Toxicology

1
Toxicology

• National Review Course
• Dr. Marco Sivilotti
• Dr. Ian Ball
• October 17, 2013

2
Acknowledgements

• Dr. Jason Lord, University of Calgary

3
Objectives

1. Clinical examination of the overdosed patient
2. General treatment strategies
3. Common poisonings
4. Toxicological concepts applicable to the ER
5. Examinable / Important Lists

4
History unreliable?

• What was ingested? How much and when?
• What was the patient doing when they became ill?
• Past medical records or d/c summaries
• Talk to family, friends, paramedics
• Search belongings
• All bottles and containers pill count
• Search scene ie/ home or garage
• Track marks, packer and stuffer
• Query pharmacy or provincial datasets

5
Physical Examination

• Vital Signs including temp and glucose
• ABCs (Kussmaul, breath odour, Cspine)
• D mental status, seizures, tone
• E expose, skin findings
• Autonomic nervous system
• TOXIDROME

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Odors in Toxicology

• Almonds CN
• Mint Methyl Salicylate
• Fruity Acetone, ETOH, Isopropyl Alcohol
• Garlic Organophosphates, Arsenic
• Glue Toluene, solvents
• Rotten Eggs Hydrogen Sulfide
• Pears Paraldehyde, Chloral Hydrate

7
Know Your Toxidromes

• Mental Status
• Vital Signs
• Pupils
• Skin
• Secretions
• Motor Activity
• GI/GU

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Toxidromes Cholinergic

• Muscarinic symptoms
• Peripheral DUMBELS (diarrhea/diaphoresis,
  urination, miosis, bradycardia/bronchospasm,
  emesis, lacrimation, salivation) or SLUDGE
• Central seizures, dec LOC
• Nicotinic symptoms
• Fasciculations, weakness, respiratory arrest
• Organophosphates, carbamates, nerve agents

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Anticholinergic AntiMUSCARINIC

• Mad as a hatter, Blind as a bat, Dry as a bone,
  Hot as a hare, Red as a beet
• (Anti-DUMBELS) - hot, flushed and dry skin,
  tachycardia, hypertension, psychosis, mydriasis
• Cyclic antidepressants, atropine, benztropine,
  antihistamines, antiemetics, Jimson weed

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Toxidromes Opioid

• Decreased LOC
• Respiratory depression
• Miosis
• miosis may be absent with meperidine
• microdose/titrated naloxone to reverse
  respiratory depression

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Toxidromes Sedative/Hypnotics

• CNS depression (respiratory depression late, and
  only at very high doses)
• hallmark is spared pupillary reactions and normal
  VS
• Barbiturates, Ethanol, Benzos, GHB

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Toxidromes Sympathomimetics

• Psychosis, diaphoresis, mydriasis, agitated,
  seizure, tremors, HTN (wide pulse pressure),
  tachycardic, tachypneic
• Amphetamines, cocaine

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CocainePharmacokinetics

• Variable onset (Body packers vs stuffers)
• Duration of effect short
• Direct Na channel blocker, interferes with
  neurotransmitter uptake, vasoconstriction
• Sensitizes the myocardium to catecholamines and
  decreases myocardial blood flow
• Increased platelet adhesion
• Combines with EtOH to form cocaethylene (more
  potent, longer acting, inc CV injury)

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CocaineClinical Features

• Sympathomimetic Toxidrome
• CNS excitation, psychosis, bleeds, seizure,
  washed out syndrome
• CV ischemia, AMI, HTN, platelet aggregation,
  dysrhythmias, Ao dissection, sudden death
• Vasospasm
• Thrombus
• Increased O2 demand ischemia
• Dissection
• Cardiomyopathy

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CocaineClinical Features

• Resp Asthma exacerbation, NCPE, PTX, airway
  burns, pneumomediastinum, pulmonary HTN
• MSK Rhabdo and ARF
• Psych cocaine bugs, excoriations, crack dancing
  (choreoathetoid movements)

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Cocaine Treatment

• AC if stuffer or WBI if packer
• Aggressively treat agitation with BENZOS
• Hyperthermia associated with death
• paralyze with nondepolarizing agents and pack in
  ice
• Refractory HTN - Alpha blockade with phentolamine
  1-5 mg Q5min PRN or Nitroprusside infusion
• AVOID Beta blockers (unopposed alpha
  stimulation), neuroleptics (lower seizure
  threshold)

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What Tests Should You Order?

