Jeffrey R. Darst

The Hemodynamic Response to Dexmedetomidine Loading Dose in Children With and Without Pulmonary Hypertension

BACKGROUND:Dexmedetomidine, an &agr;-2 receptor agonist, is widely used in children with cardiac disease. Significant hemodynamic responses, including systemic and pulmonary vasoconstriction, have been reported after dexmedetomidine administration. Our primary goal of this prospective, observational study was to quantify the effects of dexmedetomidine initial loading doses on mean pulmonary artery pressure (PAP) in children with and without pulmonary hypertension. METHODS:Subjects were children undergoing cardiac catheterization for either routine surveillance after cardiac transplantation (n = 21) or pulmonary hypertension studies (n = 21). After anesthetic induction with sevoflurane and tracheal intubation, sevoflurane was discontinued and anesthesia was maintained with midazolam 0.1 mg/kg IV (or 0.5 mg/kg orally preoperatively) and remifentanil IV infusion 0.5 to 0.8 &mgr;g/kg/min. Ventilation was mechanically controlled to maintain PCO2 35 to 40 mm Hg. When end-tidal sevoflurane was 0% and fraction of inspired oxygen (FIO2) was 0.21, baseline heart rate, mean arterial blood pressure, PAP, right atrial pressure, pulmonary artery occlusion pressure, right ventricular end-diastolic pressure, cardiac output, and arterial blood gases were measured, and indexed systemic vascular resistance, indexed pulmonary vascular resistance, and cardiac index were calculated. Each subject then received a 10-minute infusion of dexmedetomidine of 1 &mgr;g/kg, 0.75 &mgr;g/kg, or 0.5 &mgr;g/kg. Measurements and calculations were repeated at the conclusion of the infusion. RESULTS:Most hemodynamic responses were similar in children with and without pulmonary hypertension. Heart rate decreased significantly, and mean arterial blood pressure and indexed systemic vascular resistance increased significantly. Cardiac index did not change. A small, statistically significant increase in PAP was observed in transplant patients but not in subjects with pulmonary hypertension. Changes in indexed pulmonary vascular resistance were not significant. CONCLUSION:Dexmedetomidine initial loading doses were associated with significant systemic vasoconstriction and hypertension, but a similar response was not observed in the pulmonary vasculature, even in children with pulmonary hypertension. Dexmedetomidine does not appear to be contraindicated in children with pulmonary hypertension.

Predicting recovery: Successful explant of a ventricular assist device in a child with dilated cardiomyopathy

A previously healthy, 13-year-old girl presented with new-onset dilated cardiomyopathy, and is placed on a left ventricular assist device (VAD). Herein we describe a unique VAD weaning protocol used to determine the timing and feasibility of a VAD explant.

Patent Ductus Arteriosus

The ductus arteriosus is a normal and vital fetal structure that arises from the left sixth aortic arch. It connects the main pulmonary artery to the descending thoracic aorta just distal and opposite to the origin of the left subclavian artery (Fig. 14.1). The pulmonary end usually tapers and is narrower than the aortic end.

Button battery ingestion in children: a role for angiography?

A 15-month 8.2-kg girl presented to the emergency room with an insidious history of progressive drooling and not eating following ingestion of a button battery two days previously. She was alert with bilaterally clear breath sounds and was hemodynamically stable. A chest radiograph revealed a button battery lodged in the esophagus at the level of the tracheal carina. As we had previously experienced catastrophic bleeding with batteries lodged in the esophagus below the thoracic inlet, she was brought to the cardiac catheterization laboratory for endoscopic button battery removal. Following induction of anesthesia and tracheal intubation, vascular access (femoral vein and artery) was secured. The cardiac surgery team, perfusion equipment, and a primed cardiopulmonary bypass machine were present in the room. Simple fluoroscopy (Figure, panel A) showed the confirmatory ‘‘halo sign’’ of a button battery, and angiography imaging in the anteroposterior (AP) view (Figure, panel B) and the lateral view (Figure, panel C) verified the battery to be 3-4 mm from the innominate artery and 10-mm from the aortic arch, although with no direct vessel involvement. The narrowest end of the battery, which is always the negative pole (Figure, panel C), was directed posteriorly, away from the aortic vessels. After an endoscope was advanced using fluoroscopic guidance and then direct visualization, the battery was removed with forceps. Following removal, two large ulcers at ten o’ clock and five o’clock were present with associated edema, causing 3 cm of significant, longitudinal esophageal narrowing. The mucosa, although friable, showed no active bleeding. The patient made a satisfactory recovery and remains asymptomatic, although with a mild esophageal stricture.

Pulmonary interstitial glycogenosis: Diagnostic evaluation and clinical course

We sought to describe the phenotype for patients with P.I.G. including presentation, evaluation, cardiac co‐morbidities, high resolution computed tomography findings, and outcomes.

An Unusual Etiology of Infantile Hemoptysis

Figure 1. (A) Chest radiograph showing mild rightward mediastinal shift with mildly decreased right lung volumes. Bilateral peribronchial thickening and patchy airspace opacities, and a suggestion of a retrocardiac scimitar vein (arrow), are also seen. (B) Coronal mutiplanar reconstruction from computerized tomography scan with angiogram performed via a lower extremity injection, showing contrast within the lumen of the superior scimitar vein with filling defect inferiorly (arrow). The lack of reflux of contrast into the inferior scimitar vein despite pressure injection into the inferior vena cava also implied obstruction at the scimitar vein/inferior vena cava junction. The enhancement pattern in the superior scimitar vein (with less-dense contrast than in the left pulmonary veins) is thought to be due to the presence of downstream venous obstruction. Also seen is a hypoplastic right pulmonary artery