are the disadvantages of using an endobrachial blocker?
- requires a bronchoscope to place and skill/trainingrequired
- effective but expensive
What are the disadvantages of using a double lumen tube?
- tubes are bulky and can be difficult to place
- not achievable in dogs more than 20-25kg due to tube legnth
What is important to remember when using a bronchial blocker?
- stated inflation volumes for the cuff of the blocker to prevent bronchial wall damage should be followed
- only inflate the cuff when one lung ventilation is required
- avoid moving patients to decrease risk of dislodgement and causing bronchial wall damage
What should the I:E ratio be set toto prevent CVS depression?
1:2
What settings on the ventilator should be adjusted to the patient?
I:E ratio, tidal volume, respiratory rate
What should you do if VT is decreased?
increase respiratory rate
What is important to remember with capnography during thoracic surgery?
differences between ETCO2 and PaCO2 are not consistent in dogs with an open thorax due to altered ventilation and perfusion relationships
How do you detect hypoxaemia during thoracic surgery?
requires placement of an arterial catheter and is mandatory for a thoracoscopy
How do you manage hypoxaemia?
- check 100% FiO2
- check patency of ET tube such as endobrachial blocker not dislodged or secretions blocking lumen of tube
- ensure CVS function of optimised e.g depth of anaesthesia, circulating blood volume
- switch to manual ventilation so larger breaths can be given
- alveolar recrruitment manoeuvre
- reduce concentration of volitile agent
- re-expand collapsed lung
What analgesia can be used?
- local and systemic analgesia
- full Mu agonists
- epidural morphine
- intercostal nerve block
- local anaesthetic down chest drain
- NSAIDs
How would you wean off the ventilator?
- turn off ventilator and support respiration until breathes spontaneously
- decrease IPPV gradually – will allow PaCO2 to rise
- decrease anaesthetic / analgesic drugs
- reverse NMBA before stopping IPPV
