Terminology
ICU Equipment
ICUs are equipped with complex machines and monitoring devices designed for the unique needs of critically ill and postoperative patients. Equipment may include the following:
Cardiorespiratory or heart monitor. This monitor continuously displays the heart and respiratory rate. Wires from the monitor are attached to adhesive patches on the skin of the chest and abdomen.
Blood pressure monitor. Blood pressure is measured using a cuff placed on the arm or leg. Periodically, a blood pressure monitor pumps up the cuff and measures the blood pressure. Some people need continuous blood pressure monitoring. This can be done using a small catheter (small tube) in one of the arteries.
Pulse oximeter. This machine measures the amount of oxygen in the blood through the skin. A tiny light is taped to the finger, ear, or toe. A wire connects the light to the monitor where it displays the percent of oxygen in the red blood cells.
Transcutaneous oxygen/carbon dioxide monitor. This machine measures the amount of oxygen and carbon dioxide in the skin. A small, circular pad is attached to the patient's skin, most often on the chest or abdomen. The pad warms a small area of skin underneath and measures oxygen, carbon dioxide, or both. A wire connects the pad to the monitor and displays the levels. Because the transcutaneous monitor heats the skin, it must be moved to different places on the skin every few hours. The heating may leave a temporary reddened spot on the skin.
X-ray. Portable x-ray machines are brought to the bedside in the ICU. X-rays are taken for many reasons including checking placement of catheters and tubes, looking for signs of lung problems, and checking for signs of bowel abnormalities.
Endotracheal tube (ET tube). This tube is placed through the mouth or nose and into the trachea (windpipe). The ET tube is held in place with tape and is connected with flexible tubing to a mechanical ventilator (breathing machine). The patient will not be able to speak or cry while he/she has an ET tube, because the vocal cords are unable to vibrate and make sounds with the tube in place. This is temporary and the patient will regain his/her voice after the ET tube is removed, although he/she may be hoarse.
Respirator or mechanical ventilator. This machine helps patients who are unable to breathe on their own due to anesthesia, or who need help taking bigger or more effective breaths due to illness. Ventilators can also deliver extra oxygen, if needed.
Intravenous (IV) pumps. Intravenous (IV) pumps deliver fluids and medications in very accurate amounts, through catheters into the veins.
Assessment Tools
Many kinds of assessments and tests can be done to distinguish between coma and other states of unconsciousness. Imaging tests help doctors pinpoint areas of brain injury. These locations also help determine the particular state of unconsciousness. Some of the tests and assessments that doctors may use include but are not limited to:
Computerized tomography (CT). A CT scan uses a sophisticated X-ray machine linked to a computer to produce detailed, two-dimensional images of the brain. This is the best imaging test for assessing brain injuries because it can show bone fractures, hemorrhages or other bleeding and bruising, and brain tissue swelling. The patient lies still on a movable table that's guided into what looks like an enormous doughnut where the images are taken. A special dye may be injected into the bloodstream after a few CT scans are taken. CT scans are good for detecting blood clots, swelling, or compression in the brain. Not all types of brain injuries show up on CT scans. A CT scan generally takes less than 10 minutes.
Electroencephalography (EEG). An EEG measures the waves of electrical activity your brain produces. Small electrodes are attached to your scalp with paste or an elastic cap as you lie still. At times, a light may be flashed in your eyes. These actions are meant to stimulate your brain. The electrodes pick up the electrical impulses from your brain and send them to the EEG machine, which records your brain waves.
Magnetic resonance imaging (MRI) scan. This scan uses magnetic fields and radio waves to generate images of the brain. You lie inside a cylindrical machine for 15 minutes to an hour. MRI scans are particularly useful for examining the brain stem and deep brain structures. Sometimes a special dye is injected into your bloodstream during the procedure. The dye can help distinguish damaged brain tissue from healthy tissue.
Cerebral angiogram. A cerebral angiogram is a type of X-ray. During this procedure, a flexible tube (catheter) is inserted into a large artery — usually in your groin — and threaded past your heart into the cerebral arteries in your brain. A special dye (contrast medium) is then injected into the catheter, and X-rays are taken as the dye fills these arteries. A cerebral angiogram provides a clear picture of the arterial blood flow, but the procedure isn't without risks, including bleeding at the catheter insertion site, infection and stroke.
Other brain scans. Other tests, such as magnetic resonance spectroscopy (MRS), single-photon emission computerized tomography (SPECT) and positron emission tomography (PET) scanning, help doctors gauge brain activity by studying brain metabolism and chemistry and blood flow within the brain. These scans can be combined with an MRI to help doctors understand the effects of a brain injury on brain activity and function.
Glasgow Coma Scale
A doctor or other medical professional usually determines the severity of a coma by assessing the level of consciousness and neurological functioning by using the Glasgow Coma Scale. This test is often done at the scene of an accident or in the emergency room. This 15-point test measures eye opening, verbal response and motor response to document the level of neurological function. Click here for a list of the Glasgow Coma Scale scoring system. (It is sometimes mistakenly called the Glascow Scale.)
Rancho Los Amigos Scale
The Rancho Los Amigos Scale, also called the Ranchos Los Amigos Scale, is another assessment test sometimes used in conjunction with the Glasgow Coma Scale to determine the level of consciousness. This test is helpful to understand the expectations of coma recovery levels. Click here for a list of the Rancho Los Amigos Scale.
Diagnosis
The diagnosis of impaired consciousness is usually made following extensive testing by at least two independent doctors supported by the observations of other health care professionals. Depending upon the level of impairment your relative displays, the doctors will use one of four classifications:
Coma The term comatose is used to describe a person who shows no signs of wakefulness or awareness of themselves or the environment. Comatose patients lie with their eyes closed and they do not respond to command. Coma persists for at least one hour and may last between two and four weeks during which time the person may awaken or subsequently progress to the vegetative or minimally conscious state.
Vegetative state The term vegetative state is used to describe someone who is awake but unaware of themselves or their environment. A person in a vegetative state will open their eyes, demonstrate sleep-wake cycles and basic reflexes, such as blinking when they are startled by a loud noise or
withdrawing a hand when a painful stimulus is applied. However, they do not demonstrate any purposeful response to sensory or cognitive stimuli, such as following an object with their eyes or responding to command.
Minimally conscious state The term minimally conscious state describes a person who shows intermittent but clear evidence of awareness of themselves or their environment. This classification is given if they can respond to command; for example, moving a finger reliably when asked to do so.
Locked-in syndrome This term is used when someone has had a specific type of injury resulting in damage to the brainstem. Someone who is locked-in is both awake and aware, but they are unable to respond because they are paralysed and unable to speak. Typically, persons in this condition are able to communicate only by up and down eye movement. See Locked-In Syndrome.
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