Index
It is a particular type of wheezing described as a solid musical sound of constant pitch.
This sound is heard in patients with tracheal or laryngeal obstruction.
The complete differential diagnosis of airway obstruction should be carefully considered in any patient with wheezing or stridor.
Wheezing is defined as continuous, high-pitched adventitious lung sounds. They are produced by the oscillation of opposite walls of the airways whose lumen is narrowed.
Although asthma is the most common cause of wheezing, various disease processes can cause wheezing due to airway obstruction.
This obstruction can be caused by airway edema, smooth muscle constriction, increased secretions, vascular congestion, mass lesions, scarring, or foreign bodies.
The characteristic sound and associated features are seen when stenosis is present at the supraglottic, glottic, subglottic, or tracheal levels.
Importantly, stridor is a symptom, not a diagnosis, so further investigation is required to identify the underlying cause.
Causes of stridor
Stridor is an abnormal inspiratory sound and is a sign of airway obstruction that requires immediate attention.
Stridor can be caused by a mass or foreign body in the upper airway or laryngeal edema.
Laryngeal edema after endotracheal extubation is the most likely cause of stridor in an adult patient in the ICU.
Differential diagnosis
The main differentials to consider in a case of stridor are:
- Stertor: a high-pitched snoring sound that results from stenosis between the nasopharynx and the supraglottic regions.
- Wheezing is a polyphonic sound of the expiratory airways caused by narrowing the lower airways.
Stridor itself is a red flag, and an investigation of the cause should be done as soon as possible.
Even more worrisome is when the volume of the stridor sound decreases, as this may mean that the patient is getting the lungs displacing tired and less air.
Vital signs to evaluate for all stridor include:
- Torticollis and trismus.
- Inability to swallow and drool.
- No cough.
- Cyanosis.
- Evidence of systemic infection.
- Poor response to initial treatment.
Investigations and management
In most emergencies, the diagnosis is clinical, and the initial administration steps should be started before the results of the investigations are recovered. The final management steps will then vary between the underlying causes.
For non-urgent or chronic cases, visualization of the upper airway will generally be performed using fiberoptic nasal endoscopy as a fast and minimally invasive means to differentiate where the pathology is.
Additional imaging studies, such as computed tomography, may be used in the case of abscesses or malignant neoplasms. In contrast, bronchoscopy may be used if visualization below the vocal cords is warranted, such as suspected subglottic stenosis.
Sharp handling
For acute cases requiring urgent management, initial steps should include:
- Stabilize the patient, initiate high-flow oxygen, and alert the appropriate senior specialists (ENT and anesthesia staff).
- Try to suction secretions or clear the foreign body from the airway if it is evident.
- Give epinephrine or steroids (IV or inhaled) as needed.
- Take blood, including an ABG or cultures, if indicated.
Be prepared to perform or assist with an emergency cricothyroidotomy or intubation in emergencies.
Epiglottitis
Epiglottitis is inflammation of the epiglottis and surrounding tissues, most commonly caused by H. influenzae type b infections. Inflammation leads to narrowing the airway and produces the characteristic high-pitched stridor sounds.
It usually affects children between the ages of 2 and 7, but vaccination against H. influenzae in many developed countries has dramatically reduced the incidence of acute epiglottitis.
The disease incidence remains high in countries where the vaccine is not part of the routine vaccination program and older adults who have not been vaccinated.
Other causes include:
- S. Pneumoniae.
- S. Pyogenes.
- P. Aeroginosa o HSV.
Clinical features or symptoms
Patients will initially present with a sore throat, fever, and dyspnea, characteristically in the absence of cough. If left untreated, late signs of the condition include drooling, dysphagia, and stridor.
The patient will look poorly and classically in the late stages of the disease, sitting in the tripod position to allow gravity to help keep the airway open.
All cases of epiglottitis require urgent evaluation by the primary anesthesiologist or ENT surgeon in an HDU or ICU setting (the airway should not be examined without such support due to the high risk of airway narrowing).
When epiglottitis is suspected, do your best not to disturb the child with the tests, further increasing the risk of airway closure.
Nebulized epinephrine and IV dexamethasone should be started in all suspected cases.
