Category Archives: #FOAMtox

TOXCARD: Hyperthermia in the toxicological setting

Author: Jenna Otter, MD (EM Resident Physician, Temple University Hospital) // Edited by: Cynthia Santos, MD (Senior Medical Toxicology Fellow, Emory University School of Medicine), Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UT Southwestern Medical Center / Parkland Memorial Hospital) and Brit Long, MD (@long_brit) 

toxcard

Case Presentation:

A 32 year-old man presents to the emergency department with altered mental status. The patient is agitated but sleepy-appearing. He appears to be uncomfortable, shifting on the stretcher and unable to lie still. An empty bottle of cough syrup is found in his pocket. His vitals are HR 141, rectal temperature 103.6F, BP 214/110, RR 22, SpO2 98% in room air.

Question:

What is the differential diagnosis for hyperpyrexia with altered mental status? How is hyperthermia secondary to drug ingestion and toxic syndromes treated?

Pearl:

Drug-related hyperthermia is difficult to distinguish but may be differentiated based on components of history and physical exam. Hyperthermia secondary to toxic syndromes and drug ingestion will not respond to antipyretics like ibuprofen or acetaminophen and external cooling measures are key.

  • Fever is defined as a physiologic elevation in the hypothalamic set-point for body temperature induced by inflammatory cytokines in response to a stressor.
  • Hyperthermia in the toxicological setting differs from fever in that it results from an unregulated increase in body temperature either from increased heat production or decreased heat dissipation, usually resulting from increased skeletal muscle metabolism or activity.
  • Toxicological causes of increased heat production include serotonin syndrome, neuroleptic malignant syndrome, malignant hyperthermia, alcohol withdrawal, sedative-hypnotic withdrawal, and ingestions of sympathomimetics, anticholinergics, and ecstasy. Decreased heat dissipation through poor sweat production also occurs in anticholinergic ingestions.
  • Initially, fever and hyperthermia are difficult to distinguish but may be differentiated based on components of history and physical exam.

Hyperthermia Differential Diagnosis2

Toxic Syndrome CNS Other
Serotonin Syndrome Meningitis Sepsis
Neuroleptic Malignant Syndrome ICH Heat Stroke
Malignant Hyperthermia Hypothalamic stroke Pheochromocytoma
Alcohol/Sedative-Hypnotic Withdrawal Encephalitis Thyrotoxicosis
Sympathomimetic Syndrome (e.g. cocaine, amphetamines, PCP, MDMA, cathinones, etc.)

 

Status epilepticus Infection (Tetanus, malaria, etc)
Alcohol/Benzodiazepine Withdrawal
Anticholinergic Syndrome
Salicylate Toxicity

 

Some toxicological causes of hyperthermia and their differentiations:

HYPERTHERM

Table Source: Boyer E and Shannon M. The Serotonin Syndrome. N Engl J Med. 2005; 352:1112-1120. DOI: 10.1056/NEJMra041867.

  • Antipyretics have no role in the management of hyperthermia in the toxicological setting since the fever usually results from muscular hyperactivity, not an alteration in hypothalamic homeostasis.
  • Hyperthermia should be addressed promptly by using external cooling blankets, ice water submersion, evaporative cooling techniques, or cool IV fluids. Benzodiazepines should also be used to reduce excess heat production from muscle hyperactivity.
  • To prevent end-organ damage, the goal should be to reduce rectal temperature to below 40°C within 30 minutes of beginning cooling therapy.
  • In severe cases, internal cooling catheters can be used for more regulated cooling, using thermal regulation devices such as CoolLineR or CoolGardR. If necessary, cold fluids can be given through a NG or OG tube in intubated patients. Also the bladder can be irrigated with cool fluids using a foley catheter.

Main point:

Hyperthermia secondary to drug ingestion differs from infection-related fevers in that it results from an unregulated increase in body temperature, usually from increased skeletal muscle activity. Drug-related hyperthermia is difficult to distinguish but may be differentiated based on components of history and physical exam. Hyperthermia secondary to toxic syndromes and drug ingestion will not respond to antipyretics like ibuprofen or acetaminophen and external cooling measures are key.

References:

  1. Simon H. Hyperthermia. N Engl J Med. 1993; 329:483-487. DOI: 10.1056/NEJM199308123290708.
  2. LoVecchio F. Chapter 210: Heat Emergencies. In: Tintinalli J, ed. Tintinalli’s Emergency Medicine. 8th ed. McGraw Hill; 2016: 1365-1370.
  3. Boyer E and Shannon M. The Serotonin Syndrome. N Engl J Med. 2005; 352:1112-1120. DOI: 10.1056/NEJMra041867.

