6.3 Gastrointestinal Complications, Ileus, Early Enteral Nutrition, and Curling's Ulcer Prophylaxis

6.3 Gastrointestinal Complications, Ileus, Early Enteral Nutrition, and Curling's Ulcer Prophylaxis

Core Knowledge: The gastrointestinal (GI) tract is often termed the "motor" of Systemic Inflammatory Response Syndrome (SIRS) and Multiple Organ Dysfunction Syndrome (MODS) in severe burn trauma. Splanchnic vasoconstriction during burn shock starves the intestinal mucosa, leading to mucosal barrier breakdown, toxic bacterial translocation, and Curling's ulcer formation. Proactive burn nursing management requires immediate GI decompression, early enteral feeding initiation within 6 to 12 hours of admission, and vigilant intra-abdominal pressure surveillance.

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1. Splanchnic Hypoperfusion and Gut Barrier Breakdown

During the initial hours of burn shock, compensatory neuroendocrine mechanisms prioritize arterial perfusion to the brain and heart at the direct expense of the splanchnic circulation.

                    PATHOPHYSIOLOGY OF THE "GUT MOTOR" OF BURN SEPSIS
  ┌────────────────────────────────────────────────────────────────────────────────────────┐
  │ Thermal Trauma & Hypovolemic Burn Shock (≥20% TBSA)                                    │
  │                                           │                                            │
  │                                           ▼                                            │
  │  Massive Sympathetic Adrenergic Surge ──► Epinephrine, Vasopressin & Angiotensin II    │
  │                                           │                                            │
  │                                           ▼                                            │
  │  Selective, Intense Splanchnic Vasoconstriction (Mesenteric Blood Flow Drops 50–60%)    │
  │                                           │                                            │
  │                                           ▼                                            │
  │  Ischemia of Intestinal Mucosa & Epithelial Villous Tips ──► ATP Depletion & Necrosis  │
  │                                           │                                            │
  │                                           ▼                                            │
  │  Disruption of Claudin / Occludin Tight Junctions ──► Hyperpermeable Gut Barrier       │
  │                                           │                                            │
  │                                           ▼                                            │
  │  Translocation of Intraluminal Bacteria & Endotoxin (LPS) into Mesenteric Lymphatics   │
  │                                           │                                            │
  │                                           ▼                                            │
  │  Activation of Gut-Associated Lymphoid Tissue (GALT) & Kupffer Cells ──► Systemic SIRS│
  │                                           │                                            │
  │                                           ▼                                            │
  │            SECONDARY MULTIPLE ORGAN DYSFUNCTION SYNDROME (MODS) & LATE SEPSIS          │
  └────────────────────────────────────────────────────────────────────────────────────────┘

Cellular Mechanisms of Gut Barrier Failure

1. Ischemic Villous Tip Necrosis: The microscopic architecture of intestinal villi relies on a countercurrent microvascular exchange mechanism, rendering the tips exceptionally sensitive to hypoxia. Splanchnic hypoperfusion causes rapid sloughing of villous tip enterocytes within hours of injury.
2. Breakdown of Intercellular Tight Junctions: Ischemia and reactive oxygen species disrupt zonula occludens (ZO-1) and occludin protein complexes, transforming the semipermeable mucosal lining into an open, porous conduit.
3. Bacterial Translocation: Gram-negative enteric bacilli (E. coli, Klebsiella) and toxic lipopolysaccharide (LPS) endotoxins migrate directly across the compromised mucosal membrane into mesenteric lymph nodes and the portal vein, fueling persistent hyperinflammatory shock.

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2. Paralytic Ileus and Gastric Decompression

Paralytic ileus is an almost universal complication in patients with burns exceeding 20% TBSA.

Pathophysiological Drivers:

• Sympathetic Hyperactivity: High circulating catecholamines inhibit gastrointestinal smooth muscle motility through alpha-2 and beta-2 adrenergic activation.
• Electrolyte Derangements: Hypokalemia, hypomagnesemia, and metabolic acidosis impair smooth muscle membrane depolarization.
• Opioid-Induced Bowel Dysfunction: Continuous opioid infusions for severe background burn pain further paralyze enteric opioid mu-receptors.

