Regarding a toddler presenting with a history of possible ingestion of a button battery, which ONE of the following statements is TRUE?
Answer: A: Button batteries lodged in the oesophagus, nose and the ears should be removed urgently, ideally within 6 hours. A button battery >1.5 cm diameter is likely to become lodged in the oesophagus of a young child when ingested. If lodged for sufficient time it can cause severe local burns to the mucosa and acute perforation and haemorrhage.
Most children are asymptomatic at presentation or they may develop symptoms related to oesophageal burns (e.g. pain and dysphagia) early. In some the symptoms can be delayed for several days. If suspicious of ingestion of a button battery, all children should be assessed with plain chest and abdominal films to confirm or exclude the diagnosis and to locate the battery. If it is lodged above the diaphragm, the child should be referred for urgent endoscopic removal and inspection of the oesophagus for injury to be done within 6 hours from the time of ingestion. Carbonated drinks should not be tried. An asymptomatic child with a button battery located below the diaphragm but within the stomach can be managed expectantly. Plain X-ray should be repeated in 24 hours to ensure the battery has passed the pylorus. If it has not passed the pylorus, especially if it is a larger battery, it may require endoscopic removal. Once the battery passes the pylorus it is less likely to cause complications and close follow up with repeat X-ray is not generally indicated.
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A 4-year-old child presents to the ED following an accidental overdose of a liquid iron preparation. He complains of abdominal pain and vomiting. He is awake and alert. He has mild tachycardia but his other vital signs are normal at presentation.
When assessing for systemic iron toxicity, which ONE of the following is LEAST important?
Answer: B: Classically, five overlapping stages of iron toxicity are described. However, clinically, iron toxicity can be described as gastrointestinal toxicity (mainly due to direct corrosive effects) and systemic toxicity.
The dose of elemental iron accidentally ingested by young children is often not large enough to cause systemic toxicity. They frequently present asymptomatically. A further small number may present with gastrointestinal symptoms. It is important to calculate the possible amount of elemental iron ingested.
In addition to calculating the possible ingested elemental iron dose, abdominal X-ray may help to quantify the ingested amount, especially when the child has taken iron tablets, which are usually radioopaque. Systemic toxicity is unlikely to occur in the absence of gastrointestinal toxicity (e.g. vomiting, diarrhoea, abdominal pain). In the assessment of evidence for systemic toxicity, the following can be considered in the context of child’s clinical symptoms:
Iron toxicity occurs when serum iron exceeds the total iron binding capacity (TIBC) by saturating transferrin and ferritin. However, TIBC measurements are not valuable in the assessment of systemic toxicity.
Regarding drug- or toxin-induced methaemoglobinaemia, which ONE of the following statements is TRUE?
Answer: A: Acquired methaemoglobinaemia is a well-recognized toxicity syndrome secondary to accidental or deliberate exposure to drugs and toxins that act as oxidizers of iron in the haem moiety of haemoglobin from the ferrous (Fe2+ ) to ferric (Fe3+ ) form. Generally local anaesthetics, nitrates and nitrites, dapsone, rifampicin and sulfa drugs and some Asian food additives are implicated. Methaemoglobinaemia can be caused by recreational exposure to amyl nitrite and other alkyl nitrites contained in air fresheners and video head cleaners (‘poppers’). Methaemoglobin is unable to bind oxygen therefore the oxygen-carrying capacity of the blood is significantly reduced with left shifting of oxygen dissociation curve. This results in tissue hypoxia.
In the ED, methaemoglobinaemia is a clinical diagnosis based on a suggestive clinical history and the examination findings, supported by arterial blood gas (ABG) results. A grey-blue discoloration of the skin is typical while blood drawn for investigations shows a chocolate-brown discoloration. However, this blood does not become red with exposure to oxygen or air.
Methaemoglobin interferes with pulse oximetry readings and these should be interpreted with caution as the pulse oximeter will report a falsely elevated value while patient remains severely hypoxic. Methaemoglobin is able to absorb light at both 660 and 940 nm wavelengths, similar to oxyhaemoglobin. This false absorption of light by methaemoglobin plateaus oxygen saturation on pulse oxymeter around 85%. Therefore, the patient may be severely hypoxic with severe methaemoglobinaemia but pulse oximetry may remain around 85%.
Similarly, the calculated arterial oxygen saturation (SaO2 ) obtained by a blood gas analyzer will produce a falsely elevated result as the blood gas analyzer uses the partial pressure of oxygen for the calculation. The partial pressure of oxygen is a measure of dissolved, not bound oxygen, and remains normal. In summary, the SaO2 obtained with ABG remains very high and pulse oxymetry reading may remain at 85% in severe methaemoglobaemia creating an increased oxygen saturation gap.
Definitive identification of methaemoglobin requires co-oximetry, which is capable of differentiating between oxyhemoglobin, deoxyhemoglobin, carboxyhemoglobin and methemoglobin.
Methylene blue is the recommended antidote that acts as a reducing agent. NAC has been investigated for use as a reducing agent in methaemoglobinaemia but has given conflicting results. Exchange transfusion and hyperbaric oxygen as other potentially beneficial treatment options may be considered in lifethreatening toxicity.
All of the following investigations can be used to investigate ‘body packers’ EXCEPT:
Answer: A: Body packers (‘swallowers’ or ‘mules’) are people who illegally carry drugs, mostly cocaine, heroin, amphetamines and MDMA, concealed within their bodies. The packets are made of various materials, but most often are from condoms, balloons and plastic. A single person may carry up to 100 small packets containing life-threatening quantities of the drug. The body packer swallows these packets and uses constipating agents to slow the transit time of the packets through the intestine. After entering the country of destination, body packers use laxatives, cathartics or enemas to help pass their cargo rectally. Body packers usually present to EDs with druginduced toxic effects (due to rupture of packets releasing a potentially lethal quantity of drugs), intestinal obstruction or for medical assessment after detention or arrest. Contrast CT scan of the abdomen is considered the investigation of choice in suspected cases. Urine toxicology, if positive, indicates the need for further investigation. Plain abdominal X-ray may indicate the presence of multiple packets in the intestine and is reported to be sensitive. However, neither negative urine toxicology nor abdominal X-ray can exclude the diagnosis.
Which ONE of the following is likely to be the EARLIEST indication of systemic envenoming in a patient who has been bitten by a brown snake?
Answer: D: One of the earliest manifestations of envenoming in a patient bitten by a brown snake is early collapse or syncope, often with subsequent recovery until the onset of other features. A positive SVDK test for brown snake venom does not indicate systemic envenoming; however, this helps in choosing the correct monovalent antivenom if the patient develops clinical features of envenoming. Although brown snake venom contains a presynaptic neurotoxin, significant neurological manifestations do not occur when envenomed.
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