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Biomedical subjects

R D Siewers

Publications and source records attributed to R D Siewers.

At least 19 recordsLinked to original sources
PubMed2001

Regional low-flow perfusion provides somatic circulatory support during neonatal aortic arch surgery.

BACKGROUND: Regional low-flow perfusion has been shown to provide cerebral circulatory support during neonatal aortic arch operations. However, its ability to provide somatic circulatory support remains unknown. METHODS: Fifteen neonates undergoing arch reconstruction with regional perfusion were studied. Three techniques were used to assess somatic perfusion: abdominal aortic blood pressure, quadriceps blood flow (near-infrared spectroscopy), and gastric tonometry. RESULTS: Twelve patients required operation for hypoplastic left heart syndrome, and 3 required arch reconstruction with a biventricular repair. There was one death (7%). Abdominal aortic blood pressure was higher (12+/-3 mm Hg versus 0+/-0 mm Hg), and quadriceps blood volumes (5+/-24 versus -17+/-26) and oxygen saturations (57+/-25 versus 33+/-12) were greater during regional perfusion than during deep hypothermic circulatory arrest (p < 0.05). During rewarming, the arterial-gastric mucosal carbon dioxide tension difference was lower after circulatory arrest than after regional perfusion (-3.3+/-0.3 mm Hg versus 7.8+/-7.6 mm Hg, p < 0.05). CONCLUSIONS: Regional low-flow perfusion provides somatic circulatory support during neonatal arch surgical procedures. Support of the subdiaphragmatic viscera should improve the ability of neonates to survive the postoperative period.

Aorta, Abdominal↗
PubMed2001

Aortopulmonary size discrepancy is not a contraindication to the pediatric Ross operation.

BACKGROUND: Modification of the aortic annulus or the ascending aorta, or both, may be required in pediatric patients undergoing the Ross operation. The fate of these autografts remains uncertain. METHODS: Retrospective review of 15 patients undergoing Ross operation without aortic annular modification (group 1), 11 patients requiring annular reduction (group 2, n = 11), and 8 patients requiring annular enlargement (group 3, n = 8). Autograft function and dimensions were evaluated by echocardiography. RESULTS: Autograft insufficiency was less than or equal to mild in 33 patients and moderate in 1 patient. The annulus body surface area ratio increased in group 1 from 19.7 +/- 5 to 20.3 +/- 5 mm/M2 (p = 0.8). The average annular reduction in group 2 was 5 +/- 1.5 mm, and 10 of 11 patients required reduction of the ascending aorta (mean 11 +/- 5 mm). The annulus body surface area ratio increased from 18.6 +/- 7 to 20.5 +/- 9 mm/M2 (p = 0.2). The mean augmentation in annulus diameter in group 3 was 6 +/- 4 mm; the annulus body surface area ratio decreased from 23.7 +/- 14 to 20.3 +/- 8 mm/M2 (p = 0.5). CONCLUSIONS: We continue to offer the Ross operation to pediatric patients even when aortic annular or ascending aortic size discrepancies mandate surgical modifications.

Adolescent↗
PubMed2001

Hypothermic cardiopulmonary bypass alters oxygen/glucose uptake in the pediatric brain.

OBJECTIVES: Neurologic morbidity related to cardiac surgery has been recognized as a major morbidity. A variety of causes related to cardiopulmonary bypass, including microemboli, nonpulsatile flow, hemodilution, and inflammatory mediation, have been proposed. Because oxygen and glucose are the predominant metabolic substrates for the brain, we sought to examine the uptake of these substrates by the pediatric brain during hypothermic cardiopulmonary bypass. METHODS: Eleven children (median age 5 months, range 1 day-17 years) undergoing a variety of cardiac surgical procedures with the use of hypothermic cardiopulmonary bypass were studied. Cerebral arteriovenous differences for oxygen, glucose, and lactate were obtained before, during, and after bypass. On the basis of the predictable stoichiometric relationship for the oxidation of glucose, the relationship of substrate uptake was expressed as the oxygen/glucose index.Oxygen/glucose index (%) = (arteriovenous oxygen difference [micromol/mL]/arteriovenous glucose difference [micromol/mL] x 6) x 100 RESULTS: All children survived with no obvious neurologic sequelae. During cooling on cardiopulmonary bypass, the oxygen/glucose indexes fell significantly from prebypass values (53% +/- 19% at 28 degrees C and 54% +/- 25% at 24 degrees C vs 117% +/- 70%; P <.05, analysis of variance). This decline resulted from decreased oxygen uptake with stable glucose uptake (P <.05). Although oxygen and glucose uptake both increased with rewarming, the net effect was only a slight increase in oxygen/glucose index (62% +/- 16%). Postbypass oxygen/glucose index exceeded prebypass values (149% +/- 83%). CONCLUSIONS: Hypothermic cardiopulmonary bypass alters the relationship between oxygen and glucose uptake in the pediatric brain. The relationship of these findings to bypass-related neurologic morbidity remains to be explored.

