8.3 Diagnostic Tests and Procedures

Safety Before, During, and After Procedures

Diagnostic testing is heavily represented in Reduction of Risk Potential. The LPN/VN reinforces teaching, verifies preparation, confirms that informed consent is signed (a witness role — the provider obtains consent), and performs the focused post-procedure monitoring that detects bleeding, airway loss, or impaired perfusion early.

Imaging and Contrast

Iodinated contrast rules the NCLEX expects: assess for iodine/shellfish allergy, check BUN and creatinine first, hold metformin 48 hours after the dye (lactic acidosis risk), and push fluids afterward to flush the kidneys. Watch for delayed reactions — rash, itching, dyspnea.

Cardiac Testing

Post-cardiac-catheterization priorities: assess the distal (pedal) pulse, the puncture site, and limb color/sensation every 15 minutes initially, keep the affected leg straight and the patient on bed rest (often 2-6 hours for a femoral approach), and push fluids to clear contrast. Worked example: one hour after a femoral cath you find a cool, mottled foot with a weak dorsalis pedis pulse — suspect arterial occlusion and notify the RN/provider immediately while keeping the limb still.

Gastrointestinal Procedures

For a colonoscopy the bowel prep (GoLYTELY, MiraLAX) continues until output is clear yellow liquid; NPO after midnight. After barium, stool is chalky/white until it clears — teach the patient this is expected.

Procedures Involving the Airway or Throat

After EGD, ERCP, and bronchoscopy, the throat is anesthetized, so keep the patient NPO until the gag reflex returns (usually ~2 hours) to prevent aspiration. After bronchoscopy expect blood-tinged sputum, place in semi-Fowler's, and watch for respiratory distress and laryngospasm.

Thoracentesis and Lumbar Puncture

• Thoracentesis removes pleural fluid: position the patient leaning forward over a table, and afterward monitor for pneumothorax (sudden dyspnea, absent breath sounds, tracheal shift).
• Lumbar puncture samples cerebrospinal fluid: position fetal/side-lying with knees to chest; afterward keep the patient flat 4-8 hours and push fluids to prevent a post-dural "spinal" headache, and check the site for leakage.

Biopsies and Post-Care

After a liver biopsy, position on the right side so body weight tamponades the right-upper-quadrant site; take VS every 15 minutes × 4, then every 30 minutes × 4, and watch for the bleeding triad of rising pulse, falling BP, and abdominal pain. Bed rest follows for 6-8 hours.

Patient Teaching Checklist

Reinforce: the test's purpose; required prep (NPO, bowel prep, meds to hold such as metformin or anticoagulants); expected sensations; activity limits afterward; and which symptoms to report (bleeding, severe pain, fever, dyspnea). A common trap is selecting an answer that has the LPN/VN independently obtain consent — that is the provider's role; the LPN/VN witnesses the signature and confirms understanding.

Medications to Hold Before Procedures

Beyond metformin, the NCLEX-PN expects you to know which drugs to flag before invasive testing. Anticoagulants and antiplatelets — warfarin, heparin, clopidogrel, and even aspirin — are typically held before biopsies, catheterizations, and lumbar punctures because of bleeding risk; verify the hold order and check coagulation studies (INR, aPTT, platelets). For an iodinated-contrast study, screen for a true contrast allergy and pretreat with steroids and antihistamines only when ordered. Diabetics on insulin who must be NPO need a clarified insulin plan to avoid hypoglycemia.

The LPN/VN reinforces, but does not independently change, these orders.

Glucose Tolerance, Cultures, and Timing

Some diagnostics hinge on precise timing the LPN/VN controls. A fasting blood glucose requires 8 hours NPO; an oral glucose tolerance test draws a baseline, gives a measured glucose load, then draws at set intervals. Blood cultures should be drawn before the first antibiotic dose so the pathogen is captured — giving the antibiotic first is a classic wrong answer. A throat or wound culture is collected before starting topical antimicrobials.

Across all procedures the priority post-care theme repeats: protect the airway (NPO until gag returns), watch for bleeding (vital-sign trends, site checks), and preserve perfusion (distal pulses) — recognizing the early deviation and reporting it is the consistently tested LPN/VN action.