1. Clinical Toxidromes and Bedside Diagnosis

Rapid identification of a toxidrome—a constellation of signs and symptoms characteristic of a specific class of poison—is the cornerstone of initial management. This allows for empiric therapy while definitive laboratory results are pending.

Key Toxidrome Features

The five classic toxidromes are distinguished by their effects on vital signs, mental status, pupils, and secretions. The table below provides a rapid comparison for bedside differentiation.

2. Laboratory Diagnostics in Poisoning

Laboratory and imaging data are essential to confirm exposures, quantify the severity of poisoning, identify co-ingestions, and guide targeted therapies like antidotes or extracorporeal removal.

Key Metabolic Markers

Serum Toxin Levels & Specialized Tests

• Quantitative Levels: Specific levels are crucial for agents with nomogram-based treatments (acetaminophen) or where levels correlate with severity and guide therapy (salicylates, digoxin, lithium).
• Co-oximetry: A specialized blood gas analysis that directly measures carboxyhemoglobin and methemoglobin levels, which is essential for diagnosing carbon monoxide poisoning and methemoglobinemia, respectively. Standard pulse oximetry is unreliable in these conditions.
• Toxicology Screens: Rapid urine immunoassays are often used for initial screening but have significant limitations, including false positives and false negatives. They should not be used to rule out exposure, and confirmatory testing (e.g., GC-MS) is often required.

3. Severity Scoring and Risk Stratification

Standardized scoring systems help to objectively assess the severity of poisoning, facilitate clear communication, guide the appropriate level of care, and track the patient’s clinical trajectory.

Poisoning Severity Score (PSS)

The PSS is a simple, widely used tool to grade the overall severity of a poisoning case.

• 0 None: No symptoms or signs related to poisoning.
• 1 Mild: Mild, transient, and spontaneously resolving symptoms.
• 2 Moderate: Pronounced or prolonged symptoms requiring medical intervention.
• 3 Severe: Severe or life-threatening symptoms.
• 4 Fatal: Death resulting from poisoning.

Glasgow Coma Scale (GCS) and ICU Scores

• Glasgow Coma Scale (GCS): A fundamental tool for assessing level of consciousness. A score of GCS ≤ 8 is a critical threshold often indicating the need for definitive airway protection (intubation).
• General ICU Scores (APACHE II, SAPS II): While these scores can estimate overall mortality risk in critically ill patients, they are not specifically validated for poisoned patients and may not accurately reflect risks associated with specific toxins.

4. Clinical Decision Algorithms

Effective management of the poisoned patient requires a systematic approach that integrates bedside findings, laboratory data, and risk scores into a cohesive management plan.

Linking Scores to Triage and Care Levels

• Low Risk (e.g., PSS 0-1, GCS 15, asymptomatic): Can often be managed with observation on a medical floor. Requires serial exams to ensure no delayed toxicity.
• Moderate Risk (e.g., PSS 2, GCS 9-14, mild symptoms): Warrants admission to an intermediate care or step-down unit with continuous cardiac and pulse oximetry monitoring.
• High Risk (e.g., PSS ≥3, GCS ≤8, critical lab values, hemodynamic instability): Requires immediate ICU admission for invasive monitoring, potential airway protection, and administration of antidotes or consideration for extracorporeal toxin removal.