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Imaging:

Medium of Contrast

Visibilidad de estructuras o fluidos del cuerpo, mejorando el diagnóstico

Also known as a contrast material or agent, the substance is administered internally in the body to improve pictures obtained by X-rays, computed tomography, magnetic resonance imaging (MRI) and ultrasound.

The role of contrast materials is to help doctors diagnose accurately, abnormalities or diseases that may present in the patient.

The three main ways in which a contrast material can enter the body, are divided into:

  • Swallowed (taken by mouth or orally)
  • Administered by enema (rectally)
  • Injected into blood vessel (vein or artery)

After the exam, the material is absorbed by the body or eliminated through urine or bowel movements.

Types

  • Iodinated compounds and barium sulfate: used in X-ray examinations and computed tomography (CT), these contrast materials can be injected into veins or arteries, between discs or fluid spaces in the spine, and within other body cavities. For its part, the barium sulfate contrast material is more common. Is taken by mouth or orally, rectally and is available in powder, liquid, paste and tablet form.
  • It is noteworthy that when such materials are present in a specific area of the body, they block the ability of X-rays to pass through that area. As a result, blood vessels, organs and other body tissues, change their appearance in X-ray images or CT.
  • Gadolinium: is the most used in MRI exams. When this substance is present in the body, it alters the magnetic properties of nearby water molecules, increasing the quality of the images.
  • Saline solution and air: microscopic bubbles are administered for imaging ultrasound, especially in heart tests.

Exams

1.   Oral contrast materials

The barium sulfate contrast material is swallowed or given orally and is used to enhance X-ray and CT images of the gastrointestinal tract. This test is applied to body parts such as the pharynx, esophagus, stomach, small intestine and large intestine. 

2.   Rectal contrast materials

In these tests, the barium sulfate is also administered via enema (through the rectum) is used to enhance X-ray and CT images of the lower gastrointestinal tract (colon and rectum). 

3.   Intravenous contrast materials

To perform this type of exam, iodinated and gadolinium materials are injected, which improve the images of internal organs (heart, lungs, liver, adrenal glands, kidneys, pancreas, gallbladder, spleen, uterus, and bladder), the gastrointestinal tract (stomach, small intestine and large intestine), arteries and veins of the body (vessels of the brain, neck, chest, abdomen, pelvis and legs), soft tissue (muscles, fat and skin), brain and breast.

Procedures

Because contrast materials have a risk of allergies or adverse reactions, you should inform your doctor about:

  • Any allergies you have.
  • Drugs that you are currently taking.
  • Recent · Diseases, surgery, etc..
  • History of asthma and hay fever (if present)
  • History of heart disease, diabetes, kidney disease, thyroid problems or sickle cell disease.

You will be given specific instructions on how to prepare for your exam.

Side Effects

1.   Barium Sulfate

You may have the following side effects. You should tell your doctor, in case they worsen or do not disappear:

  • Stomach cramps, diarrhea, nausea, vomiting, constipation.

Likewise, notify your doctor immediately about any of these symptoms:

  • Hives, itching, redness, swelling of the throat, difficulty breathing or swallowing, hoarseness, agitation, confusion, rapid heartbeat and bluish skin.

2.   Iodinated material

You may have the following side effects. You should tell your doctor, in case they worsen or do not disappear:

  • Nausea and vomiting, headache, itching, hot flashes, moderate skin irritation or rash

Mild reactions include: severe irritation of the skin or hives, wheezing, abnormal heart rhythms, high or low blood pressure, shortness of breath or difficulty breathing.

Severe reactions include difficulty breathing, heart failure, swelling of the throat or other parts of the body, seizures and abnormally low blood pressure. 

3.    Contrast Induced Nephropathy

Patients with compromised renal function should be given special consideration before receiving iodinated contrast material into a vein or artery. Such patients are at risk of developing contrast-induced nephropathy, which worsens pre-existing damage in the kidney.

Anesthesia

Anesthesia involves the use of anesthetics that cause loss or reduction of sensation in the body. These drugs are used to help patients better tolerate medical and surgical procedures.

The types of anesthesia that are currently divided in two:

  • Local: it blocks the sensation of pain in a specific area of ‌‌the body, the patient does not sleep; however, can be used in combination with administering a sedative to make the patient feel drowsy and more comfortable during surgery.

Local anesthesia can be administered topically, applied to the surface of the skin in a cream or an adhesive patch; epidural, an administered injection that causes loss of sensation by blocking nerve transmission at or near the spine, is used to block the movement of the waist to the toes.

For its part, spinal anesthesia involves the injection of an anesthetic into the fluid-filled space surrounding the spinal cord. 

  • General: General anesthetics cause unconsciousness in the patient. There are many different medications used in the anesthesia, each with its own power, purpose and duration.

General anesthesia is achieved by administration of inhaled gases and the patient will not remember having had any medical procedure. It should be noted that the patient is not breathing on their own, they requires a machine called anesthesia ventilator.

Sedation

Sedatives are medications that alter the consciousness of a patient to minimize pain, anxiety and discomfort that may be caused by undergoing surgery, and you may or may not remember the medical procedure.

There are two levels of sedation:

  • Minimum and moderate where the patient will feel relaxed and in some cases, you may stay awake. At this level of sedation, the patient will respond to verbal stimulus, you can follow your doctor's instructions and breathe for yourself.
  • Deep sedation, the patient will be asleep until the medication loses its effect. Deep sedation is usually administered by an anesthesiologist or anesthetist nurse .

Imagine procedure with Anesthesia

  • Must inform your doctor of any medication you are taking and any allergies you have.
  • It is important to share your medical history with your doctor to determine the type and amount of anesthesia to be used.
  • Before the procedure, you may need to do a blood test to determine if the liver and kidneys are functioning well, and if the blood clots normally.
  • In case you’re a woman, you should tell your doctor if you are pregnant or breast-feeding a baby.
  • It is possible to be told not to take or drink anything for six to eight hours before an imaging procedure with anesthesia or sedation.
  • Must take off your clothes, jewelry, eyeglasses and any metal objects and wear a gown during the x-ray examination
  • After taking sedatives or been administered anesthesia, your memory may be affected temporarily.

* In general, anesthesia and sedation are safe for most patients. Patients are carefully monitored when receiving any anesthetic, including sedation.

Side effects and allergic reactions

When anesthesia is administered by injection, the patient may feel numbness or tingling for a few days, and for epidural analgesia, they may experience headache.

The most common complications after general anesthesia are: nausea, vomiting, minor allergic reactions, dizziness, headache, sore throat, changes in blood pressure and pain. Easily treated with medication.

The most serious complications that may arise are: allergic reactions, strokes and heart attacks.

The patients most likely to develop problems due to anesthesia are those with: 

  • A history of congenital heart disease
  • Esophageal reflux - acid and food that come back to the mouth after consumption
  • Reactive airway disease
  • Increased intracranial pressure
  • Abnormal respiratory airways
  • Access disorders
  • Problems of the heart
  • Sleep problems

Pregnancy
Before any imaging study, women should always inform your doctor if they are pregnant, since many of the imaging tests cannot be performed in that state.

Only if very necessary for a surgical procedure, anesthesia can be administered with care to protect the fetus and the mother.

For their part, women who are breastfeeding can receive normal doses of local anesthetics without affecting their child, but should consult their doctor before taking any medication that could be passed to the baby when breastfeeding.