EM@3AM – Anticholinergic Toxicity

Author: Erica Simon, DO, MHA (@E_M_Simon, EM Chief Resident, SAUSHEC, USAF) and Daniel Sessions, MD (EM Associate Program Director, SAUSHEC, USAF / Medical Toxicologist, South Texas Poison Center) // Edited by: Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UTSW / Parkland Memorial Hospital) and Brit Long, MD (@long_brit, EM Attending Physician, SAUSHEC, USAF)

Welcome to EM@3AM, an emdocs series designed to foster your working knowledge by providing an expedited review of clinical basics. We’ll keep it short, while you keep that EM brain sharp.


A 62 year-old female, escorted by her son, presents to the emergency department for altered mental status. The son reports his mother as being in her usual state of health during a visit the night prior, but per the family maid, was severely confused upon awakening one hour prior to arrival.  A phone call to the patient’s daughter reveals a ROS positive only for a medication change: chlorpromazine prescribed for hiccups.

 Triage VS: BP 172/101, HR 127, RR 28, T103.2°F Oral, SpO2 98% on room air

Accucheck: 137

Upon initial evaluation the patient is oriented only to herself. Her pupils are 5mm bilaterally, she is flushed, her skin is dry, and her capillary refill is > 3 seconds. Her abdominal exam is remarkable for a palpable, distended bladder.

What do you suspect as a diagnosis? What’s the next step in your evaluation and treatment?


Answer: Anticholinergic Toxicity1-5

  • Precipitating Causes: Amantadine, antihistamines, antiparkinsonian medications, antipsychotics, cyclic antidepressants, dicyclomine, atropine, phenothiazines, scopolamine, Jimson weed.1 
  • Presentation: Classically “hot as a hare, dry as a bone, red as a beet, blind as a bat, mad as a hatter, full as a flask, tachy as a pink flamingo.”
  • Evaluation:
    • Focused H&P:1
      • Perform a medication reconciliation
      • VS: obtain rectal temperature, look for tachycardia
      • Neurologic examination: possible altered mental status, mydriasis, visual deficits
      • Additional exam findings: patient commonly flushed with dry skin and a prolonged capillary refill.  Palpate the abdomen in search of a distended bladder.
  • Treatment:1
    • Delirium/Agitation: benzodiazepines
      • Avoid haldoperidol – may worsen symptoms
    • Urinary retention: foley placement
    • Hyperthermia: active cooling with misting/fanning, cooled IV fluids; benzodiazepines for shivering
    • Hypotension: IVF; if intractable, consider norepinephrine
    • EKG demonstrating conduction delays: sodium bicarbonate to overcome impaired sodium conduction
    • Although physostigmine has traditionally been recommended only for patients with life-threatening anticholinergic toxicity (given concern regarding its associated complications, i.e. – severe agitation, seizures, persistent hypertension, and hemodynamic compromise secondary to tachycardia),3 newer data report its relative safety and efficacy in reversing the anticholinergic toxidrome; specifically anticholinergic delirium.4,5 
  •  Pearls:
    • Consider anticholinergic toxicity in the differential diagnosis of an altered patient with residual urine > 200-300 mL.2
    • Exercise caution in the use of physostigmine if there is concern for TCA toxicity, arrhythmias, or QRS/QTc prolongation, as upon administration physostigmine displays a dose dependent AV nodal conduction delay.2
    • In 2013, the American Association of Poison Control Centers reported three deaths secondary to an anticholinergic drug (benztropine).3


References:

  1. Thornton S and Ly B. Over-the Counter Medications. In: Emergency Medicine: Clinical Essentials. Philadelphia, Saunders Elsevier. 2013; 1334-1342.e1.
  2. Stilson M, Kelly K, Suchard J. Physostigmine as an antidote. Cal J Emerg Med. 2001. 2(4): 47-48.
  3. Mowry J, Spyker D, Cantilena L, McMillan N, Ford M. 2013 Annual report of the American Association of Poinson Control Centers’ National Poison Data System (NPDS): 31st annual report. Clin Toxicol. 2014; 52: 1032-1238.
  4. Watkins J, Schwarz E, Arroyo-Plasencia A, Mullins M; Toxicology Investigators Consortium Investigators. The use of physostigmine by toxicologists in anticholinergic toxicity. J Med Toxicol. 2015; 11(2):179-184.
  5. Dawson A and Buckley N. Pharmacological management of anticholinergic delirium – theory, evidence, and practice. Br J Clin Pharmacol. 2016; 81(3): 516-524.

