Prolonged granulocyte activation, as well as hypoxanthine and free radical production after open heart surgery in children

Follistatin-like 1 and Biomarkers of Neutrophil Activation Are Associated with Poor Short-Term Outcome after Lung Transplantation on VA-ECMO

The investigation of biomarkers associated with undesired outcome following lung transplantation (LuTX) is essential for a better understanding of the underlying pathophysiology, an earlier identification of susceptible recipients and the development of targeted therapeutic options. We therefore determined the longitudinal perioperative course of putative cytokines related to neutrophil activation (chemokine CC motif ligand 4 (CCL-4), interleukin (IL)-23 and Lipocalin 2 (LCN2)) and a cytokine that has been implicated in graft-versus-host disease (Follistatin-like 1 (FSTL1)) in 42 consecutive patients undergoing LuTX. We plotted receiver-operating curves (ROC) to assess the predictive power of the measured cytokines for short-term outcomes namely primary graft dysfunction (PGD), early complications requiring extracorporeal membrane oxygenation (ECMO), and a high postoperative sequential organ failure assessment (SOFA). All cytokines increased immediately after surgery. ROC analyses determined significant associations between CCL4 and a high SOFA score (area under the curve (AUC) 0.74 (95%CI:0.5−0.9; p < 0.05), between LCN2 and postoperative ECMO support (AUC 0.73 (95%CI:0.5−0.9; p < 0.05), and between FSTL1 and PGD (AUC 0.70 (95%CI:0.5−0.9; p < 0.05). The serum concentrations of the neutrophil-derived cytokines LCN2 and CCL4 as well as FSTL1 were all related to poor outcome after LuTX. The specific predictive power, however, still has to be assessed in larger trials. The potential role of FSTL1 as a biomarker in the development of PGD could be of great interest particularly since this protein appears to play a crucial role in allograft tolerance.

Reduction of Inflammation by High-Dose Methylprednisolone Does not Attenuate Oxidative Stress in Children Undergoing Bidirectional Glenn Procedure With or Without Aortic Arch or Pulmonary Arterial Repair

OBJECTIVE

Corticosteroids attenuate an inflammatory reaction in pediatric heart surgery. Inflammation is a source of free oxygen radicals. Children with a cyanotic heart defect are prone to increased radical stress during heart surgery. The authors hypothesized that high-dose methylprednisolone reduces inflammatory reaction and thereby also oxidative stress in infants with a univentricular heart defect undergoing the bidirectional Glenn procedure.

DESIGN

A double-blind, placebo-controlled, randomized clinical trial.

SETTING

Operating room and pediatric intensive care unit of a university hospital.

PARTICIPANTS

The study comprised 29 infants undergoing the bidirectional Glenn procedure with or without aortic arch or pulmonary arterial repair.

INTERVENTIONS

After anesthesia induction, the patients received intravenously either 30 mg/kg of methylprednisolone (n = 15) or the same volume of saline as placebo (n = 14).

MEASUREMENTS AND MAIN RESULTS

Plasma interleukin-6, interleukin-8, interleukin-10 (biomarkers of inflammation), and 8-hydroxydeoxyguanosine concentrations (a biomarker of oxidative stress) were measured at the following 4 time points: preoperatively, during cardiopulmonary bypass, after protamine administration, and 6 hours postoperatively. The study parameters did not differ between the study groups preoperatively. Methylprednisolone reduced the proinflammatory cytokines interleukin-6 and interleukin-8 and increased the anti-inflammatory cytokine interleukin-10 postoperatively. Despite reduced inflammation, there were no differences in 8-hydroxydeoxyguanosine between the methylprednisolone and placebo groups.

CONCLUSIONS

The proinflammatory reaction and increase in free radical stress were not interrelated during congenital heart surgery in cyanotic infants with a univentricular heart defect undergoing the bidirectional Glenn procedure. High-dose methylprednisolone was ineffective in attenuating free radical stress.

The origin of plasma neutrophil gelatinase-associated lipocalin in cardiac surgery

Background

Acute kidney injury (AKI) is common after heart surgery. Neutrophil gelatinase-associated lipocalin (NGAL) is produced in injured kidney. NGAL has been used as an early plasma biomarker for AKI in patients undergoing heart surgery. Neutrophils contain all isoforms (25-kDa, 45-kDa and 145-kDa) but the kidney produces almost exclusively the 25-kDa isoform of NGAL. We investigated first, whether there is association between NGAL and neutrophil activation, and second whether activated neutrophils are a significant source of circulating NGAL in plasma in patients undergoing cardiac surgery.

