Time course of endothelin-1 and nitrate anion levels after cardiopulmonary bypass in congenital heart defects

Increased Circulating Endothelin 1 Is Associated With Postoperative Hypoxemia in Infants With Single-Ventricle Heart Disease Undergoing Superior Cavopulmonary Anastomosis

Background Inadequate pulmonary vascular growth results in morbidity for many children with single-ventricle heart disease (SVHD). Endothelin 1 (ET1) is a potent vasoconstrictor and stimulator of pulmonary artery smooth muscle proliferation. Circulating ET1 levels and their association with outcomes have not been studied during early SVHD palliation. We aimed to define circulating levels of ET1 in patients with SVHD undergoing stage 2 palliation and evaluate their relationship to postoperative hypoxemia. We hypothesized that patients with SVHD with higher ET1 concentration would have a greater post-stage 2 hypoxemia. Methods and Results Prospective cohort study of 55 subjects with SVHD undergoing stage 2 palliation and 50 controls. Samples for ET1 analysis were collected at preoperation (systemic and pulmonary vein) and 2, 24, and 48 hours postoperation for cases and a single time point for controls. The primary outcome was percentage of first 48 postoperative hours with clinically significant hypoxemia (saturation, <70%). ET1 concentration was lower in preoperative cases than controls (2.2 versus 2.7 pg/mL; P=0.0015) and in the pulmonary vein than systemic vein (1.7 versus 2.2 pg/mL; P<0.001). ET1 level increased by 2 hours postoperation and trended back to baseline by 48 hours. Higher preoperative pulmonary vein ET1 and 2 hours postoperative ET1 were associated with larger hypoxemia burden (10.6% versus 2.7% [P=0.0081]; and 7.6% versus 3.2% [P=0.01], respectively). Multivariable testing demonstrated ET1 concentration and cardiopulmonary bypass time were associated with hypoxemia, whereas catheterization measurements and clinical variables were not. Conclusions Infants with SVHD with higher perioperative ET1 concentration experience more post-stage 2 hypoxemia. ET1 activity may be a modifiable risk factor of pulmonary vascular inadequacy for stage 2 palliation.

Perioperative endothelin levels in patients undergoing intracardiac repair for tetralogy of Fallot

BACKGROUND

Endothelin, a pro-inflammatory molecule, had been extensively studied in patients with cardiovascular illness. Impact on the perioperative outcome of patients with cyanotic congenital heart defects is still unknown. In the present study, we report perioperative changes in endothelin levels and their correlation with preoperative factors and clinical outcomes in a group of patients with tetralogy of Fallot (TOF) undergoing definitive repair.

METHODOLOGY

167 patients with TOF undergoing intracardiac repair under cardiopulmonary bypass were studied. Endothelin levels were taken at three different points of time and correlated with different clinical variables.

RESULTS

The baseline endothelin level correlated with patients' nutritional status and degree of cyanosis. The magnitude of inflammatory response in the post-cardiopulmonary bypass (post-CPB) period as measured by endothelin level was much higher and correlated more consistently with adverse clinical outcomes in the younger age group. On multivariable analysis, age at operation, preoperative degree of hypoxemia, and endothelin levels were found to be independent predictors of clinical outcomes.

CONCLUSIONS

A rise in serum endothelin levels in patients with TOF undergoing definitive repair on CPB, with preoperative severity of cyanosis, nutritional status, and adverse clinical outcomes. The endothelin levels may be monitored to identify patients with cyanosis at an increased risk of exhibiting augmented inflammatory response to CPB.

Splanchnic oxygen saturation immediately after weaning from cardiopulmonary bypass can predict early postoperative outcomes in children undergoing congenital heart surgery