Adolescent↗
PubMed2000

Management of retroperitoneal arterial injury after heart catheterization in children.

With the expansion of interventional cardiology into the pediatric population, vascular complications related to cardiac catheterization can be expected to occur. Cardiac surgeons must be prepared to treat these life-threatening injuries. We present a case and detail the technique of the surgical management of retroperitoneal arterial injury after interventional cardiac catheterization in a 6-month-old boy.

Aortic Diseases↗
PubMed2000

Regional low-flow perfusion provides cerebral circulatory support during neonatal aortic arch reconstruction.

OBJECTIVE: Because of concerns regarding the effects of deep hypothermia and circulatory arrest on the neonatal brain, we have developed a technique of regional low-flow perfusion that provides cerebral circulatory support during neonatal aortic arch reconstruction. METHODS: We studied the effects of regional low-flow perfusion on cerebral oxygen saturation and blood volume as measured by near-infrared spectroscopy in 6 neonates who underwent aortic arch reconstruction and compared these effects with 6 children who underwent cardiac repair with deep hypothermia and circulatory arrest. RESULTS: All the children survived with no observed neurologic sequelae. Near-infrared spectroscopy documented significant decreases in both cerebral blood volume and oxygen saturations in children who underwent repair with deep hypothermia and circulatory arrest as compared with children with regional low-flow perfusion. Reacquisition of baseline cerebral blood volume and cerebral oxygen saturations were accomplished with a regional low-flow perfusion rate of 20 mL x kg(-1) x min(-1). CONCLUSIONS: Regional low-flow perfusion is a safe and simple bypass management technique that provides cerebral circulatory support during neonatal aortic arch reconstruction. The reduction of deep hypothermia and circulatory arrest time required may reduce the risk of cognitive and psychomotor deficits.

Aorta, Thoracic↗
PubMed1999

Technique for repair of single-ventricle hearts with transposition of the great arteries and aortic arch hypoplasia.

We describe a modified technique of aortopulmonary anastomosis for palliative repair of hearts with a single left ventricle, a rudimentary right ventricle, transposition of the great vessels, and a hypoplastic aortic arch. This procedure creates an unobstructed left ventricular outflow tract and avoids the problems of spiral patch grafting and multiple patch enlargements of the ascending aorta and arch.

Aorta, Thoracic↗
PubMed1999

The effects of cardiopulmonary bypass on remifentanil kinetics in children undergoing atrial septal defect repair.

UNLABELLED: Cardiopulmonary bypass (CPB) can greatly influence the pharmacokinetics of opioids. This study investigated the pharmacokinetic profile of remifentanil in 12 pediatric patients undergoing CPB for repair of an atrial septal defect. All patients received remifentanil (5 microg/kg) over 1 min into a peripheral vein both before the onset of CPB and after the discontinuation of CPB. Arterial blood samples were obtained at defined time periods, and remifentanil concentration was determined using high-performance liquid chromatography ultraviolet detection. The pharmacokinetic profiles both before and after bypass were determined in all 12 patients. There was no change in the volume of distribution at steady state, the volume of the central compartment, or the alpha- and beta-elimination half-life. Although the clearance values increased 20% in the postbypass period (from 38.7 +/- 9.6 to 46.8 +/- 14 mL x kg(-1) x min(-1), there was no meaningful change in the coefficient of variation (from 25% to 30%). IMPLICATIONS: After cardiopulmonary bypass the clearance of remifentanil increases in children. However, the relative lack of change in the coefficient of variation suggests that remifentanil should be a predictable drug in the postcardiopulmonary bypass period.

Adolescent↗
PubMed1995

Coronary vasoconstriction mediated by endothelin-1 in neonates. Reversal by nitroglycerin.

