Common Procedures in the NICU 

Most frequent blood tests performed in the NICU:

1. Arterial Blood Gas: This test, which is also called an ABG, is the most accurate measurement of the chemical components to assess breathing status. ABG evaluates the level of oxygen, carbon dioxide, pH and other chemical components of the blood. Blood samples for this test may be drawn from the umbilical artery catheter (UAC) or another artery in a one-time needle stick (most frequently in the radial artery, on the thumb side of the wrist). 
    
2. Capillary Blood Gas (CBG) or Venous Blood Gas (VBG): These tests also evaluate the level of carbon dioxide, pH and other chemical components of the blood but the oxygen amount is less accurate because the oxygen level of the blood in the capillaries is already depleted and on its way back to the heart and lungs. This sample is taken from a heel stick for capillary blood gas or from a venous stick for venous blood gas. Although it is a less accurate evaluation of oxygenation than an ABG, it can be used as a screening tool for respiratory issues.
    
3. Complete Blood Count (CBC): This is a blood test that looks at the components of blood including the hemoglobin, hematocrit, platelets, red blood cell count, white blood cell count, and the differential of the white blood cells (which white blood cells are present and in what amounts).
    
   • Hemoglobin: Is a major portion of the red blood cells; enables the body to carry oxygen from the lungs to the tissues to be utilized by the body and carry carbon dioxide from the body to the lungs to be removed.
      
   • Hematocrit: Is another portion of the red blood cells; enables us to determine the percentage of red blood cells present in the body. The normal percentage will vary according to age, sex, and the laboratory performing the test. Too high of a percentage can indicate dehydration, or potentially blood loss along with a few other issues. Too low of a hematocrit can indicate anemia.
      
   • Platelets: Platelets are vital to the coagulation process that is necessary to stop bleeding. The platelet count is an important screening test of platelet function. If the platelet count is too low the patient may be prone to spontaneous bleeding that is difficult to control. Bleeding can occur in various parts of the body. If the platelet count is too high this may be an indicator of massive blood loss, infection, or a number of other disorders that require further testing.
      
   • Red Blood Cell Count: By itself is not diagnostic but can be used to calculate other helpful values that are diagnostic.
      
   • White Blood Cell Count: Can be an indicator of an infection or inflammation in the body. The white blood cell count should be used in conjunction with a white blood cell differential. The differential evaluates each of the five types of white blood cells: neutrophils, eosinophils, basophils, lymphocytes and monocytes, to give a better idea of the immune system response.
      
4. Electrolytes ("Lytes"): Electrolytes are the basic body chemicals that include sodium, potassium, chloride, calcium and magnesium. These chemicals are essential to the function of all body cells. Normally, the electrolytes are supplied by the food (formula or breast milk) the baby eats. If the levels of these essential elements are too high or low, the cells are unable to function properly. Therefore, electrolyte levels in the blood must be measured and the ingredients of the IV solutions are adjusted accordingly.
    
5. Septic work-up: These tests include blood cultures, urine culture and a spinal tap to evaluate the spinal fluid for infection and to culture. All of the samples go to the lab and a "culture and sensitivity" is done. This means each specimen is allowed to grow and then examined under a microscope for the presence of microorganisms that cause infection. These microorganisms may be bacterial, viral or fungal. If any are found, the baby has an infection that needs to be treated aggressively with IV antibiotic, antifungal or antiviral medications. It takes 24 to 48 hours to get culture results, so to be safe, antibiotics are started as soon as the specimens are gathered and before the culture results are known. With cultures, sensitivities are done when an infection is found. The sensitivities identify which medication is most effective against the infection. For this reason the medications may change once the final results of the cultures are received.
    
6. Blood Sugars or Glucose: This test can be done at the bedside with one drop of blood taken from a heel stick. The blood is placed on a chemically treated strip. If the result is very high or low, a larger amount of blood may be drawn to get a more accurate measurement of the blood sugar. The amount of sugar in the IV solutions can be adjusted to keep the sugars within the normal range.
    
7. BUN and Creatinine: This is a blood test that assesses kidney function. A high  BUN measurement can indicate renal (kidney) disease or reduced blood flow to the kidneys, along with a few other potential complications. A low BUN measurement can indicate overhydration, as well as some other potential issues.  The creatinine test is a slightly more sensitive test of renal function. An elevated creatinine level indicates decreased kidney function.
    
8. Bilirubin: Bilirubin is a byproduct of the breakdown of red blood cells. The liver is responsible for ridding the body of this byproduct. Bilirubin can build up in the blood when the body is not capable of getting rid of it, either because too much is being produced or the liver is not mature enough to keep up with the amount being made. An increase in the level of bilirubin may be treated with phototherapy or bililights. These lights help the body break down and excrete the bilirubin in the urine and stool.

