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Information ⬇

Author(s): Nigel Langford and David Sprigings

  • In the UK, if you need advice about the management of a patient with severe or complex poisoning (e.g. multiple medications taken, pregnancy or major comorbidities), contact the National Poisons Information Service (NPIS) for advice (24-hour phone line, 0344 892 0111).
  • Information on poisons and the management of poisoning is also available at the TOXBASE website (www.toxbase.org) (the primary clinical toxicology database of the NPIS; user name and password needed).
  • Management of the patient with suspected poisoning is summarized in Figure 36.1.

Priorities ⬆ ⬇

Outline

The Unconscious Patient with Suspected Poisoning!!navigator!!

  1. Stabilize the airway, breathing and circulation
    • For detailed guidance, see Chapters 1, 59, 112 (airway management), 11 and 113 (management of respiratory failure) and 2 (management of hypotension and shock).
    • If carbon monoxide poisoning is suspected (Appendix 36.2), give oxygen 10L/min by a tightly fitting facemask with a circuit which minimizes rebreathing.
  2. Exclude and correct hypoglycaemia
    • If blood glucose is <4.0 mmol/L, give 100 mL of 20% glucose or 200 mL of 10% glucose over 15–30 min IV, or glucagon 1 mg IV/IM/SC.
    • Recheck blood glucose after 10 min: if still <4.0 mmol/L, repeat the above IV glucose treatment.
    • In patients with malnourishment or alcohol-use disorder, there is a remote risk of precipitating Wernicke encephalopathy by a glucose load: prevent this by giving thiamine 100 mg IV before or shortly after glucose administration.
    • See Chapter 81 for further management of hypoglycaemia.
  3. Treat prolonged or recurrent major seizures
    • Take into account pre-hospital treatment. Give lorazepam (which is less likely to cause respiratory suppression) 0.1 mg/kg (typically 4–8 mg) IV over 5–10 min (Table 16.2), midazolam 10 mg buccally (NICE-recommended, but only licensed in patients <18 years), or diazepam 10–20 mg IV at a rate of <2.5 mg/min (faster injection rates carry the risk of sudden apnoea).
    • If the seizure does not terminate, give a second dose, to a maximum total dose of lorazepam 8 mg or diazepam 40 mg.
    • See Chapter 16 for further management of seizures/status epilepticus.
  4. Give naloxone, if opioid poisoning is possible or must be excluded
    • If the respiratory rate is <12/min, or the pupils are pinpoint, or there is other reason to suspect opioid poisoning, give naloxone 800μgm IV every 2–3 min up to a total dose of 4000μgm or until the respiratory rate is >15/min. Large doses may be required in a severely poisoned patient or if synthetic opioids have been taken. Aim for reversal of respiratory depression, not full reversal of consciousness.
    • If there is a response to bolus naloxone, start an IV infusion: make up a naloxone solution with 10 mg naloxone (25 vials) made up to a final volume of 50 mL with glucose 5% (200μgm/mL) and infuse using an IV pump. Start the infusion at 60% of the initial dose required for resuscitation per hour, and titrate against the respiratory rate and conscious level.
    • In patients who have taken partial opioid agonists such as buprenorphine, methadone and tramadol, repeated large (1200μgm) doses of naloxone may be required to achieve a satisfactory response.
    • If there is no response to naloxone, this suggests that another CNS depressant has been taken or brain injury has occurred.

  5. Obtain the history

    The history should be obtained from all available sources: ambulance personnel, friends and family, primary care and hospital records.

  6. Make a systematic examination
    • The clinical features may provide clues to the poison (Tables 36.1 and 36.2). Mixed poisoning is common.
    • Bear in mind the possibility of multiple pathology (e.g. poisoning followed by head injury; poisoning on a background of chronic liver disease). Points to cover in the neurological examination of the unconscious patient are given on p. 18.
    • Is there evidence of IV substance use? Check for needle marks in the antecubital fossae, neck, supraclavicular areas, groins, dorsum of feet and under the tongue. IV substance use may be complicated by venous thrombosis, cellulitis and, rarely, botulism.
    • Check for possible complications of coma (hypothermia, pressure necrosis of skin or muscle, corneal abrasions, inhalation pneumonia).

  7. Investigations

    These are needed urgently and are given in Table 36.3. The results may provide further clues to the poison. Urine is preferable to blood for qualitative analysis as toxins are concentrated in the urine.

  8. Discuss management with an intensivist and arrange admission to ICU if:
    • The Glasgow Coma Scale score is 8 or below, or there are recurrent seizures.
    • There is respiratory failure despite administration of antidotes, or an endotracheal tube has been placed.
    • There are major arrhythmias or the patient is at high risk of arrhythmias (e.g. tricyclic poisoning with broad QRS complex).
    • There is hypotension or severe acidosis (pH <7.2) not responding to fluid resuscitation.