To determine the role of the vasoconstrictor peptide endothelin-1 in cardiopulmonary bypass in neonates, we measured plasma endothelin-1 concentrations in infants before and after cardiopulmonary bypass for arterial switch procedures and studied the effects of endothelin-1 on coronary tone and contractility in normal and reperfused neonatal pig hearts. Endothelin-1 blood concentrations (picograms per milliliter, mean +/- standard error) were significantly higher in neonates with arterial transposition and in umbilical venous blood (22.9 +/- 2.3 and 19.2 +/- 2.9, respectively) than in older children with atrial septal defects (13.2 +/- 1.6) or in healthy adults (10.7 +/- 2.5). After cardiopulmonary bypass, endothelin-1 concentrations increased 29% in neonates undergoing arterial switch procedure and 28% in children undergoing atrial septal defect repair (p < 0.05 versus before bypass). In isolated, blood-perfused neonatal pig hearts, endothelin-1 had dose-related coronary constrictor and inotropic effects between 25 and 100 pmol. Endothelin-1 concentrations that did not increase coronary perfusion pressure (5 to 10 pmol) caused significant coronary constriction in the presence of norepinephrine (10 nmol/L). During reperfusion after 30 minutes of global normothermic ischemia, the coronary vasoconstrictor effects of both endothelin-1 alone and endothelin-1 plus norepinephrine were significantly enhanced. Nitroglycerin reversed vasoconstriction produced by endothelin-1 and endothelin-1 plus norepinephrine both before and after ischemia-reperfusion. We conclude that endothelin-1 concentrations are significantly elevated in neonates and are further increased after cardiopulmonary bypass. Coronary vasoconstriction caused by endothelin-1 is enhanced by ischemia-reperfusion and by norepinephrine present in concentrations typically observed after neonatal cardiopulmonary bypass. Nitroglycerin reverses coronary vasoconstriction induced by endothelin-1 and may therefore be beneficial in the postoperative management of neonates after cardiac operations.

Adult↗
PubMed1994

Transatrial lead placement for endocardial pacing in children.

Transvenous placement of endocardial leads in children may be difficult due to restrictions and complications of vascular access. We have placed endocardial leads from a transatrial approach in 5 children with various cardiac malformations. The usual surgical approach involved an anterolateral thoracotomy and, under fluoroscopic guidance, passage of the lead tip directly through the right atrial wall and across the tricuspid valve to the apex of the right ventricle. At a mean follow-up time of 23.2 months (range, 12.0 to 27.9 months), all patients have low thresholds for myocardial capture, and there have been no complications. We conclude that placement of endocardial leads by a transatrial approach provides an excellent alternative to an epicardial system in children destined for lifelong pacing.

Cardiac Pacing, Artificial↗
PubMed1994

Extracorporeal membrane oxygenation support as a bridge to pediatric heart transplantation.

BACKGROUND: Mechanical circulatory support for intractable heart failure as a bridge to transplantation has been used infrequently in children. The lack of clinically available ventricular assist devices has resulted in the use of conventional extracorporeal circuits with oxygenator as the main modality for circulatory support. In this study we reviewed our experience with extracorporeal membrane oxygenation (ECMO) support in children with irreversible heart failure who were awaiting heart transplantation. METHODS AND RESULTS: Since 1985, 14 children were placed on ECMO support for circulatory failure and were considered candidates for heart transplantation: 8 children had postcardiotomy contractile failure, 3 had dilated cardiomyopathy, and 3 had viral myocarditis. Five of these children had cardiac arrest and were placed on support during cardiopulmonary resuscitation. Mean duration of ECMO support was 109 +/- 20 hours. Eight patients developed pulmonary edema requiring decompression of the left ventricle, 3 by blade atrial septostomy and 5 by left atrial vent cannula. Nine of 14 received a heart transplant, 1 child recovered spontaneously (myocarditis), and 4 died of sepsis on ECMO. Of the children who received transplants, 6 were early survivors with 1 late death (lymphoproliferative disease), for a total of 7 of 14 (50%) early and 6 of 14 (43%) late survivors. CONCLUSIONS: Our experience suggests that ECMO is an effective means of circulatory support as a bridge to transplantation in children. Decompression of the left ventricle is often required to prevent pulmonary edema. Sepsis and bleeding remain a limitation to prolonged mechanical support with ECMO in children.

Adolescent↗
PubMed1993

Extracorporeal membrane oxygenation for cardiac rescue in children with severe myocardial dysfunction.

