Anaes · Cardiac anaesthesia
Cardiopulmonary bypass circuit: components, physiology, and anaesthetic priorities
Also known as CPB circuit · Cardiopulmonary bypass anaesthesia · Heart-lung machine
Ordered CPB circuit components, heparin and ACT targets, indexed flows and MAP, alpha-stat versus pH-stat, weaning with rate-rhythm-preload-afterload-contractility, protamine reactions, air embolism, and TRICS III transfusion context for ANZCA Final.
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Red flags
- Never go on bypass without confirmed adequate ACT.
- Arterial cannula dissection or malperfusion is a surgical emergency.
- Massive air entrainment requires immediate circuit and field management.
- Protamine can cause catastrophic pulmonary hypertension and systemic hypotension.
- Vasoplegia after CPB needs noradrenaline/vasopressin and sometimes methylene blue.
Meet the patient
A 68-year-old for elective CABG is heparinised, the ACT is confirmed, and the surgeon calls for bypass. Your job for the next hour is to manage the physiology of the machine that has just replaced the patient's heart and lungs — non-pulsatile flow, haemodilution, hypothermia, and the inflammatory response — and to bring him off it in one piece (taught CPB vignette).[3]
The two questions every CPB case turns on: is the circuit primed, the ACT therapeutic, and the cannulae placed correctly? and can the heart separate from the pump when the time comes? Say the circuit order first, confirm the ACT second, and wean with structure third — that order mirrors safe conduct and safe viva conduct.[4]
References7ShowHide
- [1]Mazer CD, Whitlock RP, Fergusson DA, et al. Restrictive or Liberal Red-Cell Transfusion for Cardiac Surgery. N Engl J Med, 2017.PMID 29130845
- [2]Levy JH, Ghadimi K, Kizhakkedathu JN, Iba T What's fishy about protamine? Clinical use, adverse reactions, and potential alternatives. J Thromb Haemost, 2023.PMID 37062523
- [3]Pereira RM, Guerra N, Ferreira R, et al. Contemporary Clinical Practices in Anticoagulation Management During Cardiopulmonary Bypass: A Europe-Wide Survey. Interdiscip Cardiovasc Thorac Surg, 2026.PMID 41787968
- [4]Shore-Lesserson L, Baker RA, Ferraris V, et al. STS/SCA/AmSECT Clinical Practice Guidelines: Anticoagulation during Cardiopulmonary Bypass. J Extra Corpor Technol, 2018.PMID 29559750
- [5]Clark TD, Ecklund JM, McCall MM, et al. Comparison of three methods to estimate heparin loading dose for cardiopulmonary bypass. J Extra Corpor Technol, 1996.PMID 10160446
- [6]Hahn RT, Abraham T, Adams MS, et al. Guidelines for performing a comprehensive transesophageal echocardiographic examination: recommendations from the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists. J Am Soc Echocardiogr, 2013.PMID 23998692
- [7]Mattox KL, Guinn GA, Rubio PA, Beall AC Jr Use of the activated coagulation time in intraoperative heparin reversal for cardiopulmonary operations. Ann Thorac Surg, 1975.PMID 1079715