Comparing oxygen transfer performance between three membrane oxygenators: effect of temperature changes during cardiopulmonary bypass.

Recently, a new oxygenator (Dideco 903 [D903], Dideco, Mirandola, Italy) has been introduced to the perfusion community, and we set about testing its oxygen transfer performance and then comparing it to two other models. This evaluation was based on the comparison between oxygen transfer slope, gas phase arterial oxygen gradients, degree of blood shunting, maximum oxygen transfer, and diffusing capacity calculated for each membrane. Sixty patients were randomized into three groups of oxygenators (Dideco 703 [D703], Dideco; D903; and Quadrox, Jostra Medizintechnik AG, Hirrlingen, Germany) including 40/20 M/F of 68.6 +/- 11.3 years old, with a body weight of 71.5 +/- 12.1 kg, a body surface area (BSA) of 1.84 +/- 0.3 m(2), and a theoretical blood flow rate (index 2.4 times BSA) of 4.4 +/- 0.7 L/min. The maximum oxygen transfer (VO(2)) values were 313 mL O(2)/min (D703), 579 mL O(2)/min (D903), and 400 mL O(2)/min (Quadrox), with the D903 being the most superior (P < 0.05). Oxygen (O(2)) gradients were 320 mm Hg (D703), 235 mm Hg (D903), and 247 mm Hg (Quadrox), meaning D903 and Quadrox are more efficient versus the D703 (P < 0.05). Shunt fraction (Qs/Qt) and diffusing capacity (DmO(2)) were comparable (P = ns). Diffusing capacity values indexed to BSA (DmO(2)/m(2)) were 0.15 mL O(2)/min/mm Hg/m(2) (D703), 0.2 mL O(2)/min/mm Hg/m(2) (D903), and 0.18 mL O(2)/min/mm Hg/m(2) (Quadrox) with D903 outperforming D703 (P < 0.0005). During hypothermia (32.0 +/- 0.3 degrees C), there was a lower absolute and relative VO(2 )for all three oxygenators (P = ns). The O(2) gradients, DmO(2) and DmO(2)/m(2), were significantly lower for all oxygenators (P < 0.01). Also, Qs/Qt significantly rose for all oxygenators (P < 0.01). The oxygen transfer curve is characteristic to each oxygenator type and represents a tool to quantify oxygenator performance. Using this parameter, we demonstrated significant differences among commercially available oxygenators. However, all three oxygenators are considered to meet the oxygen needs of the patients.

A novel device for reducing hemolysis provoked by cardiotomy suction during open heart cardiopulmonary bypass surgery: a randomized prospective study.

Since the inception of cardiopulmonary bypass (CPB), little progress has been made concerning the design of cardiotomy suction (CS). Because this is a major source of hemolysis, we decided to test a novel device (Smartsuction [SS]) specifically aimed at minimizing hemolysis during CPB in a clinical setting. Block randomization was carried out on a treated group (SS, n=28) and a control group (CTRL, n=26). Biochemical parameters were taken pre-, peri-, and post CPB and were compared between the two groups using the Student's t-test with statistical significance when P<0.05. No significant differences in patient demographics were observed between the two groups. Lactate dehydrogenase (LDH) and plasma free hemoglobin (PFH) pre-CPB were comparable for the CTRL and SS groups, respectively. LDH peri-CPB was 275+/-100 U/L versus 207+/-83 U/L for the CTRL and SS groups, respectively (P<0.05). PFH was 486+/-204 mg/L versus 351+/-176 mg/L for the CTRL and SS groups, respectively (P<0.05). LDH post CPB was 354+/-116 U/L versus 275+/-89 U/L for the CTRL and SS groups, respectively (P<0.05). PFH was 549+/-271 mg/L versus 460+/-254 mg/L for the CTRL and SS groups, respectively (P<0.05). Preoperative hematocrit (Hct) of 43+/-5% (CTRL) versus 37+/-5% (SS), and hemoglobin (Hb) of 141+/-16 g/L (CTRL) versus 122+/-17 g/L (SS) were significantly lower in the SS group. However, when normalized (N), the SS was capable of conserving Hct, Hb, and erythrocyte count perioperatively. Erythrocytes (N) were 59+/-5% (CTRL) versus 67+/-9% (SS); Hct (N) was 59+/-6% (CTRL) versus 68+/-9% (SS), and Hb (N) was 61+/-6% (CTRL) versus 70+/-10% (SS) (all P<0.05). This novel SS device evokes significantly lowered blood PFH and LDH values peri- and post CPB compared with the CTRL blood using a CS system. The SS may be a valuable alternative compared to traditional CS techniques.

A prototype paediatric venous cannula with shape change in situ.

During cardiopulmonary bypass (CPB), venous drainage may be impeded due to small vessel and cannula size or chattering, thus, blood return to the heart-lung machine is reduced. We designed a self-expandable prototype cannula, which is able to maintain the vein open and overcome this problem and analysed its performance capability. This prototype and several other cannulae were tested using an access vessel diameter of 7 mm. An in vitro circuit was set up with a 10 mm penrose latex tube simulating the patient's vein placed between the patient preload reservoir and the cannula, encasing the cannula's inlet(s). Maximum flow rate was determined for passive venous drainage (PVD) at preloads (P) of 2 and 4 mmHg. We compared these results to three classic single-stage venous cannulae: basket tip, thoracic drain and percutaneous tip. By comparing the other cannulae to the prototype, under PVD conditions and a central venous pressure (CVP) of 2 mmHg, the prototype cannula's flow rate (1.32 +/- 0.04 L/min) outperformed the basket type (the best performing comparator) (1.02 +/- 0.08 L/min) by 23% (p < 0.005). When the preload was increased to 4 mmHg under PVD conditions, the same trend was noted with the prototype cannula (1.65 +/- 0.05 L/min), outperforming the basket cannula's value (1.26 +/- 0.05 L/min) by 24% (p < 0.001). This new cannula design provides superior flow characteristics, under all test conditions, compared to the classic single-stage venous cannulae used for paediatric CPB surgery.

[Paediatric mechanical cardiac assistance]. / Assistance cardiaque mécanique pédiatrique.

The mechanical cardiac assistance, once limited only to the adult patients, is now progressively extended to the paediatric population, including neonates. Currently for children with cardiorespiratory insufficiency requiring for a mechanical assistance there are available several options: Intra-Aortic Balloon Pump, Extra-Corporeal Membrane Oxygenation (ECMO) et le Ventricular Assist Device. From April 1999 in our Department of Cardiovascular Surgery at CHUV 8 children, including 4 neonates, have been treated with ECMO. Indications, contra-indications, advantages, disadvantages, results and complications of the available options of paediatric mechanical cardiac assistance are described.