 For Additional Reading:

Physostigmine for Anticholinergic Toxicity:

Physostigmine for Management of Anticholinergic Toxidrome

Toxcards: Alcohol Ketoacidosis

Author: Cynthia Santos, MD (Senior Medical Toxicology Fellow, Emory University School of Medicine) // Edited by: Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UT Southwestern Medical Center / Parkland Memorial Hospital) and Brit Long, MD (@long_brit)

Case Presentation:

A 45 year old male presents intoxicated, smelling of alcohol and appears disheveled with vomit on his clothes. He is sleepy but arousable to noxious stimuli. His serum ethanol level is 143 mg/dL. Na 135, K 3.9, Cl 97, CO2 20, BUN 33, Cr 1.1. Lactate 3.1. pH 7.35, CO2 28, HCO3 15. His urine is negative for ketones. His vitals are HR 103, RR 30, BP 115/65, O2 98% RA.

toxcard

Question:

Could these laboratory results be consistent with alcohol ketoacidosis (AKA)?

Pearl:

The classic laboratory findings in patients with AKA include an elevated anion gap metabolic acidosis and an elevated lactate. Early in AKA patients may be negative for ketones when the nitroprusside test is used because it does not detect beta-hydroxybutyrate. As patients recover, the nitroprusside test will become positive as beta-hydroxybutyrate gets converted to acetone and acetate.

Acid/base status:

  • Patients with AKA typically have elevated anion gap metabolic acidosis. However, vomiting may cause a primary metabolic alkalosis and a compensatory respiratory alkalosis which may result in a normal or even elevated pH.
  • AKA patients, as compared to DKA patients, typically have higher pH, lower K and Cl, and higher HCO3 in their blood tests.

High Redox State (Excess NADH):

  • As ethanol is metabolized by ADH and ALDH to acetaldehyde and acetate, respectively, an increased amount of NADH forms which causes a high redox state and excess of reducing potential (increased NADH:NAD+ ratio).

ethanol pathway

Increased lactate due to pyruvate shunting:

  • Reduced caloric intake, decreased glycogen stores, and thiamine depletion results in amino acids being converted to pyruvate. The excess pyruvate that forms can then be diverted to gluconeogenesis, be converted to acetyl-CoA, which can enter the Kreb’s cycle, or can enter various biosynthetic pathways (e.g. fatty acids, ketones, etc.). Pyruvate can be diverted to these pathways if there is sufficient NAD+.
  • However ethanol causes a high redox state (excess NADH). In the setting of a high redox state ethanol results in increased lactate due to the conversion of pyruvate to lactate and diverts pyruvate from gluconeogenesis.
pyruvate to lactate

Figure source: Shull P, & Rapoport J.

Anion gap primarily due to beta-hydroxybutyrate:

  • The primary anion contributor in patients with AKA and diabetic ketoacidosis (DKA) is beta-hydroxybutyrate with lactate having less of a role.
  • Decreased caloric intake and glycogen stores results in increased fatty acid mobilization and oxidation resulting in increased acetyl-CoA. In normal states (when there is sufficient NAD+) acetyl-CoA can then enter the Kreb’s cycle or be used in fatty acid synthesis. Thiamine also facilitates the entry of acetyl-CoA into the Kreb’s cycle.
  • However, when there is a high redox state (excess NADH) and thiamine deficiency acetyl-CoA gets converted to acetoacetate which then gets converted to beta-hydroxybutyrate.

ketone production

Ketone production:

  • Early the main anion contributor is beta-hydroxybutyrate, which is not detected well by the nitroprusside test (used to detect ketones in serum and urine). The nitroprusside test does not detect beta-hydroxybutyrate, although it is good for detecting acetoacetate and acetone.
  • It is common for early AKA to have a falsely negative ketone test if the nitroprusside test is used because of the test’s inability to detect beta-hydroxybutyrate. If available, specific assays for beta-hydroxybutyrate should be done.
  • As patients recover and receive glucose and thiamine supplementation, ATP is made which reverses the pyruvate-to- lactate and NAD+-to-NADH ratios.  This allows beta-hydroxybutyrate to be converted to acetoacetate and as patients recover the nitroprusside test will actually become more positive due to the increased production of acetoacetate.

ketone body ratio in alcoholic ketoacidosis

Figure Source:  www.derangedphysiology.com

Main Point:

The classic laboratory findings in patients with AKA include an elevated anion gap metabolic acidosis, and elevated lactate that is insufficient to account for the gap. The main anion contributor early in AKA is beta-hydroxybutyrate, but it will not be detected when evaluating for ketones using the nitroprusside test. As patients recover and are given glucose and thiamine supplementation, the lactate will decrease as pyruvate is no longer shunted to lactate and instead enters the Kreb’s cycle and other biosynthetic pathways. The anion gap decreases as beta-hydroxybutyrate gets converted to acetone and acetate. The nitroprusside test then becomes positive for ketones later as patients recover.