                          PARALYTIC ILEUS MANAGEMENT PROTOCOL
  ┌───────────────────────────────────────────────────────────────────────────────────────┐
  │ • Immediate Insertion of Large-Bore Nasogastric (NG) or Orogastric (OG) Tube (16–18 Fr)│
  │ • Connect to Low Intermittent Suction (30–40 mmHg) for Immediate Decompression        │
  │ • Continuous Monitoring of Gastric Output Volume, Color, and pH                        │
  │ • Serial Abdominal Exams: Palpate for Rigidity, Auscultate Bowel Sounds, Monitor Girth │
  │ • Avoid Prolonged NPO Status: Transition to Post-Pyloric Feeding Despite Gastric Ileus │
  └───────────────────────────────────────────────────────────────────────────────────────┘

[!WARNING] Failure to decompress the stomach in acute burn shock leads to acute gastric dilatation, massive non-bilious or bilious vomiting, and catastrophic pulmonary aspiration. In an intubated burn patient, aspiration of acidic gastric contents triggers severe Mendelson's syndrome, necrotizing pneumonia, and refractory ARDS.

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3. Early Enteral Nutrition (EEN): The Gold Standard

Modern burn critical care has replaced the historical practice of resting the gut with Early Enteral Nutrition (EEN).

                    BENEFITS OF EARLY ENTERAL NUTRITION (≤6–12 HOURS)
  ┌─────────────────────────────────┬─────────────────────────────────┬─────────────────────────────────┐
  │      MUCOSAL PRESERVATION       │       METABOLIC BLUNTING        │       IMMUNE ENHANCEMENT        │
  ├─────────────────────────────────┼─────────────────────────────────┼─────────────────────────────────┤
  │ • Directly fuels enterocytes via│ • Blunts catecholamine &        │ • Stimulates secretory IgA      │
  │   luminal absorption            │   glucagon hypersecretion       │   production from GALT          │
  │ • Preserves microvillous height │ • Reduces resting energy        │ • Inhibits bacterial adherence  │
  │ • Maintains occludin tight      │   expenditure (REE) surge       │   to mucosal wall               │
  │   junction integrity            │ • Attenuates skeletal muscle    │ • Decreases bloodstream sepsis  │
  │ • Stimulates mesenteric blood   │   proteolysis and nitrogen loss │   by >50% compared to TPN       │
  │   flow (postprandial hyperemia) │ • Lowers hypermetabolic core set│ • Accelerates wound healing     │
  └─────────────────────────────────┴─────────────────────────────────┴─────────────────────────────────┘

Clinical Implementation Guidelines

• Timing: The American Burn Association (ABA) recommends initiating enteral tube feeding within 6 to 12 hours of admission (or as soon as resuscitation begins).
• Starting Rate: Begin with continuous trophic feeding (e.g., 10–20 mL/hr of a high-protein, peptide-based or intact formula) and advance systematically over 24 to 48 hours to target caloric and protein goals determined by indirect calorimetry or Curreri formula.
• Gastric vs. Post-Pyloric (Nasojejunal) Feeding:
  • Gastric Feeding: Feasible in smaller burns or hemodynamically stable patients. However, gastroparesis frequently causes elevated gastric residual volumes (GRVs) and increased aspiration risk.
  • Post-Pyloric / Nasojejunal (NJ) Feeding: The gold standard in severe burns (>= 30–40% TBSA). Because the small intestine retains motility and absorptive capacity even in the presence of severe gastric ileus, post-pyloric feeding permits continuous, high-volume feeding with minimal aspiration risk. Crucially, post-pyloric feeds can be safely continued intraoperatively during surgical excision and grafting, eliminating the catastrophic caloric deficits associated with repetitive "NPO after midnight" orders.
• Prokinetic Pharmacotherapy: If gastric emptying is delayed, administer IV metoclopramide (10 mg IV q6h) and/or IV erythromycin (125–250 mg IV q8h) to stimulate motilin receptors and enhance gastric transit.

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4. Curling's Ulcer (Acute Burn Stress Gastroduodenopathy)

First described by British surgeon Thomas Blizard Curling in 1842, Curling's ulcer refers to acute, severe stress-induced erosive gastritis and gastroduodenal ulceration occurring specifically in extensive burn trauma.

