Updated May 16, 2014.

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Patients with neurological illnesses are distinct from other kinds of patients. Because their problem involves their nervous system, they are more prone to develop certain kinds of problems. The advantage of a neurological ICU is that physicians and nurses have specialized training that allows them to better recognize and manage such problems when they arise.

Hyponatremia

Neurological illnesses can cause the release of hormones that alter the concentration of sodium in the blood, which is known as hyponatremia.

This is problematic, since low blood sodium concentrations can cause fluid to leak into brain tissue and worsen edema and swelling. There are two main ways that brain injury leads to hyponatremia: the syndrome of inappropriate diuretic hormone hypersecretion (SIADH) and cerebral salt wasting syndrome (CSWS). SIADH is actually related to abnormally high levels of water in the body, and CSWS actually causes abnormally low levels of body sodium. In other words, while the two problems may cause a similar lab value, they are actually quite different and require different treatment. To learn more about these problems, read: Hyponatremia in Neurology

Deep Vein Thrombosis

There are three main risk factors for developing blood clots: stasis, vascular damage, and hypercoagulability. Stasis simply means that you aren’t moving much. That’s why airplanes encourage passengers to get up now and then during long flights and walk around the cabin. Staying still too long could cause blood clots to form in the veins of your legs.

If these clots break off from the legs, they could float up into the lungs and cause a life-threatening pulmonary embolus. Damage to the wall of a blood vessel can also cause clots to form, as is the case with arterial dissection. Finally, some people have blood that is especially prone to forming clots, and are therefore at an increased risk for deep vein thrombosis and pulmonary embolism.

Patients in neurological ICUs are especially prone to developing blood clots. Due to the nature of their illness, people who are paralyzed or in a coma do not move. Furthermore, some stroke victims had their ischemic stroke because they have blood that is prone to forming clots. Victims of head trauma may have suffered additional damage to blood vessel walls.

Further complicating this issue is the question of what to do if someone develops a blood clot while they are in the ICU for a bleed in their brain. For example, subarachnoid hemorrhage has been associated with a very high risk of deep vein thrombosis. Blood clots are usually prevented by giving blood thinners like heparin, but these drugs can worsen bleeding. How to manage these competing risks can be a tough decision. Learn more about deep vein thrombosis here: What is Deep Vein Thrombosis?

Aspiration

When faced with an emergency situation, doctors are taught to focus on the ABCs, which stand for airway, breathing, and circulation. The most important of these things is airway. Unless the passages that allow us to breathe are open, nothing else matters. Even a heartbeat is often of less immediate importance. Inhaling something into the lungs that isn't meant to be there is known as aspiration, and it can set someone up for serious infections.

Most of us do little things every hour to ensure our airways remain open. The simple unconscious action of swallowing saliva, for example, ensures that bacteria from our mouth doesn’t trickle into our lungs and blossom into a pneumonia. We sigh on occasion to keep small regions of our lungs from collapsing. If we feel a tickle at the back of our throat, we cough.

People who have damaged the nerves that control their chest wall, diaphragm, tongue or throat may have trouble doing these simple, unconscious actions. Someone in a coma may not do any of these things either. In an intensive care unit, these things are done for them by technicians and nurses with techniques like suctioning, respiratory therapy, and artificial cough induction. To learn more, read here: Aspiration Pneumonia

Infection

Intensive care units are where the sickest of sick people are cared for. That also means that ICUs are frequently where the toughest and most dangerous bacteria can be found. Because of the frequent use of strong antibiotics in ICUs, some of these bacteria have evolved to resist antibiotics, making infections especially difficult to treat.

Medical staff are trained to use every precaution to avoid spreading infection, including hand washing and sometimes gowns and masks as well. However, no precaution works one hundred percent of the time, and sometimes infections spread despite these precautions. For this reason, medical staff watch patients closely for signs of infection. Moreover, attempts are made to move the patient to a less virulent location, such as a normal hospital floor, as soon as reasonably possible.

To learn more, read here: Superbugs on the Rise

Acute Confusional State

Acute confusional state, also known as delirium or encephalopathy, is one of the most disconcerting things that patients or their loved ones experience in the hospital. Unfortunately, it is also one of the most common. As many as 80% of intubated patients in ICUs experience this condition. The person becomes confused about where they are, what time it is, and what is going on. They may not recognize friends or family. They may hallucinate, or become paranoid. Sometimes this leads to attempts to escape the hospital or pull out tubes and IVs required to keep the patient alive. The treatment of acute confusional state can be almost as distressing as the problem, since it can involve giving sedating medications or even physically restraining the patient. However, there are many less severe steps that can be taken to manage confusion before it gets out of hand. Learn more here: Introduction to Delirium

Subclinical Status Epilepticus

When most people think of a seizure, they picture someone violently shaking. There are more insidious types of seizure, though, in which someone doesn’t appear to be doing much of anything, or may just appear confused. Nevertheless, these people could benefit from proper medication. Some studies have suggested that as many as 10% of people in ICUs may have seizures that often go undetected, and this rate is likely higher in patients with neurological problems. Learn more here: What is Status Epilepticus?

Dysautonomia

The autonomic nervous system is unconscious and often underappreciated. This is the part of the nervous system that controls heart rate, breathing, blood pressure and more. Just as neurological diseases can alter the functions we normally think about, like movement and speech, some disorders can affect the autonomic nervous system as well. Read here: Dysautonomia

The problems listed above are often found in many types of different diseases that bring someone to a neurological ICU. While they may be found in other intensive care units as well, other specialists may not be as familiar with identifying and managing these kinds of problems. For this reason, neuro-ICUs have proven to be valuable in treating people with serious neurological illnesses.

<sub>Sources:

Allan H. Ropper, Daryl R. Gress, Michael .N Diringer, Deborah M. Green, Stephan A. Mayer, Thomas P. Bleck, Neurological and Neurosurgical Intensive Care, Fourth Edition, Lippincott Williams & Wilkins, 2004

Braunwald E, Fauci ES, et al. Harrison's Principles of Internal Medicine. 16th ed. 2005.</sub>