Aspiration syndrome: prevention and emergency intervention

By Cristiano Antonino On Jan 21, 2022

Aspiration syndrome in most cases is a sudden entry of acidic gastric contents into the respiratory tract (aspiration), causing a burn of the airways and often accompanied by the development of a critical condition in the patient

This life-threatening complication was first described by S.L. Mendelssohn in 1946 as an emergency due to massive aspiration of gastric contents in women giving birth under general anaesthesia.

Although more than 7 decades have passed since then, many questions regarding the prevention, emergency diagnosis and treatment of the syndrome remain unresolved, as evidenced by the high mortality rate of ≥40-50% [4].

Aspiration syndrome: aetiology and pathogenesis

The development of the syndrome is based on aspiration of gastric contents, which leads to chemical burn of the airways and alveoli following exposure to hydrochloric acid with the properties of a strong acid, as well as obstruction of the airways by vomiting.

An obstructive form (asphyxia) of acute respiratory failure develops with the possibility of a fatal outcome within minutes, less often – hours and days.

It is believed that 20-30 ml of gastric juice, which has a low pH, is sufficient for the development of Mendelssohn syndrome to enter the respiratory tract.

A chemical burn of the mucous membrane of the respiratory tract is accompanied by damage to the epithelium of the trachea, bronchi, bronchioles, walls of the alveoli and the endothelium of the pulmonary capillaries.

The degree of harmful effect depends directly on the acidity and the amount of gastric juice aspirated.

As a result of an acid burn, extravasation of the plasma portion of the blood into the pulmonary interstitium, as well as into the cavity of the alveoli, occurs, leading to pulmonary oedema and the development of acute respiratory distress syndrome.

Increased oedema of the mucous membrane of the bronchi and bronchioles rapidly leads to bronchopulmonary obstruction, manifested by diffuse bronchiolospasm and overfilling of the alveoli with fluid.

Destructive changes in the lungs, manifested by damage to the epithelial and endothelial layers and oedema, can occur under the influence of gastric juice at pH 2.5-5.0, as well as when bile, gastric enzymes and other aggressive components enter the respiratory tract [1 ].

With massive aspiration of gastric or oesophageal contents, the patient can rapidly develop asphyxia, where the mechanical factor is of paramount importance; at the same time there is obstruction of the trachea, bronchi and bronchioles.

In addition to obstruction, these pulmonary macrostructures are exposed to chemical attacks, which aggravate the severity of the damage to the pulmonary tissue structures.

Aspiration of gastric contents or regurgitation of the contents of the oesophagus is possible in violation of consciousness (narcosis, intoxication, sedation, coma, horizontal position of the patient).

In all patients before emergency surgery, during childbirth, the presence of contents in the stomach is assumed, when its evacuation from the stomach to the intestine is impaired.

In patients with cardiospasm and cardiostenosis, where elective surgery under anaesthesia is usually indicated, there is almost always fluid in the oesophagus.

Aspiration is facilitated by elevated intra-abdominal and intragastric pressure, e.g. with increased volume of the abdomen due to acute stomach expansion, various types of acute intestinal obstruction, acute pancreatitis, peritonitis, etc.

Regurgitation and aspiration are often predisposed by decompensated pyloric stenosis of ulcerative and cancerous aetiology, as well as cardiac sphincter atony in patients with gastroesophageal reflux disease.

If timely decompression of the stomach and oesophagus is not performed, massive aspiration of gastric contents occurs during anaesthesia, most often during intubation, which is often accompanied by cardiac arrest.

Clinical and diagnostic features of aspiration syndrome

Aspiration syndrome is characterised by acute respiratory failure caused by laryngospasm or bronchospasm, an asthmatic condition.

These complaints usually occur after aspiration or after 1-6 hours, less often – 12 hours, manifesting as increased patient anxiety, expiratory dyspnoea, tachycardia and cyanosis.

In most cases, aspiration syndrome is accompanied by a drop in blood pressure (BP) and other disorders of the cardiovascular system, up to cardiac arrest.

There is persistent cyanosis, which is not cleared even when oxygen is supplied at a concentration of 100%.

On auscultation of the lungs, a wheeze is heard and in the lower sections – crackling rales.

With the progression of acute respiratory failure, Pa02 decreases to 35-45 mm Hg. Art., pulmonary vascular resistance increases.

With further progression of the aspiration syndrome, its clinical manifestations from the lungs correspond to the clinic of acute respiratory distress syndrome.

An X-ray examination in patients with aspiration syndrome may reveal the so-called ‘impacted lung’: areas of reduced airiness, diffuse darkening of lung tissue.

With aspiration of gastric contents that have a moderate acid or neutral reaction, the syndrome can proceed relatively favourably.

With a small amount of aspiration, it is often limited to damage to the lower lobe of the right lung, manifesting as a clinical picture of right lower lobe pneumonia.

Patient with aspiration syndrome: urgent treatment

As aspiration syndrome develops, it is necessary to quickly lower the head of the bed or operating table to drain the gastric contents from the oropharynx, then clean its cavity with electrical suction or a pad attached with forceps.

It is urgent to intubate the trachea after a preliminary examination of the glottis with a laryngoscope.

Elevating the head and torso at this point may prevent the possibility of re-inspiration.

