21.2 Gastrointestinal & Exocrine Pancreatic Disorders: Esophageal, Gastric, Pancreatitis & Malabsorption
Key Takeaways
- Achalasia and Zenker diverticulum are full stomachs regardless of fasting; cricoid pressure is relatively contraindicated in Zenker diverticulum because it can express pouch contents into the pharynx.
- Infantile pyloric stenosis is a medical emergency producing hypochloremic hypokalemic metabolic alkalosis with paradoxical aciduria, and surgery is delayed until chloride exceeds 100 mEq/L and bicarbonate falls below 30 mEq/L.
- Severe acute pancreatitis sequesters 6 to 10 liters into the retroperitoneum and causes hypocalcemia from fatty acid saponification, hyperglycemia, and ARDS in up to one third of cases.
- Nitrous oxide is avoided in bowel obstruction because it diffuses into gas-filled loops faster than nitrogen leaves, and in vitamin B12 deficiency because it inactivates methionine synthase.
- Malabsorption produces vitamin K-dependent coagulopathy that contraindicates neuraxial anesthesia until the INR is corrected.
Why This Topic Matters on the NCE
Domain I.B.9 of the content outline breaks gastrointestinal pathophysiology into six named sub-topics: esophageal disorders, gastric disorders, pancreatic (exocrine) disorders, intestinal disorders, tumors and secreting lesions, and malabsorption disorders. Nearly every one of them changes a decision you make in the first five minutes of an anesthetic — whether the stomach is full, whether cricoid pressure helps or harms, and whether the patient can tolerate an induction dose at all.
1. Esophageal Disorders
Gastroesophageal reflux disease
Reflux reflects a lower esophageal sphincter (LES) barrier pressure (LES pressure minus gastric pressure) that is too low. Barrier pressure falls with volatile agents, propofol, opioids, anticholinergics, and pregnancy, and rises with metoclopramide and succinylcholine. Symptomatic reflux justifies aspiration prophylaxis (nonparticulate antacid, H2 antagonist or proton pump inhibitor, and a prokinetic when not contraindicated) and a rapid sequence induction when severe.
Achalasia
Achalasia is failure of the LES to relax with absent esophageal peristalsis. The esophagus becomes a dilated reservoir that holds undigested food regardless of fasting time.
- Treat every achalasia patient as a full stomach no matter how long they have fasted.
- Head-up rapid sequence induction, large-bore suction ready.
- Cricoid pressure compresses the esophagus against the C6 vertebral body; it does not empty a dilated esophageal reservoir above that level.
Zenker diverticulum
A pharyngoesophageal pouch that fills with retained food and regurgitates it into the pharynx when compressed.
- Cricoid pressure is relatively contraindicated — it can express diverticular contents directly into the pharynx.
- Avoid blind nasogastric tube passage (risk of perforating the pouch).
- Head-up awake or rapid sequence induction with immediate suction.
Esophageal varices
Portal hypertension shunts blood through submucosal veins. These patients bring coagulopathy, thrombocytopenia, hypoalbuminemia, and encephalopathy. Avoid blind instrumentation of the esophagus, including transesophageal echocardiography probes and esophageal temperature probes, when varices are known and bleeding.
2. Gastric Disorders
| Disorder | Pathophysiology | Anesthetic priority |
|---|---|---|
| Gastroparesis | Diabetic autonomic neuropathy, opioids, GLP-1 receptor agonists | Full stomach precautions; gastric ultrasound where available |
| Peptic ulcer disease | H. pylori, NSAIDs | Anemia; avoid further NSAID load; bleeding risk |
| Gastric outlet obstruction | Chronic ulcer scarring, tumor | Hypochloremic, hypokalemic metabolic alkalosis; volume deplete |
| Infantile hypertrophic pyloric stenosis | Hypertrophied pylorus in a 2 to 8 week-old infant | A medical emergency, not a surgical one |
Pyloric stenosis is a recurring NCE item. Persistent vomiting of gastric contents loses hydrogen and chloride, producing a hypochloremic, hypokalemic metabolic alkalosis with paradoxical aciduria (the kidney conserves sodium at the cost of excreting hydrogen ions once chloride and potassium are depleted). Surgery must be delayed until the infant is resuscitated: target a serum chloride above 100 mEq/L, sodium above 130 mEq/L, potassium above 3.0 mEq/L, and bicarbonate below 30 mEq/L. Operating on an alkalotic infant risks postoperative apnea from persistent central alkalosis. The stomach is emptied with an orogastric tube before a rapid sequence or modified rapid sequence induction.
