Anaesthesia for Thoracic Surgery Flashcards by Em Chambers

what is the main anaesthetic consideration when opening the thorax?

ventilation

How well did you know this?

Not at all

Perfectly

why is ventilation a concern when opening the thorax?

opening the thorax removes negative pressure in the pleural space

How well did you know this?

Not at all

Perfectly

what is the impact of the removal of negative pressure through opening the thorax?

when the chest wall expands on inhalation there is little or no air entry into the lungs as the pressure in the lungs is the same as atmospheric pressure
ventilation is inadequate and gas exchange impaired

How well did you know this?

Not at all

Perfectly

what is needed during thoracic surgery to ensure adequate ventilation?

manual or automatic IPPV throughout surgery

How well did you know this?

Not at all

Perfectly

what is caused by opening the thoracic cavity?

atelectasis

How well did you know this?

Not at all

Perfectly

what is decreased by atelectasis?

total lung capacity
vital capacity
functional residual capacity

How well did you know this?

Not at all

Perfectly

what is commonly seen during thoracic surgery even with IPPV?

atelectasis

How well did you know this?

Not at all

Perfectly

what can worsen atelectasis during thoracic surgery?

packing off lung lobes
manipulation of blood vessels altering supply
leak testing
pathology patient was admitted with

How well did you know this?

Not at all

Perfectly

what is functional residual lung capacity?

gas left in the lungs after expiration

How well did you know this?

Not at all

Perfectly

what is the role of functional residual capacity?

reserve gas exchange occurs between breaths

How well did you know this?

Not at all

Perfectly

which surgical approach to the thorax is more painful?

sternotomy - more retraction required and more muscle damage than thoracotomy

How well did you know this?

Not at all

Perfectly

what thoracic surgical approach is least painful?

thoracoscopy

How well did you know this?

Not at all

Perfectly

what must be considered when patients are undergoing thoracoscopy?

large volume of CO2 insufflation
lungs can become compressed

How well did you know this?

Not at all

Perfectly

when may ventilation be required from the start of abdominal surgery?

diaphragmatic hernia repair

How well did you know this?

Not at all

Perfectly

why is thoracotomy so painful?

skin incision
nerve damage
retraction of ribs to allow access leading to muscle damage
inflammation at surgical site

How well did you know this?

Not at all

Perfectly

what can be caused by poor analgesia during thoracic surgery?

hyperalgesia

How well did you know this?

Not at all

Perfectly

what is the impact on patient ventilation following thoracic surgery?

ventilation less effective as lung inflation is compromised due to pain making patient unwilling to move their chest

How well did you know this?

Not at all

Perfectly

what are the main reasons for thoracic surgery?

respiratory system
cardiovascular
oesophageal FB
thoracic duct ligation

How well did you know this?

Not at all

Perfectly

what are the main respiratory system reasons for opening the thorax?

lung lobe torsion
bulla
neoplasia
abscess

How well did you know this?

Not at all

Perfectly

what are the main considerations for thoracic surgery involving the respiratory system?

pre existing pneumothorax
hypoventilation
hypoxaemia
pre-disposed to decompensation
pathology already compromising respiration

How well did you know this?

Not at all

Perfectly

what are the main cardiovascular system reasons for opening the thorax?

patent ductus arteriosus
persistent right aortic arch
pericardectomy
heart surgery

How well did you know this?

Not at all

Perfectly

what are the main considerations for thoracic surgery involving the cardiovascular system?

CVS changes due to primary lesion or surgical manipulation
bleeding
hypotension
risk of arrhythmias

How well did you know this?

Not at all

Perfectly

what are the main considerations for persistent right aortic arch?

paediatric
present with regurgitation
risk of aspiration
may be malnourished

How well did you know this?

Not at all

Perfectly

what should you be aware of during PDA closure?

may be significant changes
bradycardia and hypertension

How well did you know this?

