The incidence of arrhythmias in a pediatric cardiac intensive care unit.

A pediatric cardiac intensive care unit (CICU) manages critically ill children and adults with congenital or acquired heart disease. These patients are at increased risk for arrhythmias. The purpose of this study was to prospectively evaluate the incidence of arrhythmias in a pediatric CICU patient population. All patients admitted to the CICU at the Cardiac Center at The Children's Hospital of Philadelphia between December 1, 1997, and November 30, 1998, were evaluated prospectively from CICU admission to hospital discharge via full disclosure telemetry reviewed every 24 hours. Arrhythmias reviewed included nonsustained and sustained ventricular tachycardia (VT), nonsustained and sustained supraventricular tachycardia (SVT), atrial flutter and fibrillation, junctional ectopic tachycardia, and complete heart block. We reviewed 789 admissions consisting of 629 patients (age range, 1 day-45.5 years; median, 8.1 months). Hospital stay ranged from 1 to 155 days (total of 8116 patient days). Surgical interventions (n = 602) included 482 utilizing cardiopulmonary bypass. During the study period, there were 44 deaths [44/629 patients (7.0%)], none of which were directly attributable to a primary arrhythmia. The operative mortality was 5.1%. Overall, 29.0% of admissions had one or more arrhythmias the most common arrhythmia was nonsustained VT (18.0% of admissions), followed by nonsustained SVT (12.9% of admissions). Patients admitted to a pediatric CICU have a high incidence of arrhythmias, most likely associated with their underlying pathophysiology and to the breadth of medical and surgical interventions conducted.

Impact of inspired gas mixtures on preoperative infants with hypoplastic left heart syndrome during controlled ventilation.

BACKGROUND: Management strategies for preoperative infants with hypoplastic left heart syndrome (HLHS) include increased inspired nitrogen (hypoxia) and increased inspired carbon dioxide (hypercarbia). There are no studies directly comparing these 2 therapies in humans. This study compares the impact of hypoxia versus hypercarbia on oxygen delivery, under conditions of fixed minute ventilation. METHODS AND RESULTS: Ten anesthetized and paralyzed preoperative infants with HLHS were evaluated in a prospective, randomized, crossover trial comparing hypoxia (17% FIO(2)) with hypercarbia (2.7% FICO(2)). Each patient was treated in a random order (10 minutes per condition) with a recovery period (15 to 20 minutes) in room air. Arterial (SaO(2)) and superior vena caval (SvO(2)) co-oximetry and cerebral oxygen saturation (ScO(2)) measurements were made at the end of each condition and recovery period. ScO(2) was measured by near infrared spectroscopy. Hypoxia significantly decreased both SaO(2) (-5.2+/-1.1%, P=0.0014) and SvO(2) (-5.6+/-1.7%, P=0.009) compared with baseline, but arteriovenous oxygen saturation (AVO(2)) difference (SaO(2)-SvO(2)) and ScO(2) remained unchanged. Hypercarbia decreased SaO(2) (-2.6+/-0.6%, P=0.002) compared with baseline but increased both ScO(2) (9.6+/-1.8%, P=0.0001) and SvO(2) (6+/-2.2%, P=0.022) and narrowed the AVO(2) difference (-8.5+/-2.3%, P=0.005). Both hypoxia and hypercarbia decreased the balance between pulmonary and systemic blood flow (Qp:Qs) compared with baseline. CONCLUSIONS: In preoperative infants with HLHS, under conditions of anesthesia and paralysis, although Qp:Qs falls in both conditions, oxygen delivery is unchanged during hypoxia and increased during hypercarbia. These data cannot differentiate cerebral from systemic oxygen delivery.

Respiratory distress after intratracheal bleomycin: selective deficiency of surfactant proteins B and C.

Intratracheal bleomycin in rats is associated with respiratory distress of uncertain etiology. We investigated the expression of surfactant components in this model of lung injury. Maximum respiratory distress, determined by respiratory rate, occurred at 7 days, and surfactant dysfunction was confirmed by increased surface tension of the large-aggregate fraction of bronchoalveolar lavage (BAL). In injured animals, phospholipid content and composition were similar to those of controls, mature surfactant protein (SP) B was decreased 90%, and SP-A and SP-D contents were increased. In lung tissue, SP-B and SP-C mRNAs were decreased by 2 days and maximally at 4--7 days and recovered between 14 and 21 days after injury. Immunostaining of SP-B and proSP-C was decreased in type II epithelial cells but strong in macrophages. By electron microscopy, injured lungs had type II cells lacking lamellar bodies and macrophages with phagocytosed lamellar bodies. Surface activity of BAL phospholipids of injured animals was restored by addition of exogenous SP-B. We conclude that respiratory distress after bleomycin in rats results from surfactant dysfunction in part secondary to selective downregulation of SP-B and SP-C.