3. Exocrine Pancreatic Disorders
Acute pancreatitis
Autodigestion of the pancreas by prematurely activated proteases. In the United States the dominant causes are gallstones and alcohol.
- Massive third-space sequestration: retroperitoneal and peripancreatic fluid loss can exceed 6 to 10 liters, producing profound hypovolemia and prerenal acute kidney injury. Aggressive crystalloid resuscitation guided by dynamic indices is the mainstay.
- Hypocalcemia from saponification of calcium by liberated free fatty acids — check ionized calcium; it is a marker of severity.
- Hypoxemia and ARDS in up to a third of severe cases, driven by circulating phospholipase A2 and systemic inflammation.
- Hyperglycemia from islet destruction, and hypertriglyceridemia both as cause and consequence.
- Severity scoring (Ranson criteria, APACHE II, BISAP) predicts mortality.
- Ileus, abdominal compartment syndrome, and a genuinely full stomach are the rule.
The classic teaching that morphine causes sphincter of Oddi spasm and must be avoided is worth knowing for the exam, though all mu agonists raise sphincter pressure and the clinical relevance is weak. Glucagon, naloxone, nitroglycerin, and atropine relax the sphincter.
Chronic pancreatitis
Fibrosis producing exocrine insufficiency (steatorrhea, malabsorption of fat-soluble vitamins), endocrine insufficiency (brittle diabetes), severe chronic pain with high opioid tolerance, and often ongoing alcohol use with its own hepatic and withdrawal implications. Celiac plexus block is a recognized analgesic intervention.
4. Intestinal Disorders
- Bowel obstruction is the archetypal full stomach with major third-space loss. Decompress with a gastric tube, resuscitate before induction if time allows, and perform a rapid sequence induction. Nitrous oxide is avoided — it diffuses into gas-filled bowel far faster than nitrogen leaves, distending loops and worsening the surgical field and closure.
- Inflammatory bowel disease (Crohn disease and ulcerative colitis) brings chronic corticosteroid exposure (stress-dose considerations), anemia, hypoalbuminemia with altered protein binding, electrolyte derangement, malnutrition, and biologic therapy such as tumor necrosis factor inhibitors.
- Postoperative ileus is reduced by multimodal opioid-sparing analgesia, thoracic epidural analgesia, goal-directed fluid therapy avoiding overload, and early feeding — the core of enhanced recovery pathways.
- Carcinoid tumors and other secreting lesions are covered in detail in the intra-abdominal and endocrine tumor section.
5. Malabsorption Disorders
Celiac disease, short bowel syndrome, cystic fibrosis, and bariatric surgical anatomy all impair absorption. The anesthetic consequences follow the missing nutrients:
| Deficiency | Consequence |
|---|---|
| Vitamin K | Prolonged prothrombin time and INR - a neuraxial contraindication until corrected |
| Vitamin B12 / folate | Megaloblastic anemia; avoid nitrous oxide, which oxidizes cobalt in B12 and inactivates methionine synthase |
| Iron | Microcytic anemia, reduced oxygen-carrying capacity |
| Vitamin D and calcium | Osteomalacia and fracture risk with positioning |
| Protein | Hypoalbuminemia raises the free fraction of highly protein-bound drugs |
| Magnesium and potassium | Dysrhythmias, potentiation of neuromuscular blockade |
Exam Traps
- Cricoid pressure is not universally protective. It is relatively contraindicated in Zenker diverticulum and useless for the reservoir above the cricoid in achalasia, and it must be released immediately if active vomiting occurs.
- Pyloric stenosis is resuscitated, not rushed. Correcting the hypochloremic hypokalemic alkalosis comes before the pyloromyotomy.
- Avoid nitrous oxide in bowel obstruction, in vitamin B12 deficiency, and in any closed gas space.
A 4-week-old infant presents with a two-week history of projectile non-bilious vomiting. Laboratory values show sodium 128 mEq/L, potassium 2.8 mEq/L, chloride 88 mEq/L, and bicarbonate 38 mEq/L. Urine pH is 5.0. What is the correct next step?
A patient with a known Zenker diverticulum requires emergency appendectomy. Which airway management modification is most appropriate?
A patient with severe gallstone pancreatitis presents for urgent cholecystectomy. Which laboratory abnormality is most specifically explained by saponification of calcium within the necrotic peripancreatic tissue?
Which patient has the strongest indication to avoid nitrous oxide?