The Conscious Patient with Poisoning!!navigator!!

  1. Check baseline observations

    Document conscious level (fully orientated or confused – use AVPU score), pulse, blood pressure, respiratory rate, arterial oxygen saturation, temperature and blood glucose.

  2. Establish:
    • Which poisons were taken, in what amount and over what period.
    • If the patient has vomited since ingestion, and when (unlikely to have eliminated significant amounts of poison if over an hour from ingestion).
    • Current symptoms.
    • Associated physical or psychiatric illness.
  3. Investigations needed will depend on the poisons and the presence of other physical illness. After poisoning with some drugs (Table 36.4), plasma levels should be checked.

  4. If the patient is at risk of harm but refuses treatment

    Ask the help of a senior colleague and a psychiatrist. Issues of mental capacity and consent to treatment are discussed in Chapter 111.

Further Management ⬆ ⬇

Outline

Is a Specific Antidote or Treatment Indicated?!!navigator!!

  • See Table 36.5. Discuss the case with a Poisons Centre first, unless you are familiar with the poison and its antidote, as some antidotes may be harmful if given inappropriately.
  • The management of paracetamol and carbon monoxide poisoning is given in Appendices 36.1 and 36.2.

Reducing Absorption!!navigator!!

Activated charcoal (50g mixed with 200 mL of water) should be given if a significant amount of any poison has been ingested within 1h (or longer if modified-release preparations or drugs with anticholinergic effects have been taken), and oral antidotes are not indicated (Table 36.6). Exceptions to this are poisoning with substances which are poorly absorbed by charcoal. Because of the risk of inhalation, activated charcoal should not be given to a patient with a reduced conscious level unless the airway is protected by a cuffed endotracheal tube.

Gastric lavage should not be employed in the management of poisoned patients, as the risks of complications outweigh any benefits.

Increasing Elimination!!navigator!!

  • Drugs whose elimination can be increased by repeated dosing with activated charcoal are given in Table 36.6. Give 50g initially then 25g 4-hourly by mouth or nasogastric tube until recovery or until plasma drug levels have fallen to within the safe range. Laxatives may also be required.
  • Other methods (e.g. haemodialysis) may be indicated in selected cases, after discussion with a Poisons Centre.

Monitoring!!navigator!!

In all patients with severe poisoning, monitor:

  • Conscious level (initially hourly).
  • Respiratory rate (initially every 15 min).
  • Oxygen saturation by pulse oximeter (continuous display).
  • ECG monitor (continuous display).
  • Blood pressure (initially every 15 min).
  • Temperature (initially hourly).
  • Urine output (put in a bladder catheter if the poison is potentially nephrotoxic, the patient is unconscious or there is significant haemodynamic collapse).
  • Arterial blood gases and pH (initially 2-hourly) if the poison can cause metabolic acidosis (Table 36.1) or there is suspected acute respiratory distress syndrome or after inhalation injury.
  • Blood glucose if the poison may cause hypo- or hyperglycaemia (initially hourly) or in paracetamol poisoning presenting after 16h (initially 4-hourly).

Monitoring should be continued until the time symptoms are likely to develop has passed or until the patient has recovered. Specific times for individual drugs can be found in TOXBASE. Prolonged observation may be required for patients who have taken sustained release medication.

Supportive Care!!navigator!!

  • Unconscious patients not requiring endotracheal intubation or transfer to ICU (see above) should be nursed in the recovery position in a high-dependency area (level 2).
  • Management of problems commonly seen after poisoning is summarized in Table 36.7.

Psychiatric Assessment!!navigator!!

All patients with deliberate self-poisoning should have a psychiatric assessment, performed when recovered from the physical effects of the poisoning. Points to be covered include:

  • The circumstances of the overdose: carefully planned, indecisive or impulsive; taken alone or in the presence of another person; action taken to avoid intervention or discovery; suicidal intent admitted?
  • Past history of self-poisoning or self-injury; psychiatric history or contact with psychiatric services; alcohol or substance use disorder.
  • Family history of depression or suicide.
  • Social circumstances.
  • Mental state: evidence of depression or psychosis?

Patients at increased risk of suicide (Table 36.8) and those with overt psychiatric illness should be discussed with a psychiatrist. Follow-up by the primary care physician or psychiatric services should be arranged before discharge.

Management (Figure 36.2)Management (Figure 36.2)

Patient Seen Within 8 H after Poisoning!!navigator!!

