What is the recommended approach to monitor and manage paracetamol (acetaminophen) poisoning in the Intensive Care Unit (ICU)?

Monitoring Paracetamol Poisoning in the ICU

In the ICU setting, paracetamol poisoning requires systematic monitoring of hepatic function, coagulation status, encephalopathy grade, metabolic parameters, and multi-organ function, with blood glucose checks at least every 2 hours and frequent assessment of mental status to guide prognosis and treatment decisions. 1

Initial Diagnostic Assessment

Upon ICU admission, obtain the following baseline investigations to assess severity and guide management:

Essential Laboratory Monitoring

• Serum paracetamol level - even if treatment has already begun, this helps confirm diagnosis and assess severity 1
• Coagulation parameters: PT/INR and Factor V levels - PT ratio <50% defines severe acute liver failure 1
• Liver transaminases (AST/ALT) - levels >1,000 U/L indicate significant hepatotoxicity 2
• Arterial blood gas and lactate - arterial pH <7.3 after adequate volume resuscitation is a poor prognostic indicator and transplant criterion 3
• Arterial ammonia levels - levels >200 μg/dL strongly associated with cerebral herniation 4
• Blood glucose - must be monitored at least every 2 hours due to risk of hypoglycemia from hepatic dysfunction 1, 3
• Serum creatinine - creatinine >3.4 mg/dL combined with PT >100 seconds in grade III/IV coma warrants transplant consideration 3

Imaging Studies

• Hepatic Doppler ultrasound - to exclude chronic liver disease, verify vessel permeability (hepatic veins, portal vein), and assess for ascites or hepatomegaly 1
• Echocardiography - particularly when ischemic hepatocellular injury suspected or when AST exceeds ALT 1
• Head CT scan - to exclude intracranial hemorrhage or other causes of altered mental status 4

Continuous Monitoring Parameters

Neurological Monitoring

• Encephalopathy grade assessment - frequent mental status checks using West Haven criteria are more valuable than ammonia measurements for monitoring disease progression 1, 4
• Serum sodium - maintain between 140-145 mmol/L to prevent cerebral edema 1, 3
• Transcranial Doppler ultrasound - for patients with advanced encephalopathy to assess intracranial pressure 1
• Glasgow Coma Scale - tracheal intubation and sedation indicated when GCS <8 1

Critical pitfall: Avoid benzodiazepines and psychotropic drugs like metoclopramide as they worsen encephalopathy and have delayed clearance in liver failure 1, 4. If sedation is necessary for intubated patients, propofol is preferred 4.

Cardiovascular Monitoring

• Volume status assessment - evaluate cardiac output and both right and left-sided cardiac function 1, 3
• Blood pressure - use norepinephrine for refractory hypotension to maintain perfusion 1, 3
• Fluid balance - crystalloid fluids are first choice for expansion 1, 3

Renal Function Monitoring

• Urine output and creatinine trends - acute renal failure commonly develops and may require renal replacement therapy 1, 3
• Avoid nephrotoxic drugs including NSAIDs 1, 3

Coagulation Monitoring

Do not routinely correct coagulation abnormalities - restrict clotting factor administration to cases with active bleeding only 1, 3. Routine correction can obscure prognostic indicators and is unnecessary.

Infection Surveillance

• Monitor for signs of SIRS - administer empirical broad-spectrum antibiotics if worsening hepatic encephalopathy or systemic inflammatory response develops 1, 3

Treatment-Specific Monitoring

N-Acetylcysteine Administration

• Start N-acetylcysteine immediately without waiting for serum paracetamol results in suspected cases (GRADE 1+ recommendation) 1
• Monitor for hypersensitivity reactions during infusion - including hypotension, wheezing, shortness of breath, bronchospasm, rash, urticaria, and pruritus 5
• Adjust dosing for massive overdoses - paracetamol concentrations more than double the nomogram line require increased acetylcysteine doses 6

Prognostic Assessment for Transplant Consideration

Monitor for poor prognostic indicators requiring early transplant unit contact 1, 3:

For paracetamol-induced ALF:

• Arterial pH <7.3 after adequate volume resuscitation, OR
• PT >100 seconds with serum creatinine >3.4 mg/dL in patients with grade III/IV coma 3

For any ALF etiology:

• PT >100 seconds irrespective of coma grade 3
• Higher grades of encephalopathy (III-IV) 3

Monitoring Frequency

• Blood glucose: Every 2 hours minimum 1, 3
• Mental status: Frequent checks, more valuable than repeated ammonia levels 4
• Coagulation parameters: Daily or more frequently if deteriorating 1
• Liver transaminases and creatinine: Daily 1
• Arterial blood gas and lactate: As clinically indicated, particularly if deterioration 1

Key principle: Early recognition of deterioration through systematic monitoring allows timely escalation to transplant evaluation, which significantly improves survival outcomes in severe paracetamol-induced liver failure 1, 3.