Regional generation of free oxygen radicals during cardiopulmonary bypass in children

Prediction of mechanical ventilation outcome by early abdominal-visceral-blood-flow-and-function score in critically ill patients after cardiopulmonary bypass in the ICU: A prospective observational study

Background

Abdominal organs are important organs that sense and respond to ischemia and hypoxia, but there are few evaluation methods.We use ultrasonography to evaluate abdominal organ function and blood flow in patients with mechanical ventilation (MV) after cardiopulmonary bypass and to obtain a semiquantitative score for abdominal organ function and blood flow.

Methods

Patients with cardiopulmonary bypass in the Critical Care Department of Peking Union Medical College Hospital in China from March to July 2021 were enrolled in this prospective observational study. The correlation of the abdominal-visceral-blood-flow-and-function score (AVBFS) with the duration of MV, number of days spent in the intensive care unit (ICU), acute physiology and chronic health evaluation II (APACHE-II), sequential organ failure assessment (SOFA), lactate, epinephrine, and norepinephrine use was analyzed, and the results were used to assess the predictive value of the receiver operating characteristic curve (ROC) regression analysis score for the duration of MV.

Results

Of the 92 patients who underwent cardiopulmonary bypass, 41 were finally included. The AVBFS were significantly correlated with the duration of MV, number of days spent in the ICU, APACHE-II score, SOFA score, and norepinephrine use time. The AVBFS in a group of patients using ventilators ≥36 h were significantly higher than those obtained for a group of patients using ventilators <36 h (P <0.05). The evaluation results for the AVBFS at 0-12 h after ICU admission were as follows: area under the ROC curve (AUC)=0.876 (95% confidence interval [CI]: 0.767 to 0.984), cut-off value=2.5, specificity=0.842, and sensitivity=0.773.

Conclusions

Abdominal visceral organ function and blood perfusion can be used to evaluate gastrointestinal function. It is related to early and late extubation after cardiac surgery.

Effect of Pyrazinamide and Probenecid on Peritoneal Urate Transport Kinetics during Continuous Ambulatory Peritoneal Dialysis

Objective

We administered pyrazinamide (PZA) and probenecid (PB) — two well-known modulators of urate transport via the proximal tubules — to evaluate their impact on urate transport through the peritoneal membrane and to clarify mechanisms affecting peritoneal transport.

Setting

A continuous ambulatory peritoneal dialysis (CAPD) unit in 2nd Hospital of IKA (Social Services Institute), Greece.

Patients

In 20 stable CAPD patients, on the study day, a 4-hour, 2-L, 1.36% glucose exchange was performed (control exchange). Pyrazinamide 3 g was given orally and another identical exchange was performed (study exchange). The same protocol was repeated with 2 g PB. Kt/V, peritoneal clearances of urea, creatinine, and urate for each exchange, and mass transfer area coefficients (MTAC) for the three solutes and their dialysate-to-plasma concentration (D/P) ratios were used to estimate peritoneal transport.

Results

Administration of PZA resulted in decreased clearances and MTAC values for the three solutes. The D/P ratio decreased significantly only for urate, indicating a more intense influence of PZA on urate. After PB administration, clearances of urea, creatinine, and urate were increased. MTAC and D/P ratio increased significantly only for urate ( p < 0.05), demonstrating an action similar to that exerted on renal tubules.

Conclusions

These findings provide evidence that unrestricted diffusion is not the only transport mechanism in the case of urate, and demonstrate the existence of an active mechanism in peritoneal urate transport with a reabsorptive and, probably, a secretive component that resembles that of renal tubule urate transport. Attention should be given in the case of CAPD patients undergoing antituberculous (PZA) treatment: it might have a negative impact on urea, creatinine, and urate peritoneal transport rates.

