ABCP PBSE and CAPE: Perfusion Science and Clinical Decisions Study Guide

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During cross-clamping, systemic arterial oxygen saturation remains excellent but myocardial electrical activity returns. Explain why systemic oxygenation does not establish adequate coronary cardioplegia delivery, then review the selected route and evidence of myocardial protection with the team.

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After separation from bypass, a patient develops tachycardia with low diastolic pressure and rising ventricular filling pressure. Identify three changes that can reduce subendocardial perfusion despite a seemingly acceptable systolic arterial pressure.

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A diagram shows blood leaving the right ventricle for the pulmonary trunk. Name the intervening valve and explain why attaching mitral chordae to that valve would make the anatomical model incorrect.

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A patient on VV ECMO develops severe ventricular failure. Explain why improving extracorporeal gas exchange alone may fail to restore systemic perfusion when native cardiac output can no longer move blood through the circulation.

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Assume haemoglobin 10 g/dL, saturation 1.00 and PaO2 100 mmHg. Calculate CaO2 as 13.4 + 0.3 = 13.7 mL/dL, and identify the haemoglobin-bound component as the dominant contribution to total content.

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During full CPB with negligible native ejection, corrected arterial flow of 4 L/min and systemic CaO2 of 14 mL/dL give DO2 of 560 mL/min. By comparison, a VV circuit at 4 L/min with outlet-minus-inlet content of 5 mL/dL transfers 200 mL oxygen/min across the oxygenator; that is not the patient's total systemic DO2.

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A delivered flow of 4.8 L/min supports a patient with body surface area 2.0 m². Calculate a flow index of 2.4 L/min/m², then explain why haemoglobin and oxygen content remain necessary for judging oxygen delivery.

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After bypass initiation, arterial saturation remains 100% while haemoglobin falls from 12 to 8 g/dL. With unchanged flow and PaO2, identify reduced arterial oxygen content as the principal reason oxygen delivery has fallen.

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During rewarming, venous saturation falls while arterial saturation remains unchanged. Review rising metabolic demand, delivered flow and haemoglobin together, rather than treating the arterial oxygenation measurement as sufficient evidence that oxygen transport remains adequate.

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A patient has falling calculated delivery, falling venous saturation and rising lactate during bypass. Explain why their combined direction raises concern for supply limitation even though mean arterial pressure has been maintained pharmacologically.

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A patient warms while pump flow and haemoglobin remain fixed. Explain why venous oxygenation may change despite stable arterial saturation, considering both increasing tissue oxygen demand and the temperature dependence of haemoglobin oxygen binding.

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After verified heparin administration, anticoagulant response remains unexpectedly small and antithrombin activity is low. Explain the mechanism of poor responsiveness and why the team should evaluate the cofactor deficiency alongside the anticoagulation test.

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A clotting time changes little after heparin, but a second sample confirms substantial circulating heparin. Identify antithrombin activity and assay influences as useful next considerations after checking administration, sample integrity and testing-system function.

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An oxygenator develops a rising pressure gradient with visible clot despite subsequently adequate anticoagulation. Explain why achieving an anticoagulation target does not prove that the established obstruction will disappear or that circuit performance has recovered.

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A long bypass case includes several heparin administrations at different times. Explain why reversal planning should consider residual circulating heparin and an appropriate assessment method, rather than mechanically matching all heparin ever administered.

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Soon after protamine begins, systemic pressure falls abruptly while pulmonary artery pressure rises. The timing and simultaneous pulmonary pressure increase suggest a serious protamine-associated reaction. Stop administration, alert the surgical and anaesthesia team immediately, and begin respiratory and circulatory support while preparing for possible return to CPB. If pulmonary hypertension progresses to circulatory collapse, urgently coordinate re-anticoagulation and reinstitution of bypass. By comparison, an isolated mild pressure decrease without pulmonary hypertension or progressive instability may respond to pausing administration, haemodynamic support and reassessment of the administration rate; it does not automatically require CPB.

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Bleeding persists after repeated protamine, while a heparin-specific assessment shows no residual heparin. Explain why further empiric protamine is poorly justified and why platelet, coagulation-factor and surgical assessments become more informative.

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A patient receiving heparin develops a substantial platelet decline and a new limb thrombosis. Explain why the coexistence of thrombocytopenia and thrombosis supports consideration of immune platelet activation, then assess clinical probability rather than diagnosing HIT from either finding alone.

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Platelets decrease from 360 to 165 × 10⁹/L during heparin exposure. Calculate a 54.2% decline and assign two points for the thrombocytopenia component, despite the final count being near many laboratories' reference intervals. Complete the remaining 4Ts components before interpreting probability.

