toxicology

Approaching the Poisoned Patient!!

ObjectivesProvide a general overview of toxicology

How to approach the poisoned patient

Understanding common toxidromes

What is ToxicologyWhat is it not a poison? All things are poison

and nothing is without poison. Solely the dose determines that a thing is not a poison.

-Paracelsus (1943-1541), the Renaissance Father of Toxicology, in his Third defence

Why do people OD? Significant portion intend to die at time of overdose

Most want to escape an intolerable situation or state of mind

Small minority of patients want to punish someone or make someone feel guilty

Mental health difficulties particularly, depression, ETOH or substance misuse, and personality disorders are frequently seen

Inability to tolerate life stressor or events, relationship breakdowns, anniversaries of bereavement, ect.

Mitchell, A. Dennis, M. Self harm and attempted suicide in adults: 10 practical questions and answers for emergency department staff. Emerg

Med J, 2006: 26, 251-255

What Drugs do they OD on?ETOH

Paracetamol

Benzo’s

Antipsychotics

Antidepressants

Antiepileptic

Opiods

And many many more!!!

Risk Assessment RRSIDEAD Approach

Resuscitation

Risk Assessment

Supportive Care & Monitoring

Investigations

Decontamination

Enhanced Elimination

Antidotes

Disposition

ResuscitationAirway

Breathing

Circulation

Control seizures

Correct hypoglycaemia

Correct hyperthermia

Consider resuscitation antidotes

Risk AssessmentAgent

Dose

Time since ingestion

Clinical features and course

Patient factors

Geographical location


Supportive Care

Airway: Intubation

Breathing: O2, Ventilation

Circulation: IVIH, Inotropes, Defib or pacing

Sedation: Titrate Benzo’s

Seizure control/prophylaxis: Titrate Benzo’s

Metabolic: control pH, normoglycaemia

Fluids & Electrolytes: Monitor

Renal function: hydrate, haemodialysis

General: Bladder care ? IDC, Nutrition, DVT & Stress ulcer prophylaxis, PAC, Monitor mental state

Can good supportive care can be done at home?


Monitoring & investigation:

12 lead ECG

Paracetamol Level

BSL below 4 correct with D50

Temp above 38.5 requires continuous monitoring

Drug Levels

Paracetamol

Cabamazepine

Lithium Salcicylate Digoxin

Methanol Theophyline Ethanol Methotrexate Valproic Acid

Ethylene glycol

Iron Phenobarbitone

The ECG in TOXValuable inexpensive screening tool

QRS widening R/T sodium channel blockade, common with TCA overdose

QT prolongation is a potassium channel effect associated with TDP, common in some antidepressant, antiarrythmics, & antipsychotic overdoses.

Urine Drug ScreenWhy don’t we do it?

In general it rarely if ever changes management.

Expensive

Takes 1-2 days to get back

When would we consider it?

Gastrointestinal Decontamination

Methods:

Induced Emesis (Syrup of ipecac)

Gastric Lavage

Activated Charcoal

Whole Bowel Irrigation

Activated charcoal has most benefits in a limited number of poisoning, other methods have limited if any evidence to support their use.

Enhanced EliminationMultiple-dose activated charcoal

Urinary alkalinisation

Haemodialysis and haemofiltration

Charcoal haemoperfusion

AntidotesLimited number of antidotes available for

limited number of poisonings.

Common Antidotes:

1 NAC

2 Naloxone

3 Sodium Bicarb

4 Digoxin Immune Fab

5. Octreotide

Common Complications in the Critically Poisoned Patient

Aspiration Pneumonia

ARDS

ARF

DVT/PE

Rhabdomyolysis

Compartment Syndrome

Hepatotoxicity

DispositionThe patients journey can be:

RESUS

ICU

Assessment

Obs ward

Psych

Or patients with DSP need Pysch R/V

Poisoning in Children Most paediatric poisoning are benign, as children

generally ingest small quantities.

Always base your assessment on worse case scenario:

The time of ingestion is assumed to be the latest possible time

Assume all missing or unaccounted for agent(s) have been ingested

Do not attempt to account for spillage, which is difficult to estimate

If more than child involved, it is assumed that each child ingested all the missing or unaccounted for agent(s)

2 tablets that can KILL a 10kg toddler

Agent Features of Toxicity

AmphetaminesMethamphetamineMDMA

Agitation, confusion, hypertension, hyperthermia

Calcium channel blockers Delayed onset of bradycardia, hypotension, conduction defects, refractory shock

ChloroquineHydroxychloroquine

Coma, seizures, cardiovascular collapse

Dextropropoxyphene Ventricular Tachycardia

OpiodsOxycodoneMethadoneMorphine sulfateDiphenoxylate/atropine

Coma, respiratory arrest, may be delayed with controlled release products

Propanolol Coma, seizures, ventricular tachycardia, hypoglycaemia

Sulfonylurea's Hypoglycaemia onset can be delayed up to 8 hours

Theophylline Seizures, SVT, vomiting

Tricyclic antidepressants Coma, seizures, hypotension, ventricular tachycardia

Management of child who ingest unidentified poison

Admit for minimum of 12-hour observation

Ensure health care facility can cope

Defer IV access until evidence of toxicity

Check BSL at presentation and on D/C

Monitor GCS & vital signs

Cardiac monitor if decreased GCS or abnormal vital signs

D/C during daylight hours

Poisoning in Pregnancy Need to assess risk to fetus or infant if lactating

Management rarely differs from non pregnant patients

Agents that pose greater risk to fetus:

1 Carbon Monoxide

2 Methaemoglobin-inducing agents

3 Lead

4 Salicylates

Need to provide risk/benefit analysis if breastfeeding is to continue as the mother recovers

Poisoning in the ElderlyCan be challenging to manage R/T co-morbidities,

decreased physiological reserve, and multiple prescribed medications.

