GI & Hepatic Physiology

Meet the patient

A 62-year-old with alcoholic cirrhosis is admitted with a variceal bleed. Sedated for endoscopy with a weight-based dose of midazolam, he fails to wake for two days; by day three his INR has climbed, his arterial ammonia is 180, and he is sinking into grade III encephalopathy.^[11]

Three physiology failures are stacked on this bed. The midazolam dose was an overdose, because Phase I CYP450 oxidation is failing and the first-pass is shunted away; the ammonia is climbing because the urea cycle can no longer run, so nitrogen is crossing the blood-brain barrier into astrocytes and swelling them; and the INR moved first because factor VII, with its six-hour half-life, is the first synthetic protein to disappear.^[10]

Hold those three — lost drug handling, lost ammonia clearance, lost clotting factor — and every hepatic section below falls into place; hold the gut beside it and the same logic explains aspiration, bacterial overgrowth and the gut-origin sepsis that follows shock.^[1]

References25ShowHide

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