• CBC, full lytes (anion gap)
• If altered mental status capillary glucose, EtOH
• If deliberate self-harm ASA, APAP, pregnancy
  test
• If suspect toxic alcohol volatiles (serum osm if
  cannot)
• If sick ABG or VBG, lactate
• Specific levels Dig, Fe, DPH, VAL, CBZ, Li, theo
• 12-lead ECG

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What Test Should You NOT Order?

• Urine drug screen
• Tests for common drugs of abuse, at threshold
  appropriate to screen employees for recent use
• Fun to guess results, but easier/faster to ask
  the patient
• Results rarely change ED management

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Extra tests to consider

• CXR
• Caustics, Aspiration
• Abdominal XR
• Body packer
• CHIPES Chloral hydrate, Heavy Metals, Iron,
  Phenothiazines, EC tablets, Solvents
• Urinalysis
• FeCl2 (ASA), pH, ketones, myoglobin

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When is it Safe to Discharge My Patient?

• If intentional ingestion for self-harm, 6 hrs of
  observation recommended, provided
• History does not suggest a dangerous substance or
  toxic time bomb
• Asymptomatic
• Routine labs are negative
• Reliable observer at discharge
• Psychiatric issues addressed

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Toxic Time Bombs

• Acetaminophen Methadone
• Anticoagulants MAOIs
• Antimetabolites Hypoglycemics
• Body Packers Sotalol
• Enteric coated products (ASA) SR products
• Heavy metals Thyroids meds
• Iron Toxic alcohols
• Lithium Valproic acid
• Lomotil Tricyclics

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When is it Safe to Discharge My Patient?

• Now, if accidental and assuredly non-toxic
  ingestion
• Product identified with certainty
• Single product involved
• Reliable estimate of maximal possible exposure
• Asymptomatic
• Assuredly unintentional/no self-harm intent
• Reliable patient/parent
• Poison-proofing advice given

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Is the CPS a Useful Resource for the Poisoned
Patient?

• Compendium of Pharmaceuticals and Specialties
• 60 contain dangerous or misleading advice
• Only 21 are adequate to allow clinician to
  manage overdose
• Brubacher J, et al. Salty Broth for Salicylate
  poisoning? CMAJ 165(9). Oct 2002

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Where to Turn for Advice?

• Poisindex (Micromedex)
• Regional Poison Centre
• Local Toxicologist
• Textbooks
• Internet
• UpToDate
• ToxBase
• ToxiNZ

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Whom Should I Decontaminate?

• Step 1 Determine risk of ingestion
• How much? How toxic? Reliable historian?
• Step 2 Decide if substance can be removed
• Time of ingestion? Likelihood of recovery?
• Step 3 Consider risk/benefit
• Any contraindications to procedure?
• Step 4 Determine the most appropriate technique
• Lavage, Charcoal, WBI?

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Decontamination1. Syrup of Ipecac

• Rarely indicated
• no improved mortality/potential for harm
• complicates care, including other GID
• contraindicated when potential for seizures or
  dec LOC, as well as hydrocarbons, caustics
• should be considered obsolete

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Decontamination2. Gastric Lavage

• Life threatening ingestion despite maximal
  supportive care/antidote/elim going forward
• Drug in stomach (cf lt 1 hr since ingestion)
• 10-30 reduction in absorption
• ASA, colchicine, TCA
• 40 Fr Ewald (15-28 in peds) after RSI
• left lateral decubitus position
• 200 cc aliquots warm tap water until clear
• Finish off with AC and remove tube

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Decontamination 3. Activated Charcoal

