The Tox Cave
The Tox Cave will dissect interesting ED cases from the perspective of a toxicologist, focusing on applying up-to-date management of the poisoned patient.
The name Tox Cave was coined by a former toxicology fellow to describe our small office space, likening it to the Bat Cave. The Tox Cave is where Drexel toxicology fellows and attendings have gathered to discuss the nuances of toxicology over the years.
Monday, August 03, 2015
A 37-year-old woman is brought into the emergency department by EMS after being found down next to a bottle of an unknown substance. (See photo.) Her family said she was initially tearful and repeatedly mumbling, “I’m sorry,” and became progressively less responsive.
She was obtunded and intubated for airway protection upon arrival to the ED. Her initial vital signs were a temperature of 98.8°F, heart rate 110 bpm, blood pressure 187/118 mm Hg, respiratory rate 22 bpm, and pulse oximetry 98% on ventilator. Initial ABG reveals a pH 6.89, pCO2 16, pO2 174, and bicarbonate 3.1. Pertinent lab results include a metabolic panel with an anion gap of 24, creatinine 1.23, ammonia of 103, and a positive urine drug screen for THC.
What is the differential diagnosis for a patient with a large anion gap? For this patient, we considered the possible etiologies included in the mnemonic MUDPILES.
M Methanol, metformin
D DKA, AKA, or any ketoacidosis
P Paracetamol, paraldehyde
I Iron, isoniazid
E Ethylene glycol, ethanol
Acetaminophen, salicylate, and ethanol levels were negative. Initial lactate is 5.6 mmol/L, and serum osmolality is 354. Her metabolic panel is below:
What is this patient’s osmolal gap? Osmolal gap= serum osmolality - calculated osmolality [(2 x serum Na) + (serum glucose/18) + (serum BUN/2.8) + (serum ethanol/4.6)]. In this case: Calculated osmolality = (2x135) + (200/18) + (14/2.8) + (0/4.6) = 286
Osmolal gap = 354 - 286 = 68
What products contain methanol or ethylene glycol?
n De-icing solutions
n Windshield washer fluid
n Engine coolant antifreeze
n Paint removers
n Shoe dyes
n Solid cooking fuel used in camping
n Embalming fluid
n Contaminant in moonshine or fermented beverages
Methanol and ethylene glycol themselves are relatively nontoxic and primarily cause CNS sedation. Toxicity stems from their metabolism to toxic metabolites.
The toxic metabolite of methanol formic acid causes retinal and optic nerve injury, and may lead to permanent blindness. Ischemic or hemorrhagic injury to the basal ganglia have also been described.
The toxic metabolites of ethylene glycol lead to acute renal injury and ultimately to renal failure by tubule damage and by the formation of calcium oxalate crystals, which lead to tubule obstruction. Systemic hypocalcemia may also occur as the oxalic acid metabolite precipitates with calcium.
The parent compounds initially cause an elevation of the osmolal gap after ingestion. As they are metabolized to their toxic acid metabolites, the osmolal gap decreases and the anion gap increases, causing a profound anion gap metabolic acidosis.
Treatment should begin immediately based on history, clinical exam, elevated osmolal gap, or a metabolic of unknown cause. Confirmatory testing done by measuring serum ethylene glycol or methanol levels should not delay treatment because these tests are generally sent to outside laboratories and may take some time to provide results. Consultation with a medical toxicologist or poison control center is recommended because these patients are a potentially serious medical emergency.
Initial treatment of a toxic alcohol ingestion requires the use of an inhibitor of alcohol dehydrogenase. Prior to the discovery of fomepizole in 1963, ethanol had been used to block the metabolism of methanol and ethylene glycol to their toxic metabolites. Alcohol dehydrogenase preferentially metabolizes ethanol, and therefore would not be available to metabolize methanol or ethylene glycol.
In fact, a patient who has ingested ethanol and a toxic alcohol has unknowingly protected himself from metabolizing the toxic alcohol to a toxic metabolite while his ethanol level remains greater than 100 mg/dL. Fomepizole has now replaced ethanol as the antidote of choice for toxic alcohol ingestion in the United States, and it has no contraindications and no known adverse effects. A 15 mg/kg IV loading dose of fomepizole should be administered followed by 10 mg/kg doses every 12 hours if a toxic alcohol ingestion is suspected. Repeated doses of fomepizole induce cytochrome P450 metabolism, so clinical guidelines recommend increasing fomepizole dosing to 15 mg/kg every 12 hours after 48 hours. No dose adjustments are needed for patients with renal or hepatic disease. Treatment should continue until methanol or ethylene glycol levels are less than 20 mg/dL.