Resources:
  1. Yip L. Ethanol, Chapter in Goldfrank’s Toxicological Emergencies. Tenth Edition. Editors: Hoffman R, Howland M, Lewin N, Nelson L, Goldfrank L. McGraw Hill (2015); New York.
  2. Woods W, Perrina D. Alcohol Ketoacidosis, Chapter in Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 7th Edition. Editors: Tintinalli JE, et al. McGraw Hill (2011); New York.
  3. Shull P, & Rapoport J. Life-threatening reversible acidosis caused by alcohol abuse. Nature Reviews Nephrology (2010) 6, 555-559
  4. Diabetic, Alcoholic, and Starvation Ketoacidosis. Chapter 6.17. Available at:  http://www.derangedphysiology.com/main/core-topics-intensive-care/acid-base-disturbances/Chapter%206.1.7/diabetic-alcoholic-and-starvation-ketoacidosis

Toxcards: Sympathomimetic vs. Anticholinergic Toxidromes

Author: Patrick C Ng, MD (Chief Resident, San Antonio Military Medical Center) // Edited by: Cynthia Santos, MD (Senior Medical Toxicology Fellow, Emory University School of Medicine), Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UTSW / Parkland Memorial Hospital) and Brit Long, MD (@long_brit)

screen-shot-2017-01-08-at-11-30-27-pm

Case Presentation

An 18 year old female is brought in by EMS after an unknown suicidal ingestion. She is confused, her pupils are dilated, and she is tachycardic. She has no tremors or rigidity. She has no history of chronic substance abuse or withdrawal.

Question:

How can you distinguish an anticholinergic vs sympathomimetic toxidrome?

Pearl:

There are overlapping signs and symptoms in both toxidromes; historical clues and a physical exam targeting the pupils, skin, GI and GU systems can reveal the toxidrome.

anticholinergic sympathomimetic toxidromes

-Antihistamines, antidepressants, scopolamine, hyoscyamine, atropine, and plants containing anticholinergic alkaloids (Datura, Belladonna) can precipitate an anticholinergic syndrome.1

-Treatment for anticholinergic syndrome is mainly supportive. Benzodiazepines are the mainstay treatment. Physostigmine is given to diagnose and treat anticholinergic delirium. A widely followed recommendation is that Physostigmine should not be given if there are signs of sodium channel blockade on the EKG.2 However newer research is challenging this notion.3

-TCA overdose can present with an anticholinergic toxidrome. Physostigmine is contraindicated in TCA overdose due to the concern for Na channel blockade causing myocardial depression.4

-Amphetamines, synthetic cannabinoids and methylxanthines like caffeine, nicotine, and theophylline can precipitate a sympathomimetic syndrome.5

-Treatment for sympathomimetic syndrome is mainly supportive with IV fluids and benzodiazapines. Beta blockers should be avoided in patients presenting with sympathomimetic syndrome secondary to cocaine use secondary to the possible effect of unopposed alpha-stimulation.

-The differential diagnosis for sympathomimetic syndrome include anticholinergic syndrome, sedative-hypnotic withdrawal, alcohol withdrawal, neuroleptic malignant syndrome, opioid withdrawal, and serotonin syndrome. Medical conditions like hypoglycemia, heat stroke, encephalitis, pheochromocytoma, thyoid storm, and sepsis can also mimic sympathomimetic syndrome.5

toxidromes

Table source: Santos C, Olmedo R. Sedative-Hypnotic Drug Withdrawal Syndrome: Recognition and Treatment. Emergency Medicine Practice Guidelines. Evidence Based Medicine Journal. March 2017;19(7):1-20

Main Point:

The clinical picture of sympathomimetic and anticholinergic can appear similar. Both may have agitation, confusion, delirium, seizures, tachycardia, hypertension, fever, and mydriasis. Distinguishing characteristics for anticholinergic syndrome are dry skin, absent bowel sounds, and urinary retention. Remember the colloquial description for anticholinergic toxicity; “Blind as a bat, mad as a hatter, red as a beet, hot as Hades (or hot as a hare), dry as a bone, the bowel and bladder lose their tone, and the heart runs alone.” Both sympathomimetic and anticholinergic syndrome respond well to benzodiazepines. Physostigmine can be used to treat delirium associated with anticholinergic syndrome after checking the EKG for signs of Na channel blockade.

