Overview of Electrodiagnostic Evaluation of Critical Illness Neuropathy
As medical technology continues to improve, more very sick patients are surviving and staying longer in intensive care units (ICUs). However, even with the best medical care, patients who have serious conditions such as blood poisoning (sepsis), failure of multiple organs, severe burns, need for long-term breathing support through a tube (prolonged mechanical ventilation), and use of many different medications often develop severe weakness in their muscles during their stay in the hospital. This muscle weakness, often called “ICU-acquired weakness” (ICUAW), can be caused by diseases that affect the nerves (neuropathy) or the muscles (myopathy) or a combination of both.
Studies show that up to 83% of patients who need breathing support for more than 7 days can develop this condition. Patients with this weakness may have difficulty waking up from sedation, or they may continue to need help breathing even after they’re alert. They may have profound weakness or numbness in their arms and legs. After they leave the ICU, their physical examination may reveal poor deep tendon reflexes, muscle wasting, or difficulty with balance. However, they usually have no problems with swallowing or eye movements. A test called creatine phosphokinase is often normal, which can help doctors confirm that the problem is neuropathy (damage to nerves), not myopathy (damage to muscles). Sepsis is the most common cause of this nerve damage, while the use of certain medications that affect the muscles and steroids are more often associated with muscle damage.
Despite these challenges, patients who have these problems can often be helped with a treatment plan that’s geared to their specific needs. The key step in creating this treatment plan is getting an accurate diagnosis. The most accurate way to diagnose these conditions is electrodiagnostic testing, which includes nerve conduction studies and needle electromyography. However, this testing may be difficult to perform in the ICU. Despite these challenges, it can help the medical team decide on the best treatment for each patient.
Doctors aren’t entirely sure what causes these conditions, but they think the causes probably include changes in the blood vessels, changes in how cells use energy, and disruptions in the electrical signals that nerves use to communicate with each other. Treating these underlying problems and getting patients moving again may help improve their condition.
The exact way that these conditions show themselves can vary somewhat, depending on whether the problem is mainly with the nerves or the muscles. Patients with nerve problems often have weakness that’s worse in their legs than in their arms, lose their deep tendon reflexes early, and have difficulty being weaned from a ventilator. Patients with muscle problems often have weakness that’s worse in their arms than in their legs, lose their deep tendon reflexes later, and also have difficulty being weaned from a ventilator. A test for nerve and muscle problems using a needle (a biopsy) may be done to help doctors make the diagnosis.
Why do People Need Electrodiagnostic Evaluation of Critical Illness Neuropathy
If a person is severely ill, they can develop problems with their nerves and muscles, known as critical illness neuropathy and myopathy. These conditions make it challenging for patients to stop relying on a ventilator, also referred to as ‘weaning off.’ If the patient is no longer using a ventilator, they may experience intense weakness and limp limbs. In addition, those with nerve issues (critical illness neuropathy) can experience feelings of numbness or strange sensations, especially in their hands and feet.
The difficulty in ending the use of a ventilator arises due to the diaphragm’s impact, a critical muscle for breathing. The nerve (the phrenic nerve) that controls the diaphragm is damaged. Other respiratory muscles, which help with breathing, may also be affected.
It’s crucial for healthcare providers to remember that nerve damage may not be noticeable on tests for about 10 to 14 days after the injury. This delay is due to a process called Wallerian degeneration, where nerves deteriorate after an injury. Thus, special tests to diagnose these nerve problems should be reserved for the right patients and typically ordered around two weeks after symptoms appear.
When a Person Should Avoid Electrodiagnostic Evaluation of Critical Illness Neuropathy
There are a few reasons why certain critically ill patients can’t undergo electrodiagnostic studies. If you’re not familiar with the term, electrodiagnostic studies are tests doctors use to check the health of your muscles and nerves. Here are some reasons why these tests may not be suitable:
– For those with severe blood clotting disorders, a procedure called needle electromyography (EMG, for short), is not suitable. In this procedure, small, thin needles are inserted into the muscle to record electrical activity.
– The needles for EMG should also not be used if the patient has an active infection in the soft tissues, which includes muscles, fats, and other similar tissues.
– If a patient has a device implanted in their heart called a cardiac defibrillator, or if they’re connected to an external defibrillator (devices that can give the heart a controlled electric shock), they can’t undergo nerve conduction studies. These are tests that check how well the nerves can send electrical signals.
– Doctors need to check if a patient has a pacemaker before performing an electrodiagnostic study. The electrical stimulation during the test should not be done directly on or near the pacemaker.
How is Electrodiagnostic Evaluation of Critical Illness Neuropathy performed
Before carrying out any tests, doctors conduct a comprehensive review of the patient’s medical history and their present condition. They then perform a full physical assessment. A good doctor would take the time to explain to the patient and their family the reasons behind the tests and give an overview of what each test entails. To diagnose CIN, which stands for Critical Illness Neuropathy, accurately using electrical tests, ideally three limbs should be examined. These tests include assessing sensory and motor nerve functions and muscle testing, comparing both upper and lower muscles.
Just like all nerve function studies, it’s important to keep the patient’s limbs warm. Cold temperatures could potentially increase the signals, prolong the time it takes for signals to travel, and slow down their speed. To minimize any electrical disturbances in the Intensive Care Unit (ICU), a specific device called a notch filter should be used. If possible, all unnecessary machines should be turned off to avoid interference, which also includes unplugging the hospital bed.
Possible Complications of Electrodiagnostic Evaluation of Critical Illness Neuropathy
Like all electrical tests used to diagnose health conditions, the risk of any severe side effects is quite low. However, when needles are involved in such tests, there’s a tiny chance that you could experience some bleeding or develop an infection. Despite these risks, they’re quite rare and these tests are generally safe.
What Else Should I Know About Electrodiagnostic Evaluation of Critical Illness Neuropathy?
Critical illness neuropathy is a condition that affects your nerve fibers, particularly those that convey feelings (sensory) and those that control movements (motor). These nerves can be tested using various studies and procedures like the use of an EMG test which records the electrical activity of your muscles, or through muscle biopsies, which involve removing a small piece of muscle tissue for laboratory analysis. These procedures help in differentiating between two types of conditions that appear similar, Critical illness polyneuropathy (CIP) and Critical illness myopathy (CIM).
Nerve conduction studies (NCS) are tests that measure how your nerves are working. There are sensory and motor type NCS. In both types, the disease mainly affects the parts of the nerves that are furthest from where the nerve originates and less of the parts that are near.
The sensory type mainly assesses how your nerves transmit signals related to senses like touch or temperature. In this type of test, an affected individual will show a decrease in the level and absence of signals related to these kind of senses.
Motor NCS tests how well your nerves transmit signals that control muscle movements. Similar to the sensory NCS, in this test there is a signal reduction and absence of signals responsible for muscle action.
Additionally, needle electomyography records the electrical activity of your muscles, and can reveal abnormalities in muscular electrical activity, specifically in the muscles which are further from your body’s center.
Different sets of diagnostic features help distinguish between CIP and CIM. For instance, CIP tends to have a reduction in these electrical wave amplitudes, normal latency (time it takes for the muscle to respond to a stimulus), and the presence of abnormal spontaneous potentials. In contrast, CIM preserves the sensory response with reduced motor responses and specific types of abnormal wave detection.