Hemodialysis should be considered in those patients with end-organ toxicity or severe acidosis. The severe acidosis indicates that a majority of the toxic alcohol has already been metabolized, in which case the efficacy of fomepizole is minimal. Clinical guidelines also recommend initiating hemodialysis with a methanol level higher than 50 mg/dL because toxic levels of methanol, along with inhibition of metabolism from fomepizole, will lead to a prolonged half-life. It is important to remember that hemodialysis will not only remove the toxic alcohols and their metabolites but will remove the antidote as well, making it necessary to increase fomepizole dosing to 10 mg/kg every four hours during hemodialysis.
A recent challenge to the treatment of toxic alcohol poisoning is the current national shortage of fomepizole. Hospitals have begun to develop or revisit protocols for the therapeutic use of ethanol for toxic alcohol poisoning. This nationwide shortage makes it important to know how to dose and treat with both antidotes.
Dosing may be challenging because of variability in metabolism between patients, so frequent monitoring is required. Most pharmacies have a 10% ethanol solution available. Administration via a central venous catheter is preferred because of the risk of phlebitis, but a large vein may also be considered for administration of IV ethanol.
IV ethanol dosing (initial blood ethanol concentration=0):
n Loading dose:
n 8 mL/kg ethanol 10% intravenous solution
n Give over 20 to 60 min as tolerated.
n Loading dose may be omitted if serum ethanol level is higher than 100.
n If serum ethanol level is detected, decrease loading dose proportionally.
n Maintenance dose (non-drinkers)
n 1 mL/kg/hr ethanol 10% solution
n Maintenance dose (drinkers)
n 2 mL/kg/hr ethanol 10% solution
n Maintenance dose during hemodialysis
n 2 to 3.5 mL/kg/hr ethanol 10% solution
n Obtain serum ethanol levels after the loading dose and frequently during maintenance therapy.
n Target blood ethanol concentration: 100–150 mg/dL
n Monitor every two hours until goal is achieved or after a change in the infusion rate.
n Once stable, monitor every four to six hours.
n Blood glucose
n Every two hours and immediately if any signs/symptoms of hypoglycemia
n Metabolic panel & acid-base status
n Every six hours
n Acute drop in serum bicarbonate or increase in anion gap should prompt immediate evaluation of blood gas and ethanol concentration.
n Observe for adverse effects
n Inebriation or sedation
n Local phlebitis
n Acute flushing, palpitations, postural hypotension in those with atypical aldehyde dehydrogenase enzyme
n Use of interacting drugs that may cause disulfiram-type reactions (metronidazole, furazolidone, procarbazine, chlorpropamide, some cephalosporins, and Coprinus mushrooms)
n Pregnancy category C. Administration should be done in consultation with toxicologist/obstetrician.
Consider adjunctive therapies in treating toxic alcohol patients, such as bicarbonate for significant acidosis in methanol poisoning or ethylene glycol toxicity. Bicarbonate functions by shifting methanol’s toxic metabolite formic acid to the less toxic dissociated form, formate, which has a lower affinity for target sites for toxicity.
The administration of cofactors is thought to have a theoretical advantage for producing nontoxic metabolites, but has not been proven in clinical studies. Folinic acid and folic acid (50 mg IV every four to six hours) enhance the metabolism of methanol’s toxic metabolite formate because it is metabolized to water and carbon dioxide. As cofactors, pyridoxine (50 mg IV every six hours) and thiamine (100 mg IV every six hours) enhance the metabolism of ethylene glycol to nontoxic metabolites, limiting accumulation of the metabolite responsible for renal toxicity and metabolic acidosis.
Our patient was treated with intravenous ethanol (because of the fomepizole shortage), sodium bicarbonate infusion, pyridoxine, thiamine, and folic acid. Nephrology was consulted, and hemodialysis was initiated within six hours of ED presentation. The patient had a prolonged hospital course and returned to baseline by hospital day 8. Although the patient’s initial ethylene glycol level at presentation returned at only 45 mg/dL, the significant metabolic acidosis and acute kidney injury on presentation suggest a significant amount of ethylene glycol had been metabolized by the time she presented.
