Comparison of the conditioned reinforcing properties of a safety signal and appetitive stimulus: effects of d-amphetamine and anxiolytics.

RATIONALE: Safety signals providing relief are hypothesised to possess conditioned reinforcing properties, supporting the acquisition of a new response (AnR) as seen with appetitive stimuli. Such responding should also be sensitive to the rate-increasing effects of d-amphetamine and to the anxiolytics 8-OH-DPAT and diazepam. OBJECTIVES: This study tests whether safety signals have conditioned reinforcing properties similar to those of stimuli-predicting reward. METHODS: Rats received Pavlovian conditioning with either appetitive stimuli (CS+) or safety signals (conditioned inhibitors, CIs) plus truly random control (TRC) stimuli. The appetitive group received a CS + paired with a sucrose pellet and the safety signal group, a stimulus paired with shock omission. Stimuli were tested using an AnR procedure and following systemic d-amphetamine, the 5HT-1A agonist 8-OH-DPAT and the benzodiazepine diazepam in a counterbalanced design. RESULTS: Effective conditioning selectively reduced contextual freezing during CI presentation in the safety signal group and increased food magazine responses (with respect to context and TRC) during CS + presentation in the appetitive group. The appetitive stimulus strongly supported AnR but the safety signal did not. Systemic d-amphetamine significantly potentiated lever pressing in the appetitive group but for the safety signal group, it either reduced it or had no effect, dependent on food deprivation state. 8-OH-DPAT and diazepam had no effect on responding in either group. CONCLUSIONS: The safety signal did not support AnR and, therefore, did not exhibit conditioned reinforcing properties. Furthermore, d-amphetamine decreased responding when the safety signal was presented as a consequence, whilst increasing responding with appetitive-conditioned reinforcement. These results are discussed in terms of implications for opponent motivational theory.

Randomized controlled trial of early compared with delayed use of inhaled nitric oxide in newborns with a moderate respiratory failure and pulmonary hypertension.

OBJECTIVE: To evaluate whether early treatment with inhaled nitric oxide (iNO) will prevent newborns with moderate respiratory failure from developing severe hypoxemic respiratory failure (oxygenation index (OI)>or=40). STUDY DESIGN: A total of 56 newborns with moderate respiratory failure (OI between 10 and 30) were randomized before 48 h after birth to early treatment with 20 p.p.m. of iNO (Early iNO group, n=28) or conventional mechanical ventilation with FiO(2) 1.0 (Control group, n=28). Infants received iNO and/or high-frequency oscillatory ventilation (HFOV) if they developed an OI>40. RESULT: 7 of 28 early iNO patients (25%) compared to 17 of 28 control patients (61%) developed an OI>40 (P<0.05). In the Early iNO group mean OI significantly decreased from 22 (baseline) to 19 at 4 h (P<0.05) and remained lower over time: 19 (12 h), 18 (24 h) and 16 at 48 h. In contrast, OI increased in the Control group and remained significantly higher than the Early iNO group during the first 48 h of study: 22 (baseline), 29, 35, 32 and 23 at 4, 12, 24 and 48 h, respectively (P<0.01). Of 17, 6 control patients who developed an OI>40 were successfully treated with iNO. Nine of the remaining eleven control patients and six of seven Early iNO patients who had an OI>40 despite use of iNO responded with the addition of HFOV. One patient of the Early iNO group and two of the Control group died. Median (range) duration of oxygen therapy was significantly shorter in the Early iNO group: 11.5 (5 to 90) days compared to 18 (6 to 142) days of the Control group (P<0.03). CONCLUSION: Early use of iNO in newborns with moderate respiratory failure improves oxygenation and decreases the probability of developing severe hypoxemic respiratory failure.

Modeling of the Norwood circulation: effects of shunt size, vascular resistances, and heart rate.

