13. Aspiration with an LMA Flashcards
You are anaesthetising a healthy young patient in the left lateral position
for an incision and drainage of a peri-anal abscess.
He is spontaneously breathing on a laryngeal mask.
Near the end of the case, the ODP notices gastric contents in the LMA tubing.
What is your immediate management?
Immediate management would be:
100% Oxygen.
Head down tilt (patient already in left lateral).
Remove LMA and clear airway with suction.
Secure airway with the aid of cricoid pressure, suxamethonium and tracheal
intubation (may be performed in lateral position or supine position, lateral
having an advantage if further aspiration, but may be technically more
difficult).
Suction trachea immediately after intubation
(before ventilation drives gastric contents deeper into the lungs).
Further management:
Insert a naso-gastric tube to empty the stomach.
If the patient is stable, surgery could be completed.
A chest X-ray should be performed looking for oedema, collapse or
consolidation.
If oxygen saturation persistently low, consider fibre-optic or rigid
bronchoscopy, particularly if aspiration of food matter is suspected.
Extubate in left lateral position if oxygen requirements permit. If not, an
intensive care bed should be requested.
Post Extubation
After extubation, the patient should be observed in recovery or in high dependency for 2–5 hours.
If the patient is asymptomatic, they may be discharged back to the ward and observed.
If symptomatic, the patient is best managed in critical care and may require CPAP or re-intubation.
Aspiration pneumonitis, pneumonia or ARDS may develop.
Prophylactic antibiotics are not indicated but infection should be treated if it occurs.
The patient should be informed about what has occurred.
You perform a chest X-ray.
This is a PA film (not marked as AP) – (the authors accept that a PA film
would not be possible in this situation but the example was all we could find!)
The alignment and penetration are good.
There is opacification of the left lower zone with loss of the left
hemidiaphragm consistent with left lower lobe consolidation.
The heart size is within normal limits (CTR <0.5).
The mediastinum is normal and there are no skeletal abnormalities.
Can you draw the bronchial tree?
Branches
Right upper:
Apical, anterior and posterior.
Right middle:
Medial and lateral.
Right lower:
Apical, anterior, posterior, medial and lateral.
Left upper:
Apical, anterior and posterior.
Lingular:
Superior and inferior.
Left lower:
Apical, anterior (with medial branch), posterior and lateral.
Where would the gastric contents go in the right lateral and supine
position?
Aspiration in the supine position may distribute to both sides,
but more frequently to the right side due to the position and size
of the right main bronchus and particularly to the upper lobe.
The right upper lobe will also be the most likely site in the right lateral position.
What is the pathogenesis and prognosis of aspiration-induced lung injury?
Mendelson described his syndrome in 1946 in obstetric patients who had
aspirated under general anaesthesia. He demonstrated the role of acid in its
pathogenesis.
Aspiration of acidic and usually sterile gastric contents into the lungs.
pH <2.5 and volume > 0.3–0.4 ml/kg (∼25 ml) thought to be required to
produce aspiration pneumonitis from animal experiments.
This has been disputed.
First phase of injury begins in seconds and peaks in the first two hours and
is due to direct tissue damage from gastric acid. Bronchospasm and
pulmonary oedema may occur.
What is the pathogenesis and prognosis of aspiration-induced lung injury?
Mendelson described his syndrome in 1946 in obstetric patients who had
aspirated under general anaesthesia. He demonstrated the role of acid in its
pathogenesis.
Aspiration of acidic and usually sterile gastric contents into the lungs.
pH <2.5 and volume > 0.3–0.4 ml/kg (∼25 ml) thought to be required to
produce aspiration pneumonitis from animal experiments.
This has been disputed.
First phase of injury begins in seconds and peaks in the first two hours and
is due to direct tissue damage from gastric acid.
Bronchospasm and pulmonary oedema may occur.
Pathogenesis
second phase
Second phase peaks at 4 to 6 hours and is marked by infiltration of
neutrophils, complement activation and acute inflammation.
While normally sterile, gastric contents may become colonized with bacteria
(often Gram-negative) in patients on antacid medications, in patients
receiving enteral feeding or in those with gastro-paresis.
In these patients early infections may contribute to lung injury.
Secondary infection and progression to ARDS may occur.
Figures
The majority of patients who aspirate under general anaesthesia remain
asymptomatic (63% in one series).
A minority will require ventilation (19%).
Death occurred in ∼6% of patients in two series of aspiration pneumonitis
cases occurring after anaesthesia and drug overdose.
Aspiration pneumonitis occurs in 1 in 3000 anaesthetics and accounts for
10%–30% of anaesthetic deaths.