• Recent, likely toxic ingestion (soft hour)
• Not useful alcohols, metals, hydrocarbons
• C/I caustics, aspiration, ileus, perforation
• 1 g/kg plain or with sorbitol OR
• 101 rule (for every ingested 1g toxin, give 10
  g charcoal)
• e.g. ASA, theophylline (10g ingestions)

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Decontamination 4. Multidose Activated Charcoal

• Severe ingestions that are well adsorbed
• EC or SR drugs, toxins that slow GI motility,
  enterohepatic recirculation, anticonvulsants
• 0.25 to 0.5 g/kg q2-4h PLAIN AC (no sorbitol)
• Probably effective phenobarb, CBZ, quinine,
  theophylline
• Possibly effective digoxin, VAL, sotalol

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Decontamination 5. Whole Bowel Irrigation

• Life-threatening ingestion in which MD-AC or GL
  of limited utility
• Iron, body packers, heavy metals like Pb
• sustained release CCBs
• Isotonic PEG solution
• Not absorbed, no fluid shifts
• 2L/hr via ng until effluent clear (c. 6 hrs)
• 500 ml/hr in children

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Enhanced Elimination1. Urinary Alkalinization

• Promotes ionization of the excreted drug which
  prevents tubular reabsorption
• Useful for ingestions of weak acids
• ASA, phenobarb, chlorpropamide
• Target urine pH gt7
• Often difficult to achieve your target pH
• Replenish Na and K, Foley catheter and hourly pH
• ASA, lytes q2h
• Do not use acetazolamide b/c of concomitant
  metabolic acidosis and inc toxicity
• Not forced diuresis

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HA
HA
HA
HA
A- H
A- H
H A-
H A-
Urine
Blood lower pH
Blood
Urine higher pH
Unionized molecules diffuse across renal tubular
membranes from blood to renal filtrate but
ionized ones cannot cross from one compartment
into the other.
When urine is alkalinized, weak acids like
salicylates will dissociate into ions, become
trapped and excreted in the urine. Unionized
parent molecules then diffuse down their
concentration gradient from blood into the urine.
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Enhanced Elimination2. Hemodialysis

• Small Vd, low protein binding, small size, water
  soluble, low endogenous clearance
• methanol, ethylene glycol, ASA, Li, Theophylline
• Less commonly severe acetaminophen, VAL,
  atenolol, sotalol

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Enhanced Elimination3. Continuous Renal
Replacement

• NOT generally of benefit for removing toxins
• peritoneal dialysis also NOT helpful

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Case

• A 24 year female presents to the emergency
  following a mixed drug ingestion. The paramedics
  find empty containers of acetaminophen, ASA and
  diazepam. The ingestion was witnessed
  approximately 45 min ago. She is now obtunded.
• What form of GI decontamination, if any, should
  be performed?

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One good answer

• Following RSI for airway protection, I will give
  her 50g of activated charcoal with sorbitol after
  the position of the ng tube has been confirmed
  radiographically. The need for subsequent doses
  of charcoal could be predicated upon the serial
  serum salicylate concentrations.

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Thou Shalt Know the Big Ones

• APAP
• ASA
• (Toxic) Alcohols
• CCBs
• Dig
• Cocaine
• Methamphetamine
• Opioids

• OP/nerve agents
• CO
• Cyanide
• Iron in a toddler
• TCAs
• Caustics
• Antidotes
• and maybe a few more

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Acetaminophen AntidoteN-acetylcysteine

• Ideally administer within 8 hrs of ingestion
• Mechanism of action
• GSH precursor
• GSH substitute
• Substrate for sulfation
• Non-specific free radical binder

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Acetaminophen1. Single Ingestion lt 8 Hours

• Toxic dose gt150 mg/kg
• Rumack-Matthew Nomogram at 4 hrs (use the lower
  line of 1000 ?M or 150 ?g/mL)
• Pre-4 hour level helpful?
• If undetectable, excludes APAP overdose

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Acetaminophen2. Single Ingestion Between 8-24
hrs