Methods

Two separate patient cohorts were studied: 1) the “kinetic cohort” (n = 29) and 2) the “FINNAKI cohort” (n = 306). As NGAL is strictly co-localized with lactoferrin in neutrophils, NGAL and lactoferrin were measured with enzyme-linked immunosorbent assay in all patients. In sixty-one patients of the “FINNAKI cohort” Western blot was used to separate NGAL isoforms according to their molecular size. Mann-Whitney U, Kruskal-Wallis H, Pearson’s and Spearman’s tests were used as appropriate.

Results

There was strong intraoperative association between NGAL and lactoferrin at all four time-points in the “kinetic cohort”. In the “FINNAKI cohort”, NGAL and lactoferrin concentrations correlated preoperatively (R = 0.59, p < 0.001) and at admission to the intensive care unit (R = 0.69, p < 0.001). At admission to intensive care unit, concentrations of NGAL and lactoferrin were higher in AKI than in non-AKI patients (NGAL: p < 0.001; lactoferrin: p < 0.029). In Western blot analyses, neutrophil specific 45-kDa isoform (median 41% [IQR 33.3–53.1]) and mostly neutrophil derived 145-kDa isoform (median 53.5% [IQR 44.0–64.9%]) together represented over 90% of total NGAL in plasma. Potentially kidney derived NGAL isoform (25-kDa) accounted for only 0.9% (IQR 0.3 – 3.0%) of total NGAL in plasma. There were no statistically significant differences in the distribution of NGAL isomers between AKI and non-AKI patients.

Conclusions

Plasma NGAL during cardiac surgery is associated with neutrophil activation. Based on molecular size, the majority of circulating NGAL is derived from neutrophils. Neutrophil activation is a confounding factor when interpreting increased plasma NGAL in cardiac surgery.

Leucocyte filtration of residual heart-lung machine blood in children undergoing congenital heart surgery

Cardiopulmonary bypass (CPB) leads to a generalized inflammatory reaction, resulting in increased postoperative leucocyte counts and decreased pulmonary function. In adults, removal of leucocytes from the residual heart - lung machine blood after CPB improved postoperative oxygenation. In children, however, the clinical effects of leucocyte filtration of the residual heart - lung machine blood are unknown. Therefore, we measured postoperative leucocyte counts and arterial blood oxygenation in children undergoing congenital cardiac surgery in a randomized prospective study. Anaesthesia and CPB were standardized. After CPB, the residual heart-lung machine blood was collected as usual. In a group of 25 children, this blood was filtered with a leucocyte depletion filter before transfusion. A control group of 25 children received this blood unfiltered. We found that the postoperative leucocyte counts were significantly lower in the filter group than in the control group ( p=0.02, repeated measurements ANOVA). This difference reached a maximum on the second postoperative day (12.9×109/L filter versus 15.9×109/L control, p=0.02, Student’s t-test). Values for the arterial blood oxygenation on the first postoperative day were not different between the two groups (15.5±1 kPa filter versus 14.6±1.3 kPa control, p=0.57, Student’s t-test). We conclude that leucocyte filtration of the residual heart-lung machine blood reduced systemic leucocyte counts, but did not improve arterial blood oxygenation in children after congenital heart surgery.

The Effect of Methylprednisolone on Plasma Concentrations of Neutrophil Gelatinase-Associated Lipocalin in Pediatric Heart Surgery

OBJECTIVES

Plasma neutrophil gelatinase-associated lipocalin is a kidney injury marker used in pediatric heart surgery. Neutrophil gelatinase-associated lipocalin is also a constituent of specific granules of neutrophils. Corticosteroids are widely used in pediatric heart surgery. Methylprednisolone inhibits degranulation of neutrophil-specific granules. Use of corticosteroids has not been taken into account in studies of neutrophil gelatinase-associated lipocalin in pediatric heart surgery. We studied the influence of systemically administered methylprednisolone on plasma neutrophil gelatinase-associated lipocalin concentrations in pediatric heart surgery.

DESIGN

Two separate double-blinded randomized trials.

SETTING

PICU at a university-affiliated hospital.

PATIENTS

Forty neonates undergoing open-heart surgery and 45 children undergoing ventricular and atrioventricular septal defect correction.

INTERVENTIONS

First trial (neonate trial), 40 neonates undergoing open-heart surgery received either 30 mg/kg IV methylprednisolone (n = 20) or placebo (n = 20). Second trial (ventricular septal defect trial), 45 children undergoing ventricular or atrioventricular septal defect correction received one of the following: 30 mg/kg of methylprednisolone IV after anesthesia induction (n = 15), 30 mg/kg methylprednisolone in the cardiopulmonary bypass prime solution (n = 15), or placebo (n = 15).

