What is Neurogenic Pulmonary Edema?
Neurogenic pulmonary edema (NPE) is a health issue that happens due to severe brain or nerve damage, causing acute, or sudden, trouble with breathing. Essentially, this issue results from a fast buildup of fluid outside the blood vessels in the lungs, following severe injuries to the central nervous system (CNS), which includes the brain and spinal cord. This condition, mostly related to the lower part of the brain, was first identified by Shanahan in 1908.
To diagnose NPE, it’s important to rule out other potential causes for lung damage or heart problems that may occur alongside the nerve-related distress. These might include lung-related issues like inhaling food or liquid into the lungs, or issues related to the heart and lungs due to insufficient blood supply, exposure to harmful substances, or injuries.
If the signs and symptoms are clear-cut, we can generally assume that NPE is the cause when sudden fluid buildup in the lungs happens alongside a CNS injury, and when there are no direct injuries to the heart or lungs. However, there’s still some uncertainty, especially because current medical studies don’t fully explain how exactly this condition develops.
What Causes Neurogenic Pulmonary Edema?
Neurogenic pulmonary edema, a form of fluid buildup in the lungs, can be caused by any kind of injury to the brain. The three most common causes of this condition are head injuries (either from a wound or a blow), bleeding around the brain (most often from a burst blood vessel, which happens in over half of such cases), and epilepsy (a disorder that causes frequent seizures).
There are also other situations that can cause this condition, such as spinal cord injury, recovering from brain surgery, and meningitis (an infection that causes brain swelling).
If a person with a brain injury also develops neurogenic pulmonary edema, their chances of survival reduce drastically, with death rates between 60% and 100%. These high death rates are not just due to the lung condition, but also because of the initial brain injury.
Risk Factors and Frequency for Neurogenic Pulmonary Edema
Neurogenic pulmonary edema is a condition that isn’t common. In fact, it usually only shows up in autopsy results of patients who have died right after having a seizure or individuals who have suffered major head injuries. It’s a rare condition, and out of the people who have severe head injuries, only about 20% end up with neurogenic pulmonary edema.
Signs and Symptoms of Neurogenic Pulmonary Edema
Neurogenic pulmonary edema is a condition that generally develops quickly following an injury to the brain. This condition is most common in children and young adults who have recently had some type of brain trauma. In the instance of an injury without penetration to the head, this type of pulmonary edema can start within minutes. Its symptoms aren’t unique to the condition, but typically align with other causes of fluid buildup in the lungs. However, unlike pulmonary edema caused by left ventricle heart failure, neurogenic pulmonary edema’s onset is immediate and can be diagnosed 2 to 12 hours after the initial injury.
Early symptoms usually include issues with ventilation, which are often paired with high systolic blood pressure. In patients who can breathe independently, symptoms like shortness of breath, rapid breathing, coughing, racing heart rate, rattling sounds heard during lung examination, pink, foamy sputum, or coughing up blood may present early. Other, less evident symptoms include insomnia, excessive sweating, paralysis of the intestines, and temporary hypertension. A short while later, issues with ventilation/perfusion, low oxygen levels in the blood, and excessive carbon dioxide can occur.
- Issues with ventilation
- High systolic blood pressure
- Shortness of breath
- Rapid breathing
- Coughing
- Racing heart rate
- Rattling sounds heard during lung examination
- Pink, foamy sputum or coughing up blood
- Insomnia
- Excessive sweating
- Paralysis of the intestines
- Temporary high blood pressure
This condition will generally progress to respiratory failure and then cardiovascular collapse if not treated, which has an over 60% mortality rate. It’s difficult to determine if the cause of death is neurological, cardiovascular or directly related to lung failure. Some recent studies suggest that the brain injury causing the edema is the more likely cause of death, but in the case of pediatric encephalomyelitis, the cause of death would more often be lung and heart failure.
Testing for Neurogenic Pulmonary Edema
Neurogenic pulmonary edema, a type of lung flooding caused by nerve damage, is usually diagnosed based on symptoms in the patient, along with acknowledging a history of nerve injury. The goal of the diagnosis process is to rule out other potential causes.
An important test in this process is a chest X-ray. This helps the doctor distinguish between neurogenic pulmonary edema and a condition called aspiration pneumonitis, which involves inhaling foreign material into your lungs. With aspiration pneumonitis, it can take a few hours before changes are visible on an X-ray and can take up to three weeks to disappear. However, with neurogenic pulmonary edema, lung changes are seen immediately following the injury. The X-ray can also help to rule out other lung issues such as a bruised lung, a condition known as a hemothorax where blood collects in the chest, or a pneumothorax which is more commonly known as a collapsed lung.
Electrocardiography and echocardiography are two additional tests that can be helpful. The first, electrocardiography (also known as an EKG or ECG), is a test that measures the activity of your heart to identify any functional issues. Echocardiography, on the other hand, uses sound waves to create pictures of your heart, allowing doctors to see if there are any structural problems.
There’s no specific biological marker, or biomarker, a type of substance that can be measured to indicate the presence of neurogenic pulmonary edema. However, it’s still important for the doctor to take into account measurements of certain substances, like cardiac enzymes, which can provide valuable information about the health of your heart.
Treatment Options for Neurogenic Pulmonary Edema
This condition typically improves after 2-3 days of treatment, and then the prognosis or likely outcome depends more on the underlying neurological problem. Cases of this condition that have severe prognoses require consistent monitoring to ensure early detection and suitable treatment.
These are very serious situations with a high risk of death and require intensive care. If neurogenic pulmonary edema, a condition characterized by the rapid onset of fluid accumulation in the lungs, is suspected, the immediate treatment often includes artificial ventilation and monitoring in an intensive care unit. It may be beneficial to continuously measure intracranial pressure (ICP) and possibly capillary lung pressure.
Treatment should focus on addressing the core cause, which is often challenging with severe head injuries. The main effort in cases of widespread injury to the central nervous system (CNS), which includes the brain and spinal cord, will be on lowering the ICP. The therapy will focus primarily on boosting the cardiovascular system, especially by increasing the heart’s contractile force, often through the stimulation of beta-adrenergic receptors (found in the heart). Reducing resistance in the lungs’ blood vessels is also crucial. An experimental treatment for this is Nitric Oxide (NO), which may be helpful.
In the advanced stages of neurogenic pulmonary edema, treatments used for acute respiratory distress syndrome (ARDS), a severe lung condition that causes low oxygen levels in the blood, may be necessary. This includes strategies to support the cardiovascular system and ventilation. However, there is still debate about whether steroids should be administered as part of the treatment.
What else can Neurogenic Pulmonary Edema be?
These are some conditions that might cause confusion when diagnosing a respiratory disorder because they present with similar symptoms:
- Adult respiratory distress syndrome
- Aspiration pneumonitis and pneumonia
- Bacterial pneumonia
- Cardiogenic pulmonary edema
- Subarachnoid haemorrhage