Urine tests

The kidneys of a newborn are very sensitive to change, including changes in general health. Some changes that can cause altered urine production include increased or decreased blood pressure, change in blood volume (there may not be enough blood in the baby's system to perfuse the kidneys well), an infection, a change in the pH of the blood (which may be related to respiratory issues), or a change in any of the electrolyte or glucose levels in the blood. The urine can be used as a screening tool for some of these issues.
 
The amount of urine produced is monitored by strict measurement of intake and output. To determine output, the amount of urine, stool, drainage from any tube (NG/OG, chest tube) is measured. Intake is the amount we put into the baby through an IV, tubes or mouth. For example, the amount of fluids given via the NG/OG tube is tracked. The amount of intake and output should closely match. Changes in the amount of urine produced can be a clue to changes in the overall health. A small amount of urine is used to test for a variety of things right in the NICU. Some of the tests include: specific gravity (which determines how concentrated the urine is), urine pH, hematuria (to test for blood), proteinurea (to test for protein) and glucosuria (to test for sugar). If there is too much of these elements in the blood, they will be excreted by the kidneys in the urine.
 
Sometimes urine is collected for the lab to evaluate. This urine sample may be obtained in a variety of ways. If it is part of a septic (infection) workup, the urine may be collected by a suprapubic tap, in which a needle is inserted through the baby's lower abdomen and into the baby's bladder. Another method of collecting urine is taping a special plastic bag over the baby's vaginal area or penis. As the baby urinates it is collected in the bag. This would be a "clean catch" sample. The urine can also be collected by inserting a soft tube through the urethra into the bladder. This tube can be left in place to drain into a collection bag (for accurate intake and output) or it can be removed once some urine is collected.

Weight

Your baby will be weighed nearly every day, depending on the stability of your infant. This helps to assess the baby's well-being. If the baby is gaining too much or too little weight, staff will evaluate the intake and output, blood pressure, heart rate, and blood levels that can help gauge kidney function and chemistry levels (electrolytes) and/or rule out infection or other health issue. Calorie intake will also be reviewed. Optimal intake levels are based on the baby's weight and adjustments need to be made as the baby grows. As the baby begins to eat by mouth, calories received from the IV solution will be adjusted to balance the calories received from food. The quantity of fluids being consumed is also considered. Calories can be added to breast milk and/or formula so the baby gets the same amount of calories in a smaller amount of fluid.

X-ray

X-ray is a very important diagnostic technique used commonly in the NICU. Although X-ray involves exposure to radiation, the amounts of exposure are controlled and monitored closely. Unnecessary X-rays are avoided. If the genitals are within the area of exposure, they will be covered with a lead shield. X-rays are performed for a variety of reasons, such as determining placement of various tubes (ETT-endotracheal tube, UAC-umbilical artery catheter, UVC-umbilical venous catheter, chest tube, NG/OG-nasal gastric or oral gastric), heart size, lung expansion or infiltrates (potential infection in the lungs) and general bone structure.

Ultrasound and echocardiogram:

An ultrasound is a noninvasive diagnostic technique used routinely in the NICU. You may have had an ultrasound during pregnancy to evaluate the baby's size, anatomy and perhaps determine the sex of your baby. Ultrasound uses sound waves to evaluate internal anatomy. A transducer along with gel (to get a closer contact) emits and receives these sound waves as they bounce off the anatomy, producing a two-dimensional picture in varying shades of gray. The denser the structure, the brighter or more echogenic the image is.
 
Ultrasound cannot scan bone, lungs, or the bowel. In fact, bone, fat and gas can act as barriers to ultrasound and a poorer quality picture will result. Doppler ultrasound can be used to evaluate blood flow (looking for narrowing or blockage), direction, and estimate speed or velocity. An echocardiogram uses the ultrasound along with the Doppler to look at anatomy and evaluate the blood flow of the heart. An echocardiogram may be done on the baby before birth and then again after birth to get a more accurate picture of the heart anatomy and blood flow. These studies can be done at the baby's bedside without sedation or dye.

CT (computed tomography) scan

CT scan involves aiming a very narrow beam of radiation at a specific layer of tissue and getting a two dimensional computer assisted image of the internal structures. As in a standard X-ray, bone absorbs more of the X-ray and appears white on the image and air absorbs the least amount of the x-ray and appears black. CT provides a very precise, detailed picture despite overriding bones or overlapping body structures. However, CT is nonportable and to get an accurate scan the baby need to stay very still. That means a critically ill baby may need to go to the radiation department and be sedated to get a CT scan. Also, CT involves exposure to radiation so they need to be used responsibly to avoid cumulative radiation doses.

MRI (magnetic resonance imaging)

MRI works based on an interaction between a large magnet found in the imaging equipment and the atoms in the body.  The nuclei of these atoms are aligned and then shifted out of alignment to create an image for diagnostics. MRI does not use radiation, is noninvasive and has no side effects. The disadvantages of MRI are that it has a high cost, it is not portable, and requires an extended length of time to collect the data. However, the quality of the images is excellent, so MRIs may be used more commonly with newborns in the future.