What is the recommended policy for toxicology sample collection in patients suspected of toxic exposure, considering factors such as age, medical history, and clinical context?

Toxicology Sample Collection Policy

Collect toxicology samples immediately when patients present with altered mental status, physiologic instability, severe intoxication, amnesia, or when drug involvement is suspected—prioritizing collection within the first 24 hours and obtaining both blood and urine specimens in parallel for complementary diagnostic information. 1

Clear Indications for Sample Collection

Toxicology samples must be collected in the following clinical scenarios 1:

• Altered mental status of unclear etiology
• Physiologic instability (hemodynamic compromise, respiratory depression, cardiac arrhythmias)
• Severe intoxication with clinical signs of substance use
• Amnesia or memory gaps suggesting possible drug-facilitated scenarios
• Suspicion raised by patient, family, or witnesses of possible drug involvement

Critical Timing Considerations

The 24-hour window is paramount—many substances have extremely short detection windows that make delayed collection diagnostically useless 1:

• GHB is only detectable in urine for approximately 12 hours 2
• Flunitrazepam is detectable in blood for 24 hours and urine for up to 48 hours 2
• Ketamine is detectable in urine for 24-72 hours 2
• Heavy metals can be detected in blood within 2-12 hours of contact 3

Collect the first urine produced after suspected exposure—this provides the highest diagnostic yield, particularly in drug-facilitated scenarios 1

Specimen Selection Protocol

Always collect both blood and urine in parallel when feasible, as each matrix provides distinct and complementary diagnostic information that cannot be obtained from a single sample type 1, 3:

Blood Collection

• Draw from peripheral sites (subclavian vein preferred over jugular or femoral) 4
• Collect 5 mL from two distinct peripheral sites (left and right femoral veins) if post-mortem 5
• Use appropriate anticoagulant tubes (heparinized tubes for heavy metal analysis) 3
• Blood provides the best correlation with current body burden and level of impairment for heavy metals 3

Urine Collection

• Obtain the first void after suspected exposure 1
• Add preservative (sodium fluoride, 0.5-2% w/v) to prevent degradation 5
• Leave 10-20% headspace in tubes if freezing is anticipated 5

Additional Specimens Based on Clinical Context

• Vitreous humor (separate samples from each eye) for post-mortem cases 5
• Stomach contents (representative portion) if recent ingestion suspected 5
• Liver tissue (10-20 g, right lobe) for post-mortem comprehensive analysis 5
• Hair/nail samples if chronic exposure is suspected (lock of hair the width of a pen, tied at root end) 5

Informed Consent Requirements

Obtain informed consent before collection when the patient has capacity, addressing 1:

• Confidentiality and discoverability of results in legal proceedings
• Value of results for immediate medical care
• Timing limitations affecting result interpretation
• Limitations of toxicology testing capabilities
• Financial responsibility for testing

Contamination Prevention Techniques

Meticulous technique is essential to prevent sample contamination 1:

• Disinfect puncture sites with alcohol-based chlorhexidine or iodine solutions 1
• Switch to aqueous chlorhexidine if toxicological testing requirements preclude alcohol-based solutions (to avoid interference) 4, 1
• Use separate sterile instruments for each sample to avoid cross-contamination 4, 1
• Sample internal organs while in situ, immediately after opening the body (post-mortem) 4
• Collect bowel content samples last during evisceration to prevent contamination 4

Special Testing Considerations and Common Pitfalls

Standard drug screening panels are grossly inadequate for many toxicology scenarios 1, 2:

Substances NOT Included in Standard Panels

• Flunitrazepam (Rohypnol)
• GHB (gamma-hydroxybutyrate)
• Ketamine
• Most over-the-counter antihistamines
• Trazodone
• Most "date rape drugs"
• Calcium-channel blockers
• Beta-adrenergic blockers
• Clonidine
• Albuterol 1, 2, 6

You must specifically request testing for suspected substances that fall outside routine panels, consulting with toxicology laboratories, Poison Control Centers, or forensic laboratories for proper specimen collection and interpretation 1

Age and Population-Specific Considerations

While the core principles apply across all ages, recognize that 1:

• Pediatric patients require the same urgent collection protocols when clinical signs warrant
• Drug-facilitated sexual assault scenarios demand immediate first-void urine collection regardless of patient age
• Occupational exposures may require hair/nail collection for chronic exposure documentation 5

Documentation and Chain of Custody

Document timing of specimen collection meticulously 3:

• Record exact time of collection relative to suspected exposure
• Implement chain-of-custody procedures when specimens may be used in legal proceedings 2
• Provide comprehensive clinical/occupational/circumstantial history with samples 5
• Include copy of any available medical records or post-mortem reports 5

Clinical Context Integration

Toxicology screening should be performed as soon as possible, potentially even before finishing the clinical evaluation, as many substances become undetectable within hours 1. The clinical presentation guides which specialized tests to request beyond standard panels 7.

Voluntary substance use does not negate the need for standard care or affect the legal status of non-consensual events 1.