Not at all

Perfectly

what are the main considerations for opening the thorax for non-respiratory/CVS reasons?

contamination risk infection pain risk of aspiration risk of regurgitation sepsis

what is vital for thoracic surgery?

preparation

what is involved in preparation for thoracic surgery?

blood type check blood availability hypotension treatment plan (drugs/fluids) pre oxygenation check ventilator or IPPV facilities ensure monitoring equipment ready analgesia plan

what must happen before thoracic surgery?

patient is as stable as possible

how may patients be stabilised for thoracic surgery?

chest drainage pre-oxygenation fluids

what must be considered about pre-oxygenation?

must not cause further stress as may worsen respiratory function method should be best available for patient

what is the aim with all anaesthetic drugs for thoracic surgery?

minimal CVS depression analgesia

what drug type might be avoided in thoracic surgery patients?

alpha-2 agonists ACP

what drugs may likely be needed during thoracic surgery?

inotropes (e.g. noradrenaline) additional analgesia infusions (e.g. fentanyl)

what is etomidate used for?

induction CRI

is etomidate licensed for animals in the UK?

what type of drug is etomidate?

IV ultra short acting nonbarbituate

what are the advantages of etomidate?

minimal CVS depression

what are the disadvantages of etomidate?

poor quality of induction unless premed is very good or the animal is very sick

what is the main benefit of fentanyl during anaesthesia?

MAC sparing

what is the benefit of giving MAC sparing drugs such as fentanyl during anaesthesia?

reduce CVS/respiratory system depression seen with volatile anaesthetic agents as the level can be reduced

what is the speed of onset of action of fentanyl?

within 5 minutes

what is the duration of analgesic effect of fentanyl?

20 minutes (lowest dose) to 40 minutes (highest dose)

what is the benefit of one lung ventilation?

isolation of one lung for ventilation if pathology only affects one increases surgical exposure

what are the options available for one lung ventilation?

single lumen ET tube advanced into one bronchus double lumen tube endobronchial blocker

what is the main disadvantage of one lung ventilation?

placement difficult must be very careful moving patients with endobronchial or double lumen tubes placed as trauma is possible

what is the benefit of a single lumen ET tube advanced into one bronchus for one lung ventilation?

easy (er)

what is the disadvantage of a single lumen ET tube advanced into one bronchus for one lung ventilation?

may not achieve effective one lung ventilation risk of contamination between lungs difficult in large dogs (>20kg) due to tube length

what is the benefit of endobronchial blockers for one lung ventilation?

effective

what is the disadvantage of endobronchial blockers for one lung ventilation?

bronchoscope required to place needs skill and training to place expensive

what is the benefit of double lumen tubes for one lung ventilation?

can be done blind

what is the benefit of double lumen tubes for one lung ventilation?

can be placed blind

what is the disadvantage of double lumen tubes for one lung ventilation?

bulky and difficult to place not achievable in dogs >20-25kg due to tube length

how is an endobronchial blocker placed?

advanced through single lumen ET tube

what must be followed when using endobronchial blockers?

stated inflation volumes for the cuff to prevent bronchial wall damage

when should an endobronchial cuff be inflated?

only when one lung ventilation is needed

what should be avoided once an endobronchial blocker is placed?

movement of patient as this can cause the blocker to dislodge

what must be avoided once an endobronchial blocker is placed and the cuff inflated?

movement of the patient due to the risk of bronchial wall damage

why is the size of the patient for double lumen tubes limited?

size of human tubes

what is the best ventilation option for thoracic anaesthesia?

mechanical make do with manual if necessary

what is the ventilator setting range for tidal volume?

10-15ml/kg (maybe 8-10ml/kg for cats)

what is the ventilator setting range for tidal volume during thoracic surgery to aid visualisation?

6ml/kg

how can you judge tidal volume settings are correct?

observe thorax adapt to monitoring

what is the ventilator setting range for Peak inspiratory pressure?

8-12 cm H2O

when may PIP settings be altered?

if open or closed thorax increase if recruitment

what is the ventilator setting range for respiratory rate?

10-30 bpm

when may respiratory rate settings be altered during ventilation?

adapt to animal increase if tidal volume reduced

what is the ventilator setting range for I:E ratio?

1:2 max

what should I:E ratio be adapted to?

does IPPV require NMBA?

not necessary in most cases

what are the main issues associated with ventilation?