References                                

  1. Curry S, et al. Chapter 14: Neurotransmitters and Neuromodulators. Chapter in Goldfrank’s Toxicologic Emergencies, 10th edition. New York: McGraw-Hill Education, 2015, p173-201
  2. Burns MJ, Linden CH, Graudins A et al. A comparison of physostigmine and benzodiazepines for the treatment of anticholinergic poisoning. Ann Emerg Med. 2000;35:374-81.
  3. Rasimas JJ, Sachdeva KK, Donovan JW. Revival of an antidote: bedside experience with physostigmine. J Amer Acad Emerg Psychiatr. 2014;12:5–24.
  4. Suchard JR: Assessing physostigmine’s contraindication in cyclic antidepressant ingestions. J Emerg Med. 2003; 25:185-91.
  5. Santos C, Olmedo R. Sedative-Hypnotic Drug Withdrawal Syndrome: Recognition and Treatment. Emergency Medicine Practice Guidelines. Evidence Based Medicine Journal. March 2017;19(7):1-20

EM@3AM – Acute APAP Toxicity

Author: Erica Simon, DO, MHA (@E_M_Simon, EM Chief Resident, SAUSHEC, USAF) // Edited by: Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UTSW / Parkland Memorial Hospital) and Brit Long, MD (@long_brit, EM Attending Physician, SAUSHEC, USAF)

Welcome to EM@3AM, an emdocs series designed to foster your working knowledge by providing an expedited review of clinical basics. We’ll keep it short, while you keep that EM brain sharp.


A 14 year-old male with a history of major depressive disorder presents to the emergency department following a toxic ingestion. The patient reports consumption of approximately 40 extra strength Tylenol caplets (500mg each), two hours prior to arrival. The patient is nauseated and covered in non-bloody gastric contents. Upon initial examination: GCS 15. VS: HR 132, BP 128/84, RR 18, SpO2 98% on room air.

What is the patient’s diagnosis? What’s the next step in your evaluation and treatment?


Answer: Acute Acetaminophen Toxicity1-3

  • Recommended dosing: 3-4g QD; toxic dose: 150mg/kg
  • Presentation varies according to stage of toxicity:
    • Stage 1 (0.5-24 hrs): mild nausea, emesis, weakness
    • Stage 2 (24-72 hrs): hepatotoxicity +/- nephrotoxicity => RUQ abdominal pain
    • Stage 3 (72-96 hrs): hepatotoxicity peaks => nausea, vomiting, jaundice, coagulopathy
    • Stage 4 (4 days -2 wks): recovery or decompensation resulting in death
  • Evaluation:
    • Use the Rumack-Matthew nomogram for single ingestions occurring <24 hours prior to arrival:
      • Obtain AST level at 4 hours s/p ingestion: utilize nomogram to determine the appropriateness of N-acetylcysteine (NAC) treatment
    • If the time of ingestion is unknown:
      • Obtain AST level and a serum acetaminophen level => if AST is elevated or serum acetaminophen concentration >10mcg/mL = initiate NAC2,3
  • Treatment:
    • If patient presents within one hour of toxic ingestion, consider NG lavage if no contraindications.
    • NAC Loading dose: 150 mg/kg IV (max 15g) infused over 1 hr or 140 mg/kg PO
  • Pearls:
    • Rumack-Matthew nomogram should not be employed in the setting of unknown time of ingestion or chronic acetaminophen therapy.
    • NAC is most effective if initiated within 8 hours of acetaminophen ingestion.
    • Evaluate for co-ingestions: serum salicylate, serum ETOH; calculate an anion gap and an osmolar gap as appropriate. Consider UDS.
    • End point of NAC treatment: AST <100 U/L and acetaminophen <10mcg/mL or if extended therapy required: normalization of INR, resolution of encephalopathy, and decreasing AST (<1,000 U/L).3

References:

  1. Tintinalli J, Kelen G, Stapczynski J, Ma O, Cline D, et al. Tintinalli’s Emergency Medicine. 8th ed. New York: McGraw-Hill; 2016. Chapter 190, Acetaminophen.
  2. Heard K. Acetylcysteine for acetaminophen poisoning. N Engl J Med. 2008; 359(3):285-292.
  3. Mottram A, Kumar A. Focus On: Acetaminophen Toxicity and Treatment. American College of Emergency Physicians Clinical and Practice Management. Available from: https://www.acep.org/Clinical—Practice-Management/Focus-On–Acetaminophen-Toxicity-and-Treatment/

TOXCARD: TOXIC ALCOHOL POISONING

Author: Kristin E. Fontes, MD (Emergency Physician, Santa Barbara Cottage Hospital and Goleta Valley Cottage Hospital) // Edited by: Cynthia Santos, MD (Senior Medical Toxicology Fellow, Emory University School of Medicine), Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UTSW / Parkland Memorial Hospital), and Brit Long, MD (@long_brit, EM Attending Physician, San Antonio Military Medical Center)

screen-shot-2017-01-08-at-11-30-27-pm
Case presentation:

A 28-year-old female is brought to the emergency department by ambulance from home after her roommate found her disoriented and poorly responsive. The roommate reports finding a small container of antifreeze in the patient’s bedroom. Vital signs are as follows: T 37.0C, HR 65, BP 126/76, RR 32, and SpO2 98% on room air.  Venous blood gas shows pH 6.97, pCO2 21, pO2 38, HCO3 4.8, and lactate 6.75.

Question:

What are the laboratory abnormalities that can occur with toxic alcohol poisoning and how can it be treated?

Pearl:

Common features of toxic alcohol poisoning are elevated anion gap metabolic acidosis and elevated osmolar gap (the latter being a distinguishing feature from ethanol poisoning); osmolar gap usually elevated early after ingestion.(1,2)

Recall the toxic alcohol metabolites and their effects:

toxic alcohol metabolism

  • EG toxicity can cause significant renal failure due to oxalate crystal deposition in the kidneys and glycolic acid, which is directly nephrotoxic; hypocalcemia and tetany can also result due to oxalate binding to calcium.(1)
  • MeOH toxicity classically causes visual disturbances (“snowfield” vision) due to formic acid-induced optic neuropathy.(1)
  • Isopropanol toxicity causes ketosis without acidosis (no lactic acid formed!).  Usually benign clinical course but can occasionally cause hemorrhagic gastritis. Fomepizole and HD not usually indicated.(1)
  • Propylene glycol toxicity often due to intravenous medication preparations containing this alcohol (e.g., diazepam, lorazepam, esmolol, nitroglycerin, phenobarbital, phenytoin) can result in severe lactic acidosis.(1)
Treatment Approach:
  • Fomepizole competitively inhibits alcohol dehydrogenase, which is involved in the metabolism of all alcohols, including ethanol. It is given to prevent the buildup of toxic metabolites from ethylene glycol (glycolic acid, glyoxylic acid, and oxalic acid) and methanol (formic acid) whose deposition in tissues can cause irreparable damage.(1)
  • Fomepizole is indicated for MeOH or EG ingestion resulting in a metabolic acidosis with an elevated osmolar gap (not accounted for by ethanol) and a serum MeOH or EG level of at least 20 mg/dL.(1)
  • Fomepizole dosing: 1) Load: 15 mg/kg (max 1.5 g) IV, diluted in 100 mL of normal saline or 5% dextrose, infused over 30 minutes; 2) Maintenance: 10 mg/kg IV every 12 hours for 4 doses, then increase to 15 mg/kg until serum toxic alcohol level is less than 20 mg/dL.(1,3)
  • Hemodialysis is indicated for toxic alcohol poisoning with an elevated osmolar gap and/or severe metabolic acidosis refractory to standard therapy, refractory hypotension, or end organ damage (i.e. acute renal failure).(1,3)
  • Vitamin Supplementation: Give folic or folinic acid to patients with MeOH toxicity to divert metabolism away from formic acid to carbon dioxide and water. Give folic acid, pyridoxine, and thiamine to patients with EG toxicity to divert metabolism to nontoxic metabolites.(1,3)
Main points:

Consider toxic alcohol poisoning in a patient with an unexplained elevated anion gap metabolic acidosis and elevated osmolar gap. Consider fomepizole and/or HD in patients with severe toxic alcohol poisoning, especially if refractory to standard therapy.