Hypoplastic left heart syndrome is the most common lethal cardiac malformation of the newborn. Its treatment, apart from heart transplantation, is the Norwood operation. The initial procedure for this staged repair consists of reconstructing a circulation where a single outlet from the heart provides systemic perfusion and an interpositioning shunt contributes blood flow to the lungs. To better understand this unique physiology, a computational model of the Norwood circulation was constructed on the basis of compartmental analysis. Influences of shunt diameter, systemic and pulmonary vascular resistance, and heart rate on the cardiovascular dynamics and oxygenation were studied. Simulations showed that 1) larger shunts diverted an increased proportion of cardiac output to the lungs, away from systemic perfusion, resulting in poorer O2 delivery, 2) systemic vascular resistance exerted more effect on hemodynamics than pulmonary vascular resistance, 3) systemic arterial oxygenation was minimally influenced by heart rate changes, 4) there was a better correlation between venous O2 saturation and O2 delivery than between arterial O2 saturation and O2 delivery, and 5) a pulmonary-to-systemic blood flow ratio of 1 resulted in optimal O2 delivery in all physiological states and shunt sizes.

[Radiofrequency fulguration for supraventricular tachycardia in pediatrics]. / Fulguración por radiofrecuencia de las taquicardias supraventriculares en pediatría.

Supraventricular tachycardias (SVT) are the most frequent cause of tachycardia in children. Its pharmacological treatment has adverse effects, is not curative, and is not always effective. During the last few years radiofrequency ablation (RF-A) has changed the treatment. The purpose of this study is to evaluate our experience in RF-A in children with SVT. Between 1990 and 1995, 92 patients (1 month to 17 years old) underwent electrophysiological study after the diagnosis of SVT. RF-A was attempted in 55 patients with accessory pathways (AP), slow-pathway of the atrioventricular node, or ectopic focus. The site of ablation was decided according to the electrical signals and the catheter position. The success of the RF-A was confirmed by the interruption of the tachycardia, the change in the sequence of activation of the intracardiac signals, the regression of the preexcitation, and the inability to reinduce tachycardia. RF-A was successful in 81% of the patients; 88% in those with a left AP, 56% in those with a right AP, and 100% in those with nodal reentry. Complications were seen in 7% of the patients: 3 with arterial obstruction, one with a minimal pneumothorax, and one with cardiac tamponade. During a follow up of 16.6 months there was no relapse nor late complications. We conclude that RF-A is a safe and effective procedure in pediatric patients with SVT.

Intermediate results after complete repair of tetralogy of Fallot in neonates.

From July 1988 through September 1993, 30 neonates with symptomatic tetralogy of Fallot underwent complete repair. Sixteen patients had tetralogy and pulmonary stenosis, 9 had pulmonary atresia, 3 had nonconfluent pulmonary arteries, and 2 had both pulmonary atresia and nonconfluent pulmonary arteries. The median age at operation was 11 days (mean +/- standard error of the mean, 12.6 +/- 2.9 days), with a mean weight of 3.1 +/- 0.1 kg (range 1.5 to 4.4 kg). Preoperatively, 14 patients were receiving an infusion of prostaglandin, 13 were mechanically ventilated, and 6 required inotropic support. Right ventricular outflow tract obstruction was managed by a limited transannular patch in 25 patients, infundibular muscle division with limited resection in 15, and insertion of a right ventricle-pulmonary artery valved aortic homograft conduit in 5 patients. Follow-up was complete at a median interval of 24 months (range 1 to 62 months). There were no hospital deaths and two late deaths, for 1-month, 1-year, and 5-year actuarial survivals of 100%, 93%, and 93%, respectively. The hazard function for death had a rapidly declining single phase that approached zero by 6 months after the operation. Both late deaths occurred in patients with tetralogy of Fallot and pulmonary atresia who had undergone aortic homograft conduit reconstruction, so that the only independent risk factor for death was the use of a valved homograft conduit (p < or = 0.005). Eight patients required reoperation, resulting in 1-month, 1-year, and 5-year freedom from reoperation rates of 100%, 93%, and 66%, respectively. Indications for reoperation were branch left pulmonary artery stenosis in 5 patients, residual right ventricular outflow tract obstruction in 2 patients, and severe pulmonary insufficiency in 1 patient. Independent risk factors for reoperation included an intraoperative pressure ratio between the right and left ventricles of 0.75 or greater (p = 0.01), Doppler residual left pulmonary artery stenosis of 15 mm Hg or more, or Doppler right ventricular outflow tract obstruction gradient of 40 mm Hg or more at hospital discharge (p = 0.002 and 0.02, respectively). This series demonstrates the safety of early hemodynamic repair of symptomatic tetralogy of Fallot in neonates. It also emphasizes the importance of relieving all sources of right ventricular outflow tract obstruction at the initial operation, particularly that located at the site of insertion of the ductus arteriosus, which may be difficult to diagnose in the neonate before ductal closure occurs. The safety and efficacy of valved aortic homograft conduits in neonates requires further investigation.

