Martin Tönz

Normothermia versus hypothermia during cardiopulmonary bypass: a randomized, controlled trial.

To evaluate the influence of perfusion temperature on systemic effects of cardiopulmonary bypass (CPB), 30 patients undergoing elective coronary artery bypass grafting were randomly assigned to either normothermic (warm, n = 14, 36 degrees C) or hypothermic (cold, n = 16, 28 degrees C) CPB. Serial hemodynamic measurements and blood samples were obtained before, during and after the CPB procedure. During CPB, there were no differences between both groups in the need for vasopressors (norepinephrine, phenylephrine), urinary output, or fluid balance. In the early postoperative period, normothermic CPB patients had significantly lower systemic vascular resistance and higher cardiac index measurements (mean +/- standard error: systemic vascular resistance, 880 +/- 27 versus 1,060 +/- 57 dyne.s.cm-5, p = 0.025; cardiac index, 3.6 +/- 0.1 versus 2.9 +/- 0.1 L.min-1.m-2, p = 0.01) without differences in the administration of vasoactive drugs. Blood loss was significantly higher in patients after hypothermic CPB (median [range] body surface area: 370 [180-560] versus 490 [280-2,120] mL/m2, p = 0.0006), with a greater need for transfusion of erythrocytes and fresh frozen plasma. Plasma levels of tumor necrosis factor and soluble tumor necrosis factor receptors increased during and after CPB, independent of perfusion temperature. This study suggests a significant influence of CPB temperature and respective perfusion management on postoperative hemodynamics and blood loss. Normothermic CPB is not associated with additional systemic adverse effects.

The influence of leukocyte filtration during cardiopulmonary bypass on postoperative lung function. A clinical study.

The accumulation of activated leukocytes in the pulmonary circulation plays an important role in the pathogenesis of lung dysfunction associated with cardiopulmonary bypass. Animal studies have demonstrated that the elimination of leukocytes from the circulation reduces postoperative lung injury and improves postoperative pulmonary function. We conducted a prospective randomized clinical study to evaluate whether postoperative lung function could be improved by use of a leukocyte filter during cardiopulmonary bypass. Elective coronary artery bypass grafting was done with a leukocyte-depleting arterial blood filter incorporated in the extracorporeal circuit (14 patients, leukocyte filter group) or without the filter (18 patients, control group). Blood samples collected at intervals before, during, and after operation were used for analysis of blood cell counts, elastase concentrations, and arterial blood gases. The use of the leukocyte filter caused no significant reduction in leukocyte count (p = 0.86). There were no differences in postoperative lung function between the groups, as assessed through (1) oxygenation index (290 for leukocyte filter group compared with 329 for control group, 95% confidence interval, 286 to 372, p = 0.21), (2) pulmonary vascular resistance (p = 0.10), and (3) intubation time (16.6 hours for leukocyte filter group versus 15.7 hours for control group, 95% confidence interval, 12.1 to 19.1 hours, p = 0.72). The levels of neutrophil elastase were significantly higher at the end of cardiopulmonary bypass in the leukocyte filter group (460 microgram/L in leukocyte filter group versus 230 microgram/L in control group, 95% confidence interval, 101 to 359 microgram/L, p = 0.003). We conclude that the clinical use of the present form of leukocyte-depleting filter did not improve any of the postoperative lung function parameters analyzed in this study.

Clinical implications of phrenic nerve injury after pediatric cardiac surgery

Phrenic nerve injury with resulting diaphragm paralysis occurred in 25 (1.5%) of 1,656 cardiac surgical procedures in children during a 10-year period. Phrenic nerve injury was most commonly noted in patients who had undergone previous cardiac surgery (16 of 165, 10%; P < .0001), typically after a previous Blalock-Taussig shunt (10 of 53, 19%; P = .007). Plication of the diaphragm (7 thoracic, 4 abdominal) was performed in 11 patients (44%). Indications for plication were inability to wean from mechanical ventilation (5 patients) and persistent or recurrent respiratory distress (6 patients). The patients who needed diaphragm plication were significantly younger than those who were managed conservatively (median, 11 months [4 days to 23 months] versus 20 months [4 months to 16 years]; P = .01). All patients older than 2 years were extubated within 3 days (mean, 1.5 days) and did not need any surgical intervention. The median follow-up period was 3.2 years, and no patient has had recurrent respiratory problems. There were no deaths as a direct result of phrenic nerve injury. Phrenic nerve injury after cardiac surgery is a serious complication that often leads to respiratory insufficiency in patients under than 2 years of age. For such patients, early diaphragm plication is a simple and effective procedure that prevents the complications of prolonged mechanical ventilation.