Blood and throat cultures should be taken, and broad-spectrum intravenous antibiotics (such as penicillin and ceftriaxone) should be given, along with analgesia and IV fluids.
Most cases are clinical diagnoses, but examination under anesthesia (AUS) and intubation is required once the initial management steps are implemented.
Fiberoptic nasal endoscopy may be attempted to visualize the airway to confirm the diagnosis.
Patients should receive intravenous antibiotics and steroids until the condition begins to improve.
Close contacts of the patient who has not been vaccinated should receive appropriate antibiotic prophylaxis.
Laryngotracheobronchitis
Laryngotracheobronchitis (or croup) is an inflammation of the larynx, trachea, and bronchus, including the vocal cords, most commonly due to a viral infection.
The condition produces a characteristic barking cough, mainly affecting infants and children six months to 2 years.
Croup is more common in the winter. Most patients can be managed in the outpatient setting, with only a few requiring hospitalizations (only 2% of hospitalized patients will eventually require intubation).
The prognosis for croup is excellent as most cases are making a full recovery. Yet, potential complications include a secondary infection (such as bacterial tracheitis) or dehydration (secondary to poor oral intake).
The cause of croup in 95% of cases is a viral infection, common organisms that include:
- Parainfluenza.
- Influenza.
- RSV.
- Rhinovirus.
Clinical features or symptoms
Croup is a self-limited disease that worsens within 48 hours and gradually improves.
An upper respiratory infection usually precedes it before developing into dyspnea and a characteristic cough, with potential fever. Symptoms are generally worse at night.
Most cases do not require any investigation and can be made as a clinical diagnosis.
Any case of higher grade can justify the presence of blood for inflammation manufacturers to confirm the diagnosis and viral swabs to determine the possible viral strain.
Management
According to NICE guidelines, all children with croup should receive a single dose of oral dexamethasone (0.15 mg/kg) to reduce inflammation and symptoms.
Pain and fever can be controlled with acetaminophen and ibuprofen, as needed. In any case of dehydration, intravenous fluids can be considered, along with supplemental oxygen.
Hospital admission
In the presence of any of the following signs, hospital admission should be considered:
- History of severe croup.
- Known structural upper airway obstruction.
- Immunocompromised patient.
- Uncertain diagnosis.
- Sick child, inadequate intake.
- Less than six months old.
Inhaled corticosteroids may be given in the hospital and nebulized epinephrine to decrease airway inflammation. In severe cases, intubation may be justified.
Treatment
The treatment to improve stridor, the doctor will carry out a previous diagnosis of the causes that precede it and, in this way, will apply the appropriate treatment to the patient’s condition.
Some of the treatments are usually:
Racemic epinephrine by nebulization
Epinephrine caused vasoconstriction and decreased blood flow, which reduced edema formation.
There is a lack of randomized controlled trials demonstrating the efficacy of epinephrine in post-extubation laryngeal edema in adults.
There is no consensus on the potentially effective dose of epinephrine nebulization. Rebound edema is known to occur, and the patient should be monitored for this.
At my institution, respiratory therapists like to repeat a dose of nebulized epinephrine, so I make sure I have two vials available of 2.25% and 0.5 ml of racemic epinephrine.
Dexamethasone
Corticosteroids reduce edema by downregulating the inflammatory response and decreasing the dilation and permeability of capillaries.
The most effective dose has not been determined. I use 8 mg dexamethasone according to the prescription patterns at my institution.
Intubation
If the stridor does not resolve, endotracheal intubation will be necessary before the patient experiences respiratory failure.
Intubation in the stridor setting is often difficult due to the airway obstruction that is causing the stridor.
Prevention
Corticosteroid administration before elective extubation has been used to prevent stridor and reintubation after extubation.
Multiple steroid regimens have been studied to prevent stridor and reintubation after extubation. To my knowledge, no regimen has been superior.
Three example regimes are:
- Dexamethasone 5 mg IV q6 hours x 4 doses the day before extubation.
- Methylprednisolone 20 mg IV q4 hours x 4 doses before extubation.
- Methylprednisolone 40 mg IV once 4 hours before extubation.
