10.2 Gastrointestinal Symptom Management (CINV, Mucositis, Diarrhea)

Gastrointestinal Symptom Management (CINV, Mucositis, Diarrhea)

Gastrointestinal (GI) toxicities are among the most distressing and dose-limiting adverse effects of cancer chemotherapy, targeted agents, and radiation therapy. Advanced Practice Registered Nurses (APRNs) must apply guideline-based prophylactic protocols for chemotherapy-induced nausea and vomiting (CINV), institute evidence-based oral mucositis regimens, and execute rapid differential diagnosis and management of treatment-induced diarrhea.

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1. Chemotherapy-Induced Nausea & Vomiting (CINV) Pathophysiology & Risk Categorization

CINV is triggered through dual neurobiological pathways: the peripheral pathway (chemotherapy injures GI enterochromaffin cells, releasing serotonin that stimulates vagal afferent fibers to the emetic center) and the central pathway (circulating chemotherapy agents or metabolites directly stimulate the Chemoreceptor Trigger Zone [CTZ] in the area postrema of the fourth ventricle). Key neurotransmitters include Serotonin (5-HT3), Substance P (acting via Neurokinin-1 [NK1] receptors), Dopamine (D2), and GABA.

Emetogenic Risk Classification of Antineoplastic Agents

Antineoplastic agents are categorized by NCCN and ASCO based on their inherent emetogenic potential in the absence of antiemetic prophylaxis:

• High Emetogenic Chemotherapy (HEC) (>90% risk of emesis): Cisplatin, AC combination regimens (Doxorubicin or Epirubicin + Cyclophosphamide), Carboplatin (AUC $\ge 4$), Cyclophosphamide $>1,500\text{ mg/m}^2$, Dacarbazine, Ifosfamide $\ge 2\text{ g/m}^2$.
• Moderate Emetogenic Chemotherapy (MEC) (30-90% risk): Oxaliplatin, Irinotecan, Carboplatin (AUC $<4$), Cyclophosphamide $<1,500\text{ mg/m}^2$, Doxorubicin (non-AC), Temozolomide.
• Low Emetogenic Chemotherapy (LEC) (10-30% risk): Paclitaxel, Docetaxel, Fluorouracil (5-FU), Gemcitabine, Etoposide, Pemetrexed.
• Minimal Emetogenic Risk (<10% risk): Vincristine, Vinblastine, Bleomycin, Bevacizumab, Rituximab.

Clinical Patterns of CINV

• Acute CINV: Occurs within 0 to 24 hours post-chemotherapy; mediated predominantly by mucosal serotonin release. Peak onset 5-6 hours.
• Delayed CINV: Occurs $>24$ hours to 5-7 days post-chemotherapy; mediated primarily by Substance P acting on central NK1 receptors. Characteristic of cisplatin, carboplatin, cyclophosphamide, and doxorubicin.
• Anticipatory CINV: A conditioned psychological reflex triggered by sensory cues (smells, sights of clinic) from prior poor emetic control. Prophylaxis requires behavioral therapy and pre-treatment Lorazepam (0.5-1 mg PO/IV).
• Breakthrough CINV: Emesis occurring despite optimal prophylactic antiemetics, requiring rescue agents from a different drug class.
• Refractory CINV: Emesis occurring during subsequent chemotherapy cycles when prophylaxis and breakthrough rescue regimens have failed in prior cycles.

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2. Guideline-Based Antiemetic Prophylaxis Regimens

NCCN and ASCO consensus guidelines mandate prophylactic antiemetics initiated PRIOR to chemotherapy rather than reactive administration after nausea develops.

ASCO/NCCN 4-Drug Prophylactic Protocol for High Emetogenic Chemotherapy (HEC)

For all patients receiving HEC (e.g., Cisplatin or AC regimens), a 4-drug combination regimen is indicated:

Breakthrough CINV Management

When breakthrough nausea occurs, add one agent from a class not currently being utilized: Olanzapine (10 mg PO daily x 3 days if not used in primary prophylaxis), Prochlorperazine (10 mg PO/IV Q6H PRN), Metoclopramide (10-20 mg PO/IV Q6H PRN - monitor for extrapyramidal symptoms/tardive dyskinesia), Haloperidol (1-2 mg PO Q4-6H PRN), or Dronabinol (5 mg PO Q4-6H PRN).

