Tissue perfusion in neonates undergoing open-heart surgery using autologous umbilical cord blood or donor blood components.

BACKGROUND: This study evaluates the hemoglobin-oxygen relationship and tissue perfusion during cardiopulmonary bypass (CPB) in neonates undergoing open-heart surgery using autologous umbilical cord blood or donor blood components. METHODS: We compared perioperative hematocrit (Hct), fetal hemoglobin (HbF), p(50)O(2), pH, pCO(2), serum lactate, duration of mechanical ventilation and intensive care unit (ICU) length of stay in neonates undergoing open-heart surgery using autologous umbilical cord blood (Group I, N=45) or donor blood components (Group II, N=65). The groups were similar with respect to diagnosis, weight, type of procedure, duration of CPB and duration of myocardial ischemia. RESULTS: Mean p(50)O(2) was significantly lower in Group I during CPB (19.7 vs. 22.3 mmHg, p=0.004) and at the end of CPB (20.1 vs. 22.8 mmHg, p=0.003). Median peak lactate during CPB was higher in Group I (4.8 vs. 2.2 mmol/l, p<0.001). Carbon dioxide tension was identified as an independent predictor of higher p(50)O(2) during CPB in Group I (ß=0.88, p=0.002), but not Group II. Bodyweight, Hct, duration of CPB, pre-CPB lactate level and pCO(2) affected peak lactate level during CPB. Although mean duration of ventilation was longer in Group II (mean 51 vs. 43, p=0.004), the groups experienced similar duration of ICU stay (5.8 vs. 5.9 days, p=0.280). CONCLUSIONS: Despite the fact that the oxyhemoglobin dissociation curve is shifted leftward in patients who receive autologous umbilical cord blood, tissue oxygen delivery appears to be preserved in neonates who undergo open-heart surgery using autologous umbilical cord blood.

Is age at initiation of extracorporeal life support associated with mortality and intraventricular hemorrhage in neonates with respiratory failure?

OBJECTIVE: To describe differences in characteristics among neonates treated with extracorporeal life support (ECLS) in the first week of life for respiratory failure compared with later in the neonatal period and to assess risk factors for central nervous system (CNS) hemorrhage and mortality among the two groups. STUDY DESIGN: Review of the Extracorporeal Life Support Organization registry from 2001 to 2010 of neonates ⩽30 days comparing two age groups: those ⩽7 days (Group 1) to those >7 days (Group 2) at ECLS initiation. RESULT: Among 4888 neonates, Group 1 (n=4453) had significantly lower mortality (17 vs 39%, P<0.001) but greater CNS hemorrhage (11 vs 7%, P=0.02) than Group 2 (n=453). Mortality and CNS hemorrhage improved significantly with increasing gestational age only for Group 1 patients. CNS hemorrhage occurred more frequently in Group 1 patients receiving venoarterial (VA) than with venovenous ECLS (15 vs 7%, P<0.001). In Group 1, lower birth weight and pre-ECLS pH and VA mode were independently associated with mortality. In Group 2, higher mean airway pressure was independently associated with mortality. Complications of ECLS therapy, including CNS hemorrhage and renal replacement therapy were independently associated with mortality for both groups. CONCLUSION: Neonates cannulated for ECLS after the first week of life had greater mortality despite lower CNS hemorrhage than neonates receiving ECLS earlier. Premature infants cannulated after 1 week had fewer CNS hemorrhages than premature infants treated with extracorporeal membrane oxygenation starting within the first week of life.

Decreased surfactant proteins in lambs with pulmonary hypertension secondary to increased blood flow.

Infants with increased pulmonary blood flow secondary to congenital heart disease suffer from tachypnea, dyspnea, and recurrent pulmonary infections. We have recently established a model of pulmonary hypertension secondary to increased pulmonary blood flow in lambs after in utero placement of an aortopulmonary vascular graft. The purpose of the present study was to utilize our animal model to determine the effects on the expression of surfactant proteins A (SP-A), B (SP-B), and C (SP-C). At age 4 wk, SP-A mRNA content in lambs decreased to 61.4 +/- 8% of age-matched control value (n = 5; P < 0.05). In addition, SP-A protein content was decreased to 50 +/- 12% of control value (n = 6; P < 0.0001). Although we did not observe statistically significant changes in SP-B mRNA content, SP-B protein was decreased to 74 +/- 25% of control value (n = 4; P < 0.02). There was no difference in SP-C mRNA. These data show that in a model of congenital heart disease with pulmonary hypertension secondary to increased pulmonary blood flow, there is a decrease in SP-A gene expression as well as a decrease in SP-A and SP-B protein contents.