                          PATHOGENESIS OF CURLING'S ULCER
  ┌────────────────────────────────────────────────────────────────────────────────────────┐
  │ Severe Thermal Burn Trauma (Splanchnic Vasoconstriction & Hypovolemia)                 │
  │                                           │                                            │
  │                                           ▼                                            │
  │  Profound Ischemia of Gastric & Duodenal Mucosa ──► Depleted Mucosal Prostaglandins   │
  │                                           │                                            │
  │                                           ▼                                            │
  │  Loss of Protective Bicarbonate Mucus Barrier & Microvascular Sloughing                │
  │                                           │                                            │
  │                                           ▼                                            │
  │  Massive Vagal / Catecholamine Hypersecretion of Gastric Hydrochloric Acid (HCl)       │
  │                                           │                                            │
  │                                           ▼                                            │
  │  Acid Back-Diffusion into Denuded Submucosa ──► Deep, Solitary / Multiple Ulcerations │
  │                                           │                                            │
  │                                           ▼                                            │
  │            CATASTROPHIC UPPER GI HEMORRHAGE OR DUODENAL PERFORATION                    │
  └────────────────────────────────────────────────────────────────────────────────────────┘

Clinical Presentation and Prevention

Historically, Curling's ulcer carried a catastrophic mortality rate (>50%) from sudden, massive upper GI bleeding. In modern burn units, the incidence has dropped below 1–2% due to protocolized multimodal prophylaxis:

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5. Intra-Abdominal Pressure (IAP) & Abdominal Compartment Syndrome (ACS)

During massive burn shock resuscitation (frequently associated with fluid creep exceeding $>250\text{ mL/kg}$ or $>6\text{ mL/kg}/%\text{TBSA}$), massive crystalloid extravasation into the retroperitoneum and bowel wall causes profound visceral edema, triggering Intra-Abdominal Hypertension (IAH) and life-threatening Abdominal Compartment Syndrome (ACS).

               INTRA-ABDOMINAL PRESSURE SPECTRUM & MANAGEMENT PROTOCOL
  ┌──────────────────────┬──────────────────────┬──────────────────────────────────────────┐
  │ Classification       │ Bladder Pressure     │ Clinical Actions & Nursing Management    │
  ├──────────────────────┼──────────────────────┼──────────────────────────────────────────┤
  │ Normal Adult IAP     │ 0 – 5 mmHg           │ Baseline monitoring in ICU.              │
  │ ICU Post-Burn Normal │ 5 – 7 mmHg           │ Common during fluid resuscitation.       │
  ├──────────────────────┼──────────────────────┼──────────────────────────────────────────┤
  │ Intra-Abdominal      │ Grade I:  12–15 mmHg │ • Initiate hourly bladder pressure checks│
  │ Hypertension (IAH)   │ Grade II: 16–20 mmHg │ • Decompress stomach (NG tube) & rectum  │
  │                      │                      │ • Minimize excessive crystalloids        │
  │                      │                      │ • Ensure adequate neuromuscular blockade │
  ├──────────────────────┼──────────────────────┼──────────────────────────────────────────┤
  │ Abdominal            │ IAP > 20 mmHg        │ • MEDICAL EMERGENCY                      │
  │ Compartment          │ PLUS new organ       │ • Spiking peak airway pressures (>40)    │
  │ Syndrome (ACS)       │ dysfunction          │ • Worsening oliguria / anuria            │
  │                      │                      │ • Refractory shock / decreased CO        │
  │                      │                      │ • Emergent decompressive laparotomy      │
  └──────────────────────┴──────────────────────┴──────────────────────────────────────────┘

Bladder Pressure Transduction Technique:

• Measure IAP at end-expiration in the complete supine position.
• Instill exactly 20 to 25 mL of sterile saline into the bladder via a closed Foley catheter transducer system.
• Zero the pressure transducer at the iliac crest in the mid-axillary line.
• Calculate Abdominal Perfusion Pressure (APP): $\text{APP} = \text{Mean Arterial Pressure (MAP)} - \text{Intra-Abdominal Pressure (IAP)}$
• Clinical Goal: Maintain $\text{APP} \ge 60\text{ mmHg}$ to ensure adequate mesenteric and renal cortical blood flow.