Paediatric venepuncture and peripheral intravenous access — formative SAQs

SAQ 1 (10)

A 14-month-old, 10 kg child is brought to the emergency department with gastroenteritis and moderate dehydration, and requires a peripheral cannula for rehydration. [7] [9]

1. State the cannula gauge you would prepare and your preferred site order, giving the reason for starting distally on the hand. (4) [6]
2. Outline the comfort bundle you would apply, naming each topical agent with its correct lead time and the role of oral sucrose. (4) [7] [10]
3. Describe how you would confirm correct cannula placement and state the rule on the number of attempts. (2) [6]

Model answer

Gauge and site. For a 14-month-old, a 22G (blue) cannula is the most appropriate starting gauge (24G for neonate and infant, 22G for infant and small child, 20G for the older child). The preferred site order is the dorsal hand veins first, then the antecubital fossa, the forearm cephalic vein, and finally the great saphenous vein at the ankle. Starting distally on the dorsum of the non-dominant hand is preferred because the veins are superficial and easy to secure, and a distal site leaves the more proximal sites available if the first attempt fails. The principle is to use the smallest cannula (largest gauge number) that delivers the therapy. [6]

Comfort bundle. Apply topical anaesthesia at the correct lead time — EMLA (lidocaine and prilocaine) about 60 minutes before, Ametop (tetracaine 4 per cent) about 30 to 45 minutes, or LMX4 (liposomal lidocaine 4 per cent) about 30 minutes — and occlude it with a dressing. Give oral sucrose at about 1 to 2 millilitres roughly two minutes before the procedure in this infant. Deploy age-appropriate distraction, comfort positioning on a parent's lap, and a single calm operator. [7] [10]

Confirmation and attempt rule. Confirm placement with a free flashback, an easy saline flush with no resistance and no swelling, and a blood return. The rule on attempts is that no operator should make more than two attempts before calling a more senior clinician; the difficult-access child is the indication for ultrasound-guided peripheral access. [6]

SAQ 2 (10)

A 3-year-old with septic shock has had two failed blind peripheral cannulation attempts and still has no visible surface veins, but has a pulse and a blood pressure. [1] [2]

1. Outline your next steps in obtaining access, including the role of ultrasound-guided peripheral cannulation and when you would move to intraosseous access. (4) [1] [2]
2. Describe the short-axis, out-of-plane ultrasound technique for peripheral cannulation and the sign that distinguishes a vein from an artery. (3) [1]
3. Explain why peripheral access is both most urgent and least likely to succeed in the shocked child, and how that should change your plan. (3) [2]

Model answer

Next steps. After two failed blind attempts, stop and call the most senior available clinician. Bring ultrasound and perform ultrasound-guided peripheral cannulation, which raises first-attempt success in the difficult-access child. Keep intraosseous access ready. If ultrasound is not fruitful promptly, or the child deteriorates into arrest, move to intraosseous access; the APLS rule is to move to intraosseous access within about 90 seconds of failed peripheral attempts in an emergency, or immediately as the first route in a shocked child with no obvious vein. Never let a hunt for a peripheral line delay resuscitation. [1] [2]

Ultrasound technique. Use a linear high-frequency probe. Identify a compressible anechoic vein in the short axis, centre it under the probe marker, insert the cannula out-of-plane advancing in small increments, and watch the needle tip tent the vessel wall then drop into the lumen with a flash. Confirm with an easy saline flush and no swelling. The vein is compressible and non-pulsatile; the artery is non-compressible and pulsatile. Compressibility is the single most useful sign. [1]

Urgency versus success. Peripheral access is most urgent in shock because the child needs fluids and vasoactive drugs immediately, yet it is least likely to succeed because peripheral vasoconstriction has hidden the veins. This mismatch is the reason to go to ultrasound early, keep intraosseous access ready, and place the largest cannula the vein allows so a bolus runs fast — and never to persist blindly while resuscitation stalls. [2]