12.3 Fulminant Liver Failure, Cirrhosis Decompensation, and Hepatic Dosing (01.S.8–10)

Liver failure reaches this examination because it is a brain disease as much as a hepatic one. In acute liver failure (ALF) the brain has no time to buffer ammonia, astrocytes swell, and herniation is a leading cause of death. In cirrhosis the brain has adapted; the emergencies are infection, bleeding, and kidney failure, not usually acute herniation. Drug dosing sits on top of both. Independent OpenExamPrep teaching here follows fulminant hepatic failure, cirrhosis complications, and hepatic dosing topics in the ABPN Content Specifications. It is not an AASLD document.

Acute liver failure: definition and tempo

ALF is coagulopathy (typically INR ≥1.5) plus any degree of hepatic encephalopathy in a patient without preexisting cirrhosis, with an illness duration <26 weeks. Wilson disease, vertically acquired hepatitis B, and autoimmune hepatitis can blur that “no chronic disease” rule when they present as ALF; the examination still wants you to treat the cerebral-edema risk.

Tempo predicts the neurology:

Acetaminophen is the prototype hyperacute toxin in North America. Measure a level, but do not withhold N-acetylcysteine (NAC) if the history is plausible, the time of ingestion is unknown, or aminotransferases are already rising. The conventional 21-hour intravenous protocol is 150 mg/kg over 1 hour, then 50 mg/kg over 4 hours, then 100 mg/kg over 16 hours (total 300 mg/kg). Many transplant centers continue NAC as an infusion until the INR is clearly falling or the patient is transplanted. Late presentation is not a reason to skip NAC. NAC is also often started empirically in non-acetaminophen ALF while the workup runs; some data show better transplant-free survival in early-grade encephalopathy.

Other treatable causes to start while you wait: intravenous acyclovir if herpes simplex hepatitis is possible (pregnancy, immunocompromise, fever, anicteric ALF), nucleoside analog for hepatitis B, steroids only when autoimmune hepatitis is the working diagnosis after infection is considered, and delivery planning for acute fatty liver of pregnancy / HELLP. Ischemic (“shock”) liver has astronomical aminotransferases that fall quickly once perfusion is restored and is not primarily a transplant disease.

Ammonia, cerebral edema, and grade III/IV encephalopathy

Ammonia is detoxified to glutamine in astrocytes. Glutamine is an osmolyte. In ALF that osmotic load appears in hours, not months, so cytotoxic cerebral edema and intracranial hypertension follow. Arterial ammonia >150 μmol/L identifies patients at high risk for intracranial hypertension; values >200 μmol/L are associated with herniation in classic series. Venous samples on ice are acceptable if an arterial line is not yet in, but trend the same source.

West Haven grade III (somnolent, marked confusion) and grade IV (coma) encephalopathy in ALF are airway and ICP events. Cerebral edema is uncommon in grades I–II, rises to about 25–35% in grade III, and 65–75% or more in grade IV (AASLD ALF guidance). Intubate for airway protection and controlled ventilation. Head of bed 30 degrees, neutral neck, minimize stimulation, treat fever, and keep the head uncongested (the ACS physiology from the prior section applies). Avoid hypotonic fluids (D5W, 0.45% saline): they drop serum sodium and worsen astrocyte swelling. In the highest-risk group (ammonia >150 μmol/L, grade III/IV, renal failure, vasopressors), prophylactic hypernatremia with hypertonic saline to 145–155 mEq/L is the AASLD-supported osmolar strategy. Mannitol 0.5–1 g/kg is first-line rescue for a herniation spike if the serum osmolality allows; do not give mannitol prophylactically to every ALF patient. Continuous renal replacement therapy can lower ammonia when the kidney fails or ammonia stays high.

ICP monitors are used in some transplant centers for high-risk coma; they are not mandatory in every hospital and they bleed more when INR is 4. Noninvasive optic-nerve sheath and transcranial Doppler trends help when a bolt is not placed. Do not flood the patient with fresh frozen plasma to “correct” INR for a number unless there is bleeding or a procedure: INR is a prognostic marker (King’s College-type listing uses coagulopathy, acidosis, renal failure, and high-grade encephalopathy). Extra plasma volume raises ICP.

Refer to a liver transplant center as soon as ALF is recognized, not after the first herniation. Listing criteria are center-specific; your job is airway, sodium, NAC, glucose, infection surveillance, and a telephone call. Hypoglycemia from failed glycogenolysis is common and mimics herniation — check a glucose before you stack osmotherapy.

Worked example: a 28-year-old presents 36 hours after a large acetaminophen ingestion. INR 4.2, grade III encephalopathy, sodium 132 mEq/L on D5W, arterial ammonia 170 μmol/L. Stop the hypotonic infusion, start hypertonic saline toward 145–155 mEq/L, start NAC now, intubate, and transfer to a transplant center. Do not load valproate for possible seizures. Do not wait for the 4-hour acetaminophen nomogram; the ingestion is already late and the liver is failing.

Cirrhosis decompensation: a different brain

Chronic hyperammonemia allows osmotic adaptation. Hepatic encephalopathy (HE) in cirrhosis is a neurotransmitter and inflammation problem more than acute herniation. Treat it as a precipitant hunt plus ammonia-lowering therapy, not as ALF osmotherapy. Precipitants: gastrointestinal bleed, infection (especially spontaneous bacterial peritonitis), constipation, hypokalemia, alkalosis, benzodiazepines, hypoxia, and TIPS. Lactulose (titrate to about 3 soft stools daily) and rifaximin are the usual pair. Do not use benzodiazepines to “calm” HE; they worsen it. Flumazenil is not standard HE therapy.