1. Kearney TE. Chapter 187. Ethanol. In: Olson KR. ed. Poisoning & Drug Overdose, 6th edition. New York, NY: McGraw-Hill; 2012.
2. Brent J. Fomepizole for ethylene glycol and methanol poisoning. New Engl J Med 2009;360(21):2216.
3. Headline: Matt Groening via Homer Simpson, The Simpsons, Episode 171; March 16, 1997.
Wednesday, July 01, 2015
A 22-year-old man with no past medical history presented to the emergency department with altered mental status. He was brought in by police who reported using a TASER on him three times after he became violent with them. His friends report he smoked K2. His initial vital signs included a temperature of 99.9°F, a heart rate of 137 bpm, blood pressure of 151/76 mm Hg, a respiratory rate of 22 bpm, and pulse oximetry of 98% on room air. The patient was agitated and combative, and was placed in four-point restraints.
K2 is a synthetic cannabinoid. Other commonly used synthetic cannabinoids include spice, moon rocks, comatose candy, and black mamba. Typically, the synthetic cannabinoid chemicals are sprayed onto a plant material and sold in packets marketed as incense or aromatherapy. Most come with a warning label of “not for human consumption” to hide its intended use and avoid regulatory control. Synthetic cannabinoids were first reported in 2008. Local and federal agencies have been enacting ordinances and placing many of the identified synthetic cannabinoids into Schedule 1 status to control sale and distribution and manage the potential public health threat. Synthetic cannabinoids, however, may still be available via the Internet and in gas stations and head shops.
The recent resurgence of designer drug abuse with unusual presentations and high degree of severity with intoxication has put this drug at the forefront of the public consciousness again. The New York Times reported the recent rise in New York ED visits from spice: more than 1,000 cases had been reported to regional poison control centers in April, which is more than double the cases reported from January to March 2015. (April 24, 2015; http://nyti.ms/1FIvoaN.) Most of these were not confirmed with testing but rather by self-reports.
NPR likewise wrote about the recent surge in K2 usage throughout the country. (April 27, 2015; http://n.pr/1KtCTn9.) Patients who habitually used K2, called K heads, had been having adverse and severe reactions to this new batch of K2. Hospitals sent samples of these drugs for testing and detected XLR-11, a synthetic cannabinoid known to cause renal damage. Other samples sent have been found to contain synthetic cannabinoids and synthetic cathinones (bath salts). Some samples contained a chemical that had never been seen by the lab before.
Our patients report expectations of a “mellow high,” but instead these patients have been presenting with psychotic or sympathomimetic symptoms. Recent news reports have shown that some of the new K2 makes patients act like they are on PCP. Common findings are nausea, vomiting, abdominal pain, anxiety, agitation, delirium, coma, psychosis, hallucinations, myoclonus, hyperthermia, and tachycardia.
Of concern, recent reports describe symptoms that are not typically expected after the use of synthetic cannabinoids, including CNS depression, bradycardia, hypotension, and seizures.
Testing should be considered for patients presenting after reported or suspected use of a synthetic cannabinoid. Such tests include:
- A thorough evaluation for signs of end-organ injury
- Basic Metabolic Panel: Renal injury has been known to occur with several types of synthetic cannabinoids.
- Renal biopsies have shown acute tubular necrosis and interstitial nephritis.
- CK: Rhabdomyolysis has commonly been reported.
- EKG and cardiac enzymes: Synthetic cannabinoids have been shown to cause myocardial infarction. Coronary artery vasospasm is one proposed mechanism.
- Head CT: Embolic stroke has been described in the literature.
- Synthetic cannabinoids are not detected by the standard urine drug screen. They bind the cannabinoid receptor as does natural marijuana, but these compounds are synthetic and have a different chemical structure.
- Specific blood or urine testing for synthetic cannabinoids or their metabolites are of limited utility in acute managing these patients, but may be considered a confirmatory test when collecting epidemiological data to assist in characterizing epidemics of use.
