History and exam
Other diagnostic factors
common
nausea and vomiting
risk factors
History of self-harm
A risk factor for intentional paracetamol overdose.
History of frequent or repeated use of medications for pain relief
A therapeutic excess is when excessive doses of paracetamol are taken with intent to treat pain or fever and without self-harm intent.[3]
Glutathione deficiency
Patients at risk include those with:
Malnourishment (e.g., not eating because of dental pain, fasting for more than a day)
Eating disorders (e.g., anorexia, bulimia)
Psychiatric disorders
Chronic illness (e.g., HIV, cystic fibrosis)
Cachexia
Alcohol-use disorder.
Long-term treatment with drugs that induce liver enzymes (cytochrome P450 inducers)
These drugs include:
Carbamazepine
Phenobarbital
Phenytoin
Primidone
Rifampicin
Rifabutin
Efavirenz
Nevirapine
St John’s wort.
Low bodyweight (<50 kg)
uncommon
right subcostal pain
If a patient presenting >8 hours after an acute overdose, or in the setting of a therapeutic excess, has right subcostal pain, start treatment with acetylcysteine without delay as right subcostal pain is a sign of acute liver injury.[3] Discuss the patient urgently with a senior colleague if a patient presenting <8 hours after an acute overdose has right subcostal pain.
General abdominal pain after 12 to 36 hours may also be present after significant paracetamol ingestion.[3]
jaundice
If a patient presenting >8 hours after an acute overdose, or in the setting of a therapeutic excess, has jaundice, start treatment with acetylcysteine without delay as this is a sign of acute liver injury.[3] Discuss the patient urgently with a senior colleague if a patient presenting <8 hours after an acute overdose has jaundice.
Jaundice may be difficult to detect in people with dark skin.
In practice, most easily seen in the sclera and best seen in natural light by pulling down the lower eyelid and asking the patient to look up.
hepatomegaly
Discuss the patient urgently with a senior colleague as this is a sign of acute liver injury.[34]
Ensure you percuss the upper and lower borders of the liver. In practice, sometimes lung pathology such as COPD can push the liver down and give a false impression of hepatomegaly.
altered conscious level
Start treatment with acetylcysteine without delay as this can be a sign of hepatic encephalopathy. See Hepatic encephalopathy.
Involve critical care support if there is grade 3 or 4 encephalopathy, as tracheal intubation to protect the airway may be needed.[28][29] Critical care should also be involved if there is grade 2 encephalopathy, as these patients are at risk of decompensation and require intensive monitoring.[28][29] The most common clinical classification used to describe the severity of hepatic encephalopathy is the West Haven criteria:[35]
Grade 4: coma, with or without response to painful stimuli.
Grade 3: drowsy but rousable, unable to perform mental tasks, disorientation to time and place, marked confusion, amnesia, occasional fits of rage, speech present but incomprehensible.
Grade 2: drowsiness, lethargy, gross deficits in ability to perform mental tasks, obvious personality changes, inappropriate behaviour, intermittent disorientation. Asterixis is obvious.
Grade 1: mild confusion, euphoria, or depression, decreased attention, slowing of ability to perform mental tasks, irritability, disorder of sleep pattern such as inverted sleep cycle. Asterixis can be detected.
Grade 0: subclinical; normal mental status but minimal changes in memory, concentration, intellectual function, coordination.
asterixis
loin pain
Discuss the patient urgently with a senior colleague as loin pain after the first 24 hours may indicate acute kidney injury.[3]
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