Continuous versus bolus thermodilution cardiac output measurements : a comparative study

OBJECTIVE To compare the methods for continuous and bolus thermodilution cardiac output measurements. DESIGN In vivo and in vitro experimental studies. SETTING Surgical research division in a university hospital. SUBJECTS Eight calves and flow bench model. INTERVENTIONS Data were collected in vivo from eight calves instrumented with pulmonary artery catheters, which allowed both continuous and bolus thermodilution measurements. The pulmonary artery catheter was placed through the external jugular vein. All in vitro measurements were performed using a flow bench model. MEASUREMENTS AND MAIN RESULTS A total of 232 bolus and continuous thermodilution measurements were analysed in vivo to determine the degree of agreement between the two methods. The absolute measurement bias was 0.14 L/min with 95% confidence limits ranging from -0.83 to 1.15 L/min. In vitro analysis of 576 measurements at six different temperature points (range 31 degrees to 41 degrees C), using clinically relevant flows (2 to 9 L/min), showed overestimation of flow values using continuous and bolus thermodilution methods. However, the continuous method showed better accuracy by a lower degree of overestimation. Systematic error was 9.7 +/- 8.4 (SD) % for continuous and 11.1 +/- 6.3% for the bolus method (p < .001). This effect was especially evident at lower flow rates. The influence of various temperatures on the accuracy and reproducibility of both methods of measurement was statistically significant but not clinically relevant. The infusion of lactated Ringers lactate solution (infusion rates 100 to 1000 mL/hr) affects both methods at a low flow rate of 2 L/min, without causing a significant effect on continuous measurement at a higher flow rate (4 L/min). Shunting of 50% of circulating volume to the distal part of the thermal filament of the pulmonary catheter impaired the accuracy of continuous measurement without affecting results from bolus measurements (systematic error -26.8 +/- 8.2% for continuous and -5.2 +/- 4.1% for bolus thermodilution). CONCLUSIONS Continuous thermodilution cardiac output measurement provided higher accuracy and greater resistance to thermal noise than standard bolus measurements. The correct placement of the catheter is essential for precise measurements.

Mycotic Aneurysm of the Abdominal Aorta: Extra-Anatomic versus in Situ Reconstruction

Between 1973 and 1991, 12 patients with mycotic aneurysm of the abdominal aorta underwent operation. There were four elective and eight emergency procedures. In situ reconstruction was performed in six patients and extra-anatomic reconstruction with axillobifemoral bypass grafting in six. The hospital mortality rate was 25% (three patients) and another three died during the follow-up period of mean 5.5 years. Descending aorta-bifemoral bypass was performed in two patients without signs of chronic local infection 1 and 2 years after previous axillobifemoral bypass. Late complications were peripheral embolization in one patient after in situ reconstruction and a total of five thromboses of the axillofemoral bypass in three patients. Extra-anatomic bypass grafting remains the method of choice for the majority of patients with mycotic aneurysm of the abdominal aorta. In situ reconstruction seems to be an appropriate procedure for a highly selected group of patients.

Sternal cleft associated with vascular anomalies and micrognathia

Sternal defects combined with craniofacial vascular defects are rare. We report on a 45-year-old woman with a sternal cleft associated with craniofacial and brain hemangiomata, an aneurysm of the aortic arch, anomalous origin of the coronary arteries, a left superior vena cava, micrognathia, supraumbilical midline raphe, and a cervical cyst. The surgical procedure consisted of the resection and replacement of the aortic arch and the innominate artery with reimplantation of the left carotid artery into the graft under circulatory arrest and deep hypothermia. The presence of sternal cleft is an indication for the search for other asymptomatic internal vascular anomalies.