MEASUREMENTS AND MAIN RESULTS

Plasma neutrophil gelatinase-associated lipocalin and creatinine were measured in both series. Lactoferrin levels were measured as a marker of neutrophil-specific granules in the ventricular septal defect trial only. No differences in creatinine levels occurred between the groups of either trial. Preoperative, neutrophil gelatinase-associated lipocalin did not differ between the study groups of either trial. Preoperatively administered methylprednisolone in the neonate trial reduced neutrophil gelatinase-associated lipocalin by 41% at 6 hours postoperatively (p = 0.002). Preoperatively administered methylprednisolone in the ventricular septal defect trial reduced neutrophil gelatinase-associated lipocalin by 47% (p = 0.010) and lactoferrin by 52% (p = 0.013) 6 hours postoperatively. Lactoferrin levels in the ventricular septal defect trial correlated with neutrophil gelatinase-associated lipocalin (R = 0.492; p = 0.001) preoperatively and after weaning from cardiopulmonary bypass (R = 0.471; p = 0.001).

CONCLUSIONS

Preoperatively administered methylprednisolone profoundly decreases plasma neutrophil gelatinase-associated lipocalin levels. Neutrophil gelatinase-associated lipocalin seems to originate to a significant extent from activated neutrophils. Preoperative methylprednisolone is a confounding factor when interpreting plasma neutrophil gelatinase-associated lipocalin levels as a kidney injury marker in pediatric heart surgery.

The Influence of Extracorporeal Circulation on the Susceptibility of Erythrocytes to Oxidative Stress

Extracorporeal circulation (ECC), a necessary and integral part of cardiac surgery, can itself induce deleterious effects in patients. The pathogenesis of diffuse damage of several tissues is multifactorial. It is believed that circulation of blood extracorporeally through plastic tubes causes a whole body inflammatory response and a severe shear stress to blood cells. The aim of this study was to evaluate the level of oxidative stress and its deleterious effect on red blood cell (RBC) before (pre-ECC), immediately after (per-ECC) and 24 h after an ECC (24 h post-ECC). Several indicators of extracellular oxidative status were evaluated. The ascorbyl free radical (AFR) was directly measured in plasma using electron spin resonance (ESR) spectroscopy and expressed with respect to vitamin C levels in order to obtain a direct index of oxidative stress. Allophycocyanin assay was also used to investigate the plasma antioxidant status (PAS). Indirect parameters of antioxidant capacities of plasma such as vitamin E, thiol and uric acid levels were also quantified. RBC alterations were evaluated through potassium efflux and carbonyl levels after action of AAPH, a compound generating carbon centered free radicals. No changes in plasma uric acid and thiols levels were observed after ECC. However, vitamin E levels and PAS were decreased in per-ECC and 24h post-ECC samples. Vitamin C levels were significantly lower in 24 h post-ECC and the AFR/ vitamin C ratio was increased. Differences in results had been noted when measurements took account of hemodilution. Increases of uric acid and thiols levels were observed after ECC. Vitamin E levels were not modified. However after hemodilution correction a significant decrease of vitamin C level was noted in 24 h post-ECC samples as compared to per-ECC sample. Whatever the way of measurement, vitamin C levels decreased suggesting the occurrence of ECC induced-oxidative stress. Concerning RBC, in the absence of AAPH, extracellular potassium remained unchanged between pre-, per- and 24 h post-ECC. AAPH induced a significant increase in extracellular potassium and carbonyls levels of RBC membranes, which was not modified by ECC. These results suggest the absence of alterations of RBC membrane during ECC despite the occurrence of disturbances in PAS. Such protection is of particular importance in a cell engaged in the transport of oxygen and suggests that RBC are equipped with mechanisms affording a protection against free radicals.

A validated method for rapid analysis of ethane in breath and its application in kinetic studies in human volunteers

Oxidative stress may initiate lipid peroxidation that generates ethane. Ethane, at low concentrations, is eliminated by pulmonary exhalation. Previous methods have not allowed frequent sampling, thus ethane kinetics has not been studied in man. A validated method over the range 3.8-100,000 ppb with a limit of quantitation of 3.8 ppb (CV 9.3%) based on cryofocusing technique of a 60 ml breath sample allowed frequent sampling. Due to a rapid analytical procedure batches of more than 100 samples may be analyzed. In human volunteers (24-55 years) uptake was studied for up to 23 min (n = 9), elimination was studied for 210 min (n = 9). Ethane was inhaled (concentrations varied from 16 to 29 ppm (parts per million)) through a non-rebreathing system; sampling was performed with short intervals from the expiratory limb. Samples were also drawn from the inhalatory limb. Ninety-five percent of steady state (inspired) concentration was reached within 1.75 min. Five percent of the initially inhaled concentrations was found in exhaled air 1.5 min after termination of inhalation. A terminal mean half life of 31 min for ethane was also observed. The data indicate that frequent sampling will be necessary to capture relevant changes in breath ethane.

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.