• Start NAC if likely toxic/symptomatic
• Send serum acetaminophen level, AST, INR
• Continue NAC based on level plotted on nomogram,
  until Stopping Criteria met
• Efficacy of NAC decreases with time if
  administered post 8 hours
• Only rare fatalities if initiated within 24 hours

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Acetaminophen3. Staggered, Unknown or Ingestion
gt 24 hrs

• Empirically start NAC if concerning history and
  symptomatic
• Draw serum acetaminophen, AST and INR
• If any are abnormal (ie detectable APAP, AST gt
  100, OR INR gt 1.5) treat until Stopping
  Criteria met
• If all normal (undetectable APAP, AST lt 100, AND
  INR lt 1.5) D/C NAC
• Some countries use creatinine as well

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Acetaminophen4. Slow Release Formulations

• Draw serum acetaminophen at 4 hrs
• If above toxic threshold on nomogram NAC
• Subtoxic level repeat serum level at 8 hrs, and
  treat if above threshold

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Patient-tailored Acetylcysteine
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Continue NAC until

• Stopping Criteria
• APAP undetectable
• AST or ALT lt 100 IU/L (or have peaked), AND
• INR lt 1.5
• OR transplant/death

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Patient-tailored Acetylcysteine

• Start NAC unless
• below Rumack-Matthew nomogram
• Stopping Criteria are met at the outset

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N-acetylcysteine

• IV protocol used in Canada
• 150 mg/kg over 60 minutes
• 12.5 mg/kg/hr for 4 hours
• 6.25 mg/kg/hr until Stopping Criteria met
• ? double the 6.25 to 12.5 in high risk pt??
• Do not write for finite duration
• APAP, AST, ALT, INR, lytes q12h

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Anaphylactoid reactions to N-AC

• Stop the infusion
• diphenhydramine, fluids, rarely more
• Verify need for N-AC, and resume at slower rate
  if still indicated
• No need to withhold in future

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Case

• A 75 year old alcoholic male fell and broke
  several ribs a few days ago. He has been taking 2
  extra strength Tylenol every few hours for 3
  days. He presents with abdominal pain and nausea.
• How would you manage this patient?

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Case

• Start NAC empirically (?orally), draw
  Acetaminophen level, AST and INR in addition to
  other bloodwork, and treat until normalize
• (if AST abnormal at baseline, treat until returns
  to prior baseline, or peaks and falls by gt50 of
  peak)

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SalicylatesPharmacokinetics

• Rapidly absorbed in therapeutic doses
• NOT after overdose!
• Rapidly eliminated in therapeutic doses
• NOT after overdose! (zero order kinetics)
• No antidote!
• Toxicity rate of absorption gt rate of
  elimination
• Serum level cannot be interpreted in isolation,
  without knowing serum pH!
• Serum levels most helpful in hindsight!

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Salicylates

• Done Nomogram NOT clinically useful
• Modeled after single, acute ingestion of NON- EC
  ASA, in peds!
• Nontoxic levels drawn before 6 hrs not useful
• Patients may become rapidly toxic prior to 6 hr
• Not useful for staggered or chronic ingestions
• Does not correlate with serum pH or clinical
  status
• TREAT THE PATIENT, NOT THE LEVEL!

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SalicylatesToxicity

• Every organ system affected, but
• Brain toxicity kills patient
• Beware methyl salicylate (7.5 g ASA in 5cc) most
  toddler exposures die en route to pediatric
  hemodialysis centre!

