Negative line pressure in Mini-CPB circuit
Research type
Research Study
Full title
Negative venous line pressure in a miniaturised cardiopulmonary bypass circuit – the influence of a fenestrated venous cannula and its effect on pump flow.
IRAS ID
172088
Contact name
Mark J Bennett
Contact email
Sponsor organisation
Plymouth Hospitals NHS Trust
Duration of Study in the UK
0 years, 11 months, 26 days
Research summary
During the majority of heart surgery a ‘heart-lung machine’ or cardiopulmonary bypass circuit is used to supply blood, carrying oxygen, to the body while the surgeon is operating on the heart. Traditionally the ‘heart-lung’ machine contains a 2-litre reservoir from which blood is supplied with oxygen and delivered back to the body. To avoid the dilution of the blood and to reduce the chance of needing a blood transfusion we have been using a miniaturised heart-lung machine (Mini-CPB), without a venous reservoir, for many of our heart operations in Plymouth for the past 8 years.
Because the pump that pumps the blood back to the patient, in this type of circuit, also pulls the blood from the patient, rather than draining by gravity into a venous reservoir, a negative pressure can be generated in the drainage (venous) pipe. The negative pressure has three potential consequences: a high negative pressure may cause damage to the blood in the pump resulting in fracturing of the blood cells; the negative pressure may cause effervescence (microbubbles) in the blood producing miniaturised air bubbles in the blood and; the flow of blood from the patient can be temporarily and repeatedly interrupted thus reducing the flow back to the patient.
We want to investigate whether a new venous drainage pipe (cannula) which has three sets of drainage holes (three-stage) compared with the standard two-stage cannula, or a three-stage which also has additional windows (fenestrations), can improve the drainage of blood into the circuit, reducing the negative pressure produced and increase the blood flow delivered to the patient. Patients who consent to participate will be randomly assigned to one of three types of venous cannula:
1. Standard venous cannulation with a two-stage venous cannula
2. The three-stage cannula (91437C, Medtronic)
3. The fenestrated three-stage cannula (MC2X, Medtronic)
Apart from measuring the pressures in the pipes and the flow back to the patient we will record any evidence of red cell damage and the number and size of any microbubbles produced in the circuit.REC name
South West - Cornwall & Plymouth Research Ethics Committee
REC reference
15/SW/0280
Date of REC Opinion
12 Nov 2015
REC opinion
Further Information Favourable Opinion