Cutaneous T-cell lymphoma in a cardiac transplant recipient.

Mycosis fungoides, an uncommon form of cutaneous T-cell lymphoma, arises in the skin and frequently progresses to generalized lymphadenopathy Although the cause of cutaneous T-cell lymphoma is unknown, chronic immunosuppression may play a role. A few cases have been reported in renal transplant recipients; however, ours appears to be the 1st report of cutaneous T-cell lymphoma in a cardiac transplant recipient. In our patient, cutaneous manifestations of the disease were noted less than 1 year after transplantation. Seven years after transplantation, Sézary syndrome, a variant form of mycosis fungoides, was diagnosed by tissue biopsy and flow cytometry analysis. Photopheresis improved symptoms but was not well tolerated because of hemodynamic sequelae. Psoralen and ultraviolet A therapy also improved the patient's skin condition, but a generalized lymphadenopathy developed. The maintenance immunosuppressive regimen was changed from cyclosporine (3 mg/kg/day) and azathioprine to cyclosporine (1.5 mg/kg/day) and cyclophosphamide. Although effective in the short-term, the results of this therapeutic strategy could not be fully evaluated because the patient died of acute myocardial infarction.

Role for endothelin-1-induced superoxide and peroxynitrite production in rebound pulmonary hypertension associated with inhaled nitric oxide therapy.

Our previous studies have demonstrated that inhaled nitric oxide (NO) decreases nitric oxide synthase (NOS) activity in vivo and that this inhibition is associated with rebound pulmonary hypertension upon acute withdrawal of inhaled NO. We have also demonstrated that inhaled NO elevates plasma endothelin-1 (ET-1) levels and that pretreatment with PD156707, an ETA receptor antagonist, blocks the rebound hypertension. The objectives of this study were to further elucidate the role of ET-1 in the rebound pulmonary hypertension upon acute withdrawal of inhaled NO. Inhaled NO (40 ppm) delivered to thirteen 4-week-old lambs decreased NOS activity by 36.2% in control lambs (P<0.05), whereas NOS activity was preserved in PD156707-treated lambs. When primary cultures of pulmonary artery smooth muscle cells were exposed to ET-1, superoxide production increased by 33% (P<0.05). This increase was blocked by a preincubation with PD156707. Furthermore, cotreatment of cells with ET-1 and NO increased peroxynitrite levels by 26% (P<0.05), whereas preincubation of purified human endothelial nitric oxide synthase (eNOS) protein with peroxynitrite generated a nitrated enzyme with 50% activity relative to control (P<0.05). Western blot analysis of peripheral lung extracts obtained after 24 hours of inhaled NO revealed a 90% reduction in 3-nitrotyrosine residues (P<0.05) in PD156707-treated lambs. The nitration of eNOS was also reduced by 40% in PD156707-treated lambs (P<0.05). These data suggest that the reduction of NOS activity associated with inhaled NO therapy may involve ETA receptor-mediated superoxide production. ETA receptor antagonists may prevent rebound pulmonary hypertension by protecting endogenous eNOS activity during inhaled NO therapy.

Inhaled nitric oxide-induced rebound pulmonary hypertension: role for endothelin-1.

Clinically significant increases in pulmonary vascular resistance have been noted on acute withdrawal of inhaled nitric oxide (NO). Endothelin (ET)-1 is a vasoactive peptide produced by the vascular endothelium that may participate in the pathophysiology of pulmonary hypertension. The objectives of this study were to determine the effects of inhaled NO on endogenous ET-1 production in vivo in the intact lamb and to determine the potential role of ET-1 in the rebound pulmonary hypertension associated with the withdrawal of inhaled NO. Seven 1-mo-old vehicle-treated control lambs and six PD-156707 (an ET(A) receptor antagonist)-treated lambs were mechanically ventilated. Inhaled NO (40 parts per million) was administered for 24 h and then acutely withdrawn. After 24 h of inhaled NO, plasma ET-1 levels increased by 119.5 +/- 42.2% (P < 0.05). Western blot analysis revealed that protein levels of preproET-1, endothelin-converting enzyme-1alpha, and ET(A) and ET(B) receptors were unchanged. On acute withdrawal of NO, pulmonary vascular resistance (PVR) increased by 77.8% (P < 0.05) in control lambs but was unchanged (-5.5%) in PD-156707-treated lambs. Inhaled NO increased plasma ET-1 concentrations but not gene expression in the intact lamb, and ET(A) receptor blockade prevented the increase in PVR after NO withdrawal. These data suggest a role for ET-1 in the rebound pulmonary hypertension noted on acute withdrawal of inhaled NO.