Weaning children from mechanical ventilation: a prospective randomized trial of protocol-directed versus physician-directed weaning.

OBJECTIVE: Compare outcomes between physician-directed and protocol-directed weaning from mechanical ventilation in pediatric patients. DESIGN: Prospective-randomized. SETTING: Pediatric and cardiac intensive care units in a 307-bed tertiary referral hospital for children. INTERVENTIONS: The control group (physician-directed) was weaned according to individual physician order for reduction in minute ventilation, positive end-expiratory pressure, and ordered oxygen saturation parameters for reduction in fraction of inspired oxygen (F(IO)(2)). The study group (protocol-directed) was weaned according to a predetermined algorithm developed for the purpose of this investigation. METHODS: The study enrolled 223 patients (116 physician-directed, 107 protocol-directed). All patients were monitored for hemodynamics, ventilator parameters, arterial blood gas values when available, oxygen saturation, weaning time, pre-weaning time, extubation time, and time on F(IO)(2) > or = 0.40. We also monitored the incidence of reintubation, subglottic stenosis, tracheitis, and pneumonia. The protocol-directed group had additional measurements of actual versus predicted minute volume, comparisons of respiratory rate (actual versus predicted for age), and presence of spontaneous breathing effort for 10 consecutive minutes. Data analysis was done according to intent to treat. RESULTS: There was no significant difference in 12-hour and 24-hour pediatric risk of mortality (PRISM III) scores between groups. The protocol-directed group overall had shorter total ventilation time, weaning time, pre-weaning time, time to extubation, and time on F(IO)(2) >0.40, although after stratification for respiratory diagnosis, only the difference in weaning time remained significant. There was no difference in the incidence of reintubation, new-onset tracheitis, subglottic stenosis, or pneumonia. CONCLUSIONS: Protocol-directed weaning resulted in a shorter weaning time than physician-directed weaning in these pediatric patients.

Improved early results with cavopulmonary connections.

BACKGROUND: We describe the recent results in a large cohort of patients with functionally single ventricle who underwent various modifications of cavopulmonary connections. METHODS: Using the database at our institution, we identified all children who underwent cavopulmonary connection operations between June 1995 and June 1997. Demographic data, surgical history, and perioperative course were reviewed. RESULTS: We performed 130 consecutive operations in 113 patients. The procedures included superior cavopulmonary connections in the form of the HemiFontan procedure in 45 instances, and bidirectional Glenn procedures in 11, and bilateral superior cavopulmonary connections in 7. The median age of these patients was 7.0 months. We completed Fontan operations using a fenestrated lateral tunnel on 47 occasions, and using an extracardiac conduit 9 times, 5 of which were fenestrated. A lateral tunnel without fenestration was constructed in one patient. The median age for these procedures was 19.5 months. In the remaining 10 instances, we revised Fontan procedures at a median age of 8 years. Diagnoses included hypoplastic left heart syndrome in 43 patients, double outlet right ventricle in 22, heterotaxy in 13, tricuspid atresia in 13, and a miscellaneous group accounting for the other 22. One death (0.7%) occurred within 30 days of surgery. Clinical seizures occurred in 7 children (5.3%), 6 had no residual neurologic deficits. Atrial pacing was needed in 14 children (10.7%) because of transient junctional rhythm, and 2 received treatment for supraventricular tachycardia. Pleural effusions were diagnosed radiographically after 31 of 130 (24%) procedures. Diuretic therapy resolved the effusion in 21 of these, with only 6 children requiring thoracostomy catheter drainage, and 4 undergoing thoracentesis alone. The median length of stay on the intensive care unit was 2 days, with a range from 1 to 30 days, and median stay in hospital was 6 days, with a range from 3 to 58 days. CONCLUSION: Mortality and perioperative morbidity after cavopulmonary connections have decreased dramatically in the current era. The long-term results of staged reconstruction for functionally single ventricle, nonetheless, await ongoing study.

Airway pressure release ventilation in pediatrics.

