What is an intensive care unit (ICU)?

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A clinical area staffed by a team of highly skilled health care professionals trained to provide total care to patients with severe, life-threatening illnesses or injuries through continuous monitoring of vital signs, supportive care, and intensive medical treatments and therapies.
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Organization and Types of Units

Critical care is a field of medicine that supports patients with complex and critical medical conditions. This essay provides a description of the structure and staffing of intensive care units (ICUs) and some of the important devices and methods they use to support patients. It is not a comprehensive description of every treatment and therapy used in the ICU.

ICUs are organized in various ways depending on the size, resources, and community needs for a given hospital. Large academic medical centers or teaching hospitals most often have multiple units, and they then cluster specific patient populations on a unit. For example, adult patients undergoing a surgical procedure are admitted to the same unit, while adult patients suffering severe trauma are admitted to a different unit. Large hospitals with multiple ICUs are usually located in densely populated areas, such as an urban or metropolitan area. The other extreme is the small community hospital in a rural area that has multiple beds on a clinical unit that are dedicated for intensive care use.

Intensive care units are organized by clinical specialty and the type of services and treatments needed for that population of patients. The most common type is a combined medical, surgical, and respiratory ICU. Surgical ICUs (SICU) care for postoperative patients, medical ICUs manage patients requiring medical care for one or multiple critical illnesses (for example, pneumonia or a poisoning), and respiratory ICUs manage patients with severe breathing problems. Cardiac ICUs, sometimes called coronary care units (CCUs), provide intensive heart monitoring and treatments for patients with heart problems. Some hospitals will have a cardiac-surgical ICU that is separate from the CCU and SICU, where patients are admitted following a cardiac operation, such as coronary artery bypass graft surgery. Trauma ICUs manage patients who were severely injured from a gunshot or stabbing wound, a car accident, a fall, or burns. Neurologic ICUs help patients recover from a stroke or spinal cord or brain injury. Most of these ICUs treat adult patients. Children who require critical care are usually admitted to a pediatric ICU or a neonatal ICU (NICU). The pediatric ICU cares for patients from birth until eighteen or nineteen years of age, and neonatal units care for newborns in their first twenty-eight days of life.

Most ICUs have a nurse manager to oversee the nursing staff and a physician director who sets policies, develops protocols, and communicates with patients, their primary care physicians and family members, and other specialists. An ICU either has full-time intensivist physicians who act as the primary care physicians and fully manage each patient (sometimes called a closed ICU) or brings in intensivists to consult on a patient’s care (sometimes called an open ICU). The physician in charge (often called the attending) manages the patients and coordinates their medical care with other health care professionals on and off the unit and outside the hospital. Patients are admitted from the emergency room or other inpatient unit in the hospital or from another facility such as a nursing home.

One activity performed to deliver the best care possible is daily patient rounds, in which a critical care team visits each patient. Rounds are usually done early in the morning, and in some units teams may revisit patients in the evening. During rounds, the team discusses each patient’s current medical condition and decides what treatments or therapies are needed for the day. The health care professionals performing rounds will vary but always include the attending physician. In teaching hospitals, fellows training to be critical care physicians, residents assigned for a one- or several-month ICU rotation, and medical students from the affiliated medical school will perform rounds with the attending. In some cases, the team is interdisciplinary (multiple clinical disciplines working together), and nurses, pharmacists, respiratory therapists, and others providing medical care to the patients will join rounds.


Intensive care units are staffed by professionals who are highly trained in a certain clinical discipline (type of job). These individuals work together on the unit as a critical care team to provide total and continuous care to patients. The critical care team on a unit includes intensivists, critical care nurses, a pharmacist, a registered dietitian, a social worker, a respiratory therapist, a physical or occupational therapist, physician assistants, nurse practitioners, a hospital chaplain, and child-life specialists.

Intensivists are board-certified or board-eligible in a medical specialty (for example, surgery or pediatrics). They have additional training, education, and certification to know every organ system in the body and how treatments, procedures, and medications may affect critically ill patients.

Critical care nurses are trained to monitor and manage the needs of acutely and critically ill patients. For example, they clean and monitor open wounds and ventilators to prevent patients from developing infections. Moreover, a nurse can receive additional education and training to become certified as a critical care registered nurse (CCRN).

Pharmacists are trained and board-certified or board-eligible in the appropriate and safe use of medications. They also can choose to undertake additional training to understand the specific problems and needs of critical care patients.

Respiratory therapists monitor and manage a patient’s breathing using a variety of methods and devices, such as oxygen therapy or mechanical ventilation. Physical therapists work with patients to restore or improve mobility, relieve pain, and limit or prevent physical disability. Occupational therapists assess the impact of the disease or injury on the patients’ ability to function at home, at work, and during physical activity after hospital discharge.

