Toxicology Clinical Background



Background

Poisoned patients represent >2% of patients presenting to the ED and 5% of admissions. National UK figures demonstrate that mortality is 1% of admitted patients. Total deaths 2500 per year. Most due to opiates, then Paracetamol (up to 500 per year) then tricyclics (mainly Dothiepin).

Resuscitation

Airway - High flow O2. Endotracheal intubation if no swallow. Semi-prone position otherwise. Suction always available.

Breathing - needs support with bag mask valve? Reversible depression (Naloxone?). Consider ETT in all requiring BMV

Circulation - pulse, BP and respiration rate and ECG monitor. Establish IV access for ALL except the most minor overdose cases. Perform external cardiac compression if no cardiac output or severe hypotension. Rehydrate if hypotensive and no evidence of fluid overload

Disability - Seizures - treat with IV Diazemuls. Exclude indirect cause

hypoxia, hypoglycaemia, hypotension, withdrawal of alcohol, opioids, barbiturates, benzodiazepines

History What? When? How much?

  • information from witnesses or GP re regular medication
  • consider access to other drugs
  • alcoholic intoxication very commonly co-exists
  • does the history suggest other causes of coma?

Symptoms & signs

In your standard assessment, pay attention to the following features:

Note on Examination

  • burns around mouth
  • sweating
  • colour, respiratory rate, depth of respiration
  • pupils
  • exclude injury
  • conscious level and behaviour
  • injection marks/blisters
  • hydration
  • odour on breath
  • temperature (rectal for hypothermia)

Investigations

  • Glucose
  • U&E
  • Salicylate & Paracetamol
  • ECG
  • ABG / spirometry
  • Urine (50ml) and 
  • Lithium Heparin Blood sample for toxicology if necessary

    Aside - please remember - "CHIPS"

    Commonly seen radio-opaque tablets

    C - Chloral hydrate

    H - Heavy metals

    I - Iron / Iodine

    P - Psychotropics

    S - Sustained releases (enteric coated) preparations

Management

In many cases, this is supportive only. More active treatment may be appropriate as follows:

Urgent antidotes/measures:

  • Naloxone (divided doses up to 2 mg initially in adult) for opioid poisoning (limited effect in Buprenorphine OD)
  • Oxygen for CO poisoning
  • Dicobalt edetate (Kelocyanor) for cyanide poisoning
    • Only if patient losing or lost consciousness = 300 mg slowly IV, then repeat if required
  • Atropine for organophosphate poisoning
    • Cholinergic effects
    • 2 mg IV repeatedly until pulse rate over 80 (saturation of cholinergic receptors at 3mg)
  • Slow rewarming for hypothermia
  • Water or milk at once if corrosives ingested
  • Cool if hyperthermic
    • after MAOI's, paralysis/ventilation will reduce temperature
  • Zagreb adder anti-venom = only if bite mark, swelling and signs of systemic toxicity
  • Calcium Gluconate for fluorides, HF acid
  • Fuller's earth + Mg SO4 purge for paraquat
  • Methionine - see Paracetamol section

Gastric Emptying

There are almost no indications for gastric emptying (even TCAD overdose) [Bestbets]).

Similarly, gastric lavage should not be considered unless a patient has ingested :

  • A potentially life-threatening amount of poison
  • AND the poison is not absorbed by charcoal
  • AND the lavage can be undertaken within 60 min of ingestion  (TCADs up to 6 hours post ingestion)
  • AND patient fully conscious OR intubated

Activated charcoal

  • Charcoal may be indicated in patients who
    • Are alert (and likely to remain alert) or are already intubated and
    • are within 2 hours of ingestion (of substance known to be absorbed by charcoal)
  • Substances not absorbed by charcoal
    • Cyanide
    • Ethanol / methanol / ethylene glycol
    • Boric acid
    • Iron, Lithium
    • Strong acids and alkalis
    • Petroleum distillates
    • Malathion
  • Activated charcoal absorbs 10% of its own weight in toxin 50g charcoal will absorb 5g drug
  • Charcoal side effects
    • Acute: Nausea and vomiting
    • Delayed: Severe pneumonitis if aspirated
    • Constipation

Multiple dose activated charcoal

Should only be considered if a patient has ingested

  • A life-threatening amount of 
    • Carbamazepine
    • Dapsone
    • Phenobarbitol
    • Quinine
    • Theophylline
MDAC does increase elimination of (but there is insufficient data to support or exclude the use of this therapy)
  • Amitriptyline, Dextropopoxyphene, Digitoxin, Digoxin
  • Disopypramide, Nadolol, Phenylbutazone
  • Phenytoin, Piroxicam and Sotalol

MDAC is not recommended in in salicylate poisoning

Admission policy

Admit all overdose patients to the Emergency Department CDU overnight

  1. There may be medical problems related to the overdose that need attention
  2. Patients awaiting tests (eg 4 hourly Paracetamol level) should wait in the CDU
  3. Admission overnight often takes the heat out of the precipitating situation
  4. After a brief reflective period, a more accurate psychiatric assessment is possible.
  5. Admission overnight gives time for issues to be resolved. The patients are reviewed regularly by the EM consultants.


Content by Dr Íomhar O' Sullivan 02/04/2004.   Reviewed by Dr Chris Luke, Dr ÍOS 17/07/2005, Dr ÍOS 25/01/2007.Last review Dr Chris Luke 11/09/14.