Perioperative management of low birth weight infants for open-heart surgery

Infants of birth weight ≤2500 g are termed low birth weight (LBW). These children often have considerable morbidity from prematurity and intra-uterine growth restriction. Additionally, LBW infants have increased risk for cardiac and noncardiac congenital anomalies and may require surgery. Primary rather than palliative surgical repair of cardiac lesions has been preferred in recent years. However, LBW remains a risk factor for increased mortality and morbidity after open-heart surgery (OHS). There is a paucity of information about the anesthetic challenges presented by LBW infants undergoing OHS. This review summarizes the perioperative issues of relevance to anesthesiologists who manage these high-risk patients. Emphasis is placed on management concerns that are unique to LBW infants. Retrospective data from the authors' institution are provided for those aspects of anesthetic care that lack published studies. Successful outcome often requires substantial hospital resources and collaborative multi-disciplinary effort.

Preterm infants with congenital heart disease and bronchopulmonary dysplasia: postoperative course and outcome after cardiac surgery

OBJECTIVE

Success in treatment of premature infants has resulted in increased numbers of neonates who have bronchopulmonary dysplasia (BPD) and require surgical palliation or repair of congenital heart disease (CHD). We sought to investigate the impact of BPD on children with CHD after heart surgery.

METHODS

This was a retrospective, multicenter study of patients who had BPD, defined as being oxygen dependent at 28 days of age with radiographic changes, and CHD and had cardiac surgery (excluding arterial duct ligation) between January 1991 and January 2002. Forty-three infants underwent a total of 52 cardiac operations. The median gestational age at birth was 28 weeks (range: 23-35 weeks), birth weight was 1460 g (range: 431-2500 g), and age at surgery was 2.7 months (range: 1.0-11.6 months). Diagnoses included left-to-right shunts (n = 15), conotruncal abnormalities (n = 13), arch obstruction (n = 6), univentricular hearts (n = 4), semilunar valve obstruction (n = 3), Shone syndrome (n = 1), and cor triatriatum (n = 1).

RESULTS

Thirty-day survival was 84% with 6 early and 6 late postoperative deaths. Survival to hospital discharge was 68%. There was 50% mortality for patients with univentricular hearts and severe BPD. The median duration of preoperative ventilation was 76 days (range: 2-244 days) and of postoperative ventilation was 15 days (range: 1-141 days). The median duration of cardiac ICU stay was 7.5 days (range: 1-30 days) and of hospital stay was 115 days (range: 35-475 days). Current pulmonary status includes on room air (n = 14), O2 at home (n = 4), and ventilated at home (n = 4) or in hospital (n = 4), and 5 patients were lost to follow-up.

CONCLUSIONS

BPD has significant implications for children who have CHD and undergo cardiac surgery, leading to prolonged ICU and hospital stays, although most survivors are not O2 dependent. Postoperative mortality was highest among patients with univentricular hearts and severe BPD. Optimal timing of surgery and strategies to improve outcome remains to be delineated.

Poly(ADP-ribose) polymerase inhibitor PJ-34 reduces mesenteric vascular injury induced by experimental cardiopulmonary bypass with cardiac arrest

The aim of this study was to investigate effects of poly(ADP-ribose) polymerase (PARP) inhibition on mesenteric vascular function and metabolism in an experimental model of cardiopulmonary bypass (CPB) with cardiac arrest. Twelve anesthetized dogs underwent 90-min hypothermic CPB. After 60 min of cardiac arrest, reperfusion was started for 40 min following application of either saline vehicle (control, n = 6) or a potent PARP inhibitor, PJ-34 (10 mg/kg iv bolus and 0.5 mg.kg(-1).min(-1) infusion for 20 min, n = 6). PJ-34 led to better recovery of cardiac output (2.2 +/- 0.1 vs. 1.8 +/- 0.2 l/min in control) and mesenteric blood flow (175 +/- 38 vs. 83 +/- 4 ml/min, P < 0.05 vs. control) after reperfusion. The impaired vasodilator response of the superior mesenteric artery to acetylcholine, assessed in the control group after CPB (-32.8 +/- 3.3 vs. -57.6 +/- 6.6% at baseline, P < 0.05), was improved by PJ-34 (-50.3 +/- 3.6 vs. -54.3 +/- 4.1% at baseline, P < 0.05 vs. control). Although plasma nitrate/nitrite concentrations were not significantly different between groups, mesenteric nitric oxide synthase activity was increased in the PJ-34 group (P < 0.05). Moreover, the treated group showed a marked attenuation of mesenteric venous plasma myeloperoxidase levels after CPB compared with the control group (75 +/- 1 vs. 135 +/- 9 ng/ml, P < 0.05). Pharmacological PARP inhibition protects against development of post-CPB mesenteric vascular dysfunction by improving hemodynamics, restoring nitric oxide production, and reducing neutrophil adhesion.