- Additionally, consider testing for alternative drugs based on similar presentations and recent reports of abuse in the community: bath salts and stimulant designer drugs.
- Do a work-up for additional/alternative diagnoses (i.e., trauma).
Generally, the most common problem with these patients is controlling their agitation. These patients should be aggressively sedated because prolonged agitation and physical restraints can lead to hyperthermia, rhabdomyolysis, and worsening acidosis. One algorithm we propose:
§ *Initial use of benzodiazepines: Ativan 2 mg IV q 2-4 minutes until sedation or a total of 20 mg, or Valium 10 mg IV wait 10 minutes. If not sedated, then increase by 10 mg every 10 minutes for a cumulative total of 100 mg of Valium.
§ If the patient has psychotic symptoms, you may consider 5 mg IV Haldol x 2 or 10 mg IV Geodon or 10 mg IV Zyprexa.
§ If the patient continues to be agitated following either a total of Ativan 20 mg or Valium 100 mg, then you may consider ketamine IV (100 mg for an adult) or 5 mg /kg IM.
§ If the patient continues to be agitated, he should be paralyzed and intubated as the final step for sedation.
* This is only one algorithm we use, and there are many others that may be just as effective. No trials have compared one sedation algorithm with the next. Patients may be affected differently by medications, so always have airway equipment available in case of oversedation.
Once the agitation is controlled, good symptomatic and supportive care should be instituted. There is no specific antidote for synthetic cannabinoid toxicity, and patients should be closely monitored for hyperthermia.
To control agitation, our patient received a total of Ativan 14 mg IV, ketamine 120 mg IV, and then required intubation with rocuronium and was started on a Versed infusion. The patient was admitted to the ICU. His creatine kinase maxed at 16,000. The patient returned to baseline mental status, and was extubated the next day.
Monday, June 01, 2015
The urine drug screen commonly utilized in the emergency department is an immunoassay that uses antibodies to detect specific drugs or their metabolites. This allows for rapid screening for drugs of abuse, but it has many limitations.
Gas chromatography-mass spectrometry (GC-MS) is the confirmatory test, but it is more costly, time-consuming, and generally can only be performed by outside laboratories. This confirmatory test is generally not useful in the emergency department, but has a role in cases of pediatric exposures, research, or occupational drug testing.
One of the limitations of a urine drug screen are the false-positive results from the interference of other drugs with the immunoassay, many of which are from structural similarities. Diphenhydramine and quetiapine commonly cause a false-positive for tricyclic antidepressants (TCA).
TCA, left; diphenhydramine, center; quetiapine, right.
The specificity for phencyclidine (PCP) immunoassays is generally poor and false-positives may result from dextromethorphan, venlafaxine, tramadol, ketamine, and diphenhydramine.
PCP, left; dextromethorphan, center; venlafaxine, right.
The amphetamine/methamphetamine screen has many false-positives, including bupropion (Wellbutrin), dextroamphetamine (Adderall), methylphenidate (Ritalin), promethazine (Phenergan), pseudoephedrine, trazodone, and ranitidine.
Case reports have also documented false-positives for opiates (levofloxacin, poppy seeds), THC (pantoprazole, hemp-containing foods, efavirenz), cocaine (coca leaf tea), and amphetamine (ma huang and ephedrine).
False-negatives may result from drug concentrations below the cutoff limit as well as adulterating, substituting, and diluting urine samples. Specific drugs in a drug class also may not be detected depending on the immunoassay used.
The assay most commonly used in hospitals tests for opiates. The term opioids is a broad term that includes the naturally occurring opiates, semi-synthetic opioids, and synthetic opioids. Specific testing for fentanyl, methadone, buprenorphine, oxycodone, or hydrocodone may be requested depending on your laboratory’s resources.
* Generally detected by the urine drug immunoassay.
Most benzodiazepine immunoassays detect oxazepam and nordiazepam, the metabolites of chlordiazepoxide (Librium), diazepam (Valium), and temazepam (Restoril). A false-negative benzodiazepine test result may occur despite the presence of other benzodiazepines, such as alprazolam (Xanax), lorazepam (Ativan), and versed (Midazolam).
The manufacturer’s package insert of the assay should be referenced if there are any questions about the immunoassay’s detection abilities to avoid incorrect interpretations. The detection time of a drug in urine may vary depending on pharmacokinetics of a drug, cutoff limits, metabolites, and chronicity of use. It is important to emphasize that the detection of a drug in the urine does not necessarily equate to intoxication.