OBJECTIVE: To assess the experience and efficacy of extracorporeal membrane oxygenation (ECMO) for cardiac rescue in patients with presumptively lethal cardiac dysfunction at the Children's Hospital of Pittsburgh. DESIGN: Retrospective analysis of patient records from a 9-yr period. SETTING: A 22-bed tertiary care pediatric intensive care unit (ICU) with an average of 1,400 admissions per year. An average of 150 open cardiotomy surgeries are performed per year, and all postoperative and severely ill cardiac patients are cared for in the ICU. PATIENTS: A total of 29 pediatric ICU patients with myocardial failure received ECMO throughout the 9-yr study period. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Demographic information, underlying cardiac defect, intraoperative and postoperative data, postoperative course, details of ECMO treatment, and outcome were collected. Comparison of survivors with nonsurvivors was performed using the Mann-Whitney U test for continuous variables. Twenty-three (79%) of 29 patients recovered myocardial function while undergoing ECMO, 18 (62%) of 29 patients were successfully decannulated, and 13 (45%) of 29 patients survived to hospital discharge. Long-term survival rate was 11 (38%) of 29 patients. Three (60%) of five bridge-to-heart transplant patients survived. Eleven (65%) of 17 patients who suffered cardiac arrest before ECMO, survived to discharge and nine (53%) of these 17 patients remain long-term survivors. Survival rate in patients who required cardiac massage for > 15 mins before cannulation was six (55%) of 11 patients. CONCLUSIONS: Patients with severe myocardial dysfunction who fail conventional therapy can be successfully supported with ECMO during the period of myocardial recovery. ECMO can also provide a viable circulatory support system in patients with prolonged cardiac arrest who fail conventional resuscitation techniques. ECMO is also an effective means of support as a mechanical bridge to heart transplantation.

Cardiac Output, Low↗
PubMed1993

Rigid bronchoscopy balloon catheter dilation for bronchial stenosis in infants.

Stenosis of the tracheobronchial tree can be a life-threatening problem. Management options for symptomatic stenosis include serial dilation, cryotherapy, laser resection, and open surgical correction. Recently, balloon angioplasty catheters have been used to dilate stenotic airway segments. The experience in infants is limited and has for the most part utilized guide wires and fluoroscopy for balloon placement. We present two infants with symptomatic bronchial stenosis who underwent endoscopic angioplasty balloon catheter dilation. Operative technique involved catheter placement under direct vision with a rigid bronchoscope. Catheters (6F) with 8-mm-diameter balloons were used. Balloon expansion was controlled with a hand-held manometer. Both infants demonstrated significant lumen size improvement intraoperatively and marked clinical improvement postoperatively, substantiated by endoscopy and radiographs. One infant has required one repeat dilation and has subsequently been asymptomatic. The other infant has had no further respiratory problems. Our technique, using a rigid bronchoscope with direct visualization of catheter placement, obviates the need for guide wires and C-arm fluoroscopy as previously described. Endoscopic placement enables direct visualization of balloon position, and fine adjustments are possible if further dilation is necessary. Rigid bronchoscopic balloon catheter dilation can be a successful technique for bronchial stenosis and should be considered prior to attempting more invasive surgical correction.

Bronchial Diseases↗
PubMed1993

Cardiopulmonary bypass significantly reduces surfactant activity in children.

Lung injury remains an important problem after cardiopulmonary bypass. The contribution of altered surfactant concentration or activity to pulmonary dysfunction after cardiopulmonary bypass is unclear. Recent evidence indicates that alveolar surfactant exists in specific aggregate forms that differ with respect to density, phospholipid composition, and function. A transition from surface active, higher density, large aggregates of surfactant to lower density, small aggregates that possess reduced surface activity has been demonstrated after experimental lung injury. The purpose of the present study was to examine surfactant aggregate fractions before and after bypass in children. Twelve acyanotic patients, aged 2 to 12 years, underwent intraoperative pulmonary function testing followed by bronchoalveolar lavage before incision and approximately 1 hour after termination of cardiopulmonary bypass. Saturated phosphatidylcholine pool sizes and total protein content of the small- and large-aggregate fractions of bronchoalveolar lavage fluid were determined. One hour after termination of cardiopulmonary bypass, the ratio of saturated phosphatidylcholine in small-aggregate as compared with that in large-aggregate fractions increased (mean +/- standard error) from 0.19 +/- 0.03 to 0.37 +/- 0.07 (p < 0.02), as did the ratio of saturated phosphatidylcholine to protein in the small-aggregate fraction (from 0.04 +/- 0.01 to 0.08 +/- 0.02, p < 0.05). Reductions in forced vital capacity (-19% +/- 5%), inspiratory capacity (-15% +/- 3%), and small airway flow rates (-32% +/- 6%) were also observed after bypass. These changes were accompanied by a fivefold increase in alveolar polymorphonuclear leukocyte content. The present study suggests that cardiopulmonary bypass of moderate duration in relatively healthy children is associated with surfactant changes that are similar in type and magnitude to those observed in experimental lung injury.

