Toxicology pgy 1+2 2013
Transcript of Toxicology pgy 1+2 2013
Dr Chris CresswellFACEM
Whanganui New Zealand
The Bible
TOXINZ.com
General approachResuscitate if neededRisk assessment – is what they have taken dangerous?Supportive Care and Monitoring
depending on your risk assessment Investigations
Everyone: Paracetamol level ECG
Other as indicatedDecontamination – very rareAntidotesEnhanced elimination - rareSeek and treat complicationsDisposition – usually psych. Psych does the psych risk
assessment for us.
Toxinology
Critters rather than drugs/chemicals
We have one rare annoying, non-life threatening spider in NZ.
Katipo = red back – painful bite and sweating +/- back pain -> analgesia + antivenom.
Controversial whether antivenom actually works.
Toxicology
Drugs and chemicals
Not going to cover them all!
Toxidrome
What’s a toxidrome?What are some examples?
Toxidrome
Clinical toxicological syndromeie you can examine a patient +/- look at their
ECG or other bedside tests and get a good idea of what they have taken
EgOpioidAnticholinergicCholinergic syndromeSerotonin syndromeNa channel blockade
ToxidromesOpioid: resp depression, decr LOC, miosisAnticholinergic: hot as a hare, mad as a hatter, red as
a beet, dry as a bone eg daturaCholinergic syndrome eg organophosphate, nerve gas
SLUDGEM: salivation, lacrimation, urinarination, diarrhoea, GI upset, emesis, miosis + muscle spasm
Or DUMBELLS: diarrhoea, urination, miosis/muscle weakness, bronchorrhoea/bradycardia, emesis, lacrimation, salivation/sweating
Serotonin syndrome eg SSRI: sweating, agitation, increase muscle tone, fever
Na channel blockade eg tricyclic: hypotension, decr LOC, widened QRS
Rapidly alternating apnoea and coma eg GHB
Tox examHRRRPupil size and reactivity and look for nystagmusArmpits for sweatReflexes and test for clonusTemp
ECGBSL
Labs: almost everyone gets a paracetamol level Cheap test. Treatment very efficacious.
Some specific drugs / chemicals
Common or important ones.
Paracetamol/acetominphenNB different units from UKCommonAlmost always reversible with antidoteHigh survival even from liver failureHow to you risk stratify and treat these
ingestions?What is the antidote?
Paracetamol/Acetominophen Most common scenario: single ingestion, reasonable idea of time. < 10g or 200mg/kg ingested within 8 hours does not need
investigation Otherwise or unknown:
< 2 hours post ingestion of non-liquid and cooperative patient -> single dose activated charcoal.
< 4 hours post ingestion: wait and take blood for paracetamol level at 4 hours post ingestion. N-acetylcysteine (NAC) if over 1000µmol/L.
4-8 hours. Take level. NAC if over threshold on nomogram. 8-24 hours. Take level and start NAC. Stop treatment if under
treatment threshold. 24+ hours or unknown. Take level, VBG, LFT, glucose, INR,
renal function. Start NAC. Stop NAC if ALT normal. If liver failure d/w liver unit
Paracetamol
Multiple dosesLook it up
NACN-acetylcysteineVery safe and effectiveBoxes in ED with dose schedule written on them
3 different rates over 24 hoursFairly frequent anaphylactoid reaction
Eg erythema, urticaria, pruritis, hypotensionThought to be from histamine release rather than
true anaphylaxisIf mild reaction half rate +/- give IV antihistamineIf severe reaction. Stop infusion. Give IV
antihistamine +/- bronchodilators, fluids etc. Once asymptomatic for 1 hour restart infusion at ¼ rate and titrate up
DispositionIn this hospital all patients requiring NAC get
admitted to ward under medical team. Inform psych of admission. They say they
will see patient before “medically cleared”
SSRIsWhat do you need to know about these?
SSRIsUsually no significant toxicityMain risk is serotonin syndrome
What is serotonin sydrome?
Serotonin SyndromeRareExcess serotonin usually from over dose of SSRI
or combination of serotonergic agentsEg
SSRI, St John’s wortAntipsychoticsLithiumPethidineTramadolLSDEcstacy and other amphetamines
Serotonin SyndromeSerotonergic drug +Mild: Tremor, anxiety, nauseaModerate: agitation and hyperreflexia and
clonusSevere: severe: fever, seizures, respiratory
failure, rhabdomyolysis, renal failure, DIC
Serotonin syndromeManagement
Mild: observe for 4-6 hoursModerate: IV fluids, benzodiazepine, +/-
cyproheptadineSevere: cooling, IV benzodiazepine, IV fluid.
May need RSI
So for all overdoses of serotonergic agent need ...Record
TemperatureTone Reflexes Clonus
CCB and Beta Blocker
Cause ?
CCB or Beta Blocker
Hypotension and bradycardiaMost beta blockers fairly benign
Exception: propranolol: Na channel blocking effect: manage as for tricyclic + Beta blocker
Calcium channel blockers: nasty
Treatment?
