Emergency CPB Initiation
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Direct answer
Cardiac arrest in the catheterisation laboratory, a massive pulmonary embolism, a hypothermic arrest needing active core rewarming, an iatrogenic catastrophe in an interventional suite — each is an indication for emergency initiation of cardiopulmonary bypass, where a pre-primed or rapidly primed circuit and percutaneous femoral cannulation (a 17-19 Fr arterial and 21-25 Fr multistage venous cannula by Seldinger technique under ultrasound and echo) restore circulation in single-digit minutes. Speed is bought with pre-made decisions: a stored crystalloid-primed rapid-deployment circuit, a rehearsed cannulation team, and acceptance that a heparinised prime, deepening anaesthesia and perfect haematocrit are luxuries of elective cases. Emergency bypass is elective bypass with the tolerances widened and the sequence compressed.
What you must remember
- Indications list: sudden arrest or collapse during interventions (ECPR), massive pulmonary embolism with obstructive shock, rewarming of severe hypothermia with arrest, trauma exsanguination in selected programmes, postinfarct rupture or severe ischaemia bridging to surgery.
- Cannulation by kit: percutaneous femoral artery 17-19 Fr and femoral vein 21-25 Fr multistage by Seldinger wire, position confirmed on echo or fluoroscopy where available; open cutdown when pulses are absent.
- The prime trade-off: clear crystalloid prime is accepted for speed; the resulting dilution and its consequences (haematocrit, platelets, oncotic pressure) are corrected after circulation is restored, not before.
- Anticoagulation in extremis: heparin 300-400 U/kg still given once flow is possible; brief no-heparin running on heparin-coated circuits is described in desperate scenarios but is a clot timer, not a plan — hedge and correct fast.
- Flow logic: flows rise as rewarming and reperfusion proceed; early hypothermic runs may be on lower flows, then full 2.2-2.4 L/min/m² indexed support.
- The emergency circuit: centrifugal-pump configurations, membrane oxygenator, minimal tubing length, kept assembled or rapidly assembled with a checklist card; the drill is rehearsed like a fire drill.
- Communication discipline survives compression: closed-loop commands, times called aloud, one person owning the wire and one the pump.
- Destination planning: emergency bypass is a bridge — to theatre, to ECMO configuration, to definitive repair; the perfusionist plans the transition while flow is being established.
Three minutes from arrest to flow
Script the scenario the way programmes rehearse it. In the catheterisation laboratory, a left main dissection drops the pressure to nothing; compressions start, and the call goes out — "crash pump, left femoral". The perfusionist drops the stored circuit into the console, confirms the prime is in date and de-aired by design, while the operator punctures the femoral artery and vein and feeds wires under compressions, echo confirming the venous wire in the right atrium. Heparin goes in the moment access exists. The arterial cannula seats; the venous drains; the pump turns. "On flow — two litres" — compressions stop because the circuit is the circulation now. The first ABG shows profound acidosis; ventilation and sweep are set high, the anaesthetist buffers, and the temperature line reads 34 and drifting. Six minutes in, the patient has a perfusing circulation, a sternotomy is being prepped, and the record already reads like an anaesthetic chart from a war film — times, doses, flow, spoken commands. That compression of sequence into choreography is the entire discipline.
Where the exam probes
Theory papers ask "indications and technique of emergency cardiopulmonary bypass" and grade the technique half on logistics: what is pre-primed, what sizes the cannulae, how position is confirmed without fluoroscopy, and what compromises are acceptable in the first minutes. The viva trap is the heparin question — "can you run emergency bypass without heparin?" The trained answer: only for minutes, on biocompatible surfaces, with full heparinisation the moment the situation allows, because the circuit clots catastrophically at stagnant points and the oxygenator is the first casualty. The Indian context: rapid-deployment ECMO and crash-pump capability now exist in large tertiary centres and mobile retrieval programmes, and examiners increasingly frame the question as ECPR — cannulating during compressions — where the expected answer includes that flow target rises gradually and that femoral VA support is the default configuration. Candidates who describe only the sterile elective sequence lose the tempo marks.
Frequently asked questions
What are the principal indications for emergency initiation of bypass?
Catheterisation laboratory arrest (ECPR), massive pulmonary embolism with obstructive shock, arrest from severe hypothermia requiring core rewarming, and selected trauma or bridge-to-surgery scenarios.
Which vessels and sizes are used for percutaneous emergency cannulation?
Commonly a 17-19 Fr femoral arterial cannula and a 21-25 Fr multistage femoral venous cannula placed over a Seldinger wire, positions confirmed by echo or fluoroscopy where possible.
Can emergency bypass run without heparin?
Only briefly and only in extremis on biocompatible circuits — clotting begins within minutes, so full heparinisation is restored as soon as possible.
Why is a crystalloid prime accepted in emergencies?
Speed outweighs optimisation — dilution and its haematological consequences are accepted at initiation and corrected once circulation is established.
How does emergency bypass differ from planned ECMO?
The circuit and cannulation are similar, but emergency bypass is a resuscitative bridge aimed at a definitive operation, whereas ECMO is deliberately configured for days of support.