Table 1. Duration of Detection Time of Drugs in Urine
Adapted from Mayo Clinic Proceedings 2008;83:66.
Cocaine metabolite (benzoylecgonine)
Cocaine metabolite: chronic user
Marijuana: single use
Marijuana: 4 times/week
Marijuana: daily use
Marijuana: long-term, heavy smoker
Urine drug screens can be thought of as the good, the bad, and the ugly. Screens that are positive for cocaine, THC, or barbiturates are usually true-positives. Screens that are negative for benzodiazepines or opiates could be false-negatives. Depending on the clinical scenario, urine drug screens positive for TCAs, amphetamines, or PCP are more likely to be a false-positive than a true-positive.
Moeller KE, Kelly CL, Kissack JC. "Urine drug screening: Practical guide for clinicians." Mayo Clinic Proceedings 2008;83:66.
Friday, May 01, 2015
A 40-year-old man presented with hypoglycemia following an intentional overdose with Humalog Mix 75/25 (75% insulin lispro protamine suspension and 25% insulin lispro injection). He reported injecting 900 units into his abdomen one hour prior to ED presentation. He complained of lightheadedness and nausea. His initial vital signs were heart rate 110 bpm, blood pressure 112/70 mm Hg, respiratory rate 14 breaths per minute, and oxygen saturation 99% on room air. His physical exam is remarkable for a visible injection site on the abdomen. Blood glucose is 50, potassium is 3.1, and creatinine is 0.8. The patient reports a prescribed dose of Humalog 75/25 20 units SQ before breakfast and again before dinner. (Table 1.)
The adverse effects of insulin overdose result from hypoglycemia, and include diaphoresis, tachycardia, anxiety, hunger, impaired cognition, agitation, and hypothermia. Severe or protracted cases may result in seizure, coma, permanent neurologic damage, and death. Hypokalemia may also occur because of insulin’s effect on the intracellular shifting of potassium.
These diagnostic tests should be considered in an insulin overdose:
n Blood glucose levels (bedside or laboratory)
n Insulin level and C-peptide
- Insulin is endogenously secreted as proinsulin, which is cleaved to form insulin and C-peptide. A decreased or nonexistent level of C-peptide is an indicator of surreptitious insulin administration.
n Potassium and phosphate levels should be checked.
Patients are at risk for hypoglycemia after an intentional injection of insulin. This patient had injected 45 times his recommended dose subcutaneously. For further perspective on dose, emergency physicians may administer 10 units of insulin intravenously in conjunction with an ampule of D50 to manage hyperkalemia. It is worth noting subcutaneous depot injections are erratically absorbed, making it challenging to predict the duration of toxicity. If appropriate, patients should be encouraged to drink or eat to provide and maintain their glucose levels. PO intake will provide a larger dose of glucose with longer duration of activity than anything we can administer by IV. (Table 2.)
If these patients are unable to eat or not responding to enteral nutrition, a dextrose infusion with D10 should be considered with repeated boluses of D50 as needed. Some of these patients may require concentrated dextrose infusions, such as D25W, to treat hypoglycemia. Once initial control is achieved, glucose concentration should be maintained between 100-150 mg/dl with oral intake and a dextrose infusion if needed.
Patients should be monitored for recurrent hypoglycemia with regular interval glucose measurements and recognition of signs or symptoms of hypoglycemia. Frequent glucose checks may require an admission to the ICU, depending on hospital protocols. Potassium should also be monitored because insulin causes intracellular shifting so it should be cautiously repleted to avoid rebound hyperkalemia. Phosphate concentrations should also be monitored because glucose-loading may cause hypophosphatemia.
This patient received orange juice, and was encouraged to eat. He had recurrent episodes of asymptomatic hypoglycemia in the emergency department, and was started on a D10W infusion at 100 ml/hr. He was admitted to the intensive care unit for hourly bedside glucose tests, and had several episodes of asymptomatic hypoglycemia as late as 14 hours post-exposure. He was weaned off the IV dextrose infusion, and no further hypoglycemic episodes were noted.