 

References:
  1. Olson KR & California Poison Control System. (2012). Poisoning & drug overdose. New York: Lange Medical Books/McGraw-Hill.
  2. Emmett M and Palmer BF. Serum osmolal gap. In: UpToDate, Forman JP (Ed), UpToDate, Waltham, MA, 2016.
  3. LeBlanc C, Murphy N. Should I stay or should I go?: toxic alcohol case in the emergency department. Can Fam Physician 2009 Jan;55(1):46-9.

ToxCard: TCA Poisoning

Author: Tharwat El Zahran, MD (Medical Toxicology Fellow, Emory University School of Medicine) // Edited by: Cynthia Santos, MD (Senior Medical Toxicology Fellow, Emory University School of Medicine), Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UTSW / Parkland Memorial Hospital), and Brit Long, MD (@long_brit, EM Attending Physician, San Antonio Military Medical Center) screen-shot-2017-01-08-at-11-30-27-pm
Case Presentation:

2 yo male child presented to the ED with status epilepticus. His parents found an empty bottle of amitriptyline at home. He was intubated, given benzodiazepines and antiepileptic drugs. VS: BP 70/30, T 106 F, RR 24, HR 98, sat 98% RA, glucose 100 mg/dl. EKG is shown below.

EKG TCA PED

Question

What EKG findings occur in tricyclic antidepressant (TCA) poisoning? And how are they treated?

Pearl

TCAs alter the conformation of the sodium channel and slow the rate of rise of the action potential, which produces both negative dromotropic and inotropic effects. Sodium bicarb is the primary treatment for TCA poisoning.

  • All TCA are competitive antagonists of the muscarinic acetylcholine receptors and antagonize peripheral α1 adrenergic receptors.
  • Most prominent effects of TCA overdose result from binding to cardiac Na channels.
  • Acute ingestion 10-20 mg/kg of most TCAs cause cardiovascular and CNS toxicity. In children,  >5mg/kg results in toxicity.(1)
  • Signs of acute cardiovascular toxicity are refractory hypotension, acidosis, and arrhythmias. EKG indicators include intraventricular conduction delay (R shift of QRS axis and prolonged QRS), R in avR≥ 3mm, R/S>0.7 and arrhythmias. A QRS≥100 msec indicates increased incidence of serious toxicity, including coma, intubation, hypotension, seizures, and dysrhythmias. Sinus tachycardia is the most common EKG abnormality. (2)(3)
  • Acute neurological toxicity include AMS, delirium, agitation , seizures, and/or psychotic behavior with hallucinations, lethargy, coma.
Treatment approach
  • If the decision is made to intubate, avoid apnea, consider awake intubation, pretreat w benzos to raise seizure threshold and hyperventilate to promote alkalosis.(4)
  • If the EKG indicates signs of TCA poisoning as mentioned above,  give 1-2 meq/kg of sodium bicarb IV boluses at 3-5 min intervals.(4)
  • Continue bicarb drip until QRS duration <100, vitals stable, Na ~150, pH ~7.55. Watch for hypokalemia and hypocalcemia with bicarb drip.  Consider hypertonic saline (3%) if refractory or if serum pH>7.55.(4)
  • Hypotension unresponsive to sodium bicarb, or fluid boluses should be treated with vasopressors (norepi recommended).(4)
  • Treat dysrhythmias with lidocaine bolus of 1mg/kg IV followed by infusion of 20-50 mcg/kg/min.
  • Benzodiazepines, barbiturates, or propofol are recommended for seizures. Consider continuous EEG monitoring with neuromuscular blockade in refractory cases. Avoid phenytoin.(4)
  • For refractory cardiovascular poisoning consider intralipid or ECMO if available.(4)
Main point

TCAs are sodium channel blockers and primary treatment of TCA poisoning is sodium bicarb. The EKG abnormalities like QRS≥100,  R wave in avR ≥3mm, and R/S> 0.7 can predict significant toxicity.  Sodium bicarb displaces the TCA from the Na binding site by raising the Na+ gradient and increasing the pH.  Prolonged resuscitation might be necessary.

References
  1. Caksen et al. Acute amitriptyline intoxication: an analysis of 44 children. Human & Experimental Toxicology (2006) 25: 107-110
  2. Olgun et al. Clinical, Electrocardiographic, and Laboratory Findings in Children With Amitriptyline Intoxication. Pediatr Emer Care 2009;25: 170-173
  3. Paksu et al. Amitriptyline overdose in emergency department of university hospital: Evaluation of 250 patients. Human and Experimental Toxicology 2014;33:980–990
  4. Goldfrank’s Toxicologic Emergencies, 10th E, Chapter 71: Cyclic Antidepressants, p 972- 982.