This study compared the abilities of cerebral, renal, and splanchnic regional oxygen saturation (rSO2) immediately after weaning from cardiopulmonary bypass (CPB) to predict early postoperative outcomes for children undergoing congenital heart surgery. The study enrolled 73 children (ages 0.1-72 months) undergoing corrective or palliative cardiac surgery requiring CPB. Laboratory and hemodynamic variables were analyzed at the time of successful weaning from CPB. Using near-infrared spectroscopy, cerebral, renal, and splanchnic rSO2 values were obtained simultaneously. Early postoperative outcome measures included the maximum vasoactive inotropic score (VIS(max)) during the first 36 postoperative hours, the duration of mechanical ventilation, and the postoperative hospital length of stay. In the univariate analysis, cerebral, renal, and splanchnic rSO2 values correlated significantly with early postoperative outcomes. However, splanchnic rSO2 was the only independent factor predicting VIS(max) (β = -0.302, P = 0.021), duration of mechanical ventilation (β = -0.390, P = 0.002), and postoperative hospital length of stay (β = -0.340, P = 0.001) by multivariate analyses. Splanchnic rSO2 had a larger receiver operating characteristic area under the curve (AUC) for determining high VIS(max), prolonged mechanical ventilation, and longer postoperative hospital stay (AUC 0.775, 0.792, and 0.776, respectively) than cerebral (AUC 0.630, 0.638, and 0.632, respectively) and renal (AUC 0.703, 0.716, and 0.715, respectively) rSO2. After weaning from CPB, splanchnic rSO2 may be superior to rSO2 measured from brain and kidney in predicting an increased requirement for vasoactive inotropic support, a prolonged mechanical ventilation, and a longer postoperative hospital stay for children.

Pharmacotherapy for pulmonary hypertension

Pulmonary arterial hypertension is a serious disease with significant morbidity and mortality. Although it can occur idiopathically, it is more commonly associated with other cardiac or lung diseases. While most of the available therapies have been tested in adult populations and most therapies in children remain off-label, new reports and randomized trials are emerging that inform the treatment of pediatric populations. This review discusses currently available therapies for pediatric pulmonary hypertension, their biological rationales, and evidence for their clinical effectiveness.

Pathophysiology of acute pulmonary vasoconstriction

Acute pulmonary vasoconstriction occurs in a variety of clinical settings relevant for the cardiac intensivist, postoperative pulmonary hypertension being perhaps the most common. Although we know that significant postoperative pulmonary vasoconstriction generally occurs in patients with a pathologically remodeled pulmonary circulation, we know little of its pathophysiology. The following review describes the biochemistry of smooth muscle contractile activation and examines the possible role that endothelin-1 may play in postoperative pulmonary hypertension.

Endothelin-1 is not predictive of ventricular ectopy or ventricular fibrillation during acute myocardial ischemia

Endothelin(ET)-1 (ET-1) increases after myocardial infarction and may have effects on myocardial function. ET-1 has also been shown to affect the action potential (AP) which may be arrhythmogenic and predispose to ventricular fibrillation (VF). The effects of ET-2 and ET-3 are uncertain. We hypothesized that the ETs increase during acute ischemia and that plasma levels are predictive of ischemically induced VF. Thirty-four domestic swine underwent balloon occlusion of the proximal LAD coronary artery. Occlusion was confirmed angiographically. Venous samples were collected from the right atrium at baseline and at 5 min intervals for 30 min or until VF induction. ET-1, ET-2, and ET-3 were measured using ELISA. Changes in plasma concentrations were assessed using repeated measures ANOVA with Dunnett's. A p < 0.05 was considered statistically significant. All animals had angiographic evidence of successful proximal LAD occlusion. ET-1 levels were significantly increased from a baseline at 20 min and remained elevated during 30 min of occlusion. ET-2 and ET-3 levels did not change from baseline values (figure, mean +/- SE). VF occurred in 60% of animals. Peak ET-1 values were not significantly different between VF and non-VF animals (6.2 +/- 2.2 vs. 4.8 +/- 2.3 pg/mL). No single ET-1 value had a VF predictive value >50%. There is a significant increase in ET-1 level within 20 min of acute myocardial ischemia. Despite known effects of ET-1 on the AP, this increase did not correlate with the occurrence of VF.

The change of plasma endothelin-1 levels before and after surgery with or without Down syndrome

BACKGROUND

The present study aimed to elucidate the pathophysiological roles of endothelin (ET)-1 in patients with pulmonary hypertension and pulmonary vascular obstructive disease secondary to congenital heart disease and compare the plasma levels of ET-1 between children with and without Down syndrome.

METHODS

Subjects comprised 32 children with congenital heart disease aged 0.5-14 months. Patients were classified into two groups: those with Down syndrome (Group D, n = 16); and those with nonDown syndrome (Group ND, n = 16). Heparinized blood samples were taken from a radial arterial line and plasma ET-1 levels were measured preoperatively, during cardiopulmonary bypass (CPB), a few minutes after termination of CPB, and 2, 6 and 24 h after discontinuation of CPB.

