The use of cardiopulmonary bypass during cardiothoracic emergencies is often dependent upon the requirement to provide end-organ perfusion during periods of reduced cardiac output or wherein a surgical repair is indicated. Such eventualities pose various considerations for the perfusionist and conduct of cardiopulmonary bypass; primarily determined by the degree of notice presented by the surgical emergency. This falls into three distinct categories; ‘elective’ emergencies wherein an emergency can be anticipated and planned for, semi-planned emergencies in which surgery is required within a defined timeframe and true emergencies which cannot be anticipated. Considerations predominantly vary across cardiopulmonary bypass circuit adaptations, cannulation strategy and ability to induce systemic anticoagulation. Though cardiopulmonary bypass conduct including rapid cooling, haemofiltration and oxygenated arterial flow rates must also be considered.