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3. Alimentary Tract Mucositis Management

Oral mucositis occurs in up to 40% of standard chemotherapy patients and nearly 100% of patients receiving head/neck radiation or high-dose conditioning for hematopoietic stem cell transplantation (HSCT). The injury proceeds through 5 biological phases: Initiation (DNA damage/ROS formation) $\rightarrow$ Primary damage response (transcription factor activation) $\rightarrow$ Signal amplification (TNF-$\alpha$, IL-1$\beta$ surge) $\rightarrow$ Ulceration/Infection (painful pseudomembranous denudation) $\rightarrow$ Healing.

Evidence-Based Interventions

• Palifermin (Recombinant Human Keratinocyte Growth Factor - rhKGF): Indicated to decrease the incidence and duration of severe oral mucositis in patients receiving myeloblative conditioning followed by autologous HSCT. Administered as 60 mcg/kg/day IV for 3 consecutive days prior to conditioning and 3 consecutive days post-transplant (total 6 doses). Timing Rule: Do NOT administer within 24 hours before, during, or after myelosuppressive chemotherapy.
• Oral Cryotherapy: Swishing ice chips or ice water in the mouth for 30-45 minutes starting 5 minutes prior to bolus 5-Fluorouracil (5-FU) administration. Local vasoconstriction decreases mucosal exposure to short-half-life chemotherapy.
• Symptom Management: Bland oral rinses (0.9% saline + sodium bicarbonate every 2-4 hours). Topical mucosal coating agents (doxepin rinse, compounding "Magic Mouthwash" containing diphenhydramine, lidocaine, and aluminum hydroxide/magnesium hydroxide). Systemic transdermal/IV opioids for Grade 3-4 severe pain. Avoid chlorhexidine rinses for prevention as evidence shows lack of benefit.

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4. Chemotherapy-Induced Diarrhea (CTID) Management

Severe diarrhea causes profound dehydration, electrolyte collapse, hypovolemic shock, and sepsis. Two distinct etiologies must be recognized by the APRN:

Irinotecan-Induced Diarrhea Syndromes

1. Early-Onset Acute Diarrhea: Occurs during or within 24 hours of irinotecan infusion. Caused by direct inhibition of acetylcholinesterase, producing an acute cholinergic storm (diarrhea, diaphoresis, abdominal cramps, lacrimation, rhinorrhea, hypersalivation). Management: Atropine 0.25 mg to 1.0 mg IV or SC immediately (prophylactic atropine indicated for subsequent cycles).
2. Late-Onset Diarrhea: Occurs $>24$ hours post-infusion (median onset 5-8 days). Caused by luminal mucosal injury from the active biliary metabolite SN-38. Management: Immediate aggressive High-Dose Loperamide Protocol: Initiate 4 mg PO at first onset of loose stool, followed by 2 mg PO every 2 hours until the patient is diarrhea-free for 12 consecutive hours (nighttime dosing may be 4 mg every 4 hours).

Uncomplicated vs Complicated Diarrhea Protocols

• Uncomplicated CTID (Grade 1-2 without fever, neutropenia, or cramping): Standard loperamide (4 mg initial, then 2 mg Q4H). Low-residue diet, aggressive hydration (2-3 L fluids/day).
• Complicated CTID (Grade 3-4, or accompanied by fever, severe cramping, Grade 3-4 neutropenia, frank bleeding, or nausea/vomiting): Hold antineoplastic therapy. Initiate Subcutaneous Octreotide (100-150 mcg SC TID or continuous IV 25-50 mcg/hr, escalating up to 500 mcg SC TID). Stool diagnostic workup (C. difficile PCR, stool culture, ova/parasites) is mandatory before declaring non-infectious CTID. Initiate empiric broad-spectrum oral fluoroquinolone (Ciprofloxacin 500 mg BID) if neutropenic.