Question 4 – Redback spider A 22-year-old man presents with a 2-hour history of increasing R forearm pain after working in his garden. He tells you there are "lots of spiders around" and you suspect a redback spider bite.

Sweating - local or generalised, may be profuse Piloerection N&V a) List 3 other symptoms or signs you would look for to confirm the diagnosis (3 marks)   Intense pain radiating up the arm proximally, then spreading to shoulder/chest/abdo/back Sweating - local or generalised, may be profuse Piloerection N&V Mild hypertension Tender lymphadenopathy Needed to mention symptoms that help make the diagnosis Most useful symptom is pattern of pain - needed to mention to get full marks. Common answer - “localised” sweating but often generalised Erythema commonly mentioned – usually mild, if present. Non-specific systemic effects such as nausea, vomiting, headache, malaise and lethargy alone (without pain description) not that useful to make diagnosis. How to mark if >3 signs mentioned?

b) List 2 medications you would give as a priority, include dosage (2 marks).  Any of: Paracetamol 1g, Ibuprofen 400mg, Oxycodone 10mg. Morphine/fentanyl, titrated to response Other - ADT, ondansetron - doesn't address main symptoms, not a priority Morphine - titrated to conscious state or RR?!?

c) What three pieces of information regarding antivenom use in this man, would you explain to the registrar who is looking after this patient (3 marks) Recent RCT (RAVE II) showed no significant clinical benefit of AV over placebo. Anecdotal clinical improvement seen by toxicologists Could consider if ongoing severe symptoms with unsatisfactory response to adequate doses of IV opioid analgesia Necessary to have discussion with patient re. questionable benefit of treatment vs risk of allergy and serum sickness.     Dose is 2 ampoules diluted in 100mL normal saline over 20min intravenously.     RAVE study – im and iv equivalent effect (or lack of!) Anaphylaxis/serum sickness – technically correct but better answers For full marks – must mention RAVE 2

List the most important early complication of antivenom administration (1 mark)  Allergy or anaphylaxis   List the most important delayed complication of antivenom administration (1 mark) Serum sickness List 2 symptoms of this delayed complication (2 marks) Fever Rash Arthralgia Myalgia