  • Give activated charcoal 50g if <1h since ingestion and >75 mg/kg paracetamol has been ingested.
  • Take blood for plasma paracetamol level at or after 4h since ingestion.
  • If the plasma paracetamol concentration at four or more hours post ingestion is less than the paracetamol treatment line, the patient is asymptomatic and the investigations are normal, there is no risk of serious complications, the patient may be discharged following psychiatric assessment.
  • Start acetylcysteine (AC) (Table 36.9) if the plasma paracetamol level is above the treatment line (Figure 36.2).
  • If the plasma paracetamol level is not available by 8h, begin AC if >75 mg/kg of paracetamol has been taken.
  • Discontinue AC if the plasma paracetamol level is below the treatment line.
  • On completion of AC treatment, check the prothrombin time, alanine transaminase/aspartate transaminase activities and plasma creatinine.
  • If the patient is asymptomatic post AC treatment and the investigation results are normal (INR <1.3, ALT <2 × upper limit normal, creatinine normal), there is no risk of serious complications and the patient may be discharged (with appropriate written advice), after psychiatric assessment.

Patient Seen 8–24 H after Poisoning!!navigator!!

  • Take blood for plasma paracetamol level, prothrombin time, alanine transaminase/aspartate transaminase activities, plasma creatinine and bilirubin, acid-base status (venous sample) and full blood count.
  • Start AC immediately (Table 36.9) if >75 mg/kg paracetamol has been taken.
  • Discontinue AC if the plasma paracetamol level is below the treatment line (Figure 36.3).
  • On completion of AC treatment repeat above investigations (except paracetamol level).
  • If the investigations are abnormal or if the patient is symptomatic, consider continuing AC treatment (100 mg/kg in 1L 5% glucose over 16h, repeated until recovery (INR less than or equal to 1.3 or falling on two consecutive blood tests and is less than 3.0)). Repeat investigations as appropriate.
  • If the patient is asymptomatic following treatment and the investigation results are normal (INR <1.3, ALT <2 × upper limit normal, creatinine normal), there is little risk of serious complications. The patient may be discharged (with appropriate written advice), after psychiatric assessment.

Patient Seen >24 H after Overdose!!navigator!!

  • Take blood on admission for plasma paracetamol level, prothrombin time, alanine transaminase/aspartate transaminase activities, plasma creatinine, bilirubin and phosphate, acid-base status (venous sample), glucose and full blood count.
  • If the patient has taken >150 mg/kg paracetamol, is symptomatic, or has abnormal investigation results, give a standard course of AC (Table 36.9).
  • Repeat the above investigations at the end of the AC course.
  • Normal blood tests at 24 hours indicate that serious liver toxicity has not occurred and treatment can be discontinued. Patient may be discharged (with appropriate written advice), after psychiatric assessment.

Severe Hepatotoxicity!!navigator!!

Make early contact with a Liver Unit if the patient has evidence of severe hepatotoxicity (Table 36.10). In such patients (before transfer):

  • Start a course of acetylcysteine if not previously administered.
  • Give glucose 10% 1L 12-hourly IV to prevent hypoglycaemia, and monitor blood glucose 4-hourly.
  • Monitor conscious level 4-hourly.
  • Monitor CVP and urine output: correct hypovolaemia with crystalloid.
  • Check prothrombin time 12-hourly and plasma creatinine daily.
  • Start prophylaxis against gastric stress ulceration with omeprazole 40 mg daily IV by mouth or by nasogastric tube.
  • See Chapter 77 for other aspects of the management of acute liver failure.
Management (Figure 36.4)Management (Figure 36.4)
  1. If carbon monoxide poisoning is suspected, give 100% oxygen (10L/min) using a tightly fitting facemask with a circuit which minimizes rebreathing. Unconscious patients should be intubated and ventilated mechanically with 100% oxygen. Cerebral oedema may occur and is treated with mannitol and mild hyperventilation (Table 36.7).
  2. Attach an ECG monitor and record a 12-lead ECG. Severe poisoning may result in myocardial ischaemia, with anginal chest pain, ST segment depression and arrhythmias. Check arterial blood gases and pH (metabolic acidosis is usually present) and arrange a chest X-ray.
  3. Check the carboxyhaemoglobin (COHb) level in blood (heparinized sample) (most arterial blood gas analysers will do this). If acute carbon monoxide poisoning is confirmed (COHb >10%), recheck 2-hourly and continue 100% oxygen until two consecutive samples contain <5%.
  4. Although its effectiveness is disputed, generally accepted indications for hyperbaric oxygen therapy are:
    • Carboxyhaemoglobin level >40% at any time
    • Coma
    • Neurological symptoms or signs other than mild headache
    • Evidence of myocardial ischaemia or arrhythmias
    • Pregnancy

Contact a Poisons Centre to discuss the management of severe poisoning and for the location of the nearest centre which can provide hyperbaric oxygen therapy.

Further Reading ⬆

Chen H-Y, Albertson TE, Olson KR (2015) Treatment of drug-induced seizures. Br J Clin Pharmacol 81, 412–419. http://onlinelibrary.wiley.com/doi/10.1111/bcp.12720/pdf.

National Institute for Health and Care Excellence (2016) Self-harm: long-term management.

Clinical guideline (CG133). https://www.nice.org.uk/guidance/cg133.