Clinical Perfusion Glossary
Comprehensive, peer-reviewed definitions of critical physiological and technical terms encountered in extra-corporeal circulation and cardiac perfusion.
Activated Clotting TimeACT
A point-of-care coagulation test that measures the time (in seconds) required for whole blood to clot after exposure to an activator (such as kaolin or celite).
Clinical Significance
Used to monitor high-dose heparin anticoagulation during cardiopulmonary bypass. The standard target ACT is >400–480 seconds before initiating CPB to prevent circuit thrombosis.
Acute Kidney InjuryAKI
An abrupt decline in kidney function, often defined by increases in serum creatinine, decreases in urine output, or the need for renal replacement therapy.
Clinical Significance
Cardiac surgery-associated AKI (CSA-AKI) is a severe postoperative complication. Goal-Directed Perfusion (GDP) targeting DO₂I > 270 mL/min/m² is clinically proven to reduce AKI rates.
Alpha-stat Regulation
An acid-base management strategy on bypass that does not correct blood gas values for the patient's actual hypothermic temperature, maintaining a constant state of ionization of histidine residues.
Clinical Significance
Alpha-stat preserves cellular enzyme function and autoregulation of cerebral blood flow, making it the preferred method for standard adult cardiac surgery.
Anion GapAG
The calculated difference between measured cations (sodium) and measured anions (chloride and bicarbonate) in serum.
Clinical Significance
Indicates the presence of unmeasured anions, helping differentiate the causes of metabolic acidosis on bypass (e.g., lactic acidosis from tissue hypoperfusion).
Antegrade Cardioplegia
Cardioplegia solution infused in the same direction as normal coronary blood flow, usually via the aortic root or directly into the coronary ostia.
Clinical Significance
Achieves rapid diastolic cardiac arrest but may have poor distribution in the presence of severe coronary artery stenosis.
Body Surface AreaBSA
The measured or calculated surface area of a human body, standardly expressed in square meters (m²).
Clinical Significance
Crucial for determining individualized metabolic requirements, targeted pump flow rates, and indexing clinical parameters on cardiopulmonary bypass.
Cardiopulmonary BypassCPB
A technique that temporarily takes over the function of the heart and lungs during surgery, maintaining systemic circulation and oxygenation.
Clinical Significance
Requires an extracorporeal circuit consisting of a pump (roller or centrifugal), an artificial oxygenator, reservoir, and heat exchanger.
Cardioplegia
A high-potassium solution infused into the coronary circulation to arrest the heart in diastole, minimize metabolic demand, and protect the myocardium from ischemic injury.
Clinical Significance
Essential for providing a still, dry surgical field for open-heart procedures while preserving myocardial cellular viability.
Delta Gap
The difference between the patient's calculated anion gap and a normal anion gap, compared to the deficit in bicarbonate.
Clinical Significance
Used in advanced blood gas analysis to identify complex, mixed metabolic acid-base disorders.
Goal-Directed PerfusionGDP
A perfusion strategy that continuously monitors and optimizes oxygen delivery (DO₂I) above a critical physiological threshold (270 mL/min/m²).
Clinical Significance
Focuses on maintaining the balance between systemic oxygen supply and metabolic demand on bypass, significantly reducing the risk of postoperative acute kidney injury.
Hemodilution
An increase in the fluid content of blood (plasma volume) relative to cellular elements, resulting in decreased hematocrit and viscosity.
Clinical Significance
Occurs acutely on bypass due to crystalloid priming volumes. Controlled hemodilution improves microvascular flow under hypothermia but must be managed to avoid cellular hypoxia.
Heparin
A highly sulfated glycosaminoglycan utilized as an injectable anticoagulant to prevent thrombus formation.
Clinical Significance
Binds to antithrombin III, accelerating its inhibition of clotting factors (principally thrombin and Factor Xa). Standardly dosed at 300–400 U/kg before bypass.
Hypokalemia
A serum potassium level below the standard reference range (typically < 3.5 mEq/L).
Clinical Significance
Increases myocardial cell excitability and can cause refractory ventricular fibrillation or arrhythmias during or after weaning from cardiopulmonary bypass.
Hypothermia
A deliberate reduction in patient core body temperature below normal physiological limits during cardiac surgery.
Clinical Significance
Reduces systemic tissue oxygen requirements and metabolic rate, providing organ protection during periods of reduced or interrupted systemic blood flow.
Oxygen Content of Arterial BloodCaO₂
The total volume of oxygen carried in 100 mL of arterial blood, including oxygen bound to hemoglobin and dissolved in plasma.
Clinical Significance
Determined by hemoglobin concentration, arterial oxygen saturation (SaO₂), and partial pressure of oxygen (PaO₂).
Oxygen DeliveryDO₂ / DO₂I
The volume of oxygen delivered to systemic tissues per minute, calculated as the product of cardiac output (or pump flow) and arterial oxygen content.
Clinical Significance
Indexed to BSA (DO₂I) on bypass. Maintaining DO₂I above 270 mL/min/m² ensures aerobic cellular respiration and preserves organ function.
Oxygen ConsumptionVO₂ / VO₂I
The volume of oxygen consumed by systemic tissues per minute, calculated using the Fick principle from the difference between arterial and mixed venous oxygen content.
Clinical Significance
Reflects systemic metabolic rate, which decreases with hypothermia and anesthetic depth and increases during shivering or light anesthesia.
Oxygenator
A disposable medical device containing microporous hollow fibers that acts as an artificial lung, exchanging oxygen and carbon dioxide.
Clinical Significance
The heart of the CPB circuit, where blood flows around the fibers and sweep gas flows through the inside of the fibers.
pH-stat Regulation
An acid-base management strategy on bypass that tempers and corrects blood gas values for the patient's actual hypothermic temperature, adjusting sweep gas to maintain pH 7.40 and pCO₂ 40 mmHg at core temperature.
Clinical Significance
Leads to respiratory acidosis relative to alpha-stat, causing cerebral vasodilation. Frequently preferred in pediatric cardiac surgery to optimize cerebral cooling.
Protamine Sulfate
A highly alkaline protein that acts as an immediate antidote to heparin, reversing its anticoagulant effects.
Clinical Significance
Forms a stable, inactive ionic salt complex with heparin. Must be infused slowly to prevent systemic hypotension or anaphylactoid reactions.
Retrograde Cardioplegia
Cardioplegia solution infused in the direction opposite to normal coronary flow, via a cannula inserted directly into the coronary sinus.
Clinical Significance
Provides excellent protection to the left ventricle and behind obstructed coronary arteries, but may offer suboptimal protection to the right ventricle.
Sweep Gas Flow
The flow rate of gas (air/oxygen mixture) passing through the hollow fibers of the membrane oxygenator.
Clinical Significance
Directly controls the clearance of carbon dioxide from the patient's blood; increasing sweep gas lowers blood pCO₂.
Systemic Vascular ResistanceSVR
The resistance to blood flow offered by the systemic vascular bed, determined by arteriolar tone.
Clinical Significance
Calculated as ((MAP - CVP) / CO) × 80. Crucial for guiding the administration of vasodilators or vasoconstrictors on bypass.