What investigations should be done in a patient with suspected hypochlorite (bleach) poisoning?

Investigations in Hypochlorite (Bleach) Poisoning

Obtain comprehensive laboratory testing including complete blood count, electrolytes (sodium, potassium, chloride, magnesium, calcium), renal function (urea, creatinine), liver enzymes (ALT, AST, bilirubin), arterial blood gas with pH and lactate, and β-HCG in women of childbearing age, followed by contrast-enhanced CT imaging of the neck, chest, and abdomen 3-6 hours post-ingestion to assess for transmural necrosis. 1

Initial Laboratory Evaluation

Core biochemical investigations should be performed immediately upon presentation:

• Complete blood count (CBC) to detect leukocytosis (predictive of transmural necrosis) and thrombocytopenia (associated with poor outcomes) 1
• Comprehensive metabolic panel including sodium, potassium, chloride, magnesium, and calcium, as hypochlorite can cause severe hypernatremia, hyperchloremia, hyponatremia, and hypokalemia 1, 2
• Renal function tests (urea, creatinine) since renal failure predicts transmural necrosis and poor outcomes 1
• Liver function tests (bilirubin, ALT, AST) as deranged values are predictive of transmural necrosis 1
• Arterial blood gas with pH and serum lactate to identify severe metabolic acidosis (low pH, high lactate), which correlates with transmural necrosis and mortality 1, 2
• C-reactive protein (CRP) as elevated levels predict transmural necrosis 1
• β-HCG in young women to rule out pregnancy 1
• Blood alcohol level if intentional ingestion is suspected, as coingestion occurs in 66% of intentional poisoning cases 1

Critical Laboratory Findings Requiring Urgent Intervention

Serial monitoring of laboratory values is essential, as initial normal values do not rule out transmural necrosis: 1

• Severe acidosis with pH <7.20 or lactate ≥10 mmol/L indicates high mortality risk 1
• Hypernatremia (>169 mEq/L) and hyperchloremia (>143 mEq/L) can occur with massive ingestion and indicate severe systemic toxicity 2
• Leukocytosis, elevated CRP, renal failure, and thrombocytopenia predict transmural necrosis requiring emergency surgery 1

Imaging Studies

Plain radiography should be obtained first, followed by contrast-enhanced CT:

• Neck, chest, and abdominal radiographs to detect free air indicating gastrointestinal perforation, pneumothorax, or pneumoperitoneum 1, 3, 2
• Contrast-enhanced CT of neck, thorax, and abdomen performed 3-6 hours post-ingestion using intravenous nonionic contrast (2-3 mL/kg at 2-3 mL/s) with 18-25 second acquisition time and 90-second scan delay 1

CT imaging outperforms endoscopy in detecting transmural injuries and predicting outcomes: 1

• The critical finding is absence of post-contrast wall enhancement, indicating transmural digestive necrosis—an absolute indication for emergency surgery 1
• CT can identify air bubbles, abnormal soft tissue density around the esophagus, pleural effusion, mediastinitis, and perforation 3
• A four-stage CT classification system grades esophageal injury severity from Grade I (homogenous enhancement) to Grade IIb (fine rim of external enhancement with non-enhancing necrotic mucosa) 1

Endoscopic Evaluation

Urgent esophagogastroduodenoscopy should be performed within 12-24 hours of ingestion: 4, 5

• Clinical symptoms and oral lesions do not correlate reliably with gastrointestinal damage extent—absence of pain or oral lesions does not rule out life-threatening injury 1
• Endoscopy assesses injury severity and guides management, though it should not be advanced beyond Grade 3 injuries to avoid perforation 4
• Average time to endoscopy in clinical practice is approximately 244 minutes after emergency department admission 5

Poison Control Center Consultation

Contact the Poison Control Center immediately to evaluate systemic toxicity of the specific hypochlorite product: 1, 4

• Identify the concentration of sodium hypochlorite (household bleach is typically 5.25%, but concentrations vary) 2, 6
• Determine the quantity ingested and whether ingestion was accidental or intentional 1
• Obtain guidance on agent-specific management, as certain formulations may require specialized treatment 4

Common Pitfalls to Avoid

Do not rely on clinical presentation alone: While household bleach (oxidants) usually causes mild injuries, severe damage requiring emergency resection has been reported, and massive ingestion can cause extensive necrosis 1, 3, 2

Do not delay imaging for endoscopy: CT imaging should be performed 3-6 hours post-ingestion and provides superior detection of transmural injury compared to endoscopy 1

Do not assume safety based on initial laboratory values: Serial monitoring is crucial as transmural necrosis can develop despite initially normal values 1

Recognize that hypochlorite can cause fatal outcomes: Although most household bleach ingestions follow a benign course, fatal cases with esophageal perforation, mediastinitis, severe metabolic acidosis, and multi-organ failure have been documented 3, 2, 6