Static blood-flow control during cardiopulmonary bypass is a compromise of oxygen delivery.
BACKGROUND
Blood-flow control during cardiopulmonary bypass (CPB) is by tradition based on the patient's body surface area. Emergence of new techniques enables dynamic blood-flow control based on online measurement of venous oxygen saturation and oxygen consumption. Present investigation aimed to compare static versus dynamic blood-flow control with respect to use of oxygen and effects upon organ function.


METHODS
In this study, 100 coronary-artery-bypass surgical patients were prospectively randomised to static or dynamic hypothermic blood-flow control during CPB. In the static group, pump flow was set to 2.4 (litres per minute) times the patient's body surface area (m(2)) throughout the procedure. Pump flow in the dynamic group was varied according to the reading of the venous oxygen saturation and maintained at >75%. CPB-specific information was collected online. Blood samples were collected for analysis of haemoglobin, lactate, amylase, creatinine and C-reactive protein: pre-CPB, at weaning from CPB and on day 1 postoperatively.


RESULTS
Randomisation formed two uniform groups. Choice of static or dynamic blood-flow control during CPB had no significant effects on organ function as judged by lactate, amylase or creatinine levels. On increasing oxygen demand, oxygen balance was maintained by increasing venous oxygen extraction rates in the static flow mode and by increasing the pump flow rate in the dynamic group.


CONCLUSIONS
Independent of the blood-flow control mode, oxygen balance remained preserved. However, the dynamic mode provided higher oxygen delivery, which may increase margins of safety and protection of organ function.
Svenmarker
Staffan
S
Department of Surgical and Perioperative Science, Heart Centre, Umeå University Hospital, Umeå, Sweden. Staffan.Svenmarker@vll.se
Häggmark
Sören
S
Hultin
Magnus
M
Holmgren
Anders
A
D000368:Aged; D001830:Body Surface Area; D002315:Cardiopulmonary Bypass / Q000379:methods*; D001026:Coronary Artery Bypass / Q000379:methods; D005260:Female; D006801:Humans; D007036:Hypothermia, Induced / Q000379:methods; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology*; D011446:Prospective Studies; D014655:Vascular Resistance / Q000502:physiology
D010100:Oxygen