RESULTS

Plasma ET-1 levels were significantly higher in Group D than in Group ND at all times except for a few minutes after termination of CPB. In both groups, peak ET-1 values were obtained at 6 h after CPB. At 24 h after CPB, ET-1 concentrations returned to baseline levels before CPB in Group ND, but not in Group D. A correlation was identified between preoperative pulmonary to systemic pressure ratio and ET-1 concentration before and after CPB in both groups.

CONCLUSIONS

Pre- and postoperative plasma ET-1 concentrations reflect pre- and postoperative pulmonary artery conditions in both groups. Specific features in Down syndrome could be associated with ET injury and might cause persistent increases in ET concentration and prolong artificial respiration.

Congenital Heart Disease Associated Pulmonary Arterial Hypertension

Pulmonary arterial hypertension associated with congenital heart disease, although common (15%-30%) in all-comers with congenital heart disease, is variable in terms of clinical manifestations, severity of associated pulmonary arterial hypertension, and response to therapy and outcomes (depending on lesion anatomy, pulmonary circulation flows and pressures, and presence and timings of surgeries). Evaluation includes imaging and catheterization. Surgical or another anatomic correction may be desirable after rigorous preinterventional assessment. Patients who are not surgical candidates or who fail to improve early or late after surgery may have the potential to respond to idiopathic pulmonary arterial hypertension therapies. Lung or heart/lung transplantation remains an option for selected recalcitrant patients.

Role of the endothelium in pulmonary arterial hypertension

Pulmonary hypertension represents a significant disease burden in both the developed and developing worlds. Certain forms of pulmonary hypertension are more common in some countries than others but people of all races, all ages and both sexes are affected. Treatment options are limited and expensive. The development of new therapies will be determined by improved understanding of endothelial cell biology.

Preoperative glucocorticoids decrease pulmonary hypertension in piglets after cardiopulmonary bypass and circulatory arrest

BACKGROUND

Glucocorticoids during cardiopulmonary bypass benefit pediatric patients undergoing repair of congenital heart defects and are routine therapy, but underlying mechanisms have not been fully examined. The hypothesis was that glucocorticoids could improve cardiopulmonary recovery after cardiopulmonary bypass and deep hypothermic circulatory arrest.

METHODS

Crossbred piglets (5 to 7 kg) were cooled with cardiopulmonary bypass, followed by 120-min deep hypothermic circulatory arrest. Animals were then warmed to 38 degrees C, removed from bypass, and maintained for 120 min. Methylprednisolone (60 mg/kg) was administered in the cardiopulmonary bypass pump prime (intraoperative glucocorticoids) or 6 hours before bypass (30 mg/kg) in addition to the intraoperative dose (30 mg/kg; preoperative and intraoperative glucocorticoids). Controls (no glucocorticoids) received saline.

RESULTS

Pulmonary vascular resistance in controls increased from a baseline of 152 +/- 40 to 364 +/- 29 dynes. s/cm(5) at 2 hours of recovery (p < 0.001). Intraoperative glucocorticoids did not alleviate the increase in pulmonary vascular resistance (301 +/- 55 dynes. s/cm(5) at 2 hours of recovery, p < 0.001). However, animals receiving pre and intraoperative glucocorticoids had no increase in pulmonary vascular resistance (155 +/- 54 dynes. s/cm(5)). Plasma endothelin-1 in controls increased from 1.3 +/- 0.2 at baseline to 9.9 +/- 2.0 pg/mL at 2 hours recovery (p < 0.01), whereas glucocorticoid-treated animals had lower endothelin-1 levels (4.5 +/- 2.1 pg/ml, preoperative and intraoperative glucocorticoids; 4.9 +/- 1.7 pg/mL, intraoperative glucocorticoids) at the end of recovery (p < 0.05). Intracellular adhesion molecule-1 in lung tissue was lower in animals receiving pre and intraoperative glucocorticoids (p < 0.05). Myeloperoxidase activity was elevated in control lungs at 2 hours of recovery compared with glucocorticoid-treated groups (p < 0.05). Inhibitor kappaBalpha, the inhibitor of nuclear factor-kappaB, was higher in lungs of animals receiving glucocorticoids compared with controls (p < 0.05).