OBJECTIVES: The purpose of this study was to determine the effectiveness of airway pressure release ventilation in children. DESIGN: Prospective, randomized, crossover clinical trial. SETTING: This study was conducted in our 33-bed pediatric intensive care unit at The Children's Hospital of Philadelphia. PATIENTS: Patients requiring mechanical ventilatory support and weighing >8 kg were considered for enrollment. Patients were excluded if they required mechanical ventilatory support for >7 days or required >.50 Fio(2) for >7 days before enrollment. Patients with documented obstructive airway disease and congenital or acquired heart disease were excluded as well. INTERVENTIONS: Each patient received both volume-controlled synchronized intermittent mechanical ventilation (SIMV) and airway pressure release ventilation (APRV) via the Drager Evita ventilator (Drager, Lubeck, Germany). Measurements were obtained after the patient was stabilized on each ventilation mode. Stabilization was defined as oxygenation, ventilation, hemodynamic variables, and patient comfort within the acceptable range for each patient as determined by the bedside physician. After measurements were obtained on the initial mode of ventilation, the subjects crossed over to the alternative study mode. Stabilization was again achieved, and measurements were repeated. After completion of the second study measurements, patients were placed on the ventilation modality preferred by the bedside clinician and were followed through weaning and extubation. Measurements: Vital signs, airway pressures, minute ventilation, Spo(2), and E(T)CO(2) were recorded at enrollment and at each study condition. MAIN RESULTS: APRV provided similar ventilation, oxygenation, mean airway pressure, hemodynamics, and patient comfort as SIMV. Inspiratory airway pressures were lower with APRV when compared with SIMV. CONCLUSIONS: Using APRV in children with mild to moderate lung disease resulted in comparable levels of ventilation and oxygenation at significantly lower inspiratory peak and plateau pressures. Based on these findings, we plan to evaluate APRV in children with significant lung disease.

Prolonged extracorporeal membrane oxygenation as a bridge to cardiac transplantation.

Cardiac transplantation provides the best option for neonates with congenital heart disease that is not amenable to surgical repair or palliation. The scarcity of suitable organs for this group has resulted in prolonged waiting times; many infants die awaiting transplantation. We present the case of a newborn with severe Ebstein's anomaly and low cardiac output who was supported with extracorporeal membrane oxygenation for 1,126 hours, until an appropriate organ became available.

Early survival of infants weighing 2.5 kilograms or less undergoing first-stage reconstruction for hypoplastic left heart syndrome.

BACKGROUND: Results of staged palliation for hypoplastic left heart syndrome (HLHS) have improved in recent years; however, certain risk factors have been associated with decreased survival rates. METHODS AND RESULTS: We retrospectively reviewed the medical records of 67 patients weighing

Early results of the Ross procedure in simple and complex left heart disease.

BACKGROUND: The Ross procedure has been used increasingly to treat aortic valve disease in children and young adults. Benefits include the lack of anticoagulation after surgery and the potential growth and durability of the autograft. The purpose of this study was to review our institutional experience with the Ross procedure and to compare early outcome in simple aortic valve disease and complex left heart disease. METHODS AND RESULTS: Between January 1995 and October 1998, 66 patients (median age, 10.8 years; range, 6 days to 34.8 years) underwent the Ross procedure. The primary indication for surgery was isolated valvular disease in 41 patients: aortic stenosis (AS; n=3), aortic insufficiency (AI; n=11), and AS/AI (n=27). The remaining 25 patients had multiple levels of left ventricular outflow tract obstruction, 12 of whom had at least moderate AI. Additional left heart disease in the complex group included subaortic stenosis (n=20), arch obstruction (n=7), mitral valve disease (n=5), apical aortic conduit stenosis or insufficiency (n=3), and supravalvar AS (n=2). There were 123 prior interventions performed in 51 patients, including aortic valvotomy/valvuloplasty (n=56), coarctation repair (n=21), subaortic stenosis resection/Konno procedure (n=10), ventricular septal defect closure (n=8), apical aortic conduit placement (n=3), aortic valve replacement (n=3), and other (n=22). An isolated Ross procedure was performed in 41 patients, 10 of whom required concurrent aortic annulus enlargement procedure to accommodate the larger pulmonary autograft. In the remaining 25 patients, 49 concurrent procedures were performed, including the Konno procedure (n=17), aortic annulus enlargement (n=2), subaortic membrane resection (n=9), arch augmentation (n=5), mitral valvuloplasty (n=5), ventricular septal defect closure (n=4), apicoaortic conduit division (n=3), and other (n=4). One patient (1.5%) died 3 days after a Ross-Konno procedure, which included arch reconstruction, from presumed arrhythmia. There were no other early deaths. One patient required ECMO (extracorporeal membrane oxygenation) for 3 days after a ventricular tachycardia (VT)-related cardiac arrest. Transient complete heart block was seen in 4 patients; the duration was <5 days. No patient had left ventricular outflow tract obstruction on discharge echocardiography. Neo-AI was graded as none (n=5), trivial-mild (n=57), or moderate (n=3). All 3 patients with moderate neo-AI at discharge had abnormal pulmonary valves before surgery. Perioperative VT was noted in 18 patients (27.2%), 2 of whom were discharged on antiarrhythmic medication. CONCLUSIONS: The Ross procedure can be performed in isolation or in combination with other complex procedures with low mortality (1.5%) and acceptable short-term results, even in patients with complex left heart disease and multiple prior interventions. Postoperative VT is common. Anatomic abnormalities of the pulmonary valve preclude its use as an autograft.

