DOH Cardiac Perfusionist oral exam prep

Knowledge: Air pumped into the arterial line goes straight to the aorta and the cerebral and coronary circulations, causing stroke, myocardial ischaemia and death. With a roller pump, an empty reservoir lets the pump drive air forward at full flow, which is why a level sensor linked to the pump is a basic safety requirement. The classic response, described by Mills and Ochsner, is to stop the pump, clamp the lines, de-air the circuit and the patient, and use retrograde perfusion through the superior vena cava to flush air out of the cerebral vessels. Hypothermia lowers cerebral metabolic demand, and hyperbaric oxygen may help later if available.

Management: I would stop the arterial pump at once, call 'air in the arterial line, stop', and clamp the arterial and venous lines. The surgeon places the patient in steep head-down position, and the aortic cannula is removed or opened so air can be vented from the aorta and arterial line. I would de-air and refill the circuit, re-prime the arterial line and filter, and restore the level. Retrograde perfusion of the superior vena cava with cold oxygenated blood is then run, as the surgeon directs, until no more air comes from the aortic root. Antegrade bypass then resumes with deeper cooling and adequate perfusion pressure,. After the case the patient needs ICU neurological assessment and possible hyperbaric referral.

Ethics and communication: I would record exact times, flows, temperatures and actions, and keep the circuit for inspection. The disabled level sensor is a serious incident that I report through the facility system and review honestly. The family should receive open disclosure from the surgeon with perfusion input, in line with Federal Decree-Law No. 4 of 2016 on Medical Liability. Pre-bypass checklists confirming that safety devices are active should be reinforced.

Reference: Mills NL, Ochsner JL, Massive air embolism during cardiopulmonary bypass (J Thorac Cardiovasc Surg 1980); Cardiopulmonary Bypass and Mechanical Support: Principles and Practice (5th ed, 2025)

Knowledge: Heparin works by binding antithrombin, so prolonged preoperative heparin therapy, which depletes antithrombin, is a common cause of heparin resistance. Other causes include high platelet counts, raised factor VIII and fibrinogen, sepsis, and errors such as heparin given into a line that did not deliver it. The STS/SCA/AmSECT guideline states that it is reasonable to keep the ACT above 480 seconds during bypass, and weight-based heparin dosing is reasonable for the initial dose. Bypass with an inadequate ACT risks clotting of the oxygenator and circuit, which is catastrophic. Treatment options are further heparin, antithrombin concentrate, or fresh frozen plasma to supply antithrombin.

Management: I would tell the surgeon clearly that we cannot go on bypass at this ACT and that I will not start bypass until anticoagulation is adequate. I would check the basics first: confirm the heparin was given into a running central line, check the vial and dose, repeat the ACT on a fresh sample, and check the analyser's quality control. I would agree with the anaesthetist on a further heparin dose, and if the ACT remains low, antithrombin concentrate or fresh frozen plasma, which the anaesthetist prescribes. Heparin is also in my prime as per protocol. I would repeat the ACT after each step and only start bypass once the target is reached, then check it every 20 to 30 minutes. Heparin-induced thrombocytopenia should be excluded if platelets have fallen.

Ethics and communication: Holding firm when a surgeon is impatient is a core safety duty, and I would state the risk calmly and factually. Every dose, time and ACT is documented, and if pressure to proceed unsafely continued I would escalate to the senior anaesthetist and perfusion lead. Use of plasma products requires the patient's consent for blood products, which the team confirms.

Reference: Shore-Lesserson L et al, STS/SCA/AmSECT Clinical Practice Guidelines: Anticoagulation During Cardiopulmonary Bypass (Ann Thorac Surg 2018); 2024 EACTS/EACTAIC/EBCP Guidelines on cardiopulmonary bypass in adult cardiac surgery (Wahba A et al, Eur J Cardiothorac Surg 2025)

Knowledge: Poor oxygen and carbon dioxide transfer with a rising pressure drop suggests clot or fibrin building up in the oxygenator, even with an adequate ACT. Other causes of falling PaO2 must be excluded first because they are quicker to fix: a disconnected or kinked gas line, blender or flowmeter failure, an empty gas supply, a sampling error, and a wet or leaking membrane with plasma leak, which shows as foam at the exhaust. If transfer cannot be restored, oxygenator replacement is needed. A rising pressure drop also risks high line pressure and haemolysis. Cooling lowers oxygen demand and gives some protection during a short stop in flow.

Management: I would immediately check the gas line from wall to oxygenator, the blender, the flowmeter and the exhaust port, and send a repeat blood gas. I would inform the surgeon and anaesthetist early, and ask a second perfusionist to come and prime a new oxygenator. If the gas supply is sound and exchange keeps falling, we would plan a change-out: lower the temperature further if agreed, reduce flow briefly, then stop the pump with lines clamped and replace the oxygenator with a rehearsed cut-and-replace technique, or a parallel oxygenator method if the circuit allows. I would de-air carefully, restart flow, confirm the blood gas, and check the ACT and the line pressures. The failed oxygenator is kept for analysis.

Ethics and communication: I would document the trend, the checks, the times of stopped flow and the outcome. The event is reported through the facility system and the device is reported to the manufacturer and the relevant regulator in line with facility policy on medical device incidents. The surgeon leads disclosure to the family if the event caused harm.

