Chapter 18. Poisoning
Four crucial questions must be asked:
• What was taken?
• How much was taken?
• When was it taken?
• What was taken with the overdose (e.g. alcohol)?
If possible, the paramedic should take any medicine containers found at the scene to the hospital along with the patient.
Always consider the possibility of alcohol consumption.
Poisoning in children is common, but not commonly serious. A typical case of poisoning in childhood is the accidental ingestion of a mildly toxic substance by a child aged 1–3 years. Most incidents are minor.
In the UK, the majority of children ingest therapeutic agents: paracetamol, iron, benzodiazepines, tricyclic antidepressants and the contraceptive pill are the most common. The remainder are usually poisoned by a variety of household products. The accidental ingestion is usually noticed rapidly by the parents and the children often present very soon after ingestion.
As a general rule, most cases of poisoning require no treatment other than maintenance of the vital signs. If this is achieved, the majority of patients will have a favourable outcome.
Examples of alerting clinical syndromes include:
• Rapid pulse rate – tricyclic antidepressants, antihistamines, amphetamines or other arrhythmogenic agents
• Low blood pressure – anticholinergic medications or vasodilators such as alcohol
• Increased respiratory rate – substances that cause shock, also salicylate overdose
• Decreased respiratory rate – opiate ingestion
• Dilated pupils – tricyclic antidepressants, amphetamines ingestion
• Constricted pupils – opiate ingestion
• Nasal bleeding or perioral sores – solvent abuse.
Specific poisons
Medications
Almost any medication can be harmful if taken in excess.
Benzodiazepines
Symptoms and signs
• Drowsiness
• Unconsciousness
• Respiratory depression (if taken with alcohol).
Management
• Clear and maintain the airway
• Support respiration (bag-mask ventilation if required)
• Monitor
• Transfer to hospital.
Antidotes
Although there is a specific antidote to benzodiazepines (flumazenil), there are dangers with its use. The patient may develop seizures as a result of benzodiazepine withdrawal or because other medications (e.g. tricyclic antidepressants) may also have been ingested. Should this happen, the seizures are extremely difficult to treat as the usual anticonvulsant in this situation – diazepam – will not work in the presence of the flumazenil. A further problem arises with the patient who revives following the administration of flumazenil, refuses further treatment and leaves the scene; because the effects of the flumazenil are short-lived, unlike the effects of the benzodiazepines, the patient may succumb again to the overdose, possibly when no witnesses are present to call for help.
Paracetamol
The most common over-the-counter medication taken in overdose is paracetamol. As noted previously, the great danger of this drug is that it is perceived as harmless.
Signs and symptoms
Early
• None
• Because there are often no immediately felt ill-effects after taking this drug, there may be a prolonged delay in seeking treatment and a reluctance to attend hospital.
Drowsiness suggests the ingestion of other medication, commonly a compound analgesic.
Late
• Hepatic failure
• Death.
Management
Immediate transfer to hospital for assessment of blood paracetamol levels and management.
Antidote
N-Acetyl-cysteine is a specific and highly effective antidote to paracetamol.
Tricyclic antidepressants
Tricyclic antidepressants are commonly prescribed to the patients who are most at risk of attempted self-harm. It is unfortunate that this group of drugs are among the most toxic medications when taken in overdose.
Signs and symptoms
• Depressed consciousness
• Seizures
• Cardiac arrhythmias (sinus tachycardia to ventricular tachycardia)
• Hypotension
• Tachypnoea
• Impaired ventilation.
Management
The management of these patients can be very challenging; however, the ABC approach will provide sufficient prehospital care for most of them.
• Clear and protect the airway
• Give oxygen via a face mask
• Ventilate if necessary via a bag-valve-mask system (hyperventilating the patient will help correct both metabolic and respiratory acidosis)
• Treat hypotension with an intravenous fluid challenge
• Monitor ECG – only treat symptomatic arrhythmias
• Control seizures with diazepam.
Antidote
In hospital, sodium bicarbonate is effective in treating acidosis.
β-Blockers
Signs and symptoms
• Bradycardia
• Hypotension
• Depressed conscious level.
Management
• Secure the airway
• Assist breathing
• Treat hypotension with intravenous fluid
• Treat bradycardia with 0.5 mg atropine intravenously*
• Use of an external pacemaker may also be considered.
Antidote
Glucagon 0.5–1.0 mg given IM or IV (and repeated up to 5 mg) has been shown to be of benefit in severe β-blocker poisoning. In such cases, the patient may require insertion of an intravenous pacemaker, therefore there should be no delay in taking the patient to the nearest hospital.
*Further doses (to a maximum of 3 mg) may be given if there is no effect or if the patient deteriorates after transient improvement.