CONCLUSIONS

Glucocorticoids prevented pulmonary hypertension after cardiopulmonary bypass and deep hypothermic circulatory arrest, which was associated with reduced plasma endothelin-1. Glucocorticoids also reduced pulmonary intercellular adhesion molecule-1 and myeloperoxidase activity. Inhibition of nuclear factor-kappaB, along with reduced neutrophil activation, contributed to glucocorticoid alleviation of pulmonary hypertension after cardiopulmonary bypass and deep hypothermic circulatory arrest.

Antioxidant therapy with Salvia miltiorrhiza decreases plasma endothelin-1 and thromboxane B2 after cardiopulmonary bypass in patients with congenital heart disease

OBJECTIVE

The endothelium-derived vasoconstrictor endothelin-1 is increased after cardiopulmonary bypass in children with congenital heart defects. This study determines whether antioxidant therapy with Salvia miltiorrhiza injection, an herb extract containing phenolic compounds, prevents the postoperative increase of endothelin-1. The relationship between endothelin-1 and the endothelium-derived prostacyclin (prostaglandin I2) and thromboxane A2 postoperatively is also investigated.

METHODS

Twenty children with congenital heart defects and pulmonary hypertension were randomly assigned to group A (placebo control, n=10) or B (200 mg/kg Salvia miltiorrhiza intravenously after anesthesia induction and at the time of rewarming, respectively; n =10) before cardiac surgery. Central venous blood samples were taken before operation (T(0)), 10 (T(1)) and 30 minutes (T(2)) after starting cardiopulmonary bypass, 10 (T(3)) and 30 minutes (T(4)) after aortic declamping, and 30 minutes (T(5)) and 24 hours (T(6)) after termination of cardiopulmonary bypass. Plasma lipid peroxidation product malondialdehyde, myocardial specific creatine kinase-MB activity, thromboxane B2, and 6-keto-prostaglandin F(1 alpha) (stable metabolites of thromboxane A2 and prostaglandin I2) were measured.

RESULTS

Malondialdehyde increased significantly at T(1) in group A and remained significantly higher than in group B thereafter (P <.05). Malondialdehyde in group B did not significantly increase over time. At T(5), plasma creatine kinase-MB, thromboxane B2, and endothelin-1 in group B were lower than in group A (P <.05); malondialdehyde correlated significantly with creatine kinase-MB (r = 0.71, P =.0005). At T(6), endothelin-1 negatively correlated with the 6-keto-prostaglandin F(1 alpha)/thromboxane B2 ratio (r = -0.64, P =.0025).

CONCLUSION

Antioxidant therapy reduces myocardial damage and attenuates postoperative vasoactive mediator imbalance.

Inflammation After Cardiopulmonary Bypass: Therapy for the Postpump Syndrome

Cardiopulmonary bypass (CPB) is used in most, but not all, complex heart operations. CPB is associated with a systemic inflammatory response in adults and children. Many materials-dependent (exposure of blood to non- physiologic surfaces and conditions) and materials-in dependent (surgical trauma, ischemia-perfusion to the organs, changes in body temperature, and release of endotoxin) factors during CPB have been implicated in the etiology of this complex response. The mechanisms involved may include complement activation, release of cytokines, leukocyte activation with expression of ad hesion molecules, and production of various vasoactive and immunoactive substances. Postpump inflamma tion may lead to postoperative complications and may result in respiratory failure, renal dysfunction, bleeding disorders, neurologic dysfunction, altered liver func tion, and ultimately multiple organ failure. Significant efforts are being made to decrease the generation and effects of postpump inflammation. Interventions to this end have included avoiding CPB when possible, im proving the biocompatibility of the involved mechani cal devices, and administering medications that main tain cellular integrity. This article provides an overview of the etiology, pathophysiology, and treatment of postpump inflammation. Perhaps with additional in sight into this syndrome, CPB can be made a safer and more efficacious modality of cardiorespiratory support. Copyright© 2001 by W.B. Saunders Company.