Reference: Cardiopulmonary Bypass and Mechanical Support: Principles and Practice (5th ed, 2025); 2024 EACTS/EACTAIC/EBCP Guidelines on cardiopulmonary bypass in adult cardiac surgery (Wahba A et al, Eur J Cardiothorac Surg 2025)

Knowledge: In femoral venoarterial ECMO, oxygenated blood flows retrograde up the aorta. When the heart recovers and ejects, blood from the left ventricle meets the ECMO flow somewhere in the aorta. If the lungs are not oxygenating, because of pulmonary oedema, the left ventricle ejects poorly oxygenated blood into the coronary arteries and the vessels of the head and right arm. This is differential hypoxaemia. The right radial artery best reflects what the brain and heart receive, which is why it is the preferred site for arterial monitoring. A good post-oxygenator gas shows the oxygenator is working. Left ventricular distension and pulmonary oedema are linked problems in this setting.

Management: I would confirm the sample site and repeat the right radial and post-oxygenator gases, check the circuit and oxygenator, and inform the ECMO physician at once. Options the physician will consider include ventilator changes with more PEEP and oxygen to improve native lung function, a modest increase in ECMO flow, and treating pulmonary oedema with diuresis or ultrafiltration. If hypoxaemia persists, the circuit may be reconfigured by adding a jugular return cannula to make a venoarterial-venous circuit, or the cannulation strategy changed. I would prepare the components and priming for that change. I would monitor right radial gases, cerebral oximetry, pulse pressure and limb perfusion closely and document trends.

Ethics and communication: The family should get regular honest updates from the physician about the course and the limits of ECMO, which is a bridge and not a cure. I work within my role, raising the alarm and offering technical options, while decisions on strategy belong to the ECMO physician. Clear handover at every shift change is essential for safety.

Reference: Lorusso R et al, ELSO Interim Guidelines for Venoarterial Extracorporeal Membrane Oxygenation in Adult Cardiac Patients (ASAIO J 2021); Extracorporeal Life Support: The ELSO Red Book (6th ed, 2022)

Knowledge: A centrifugal pump is not occlusive, so when it stops, blood flows backwards from the aorta through the pump towards the reservoir. This drains the patient, can pull air in around the aortic cannula and leaves the brain without perfusion. The first action is therefore to clamp the arterial line. Recovery depends on moving the pump head to a backup drive or a manual hand crank and generating enough speed to produce forward flow before releasing the clamp. With a roller pump the response is different: the pump is occlusive and can be hand-cranked directly, with someone counting turns against the flow. Every perfusionist should know the backup equipment and practise it.

Management: I would clamp the arterial line at once and call 'pump failure' to the surgeon and anaesthetist, so the surgeon stops manipulating the heart and the anaesthetist supports pressure. I would move the pump head to the backup drive or hand crank, bring it to a speed that gives forward flow, then release the clamp and confirm the flow reading and arterial pressure. I would ask for a second perfusionist to help, manage the venous reservoir level by hand, and watch for air. If the console cannot be restarted, I would continue manually or change to a spare console, keeping bypass until the team can safely separate. I would check the oxygenator, temperature and ACT once stable.

Ethics and communication: I would document the failure time, actions and duration of low flow, and keep the console for biomedical engineering review. The event is reported through the facility incident system and to the manufacturer under device reporting rules in facility policy. The surgeon and anaesthetist are told the duration of low flow, so the patient's neurological state can be assessed and the family informed honestly.

Reference: Cardiopulmonary Bypass and Mechanical Support: Principles and Practice (5th ed, 2025); AmSECT Standards and Guidelines for Perfusion Practice

Knowledge: A perfusionist controls the patient's circulation, gas exchange, temperature and anticoagulation, so impairment from alcohol creates an immediate risk of death. Signs such as unsteadiness, errors and the smell of alcohol are enough to act on; it is not my role to prove intoxication. Professional codes and facility policies require staff to protect patients from an impaired colleague, and also to treat that colleague fairly, as impairment may reflect a health problem that needs support. The response should be proportionate: stop the immediate risk, report through the proper channel and avoid public accusations.

Management: I would speak to him privately and calmly, explain that he cannot run the pump today, and ask him to step away from the case. I would inform the chief perfusionist or head of department straight away, and the anaesthetist and surgeon that the case must be delayed until a fit perfusionist is available. I would not run a case alone if the department policy requires two perfusionists. I would make sure he does not drive home and that a senior colleague stays with him. I would write a factual note of what I saw and when, and leave further assessment, testing and occupational health referral to management under the facility policy.

Ethics and communication: My duty to the patient overrides his request for secrecy, but I would protect his dignity by sharing the information only with those who need it. Concern for his visa does not change the duty, though I can be kind and point him to support services. Reporting follows the facility policy and any regulatory requirement it sets out; I would not invent a separate route. If the patient asks why the case is delayed, the team gives an honest explanation without sharing the colleague's personal details.

Reference: AmSECT Standards and Guidelines for Perfusion Practice; Federal Decree-Law No. 4 of 2016 on Medical Liability (UAE)