Bronchoalveolar Lavage Fluid↗
PubMed1992

Extracorporeal membrane oxygenator rescue in children during cardiac arrest after cardiac surgery.

BACKGROUND: Conventional cardiopulmonary resuscitation (CPR) for cardiac arrest after open-heart surgery in children is often unsuccessful despite the ability to perform open-chest massage. The purpose of this study was to review our results with mechanical support as rescue therapy in children with sudden circulatory arrest after cardiac surgery. METHODS AND RESULTS: From 1981 through 1991, we have used mechanical support with an extracorporeal membrane oxygenator (ECMO) circuit for cardiac support in 33 children. Eleven of the 33 patients (age, 15 +/- 7 months) suffered cardiac arrest intractable to conventional open-chest massage 39 +/- 15 hours after an open-heart procedure. The mean duration of CPR was 65 +/- 9 minutes until ECMO flow was started. ECMO support was continued for 112 +/- 8 hours. One patient had ECMO discontinued due to bleeding (survived); three were discontinued from ECMO and died from neurological complications; and one died of cardiac dysfunction. Sepsis on ECMO was seen in one patient (survived). Overall early survival was seven of 11 (64%) with one patient requiring heart transplantation due to irreversible cardiac dysfunction. One child died late (1 month) after ECMO support. There were no long-term sequelae in the survivors. CONCLUSIONS: We conclude that ECMO rescue in children with postcardiotomy cardiac arrest is a feasible option in selected patients even after prolonged CPR (as long as 60 minutes).

Cardiac Surgical Procedures↗
PubMed1992

Long-term results of survivors of surgical valvotomy for severe aortic stenosis in early infancy.

Long-term morbidity and mortality were evaluated in the 21 survivors of a cohort of 51 consecutive infants with severe aortic valve stenosis who underwent surgical treatment in the first 3 months of life during the period from 1958 to 1988. The 21 early survivors have been followed up from 3 to 27 years (median 7.5 years). There have been two late deaths: one at age 13 year from bacterial endocarditis and the other at age 14 years after dislodgment of a prosthetic valve. The calculated 10-year actuarial survival for this group is 100%, with a 15-year actuarial survival of 75% (standard error 15%). Seven repeat operations have been performed in six patients: Three had persistent stenosis and a repeat valvotomy was performed in two of them, aged 2 years and 15 years. The other underwent placement of a conduit from the left ventricle to the descending aorta at 2 years of age. Replacement of the aortic valve has been performed in four patients because of severe valvular insufficiency 13 to 27 years after the initial operation. One of these had required a repeat valvotomy at the age of 15 years. The calculated actuarial freedom from reoperation at 10 years is 90% (standard error 6%) and at 15 years, 67% (standard error 15%). Aortic insufficiency was progressive throughout the period of follow-up. No patient had more than moderate aortic insufficiency 3 to 5 years after the initial valvotomy, whereas aortic insufficiency was severe in five of the eight patients followed up for 11 or more years. Progression of aortic insufficiency and the need for reoperation were not related to the age at initial valvotomy. Survivors of surgical aortic valvotomy in early infancy have a relatively good long-term prognosis and a high freedom from reoperation in the period leading to adolescence. Aortic insufficiency in these patients is progressive, and valve replacement eventually may be required.

Actuarial Analysis↗
PubMed1991

Coarctation and hypoplasia of the aortic arch: will the arch grow?

Hypoplasia of the transverse aortic arch of various degrees of severity is commonly seen in infants who have coarctation of the aorta. It is more often present when the coarctation is associated with intracardiac lesions that diminish or limit forward flow in the ascending aorta and promote right to left flow through an arterial duct. The increased frequency of surgical treatment of infants with complex coarctation, which is in part related to the ability to stabilize their condition with prostaglandin E1, has posed the question of the potential for growth and development of the originally hypoplastic aortic arch after conventional repair of aortic coarctation. Review of our experience with transverse aortic arch hypoplasia, found in 33 (32%) of 102 infants undergoing coarctation repair by subclavian flap aortoplasty or classic resection and end-to-end anastomosis, revealed excellent growth of the transverse arch after repair in all patients available for linear follow-up. The currently proposed extended arch repair should be reserved for the small group of infants with transverse aortic arch to ascending aorta diameter ratios (arch indices) of less than 0.25.

Abnormalities, Multiple↗