Efficacy of Bone Source™ and Cementek™ in comparison with Endobon™ in critical size metaphyseal defects, using a minipig model.

INTRODUCTION: To examine and compare biocompatibility, osteocompatibility, rate of resorption, and remodelling dynamics of 2 calcium phosphate cements in comparison with a well-established hydroxyapatite ceramic. MATERIALS AND METHODS: In a randomised fashion, Bone Source™, Cementek™, and Endobon™ were implanted bilaterally into the proximal metaphyseal tibiae of 35 Göttinger minipigs in a direct right vs. left intra-individual comparison. Fluorescent labelling was used. Histological and morphometric evaluations were carried out at 6, 12, and 52 weeks. RESULTS: All bone substitutes showed good biocompatibility, bioactivity, and osteoconductivity. Endobon™ was not degraded over the follow-up period. Cementek™ was degraded constantly and significantly over the time intervals, whereas Bone Source™ was degraded mainly from the 6 week to 12 week interval. After 52 weeks, a significant difference of residual material within the defect zone was detected between all substitutes, with the highest resorption rate for Cementek™. Bone Source™ was least degraded. Defects filled with Endobon™ were characterised by a significantly continuous bony ingrowth over the time intervals. Bone formation within the defects filled with Cementek™ and Bone Source™ showed significant peaks 12 weeks after implantation. After 52 weeks, a significant difference in the amount of new bone within the defect area was detected, with the highest levels for Endobon™, followed by Cementek™. CONCLUSION: After 1 year a restitution ad integrum could not be observed in any treatment group. The ceramic Endobon™ showed the expected response histologically. Based on its porosity it excelled in osteoconductivity. Concerning the calcium phosphate cements, a thorough osseous incorporation seemed to inhibit further degradation of both bone substitute materials.

The efficacy of Biobon and Ostim within metaphyseal defects using the Göttinger Minipig.

INTRODUCTION: To compare bio, osteocompatibility, rate of resorption and remodeling dynamics of two clinically used bone substitutes. MATERIALS AND METHODS: In a randomized fashion Biobon and Ostim were implanted bilaterally into the proximal metaphyseal tibiae of 18 Göttinger Minipigs in a direct right versus left "intra-individual" comparison. Fluorescent labelling was used. Microradiographic, histological and morphometric evaluation was carried out at 6, 12 and 52 weeks. RESULTS: Both bone substitutes showed good biocompatibility, bioactivity and osteoconductivity. The degradation dynamics of both materials differed. Degradation of Ostim stopped after 6 weeks postoperatively, whereas Biobon was degraded slowly but evenly over the time intervals. Only at 6 weeks a significant (P < 0.05) difference in resorption rate was detected. Both Biobon and Ostim showed incomplete resorption after a year. CONCLUSION: After 1 year no "restitutio ad integrum" could be observed in either group. Similar to ceramics, a thorough osseous incorporation seemed to inhibit further degradation of both bone substitute materials.

Methemoglobinemia: Toxicity of inhaled nitric oxide therapy.

Elevation in methemoglobin is a known toxicity of inhaled nitric oxide (NO) therapy. This article describes two significant episodes of methemoglobinemia. These cases illustrate the probable cause and the treatment strategies for the potential for delivery of high concentrations of NO, resulting in methemoglobinemia with moderate and even low-dose delivered NO. We propose mechanisms for this occurrence and means of prevention.

Extracorporeal membrane oxygenation in children after repair of congenital cardiac lesions.