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SalicylatesClinical Presentation

• Early N/V, tinnitus, diaphoresis, confusion,
  deafness, tachypnea, vertigo, respiratory
  alkalosis (direct stimulation)
• Late anion gap metabolic acidosis, ? LOC, NCPE,
  hypoglycemia, hepatic and renal dysfunction,
  death

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• Increased tissue and CNS penetration with
  acidosis is a very important concept!
• Fastest way to kill an ASA overdose is to sedate
  for agitation!
• Decreasing serum levels may reflect
• Increased ASA excretion, OR
• Increased tissue penetration and toxicity

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Acute Chronic
Age Younger Older
Etiology Overdose Accidental
Dx Classic Subtle
Comorbidities Few Many
Suicide attempt Often Rarely
Clinical course Rapid Progression Neurologic Predominate (nonspecific)
Serum levels ???? ?
Mortality Uncommon 25
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The Anion Gap

• Sodium (Chloride Bicarb)
• N 7 /- 4 meq/L
• MUDPILES CAT
• Serum lactate (Elevated level does not rule out a
  toxic ingestion)
• Serial measurements are very important
• Venous gas can be substituted for ABG

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SalicylatesTreatment

• Volume resuscitate!
• GL, MDAC and WBI all recommended
• Urinary alkalinization
• Empiric dextrose (low CNS Glc)
• Use pH and mental status to guide Rx

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SalicylatesAlkalinization

• Indications
• Symptoms of salicylism
• Tinnitus
• Metabolic derangements
• Serum level gt 2 mmol/L (or expected to get there!)

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SalicylatesAlkalinization

• Target Urine pH gt7
• Keep serum pH lt 7.55
• Avoid hypokalemia (K/H exchange in distal
  tubule)
• No role for forced diuresis
• q2h testing of lytes and salicylate levels

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SalicylatesHemodialysis

• Indications
• Worsening clinical status
• End organ toxicity AKI, NCPE, CNS
• Severe acid base disturbance
• Volume overload
• Serum level gt 7 mmol/L (acute) or gt 4 mmol/L
  (chronic) or expected to get there despite urine
  alkalinization and GID!

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Tricyclic AntidepressantsPharmacokinetics

• Rapidly absorbed, large Vd, variable protein
  binding, lipophilic
• Mechanism of action
• Inhibits voltage gated Na channels (prolongs
  phase 0 depolarization) and blocks K efflux
• Negative cardiac inotrope
• Blocks H1, H2 and D2 receptors
• Blocks muscarinic receptors
• Alpha blockade
• Inhibits DA, serotonin Norepinephrine reuptake
  interacts with GABA receptors

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Tricyclic Antidepressants Clinical Presentation

• End organ effects
• Cardiovascular
• hypotension, widened QRS and Qt, dysrythmias
• CNS
• abrupt and unpredictable decreased LOC and
  seizure
• Anticholinergic toxicity
• Tachycardia, confused, flushed

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Tricyclic Antidepressants Diagnosis

• Drug levels do NOT correlate with toxicity
• EKG diagnostic of Na channel blockade
• limb QRS gt100 msec 30 risk seizure
• gt160 msec 50 risk arrhythmias
• R axis deviation in terminal 40 msec QRS of aVR
  (tall slurred R wave gt 3mm)
• Sinus tachycardia with prolonged QT interval
• Boehnert Lovejoy, NEJM, 1985

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Tricyclic Antidepressants Treatment

• Consider gastric lavage and AC
• Beware rapid LOC and seizures
• Avoid acidosis at all costs (seizures, ?BP, ?CO2)
• Sodium bicarbonate boluses for wide QRS

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Tricyclic Antidepressants Treatment

• Indications for Alkalinization
• QRS gt100 msec in limb leads
• VT (Second Line Lidocaine, Amiodarone)
• Cardiac arrest in young adult

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Tricyclic Antidepressants Treatment

• Hypertonic Saline (when serum pH gt 7.55)
• Benzos for sedation or seizure, propofol if
  refractory
• Fluids and ?-agonists for hypotension
• Physostigmine can be considered if survive
  cardiac toxicity
• Hoffman, Votey et al., Am J Emerg Med 1993
• Hoegholm Clementsen, J Toxicol Clin
  Toxicol 1991

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DigitalisPharmacokinetics

• Binds to the Na-K ATPase (inhibits active
  transport of Na and K)
• Increased intracellular Ca
• Enhanced automaticity with decreased conduction
  Vagolytic
• ECG Slow A. Fib, Nonparoxsymal junctional
  tachycardia, Atrial tachycardia with block,
  Bidirectional V. Tach