Origin of both coronary arteries from the pulmonary artery.

Origin of both coronary arteries from the pulmonary artery is generally a lethal condition from progressive ventricular failure. We report the clinical and surgical course of two infants, ages 3 and 6 months, with this anomaly. One patient had normal intracardiac anatomy with low pulmonary artery pressures (30/12 mm Hg). The second patient had a restrictive subpulmonic ventricular septal defect with a moderately elevated pulmonary artery pressure (50/13 mm Hg). Left ventricular ejection and shortening fractions were profoundly depressed in both patients. The common coronary trunk arose from the right anterior facing sinus in one patient and from the left posterior facing sinus in the other. Both patients underwent repair by direct coronary implantation to the aorta. Left ventricular function improved with shortening fractions near normal at a follow-up of 6 months for one patient and 1 year for the other. Early diagnosis and prompt repair is compatible with survival and return of normal shortening fraction.

Intraoperative mapping and radiofrequency ablation of the His bundle in a patient with complex congenital heart disease and intractable atrial arrhythmias following the Fontan operation.

Intraoperative mapping and radiofrequency ablation of the His bundle (with epicardial ventricular pacing) were performed in an 18-year-old woman with complex congenital heart disease and intractable chronic atrial arrhythmias following the Fontan operation. The presence of complex intracardiac anatomy as well as the exclusion of the atrioventricular conduction tissue from the systemic venous circulation strongly influenced the technical approach.

[Nonimmune fetal hydrops secondary to fetal tachycardia: their intrauterine diagnosis and treatment]. / Hidrops fetal no immune secundario a taquicardia fetal: diagnóstico y tratamiento intrauterino.

A case of nonimmune hydrops fetalis (NIHF) secondary to fetal supraventricular tachycardia (SVT) diagnosed at 33 weeks gestation is presented. Administration of digoxin to the mother yielded normal fetal heart rhythm and frequency as well as progressive resolution of hydrops after 24 hours of initiation of therapy. Causes of NIHF and diagnostic approach are mentioned. Diagnosis and management of fetal arrhythmias are discussed. The successful perinatal outcome obtained in this case and the literature review, recommend the use of antiarrhythmic drugs therapy in cases of NIHF secondary to SVT.

[Cardiac involvement in Kawasaki disease]. / Compromiso cardíaco en la enfermedad de Kawasaki.

Cardiovascular complications (CVC) of Kawasaki disease (KD) are described in 15 affected children (10 boys, mean age 18.5 months). Clinical records, electrocardiographic tracings (ECG) and bidimensional echocardiograms (BDE) were analysed. In each case the first BDE was done at clinical diagnosis (mean time 10 days from initial symptoms of disease), then at weekly intervals for the first month and each two weeks along the second month. In children showing persistent coronary artery lesions (CAL) BDE was repeated monthly and in patients without CVC at three month intervals. During follow up, no definite clinical evidence of miocardial ischemia was found, but abnormal BDE recordings were obtained from 12/15 patient: CAL in 9/15; right ventricular, left ventricular and aortic enlargement in 3/15. CAL were located at the left coronary artery (LCA) in 3/9 (one LCA aneurysm) and at both coronary arteries in 6/9 (including 3 cases with bilateral aneurysms). All patients were given aspirin and seven were also treated with intravenous gammaglobulin, this last at day 9 (mean) of disease, but 5 of them developed CVC, including 3 cases of CAL.