TREATMENT OF ACUTE PULMONARY HYPERTENSION WITH INHALED NITRIC OXIDE

We examined the effectiveness of inhaled nitric oxide (NO) as a selective pulmonary vasodilator in acute pulmonary hypertension in an in vivo canine model with fixed cardiac output. In 5 dogs, total right heart bypass was instituted, and pulmonary hypertension was induced by infusion of the thromboxane analogue U-46619. During U-46619 infusion, NO was administered at 10 and 40 ppm for 5 minutes followed by breathing of the oxygen mixture without NO. Pump flow was held constant during the experiment. Infusion of the thromboxane analogue resulted in an increase in pulmonary vascular resistance and systemic vascular resistance from 147 +/- 83 to 740 +/- 126 dyne.s.cm-5 and from 1,720 +/- 113 to 2,407 +/- 232 dyne.s.cm-5, respectively. During inhalation of 10 ppm NO, pulmonary vascular resistance significantly decreased to 613 +/- 55 dyne.s.cm-5 (p < 0.05) and further decreased to 527 +/- 163 dyne.s.cm-5 with 40 ppm NO inhalation (p < 0.05). Systemic vascular resistance did not change during NO treatment (2,300 +/- 70 dyne.s.cm-5 during 40 ppm NO). There was no increase in intrapulmonary shunting or methemoglobin levels during NO inhalation. In this setting, with a constant cardiac output throughout the experiment, NO acted as a selective pulmonary vasodilator without altering systemic vascular resistance. However, induced pulmonary vasoconstriction was only partially reversed by NO inhalation.

Quantitative gas transfer of an intravascular oxygenator

The intravascular oxygenator is a newly developed device for intracaval gas exchange in critically ill patients with respiratory failure. In an experimental ex vivo model, performance characteristics of the intravascular oxygenator/carbon dioxide removal device were studied. With a mean hemoglobin concentration of 6.2 +/- 1.9 g/dL (mean +/- standard deviation), total O2 transfer was 21.8 +/- 4.8 mL/min at a blood flow of 1 L/min, 37.0 +/- 12.6 mL/min at 2 L/min, at 2 L/min, and 47.5 +/- 16.7 mL/min at 3 L/min. Total CO2 transfer was 27.3 +/- 6.6 mL/min at a blood flow of 1 L/min, 38.6 +/- 8.9 mL/min at 2 L/min, and 40.4 +/- 9.3 mL/min at 3 L/min. In contrast to total gas transfer, O2/CO2 transfer rates (mL/L) diminished significantly with increasing blood flow. In addition, there was a negative correlation between O2 transfer rate and venous O2 partial pressure (r = -0.73; p < 0.0001), a positive correlation between CO2 transfer rate and venous CO2 partial pressure (r = 0.65; p < 0.0001), and a positive correlation between O2 and CO2 transfer rates and blood hemoglobin level (r = 0.57 [p < 0.01] and r = 0.70 [p < 0.01], respectively). These results demonstrate that the behavior of the intravascular hollow-fiber oxygenator is similar to that of the classic membrane oxygenator used for cardiopulmonary bypass: total gas transfer correlates directly with blood flow and venous CO2 partial pressure and indirectly with venous O2 partial pressure. The O2 and CO2 transfer rates increase significantly with increasing hemoglobin content of the blood.

Combined coronary artery bypass grafting and repair of aneurysm of the descending aorta

The outcome of patients with thoracic or thoracoabdominal aortic aneurysm is often determined by the concomitant coronary artery disease. Two patients with thoracic and thoracoabdominal aortic aneurysm and concomitant single-vessel coronary artery disease underwent combined myocardial revascularization and repair of aortic aneurysm. The operations were performed through a left thoracotomy and thoracoabdominal incision with distal aortic perfusion using a partial femoro-femoral bypass and selective right lung ventilation. Coronary anastomoses were performed on the beating heart, and the aneurysm was replaced with a woven Dacron tube graft.

Effect of intermittent warm blood cardioplegia on functional recovery after prolonged cardiac arrest

BACKGROUND There is some evidence that continuous warm blood cardioplegia offers good myocardial protection; however, the effects of interrupting cardioplegia remain controversial. To study this, we compared the effects of continuous and intermittent antegrade warm (37 degrees C) blood cardioplegia on functional recovery after prolonged cardiac arrest (180 minutes). METHODS Twenty-four juvenile pigs were randomly assigned into four groups. Group 1 received continuous cardioplegia, group 2 underwent several periods of 15 minutes of cardioplegia interrupted by 5 minutes of normothermic ischemia, and group 3 underwent several periods of 10 minutes of cardioplegia interrupted by episodes of 10 minutes. The hearts of group 4 received no cardioplegia. Left ventricular systolic function was assessed from fractional left ventricular shortening and percentage left ventricular wall thickening, and left ventricular diastolic function was determined from the time constant of relaxation and the constant of myocardial stiffness. RESULTS Systolic and diastolic functions were slightly depressed 1 and 2 hours after cross-clamp removal in all four groups, without significant differences among the groups. CONCLUSIONS These data suggest that antegrade warm blood cardioplegia can be interrupted for up to 10 minutes without obvious negative effects on left ventricular function in the normal myocardium, provided that the intermittent doses of cardioplegia are sufficient to restore the metabolic demands of the arrested myocardium.