Inhaled nitric oxide to newborns and infants after congenital heart surgery on cardiopulmonary bypass. A dose-response study

Twelve patients (median age 3.8 months) with pulmonary hypertension in the postoperative period after congenital heart surgery on cardiopulmonary bypass were given inhaled nitric oxide. Effects on cardiovascular and respiratory systems were measured. Mean pulmonary artery pressure decreased from 33+/-2 to 28+/-2 mmHg (p < 0.001) and arterial oxygen tension increased from 13.3+/-2.3 to 16.7+/-2.7 kPa (p < 0.05). The mean change in arterial oxygen tension in percent was 29.8+/-6.3% (p < 0.05). The response was significant only in the first step from 0 to 3 or 5 ppm with no further significant changes in mean pulmonary artery pressure or oxygenation at higher doses. The decrease in mean pulmonary artery pressure was concomitant with a significant increase in arterial oxygen tension. No dose-response relationship was found with increasing doses to 80 ppm.

Temporal endothelin dynamics of the myocardial interstitium and systemic circulation in cardiopulmonary bypass

OBJECTIVE

Increased systemic levels of the bioactive peptide endothelin 1 during and after cardioplegic arrest and cardiopulmonary bypass have been well documented. However, endothelin 1 is synthesized locally, and therefore myocardial endothelin 1 production during and after cardiopulmonary bypass remains unknown.

METHODS

Pigs (n = 11) were instrumented for cardiopulmonary bypass, and cardioplegic arrest was initiated. Myocardial interstitial and systemic arterial levels of endothelin 1 were measured before cardiopulmonary bypass, throughout bypass and cardioplegic arrest (90 minutes), and up to 90 minutes after separation from bypass. Myocardial interstitial endothelin 1 was determined by microdialysis and radioimmunoassay.

RESULTS

Baseline myocardial endothelin 1 levels were higher than systemic endothelin 1 levels (25.6 +/- 6.7 vs 8.3 +/- 1.1 fmol/mL, P <.05). With the onset of bypass, myocardial endothelin 1 increased by 327% +/- 92% from baseline (P <.05), which preceded the increase in systemic endothelin 1 levels.

CONCLUSION

Myocardial compartmentalization of endothelin 1 exists in vivo. Cardiopulmonary bypass and cardioplegic arrest induce temporal differences in endothelin 1 levels within the myocardial interstitium and systemic circulation, which, in turn, may influence left ventricular function in the postbypass period.

Nitric oxide-related compounds in patients with congenital heart defects and pulmonary hypertension

BACKGROUND

The relationship between blood levels of nitric oxide (NO)-related compounds in patients with congenital heart defects (CHD) and degree of pulmonary hypertension (PH) has not yet been described.

METHODS

Thirty-six patients (aged 6 months to 19 years) with CHD were divided into three groups on the basis of their hemodynamic characteristics: group 1 (control, n = 5), left-to-right shunt (-) without PH (pulmonary to systemic artery peak pressure ratio, Pp/Ps < 0.4); group 2 (n = 14), left-to-right shunt (+) without PH; group 3 (n = 17), left-to-right shunt (+) with PH (Pp/Ps > 0.4). Blood samples were obtained from the right atrium, pulmonary artery, left atrium or pulmonary capillary wedge and aorta during cardiac catheterization. All NO-related compounds in whole blood were measured by chemiluminescent assay using Sievers NO analyzer.

RESULTS

The sampling site had no significant impact on NO-related compound levels. However, the patients with PH (group 3) had significantly higher (P < 0.01) blood levels of NO-related compounds (117.3 +/- 14.7 mumol/L) than the patients without PH (groups 1 and 2, 23.9 +/- 3.2 and 38.4 +/- 4.8 mumol/L, respectively). In addition, pulmonary artery resistance (Rp) values of less than 6 Wood U/m2 were directly correlated with levels of NO-related compounds, whereas Rp values greater than 6 Wood U/m2 were inversely correlated with blood levels of NO-related compounds.

CONCLUSION

The present results suggest that the hemodynamic status of the pulmonary circulation in CHD affects, at least partly, blood levels of NO-related compounds.

Endothelins and the lung

Since endothelins were discovered by Yanasigawa in 1988 it has been recognised that they may have an important role in lung pathophysiology. Despite their biological importance as vasoconstrictors the physiological role of endothelin has not yet been defined within the lungs. This review explores their role in acute and chronic disease. During acute inflammation and ischaemia-reperfusion injury cytokines may induce release of endothelin. This is important in the realm of acute lung injury and during surgical procedures such as cardiopulmonary operations including lung resections and transplantation. Complications of surgery including primary organ failure resulting in poor gas exchange as well as increased pulmonary vascular resistance have been linked to the presence of excessive endothelin. Endothelin may have an important role in transplantation biology. The complex process leading to successful lung transplantation includes optimising the donor with brain death, harvesting the lungs, managing acute and chronic rejection, and protecting the vital organs from toxic effects of immunosuppressants. During chronic disease processes, the mitotic action of endothelin may be important in vascular and airway remodelling by means of smooth muscle cell proliferation. We also explore recent advances in drug development, animal models and future directions for research.

