What are the steps involved in cardiopulmonary bypass (CPB)?

Cardiopulmonary Bypass: Step-by-Step Protocol

Cardiopulmonary bypass must follow a systematic, sequential approach beginning with rigorous preparation, proceeding through initiation and maintenance phases, and concluding with safe weaning—each step requiring specific safety checks and physiological targets to prevent morbidity and mortality.

Phase 1: Pre-CPB Preparation

Preoperative Assessment

• Complete a standardized institutional preoperative assessment form documenting the patient's condition, concomitant diseases, and planned surgical procedure—this allows the perfusionist to anticipate complications and plan accordingly 1.
• Maintain this assessment as a written or electronic document in the patient's medical record 1.
• Conduct multidisciplinary planning involving all stakeholders in the patient's care pathway 1.

Pre-CPB Checklist

• Execute a mandatory pre-CPB checklist adapted to your specific institutional environment—checklists have proven efficacy in reducing complications, saving time, and preventing mortality 1.
• Review and revise checklists at intervals consistent with institutional protocol, incorporating emerging technologies 1.
• Use checklists in a diligent and professional manner as part of a culture of safety 1.

Circuit Preparation

Select between conventional CPB or minimized extracorporeal circulation (MiECC) based on surgical complexity:

For MiECC systems (preferred when feasible for reduced complications):

• Small priming volume with tip-to-tip biocompatible coating 1
• Closed circuit system 1
• Centrifugal blood pump 1
• Membrane oxygenator with heat exchanger 1
• Venous bubble trap/air-removing device 1
• Shed blood management system (mechanical salvage instead of cardiotomy suction) 1
• Cardioplegia delivery system 1

Biocompatible coating reduces neurological complications (3.9% vs 9.4% without coating) and improves renal function 1.

Gas Supply Verification

• Confirm continuous piped supplies of oxygen, air, and carbon dioxide with backup cylinder supplies available 1.
• Install and test scavenging system for volatile anesthetics at oxygenator outlet to prevent occupational exposure 1.
• Monitor all incoming and outgoing gases 1.

Phase 2: Initiation of CPB

Cannulation

• Establish venous drainage to reservoir 2.
• Place arterial return cannula 2.
• Monitor for cannulation complications including dissection, malposition, and gas embolism 3.

Circuit Priming and De-airing

• Prime circuit with appropriate volume (minimized in MiECC systems) 1.
• Flush extracorporeal circulation with CO2 before priming to prevent air embolism 1.
• Verify all connections and check for leaks 2.

Anticoagulation

• Administer systemic anticoagulation before initiating bypass 1.
• Administer tranexamic acid routinely (used in 88% of centers) 4.

Phase 3: CPB Maintenance

Hemodynamic Targets

Maintain pump flow >2.2 L/min/m² in 93% of cases 4:

• Target mean arterial pressure 51-90 mmHg 4
• Individualize or maintain hemoglobin >7-8 g/dL (transfusion trigger used in 92% of centers) 4

Oxygenation Monitoring

• Monitor mixed venous oxygen saturation routinely (standard in 59% of centers) 4.
• Check lactate levels regularly (88% of centers) 4.
• Use noninvasive cerebral saturation monitoring routinely or in high-risk patients (84% of centers) 4.

Temperature Management

• Monitor temperature via nasopharynx (preferred site in 66% of centers) 4.
• Utilize heat exchanger for controlled hypothermia or normothermia 1.

Physiological Goals

Maintain parameters approximating normal physiology for optimal end-organ function 1:

• Adequate tissue perfusion and oxygenation 1
• Appropriate depth of anesthesia (monitor routinely in 53% of centers) 4
• Continuous anticoagulation monitoring 1

Anesthetic Management During CPB

Choose one primary anesthetic approach:

• Volatile agents as sole agent (36% of centers) 4, OR
• Propofol infusion (47% of centers) 4
• Use depth-of-anesthesia monitoring to prevent awareness during CPB 3, 4

Adjunctive Medications

• Magnesium supplementation (45% of centers) 4
• Steroids in selected cases (18% of centers) 4
• Aprotinin when indicated (15% of centers) 4

Ventilation Strategy

• Consider low-tidal-volume ventilation during CPB (26% of centers) 4
• Apply continuous positive airway pressure (28% of centers) 4

Advanced Monitoring

• Use transesophageal echocardiography routinely or in selected patients (97% of centers) 4.
• Consider pulmonary artery catheter placement (71% of centers use routinely or selectively) 4.

Phase 4: Safety Monitoring Throughout CPB

Equipment Surveillance

Continuously monitor for CPB equipment failures 3:

• Heater-cooler malfunction 3
• Oxygenator dysfunction 3
• Electrical system failure 3
• Tubing rupture 3
• Circuit thrombosis 3

High-Risk Complications

Maintain vigilance for the highest-risk events across all circuit types 1:

• Air embolism (most critical risk) 1
• Defoamer material embolization 1
• Spallation 1
• Over-pressurization 1
• Systemic inflammatory response activation 1

Phase 5: Weaning from CPB

Preparation for Separation

• Restore adequate cardiac function 2
• Achieve appropriate body temperature 2
• Correct metabolic derangements 2
• Ensure adequate volume status 2

Gradual Flow Reduction

• Progressively reduce pump flow while monitoring hemodynamics 2
• Assess cardiac function via transesophageal echocardiography 4
• Provide individualized pharmacologic or mechanical support for cardiac dysfunction as needed 5

Critical Pitfalls to Avoid

Time-dependent complications increase significantly:

• Risk rises when CPB exceeds 2 hours 5
• Risk increases sharply when pump time exceeds 3-4 hours 5
• Prolonged CPB exacerbates blood trauma, capillary membrane permeability abnormalities, and tissue anoxia 5

Systemic inflammatory response complications 6:

• Capillary leak syndrome 6
• Coagulopathy 6
• Respiratory failure 6
• Myocardial dysfunction 6
• Renal insufficiency 6
• Neurocognitive decline 6

Prevention strategies:

• Meticulous filtration throughout procedure 5
• Strict attention to myocardial and tissue preservation 5
• Precise technique to avoid prolonged extracorporeal circulation 5
• Team coordination between surgeon, perfusionist, and anesthesiologist is paramount 2