Normalization of native heart function years after heterotopic transplantation.

We describe a patient whose native heart function has normalized several years after heterotopic heart transplantation. The native heart sustained the patient's circulation at a time when the donor heart was temporarily dysfunctional. Native heart improvement, let alone normalization, is considered rare after heterotopic transplantation but has been noted with increased frequency after long-term unloading with left ventricular assistance.

Alterations in endogenous nitric oxide production after cardiopulmonary bypass in lambs with normal and increased pulmonary blood flow.

BACKGROUND: After cardiopulmonary bypass (CPB), altered vascular reactivity is a major source of complications, particularly for children with increased pulmonary blood flow. Although changes in agonist-induced NO activity are well described after CPB, potential changes in basal NO production and their role in post-CPB pulmonary hypertension remain unclear. By using aortopulmonary vascular graft placement in the fetal lamb (shunt lambs), we established a unique model of pulmonary hypertension that mimics congenital heart disease with increased pulmonary blood flow. The objective of the present study was to investigate potential alterations in endogenous NO production after CPB in lambs with normal and increased pulmonary blood flow. METHODS AND RESULTS: Vascular pressures and blood flows were monitored in 1-month-old lambs (n=7) with increased pulmonary blood flow and 6 age-matched control lambs. After shunt closure, hypothermic CPB (25 degrees C) was performed for 2 hours. The hemodynamic variables were monitored for 4 hours after CPB. Before, during, and after CPB, peripheral lung biopsies were performed to determine tissue NO, nitrite, nitrate, and cGMP concentrations; total NO synthase (NOS) activity; and endothelial NOS protein levels. Hypothermic CPB increased both mean pulmonary arterial pressure and left pulmonary vascular resistance (P:<0.05). The increase in pulmonary arterial pressure induced in shunt lambs was greater than that induced in control lambs (P:<0.05). Four hours after CPB, tissue concentrations of NO, nitrite, nitrate, and cGMP were decreased to approximately 70% of pre-CPB levels in both control and shunt lambs (P:<0.05). Total NOS activity and endothelial NOS protein levels were unchanged. CONCLUSIONS: Modest decreases in basal NO production, the inability to increase NO production, or both may play a role in the altered pulmonary vascular reactivity after CPB. The decrease in NO is independent of gene expression. However, other mechanisms for this decrease, such as substrate or cofactor availability, warrant further study.

Left ventricular reduction in a Jehovah's Witness.

For Jehovah's Witnesses with severe heart failure, left ventricular reduction surgery may be a satisfactory alternative to cardiac transplantation. Compared with transplantation, left ventricular reduction surgery can involve less blood loss thus decreasing the need for blood-volume replacement. More importantly, left ventricular reduction surgery obviates the need for a donor organ.

Inhaled nitric oxide inhibits NOS activity in lambs: potential mechanism for rebound pulmonary hypertension.

Life-threatening increases in pulmonary vascular resistance have been noted on acute withdrawal of inhaled nitric oxide (NO), although the mechanisms remain unknown. In vitro data suggest that exogenous NO exposure inhibits endothelial NO synthase (NOS) activity. Thus the objectives of this study were to determine the effects of inhaled NO therapy and its acute withdrawal on endogenous NOS activity and gene expression in vivo in the intact lamb. Six 1-mo-old lambs were mechanically ventilated and instrumented to measure vascular pressures and left pulmonary blood flow. Inhaled NO (40 ppm) acutely decreased left pulmonary vascular resistance by 27. 5 +/- 4.7% (P < 0.05). This was associated with a 207% increase in plasma cGMP concentrations (P < 0.05). After 6 h of inhaled NO, NOS activity was reduced to 44.3 +/- 5.9% of pre-NO values (P < 0.05). After acute withdrawal of NO, pulmonary vascular resistance increased by 52.1 +/- 11.6% (P < 0.05) and cGMP concentrations decreased. Both returned to pre-NO values within 60 min. One hour after NO withdrawal, NOS activity increased by 48.4 +/- 19.1% to 70% of pre-NO values (P < 0.05). Western blot analysis revealed that endothelial NOS protein levels remained unchanged throughout the study period. These data suggest a role for decreased endogenous NOS activity in the rebound pulmonary hypertension noted after acute withdrawal of inhaled NO.