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Heparin begins with CPB on 1 October, with no exposure in the preceding 100 days. Platelets are 250 × 10⁹/L on 1 October, 110 on 3 October, 230 on 6 October and 95 on 9 October, when a new DVT is confirmed. The renewed fall is 58.7% from the recovery peak and occurs on day 8. If no alternative cause is evident, the four components each score two, giving a high-probability total of eight. This warrants prompt HIT management and diagnostic testing; it is not laboratory confirmation.

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An elective surgical patient has recovered platelets but a positive functional assay: classify this as subacute HIT A and consider deferral. A patient with recovered platelets, a negative functional assay and persistent immunoassay positivity has subacute HIT B, for which ASH supports selected limited intraoperative heparin exposure. Urgent active disease requires a separately planned strategy such as bivalirudin with appropriate monitoring.

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During bypass, haemodilution lowers haemoglobin and a pressure-supporting drug maintains arterial pressure. Explain why organ oxygen supply can remain inadequate unless actual delivered flow and arterial oxygen content are evaluated together.

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A patient on femoral VA ECMO has worsening pulmonary oedema, minimal pulsatility and a persistently closed aortic valve. Link the findings to inadequate left ventricular ejection and communicate the need for an unloading assessment.

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A sample has pH 7.28, PaCO2 30 mmHg and bicarbonate 14 mmol/L. Identify metabolic acidosis with a compensatory respiratory direction, then relate the result to perfusion, lactate and the patient's clinical condition.

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As bypass becomes colder and more diluted, ACT lengthens without additional heparin. Explain why this change cannot be interpreted automatically as an increase in circulating heparin and why assay context matters.

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A prolonged viscoelastic clotting result becomes substantially shorter with heparinase. Explain why that paired comparison supports residual heparin, while a similar prolongation in both channels would direct attention toward other haemostatic defects.

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Classify three illustrative statements: “An arterial air detector shall be used” expresses a standard; “The team should consider a recommended monitoring method” expresses a guideline; “When this alarm activates, the assigned clinician performs these specified actions” describes a protocol. During a handoff, communicate flow, temperature, anticoagulation results and a rising oxygenator gradient, then obtain acknowledgement of the unresolved issue and transfer of responsibility.

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A programme records four adverse events in 200 cases before an intervention and three in 100 afterward. Calculate rates of 2% and 3%, and explain why the lower event count does not demonstrate improvement.

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Pump speed is unchanged, but delivered flow falls as an arterial line becomes partially kinked. Explain why the pump cannot be assumed to maintain its earlier output and identify downstream resistance as the likely limitation.

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Increasing pump speed produces more inlet-line oscillation but little additional flow. Initially reduce excessive suction, then assess volume status, inspect the drainage pathway and evaluate cannula position before selecting fluid administration or cannula correction.

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At unchanged flow, pressure before an arterial cannula rises while patient arterial pressure remains stable. Inspect the connecting tubing and cannula pathway, using the pressure difference to identify resistance outside the patient's systemic circulation.

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Two hypothetical straight tubes have identical length and viscosity, but one has half the internal radius. Under ideal laminar assumptions, calculate sixteenfold resistance and explain why internal dimensions strongly influence equipment selection.

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At stable flow and temperature, pre-oxygenator pressure rises while post-oxygenator pressure remains similar. Identify an increasing transoxygenator gradient and assess device obstruction rather than attributing the entire change to systemic arterial pressure.

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A functioning oxygenator delivers nearly fully saturated outlet blood, but systemic oxygen delivery remains low because systemic blood flow is inadequate. Explain why increasing gas oxygen concentration alone will not correct the principal limitation.

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A filter purge line returns blood to the venous reservoir. Explain why the flow entering the filter may exceed flow reaching the patient and why the filter does not replace an arterial bubble detector.

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Before bypass, a level sensor is mounted above its intended operating position and the pump-interruption connection is inactive. Identify why visual presence of the device does not establish that low-volume protection is functional.

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During a planned centrifugal pump stop, arterial pressure remains higher than venous-side pressure. Explain why the circuit requires its designated reverse-flow prevention step and why zero revolutions per minute does not establish zero blood movement.

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Calculated oxygen delivery falls after haemodilution, while drainage can safely support more flow. Compare increasing delivered flow with other corrective options, and reassess delivery and extraction rather than responding solely to the haemoglobin value.

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Bladder temperature is 35°C, but arterial outlet blood is approaching 37°C. Explain why the slower body-site reading should not prompt further aggressive heating that would exceed the recommended arterial outlet limit.