Spontaneous bacterial peritonitis (SBP)

Any cirrhotic with ascites and unexplained fever, pain, HE, ileus, or AKI needs a diagnostic paracentesis. SBP is an ascitic fluid polymorphonuclear (PMN) count ≥250 cells/µL, with or without a positive culture (usually a single enteric organism). Do not wait for the culture to start antibiotics. Community-acquired SBP is typically a third-generation cephalosporin (cefotaxime or ceftriaxone). Nosocomial SBP needs broader coverage based on local resistance. Albumin 1.5 g/kg on day 1 and 1 g/kg on day 3 reduces renal failure and death in SBP when creatinine, blood urea nitrogen, or bilirubin is high — this is not cosmetic volume. Secondary peritonitis (polymicrobial culture, very high ascitic protein, glucose <50 mg/dL, high LDH) is perforation until proven otherwise; that is a surgical CT, not another dose of ceftriaxone alone.

Hepatorenal syndrome, conceptually

Hepatorenal syndrome–acute kidney injury (HRS-AKI) is kidney failure from splanchnic vasodilation and renal vasoconstriction after volume has been restored and structural kidney disease, shock, and nephrotoxins have been excluded. A typical sequence is albumin 1 g/kg/day for two days as a diagnostic volume challenge, then a vasoconstrictor plus albumin. Terlipressin plus albumin reversed HRS more often than albumin alone in the CONFIRM trial (NEJM 2021) and was FDA-approved in 2022; it increases respiratory failure (about 14% versus 5% in CONFIRM) and is a poor choice in hypoxia, volume overload, or creatinine already >5 mg/dL. In the ICU, norepinephrine plus albumin is the usual alternative. Midodrine plus octreotide is a ward-level stopgap, not the preferred ICU regimen. Transplant remains definitive. Dialysis is a bridge, not a cure of the physiology.

Variceal bleeding in the cirrhotic ICU patient

The bundle from the prior section still applies: restrained transfusion, octreotide (or terlipressin where used for bleeding), antibiotics, and banding. Gastric fundal varices may need glue or TIPS rather than bands. After a large-volume bleed, HE often follows because the gut protein load becomes ammonia; lactulose starts after the airway is safe. Do not attribute every post-bleed coma in a cirrhotic to HE until you have considered aspiration, seizure, and intracranial hemorrhage — especially if the patient was thrombocytopenic and fell.

Hepatic dosing that hits the neuro ICU

The liver clears high-extraction drugs (flow-dependent) and low-extraction drugs (enzyme- and protein-binding-dependent). In ALF and decompensated cirrhosis both flow and CYP activity collapse, albumin falls, and bilirubin occupies binding sites. The three examination favorites are midazolam, valproate versus levetiracetam, and fosphenytoin.

Midazolam is a CYP3A4 substrate with an active metabolite (1-hydroxymidazolam) that accumulates when renal function also fails. Infusion context-sensitive half-time stretches from hours to days in cirrhosis. High-dose midazolam infusions for status epilepticus or for “comfort” produce a patient who cannot be examined, cannot wean, and looks like irreversible coma. Prefer propofol or ketamine for short-term anesthetic-range sedation in status, with the usual propofol-infusion-syndrome limits, and use the lightest possible sedation for ventilation. Bolus midazolam for seizures still has a role in the first minutes of status; the trap is the unmonitored high-dose infusion left on for days.

Valproate is hepatotoxic, causes hyperammonemia even with therapeutic levels (carnitine depletion), and is contraindicated in ALF and in urea-cycle disorders. It is a poor maintenance choice in decompensated cirrhosis. Levetiracetam is renally cleared, not hepatically metabolized, is not protein-bound in a clinically important way, and was equivalent to fosphenytoin and valproate for benzodiazepine-refractory convulsive status in ESETT (load conceptually 60 mg/kg, maximum 4500 mg). In liver failure, levetiracetam is the preferred antiseizure drug among those three. Adjust the maintenance dose for creatinine clearance and for CRRT.

Fosphenytoin / phenytoin is about 90% albumin-bound. In hypoalbuminemia and hyperbilirubinemia, the free fraction rises, so a “therapeutic” total level of 15 µg/mL can be toxic free phenytoin. The Sheiner–Tozer approximation (corrected total ≈ measured / [(0.2 × albumin) + 0.1]) is a crude alert, not a substitute for a free phenytoin level. Hepatic CYP2C9/2C19 failure also slows elimination, so levels climb over days. Do not empirically “give more fosphenytoin because the total level is 8” in a patient with albumin 1.8 g/dL and bilirubin 12 mg/dL — measure free drug, watch for nystagmus and arrhythmia, and consider levetiracetam instead.

Other practical hepatic-dosing notes that appear in stems: lacosamide has mixed renal/hepatic clearance but is still more usable than valproate; phenobarbital accumulates and sedates for days; propofol has extrahepatic clearance but still causes hypotension; dexmedetomidine is hepatically cleared and lingers; nimodipine is CYP3A4-metabolized — in Child–C cirrhosis the hypotensive effect is exaggerated. For analgesia, morphine-6-glucuronide accumulates more from kidney failure than from liver failure; hydromorphone and fentanyl still require titration.

Exam traps: treating cirrhotic HE with 3% saline as if it were hyperacute ALF herniation; giving hypotonic maintenance fluid to grade-IV acetaminophen ALF; holding NAC because the ingestion was “too late”; waiting for ascitic culture to treat a PMN of 400; starting terlipressin in pulmonary edema; loading valproate for seizures in ALF; and raising the fosphenytoin dose because the total level is low while albumin is 1.6 g/dL.