Endothelin receptor blockade prevents the rise in pulmonary vascular resistance after cardiopulmonary bypass in lambs with increased pulmonary blood flow.

BACKGROUND: Children with increased pulmonary blood flow may experience morbidity as the result of increased pulmonary vascular resistance after operations in which cardiopulmonary bypass is used. Plasma levels of endothelin-1, a potent vasoactive substance implicated in pulmonary hypertension, are increased after cardiopulmonary bypass. OBJECTIVES: In a lamb model of increased pulmonary blood flow after in utero placement of an aortopulmonary shunt, we characterized the changes in pulmonary vascular resistance induced by hypothermic cardiopulmonary bypass and investigated the role of endothelin-1 and endothelin-A receptor activation in postbypass pulmonary hypertension. METHODS: In eleven 1-month-old lambs, the shunt was closed, and vascular pressures and blood flows were monitored. An infusion of a selective endothelin-A receptor blocker (PD 156707; 1.0 mg/kg/h) or drug vehicle (saline solution) was then begun 30 minutes before cardiopulmonary bypass and continued for 4 hours after bypass. The hemodynamic variables were monitored, and plasma endothelin-1 concentrations were determined before, during, and for 6 hours after cardiopulmonary bypass. RESULTS: After 90 minutes of hypothermic cardiopulmonary bypass, both pulmonary arterial pressure and pulmonary vascular resistance increased significantly in saline-treated lambs during the 6-hour study period (P <.05). In lambs pretreated with PD 156707, pulmonary arterial pressure and pulmonary vascular resistance decreased (P <. 05). After bypass, plasma endothelin-1 concentrations increased in all lambs; there was a positive correlation between postbypass pulmonary vascular resistance and plasma endothelin-1 concentrations (P <.05). CONCLUSIONS: This study suggests that endothelin-A receptor-induced pulmonary vasoconstriction mediates, in part, the rise in pulmonary vascular resistance after cardiopulmonary bypass. Endothelin-A receptor antagonists may decrease morbidity in children at risk for postbypass pulmonary hypertension. This potential therapy warrants further investigation.

Progressive necrosis after hepatectomy and the pathophysiology of liver failure after massive resection.

BACKGROUND: Mortality after hepatectomy in rats increases markedly beyond the classic 2/3 resection from which complete recovery is the rule. Because an extremely small hepatocyte population can theoretically sustain life, we hypothesize that lethal liver failure after subtotal resection could be due to progressive injury occurring in the remnant liver. The obligatory increase in portal blood through the small remnant may be central to the pathogenesis because of sinusoidal injury and Kupffer's cell activation. To test this hypothesis an experimental study in rats was undertaken to characterize liver cell injury after lethal (85%) and nonlethal (70%) hepatectomy. METHODS: One hundred thirty Wistar rats were divided into three groups: control group (Sham laparotomy, n = 30), 70[5] hepatectomy group (n = 50), and 85% hepatectomy group (n = 50). Five rats in each group were killed for blood and liver collections from 15 minutes to day 14 after hepatectomy. Survival, histologic characteristics, serum activities of aspartate (AST) and alanine (ALT) aminotransferases and arginase were determined; serum level of tumor necrosis factor-alpha (TNF-alpha) and plasma level of prostaglandin E2 (PGE2) were measured by enzyme-linked immunosorbent assay. RESULTS: Whatever the extent of resection, hepatic injury, as demonstrated by increased serum levels of arginase, ALT, and AST, was observed. The kinetics of arginase release after hepatectomy mimicked quite well those of AST and ALT, representing a reliable marker of hepatocyte injury. A significantly higher, more prolonged blood release of enzymes was observed after 85% hepatectomy than after 70% hepatectomy. Because of a very short half-life the rise in arginase several hours after hepatectomy seems to indicate ongoing liver damage distinct from the surgical injury. Significant elevations of TNF-alpha were detected that were much more severe after 85% hepatectomy. PGE2 levels that increased significantly after 70% resection remained depressed after 8% hepatectomy. Light microscopy demonstrated extensive patchy necrosis after 85% hepatectomy. CONCLUSIONS: A pattern of progressive necrosis of the remnant liver was identified with Kupffer's cell dysfunction. We hypothesize that failure of down-regulation of TNF-alpha production by PGE2 could contribute to the pathophysiology of liver injury in the remnant after massive hepatectomy. These events may be initiated in part by the dramatic increase of portal flow through a too small remaining liver, and a pathologic mechanism may be amenable to pharmacologic manipulation.

Mechanism of cyclosporine-induced sympathetic activation and acute hypertension in rats.