BACKGROUND: The purpose of this study was to review our experience in the early application of extracorporeal membrane oxygenation (ECMO) in patients requiring mechanical assistance after cardiac surgical procedures. METHODS: The hospital records of all children requiring ECMO after cardiac operation were retrospectively reviewed, and an analysis of variables affecting survival was performed. RESULTS: Fifty pediatric patients between May 1997 and October 2000 required ECMO for cardiopulmonary support after cardiac operation. Patients ranged in age from 1 day to 11 years (median age, 40 days). Forty-eight patients underwent repair of congenital cardiac lesions and 2 were included after receiving a heart transplant. Twenty-two children could not be weaned from cardiopulmonary bypass and were placed on ECMO in the operating room for circulatory support. Of the 28 children who required ECMO in the intensive care unit, 10 had ECMO instituted after cardiopulmonary arrest (mean cardiopulmonary resuscitation time 42 minutes; range, 5 to 110 minutes). In infants with single-ventricle physiology, survival to discharge was 61% (11 of 18 patients) as compared with 43% (14 of 32 patients) in those with biventricular physiology. Thirty of the 50 patients (60%) were successfully weaned from ECMO, of which 25 (83%) were discharged home. Overall survival to discharge in the entire cohort was 50%. Extracorporeal membrane oxygenation support greater than 72 hours was a grave prognostic indicator. Overall survival in this group was 36% (9 of 25 patients) compared with 56% (14 of 25 patients) in those with ECMO support less than 72 hours (p < 0.05). Univariate analysis revealed the presence of renal failure, extended periods of circulatory support, and a prolonged period of cardiopulmonary resuscitation as risk factors for mortality. The presence of shunt-dependent flow, operative procedure, and institution of ECMO in the intensive care unit did not alter survival. CONCLUSIONS: Extracorporeal membrane oxygenation provides effective support for postoperative cardiac and pulmonary failure refractory to medical management. Early institution of ECMO may decrease the incidence of cardiac arrest and end-organ damage, thus increasing survival in these critically ill patients.

Long-lasting improvement after septal myectomy for hypertrophic obstructive cardiomyopathy.

BACKGROUND: The most effective treatment of symptomatic patients with hypertrophic obstructive cardiomyopathy is still disputed. Treatment options include medical therapy, pacemaker insertion, percutaneous transluminal septal myocardial ablation, mitral valve replacement, and surgical resection of obstructing muscle. The long-term results of the various treatment options are not well defined. We aimed to demonstrate that septal myectomy is efficacious in reducing or abolishing left ventricular outflow tract gradient and leads to long-lasting symptomatic improvement in most patients. METHODS: Twenty-two consecutive patients had septal myectomy between 1981 and the present. Their records were reviewed to document the details of their preoperative status, hospital course, their subsequent clinical outcome, and current status. RESULTS: Mean age at operation was 31.3 years. Preoperatively all patients were disabled by typical symptoms despite aggressive medical treatment. Mean resting gradient was 78 mm Hg. Nine patients required simultaneous associated cardiac procedures. There were no perioperative deaths and minimal morbidity. Two patients died at 6 and 9 years postoperatively of congestive heart failure and arrhythmias. Long-term survivors have been followed up for a mean of 6.6 years. Currently all have minimal or no symptoms. The mean resting gradient was 12 mm Hg. No patient has required reoperation for residual obstruction. CONCLUSIONS: Septal myectomy reduces or abolishes left ventricular outflow tract gradient in hypertrophic obstructive cardiomyopathy. Myectomy provides long-lasting symptomatic improvement in most patients. The clinical status of patients late postoperatively can be affected by arrhythmias and myocardial dysfunction.

Glucagon lowers canine biliary cholesterol output at physiologic doses.

Pharmacologic doses of glucagon affect canine bile secretion by increasing bile flow while simultaneously decreasing biliary cholesterol output. The present study was performed to determine if physiologic doses of glucagon reduce biliary cholesterol output. Awake dogs received both intravenous 1% sodium taurocholate (50 ml/hr) to stabilize bile flow and somatostatin (12 micrograms/kg/hr) to suppress endogenous pancreatic hormone release. Suppression was documented by significant decreases in portal plasma glucagon and insulin levels. During experimental trials, dogs received, in addition, glucagon (5 ng/kg/min) infused via a splenic vein catheter. Bile flow significantly decreased during the initial hour of somatostatin infusion but increased significantly only in experimental trials during subsequent glucagon infusion. Biliary cholesterol output showed no change during control studies (N = 9), but decreased significantly during glucagon infusion studies (N = 11). Biliary phospholipids and bile salts failed to show any changes during glucagon infusion. These data demonstrate that glucagon at physiologic levels influences both the volume and cholesterol content of bile and suggest the mechanism of decreasing cholesterol output must be independent of pathways for influencing bile salt or phospholipid secretion.