Category: Toxicology

Nitrous Oxide Induced Neurotoxicity

Nitrous Oxide  has been used clinically and recreationally since its discovery in 1772. Since then Nitrous Oxide induced neurotoxicity have been reported, and has been shown to be dose depaendant. With infrequent users unlikely to be at risk of neurotoxicity, while heavier and habitual used at risk of serious neurological conserquences.

With the increase in recreation use of “Whippits” we need to remember to take a detailed recreation drug history when seeing patients presenting to ED with neurological symptoms. As Nitrous Oxide induced neurotoxicity is treatable.

Presentations

Nitrous Oxide induced neurotoxicity can present as either spinal cord demyelination , peripheral neuropathy or a a combination of the two.

  • Demyelination of the dorsal columns of spinal cord 
    • Typically onset is subacute  (i.e. weeks), but acute onset has been reported in the literature
    • Typically symmetrical but can be unilateral
    • Signs
      • Pyramidal weakness – weak upper limb extensors, and lower limb flexors
      • Dorsal Column Sensory loss – Vibration, Proprioception, Fine touch
      • Sensory Ataxia – Incoordination due to loss of proprioception and weakness
    • Level – Most frequently cervical 4-6 levels, but can affect any.
  • Peripheral Neuropathy
    • Typically Symmetrical (but not always)
    • Sensory loss (often painful)
    • Distal Weakness
  • Optic Neuropathy  – has been reported and may present with visual disturbance.

Pathophysiology

Nitrous Oxide usage can render vitamin B12 inactive, which in-turn disrupts myelination, causing the demyelination of nerves.

Differentials

  • Deficiencies: B12, Folate, copper, zinc
  • Inflammatory: Guillian-Barre syndrome, MS, Neurosarcoidosis
  • Infection: HIV, Syphilis
  • Cancer
  • Vascular: Spinal cord ischaemia, vasculitis

Tests

  • Vitamin B12 level (often in normal range)
  • Homocysteine and Methylmalonic Acid Level (not available in ED)
  • MRI – contrast enhanced

Treatment

Start before Tests are back (i.e. on clinical suspicion)

  • IM Vitamine B12 1mg OD
  • PO Folic Acid 5mg OD

Follow-up

  • Discuss admission with Medical team as potential for SDEC management
  • Treat until clinical improvement(King’s Team noted the following)
    • Sometimes treat for 5-7days only
    • Often switch to alternate days IM Bit B12
    • Can teach to self administer
  • Further Testing
    • Homocysteine and Methylmalonic Acid levels – often improve quickly
    • MRI often lags clinical improvement endnote necessary to repeat
  • Majority Improve clinically – but futureabstinence is often challenging

 

References

Drugs & Alcohol misuse in young people

Ending up in the ED as a result of alcohol and or substance use is NOT normal behaviour

  • Children who use alcohol or other substances are hugely vulnerable to sexual exploitation and other forms of abuse.
  • The use of alcohol or drugs can be encouraged as part of the grooming process, or as a means of coping with a difficult situation for the young person.
  • It is also likely that friends and close acquaintances of the young person are equally vulnerable.

Read more

LA – Toxicity

We are regularly doing femoral blocks next to major vessels. So warn the patient of the symptoms, & keep them monitored(at least 15 min).

Symptoms of local anaesthetic toxicity

  • Circumoral and/or tongue numbness
  • Metallic taste
  • Lightheadedness/Dizziness
  • Visual/Auditory disturbances (blurred vision/tinnitus)
  • Confused/Drowsiness/Fitting
  • Arrhythmia
  • Cardio-Resp Arrest

Remember – Do basics WELL

Intralipid – in antidote cupboard (Green Majors treatment room)

    1. Bolus – 1.5ml/kg 20% lipid solution over 1min
    2. Then start Infusion – 15ml/kg/hr 20% lipid solution
    3. 5 mins reassess if Cardiac instability/deterioration
      • Rpt Bolus 1.5ml/kg over 1min (max 3 boluses inc. initial)
      • Increase infusion rate – up to 30ml/kg/hr
      • Total Max dose 12ml/kg

Propofol is not a suitable substitute for lipid emulsion

Without Cardio-Resp Arrest

Use conventional therapies to treat:

  • Seizures
  • Hypotension
  • Bradycardia
  • Tachyarrhythmia (Lidocaine should not be used as an anti-arrhythmic therapy)

In Cardio-Resp Arrest

  • CPR – using standard protocols (Continue CPR throughout treatment with lipid emulsion)
  • Manage arrhythmias – using standard protocols
  • Consider the use of cardiopulmonary bypass if available
  • Recovery from LA-induced cardiac arrest may take >1 h
  • Lidocaine should not be used as an anti-arrhythmic therapy

PDF:la_tox

 

2. HAZMAT – Suspected Contamination Incident

So a patient comes to ED after white powder thrown is at them what do you do? Your initial response can help them and everyone in the department!

  1. Ask them to leave the department
    • Going to garage was useful
    • Inform Nurse in Charge and Consultant
  2. Dynamic risk assessment
    • Performed by nursing/medical staff while outside
  3. Decontaminate
  4. Return to ED

If you haven’t seen the Initial Operational Response (IOR) training video please watch it.

The patient can then be thoroughly assesses, to identify the substance involved (this may involve witnesses, police info and symptomatology), and treated appropriately.

Police should be informed of the incident for several reasons: 1. Public safety, 2. To collect the evidence and possible find out what it was for you. (if this is not a criminal act Public health England can advise on return/disposal of personal effects)

Inform Manager On-Call of incident as it may disrupt the functioning of ED and can provide support.

 

Patient symptom-free and substance unknown

In our recent case Public Health England advised

  • 4-6hr observation
  • Discharge with advice:
    • “if developing symptoms to return to the ED via ambulance but the patient must be aware that they must inform 999 of the original exposure.”

Resourses

Methaemoglobinaemia

Q: Why are Smurf’s Blue? 

A: Methaemoglobin (MetHb) of course!

– MetHb is produced by oxidisation of the Iron in Haemoglobin (Hb) from Fe2+ to Fe3+

– Fe3+ prevents Hb carrying oxygen (thus produces symptoms of hypoxia)

– Often due to chemical ingestion, but may also be genetic

– Treated with Methyl Blue & supportive measures

Read more

Concealed Illicit Drugs

Background

Those suspected of concealing illicit drugs often present near ports and borders however they can present to any ED or be brought in by the police.

Body Packers – Swallow large quantities of well packaged drugs to smuggle them into countries or institutions.  These are often well manufactured with a low risk of rupture but the potential for serious toxicity if rupture occurs.

Body Stuffers – Swallow small quantities of poorly packaged illicit substances often at the point of arrest to conceal them. These have a much high risk of package rupture but involve smaller quantities of substances.

 

Investigations

Authorisation for an intimate search or radiological investigation must come from an inspector or higher with written consent from the patient.

Intimate searches must be carried out by a police surgeon but require immediately available resuscitation facilities therefore may be conducted in the ED. ED physicians should not handle the drugs at any time.

AXR or low dose CT scanning can be used to detect concealed packages in Body Packers.

 

General Management

Try to obtain a history of what and how much has been concealed

Look for toxidromes suggestive of package leak –

  • Cocaine: Tachycardia, hypertension, agitation, diaphoresis, dilated pupils, hyperpyrexia, seizures, chest pain, arrhythmias and paranoia.
  • Heroin: pinpoint pupils, respiratory depression, decreased mental state, decreased bowel sounds
  • Amphetamines : – Nausea, Vomiting, Dilated Pupils, Tachycardia, Hypertensions, Sweating, Convulsions and the development of non-cardiogenic pulmonary oedema

ECG

Body Stuffers should be observed for signs of toxicity for a minimum 6 hours, consider activated Charcoal

Body Packers with positive imaging who are asymptomatic can be discharged back to police custody for monitoring. Bowel preparation such as Cleanprep or movicol can be used.

Toxidromes should be treated as per toxbase guidelines Toxbase

Body Packers with signs of cocaine or amphetamine toxicity or signs of obstruction/ileus require urgent surgical intervention.

Body packers with signs of Heroin toxicity should be treated with Naloxone infusion as per toxbase guidelines

 

Algorithms

 

 

Full RCEM Guide