Acute right ventricular restrictive physiology after repair of tetralogy of Fallot: association with myocardial injury and oxidative stress

BACKGROUND

Acute right ventricular (RV) restrictive physiology after tetralogy of Fallot repair results in low cardiac output and a prolonged stay in the intensive care unit (ICU). However, its mechanism remains uncertain.

METHODS AND RESULTS

In the first 24 hours after tetralogy of Fallot repair (n=11 patients), serial prospective measurements were performed of cardiac troponin T, indexes of NO production (NO(2)(-) and NO(3)(-) combined as NOx), and iron metabolism and antioxidants. RV diastolic function was assessed by transthoracic Doppler echocardiography. Patients who had a long stay in the ICU were characterized by restrictive RV physiology (nonrestrictive group [n=7]: 3.0+/-0.6 days [mean+/-SD]; restrictive group [n=4]: 10.7+/-3.1 days). Troponin T peak concentration and the area under its concentration-time curve (AUC) were higher in the restrictive RV group (peak: restrictive group 17. 0+/-2.8 microg/L, nonrestrictive group 10.4+/-4.6 microg/L, P<0.03; AUC: restrictive group 268.8+/-73.6 microg. h(-1). L(-1), nonrestrictive group 136.2+/-48.3 microg. h(-1). L(-1), P<0.03). Plasma NOx/creatinine concentrations were higher in the restrictive group than the nonrestrictive group at 2 hours after bypass (restrictive group 1.3+/-0.4, nonrestrictive group 0.8+/-0.2; P=0. 04) but were similar by 24 hours. Iron loading peaked 2 to 10 hours after bypass and was more severe in the restrictive group (peak transferrin saturation: restrictive group 83.9+/-13.0%, nonrestrictive group 58.3+/-16.2%, P=0.05; minimum total iron-binding capacity: restrictive group 0.59+/-0.21%, nonrestrictive group 0.76+/-0.06%, P=0.04; minimum iron-binding antioxidant activity to oxyorganic radicals: restrictive group 9. 5+/-22.4%, nonrestrictive group 50.6+/-11.4%, P=0.01).

CONCLUSIONS

After tetralogy of Fallot repair, acute restrictive RV physiology is associated with greater intraoperative myocardial injury and postoperative oxidative stress with severe iron loading of transferrin.

Effect of modified ultrafiltration on plasma thromboxane B2, leukotriene B4, and endothelin-1 in infants undergoing cardiopulmonary bypass

BACKGROUND

Plasma thromboxane B2 (TXB2), leukotriene B4 (LTB4), and endothelin-1 (ET-1) levels increase on cardiopulmonary bypass (CPB). Elevated levels of TXB2 and ET-1 have been correlated with postoperative pulmonary hypertension in infants undergoing repair of congenital heart defects. LTB4 is a potent chemotactic cytokine whose levels correlate with leukocyte-mediated injury. Modified ultrafiltration (MUF) has been associated with improved hemodynamics and pulmonary function, in addition to its beneficial effects on fluid balance and blood conservation. Recent investigations have suggested that removal of cytokines may be the cause of the improved cardiopulmonary function seen with MUF.

METHODS

Plasma TXB2, ET-1, and LTB4 levels were measured in 34 infants undergoing CPB: 22 underwent MUF (group 1), and 12 did not (group 2). Samples were obtained at various time points. All patients underwent conventional ultrafiltration during the rewarming phase of cardiopulmonary bypass.

