Question 9

College answer

Aim: To explore candidate understanding of the assessment and management of a toxicology patient with a threatened airway in the first 48 hours.

Key sources include: Paper 2000.1 Q6 concentrates on complications of corrosive ingestions. CanMEDS medical expert.

Discussion: Candidates who were specific in their response and answered the question from a practical perspective did well. The question asked for “your” assessment and management. Candidates who provided specific recommendations for the threatened airway and toxidrome gained more marks than candidates who listed all the potential strategies but did not recommend any particular course of action.

Candidates should note that although referral with other specialities is an integral part of ICU practice, to demonstrate a transitional fellow approach it is important to know and detail the rationale for the referral and desired outcome. Candidates who were explicit, specific, logical and with coherent synthesis were given more marks than answers which were vague, non-committal and potentially placed patient safely at risk. For example, a discussion of caution/avoidance in the use of nasogastric tubes or placement with aid of a gastroscope demonstrated that the candidate was aware of the high risk of perforation of hollow organs with mediastinal soiling.

Answers that were superficial and generic or incorrect were given less marks. For example, answers which focused on whole bowel irrigation or contact risk to staff were incorrect.

Candidates should note the glossary of terms for the definitions and subheadings of assessment and management which will help the candidate focus and give depth to their answer. Use of these headings to guide specific details contextualised to the clinical case provided will allow the candidate to demonstrate competency in this area and gain marks. The use of other templates such as DR RSI DEAD are perfectly acceptable however candidates answer in the R=risk management section was often lacking important historical details.

Discussion

It is a fair statement, that when one is asked for their management strategy, one should offer their own management strategy instead of a range of noncommittal possibilities. But what would that even look like? The author offers the following suggested model answer without flattering himself (as even under normal circumstances his plans are never "explicit, specific, logical and with coherent synthesis"). 

• Resuscitation
  • This patient requires intubation for a variety of reasons:
    • The airway already appears compromised from the history and examination findings as given in the stem; for example, even leaving aside the stridor, the patient is clearly unable to manage his own secretions
    • Even if it wasn't,  it would be best to secure an airway while it is easy, anticipating that it could become more difficult in the immediate future with progressive swelling
    • Intubation is anyway going to be necessary to facilitate some of the invasive investigations (eg. endoscopy)
  • IV access and fluid resuscitation
• Risk asssessment
  • ​​​​​​​Agent: most "drain cleaner" is alkaline, and the most corrosive things people usually have access to in their home will usually be some kind of alkali, but local homeware department stores sometimes stock surprisingly hardcore acids. It would be lovely if the emergency services personnel have brought the canister of the agent with them when they collected the patient.
  • Dose: work out how much they drank
  • Time: how long ago did they drink it?
  • Patient factors: while this guy is still talking, some background medical history would be relevant.
  • Recent features: vomiting, unconsciousness, shortness of breath, any co-ingested agents (alcohol?) etc
• Supportive care and monitoring
  • ​​​​​​​Mechanical ventilation, with attention to the resp rate (would need to be a bit higher to accommodate worsening acidosis)
  • Invasive monitoring and central venous access (considering the need for TPN in the future will be high, may as well use a line that has an abundance of lumens)
  • Fluid resuscitation to account for third space losses (consider this analogous to the resuscitation of burns)
  • Antiemetics (vomiting results in re-exposure to the agent)
  • PPI (to prevent further damage to the mucosa)
  • Analgesia (these injuries are usually extremely painful)
  • Broad-spectrum antibiotics, including antifungal cover, until perforation is excluded
• Investigations
  • ABG: looking for lactic acidosis of shock
  • ​​​​​​​EUC, CMP: looking for hyperchloremia and renal failure
  • FBC, coags - looking for bleeding (GI perforation) and DIC
  • Serum osmolality
  • ECG
  • CXR: looking for free gas (mediastinal or intraabdominal organs could have perforated)
  • CT chest and abdomen (for the same reason)
  • Endoscopy - early - to explore the extent of the oesophageal injury and to place an NG tube safely, while the oesophagus is still not too friable. Later, endoscopy becomes impossible.
  • Paracetamol level: because always.
• Decontamination
  • ​​​​​​​Mostly decontamination is impossible, as alkline ingestion will be limited by the neutralising effects of gastric acid
  • Specific corrosive agents which would benefit from decontamination include zinc chloride (ZnCl₂) and mercuric chloride (HgCl₂). The corrosive damage is trivial compared to the systemic toxicity. Activated charcoal is the agent of choice
• Enhanced elimination
  • ​​​​​​​No additional enhanced elimination techniques are needed, except for agents with significant systemic toxicity as mentioned above.
• Antidotes
  • ​​​​​​​Gastric acid neutralises alkaline ingestables; for acidic ones, alkaline antacids administration is theoretically possible, but most neutralisation reactions are exothermic and could exacerbate the burn. Moreover the products of neutralisation are themselves often ridiculously toxic.
• Disposition
  • ​​​​​​​ICU, or the operating theatre if a perforated viscus needs to be repaired or endoscopy is organised.

b) was a hugely lopsided part of the question, asking for something with potentially a massive host of points, but allocating only 10% of the marks to it. Question 6 from the first paper of 2000, referenced in the examiner comments, was all about the complications of corrosive ingestion, but mainly focused on the immediate complications. 

Chronic complications include:

• Chronic facial and airway scarring
• Pulmonary fibrosis and bronchiectasis from corrosive aspiration
• Oesophageal stricture
• Sequelae of salvage surgery (eg. gastrectomy)
• Gastric outlet obstruction
• Short gut (where large resection was required)
• Malnutrition (due to same, or due to chronic swallowing dysfunction)
• If mediastinitis develops:
  • Chronic empyema
  • Chronic fungal infections
  • Sequelae of mediastinal cleanup surgery, eg. chronic pain from thoracotomies, phrenic nerve injury, thoracic duct disruption, restrictive pericarditis