Respiratory
A 36 year old man is brought to the Emergency Department by paramedics. He was found at home by his family unresponsive in bed. He has a history of epilepsy and heavy alcohol consumption. He is not compliant with his epilepsy medication. His observations are recorded as:
- Heart rate: 89 beats per minute
- Blood pressure: 126/87 mmHg
- Respiratory rate: 24 breaths per minute
- Temperature: 37.6°C
- Glasgow coma score: 9/15
On examination you note a strong smell of alcohol and urine. On auscultation you find harsh breath sounds on the right side of the chest. A chest x-ray shows a right sided opacification with air bronchograms, obscuring the right heart border. What is the most likely diagnosis?
Answer:
This patient has a pneumonia, likely to be secondary to aspiration. The patient has a couple of risk factors for aspirating, including his alcohol use and his epilepsy that is poorly controlled.Pulmonary Aspiration
Respiratory
Last Updated: 8th September 2021
Aspiration is the inhalation of liquid or solid particles, particularly food, into the airways beyond the vocal cords. It can be categorised as aspiration pneumonitis or aspiration pneumonia. Aspiration pneumonitis is a chemical injury after aspiration of gastric contents. Aspiration pneumonia is an infectious process secondary to aspiration of orogastric contents colonised with bacteria.
Risk factors
Pulmonary aspiration usually occurs in patients with altered level of consciousness, dysphagia, or impaired cough reflex.
Aspiration of food and liquids is more common in:
- Patients with oropharyngeal dysphagia, especially when it is due to stroke or cervical spine surgery
- Older patients (>70 years)
- Patients who are taking sedative medications
- Patients being fed by a gastric tube
- Patients who depend on others for feeding
- Current smokers
- Patients taking >8 medications
- Pregnant women
Patients with risk factors for aspiration should undergo a bedside clinical examination before feeding.
Anaesthesia-related aspiration of gastric contents can be prevented by identifying patients susceptible to vomiting and reflux, minimising gastric contents before surgery, minimising emetic stimuli, and avoiding complete loss of protective reflexes from over-sedation.
Clinical features
The diagnosis of acute aspiration is primarily by history, bearing in mind the presence of risk factors, with confirmation when necessary by imaging studies.
A sudden onset of fever, cough, dyspnoea, wheezing, or cyanosis in at-risk patients means that aspiration is likely. Crackles on lung auscultation is common after aspiration of gastric contents, occurring in 72% of cases. Aspiration in the setting of general anaesthesia or in the intensive care unit is also common. It may be silent, or may manifest clinically by a combination of bronchospasm, hypoxia, cough, dyspnoea, fever, and even respiratory failure from non-cardiogenic pulmonary oedema.
Investigations
- Chest x-ray
- When aspiration of gastric contents results in aspiration pneumonitis or pneumonia, the chest x-ray reveals patchy, bilateral airspace consolidations with a perihilar and basilar distribution.
- The right lung may be involved more frequently because of the obtuse angle between the trachea and the right main bronchus.
- Chest x-ray findings of aspiration pneumonitis usually develop within 2 hours of aspiration and sometimes resolve quickly. However, the aspiration pneumonia opacities can develop days later and can take weeks to resolve.
- CT chest
- Although chest x-ray is sufficient in most cases of aspiration, a CT chest should be ordered if foreign body aspiration is suspected (to plan extraction) or if the patient fails to improve with initial therapy (to rule out empyema or lung abscess).
- Bronchoscopy
- Bronchoscopy is indicated if aspirated material is particulate or if there is radiographic evidence of lobar or segmental collapse, in order to clear the airway. In addition, bronchoscopy can be used to collect quantitative cultures on bronchoalveolar lavage or protected specimen brush, which can be used to guide antibiotic therapy, particularly in patients who fail to respond to empirical antibiotic treatment.
Management
- Patients that aspirate will often have a reduced level of consciousness and require close observation for at least 48 hours, either in hospital or in another care facility.
- Patients with recent suspected or witnessed aspiration of gastric contents should, whenever possible, be immediately placed semi-prone and tilted to a 30° head-down position. This positions the larynx at a higher level than the oropharynx and allows the gastric content to drain externally. The oropharynx should be gently suctioned, taking care to avoid initiating a gag reflex that may worsen aspiration.
- Once the oropharynx has been suctioned, the airway should be secured by endotracheal intubation if the patient is deemed to be at risk of further aspiration, is unable to protect their own airway (regurgitation, poor cough reflex), or shows signs of respiratory failure (tachypnoea, dyspnoea, confusion, cyanosis).
- Once the airway is secured, a nasogastric tube should be inserted to empty the stomach, and where possible the patient can be tilted to a 45° head-up position to help prevent further aspiration.
- If a substantial amount of gastric content (>20-25 mL in an adult) is likely to have been aspirated, prompt (within a few hours) bronchoscopy and suctioning can remove aspirated gastric fluid and solid material from the central airways, thereby helping to reduce inflammatory reaction, prevent lung collapse, and lessen the risk of subsequent infection.
- Gastric aspirate is sterile under normal conditions due to the low pH, so bacterial infection does not have an important role in the early stages of acute lung injury. Consequently, immediate routine antibiotic therapy is not recommended for aspiration pneumonitis.
- Empirical therapy with broad-spectrum antibiotics is recommended if the pneumonitis does not resolve 48 hours after aspiration, as this suggests the development of bacterial pneumonia. Clinical features suggestive of aspiration pneumonia include persistent leucocytosis, fever, and infiltrates, >48 hours after a confirmed or probable aspiration event. A repeat chest x-ray should be obtained if non-resolution is suspected clinically. Sputum and/or bronchoalveolar lavage culture and blood cultures should be obtained to guide antibiotic therapy.
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