Higher complication rate and longer hospital admission:

Pharmacokinetic changes:

Delayed gastrointestinal absorption

Decreased protein binding ^ free drug levels

Reduced hepatic metabolic function

Decreased GFR which impairs elimination

Common poisoning in the Elderly

Digoxin

Metformin

Lithium

Disposition= Generally elderly patients end up in Gen Med units for prolonged periods of care

Toxidromes

Coma Patients presenting with coma have generally

overdosed on a drug with CNS depressant effects.

Can be caused by secondary effects:

1 Hypoxaemia

2 Hypoglcaemia

3 Hyponatraemia

4 Hypotension

5 Seizures

6 Cerebral oedema

Coma Management RRSIDEAD

Good supportive care & airway management

Treat secondary effects

Look at what else can cause coma

1 Neurotrauma

2 Metabolic encepathopathy

3 Menigioencephalopathy

4 Space occupying lesion

Patients generally go to ICU, till conscious states improve

Look for complication’s (Asp Pneumonia)

Why do we use Diazepam so much in TOX?

Good safety profile

Long half life

Controls agitation well

Used to treat toxic seizures

Generally drug of choice in managing withdrawals

Dose adult 5-10mg, child 0.1-0.3mg/kg/dose every 3-5mins

Anticholinergic Syndrome

Results from the competitive, reversible blockade of central & peripheral cholinergic blockade.

Is potentially life threatening

Diagnosed clinically by agitated delirium and peripheral muscarinic blockade

History of ingestion of known anticholinergic agent

Types of Anticholinergic Agents

Antipakinson drugs (benztropine, amantadine) Antihistamines (prometazine, doxylamine) Antitussives (dextromethorphan) Antidepressants (TCA) Antipsychotic agents including atypical (Haloperidol, olazapine,

Quetiapine) Anticonvulsant agents (carbamazapine) Motion sickness agents (hyoscine-scopolamine) Antimuscarinic agents (Atropine) Topical ophthalmological agents Bronchodilators (Ipratropium) Urinary antispasmodic agents (oxybutynin) Muscle relaxants Plants & herbal remedies (Selected mushrooms)

Clinical Features of Anticholinergic Syndrome

Central Peripheral

Agitated delirium characterised by:

Mydriasis

•Fluctuating mental status Tachycardia

•Confusion Dry mouth

•Restlessness Dry skin

•Fidgeting Flushing

•Visual hallucinations Hyperthermia

•Picking at objects in the air Sparse or absent bowel sounds

•Mumbling slurred speech Urinary retention

•Disruptive behaviour

Tremor

Myoclonus

Coma

Seizures (rare)

Remember the saying!!!Hyperthermia (HOT as a hare)

Flushed (RED as a beet)

Dry Skin (DRY as a bone)

Dilated pupils (Blind as a bat)

Delirium, hallucinations (Mad as a hatter)

Tachycardia

Urinary Retention

Management Good Supportive Care

IV fluids

IDC

Diazepam to control agitation

Avoid drugs with anticholinergic effects

Antidote:

Physostigimine

Reverse anticholinergic delirium in selected patients that don’t respond to benzo’s

Serotonin SyndromeClinical diagnosis based on history of ingestion

of one or more serotonergic agents, the presence of characteristic symptoms, & high index of suspicion

Clinical features fall into 3 categories

1 CNS

2 Autonomic

3 Neuromuscular

Clinical features of serotonin syndrome

CNS Autonomic Neuromuscular

Apprehension Flushing Tremor *

Agitation, psychomotor delirium*

Mydriasis* Clumsiness

Hallucinations Sweating * Hyperreflexia *

Seizures* Tachycardia * Clonus *

Coma Hyperthermia * Myoclonus *

Hypertension * Increased limb tone (lower limbs > upper limbs

Hypotension Rigidity

Clonus & Hyperreflexia are highly diagnostic of serotonin syndrome

Diarrhoea *

Life threatening serotonin syndrome

Characterised by:

• Generalised rigidity

• Autonomic instability

• Delirium

• Coma

• Hyperthermia

• Secondary multiple-organ failure

Agents implicated in serotonin syndrome

SSRIs (fluoxetine, setraline, paroxetine)

SNRIs (venlafaxine, citalopram, bupropion)

TCAs (amitriptyline, dothiep)

MAOIs (phenelzine, moclobemide)

Lithium

Analgesic (pethidine, tramadol, dextromethorphan)

Antiemetics (metaclopramide, ondansetron)

Anticonvulsants (valproic acid)

Drugs of abuse (amphetamine, MDMA)

Managing Serotonin Syndrome

RRSIDEAD

Check BSL

Check temp >38.5 continuous core monitoring, temp > 39.5 paralysis and intubate

Give benzo’s to achieve gentle sedation

HT & tachycardia generally respond to benzo’s, if refractory trial of GTN infusion

Antidote: Cyproheptadine, given orally or via NG

The Tox Bible

THE END!!

toxicology

Health & Medicine