Beta blocker + CCBResuscitate if required: ABCsRisk assessment: look up to see how toxic the dose
could be.Supportive care and monitoring: if moderate risk:
resus bay, IV access, cardiac monitoring, IV fluids, trial of atropine, calcium gluconate, pressors eg dopamine. If high risk likely to need intubation
Investigations: ECG, paracetamol level, lactate, glucose.
Decontamination: Whole bowel irrigation likely to be needed eg Polyethylene glycol via NG tube
Beta blocker + CCB
Antidote/specific treatments: could call calcium an antidote to CCB, glucagon 5mg IV, high dose insulin 1 unit/kg then 1unit/kg/hour
Enhanced elimination: dialysis ineffective. Multidose activated charcoal may be effective for CCB.
Seek and treat complications: Likely to need ICU care. Monitor for MOF, rhabdo etc
If all of the above wasn’t working what else could be done?
Intraarterial balloon pumpBypass/ECMO
Most life threatening drug ingestions cause temporary CVS collapse – if we can support them through this the patient should do well
SulphonylureasLife threateningAntidote?
SulphonylureasAntidote: IV glucose then IV octreotide
IronWhat’s important about ironWhat’s the antidote
IronCan be life threatening and yet the patient is
asymptomatic, or has recoveredLook it upMost accidental ingestions not harmfulOver a threshold ingestion -> iron levels
usefulLow threshold for whole bowel irrigationAntidote: desferoxamine
Digoxin
What are the 2 main types of toxicity?What are the classic signs and symptoms?What is the antidote?
Digoxin2 main types of toxicity:
Acute ingestion – rare Chronic – usually due to dehydration/renal impairment
Consider this in any patient on digoxin who is unwell. Check ECG, K+ and digoxin level
Classic signs and symptoms Yellowed vision Nausea and vomiting Confusion Cardiac automaticity (ectopics or tachyarrythmia) and block
What is the antidote? Digoxin FAB fragments – “digibind” Expensive but cost effective
Indications for Digoxin FAB
Hemodynamically unstable or life-threatening dysrhythmia,
Hyperkalemia > 6 mmol/L (6 mEq/L)Plasma digoxin level > 20 nmol/L (15.6
ng/mL) at 6 hours post-ingestionDigoxin level > 10 nmol/L (7.8 ng/mL) or
elevated digoxin level + renal impairment + symptoms in chronic toxicity
Local anaesthetic
Eg femoral nerve block -> intraarterial
Classic signs?
Local anaesthetic
Perioral tingling
Others: Visual disturbanceSeizureVT
Antidote?
Local anaesthetic
Intralipid? Lipid sink? Cardiac fuel
Tricyclic / propranalol
Na channel blockadeNasty
HypotensionDecr LOCSeizureDysrhythmias
Antidote?
Na channel blockade"Prompt intubation, hyperventilation and
administration of administration of sodium bicarbonate at the first evidence of severe toxicity is life-saving"
Na channel blockade from TCA
Blue apnoeic patient dumped at the front door.
He has pin point pupils
How will you manage this patient?
IV opioid toxicity
Lots of techniques
BVM ventilate
400mcg IM naloxone200mcg IN naloxone
Oral opioid toxicity
If significant respiratory/LOC depression usually require naloxone infusion
Titrate IV nalaxone boluses to get just adequate reversal – don’t make the patient withdraw and run
Infusion of 2/3 of reversal dose/hour
Rare but nasty
Theophylline -> vomiting +++ -> needs urgent dialysis
Ethylene glycol
Neuroleptic Malignant SyndromeWhat is it?What do you do about it?
Neuroleptic malignant syndromeRareUsually an idiosyncratic reaction to
standard/high doses of antispychotic rather than a result of overdosage.
Life threatening“Malignant Parkinson’s”
Parkinsonism + fever + autonomic instabilityDoesn’t have the agitation, hyperreflexia or
clonus of serotonin syndrome
Neuroleptic malignant syndromeIf temp > 39.5 or rigidity compromising
ventilation -> RSICool to 38-39˚BenzodiazepinesTreat hypoglycaemiaBromocriptine +/or dantrolene
“My child might have taken some of granny’s pills”
Try to work out what Granny is onDefault
Blood sugarBPECGIf abnormal or toxidrome: IV line and treat
empirically.If normal: Observe 12 hours. Discharge if BP and
BSL normal
BenzodiazepinesAntidote – when do we use it?
FlumazenilAntidote to benzosAlmost never usedOnly used if we caused the ODFor chronic benzo users or coingestion with a
proconvulsant (eg TCA) flumazenil may cause seizure
Benzos almost never need treatment or intubation
Recovery position, wait for them to wake up
AlcoholAlmost never needs intubationRecovery position and observeLOC should improve hourly – if not consider
other diagnosis eg head injury
Activated charcoalAlmost never usedLittle proof of efficacyHas killed people - aspiration
Hydrofluoric acidNasty. 2% BSA exposure can kill
WarfarinVitamin K and prothrombin complex
(prothrombinex)
InsulinGlucose + foodOccasionally 10% glucose infusion
CO and cyanideHigh flow oxygen then look it upCyanide ? Amyl nitrate, Sodium nitrite,
sodium thiosulphate (or dicobalt EDTA where available)