Gender-related plasma levels of progesterone, interleukin-8 and interleukin-10 during and after cardiopulmonary bypass in infants and children

The study was conducted at the University of Ulm. Infants and children were consecutively enrolled and underwent CPB if informed consent had been given by the parents. A total of 18 were included (median age 19 months, range 2 months to 15 years). On the day before the CPB, all patients had negative plasma levels of C-reactive protein and were not believed to have infections. Before the elective operation, the patients were in a haemodynamically stable condition and none of them had signs of heart failure. Diagnosis, type of operation, sex and age at operation of every patient are summarized in Table 1. None of the patients was pretreated with β-blockers. Patient 3 (pulmonary atresia with intact ventricular septum) was on prostaglandin and furosemide treatment, and patient 8 (ventricular septal defect) received digoxin. Patients 3 and 15 were cyanotic, with preoperative arterial oxygen saturations of 80 and 72%, respectively. Age, body weight and length, and body surface area were not significantly different between male and female patients (Table 2). The present study was approved by the Institutional Review Board of the University of Ulm.

Anaesthesia was induced and maintained with fentanyl, midazolam (except in patients 6 and 18, who received clorazepate) and vecuronium bromide. Further anaesthetics were used in five male patients (enflurane in patients 9–11 and propofol in patients 6 and 18) and in three female patients (enflurane in patients 1, 8 and 13, and propofol in patient 1). A tri-lumen central venous line was inserted into the internal jugular vein. For the monitoring of arterial blood pressure, an arterial line was placed into the radial artery. Volume-controlled ventilation was applied (SERVO 900 C respirator; Siemens, Munich, Germany). A transurethral catheter was inserted in all patients in order to monitor fluid balance.

The CPB was performed using a CAPS-roller pump system (Stöckert Instruments, Munich, Germany) with continuous flow. The system was connected to a membrane oxygenator (Dideco, Sorin Biomedica, Puchheim, Germany; Cobe Optima, Cobe Laboratories, Planegg-Martinsried, Germany) and an arterial filter. The priming solution consisted of ringer solution and sodium bicarbonate, and contained 2 IU/ml heparin-sodium and 1.5% human albumin. If the haematocrit was expected to drop to below 25% after the patient was connected to the bypass circuit, then red packed cells were added (which contained no detectable levels of progesterone).

After the sternotomy had been conducted (patients 1 and 13 had a right-sided thoracotomy for atrial septal defect type II closure), 30,000 IU/kg aprotinin were administered over a period of 20 min and the administration was continued with 7500 IU/kg per h throughout the operation. Before cannulation of the patient's heart, 300 IU heparin-sodium/kg was given intravenously in order to achieve an activated clotting time of greater than 400s. No corticosteroids were given before or during the operation. After the caval veins, the left atrium and the aorta had been cannulated, hypothermia was induced by cooling down the priming solution (median oesophageal temperature 28.5°C; minimum 28°C and maximum 33°C). A secundum type atrial septal defect in patients 1 and 13 was closed under normothermic conditions. After electrical fibrillation of the heart, 30 ml/kg cold Bretschneider solution was infused into the cross-clamped aortic bulbus. The perfusion index was adjusted to 2.5 ml/kg per m² with the CPB system. At the end of the procedure rewarming was started. Catecholamines were used whenever systemic perfusion was impaired. Heparinization was countered using 300 IU/kg protamine-hydrochloride. The ventilated patients were transferred to the cardiac intensive care unit.

The patients were weaned from the respirator as soon as possible. Crystalloid fluid management consisted of 40 ml/kg per day during the first postoperative day, increasing by approximately 10 ml/kg every other day. Fresh frozen plasma or thrombocytes were given if the patient had postoperative bleeding (>3 ml/kg perh), or if the prothrombin time was below 40% of normal or the thrombocyte count was below 50,000/μl, respectively. Furosemide (0.5–1 mg/kg per dose) was used to facilitate diuresis. Blood pressure was maintained within age-specific ranges with catecholamines (dopamine, dobutamine, adrenaline, noradrenaline).

Blood samples were taken immediately before the operation; after induction of anaesthesia and administration of heparin; 10 min after the commencement of CPB; after disconnection from the circuit and administration of protamine; and 6 h, 24 h, 3 days and 7 days postoperatively. Additional blood samples were taken when this was clinically indicated.

Blood cell counts, electrolytes, urea nitrogen, creatinine, protein, creatine kinase, heart-specific creatine kinase, aspartate aminotransferase, bilirubin, prothrombin time, partial thromboplastin time, fibrinogen and antithrombin III were measured using standard methods. Plasma levels of progesterone were measured in EDTA-medium using a RIA-kit (Coat-A-Count Progesterone; Diagnostic Products Corporation, Los Angeles, CA, USA). The detection limit was 0.02 ng/ml. The intra- and inter-assay coefficient of variation was 4.0 and 5.3% at 1.5 ng/ml, respectively. The test has no detectable cross-reactivity with aldosterone. IL-8 plasma levels were determined immediately after the blood was drawn (EDTA-coated tubes) using a chemiluminescence immunoassay (Immulite; DPC-Biermann, Bad Nauheim, Germany). The lower detection limit for this assay was 5 pg/ml. The assay was calibrated up to 10,000 pg/ml. Intra- and inter-assay coefficient of variation was below 5% and below 2% at 95 pg/ml, respectively. All IL-10 plasma samples (EDTA-coated tubes) were frozen at -70°C and then measured using an enzyme-linked immunoassay (LD Zytokit IL-10 ELISA; LD Labordiagnostica, Heiden, Germany). The assay had a lower limit of detection of 15 pg/ml. Intra- and inter-assay coefficient of variation was 4.0 and 5.5% at 130 pg/ml, respectively. The IL-10 levels at 6 h postoperatively could not be measured because immediate workup of the samples was not possible.

The different organ systems considered and the criteria used to define the dysfunction of an organ system are summarized in Table 3. MOD was diagnosed if two or more organ systems were affected. The occurrence of organ dysfunction was monitored for as long as the patient was in the intensive care unit.