Toxicology Flashcards
What are the essential laboratory tests for toxicologic emergencies?
- Glasgow Coma Scale
- Urine
- Blood
- Electrolytes/anion gap
- Osmolality/osmole gap
What is the Glasgow Coma Scale?
Measure person’s level of consciousness after brain injury
Severity and corresponding score:
Mild - 13-15
Moderate - 9-12
Severe - 3-8 (Requires intubation)
How to calculate anion gap?
(Na + K) - (Cl + HCO3)
How to calculate osmole gap?
Measured osmolality - calculated osmolality
Where calculated osmolality =
Na x 2 + glucose + urea + ethanol x 1.2
What are the possible causes of elevated anion gap metabolic acidosis?
MUDPILES
M - Methanol
U - Uremia
D - Diabetic Ketoacidosis
P - Phenformin
I - Iron, Isoniazid, Ibuprofen
L - Lactic acid
E - Ethylene glycol
S - Salicylates
GOLDMARK
G - Glycols
O - Oxaproline
L - L-lactate
D - D-lactate
M - Methanol
A - Aspirin
R - Renal failure
K - Ketones
What are the possible causes of an elevated osmole gap?
MEDIE
M - Methanol
E - Ethylene glycol
D - Diuretics
I - Isopropanol
E - Ethanol
Toxicology testing is most useful when:
Patient doesn’t want to admit ingestion
Results of toxicology testing is used for:
Diagnosis and treatment decisions
What are the NACB guidelines for emergency toxicology?
Tier 1:
Serum quantitative and urine qualitative testing; 24/7 testing
Tier 2:
Additional drug testing; any drugs not included in Tier 1
What drugs are included in Tier 1:
Important drug levels in serum/plasma
- Acetaminophen, Salicylates, Ethanol
Stat qualitative urine toxicology assays required to support ED
- Fentanyl
What is the purpose of patient-centred clinical urine drug testing?
Minimize the risk of unintentional overdose, drug abuse, addiction and diversion
What medications to test for in urine?
Illicit drugs
- Amphetamines, Cannabinoids, Cocaine, Fentanyl, Opioids
Pain meds
- Opioids, benzodiazepines (psychiatric patient)
What are the urine drug testing methods?
Homogenous competitive immunoassay
1. Enzyme multiplied immunoassay technique (EMIT)
2. Cloned Enzyme Donor Immunoassay (CEDIA)
What is the EMIT principle?
If urine is -ve for drug, Ab inhibits G6P dehydrogenase and the substrate, 6-phosphoglucolacton, is not made
If urine is +ve for drug, Ab binds to drug in urine and G6P dehydrogenase will convert G6P into 6-phosphoglucolacton
What is the CEDIA principle?
If urine is -ve for drug, the Ab will bind to the substrate of the enzyme, blocking the substrate from binding to the enzyme.
If urine is +ve for drug, Ab will bind to the drug in the urine. Substrate can bind to enzyme, and chlorophenol-beta-D-galactopyranoside is converted into the product.
What are the analytical issues for EMIT?
False -ve for opioids
What are the analytical issues for POCT testing of opioids?
False -ve for hydrocodone, hydromorphone and oxycodone
How do tests for cocaine work?
Reacts with primary metabolite benzoylecgonine
+ve result = likely person using cocaine i.e highly specific
What are some analytical issues with tests for amphetamine/methamphetamine?
- Highly cross-reactive
- Cross-reacting cmpd hv similar structure w standardizing cmpd - Less specific - more false +ves
What are some analytical issues with tests for opioids?
- Cross-reacting cmpds can be structurally unrelated
- Some quinolone antibiotics can cause false +ves
What are some analytical issues with tests for Diphenydramine and ibuprofen?
Diphenydramine only
False +ve tricyclic antidepressant
Diphenydramine & Ibuprofen
False +ve methadone by some IAs
What is the general performance of IAs with the different types of drugs? (Good, Bad, Ugly)
Good:
Cocaine
Bad:
Amphetamines
Opioids
Benzodiazepine
Fentanyl
Ugly:
Tricyclic antidepressants
What is the performance of IAs with amphetamines?
➔ False -ve: low cross-reactivity towards MDMA (Ecstasy)
➔ False +ve: other medications
What is the performance of IAs with opioids?
➔ False -ve: low cross-reactivity w/ oxycodone & hydromorphan
➔ False +ve: when taking antibiotics (Ofloxacin & Levofloxacin)