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At an arterial outlet temperature of 32°C, the arterial-to-venous blood gradient is 7°C. Identify the excessive gradient under the cited rewarming recommendation and reduce thermal intensity while continuing to monitor outlet temperature and rewarming rate.

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A patient with important aortic regurgitation is receiving root cardioplegia, and the left ventricle begins to distend. Explain the delivery problem and why the team should reconsider the coronary delivery route and ventricular decompression.

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A small adult has a large crystalloid prime relative to estimated blood volume. Explain how autologous priming could reduce dilution, while identifying haemodynamic tolerance as a necessary condition for safely displacing that prime.

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After paediatric bypass, the team considers modified ultrafiltration for marked haemodilution. Explain its post-bypass timing and why blood pressure, filling and the selected flow pathway must be monitored while plasma water is removed.

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Assume patient blood volume 300 mL, initial haematocrit 40%, and 300 mL of cell-free prime, with no losses or other additions. Calculate a mixed haematocrit of 20% and recognise the substantial dilution.

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A neonatal blood prime has acceptable haematocrit but elevated potassium and low ionised calcium. Explain why red-cell concentration alone is insufficient evidence of readiness and why the electrolyte abnormalities should be addressed before connection.

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Two heparin vials contain the required active drug concentration, but one includes benzyl alcohol. For a premature neonate, identify the preservative-free formulation as the appropriate way to avoid that recognised excipient hazard.

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During infant cooling, CO2 is added to achieve temperature-corrected targets. Identify pH-stat and explain its cerebral vasodilator effect. Before interpreting the displayed values or changing management during rewarming, confirm the reporting temperature and the team's phase-specific strategy.

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A patient with severe lung failure has preserved cardiac output and receives venous drainage with venous return. Explain why VV support matches the principal physiological problem and why ongoing native cardiac function remains essential.

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A VV ECMO patient has stable oxygenation and blood flow but persistent hypercapnia. After confirming gas-path integrity, identify a controlled sweep adjustment with repeat blood-gas assessment as more directly targeted than increasing blood flow alone.

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Fever increases cardiac output and oxygen consumption while VV ECMO blood flow remains unchanged. Explain why arterial saturation may fall even though oxygenator outlet blood remains well oxygenated and the membrane is functioning.

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Increasing VV flow raises drainage-line saturation but barely changes systemic saturation. Explain why return blood may be re-entering the drainage pathway and why cannula assessment can be more useful than further speed escalation.

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A femoral VA ECMO patient has strong ventricular ejection, severe lung dysfunction and a low right radial saturation despite excellent post-oxygenator oxygenation. Recognise differential oxygenation and evaluate the native lung contribution and mixing pattern.

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At stable VA flow, echocardiography shows an enlarging left ventricle and minimal aortic valve opening while pulmonary congestion worsens. Identify a mechanical unloading assessment as the appropriate focus rather than adjustment of sweep alone.

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An improving adult is ventilated with FiO2 0.40, PEEP 8 cmH2O, tidal volume 6 mL/kg predicted body weight and plateau pressure 26 cmH2O. After a supervised three-hour off-sweep interval at unchanged support, PaO2 is 78 mmHg, PaCO2 45 mmHg and pH 7.37; respiratory rate is 22/min, without excessive effort or haemodynamic instability. This supports further decannulation assessment under the ELSO approach. Adequate oxygenation with worsening acidemia or excessive effort would instead indicate an unsuccessful trial.

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An arterial bubble detector activates and visible air is present upstream of the patient. Recognise interruption of delivery through the affected path as the protective objective while the team initiates its rehearsed air-management response.

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Venous return suddenly decreases during a surgical manoeuvre and reservoir level falls rapidly. Reduce outflow to match available return while alerting the team and checking the drainage pathway, before the reservoir reaches an unsafe volume.

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A power interruption occurs while the patient depends on bypass. Explain why an accessible but untested manual drive is insufficient preparation, and identify confirmed backup operation plus measured patient flow as essential evidence of restored support.

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Post-oxygenator oxygenation suddenly worsens while measured blood flow and pressures remain stable. A disconnected gas line is found. Restore the gas pathway using the available source and verify gas exchange with repeat measurements.

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During full CPB with negligible native contribution, a sensor reads 5.0 L/min upstream of a branch returning 0.5 L/min to the reservoir. Assuming no other branches, calculate patient arterial flow as 4.5 L/min and use that value with systemic arterial oxygen content to calculate delivery.

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After cannula adjustment, one cerebral saturation falls while the opposite side and systemic arterial saturation remain stable. Check the sensor and head position, then urgently assess regional perfusion and cannula-related explanations with the team.