 

 

Tox Cards: CO Poisoning

Author: Patrick C. Ng (Chief Resident, San Antonio Military Medical Center) // Edited by: Cynthia Santos, MD (Senior Medical Toxicology Fellow, Emory University School of Medicine), Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UTSW / Parkland Memorial Hospital), and Brit Long, MD (@long_brit, EM Attending Physician, San Antonio Military Medical Center)
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Case Presentation:
It is a cold day in the middle of December. A 56 yo female and her 29 yo daughter who is 8 months pregnant present to your ED with a chief complaint of generalized weakness and headache for 2 days. They mention that they think they both caught the flu due to the cold temperatures despite turning their heater on high and using oil lamps for extra heat in their apartment. Their vital signs are normal.
Question:
What are the most common signs/symptoms of carbon monoxide (CO) poisoning, and what are the general management plans?
Pearl:

CO poisoning presents with nonspecific symptoms that can be mistaken for other diagnosis such as the flu. Initial treatment includes high-flow supplemental O2. Hyperbaric oxygen therapy (HBOT) may or may not be the “standard of care” (controversial).

  • CO poisoning can be an elusive diagnosis, as non-specific symptoms such as headache, dizziness, nausea, fatigue, and chest pain are non-specific and can be consistent with many other disease processes.(1,2)
  • Key historical clues include people from the same household presenting with symptoms of headache and flu-like symptoms that improve throughout the course of the day (i.e. when patients leave their dwellings for work, school, etc.) and history of exposure to CO sources such as heaters and enclosed garages.(1,2)
  • A co-oximetry is a spectrophotometer that uses many different wavelengths to measure oxygenated hemoglobin (oxyHb), deoxygenated hemoglobin (deoxyHb), as well as carboxyhemoglobin (COHb) and methemoglobin (MetHb) concentrations.(3)
  • The use of greater number of wavelengths in a co-oximeter as compared to a standard pulse oximeter allows the co-oximeter to distinguish between other types of hemoglobin,  whereas a standard pulse oximetry can only distinguish between oxyHb and deoxyHb.(3)
  • Blood COHg levels commonly reaches a level of 10 % in smokers and may even exceed 15 %, as compared with 1 to 3 % in nonsmokers.(2)
  • Standard treatment includes  high-flow O2  via NRB mask (or intubation in severe cases) until symptoms resolve and CO levels return to baseline; pregnant patients should continue for at least 24 hours with fetal wellbeing assessment. Patients also require follow up at 1-2 months for neuropsychiatric assessment.(1,2)
  • Normal half life of Hb-CO is 4-6 hrs with room air oxygen, 40- min with high-flow O2, and 15-30 min with HBOT.(2)
  • Although the indications for HBO are controversial, some recommend HBO for any CO-poisoned patient with mental status change or history of syncope, signs of cardiac ischemia or arrhythmia, history of ischemic heart disease and CO level > 20%, symptoms that do not resolve with normobaric O2 therapy after 4-6 hours, or any pregnant patient with CO > 15%. Coma is generally an undisputed indication for hyperbaric-oxygen therapy.(2)
  • The use of HBO has been reported to reduce the risk of neurological/cognitive sequelae thought to be associated with carbon monoxide poisoning.(4,5)
Main Point:
Carbon monoxide poisoning can be a deadly diagnosis associated with significant morbidity and long-term permanent neurological damage. It can present with very non-specific symptoms. Specific historical clues as well as co-oximetry can help the emergency physician quickly make the diagnosis. High-flow O2 therapy is the initial standard therapy with some advocating HBOT for select severe or at risk cases.
References:
1. Piantadosi CA. Diagnosis and treatment of carbon monoxide poisoning. Respir Care Clin N Am. 1999;5:183-202.
2. Ernst A, Zibrak JD. Carbon Monoxide Poisoning. N Engl J Med 1998;339:1603-1608.
3. Hampson NB. Noninvasive pulse CO-oximetry expedites evaluation and management of patients with carbon monoxide poisoning. Am J Emerg Med. 2012 Nov;30(9):2021-4.

4. Tibbles PM, Perrotta PL. Treatment of carbon monoxide poisoning: a critical review of human outcome studies comparing normobaric oxygen with hyperbaric oxygen. Ann Emerg Med. 1994;24:269-276.
5. Weaver LK, Hopkins RO, Chan KJ, et al. Hyperbaric oxygen for acute carbon monoxide poisoning. N Engl J Med 2002;347:1057–1067