Normal and abnormal trans-oxygenator pressure gradients during cardiopulmonary bypass

Abstract

A prospective study was conducted with the aims of 1) determining the normal trans-oxygenator pressure gradient characteristics for a range of oxygenators and 2) determining the characteristics, incidence and outcome of abnormally raised gradients. The trans-oxygenator pressure gradient was monitored in 3684 patients undergoing open-heart surgery in eight different hospitals. When the normal pressure gradient was measured during cardiopulmonary bypass in mmHg/L blood flow, a constant figure was obtained which was specific for each oxygenator. This gradient was abnormally raised in 16 cases (one in every 230 cases) and was raised to such an extent in three of these cases that an emergency oxygenator changeout was required (one in every 1228 cases). Among the 16 reported incidents, three different patterns of gradient changes occurred, suggesting the possibility that there were three different aetiologies. In nine of these incidents, the pressure gradient was normal immediately upon going on bypass, but rose rapidly to a plateau value, which then returned to the normal value within 40 minutes. In three cases, the pressure gradient was raised immediately upon going on bypass and then rapidly returned to the baseline. In one case, the pressure gradient was raised immediately upon going on bypass and stayed raised throughout the operation.

Leukocyte-derived extracellular DNA contributes to abnormal pressure elevation in the extracorporeal circulation circuit

“…Furthermore, heparin injection caused leukocytes to release extracellular DNA. Previous studies have reported an abnormal elevation in pressure in CPB [1][2][3][4][5][6][7][8][9] . However, no studies have suggested that extracellular DNA can contribute to abnormal elevation in pressure.…”

“…Hypothermia and alkalemia might also be associated with an abnormal elevation in pressure, although these factors are not sufficient by themselves 3,9 . Fibrin deposition inside CPB equipment might be involved in the underlying mechanism 1,2,6,9,10,12 . However, whether intensification of anticoagulation can ameliorate an abnormal elevation in pressure is unclear because most patients have already received a large amount of unfractionated heparin 1,2,11,12 .…”

Alkalemic conditions result in blood clotting in the circuit soon after initiating cardiopulmonary bypass

“…However, if a blood clot occurs, the venous reservoir filter and membrane oxygenator can become obstructed, and it may become necessary to replace parts during surgery, 1,4) although a blood clot in the circuit that appears soon after initiating CPB may reversibly disappear with time. 4) In this study, we hypothesized that blood clotting in the circuit may be caused by echinocytes that form because of alkalization of the priming fluid, as previously reported. 6) We therefore investigated blood clotting in the circuit soon after initiating CPB under six different priming conditions.…”

Epoprostenol for the treatment of increasing oxygenator pressure drop during cardiopulmonary bypass. A case report

“…There is also an increased risk for infection. [1][2][3] In our unit, the main indication for an oxygenator change during CPB is an increasing drop in blood pressure across the oxygenator in the cardiopulmonary bypass circuit with a preoxygenator blood pressure of 550 mmHg or more. This level has been chosen as the risk of tubing rupturing in the pump or that connectors and tubing separation increase rapidly above this level.…”

“…A theoretical explanation is platelet aggregation inducing a conjugation of the leucocytes and fibrinogen with the formation of a macroscopically visible gel. 2,3,5,6 Because of the risks associated with a change of an oxygenator during CPB, we have, in our department, explored alternative solutions.…”