Insulin
It is uncommon for insulin to be taken as a deliberate overdose, unless there is a genuine desire to die and steps are taken to avoid discovery, but accidental overdoses occur frequently.
Signs and symptoms
• Loss of consciousness
• Aggression
• Confusion
• Sweating.
Management
• Clear and maintain airway
• Obtain IV access
• IM glucagon
or
• Intravenous glucose.
Warm sweat drinks or Hypostop may be effective in aborting mild hypoglycaemia before it progresses.
NEVER FORGET TO CHECK THE BLOOD SUGAR IN A PATIENT WITH AN ALTERED CONSCIOUS LEVEL
Glucagon raises blood sugar by mobilising glucose from glycogen in the liver. In alcoholics or those with chronic liver disease, these stores will be depleted and glucagons will be ineffective.
Opiates
Opiates may be taken in overdose accidentally (in the case of the patient with chronic pain), intentionally, with a view to self-harm, or recreationally, by injecting drug abusers.
Signs and symptoms
• Depressed level of consciousness
• Depressed respiration (breathing tends to be slow and deep)
• Pinpoint pupils
• Hypotension
• Hypoxia
• Risk of aspiration of stomach contents
• Needle marks from IV drug abuse.
Management
• Secure the airway
• High flow oxygen
• Assist breathing
• Establish intravenous access
• Administer naloxone.
Naloxone dosage
IV boluses of 0.4 mg repeated to a maximum dose of 10 mg or until the patient begins to recover.
Failure to respond to a dose of 2 mg suggests that opiates are not responsible for the loss of consciousness.
The half-life, and therefore the effect, of naloxone is shorter than the effect of most commonly used opiates. The result of this is that the improvement in the patient’s condition may be short-lived and coma may return. A patient who is allowed to leave the scene may well lapse into another coma, possibly with no witnesses to summon help. One method that may be used in such cases is to administer intramuscular naloxone (1 mg) to the poisoned patient before giving the intravenous dose. In this way, if the patient leaves the scene following recovery, naloxone will be slowly released into the circulation from the IM dose and may prevent a relapse.
Household substances
Most household products in current use are of low systemic toxicity if accidentally ingested. Commonly ingested substances include bleaches, turpentine substitute, paraffin and household cleaning products. The treatment of ingestion of these substances is to administer oral fluids (milk) and rapidly transfer the patient to hospital. There may be local irritation of the mouth or oesophagus, but systemic toxicity is unusual. The patient should not be encouraged to vomit, as this may lead to a potentially fatal pneumonitis.
Plants and fungi
It is unusual for adults to eat poisonous plants, although mistakes occur occasionally. Poisoning is more common in children.
The quantities involved are usually small because the plant material is sufficiently unpalatable to prevent consumption of more than very minimal amounts.
The most common plant poisoning in Britain is the ingestion of laburnum seeds ingestion of more than 10 seeds is considered dangerous.
The treatment of laburnum poisoning is the same as that for all plant ingestions: evaluation and support of the airway, breathing and circulation and transportation of the patient to hospital.
Many poisonous fungi can be mistaken for edible mushrooms, but serious poisoning is rare.
Usually, patients who have ingested fungi have a violent but self-limiting attack of abdominal pain, diarrhoea, nausea and vomiting about 2 hours after the ingestion.
There may be signs of excessive cholinergic stimulation (bronchospasm, bradycardia, constricted pupils and collapse). This can be treated with boluses of intravenous atropine, but this may exacerbate any agitation or hallucinations.
The patient and the fungi should be taken to the nearest hospital as soon as possible.
Wherever possible, take a sample of the ingested plant to hospital for identification.
Effects of laburnum ingestion
• Burning mouth and throat
• Nausea
• Abdominal pain
• Vomiting
• Diarrhoea
• Drowsiness
• Incoordination
• Delirium
• Twitching
• Coma.
Inhalational agents
A number of substances are harmful if inhaled. The two main groups of inhalational ‘poisons’ are the recreational drugs and substances inhaled accidentally or for deliberate self-harm (carbon monoxide and other gases). The treatment of the first group is rapid assessment of the airway, breathing and circulation, supportive care, administration of naloxone in the case of opiate poisoning and rapid transport to hospital.
The second group is important because in these cases, there is a danger to the paramedic. Care should be taken that the paramedic does not become a secondary casualty by inhaling the toxic fumes. If it is possible to approach safely, the patient should be removed from the environment and given high-concentration oxygen.
Recreational drugs
The general effect of these drugs is to affect the central nervous system, producing depression (opiates and benzodiazepines) or stimulation (Ecstasy, amphetamines and cocaine). The treatment of poisoning by these substances is the assessment and support of airway, breathing and circulation, the administration of naloxone in opiate poisoning and rapid transport to hospital.
For further information, see Ch. 18 in Emergency Care: A Textbook for Paramedics.
