Septic shock — central venous access and the arterial line

(a) Site choice and preparation, including the coagulopathy (4 marks).

• Site — the right internal jugular vein under ultrasound guidance. Rationale: it is compressible (unlike the subclavian), the right side offers a straight path to the superior vena cava, the apex of the lung is lower on the right (lower pneumothorax risk), and ultrasound reduces the number of attempts, the failure rate and the arterial puncture rate compared with the landmark technique.
• The coagulopathy governs site selection. The INR of 2.8 is a relative contraindication to the subclavian route, because the subclavian vessels are not compressible and a bleeding complication there cannot be controlled by direct pressure. The internal jugular and the femoral veins are compressible, and ultrasound-guided internal jugular cannulation is sufficiently safe in the patient with an INR in this range that the line need not be delayed — the urgency of septic shock with refractory hypotension overrides the elective correction threshold. (The femoral is an acceptable alternative if the upper-body approach is unsuitable.)
• Preparation. Full sterile barrier (cap, mask, sterile gown and gloves, full body drape) — the cornerstone of CLABSI prevention. Confirm the ultrasound images the vein before draping. Position 15 to 30 degrees head-down (Trendelenburg) to distend the vein and reduce the air-embolism risk, head turned 30 to 45 degrees to the left. Continuous ECG (the guidewire can provoke atrial ectopy), pulse oximetry and blood pressure monitoring. Local anaesthesia with 1 per cent lidocaine (maximum 3 mg per kg plain).

(b) Ultrasound-guided Seldinger technique for the right internal jugular (6 marks).

^[5]1. Scout — covered linear probe transverse at the apex of the sternocleidomastoid triangle; identify the compressible, thin-walled internal jugular vein lateral to the round, pulsatile, non-compressible carotid; confirm compressibility and patency. 2. Anaesthetise — infiltrate 1 per cent lidocaine subcutaneously and along the tract, aspirating to avoid intravascular injection. 3. Cannulate under ultrasound — advance the 18-gauge introducer needle attached to a syringe, in-plane, watching the needle tip enter the vein lumen; aspirate dark, non-pulsatile venous blood to confirm. 4. Pass the J-tipped guidewire through the needle; advance smoothly with no resistance (never advance against resistance — withdraw slightly and reorient); watch the ECG for ectopy and withdraw 1 to 2 cm if the wire irritates the right atrium. 5. Remove the needle (wire always controlled in one hand); nick the skin with a number 11 blade; pass the dilator over the wire with a controlled rotating motion to create the tract. 6. Remove the dilator; pass the catheter over the wire to a measured depth (right internal jugular about 12 to 15 cm to the cavoatrial junction); remove the wire; aspirate and flush all lumens; secure; confirm with ultrasound and a post-procedure chest X-ray (tip at the cavoatrial junction, exclude pneumothorax).

^[5](c) Complications and the air-embolism rescue (3 marks).

• Immediate mechanical — pneumothorax (highest subclavian, lower internal jugular, zero femoral; excluded on the post-procedure chest X-ray), arterial puncture (carotid; with the finder needle withdraw and press 5 to 10 minutes; with the large-bore catheter leave it in and call vascular or interventional radiology), haematoma, guidewire-induced arrhythmia, the lost guidewire.
• Infectious — central-line-associated bloodstream infection (CLABSI), prevented by the bundle: hand hygiene, full sterile barrier, chlorhexidine skin preparation, femoral avoided where possible, daily review and early removal.
• Delayed — venous thrombosis, catheter migration, catheter fracture and embolisation.
• Venous air embolism rescue — at the first sign (sudden cough, desaturation, mill-wheel murmur, cardiovascular collapse): place the patient head-down in the left lateral position to trap the air in the right atrium, give 100 per cent oxygen, aspirate the air through the central line if it is in the right heart, commence cardiopulmonary resuscitation if arrest occurs, and consider hyperbaric therapy for neurologic sequelae.

^[5](d) Radial arterial line and the test that precedes it (2 marks).

• Modified Allen test — patient clenches the fist; operator compresses both the radial and the ulnar arteries until the hand blanches; patient opens the hand; operator releases the ulnar artery. Return of palm colour within 5 to 15 seconds indicates adequate ulnar collateral circulation and the radial artery may be cannulated; a delay beyond 15 seconds indicates insufficient collateral flow and the radial should not be used (choose the femoral or the other wrist after a normal test).
• Technique — wrist supinated and dorsiflexed over a rolled towel; ultrasound-guided 20-gauge over-needle cannula at the wrist; flashback of pulsatile blood; thread and secure; attach the transducer set, zero at the level of the heart.