Although intravenous cyclosporine A (CsA) previously has been shown to cause a robust sympathetically mediated increase in blood pressure in the rat, the underlying mechanism by which CsA increases the activity of the sympathetic nervous system is unknown. To determine the relative contributions of central neural versus peripheral reflex mechanisms in causing this sympathetic activation, we recorded efferent renal sympathetic nerve activity and blood pressure during intracerebroventricular or intravenous infusion of CsA, the latter performed in intact rats and in those with sinoaortic denervation, cervical or subdiaphragmatic vagotomy, or dorsal rhizotomy (T10 through L1). In intact rats, intravenous CsA (5 mg/kg), as expected, tripled renal sympathetic nerve activity and increased mean arterial pressure by 27 +/- 4 mm Hg (P < .05). The new findings are that this sympathoexcitatory effect of intravenous CsA (1) was not duplicated by central administration (either into the cerebroventricular system or directly onto the ventrolateral surface of the medulla), (2) was unaffected by sinoaortic denervation, but (3) was greatly attenuated by either cervical or subdiaphragmatic vagotomy or by dorsal rhizotomy. In additional experiments, we found that intravenous cyclosporine increased the multiunit activity of subdiaphragmatic but not cardiopulmonary vagal afferents. From these data, we conclude that in the rat CsA-induced increases in sympathetic activity and blood pressure are caused mainly by activation of excitatory neural reflexes arising in the subdiaphragmatic region. These reflex mechanisms use at least two different afferent neural pathways: one involving the subdiaphragmatic vagi and the other involving the low thoracic dorsal spinal roots.

Muscarinic receptor subtypes and sexual behavior in female rats.

Cholinergic muscarinic systems are involved in the regulation of female sexual behavior in rats and hamsters. This series of experiments was designed to determine whether sexual behavior in female rats is controlled preferentially by one of the traditional muscarinic receptor subtypes. Intraventricular infusion of the muscarinic antagonist scopolamine (10 micrograms bilaterally) which binds with high affinity to both M1 and M2 subtypes inhibited sexual behavior, as indicated by the incidence of lordosis, in ovariectomized rats treated with estrogen and progesterone. In contrast, the M1-selective antagonist pirenzepine failed to reduce the incidence of lordosis following intraventricular infusion (10 to 80 micrograms bilaterally). Biochemical analyses revealed that intraventricular infusion of scopolamine (10 micrograms bilaterally) inhibited both M1 and M2 binding in brain tissues while intraventricular infusion of pirenzepine (10 micrograms bilaterally) completely inhibited M1 binding without affecting M2 binding. Intraventricular infusions of the acetylcholinesterase inhibitor physostigmine (10 micrograms bilaterally), the cholinergic agonist carbachol (1 microgram bilaterally), and the muscarinic agonist oxotremorine-M (0.1 micrograms bilaterally) activated lordosis in ovariectomized females primed with low doses of estrogen. In contrast, the putative M1 agonist McN-A-343 failed to significantly increase lordosis following intraventricular infusions (1, 10, 20 micrograms bilaterally). According to biochemical results, the ability of these agents to activate lordosis in female rats was related to their affinities for M2 binding sites not M1 binding sites. In a final experiment, estrogen treatment of ovariectomized rats did not alter muscarinic subtype binding in several brain areas as measured by the M1-selective ligand [3H] pirenzepine and the M2-selective ligand [3H] oxotremorine-M. The results of these experiments confirm that muscarinic systems contribute to the regulation of lordosis in female rats and indicate that M2 binding sites rather than M1 binding sites may be a critical component of this regulation.

Cholinergic regulation of sexual behavior in female hamsters.

The effect of cholinergic manipulations on sexual behavior in female hamsters was determined in a series of experiments. The cholinergic receptor antagonist, scopolamine, reduced total lordosis duration following systemic (1 mg/kg) or intraventricular (10 and 20 micrograms bilaterally) administration to ovariectomized hamsters primed with estrogen and progesterone. The inhibitory effect of scopolamine on lordosis occurred within 15 min after either treatment route and persisted at 2 hr after systemic administration. Intraventricular administration of the acetylcholinesterase inhibitor, physostigmine (10 micrograms bilaterally), activated lordosis of short duration in ovariectomized hamsters primed only with estrogen. These results indicate that the cholinergic system plays a facilitative role in the regulation of sexual behavior in female hamsters similar to that demonstrated previously in female rats. The activational effect of cholinergic neurotransmission on female sexual behavior may be a neural mechanism common to a number of mammalian species.