Influence of steroids on microvascular perfusion injury of the bowel induced by extracorporeal circulation

BACKGROUND

Extracorporeal circulation is associated with gastrointestinal complications. By means of intravital microscopic methods, we investigated whether preoperative treatment with steroids can attenuate the impairment of the bowel microcirculation.

METHODS

In 20 pigs, a partial left heart bypass (pLHB) was established. A loop of the terminal ileum was exteriorized for intravital-microscopic observation. Seven sham-operated animals served as controls. In 13 animals, pLHB was established for 2 hours with a flow rate of 2,000 mL per minute; 7 of the animals received 20 mg/kg body weight prednisolone preoperatively. The microcirculatory network was analyzed before, during pLHB, and 2 hours after bypass.

RESULTS

Despite unchanged macro-hemodynamics, pLHB resulted in a significant microvascular perfusion injury of the small bowel. Arteriolar vasoconstriction and a reduction of perfused capillaries per unit area (functional capillary density) to 30% of prebypass values could be found. Blood cell velocities were reduced in submucuous collecting venules. In the steroid-treated animals, the functional capillary density remained normal. In addition, arteriolar vasoconstriction could be prevented.

CONCLUSIONS

Treatment with prednisolone largely prevents the microcirculatory alterations in the small bowel induced by extracorporeal circulation.

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.

Oxygen free radical generation in healthy blood donors and cardiac patients: the protective effect of allopurinol

Cardiopulmonary bypass (CPB) activates the complement system, which leads to granulocyte activation and free radical production. Free radical activity during CPB has been associated with myocardial dysfunction. However, the relationship between cardiac enzymes and granulocytes to lipid peroxidation in cardiac surgery patients is unknown. Moreover, the effect of allopurinol on lipid peroxidation during mechanical trauma has to be explored. Thirty-four patients undergoing coronary bypass surgery and 26 healthy blood donors participated in this prospective study where granulocyte counts, cardiac enzymes and malondialdehyde (MDA) were measured and related. Allopurinol was used ex vivo, as scavenger, to explore its effect on lipid peroxidation. In the patient group, the mean preoperative MDA level (2.2 +/- 0.7, nmol/ml) significantly increased after 30 min of bypass (3.3 +/- 0.9 nmol/ml; p < 0.0001), and showed a second peak at aortic declamping (4.1 +/- 0.9 nmol/ml). There were significant correlations between MDA and granulocyte counts (r = 0.59, p < 0.0001) and cardiac enzymes (r = 0.55, p < 0.0001). In an ex vivo setting, further mechanical trauma to blood significantly increased the MDA levels, both in the control (p < 0.0001) and in the patient group (p < 0.0001) and this effect could be reduced by allopurinol (p < 0.0001). CPB and mechanical trauma generate oxygen free radicals. Allopurinol was found to reduce lipid peroxidation of red cells following mechanical trauma and this has to be further investigated regarding its ability to reduce morbidity in patients undergoing open heart surgery.

