Paracetamol poisoning

Acetaminophen poisoning

The minimum dose that causes toxicity :  In single dose – 150mg/kg  or 10gm for adult & 200mg/kg for children

Clinical features

Phase I : 30 minutes – 24 hours after ingestion

The patient may be asymptomatic or may present with anorexia, nausea, vomiting, malaise

Physical examination may reveal pallor & diaphoresis

Phase II : 18 - 72 hours after ingestion

Right upper quadrant abdominal pain , anorexia, nausea, vomiting & decreased urinary output

Physical examination may reveal upper right quadrant tenderness, tachycardia & hypotension

Phase III : 72 – 96 hours after ingestion

Also known as hepatic phase

Characterized by nausea, vomiting, abdominal pain, tender hepatic edge on palpation, jaundice, hypoglycemia, coagulopathy, hepatic encephalopathy & acute renal failure.

Death may occur due to multiorgan failure

Phase IV : 4 days – 3 weeks after ingestion

 Also known as recovery phase

Complete resolution of symptoms & recovery of organs takes place

Investigations

Plasma acetaminophen levels are measured . the values are plotted on the Rumack Matthew nomogram to determine the risk of hepatotoxicity

Liver function tests

Renal fucnction tests

PT & INR

ECG done to rule out congestion of cardioactive susbstances

Arterial blood gas – pH < 7.3 indicates poor outcome

Serum amylase & lipase levels to rule out pancreatic injury

If encephalopathy is present, CT brain is done to look for cerebral edema & arterial serum ammonia levels are obtained

Treatment

 The acute management consists of stabilizing airway, breathing & circulation & administration of the antidote- N-acetyl-Cysteine, if indicated

Indications of N-acetyl-Cysteine

Plasma acetaminophen levels above the lower line in the Rumack Matthew nomogram

Suspected ingestion ˃ 7.5gm in a single dose

Patients presenting late with laboratory evidence of liver injury & h/o acetaminophen ingestion

Patients with unknown time of ingestion with serum concentration ˃10mcg