A multichannel catheter for extracorporeal circulation of blood to a patient undergoing cardiovascular treatments or surgery has three independent channels, an obturator and an expandable balloon. The first channel is the largest and is of a size that allows for delivery of blood through outlet parts in the wall of the first channel to a patient in an amount sufficient to maintain the patient's metabolism and perfusion throughout the treatment or surgery. The obturator is longitudinally insertable into the first channel. The second and third channels are integrated into the wall of the first channel. The second channel is suitable for delivering a biologically active fluid to the heart and/or venting the left heart. The third channel is suitable for delivering a fluid to the balloon for its expansion. The catheter provides an improved means of preparing for or performing cardiovascular surgery on a patient using a cardiopulmonary machine for extracorporeal circulation of blood.