Poisoning by a mercury thermometer
aka Toxicology Conundrum 002
Your next patient is an 80 year old man suffering from Alzheimer’s dementia. He was brought into the ED by his wife and daughter who are his care-givers. He had a recent catheter-associated urinary tract infection and his daughter was checking his temperature orally with a mercury thermometer 30 minutes previously.
Unfortunately he bit down on the thermometer. The thermometer broke and some mercury spilled onto the floor. The daughter believes that the amount spilled is less than 1 mL. The patient is asymptomatic.
Questions
Q1. What is the risk assessment for the patient in this case?
Answer and interpretation
The patient’s mercury exposure is benign.
Accidental oral or skin exposure to elemental mercury does not need medical assessment unless the patient is symptomatic. Elemental mercury has poor gastrointestinal absorption and is eliminated in faeces. The volume of mercury in a thermometer is very small.
However – other factors to consider:
- Increased absorption of elemental mercury may occur if the patient has an abnormal gastrointestinal mucosa, or delayed faecal elimination due to an ileus or a gastrointestinal perforation. There have been reports of mercury getting trapped in the appendix, but in the absence of appendicitis or features of toxicity no intervention is required.
- Vomiting of orally ingested elemental mercury may lead to aspiration. This is higher risk as aerosolized or vaporized elemental mercury is well absorbed from the respiratory tract.
Q2. Describe the investigations and management required for the patient.
Answer and interpretation
Decontamination:
- Remove contaminated clothing and discard in sealed plastic double-bag (do not put in a washing machine or dryer as they will become contaminated).
- Removal of mercury from the skin – remove all jewelry (mercury forms a gold amalgam) and wash with soap and water.
Assess for traumatic injury to the mouth from broken glass.
Assuming there is no injury, no further investigation or management is required.
X-ray may reveal mercury…
Q3. What is the risk assessment for the care-givers who live with the patient?
Answer and interpretation
If the elemental mercury is not adequately cleaned up there is the possibility of ongoing vaporization. However the volume of mercury in a household thermometer is so small that the risk of chronic mercury toxicity due to inhalation is probably negligible.
Q4. How should the spilled mercury be cleaned up?
Answer and interpretation
In Australia, the Local Government Environmental Health Officer can be contacted for advice about cleaning up spilled mercury. Amounts of elemental mercury greater than ~ 2 teaspoons should be dealt with by professionals.
Clean up advice:
- Clear the room of people and pets.
- Open windows and doors to ventilate the room.
- Turn off heating or cooling.
- Clean up as thoroughly as possible as ongoing release of vapour is a risk.
- The cleaner should remove jewelry (forms gold amalgam).
- Ideally remove and discard contaminated carpet or tiles.
- Suck up droplets with an eye dropper or similar device.
- Avoid brooms (breaks up droplets).
- Avoid vacuums (agitation and heating promotes vaporization) – if a vacuum cleaner has been used the tubing, filter and bag will need to be replaced. It is best discarded or decontaminated by a professional.
- Treat the remaining mercury (e.g. in cracks between tiles or on carpet) with a calcium polysulfide slurry (mix 1 part lime with 1 part powdered sulfur in water), leave overnight, and then vacuum.
- Place any residue in a sealed plastic bag and discard as per local authority requirements.
References
- Caravati EM, Erdman AR, Christianson G, et al. Elemental mercury exposure: an evidence-based consensus guideline for out-of-hospital management. Clinical Toxicology 2008 46(1):1-21. [Pubmed]
CLINICAL CASES
Toxicology Conundrum
Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.
After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.
He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE. He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.
His one great achievement is being the father of three amazing children.
On Twitter, he is @precordialthump.
| INTENSIVE | RAGE | Resuscitology | SMACC