Physician assistants and nurse practitioners are licensed with advanced critical care training and work directly under the intensivist. They assist the intensivist, for example, by performing physical exams and procedures, diagnosing and treating illnesses, writing orders, and talking with patients and families. Child-life specialists are licensed professionals who provide play therapy to help children recover from an illness and therapies to distract them during painful procedures. The hospital chaplain offers pastoral support to patients, family members, and staff.

Supportive Care

A wide array of devices, equipment, and medications are used in the ICU to provide supportive care to patients recovering from life-threatening illnesses or injuries. Thus, it is one of the most complex clinical areas in the hospital. In an ICU, lines, tubes, drains, and other devices are attached to or inserted into patients. Any one patient may have as many as fourteen of these different-sized tubes attached in some way to the body. All patients will have heart monitor leads attached to the chest area to monitor the electrical activity of the heart and a pulse oximeter that typically clasps onto a finger to monitor oxygen levels in the blood and pulse rate. Patients may also have a cuff on the arm for periodic blood pressure monitoring and a peripheral IV inserted in a vein on the top of the hand to give fluids or medications. A patient may need a Foley catheter inserted up to the bladder to collect urine or a dialysis catheter inserted in the groin area and attached to a machine to assist the kidneys in cleaning the blood. Other small, tube-like catheters include central line/pulmonary artery (PA) catheters inserted in the neck to monitor blood flow or give medications or life-sustaining nutrition, an arterial line inserted in an artery at the wrist to monitor blood pressure, or an intracranial pressure catheter inserted in the brain to monitor its swelling.

A patient may need assistance breathing. In this case, either an endotracheal tube is inserted in the mouth or a tracheostomy tube is inserted in the neck and attached to a machine (a process called mechanical ventilation) to regulate the patient’s breathing and provide the appropriate mix of oxygen and gas. A tracheostomy tube is used only if the patient will need mechanical ventilation for a prolonged period. Chest tubes are inserted under the skin around the rib cage area to remove escaped air or drain blood from the space around the lungs. This type of drainage tube is also used in other areas of the body to remove fluids or blood from a wound. A nasogastric tube inserted through the nose and down into the stomach can remove acid or other unwanted fluids or can supply nutrition. An intra-aortic balloon pump inserted into the groin helps the heart pump blood through the body.

Several emergency procedures can be performed in the ICU to revive a patient who has stopped breathing or is experiencing cardiac arrest. Cardiopulmonary resuscitation (CPR) is a series of things done to open the patient’s airway (tilting the chin up, opening the mouth, holding down the tongue), help with breathing (blowing air into the mouth), and help pump blood from the heart into the body (chest compressions). Sometimes manual resuscitation will be done. In this case, a face mask is placed over the patient’s mouth or a breathing tube inserted down the throat, and a plastic bag is attached and manually squeezed by the doctor, nurse, or respiratory therapist to fill the lungs with oxygen. Manual resuscitation is a short-term solution for a breathing problem. A patient who continues to require breathing support will be placed on a mechanical ventilator. A patient experiencing cardiac arrest will be defibrillated by placing two paddles attached to a defibrillator on the chest to send an electrical shock through the heart in an attempt to restart the heart’s natural rhythm. This procedure may have to be done more than once to convert the heart back to its natural rhythm.

Perspective and Prospects

Intensive care units are relatively new considering the practice of medicine dates to about 4000 BCE, during ancient Egyptian times. The history of intensive care began in the late 1920s when W. E. Dandy opened a three-bed unit for patients following neurosurgery at Johns Hopkins Hospital in Baltimore. About the same time, in 1927, Sarah Morris Hospital in Chicago opened the first center to care for infants born prematurely. The devastation of World War II prompted the creation of wards to resuscitate and care for severely injured soldiers, and afterward, recovery rooms were opened to group postoperative patients together to compensate for a nursing shortage. By 1960, postoperative recovery rooms were in every hospital. Another catastrophic event that contributed to intensive care was the polio epidemic in 1947–48. To compensate for the development of respiratory paralysis and death from polio, doctors in Denmark developed mechanical ventilation therapy to keep patients breathing during this illness. The benefits of this therapy prompted the opening of respiratory ICUs in the 1950s. Then, in 1958, Baltimore City Hospital (now Johns Hopkins Bayview Medical Center) opened the first multidisciplinary ICU in the United States. By the late 1960s, most US hospitals had at least one ICU, and in the late 1990s there were about six thousand ICUs.


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