Perioperative determinants and outcome of cardiopulmonary arrest in children after heart surgery

OBJECTIVES

To identify perioperative factors associated with postoperative cardiopulmonary arrest (CA) in the pediatric intensive care unit (PICU) in children undergoing cardiovascular surgery, and to report the outcome of cardiopulmonary resuscitation (CPR) in these patients.

METHODS

We reviewed the medical records of all patients under 16 years of age who had undergone cardiovascular surgery and sustained CA in PICU in an urban, tertiary care children's hospital over a 5-year period. We used two control groups of patients who recovered without CA. (1) Sixty-five patients, who were operated under deep hypothermic circulatory arrest (DHCA) during the study period. (2) All patients who underwent repair of congenital heart lesions without DHCA in 1994 (n=278).

RESULTS

Eighty-two children experienced CA during postoperative care in PICU, mainly from cardiovascular causes. Thirty-four (41%) were declared dead without attempted resuscitation, CPR was initiated in 48 (59%). The primary survival rate was 56% and 1 year survival rate was 19%. The incidence of CA was 3.6% for closed heart operations, 4.9% for intra-cardiac surgery without DHCA, and 27% for operations involving DHCA. Thirty-three per cent of patients with CA arrested during the first 24 postoperative h. Preoperative mechanical ventilation (P=0.03), prostaglandin E1 (P=0.001) and inotropic support (P=0.04) were given significantly more frequently to patients who postoperatively required CPR, compared to control groups. Patients in whom CPR was attempted were younger than the 1994 controls (0.4 vs. 1.2 years; P<0.04), had longer mean aortic-cross-clamp times (76 vs. 51 min; P<0.0001) and cardiopulmonary bypass times (124 vs. 85 min; P<0.0002), and required more inotropic support upon leaving the operating room (P<0.0001). Patients who received CPR had significantly longer DHCA times (53 vs. 32 min; P<0.0002) and required more inotropic support than patients in the DHCA control group (P<0.002).

CONCLUSIONS

CA after pediatric cardiac surgery is associated with repair of complex congenital heart anomalies in patients who require preoperative mechanical ventilation and vasoactive agents, prolonged aortic cross-clamp, circulatory arrest; and heavy postoperative inotropic support.

Reperfusion injury after focal myocardial ischaemia: polymorphonuclear leukocyte activation and its clinical implications

The only way to rescue ischaemic tissue is to re-instate the oxygen supply to the tissue. However reperfusion of the ischaemic area not only oxygenates the tissue but also initiates a cascade of processes, which may in some cases result in temporary dysfunction of the myocardium. In order to devise protective measures, it is essential to understand the mechanisms and the triggers of this reperfusion phenomenon. In this review we will mainly focus on the inflammatory response caused by reperfusion. We will cover the different steps of polymorphonuclear leukocyte activation and will briefly discuss the molecular biology of the receptors involved. The currently used pharmacological medications in acute cardiology will be reviewed and in particular their actions on polymorphonuclear leukocyte activation, adhesion and degranulation. This review is a compilation of the current knowledge in the field and the therapeutic progress in the prevention of reperfusion injury made today.

Delayed impairment of cerebral oxygenation after deep hypothermic circulatory arrest in children

BACKGROUND

Clinical studies of deep hypothermic circulatory arrest (DHCA) have focused only on the immediate postoperative period. However, experimental findings suggest impairment of cerebral oxygenation at 2 to 8 hours after reperfusion.

METHODS

In 10 children who had DHCA for heart operations, transcerebral differences of hemoglobin oxygen saturation and plasma hypoxanthine, xanthine, and lactoferrin concentrations were measured in concurrently obtained cerebral venous, arterial, and mixed venous samples up to 10 hours postoperatively.

RESULTS

Compared with preoperative levels (57% +/- 7%), cerebral venous oxygen saturation was not significantly reduced until 2 hours (44% +/- 6%) and 6 hours (42% +/- 5%) after DHCA (p < 0.05). A statistically significant transcerebral (ie, cerebral vein versus artery) concentration difference of hypoxanthine was observed at 30 minutes (3.6 +/- 0.9 micromol/L), 1 hour (3.4 +/- 1.1 micromol/L), and 2 hours (3.1 +/- 0.8 micromol/L) after DHCA but not preoperatively (0.4 +/- 0.2 micromol/L). A transcerebral concentration difference of lactoferrin occurred 30 minutes after DHCA (196 +/- 70 microg/mL) but not preoperatively (16 +/- 20 microg/mL).

CONCLUSIONS

Cerebral venous oxygen saturation of hemoglobin decreased as late as 2 to 6 hours after DHCA, in association with impaired cerebral energy status. Neutrophil activation in the cerebral circulation occurred 30 minutes after reperfusion.