Mechanisms of brain injury during infant cardiac surgery

Neurological injury is a major and often debilitating complication of congenital heart disease and open-heart surgery. Paradoxically, the full impact of this complication has been underscored by the marked decrease in mortality and the rescue of infants with desperate and previously lethal heart conditions. Although recent focus has been on mechanisms of brain injury originating during open-heart surgery, this article also emphasizes the importance of mechanisms initiated or perpetuated during the preoperative and postoperative periods. In addition to the usually implicated mechanism of hypoxia-ischemia, recent genetic advances suggest an important role for genetic deletion syndromes. Inflammatory cascades have been implicated in the end-organ injury seen after cardiopulmonary bypass and might play a role in neurological dysfunction. These mechanisms are reviewed, with an emphasis on recent developments in our understanding of brain injury in this population.

Inflammatory response to cardiopulmonary bypass: mechanisms involved and possible therapeutic strategies

BACKGROUND

Recent study of the inflammatory reactions occurring during and after cardiopulmonary bypass (CPB) has improved our understanding of the involvement of the inflammatory cascade in perioperative injury. However, the exact mechanisms of this complex response remain to be fully determined.

METHODS

Literature on the inflammatory response to CPB was reviewed to define current knowledge on the possible pathways and mediators involved, and to discuss recent developments of therapeutic interventions aimed at attenuating the inflammatory response to CPB.

RESULTS

CPB has been shown to induce complement activation, endotoxin release, leukocyte activation, the expression of adhesion molecules, and the release of many inflammatory mediators including oxygen-free radicals, arachidonic acid metabolites, cytokines, platelet-activating factor, nitric oxide, and endothelins. Therapies aimed at interfering with the inflammatory response include the administration of pharmacologic agents such as corticosteroids, aprotinin, and antioxidants, as well as modification of techniques and equipment by the use of heparin-coated CPB circuits, intraoperative leukocyte depletion, and ultrafiltration.

CONCLUSIONS

Improved understanding of the inflammatory reactions to CPB can lead to improved patient outcome by enabling the development of novel therapies aimed at limiting this response.

[Reperfusion arrhythmias in valvular patients undergoing extracorporeal surgery and pretreated with captopril]

INTRODUCTION AND OBJECTIVES

After the ischemia-reperfusion process in extracorporeal cardiac surgery there are, among several phenomena, some reperfusion arrhythmias which are influenced by a varied series of mechanisms. These arrhythmias have been related to the release of oxygen-derived free radicals during the first moments of reperfusion. Thus, a previous administration of free-radical scavengers might be beneficial, among which captopril has been included with good results in human studies in vitro and in animals in vivo. The aim of this study was to evaluate the influence of pretreatment with captopril on the prevention of reperfusion arrhythmias in patients undergoing valvular cardiac surgery.

METHODS

30 patients were randomly allocated to pretreatment with either captopril (CTP group, n = 15) or without captopril (CON group, n = 15). Exclusion criteria (left ventricular ejection fraction < 40%, evidence of angiographic coronary disease, prior myocardial infarction and preoperatory myocardial infarction). The dose of captopril administered was 12.5 mg every 8 hours orally, from 24 hours before surgery. A Holter register was used to analyze the ventricular arrhythmias (extrasystoles, salvos, tachycardia and fibrillation) during the first hour of reperfusion. The need for cardioversion was examined and the number of shocks needed. These events were related to changes in blood analyses from coronary sinus samples to determine creatine phosphokinase, activity of the angiotensin converting enzyme and cyclic adenosine monophosphate, before aortic clamping and after the heart was rewarmed.

RESULTS

No significant differences were found in the number of ventricular arrhythmias. 60% of the patients with captopril and only 40% of the patients without it (non significant) had spontaneous defibrillation without electric shock; in those cases in which it was necessary, the number of shocks was less in the captopril group (p < 0.05). Excepting the significant correlation (p < 0.01) that we have found between ventricular fibrillation and the cyclic adenosine monophosphate increase, there is no significant correlation between the other arrhythmias and the analytical data studied.

CONCLUSIONS

These data suggest that captopril, given before cardiac surgery, has little or no protector effect on reperfusion ventricular arrhythmias in extracorporeal cardiac surgery, though in patients treated with captopril there is a greater possibility of spontaneous defibrillation and fewer shocks necessary for defibrillation, without negative effects.