Tuesday, March 31, 2015
A 42-year-old man presented with somnolence. His initial vital signs were heart rate 54 bpm, blood pressure 92/68 mm Hg, temperature 37°C, respiratory rate 6, and pulse oximetry 90% on room air. His physical examination was remarkable for depressed level of consciousness, miosis, and bradypnea. His mental status and respiratory rate temporarily improved with the administration of 0.04 mg naloxone. He reports swallowing several “patches” in a suicide attempt.
Popular transdermal patches are listed in the table. Others include diclofenac, buprenorphine, hormone patches (estrogen, contraceptive, testosterone), methylphenidate, and rivastigmine. It is important to consider the potentially significant quantity of drug contained in transdermal patches even after being used.
The patches are designed to deliver small quantities of the drug over a long period of time into the outer layers of skin, and it is absorbed into the deeper layers and then to the bloodstream, which circulates it throughout the body. Several types of transdermal delivery systems are available; fentanyl patches, for example, are available as a reservoir system and matrix system. (Figure 1.)
Reservoir system (left) and Matrix system (right). Derived from Duragesic and Mylan package inserts.
Swallowing, sucking, transmucosal absorption by placement of pieces in mouth, brewing it as a tea to ingest or inject, chewing whole or in pieces, extracting with a needle for injection, eluting with a solvent for injection, pyrolyzing patches for inhalation, rectal insertion, insufflation, transdermal application on abraded skin, applying heat to transdermally applied patch, and dermal application of multiple patches.
Some considerations for transdermal patch exposures include:
n Continued drug delivery from skin depots
□ Blood nicotine levels remain elevated for six to 12 hours after removal of a patch.
□ The apparent half-life of fentanyl delivered by transdermal patches is about 17 hours after removal of a patch from the skin.
n Supratherapeutic levels may result from skin conditions: application of external heat source (hot tubs, heating pad, etc.), abraded skin, multiple patches, or from physical patch damage resulting in uncontrolled drug release.
n Significant amount of drug remains in used patches
□ Studies were conducted on 25 mcg/hour and 100 mcg/hour patches after three days of continuous use, and it was determined that there was 700 to 1220 mcg left in the 25ug/hour patches and 4460 and 8440 mcg in the 100 mcg/hour patches.
Initial management of transdermal patch ingestions includes the identification and standard treatment for the suspected drug. During the primary survey, the patient should be disrobed to allow for a complete survey for any transdermal patches, which should be removed and, subsequently, the skin should be decontaminated with copious amounts of water. GI decontamination with whole bowel irrigation should be strongly considered because these patches contain potentially lethal doses of each drug and their ingestion may lead to altered absorption of the drug.
There are no specific labs outside of the typical toxicology labs that should be ordered to help guide the treatment of these ingestions. It is worth noting that fentanyl is not detected on the standard urine drug screens. Imaging is not typically helpful because standard abdominal radiographs are not reliable in detecting patches. All patients should be admitted and monitored because the onset and duration of symptoms may be unpredictable.
The patient had recurrence of somnolence and bradypnea in the ED. He was started on a naloxone infusion and admitted to the intensive care unit. Whole bowel irrigation was administered. The following morning, the naloxone infusion was discontinued and the patient remained asymptomatic for 12 hours after the naloxone infusion was discontinued. He was medically cleared shortly after.
1. Package inserts for Catapres-TTS (clonidine), Duragesic (fentanyl), Lidoderm (lidocaine 5% patch), NicodermCQ (nicotine), Nitro-Dur (nitroglycerin), and Transderm Scōp (scopolamine).
2. Nelson L, Schwaner R. Transdermal Fentanyl: Pharmacology and Toxicology. J Med Toxicol 2009;5(4):230.
3. Prosser JM, Jones BE, Nelson L. Complications of Oral Exposure to Fentanyl Transdermal Delivery System Patches. J Med Toxicol 2010;6(4):443.
4. Montalto N, Brackett CC, Sobol T. Use of Transdermal Nicotine Systems in a Possible Suicide Attempt. J Am Board Fam Prac 1994;7(5):417.
5. Marquardt KA, Tharratt RS, Musallam NA. Fentanyl Remaining in a Transdermal System following Three Days of Continuous Use. Ann Pharmacother 1995;29(10):969.
Read more about transdermal patches in our archive.