RESULTS

In group 1, mean end-CPB TXB2 level was 101.2 pg/mL versus 46.9 pg/mL post-MUF (p < 0.05). The mean TXB2 level 1 hour post-CPB (54.1 pg/mL) was not significantly different from the post-MUF level. In group 2, the mean end-CPB TXB2 level was 123.6 pg/mL versus 53.2 pg/mL 1 hour post-CPB. Hence, TXB2 levels decreased by similar amounts and to similar levels by 1 hour post-CPB in both groups. ET-1 levels increased after CPB and were unaffected by MUF: 1.45, 1.80, 2.55 pg/mL at end-CPB, post-MUF, and 1 hour post-CPB, respectively, in group 1; and 1.51, and 2.73 pg/mL at end-CPB and 1 hour post-CPB in group 2. LTB4 levels post-MUF were 119% of pre-MUF values, and were similar at 1 hour post-CPB in both groups.

CONCLUSIONS

Despite reduction in TXB2 by MUF, values were similar and approached baseline 1 hour post-CPB in both groups. LTB4 levels increased slightly with MUF. ET-1 levels increased during and post-CPB and were unaffected by MUF. MUF does not appear to have a significant effect on post-CPB levels of TXB2, ET-1, and LTB4. Therefore, the improved hemodynamics observed with MUF do not appear to be related to removal of these cytokines.

Effects of cyanosis and hypothermic circulatory arrest on lung function in neonatal lambs

BACKGROUND

Lung function is often impaired after cardiac surgery and cardiopulmonary bypass (CPB), particularly in chronically cyanotic patients. This study aimed to evaluate lung function in a surgically created chronic cyanotic neonatal lamb model after CPB and deep hypothermic circulatory arrest (DHCA) and to assess the role of nitric oxide (NO) in the pathogenesis of increased pulmonary vascular resistance.

METHODS

A chronic cyanosis model was surgically created in 7 lambs (4.7+/-0.8 days old) by anastomosing the pulmonary artery (PA) to the left atrium (LA). Another 7 lambs underwent a sham operation (control). One week later, the animals underwent shunt takedown and CPB with 90 minutes of DHCA at 18 degrees C. Cardiac index (CI), pulmonary vascular resistance index (PVRI), lung dynamic compliance (Cdyn), alveolar-arterial oxygen difference (AaDO2), left atrial plasma nitrate/nitrite (NO metabolites) levels, and pulmonary cGMP production (concentration difference between LA and PA) were measured before CPB and at 1 and 2 hours after reperfusion.

RESULTS

The cyanosis model consistently produced significantly lower arterial oxygen tension (34.8+/-2.3 vs 93.1+/-8.8 torr in control, p < 0.001) and Qp/Qs (0.6+/-0.1 vs 1.0+/-0.0 in control, p < 0.001) than controls. Postoperative PVRI was significantly lower in the cyanosis group than in controls, although CPB with DHCA significantly elevated PVR in both cyanotic and control animals. There were no significant differences in AaDO2 and Cdyn after CPB between groups. The level of NO metabolites did not change before or after CPB in either cyanotic or acyanotic animals. NO metabolite levels tended to be higher in the cyanotic animals (p = 0.08). There was no significant difference in pulmonary cGMP production between both groups.

CONCLUSIONS

These findings suggest that CPB with DHCA, per se, does not affect NO production in cyanotic or acyanotic neonatal lambs but causes increased PVR in both groups. Chronic cyanosis does not result in reduced pulmonary function after CPB with DHCA, and is associated with lower PVR. The mechanism may involve an increased NO production in cyanotic animals.

Time course of endothelin-1 and adrenomedullin after the Fontan procedure

BACKGROUND

The endothelium-derived vasoconstrictor endothelin (ET)-1 might contribute to the physiology of blood flow regulation and play a role in cardiovascular disease. Adrenomedullin (AM) is a potent vasodilator peptide that has major effects on cardiovascular function and has multiple biologic effects involved in cardiovascular homeostasis. Although pulmonary vascular resistance is known to be one of the most important factors to determine the indications for a Fontan procedure, the time course of the plasma cytokine before and after the Fontan procedure is not known.

METHODS

Sixteen patients were divided into two groups, 8 patients (1 to 14 years) who had the Fontan procedure (atriopulmonary connection) and 8 age-matched controls who had biventricular repair with normal central venous pressure. Plasma ET-1 and adrenomedullin levels were measured in both groups immediately before cardiopulmonary bypass, immediately after cardiopulmonary bypass, and 6 and 24 hours after cardiopulmonary bypass. A thermodilution catheter was inserted during the operation, and mean pulmonary arterial pressure, pulmonary wedge pressure, and cardiac output were measured, and pulmonary vascular resistance was calculated at the same time points. Correlation between the plasma ET-1 levels and pulmonary vascular resistance data were obtained in the Fontan group.

