What do RBC (Red Blood Cell) and NV (Nausea and Vomiting) mean in a medical context?

Medical Terminology: RBC and NV

RBC stands for Red Blood Cell, the oxygen-carrying cells in blood, while NV stands for Nausea and Vomiting, a common symptom complex in medical practice.

Red Blood Cell (RBC)

RBCs are polymorphic, inherited structures that form the foundation of oxygen transport and constitute key components of hematologic assessment. 1

Structure and Function

• RBCs contain hemoglobin and are responsible for oxygen-carrying capacity throughout the body. 2
• Blood group antigens on RBC membranes contribute to membrane structural integrity, transport molecules through the membrane, serve as receptors for extracellular ligands, and function as adhesion molecules and enzymes. 1
• RBC membrane structures maintain the architecture necessary for proper cell function and survival in circulation. 1

Clinical Assessment

• Complete blood count (CBC) provides critical information on RBC size, shape, and hemoglobin concentration to detect and characterize anemia. 2
• RBC indices (mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration) suggest potential causes of anemia in specific patients. 2
• Peripheral blood smear examination combined with RBC histograms and indices provides the most accurate assessment of RBC morphology for anemia detection. 2
• RBC morphology assessment includes evaluation of shape, size, color, inclusions, and arrangement to establish differential diagnoses in anemic patients. 3

Clinical Significance

• In microcytic anemia, RBC morphology increases or decreases the diagnostic likelihood of thalassemia. 3
• In normocytic anemias, morphology differentiates among blood loss, marrow failure, and hemolysis. 3
• In macrocytic anemias, RBC morphology guides diagnostic considerations toward either megaloblastic or nonmegaloblastic causes. 3

Nausea and Vomiting (NV)

NV represents a symptom complex requiring systematic evaluation and treatment based on underlying etiology and patient life expectancy. 4

Classification and Timing

• Acute NV occurs within the initial 24 hours after chemotherapy. 4
• Delayed NV manifests later than 24 hours after chemotherapy. 4
• Anticipatory NV develops days to hours before chemotherapy administration. 4

Common Etiologies to Evaluate

• Medication-induced causes require discontinuation of unnecessary medications and checking blood levels of necessary medications (digoxin, phenytoin, carbamazepine, tricyclic antidepressants). 4
• Gastrointestinal causes include severe constipation/fecal impaction, gastroparesis, bowel obstruction, and gastric outlet obstruction from intra-abdominal tumor or liver metastasis. 4
• Central nervous system involvement, metabolic disorders, electrolyte disturbances, infection, and cachexia syndrome all contribute to NV. 4
• In advanced cancer patients, NV may be secondary to cachexia syndrome (chronic nausea, anorexia, asthenia, changing body image, and autonomic failure). 4

Pharmacologic Management Algorithm

First-line treatment consists of dopamine receptor antagonists titrated to maximum benefit and tolerance. 4, 5

Initial Therapy

• Metoclopramide 10-20 mg every 6 hours, prochlorperazine 5-10 mg every 6 hours, or haloperidol 0.5-2 mg every 4-6 hours serve as first-line dopamine receptor antagonists. 5, 6
• Olanzapine 2.5-5 mg daily is particularly effective and stimulates appetite. 5
• Around-the-clock dosing schedules provide the most consistent benefit rather than as-needed administration. 4, 5
• If anxiety contributes to NV, add lorazepam 0.5-1 mg every 4 hours as needed. 4, 5

Second-line Therapy for Persistent Symptoms

• Add 5-HT3 receptor antagonist (ondansetron 4-8 mg every 8-12 hours, granisetron 1 mg twice daily, or palonosetron 0.25 mg IV) when first-line therapy fails. 4, 5
• Consider adding anticholinergic agents (scopolamine) or antihistamines (meclizine) for additional symptom control. 4, 5

Third-line Therapy for Refractory Cases

• Add corticosteroid (dexamethasone 4-8 mg daily) which reduces nausea and stimulates appetite. 4, 5
• Consider continuous IV/subcutaneous infusion of antiemetics for intractable NV. 4, 5
• Opioid rotation should be considered if the patient is on opioids, as these may contribute to symptoms. 5, 7

Special Considerations

Elderly Patients

• Start with reduced doses (25-50% lower) in elderly patients, such as metoclopramide 5-10 mg three times daily or olanzapine 2.5 mg daily. 6
• Monitor closely for extrapyramidal side effects with dopamine antagonists and sedation with olanzapine. 5, 6
• Avoid long-term benzodiazepine use due to increased sensitivity in elderly populations. 6

End-of-Life Care

• Non-pharmacologic therapies (acupuncture, hypnosis, cognitive behavioral therapy) and cannabinoids may be considered in dying patients. 4

Critical Pitfalls to Avoid

• Never use antiemetics in suspected mechanical bowel obstruction, as this masks progressive ileus and gastric distension. 7
• Avoid starting with excessively high doses in elderly or debilitated patients. 5
• Do not fail to treat around-the-clock for persistent symptoms rather than using as-needed dosing. 5
• Monitor for extrapyramidal symptoms with dopamine antagonists, particularly in young males. 7
• Watch for QTc prolongation when using ondansetron, especially combined with other QT-prolonging agents. 7