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DigitalisClinical Presentation

• Acute hyperkalemia
• G/I sine qua non N/V, anorexia, abdominal pain
• CNS confusion, dec LOC, headache, seizures
• Visual blurred, scotoma, altered color vision,
  halos

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DigitalisTreatment

• MDAC
• Correct serum electrolytes
• Atropine for bradycardia (may not be effective)
• Avoid 1A, 1C antidysrhythmics
• Avoid Calcium if concomitant AKI
• Digoxin specific FAB fragments (Digibind)

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DigoxinDigibind

• Binds free drug and promotes transport of bound
  digoxin from tissue to serum
• Bound drug excreted renally
• Onset 15 min (complete by 90 min)
• Downside cost.

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DigoxinFAB Indications

• Adults
• Ventricular dysrhythmia
• Progressive/refractory hemodynamic instability or
  bradycardia
• K gt 5 mmol/L (acute)
• Ingested Plant dysrhythmia
• Acute ingestion gt 10 mg (adult) or 4 mg (peds)

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DigoxinFAB Indications

• Pediatrics
• Ingested dose gt 0.1 mg/kg or serum level gt 5
  ng/ml with progressive symptoms or K gt 5
• Coingestion with other CV med or TCA
• Ingested plant other indication

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Digoxin FAB Dosing

• Empiric
• Acute adults and peds 5 vials
• Chronic adults 2-4 vials, peds 1 vial
• Based on steady state Vd (6 hrs)
• (serum dig level x wt in kg) / 100 vials

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Pitfalls of Using the Serum Digoxin Level

• Interpreted with other electrolytes
• Pre-redistribution levels high (within 6 hr of
  ingestion)
• False positives can occur
• Assays vary after FAB treatment may be very high
  if measure total dig
• Other cardiac steroids variably detected

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IronPharmacokinetics

• Prescribed as Ferrous gluconate, sulfate and
  fumarate with differing elemental Fe
  concentrations other forumulations available
• lt 20 mg/kg elemental Fe likely asymptomatic
• gt 20 mg/kg self limiting GI symptoms
• gt 40 mg/kg potentially serious
• gt 60 mg/kg may be lethal ( 5 tabs for a
  toddler)
• Toxicity
• Direct caustic injury to GI mucosa
• Impaired intracellular metabolism liver, CNS
  and CV collapse

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IronClinical Manifestations

• Stage I 0-6 hrs
• Acute corrosive effects on GI tract
• N/V, diarrhea, abd pain and hypovolemia
• If asymptomatic at 6 hours no sig OD
• Stage II 6-12 hrs
• Latent stage with apparent recovery
• Never asymptomatic, just less violently ill

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IronClinical Manifestations

• Stage III 12-48 hrs
• Acidosis, CV collapse, GI bleed, lethargy and
  coma
• Stage IV 2-5 days
• Hepatic failure / death
• Stage V delayed corrosive effects
• GI scarring, strictures and obstruction

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IronDiagnosis

• AXR if suspicious, does not rule out
• Serum Fe level 4 hours post ingestion
• lt55 umol/L Do not treat
• 55-90 umol/L Treat if s/s
• gt90 umol/L Treat all
• Repeat level at 8 hours with SR or EC preps

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IronTreatment

• Fluid resuscitation
• WBI
• No role for AC
• Deferoxamine IV x 24 hrs
• chelates Fe ? renally excreted
• Resp toxicity (ARDS) with prolonged infusion
• Slow infusion if hypotension develops
• Yersinia sepsis

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IronCauses of Metabolic Acidosis

• Conversion of Fe2 to Fe3 ? liberates H
• Vasodilation and ? BP lactic acidosis
• Direct neg inotrope ? Cardiac output
• Disrupts oxidative metabolism