RESULTS

Plasma ET-1 levels in the Fontan group were elevated after operation and were higher than the control group at 6 and 24 hours after cardiopulmonary bypass. Plasma adrenomedullin in the Fontan group was lower than in the control group at 6 and 24 hours after cardiopulmonary bypass. A significant positive correlation was obtained between the plasma ET-1 and pulmonary vascular resistance data (r = 0.475).

CONCLUSIONS

Imbalance between increased ET-1 and relatively decreased adrenomedullin after cardiopulmonary bypass in the Fontan procedure could contribute to dominant effects of ET-1, which might induce vasoconstriction after the Fontan procedure. ET-1 might play an important role in maintaining vasoconstriction after the Fontan procedure.

Adrenomedullin in patients at high risk for pulmonary hypertension

BACKGROUND

Adrenomedullin is a newly identified peptide with profound hypotensive effects. We investigated perioperative adrenomedullin levels among patients with congenital heart disease with and without pulmonary hypertension.

METHODS

Levels of plasma adrenomedullin, endothelin-1, and nitric oxide metabolites were measured in three groups: (1) low pulmonary flow (n=11); (2) high flow/low pulmonary arterial pressure (less than 60% systemic pressure) (n=9); and (3) high flow/high pressure (n=10). Samples were obtained preoperatively, on and off pump, and 3, 6, and 12 hours after bypass.

RESULTS

Adrenomedullin levels were highest in the low pulmonary flow group (189.7+/-15 pg/mL low flow versus 103.1+/-9.5 pg/mL high flow/low pulmonary and 139+/-17.5 pg/mL high flow/high pressure at 12 hours; p < or = 0.05). The arterial pressure/systemic pressure remained significantly lower in the high flow/low pulmonary pressure compared with the high flow/high pressure group (0.37+/-0.08 versus 0.62+/-0.11; p < 0.005). Perioperative endothelin-1 and nitric oxide levels remained low in the low pulmonary flow group but increased progressively in both high flow groups.

CONCLUSIONS

Circulating plasma adrenomedullin appears to affect baseline vascular tone in patients with intact endothelial function. It may interact with nitric oxide and endothelin-1 to help regulate blood pressure perioperatively in patients with congenital heart disease.

Dilutional and modified ultrafiltration reduces pulmonary hypertension after operations for congenital heart disease: a prospective randomized study

OBJECTIVE

A prospective randomized study was performed to test whether removal of endothelin-1, by ultrafiltration techniques, will reduce pulmonary hypertension after operations for congenital heart disease.

METHODS

Twenty-four patients with pulmonary hypertension (systolic pulmonary/systemic arterial pressure ratio > 60%) undergoing cardiac operations were randomized into a control group (n = 12) having conventional ultrafiltration and an experimental group (n = 12) undergoing dilutional ultrafiltration during and modified ultrafiltration after cardiopulmonary bypass. Plasma endothelin-1, nitric oxide metabolites, and cyclic guanosine monophosphate were assayed before bypass, 10 minutes into bypass, after bypass, and 0, 3, 6, and 12 hours after the operation in both groups, as well as in the ultrafiltrates and after modified ultrafiltration in the experimental group. Both groups received alpha-blockers (chlorpromazine and/or prazosin) postoperatively using the same guidelines.

RESULTS

The ultrafiltrates contained significant amounts of endothelin-1 (1.81 +/- 0.86 pg/ml, dilutional, and 6.44 +/- 1.82 pg/ml, modified ultrafiltrate). Endothelin-1 and the pulmonary/systemic pressure ratio were significantly lower in experimental compared with control patients. Nitric oxide metabolites and cyclic guanosine monophosphate increased similarly in both groups for 12 hours after the operation (p = not significant). Three of 12 control patients (25%) but no experimental patients had pulmonary hypertensive crises (p = 0.07). The experimental patients required significantly less ventilatory support (67 +/- 47 hours vs 178 +/- 139 hours for control patients, p = 0.048).

CONCLUSIONS

Dilutional and modified ultrafiltration reduce endothelin-1 and the pulmonary/systemic pressure ratio postoperatively and may become an important adjunct for preventing pulmonary hypertension after operations for congenital heart disease in high-risk patients.