Intensive care units (ICU), also called critical care or intensive therapy departments, are sections within a hospital that look after patients whose conditions are life-threatening and need constant, close monitoring and support from equipment and medication to keep normal body functions going. They have higher levels of staffing, specialist monitoring and treatment equipment only available in these areas and the staff are highly trained in caring for the most severely ill patients. Some hospitals have areas called high dependency units (HDU) and some specialist units have high dependency areas within the ICU. Hospitals differ in what they call these areas but their role and expertise is the same.

Some patients are in an ICU for shorter periods of time than others, depending on the extent of their illness or injury. They may be admitted either as a planned admission after major surgery or as an emergency admission following an acute illness. As patients get better and need less intensive care, they are sometimes transferred to a high dependency unit (HDU) and then to a general ward somewhere else in the hospital.

Someone who is seriously ill or who has suffered a serious injury is usually admitted first to the Emergency Department (ED) of a hospital. Here, the emergency team assess and stabilise the patient. If the patient's condition is life-threatening, the patient is transferred to the intensive care unit (ICU) because he or she needs continuous observation, treatment and specialised care.

Once someone  is admitted to critical care it is a time of great stress and worry. It might help to know what to expect. ICUs vary in size from one hospital to the next. Some are small with about six beds. Others may have more than double this number. You should expect a high level of activity round the clock. Noise levels are likely to be higher than on a general hospital ward largely because of the operation of the equipment, often beeping or sounding an alarm. If you do hear an alarm it doesn't necessarily mean something's wrong, just that there's something the staff need to be aware of. Staff will be able to explain the equipment and noises to you should you have concerns about the alarms.
Intensive care units in the United Kingdom are run and staffed by specialists trained in intensive care. Once a patient is admitted to the unit the intensive care team will manage the care of the patient in consultation with the original team that admitted the patient to the hospital and any other specialists that they think can help to aid the patient's recovery. The intensive care doctors and nurses will give the best overview and general update on the patient, but they may refer relatives to the specialist teams for discussion of certain aspects of care.

Once a patient has recovered and is well enough to be transferred to the ward their care will be handed over to the ward team. Intensive care teams often continue to visit patients on the ward and some units offer follow up clinics to look for problems that are specific to patients who have had long stays and been severely unwell.

Visiting in intensive care is often very flexible, being a difficult time for families. However there will be times when you will be asked to wait because of interventions being carried out or because of other patients being very unwell. The number of people around a bed at one time will be limited for the patient's safety.

Infection control is very important in intensive care as patients who are very unwell are very susceptible to infection, and visitors are required to comply with local hygiene policies.

Sometimes patients must be transferred to other hospitals or transferred to the ordinary wards, and this can happen at any time although this should be done during the day whenever possible. The staff have to make tough decisions about where a patient can be best cared for and sometimes which patient can best cope with being transferred. These decisions are always made by the most senior doctors and nurses.

It is now recognised that critical illness places not only physiological stress on  the body but also severe psychological stress on both patients, their families and close friends. Being critically ill is a major life event and is inevitably going to have a big impact on all involved, particularly the patient.

 
 
What are the common conditions requiring critical care?

Patients with critical illness suffer from failure of one or more of their systems such as the heart, lung or kidneys. Heart attack, stroke, poisoning, pneumonia, surgical complications, major trauma as a result of road traffic accidents, a fall, burns, an industrial accident or violence are all examples of critical illnesses. Patients recovering from a major operation are also admitted to intensive care units (ICUs).

There are many reasons a person may need care in an ICU and there are some common conditions that either bring a patient to the ICU or develop while the patient is in the unit.

Shock can occur when the organs of the body do not get enough oxygen and blood flow for them to function normally.

Respiratory failure occurs when the lungs do not work effectively. Respiratory failure can be caused by a variety of conditions such as heart failure, pneumonia and COPD (chronic obstructive pulmonary disease). When it is severe it can be called "acute lung injury" or most severe of all ARDS (Acute Respiratory Distress Syndrome).

Infections are a common cause of ICU admission and can develop for many reasons while a patient is in the ICU. Usually the illness that has brought the patient to the ICU has weakened them and lessened their ability to fight off infections.

An infection, as well as age and pre-existing medical conditions affecting the patient, may put them at risk of uncontrolled inflammation, which is called sepsis.

Overwhelming infection that causes at least one acute organ dysfunction is called severe sepsis. This occurs when the inflammatory response begins to affect the basic functions of the body (renal kidney failure and acute respiratory failure, to name two), and the patient becomes very sick.

 
 
Levels of Care

A Department of Health report in 2000 entitled "Comprehensive Critical Care" defined four different levels of care encompassing patients in hospital.

The definitions of these levels of care are:

Level 0
Patients whose needs can be met through normal ward

Level 1
Patients at risk of their condition deteriorating, or higher levels of care whose needs can be met on advice and support from the critical care team.

Level 2
Patients requiring more detailed observation or intervention, single failing organ system or postoperative care, and higher levels of care.

Level 3
Patients requiring advanced respiratory support alone or basic respiratory support together with support of at least two organ systems. This level includes all complex patients requiring support for multi-organ failure.

High dependency can refer to level 1 or 2 whereas intensive care usually means level 2 or 3.