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Toxic Alcohols

• Ethylene Glycol, Methanol, Isopropanol
• Same kinetics as ethanol
• peak serum levels by 1 hour
• rapidly distribute into body water
• small Vd, not protein bound
• easily dialyzable
• Toxic acid metabolites of EG and MeOH

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Ethylene Glycol

• Present in antifreezes and coolants
• Metabolized by alcohol dehydrogenase ?
  glycoaldehyde, glycolic acid and oxalic acid
• Inhibit oxidative phosphorylation and are
  directly toxic to lungs, kidney and CNS
• Calcium oxalate crystals

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Methanol

• Present in window cleaning solutions, solvents,
  some antifreezes
• Metabolized by alcohol dehydrogenase ?
  formaldehyde and formic acid
• Inhibit cellular respiration and directly toxic
  to CNS (including retina)

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Ethylene GlycolClinical Presentation

• Acute Neurologic Stage (30 min 12 hrs)
• Inebriation, seizure, N/V, coma, osmolar gap
• Cardiopulmonary Stage (12-24 hrs)
• HTN, tachycardia, tachypnea, AKI, metabolic
  acidosis /- pulmonary edema or circulatory
  collapse
• Hypocalcemia and dysrhythmias

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Ethylene GlycolClinical Presentation

• Renal Stage (24-72 hrs)
• Crystalluria, hematuria, proteinuria, ATN and
  flank pain
• Delayed Neurologic Stage (6-12 d)
• Cranial nerve palsies, deafness, cognitive and
  motor abnormalities, personality changes

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MethanolClinical Presentation

• Early inebriation, gastritis, altered LOC,
  ataxia
• Late Visual changes snowstorm blindness,
  altered LOC, metabolic acidosis, seizures
• Optic disc hyperemia, papilledema, sluggish pupils

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Toxic AlcoholsDiagnosis and the Gaps

• Forget the Woods lamp and crystals!
• Increased Anion Gap metabolic acidosis
• Increased Osmolar Gap
• Calculated Osmolality Measured Osmolality
• 2 Na Glucose BUN 1.25 Etoh (N -2 /- 6
  mOsm)
• (Ethanol, Ethylene glycol, Methanol, Isopropyl
  alcohol, Mannitol, Glycerol)

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Gap Dynamics
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Toxic AlcoholsTreatment

• Correct acidosis with Bicarb
• Prevents diffusion of toxic metabolites into
  target tissues

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Toxic AlcoholsTreatment

• Inhibit alcohol dehydrogenase
• Suspected ingestion and 2 of
• Osmolar gap gt 10
• pH lt 7.3
• Bicarb lt 20
• Urinary oxalate crystals
• Serum EG gt 3mmol/l or Meoh level gt 6 mmol/L
• Documented ingestion and Osm Gap gt 10
• Etoh Target serum Etoh level gt 20 mmol/L
• Fomepizole (4MP) easier administration,
  predictable, more potent inhibitor of ADH, safer,
  avoids labs, longer half-life, no altered LOC

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Toxic AlcoholsTreatment

• Enhanced metabolite elimination with Hemodialysis
• Serum EG gt 8 mmol/L or Meoh gt 15 mmol/L
• Metabolic acidosis
• Renal impairment
• Electrolyte abnormalities
• Unstable VS
• END ORGAN DYSFUNCTION

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Toxic AlcoholsTreatment

• Adjunctive Treatments
• Folic/Folinic Acid 50 mg IV q6h for methanol
  (very important)
• Thiamine 100 mg IV and Pyridoxine for ethylene
  glycol (not so important)
• Calcium replacement for EG
• Serial monitoring of acidosis and electrolytes

98
Toxic Alcohols Triage Tools

• Fixed and dilated pupils very poor prognostic
  sign following methanol ingestion
• ABG allows you to make immediate decisions
  regarding fomepizole and hemodialysis
• A loading dose of fomepizole buys you 12-24 hours
  of time in non-acidotic patient
• Serial testing without ADH blockade following
  accidental sipif pH remains normal after 6 hours
  can discharge (unless EtOH or fomepizole on
  board)

