Biomedical subjects

Gregor Wollenek

Publications and source records attributed to Gregor Wollenek.

6 recordsLinked to original sources

PubMed2005

Vascular dysfunction after coarctation repair is related to the age at surgery.

BACKGROUND: Despite repair of aortic coarctation, hypertension is frequent in adults and premature coronary and cerebrovascular disease remain of concern. Persistent impairment of arterial dilation has been suspected to contribute to abnormal blood pressure regulation. We tested the hypothesis that arterial reactivity is more likely to be impaired in patients corrected at older age. METHODS: We studied changes in brachial artery diameter in response to reactive hyperemia (FMD) and to nitroglycerin (NMD) in 36 patients and 25 controls. Depending on their age at surgery, patients were divided in group A (surgery <9 years) and group B (surgery > or =9 years). RESULTS: Cholesterol levels and percentage of smokers were similar in patients and controls, but 16 patients had arterial hypertension compared to none of the controls. Endothelium-dependent vasodilation, FMD, and endothelium-independent vasodilation, NMD, were significantly impaired in patients vs. controls (8.2+/-6.2% vs. 13.0+/-5.1%, p<0.001 and 12.9+/-8.0% vs. 18.8+/-9.2%, p<0.01, respectively), both, in hypertensives (8.3+/-6.0%, p<0.01 and 11.8+/-6.0%, p<0.05) and in normotensives (8.1+/-6.5% p<0.01 and 13.8+/-9.3%, p<0.05). However, FMD and NMD in patients of group A did not significantly differ from that in controls (10.0+/-6.7% n.s. and 15.0+/-7.6% n.s.), whereas they were lowest in patients of group B (5.5+/-4.3%, p<0.0001 and 9.6+/-7.7% p<0.001). CONCLUSIONS: Persistent impairment of FMD and NMD after repair of coarctation is more likely to be present in patients corrected at older age. It may be an important contributor to abnormal blood pressure regulation and late morbidity and mortality.

Adolescent↗

PubMed2004

The oxygen dissociation curve: quantifying the shift.

An oxyhaemoglobin dissociation curve (ODC) quantifies the most important function of red blood cells and that is the affinity for oxygen and its delivery to the tissues. Oxygen affinity for haemoglobin plays a critical role in the delivery of oxygen to the tissues and is changed by shifting to the left or right. A shift to the left implies an increased oxygen affinity and, hence, tighter binding due to the higher oxygen saturation in relation to the pO2. On the other hand, a shift to the right corresponds to a decreased oxygen affinity and easier release of oxygen to the tissues. It is well known that the ODC shifts in response to changes in pH, pCO2 and 2,3 diphosphoglycerate. However, how much the ODC shifts has never been quantified. Arterial and venous blood gases were taken during cardiopulmonary bypass and two indices were used to quantify the shift of the ODC; the p50 shift and the SO2 difference. Arterial blood shifted to the right by 4 +/- 0.1 mmHg at a pH of 7.24 and shifted to the left by -3.5 +/- 0.05 mmHg at a pH of 7.51. The change in arterial saturation was minimal, rising by 0.8% and dropping by -5% and did not correlate to p50 shifting and changes in pH, but demonstrated changes dependent on the concentration of dyshaemoglobins. The venous blood exhibited a greater range of p50 shifting at each pH value. At a pH of 7.24, the p50 shifted to the right by 4.8 +/- 2 mmHg and at a pH of 7.51 the p50 shifted to the left by -4 +/- 1.8 mmHg. Unlike the arterial blood, the change in saturation correlated well to p50 shifting. It is shown here for the first time how much the curve shifts with changes in pH and how this may be used to evaluate treatment strategies.

Arteries↗

PubMed2003

Methemoglobin formation in children with congenital heart disease treated with inhaled nitric oxide after cardiac surgery.

OBJECTIVE: Inhaled nitric oxide (NO) is used as a therapy of pulmonary hypertension in children after cardiac surgery. Hemoglobin binds to NO with great affinity and forms methemoglobin by oxidation in the erythrocyte. Once produced, methemoglobin is unable to transport and unload oxygen in the tissues. The amount of available hemoglobin in the body for oxygen transport is thereby reduced. Anemia, acidosis, respiratory compromise and cardiac disease may render patients more susceptible than expected for a given methemoglobin level. The goal of the present study was to review the cumulative effect of inhaled NO on methemoglobin formation in critically ill children. We therefore looked for methemoglobin levels in children with congenital heart disease after cardiac surgery who were treated with inhaled NO in a range of 5-40 ppm. METHODS: We retrospectively reviewed the medical charts of 38 children with congenital heart disease after cardiac surgery. We extracted demographic data and physiological measurements at the following time points: (1) T0 = before starting inhaled NO therapy, (2) T1 = 24 h after the beginning of inhaled NO therapy, (3) T2 = half-time therapy, (4) T3 = end of therapy, (5) T4 = 24 h after finishing inhaled NO therapy. RESULTS: The median duration of inhaled NO therapy was 5.5 days (interquartile range 6, range 2-29), NO concentrations at T1 and T2 were 16 ppm (10, 5-40) and 12.5 ppm (12.3, 2-40), respectively. The median cumulative dose of inhaled NO was 1699 ppm (2313, 193-7018). Methemoglobin levels increased moderately, but significantly, during therapy ( T0 vs T1 p<0.05 and T0 vs T2 p<0.001). The highest methemoglobin level measured was 3.9%. Methemoglobin levels correlated positively with the inhaled NO doses applied at T1 ( r(2)=0.8376; p<0.01) and at T2 ( r(2)=0.8945; p<0.01). At T1 the methemoglobin level correlated negatively with the T1 blood pH value. The overall mortality rate was 13.2% (5 of 38 study patients died). There was no significant difference in methemoglobin levels between survivors and non-survivors. CONCLUSION: We conclude from our data that the use of inhaled NO therapy for children with congenital heart disease after cardiac surgery in the described range of 5-40 ppm, resulting in a maximum of 4% methemoglobin blood level, is feasible and safe. However, we recommend the use of the minimal effective dose of inhaled NO and continuous monitoring of methemoglobin levels, especially in cases of anemia or sepsis in critically ill children.