After inserting the endotracheal tube into the trachea, its cuff must be inflated, which helps to prevent the re-entry of gastric contents into the respiratory tract.

Even within the first few minutes of aspiration, the patient requires cardiovascular resuscitation.

After intubation, it is necessary to quickly remove the aspirate from the airway using a catheter inserted through an endotracheal tube and connected to an electric aspirator.

Efforts should be made for complete removal of the aspirate from the trachea and bronchi.

Urgent suctioning of the aspirate from the trachea and bronchi, in addition to coughing by patients, is much more effective in restoring airway patency than bronchoscopy performed 30-60 minutes after suctioning.

After the emergency therapeutic measures, it is necessary to start performing bronchial lavage, for which a small amount of 0.9% sodium chloride solution (10-15 ml) is used with the addition of sodium bicarbonate (1 vial – 44 mmol). The total amount of the solution is adjusted to 30-50 ml.

During the initial period of bronchopulmonary suctioning, pure oxygen is usually used.

In the absence of effective spontaneous respiration, artificial pulmonary ventilation is performed, maintaining arterial oxygen saturation at 90-95%.

In order to eliminate shock and bronchospasm, hydrocortisone is administered intravenously at a dose of 150-200 mg or dexamethasone at a dose of 4-8 mg, 10 ml of a 2.4% aminophylline solution.

Introduction of antihistamines (30 mg diphenhydramine or 20-40 mg suprastin) is also shown, with low blood pressure – introduction of dopamine at a dose of 10-15 mcg / kg – min.

It is necessary to perform infusions of isotonic electrolytes and colloidal solutions, fresh frozen plasma (200-400 ml), 20% glucose solution (10-20 ml) and heparin at a dose of 5000-10,000 IU [4].

When the patient’s condition has stabilised, sanitisation bronchoscopy using a fibroscope inserted through an endotracheal tube is recommended.

Bronchoscopy should be completed by washing the bronchi with a glucocorticoid solution (hydrocortisone, dexamethasone) and introducing antibiotics (gentamicin, etc.).

It is necessary to maintain a coughing pulse, in which the emptying of the bronchi is more effective.

Be sure to perform vibratory chest massage, monitoring the activity of the respiratory and cardiovascular systems.

After restoration of adequate spontaneous breathing, extubation is performed.

Aspiration syndrome: prevention

Before an emergency operation, a nurse and a doctor empty the patient’s stomach with a tube.

Patients should not be given water or food before any surgery, especially when anaesthesia is required.

Be sure to perform premedication, which involves introducing atropine at a dose of 0.1 mg per 10 kg of body weight.

When performing intubation, the following measures should be observed: give the head an elevated position by pressing on the cricoid cartilage, which ensures compression of the oesophagus between the trachea and the spine (Sellick manoeuvre).

This technique is used immediately after pre-oxygenation with 100% oxygen prior to the introduction of muscle relaxants and ends after tracheal intubation and cuff inflation.

If there is a flow of gastric content into the pharynx at the time of intubation, an endotracheal tube must be inserted into the oesophagus and the cuff inflated [4].

After sanitation of the oropharynx, tracheal intubation with a spare endotracheal tube should be performed.

A probe must then be inserted into the stomach.

It should be remembered that aspiration of a small amount of gastric content may go undetected, so the lungs are completely dried during and after anaesthesia.

After extubation, the oropharynx is examined with a laryngoscope and, if necessary, debridement is performed.

Extubation is only performed when muscle tone and consciousness are restored.

Unfortunately, in all anaesthesiology and resuscitation manuals, tracheal intubation is given the main role in aspiration syndrome.

However, clinical practice shows that in this critical situation it is not possible to perform tracheal intubation in some cases for various reasons.

Therefore, this method cannot be considered a method of ‘last resort’.

In addition, aspiration syndrome may develop in persons who do not require anaesthesia (state of intoxication, leakage of the contents of the oesophagus into the oropharynx during cardiospasm, acute expansion of the stomach, etc.).

Such patients with no tracheal intubation or unsuccessful intubation must undergo cricothyroidotomy (conicotomy).

The above allows us to conclude that:

Aspiration syndrome is a serious and life-threatening condition that requires rapid tracheal intubation. If intubation is unsuccessful, the patient is shown an urgent tracheostomy and, if this is impossible, a cricothyroidotomy is indicated. Mortality in aspiration syndrome reaches ≥40-50%.
Spontaneous aspiration of gastric contents is often found in acute surgical diseases of the abdominal organs (peritonitis, acute intestinal obstruction, etc.) In patients with fluid in the stomach cavity during intubation, gastric probing, after extubation. This complication is possible with cardiospasm and cardiostenosis due to regurgitation of contents from the dilated atonic oesophagus, with cardiac sphincter insufficiency in patients with gastro-oesophageal reflux disease and in patients who have undergone total gastrectomy with formation of a dijejunoesophageal anastomosis.
Preventive measures include raising the head of the bed, placement of a nasogastric tube prior to surgery. Tracheal intubation should be performed using the Sellick manoeuvre and endotracheal tube cuff inflation.

Tracheal Intubation: When, How And Why To Create An Artificial Airway For The Patient

Endotracheal Intubation In Paediatric Patients: Devices For The Supraglottic Airways

Sedation And Analgesia: Drugs To Facilitate Intubation

Intubation Under Anaesthesia: How Does It Work?