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Carbon Monoxide

• Most common cause of death by poisoning in the US
  (20 accidental)
• Mild (5-10) - mild headache, mild dyspnea
• Mod (10-30) - headache, weakness, dizzyness,
  dyspnea, irritability, N/V
• Severe (gt30) - coma, seizures, MSOF, death
• Delayed neuropsychiatric sequelae in 10-30 of
  survivors (levels not predictive)
• Pulse oximeter falsely normal

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So why is 50 carboxyhemoglobin fatal?
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Carbon Monoxide

• 1/2 life carboxyhemoglobin on room air 5-6 hrs
• 1/2 life 100 O2 45-90 min
• 1/2 life HBO (3 atm) 15-30 min
• Indications controversial (dec LOC, severe
  symptoms or levels, met acidosis, age gt50 or preg
  - d/w toxicologist)
• Reduced delayed sequelae if dived within 24hrs
  (maybe)
• Juurlink et al., Cochrane Database Sys Rev
  2000
• Weaver et al., NEJM 2002
• Thom et al., Ann Emerg Med 1995
• Kao Nanogas, Med Clin NA, 2005 - Review

103
Bottom line

• There is insufficient evidence to support the
  use of hyperbaric oxygen for treatment of
  patients with carbon monoxide poisoning

104
Toxins and Seizures

• Anticholinergics Methylxanthines
• Antidepressants Opiods
• ASA Propranolol
• Camphor Stimulants
• Carbamazapine TCAs
• Tegretol Withdrawal
• INH

105
Intractable Seizures

• ABCs, glucose, benzos benzos benzos
• Propofol, Phenobarbital, Pyridoxine
• Preeclampsia / hyponatremia (MDMA) / INH
• INH overdose
• Inhibits the formation of an important substrate
  required for GABA
• Pyridoxine replaces this substrate

106
Tox ACLS

• Sodium bicarbonate first line agent for wide
  complex tachycardias (Cocaine, TCA) or tox arrest
• Avoid procainamide
• Direct pressor (norepi) for refractory
  hypotension
• Prolonged resuscitative efforts not always futile
• Extracorporeal circulatory assistance in extremis

107
Single Tablet/Dose Toxins That Kill

• Camphor Theophylline
• Sulfonylureas Methyl salicylate
• Essential oils Quinine
• Chloroquine Phenothiazines
• Ca blockers TCAs
• Beta blockers Lomotil
• Methadone

108
Nifty antidotes

• Octreotide
• Physostigmine
• High dose insulin
• Intralipid
• Hydroxocobalamin

109
Clinical Syndromes from Chemical Exposures
Syndrome Etiology
Cholinergic Organophosphates, nicotine, carbamates
Muscle Rigidity or seizures Strychnine
Oropharyngeal pain and ulcers Paraquat, diquat, caustics, inorganic mercuric salts, mustards
Cellular hypoxia Cyanide, CO, methemoglobin causing agents
Peripheral neuropathies or neurocognitive Organic mercurics, Lead, Arsenic
Severe GI distress Ricin, Arsenic, Colchicine
MMWR 52(39) Oct 3, 2003
110
Hyperthermia, Altered Mental Status and Rigidity

• Malignant hyperthermia
• Serotonin Syndrome
• Neuroleptic Malignant Syndrome
• MAOI overdose

111
Disease Mechanism Clinical Onset Treatment
NMS ? Central DA activity in thalamus Neuroleptic use, Rigid Gradual, days Benzos, hydrate, cool, paralysis ? Bromocriptine or Dantrolene
Serotonin Syx ? Serotonin in CNS Recent SSRI or DA agonist ? DTR, clonus Rapid with recent dose or drug change Benzos, hydrate, cool Cyproheptadine
Malignant Hyperthermia Genetically unstable sarc. Retic. ? massive Ca release Inhalational anesthetic or sux Rigid Immediate Hydrate, cool Dantrolene
MAOI OD Inhibited monoamine oxidase Adrenergic overdrive Variable Hydrate, cool, paralysis