Administration, Inhalation↗

PubMed2003

Early postoperative prediction of cerebral damage after pediatric cardiac surgery.

BACKGROUND: Cerebral damage is a serious complication of pediatric cardiac surgery. Early prediction of actual risk can be useful in counseling of parents, and in early diagnosis and rehabilitation therapy. Also, if all children at risk could be identified therapeutic strategies to limit perioperative cerebral damage might be developed. The aim of this study is to create a mathematical model to predict risk of neurologic sequelae within 24 hours after surgery using simple and readily available clinical measurements. METHODS: The hospital records of 534 children after cardiac surgery were reviewed. Variables examined were age at operation, diagnosis, use of cardiopulmonary bypass, arterial and central venous oxygen saturation, serum glucose, lactate and creatine kinase, mean arterial pressure, and body temperature. The endpoint for each study patient was the occurrence or lack of occurrence of seizures, movement or developmental disorders, cerebral hemorrhage, infarction, hydrocephalus, or marked cerebral atrophy. Univariate and multivariate regression analyses were used to evaluate the predictive power of the investigated factors as well as to create a predictive model. RESULTS: In 6.26% of children symptoms of cerebral damage were found. Significant risk factors were age at surgery, more complex malformations, metabolic acidosis, and increased lactate (odds ratio: age, 0.882/yr [0.772-1.008]; complex malformations, 10.32 [1.32-80.28]; arterial pH more than 7.35 to 0.4 [0.18-0.89]; lactate -1.018 per mg/dL [1.006-1.03]). CONCLUSIONS: It is possible to quantify the risk of appearance of symptoms of cerebral damage after cardiac surgery within 24 hours using simple and readily available clinical measurements.

Analysis of Variance↗

PubMed2002

Cold water submersion and cardiac arrest in treatment of severe hypothermia with cardiopulmonary bypass.

In the paediatric population, submersion injury with drowning or near-drowning represents a significant cause of morbidity and mortality. This study reviews retrospectively our own experiences and the literature on the use of cardiopulmonary bypass (CPB) to rewarm paediatric victims of cold water submersion who suffer severe hypothermia (<28 degrees C) and cardiac arrest (asystole or ventricular fibrillation). In addition to three children treated at our institution, nine other victims were found in the literature. In this cohort of 12 children aged between 2 and 12 years, there was a tendency to better outcome with lower core temperature at the beginning of extracorporeal circulation (mean temperature in nine survivors, 20 degrees C; in three non-survivors, 25.5 degrees C). The lowest temperature survived was 16 degrees C. Neither base excess, pH nor serum potassium levels were reliable prognostic factors. The lowest base excess in a survivor was -36.5 mmol/l, the lowest pH 6.29. We consider CPB as the method of choice for resuscitation and rewarming of children with severe accidental hypothermia and cardiac arrest (asystole or ventricular fibrillation). Compared with adults, children, especially smaller ones, require special consideration with regard to intravenous cannulation as drainage can be inadequate using femoral-femoral cannulation. In hypothermic children we advocate, therefore, emergency median sternotomy. Until more information regarding prognostic factors are available, children who are severely hypothermic and clinically dead after submersion in cold water--even if for an unknown length of time--should receive cardiopulmonary resuscitation (CPR) and be transported without delay to a facility with capabilities for CPB instituted via a median sternotomy.

Body Temperature↗

PubMed2002

The University of Vienna experience in heart transplantation.

Since the University of Vienna Cardiac Transplant Program began in 1984, 892 heart transplant procedures have been performed through the end of 2001. One- and five-year survival has increased steadily over time to 80% and 75%, respectively, in the most recent cohort. Ten-year survival is 55%. Over the past 10 years our program has seen dramatic changes in patient selection, accepting now patients with more risk factors (age, diabetes, elevated pulmonary resistance,..). Developments in immunosuppression have decreased the incidence of infection, rejection and graft arteriosclerosis continuously. Our program continues to pursue novel strategies to improve the survival and quality of life of our heart transplant patients.

Adolescent↗