CVS depression trauma re-expansion pulmonary oedema

why can ventilation lead to CVS depression?

decreased venous return

how can the CVS depressive effects of ventilation be reduced?

limit I:E ratio to at least 1:2

how can the risk of trauma during ventilation be reduced?

limit pressure/volume applied to the chest

how can re-expansion pulmonary of ventilation be reduced?

be careful not to over expan lungs at the end of surgery - allow them to reopen over time

what monitoring techniques will be used for anaesthesia for thoracic surgery?

blood gas capnography oxygen monitoring as well as standard

what must you be aware of when using capnography with an open thorax?

EtCO2 unlikely to reflect PaCO2

why are there differences between EtCO2 and PaCO2 in animals with an open thorax?

altered ventilation and perfusion relationships in different areas of the lungs

how can PaCO2 be used to inform EtCO2 in patients with an open thorax?

PaCO2 reading obtained from art line calculate difference between PaCO2 and EtCO2 use this to inform required EtCO2 level to keep PaCO2 between 35-45mmHg

how should oxygen levels be monitored during thoracic surgery?

SpO2 as a minimum PaO2 if possible

how is hypoxaemia detected during surgery?

PaO2 via art line

how can hypoxaemia be managed?

check patient on 100% FiO2 check ET tube patency ensure CVS function optimised

how can you alter ventilation to manage hypoxaemia?

switch to manual IPPV and give larger breaths alveolar recruitment manoeuvre introduce PEEP reduce Fi inhaled agent re-expand collapsed lung - communicate with surgeon

what may affect ET tube patency during thoracic surgery?

endobronchial blocker may have become dislodged and blocked the ET tube lumen secretions may block tube lumen

how can you ensure CVS function is optimised during thoracic surgery?

ensure anaesthetic depth is appropriate ensure circulating blood volume is adequate (IVFT?) confirm surgeon isn't decreasing venous return

what is the alveolar recruitment manoeuvre?

temporary airway pressure is increased during mechanical ventilation so as to open up the collapsed alveoli

what pressure is needed for a alveolar recruitment manoeuvre?

30 cmH2O airway pressure for a breath

what are the main supportive therapies used for thoracic surgery patients?

IVFT hypothermia management

what analgesia is needed for a thoracic surgery patient?

combination of local and systemic techniques

what drug types may be used for analgesia following thoracic surgery?

full mu agonists LA NSAIDs

what full mu agonists may be used for thoracic surgery?

methadone fentanyl morphine epidural

what local anaesthetic techniques may be used for thoracic surgery?

intercostal nerve block (lateral thoracotomy) LA down chest drain at end of surgery LA infiltration around sternotomy site

why must NSAIDs be used with caution post-op?

if patient has had unstable BP throughout NSAIDs should not be given due to prostaglandin effects

when should the end of IPPV be timed with during thoracic surgery?

chest closure and drainage as won't be able to breathe spontaneously before this

describe the process of weaning from the ventilator

turn off ventilator support respiration with IPPV gradually decrease IPPV to allow PaCO2 to rise decrease anaesthetic and analgesic drugs reverse NMBA, if used, before stopping IPPV completely continue until breathing spontaneously

what techniques can be used to aid pulmonary re-expansion?

alveolar recruitment manoeuvre

when is an alveolar recruitment manoeuvre useful?

following lavage atelactasis

when is the risk of re-expansion pulmonary oedema higher?

if lungs collapsed for more than 12 hours

what is a vital part of the recovery process from thoracic surgery?

weaning patient on to room air oxygen supplementation if needed IVFT

what monitoring is needed for patients in recovery from thoracic surgery?

pulse ox assess chest drain for air, blood or fluid

what should be done if the patient isn't saturating adequately in recovery?

assess chest drain for air, blood or fluid supplement O2

when can oxygen toxicity occur?

>6 hours on high FiO2

when may a blood transfusion be necessary?

if >20% blood loss - check PCV

how can you check if a patient is actively bleeding from a chest drain?

PCV of fluid from chest drain

what are the key factors involved in anaesthesia for thoracic surgery?

IPPV** pain management basic support (temp, fluids) good anaesthesia protocol: MAC sparing and good analgesia