ICU · gi-nutrition

Acute Severe Pancreatitis — Comprehensive (Revised Atlanta, WATERFALL, PANTER, Step-Up, Infected Necrosis)

Also known as Severe acute pancreatitis · Necrotising pancreatitis · Infected pancreatic necrosis · WATERFALL trial · PANTER trial · TENSION trial · Step-up approach · Walled-off necrosis · Revised Atlanta classification · Pancreatic pseudocyst · BISAP score · Acute necrotic collection

Acute severe pancreatitis (approximately 15-20% of all acute pancreatitis) is defined by the Revised Atlanta Classification (2012) as acute pancreatitis with PERSISTENT organ failure lasting 48 hours — respiratory (PaO2/FiO2 <300), cardiovascular (SBP <90 despite fluids / need for vasopressors), or renal (creatinine 170 umol/L) — and carries a mortality of 15-30%. The two pathological phases dictate ICU management. EARLY PHASE (week 1): uncontrolled SYSTEMIC INFLAMMATION (SIRS) driven by pancreatic enzyme activation and cytokine storm (IL-6, TNF-alpha, IL-1) → capillary leak, 'third-space' fluid sequestration into the retroperitoneum and bowel wall → hypovolaemia, haemoconcentration, haemodynamic instability, AKI, and the early killers ARDS and shock. Aetiology: gallstones (1, ~40%), alcohol (2, ~30%), ERCP, hypertriglyceridaemia (11 mmol/L), drugs (azathioprine, mesalazine, didanosine, sodium valproate, thiazides), trauma, post-ERCP, autoimmune, idiopathic. EARLY ICU MANAGEMENT is SUPPORTIVE and evidence-based: (1) GOAL-DIRECTED FLUID RESUSCITATION with lactated Ringer's — the WATERFALL trial (NEJM 2022, de-Madaria) proved AGGRESSIVE fluids (20 mL/kg bolus + 3 mL/kg/hr) CAUSE HARM (fluid overload 20.5% vs 6.3%, no outcome benefit) — use moderate, goal-directed resuscitation (1.5 mL/kg/hr + small boluses only if hypovolaemic); (2) EARLY ENTERAL NUTRITION within 48 hours (NOT 'NPO + TPN' — old practice refuted by multiple RCTs and meta-analyses) — maintains gut mucosal barrier, reduces bacterial translocation, reduces infected necrosis and mortality; oral or nasogastric route is as effective as nasojejunal in most patients; (3) NO PROPHYLACTIC ANTIBIOTICS — the PANTER trial, ACG (Tenner 2024), and IAP/APA guidelines all confirm antibiotics do NOT prevent infected necrosis and increase resistance, fungal superinfection, and C. difficile; give antibiotics ONLY for documented infection (infected necrosis, cholangitis, pneumonia); (4) analgesia (opioid — morphine/fentanyl, PCA); (5) ERCP within 24-72h ONLY if concomitant cholangitis or ongoing biliary obstruction. LATE PHASE (week 2+): local complications dominate — pancreatic/peripancreatic NECROSIS (sterile in ~70%, infected in ~30%), walled-off necrosis, pseudocyst. Infected necrosis is the principal late killer (mortality 30-40% historically). Diagnosis: gas within necrosis on CT is pathognomonic; otherwise clinical deterioration + positive fine-needle aspiration (FNA) culture. Management of infected necrosis is the STEP-UP APPROACH (PANTER trial, NEJM 2010, van Santvoort): percutaneous or endoscopic DRAINAGE first, then minimally-invasive necrosectomy only if drainage fails — step-up halved the composite of major complications/death (40% vs 69%) versus open necrosectomy, and 35% needed drainage alone. The TENSION trial (Lancet 2018, van Brunschot) showed ENDO- scopic step-up (EUS-guided transluminal drainage ± endoscopic necrosectomy) is NOT superior to surgical step-up for the primary endpoint but causes FEWER pancreatic fistulas and shorter hospital stay — endoscopic step-up is now the preferred first approach when expertise exists. CRITICAL: DELAY invasive intervention ~4 weeks whenever possible (let necrosis become walled-off/encapsulated → safer drainage). Scoring: APACHE II =8, Ranson =3, BISAP =3, CRP 150 mg/L at 48h, and the Revised Atlanta organ-failure criteria all predict severity. Systemic complications: SIRS → MODS, ARDS (lung-protective ventilation), AKI (CRRT if shocked), abdominal compartment syndrome (monitor bladder pressure), and sepsis from infected necrosis.