Outcome after repair of tetralogy of Fallot with absent pulmonary valve.

BACKGROUND: Tetralogy of Fallot with absent pulmonary valve (TOF/APV) is associated with pulmonary artery dilatation and airway compression. METHODS: Since January 1, 1984, 28 patients with TOF/ APV have undergone complete repair (median age 11 days, range 1 day to 16 years). RESULTS: Thirteen patients were ventilated for respiratory failure preoperatively and extracorporeal membrane oxygenation was used in 3. Twenty-six patients underwent pulmonary artery plication (11 anterior, 15 anterior/ posterior). The right ventricular outflow tract (RVOT) was reconstructed with a patch (19), valved conduit (5), or monocusp valve (4). Early mortality was 21.4% (6/28), with 1 late death. All early deaths occurred in infants intubated preoperatively. Survival was 77% (95% confidence limit [CL] 56%, 89%) at 1 year and 72% (95% CL 50%, 86%) at 10 years. After surgery, 3 patients underwent reoperation for persistent respiratory symptoms, which resolved after repeat plication and placement of a valved conduit. Freedom from death or reoperation was 68% (95% CL 46%, 83%) at 1 year and 52% (95% CL 29%, 71%) at 10 years. In a multivariable analysis, only preoperative intubation was associated with a worse outcome (p = 0.04). CONCLUSIONS: Long-term outcome for patients with TOF/APV who survive the initial repair is good. Repeat plication and pulmonary valve implantation may improve outcome in patients with persistent airway compression.

Inspired oxygen concentration alters the phospholipids and protein content in the bronchoalveolar lavage-accessible space.

OBJECTIVE: To examine the effect of FIO2 on the contents of total protein, total phospholipids, phosphatidylcholine, and phosphatidylglycerol in the bronchoalveolar lavage-accessible space in male and female rats in vivo. DESIGN: Prospective, controlled trial. SETTING: Research laboratory. SUBJECTS: Adult male and female Sprague-Dawley rats. INTERVENTIONS: After animals were anesthetized with an intraperitoneal injection of pentobarbitol (50 mg/kg), a 24-gauge catheter was placed in the femoral artery. Determinations of arterial pH and PaO2 and PaCO2 were performed before tracheostomy, and all animals were then ventilated for 3 mins with an FIO2 of 0.21, followed by a reduction bronchoalveolar lavage. The animals were randomly divided equally by gender and given either an FIO2 of 0.21, 0.50, or 1.00. All subjects were ventilated in the same manner. Sampling bronchoalveolar lavage was performed 80 and 160 mins after institution of the variable FIO2. Bronchoalveolar lavage samples were analyzed for protein and phospholipid content. Arterial blood was obtained for determination of arterial pH and the PaO2 and PaCO2 immediately and 40 mins after each sampling bronchoalveolar lavage. MEASUREMENTS AND MAIN RESULTS: At the times of bronchoalveolar sampling lavage, the PaCO2 increased and the PaO2 decreased, as did the pH. In the 40-min samples obtained between sampling lavages, the arterial pH and PaCO2 and PaO2 returned to pretracheostomy values (animals ventilated with an FIO2 of 0.21) and/or higher pO2 values (animals ventilated with an FIO2 of 0.5 or 1.0). No differences were found between genders in amounts of total protein and phospholipid content in reduction and zero time bronchoalveolar lavage fluid. Males and females ventilated with an FIO2 of 0.21 differed in the amounts of total protein, total phospholipids, phosphatidylcholine, and phosphatidylglycerol found in sampling bronchoalveolar lavage at 80 and 160 mins. Amounts of total protein and total phospholipids also demonstrated gender differences with the administration of an FIO2 of 1.0, but no differences with the administration of and FIO2 of 0.5. In terms of the phospholipids, males had greater amounts in the sampling bronchoalveolar lavage at 80 mins, and females at 160 mins. Administration of an FIO2 of 0.5 or 1.0 resulted in decreased amounts of total phospholipids in both males and females when compared with and FIO2 of 0.21. In males, administration of both FIO2 of 0.5 and 1.0 resulted in decreased amounts of phosphtidylcholine found in the bronchoalveolar lavage-accessible space; in females, amounts of phosphatidylcholine were only decreased when and FIO2 of 1.0 was administered. In males, administration of and FIO2 of 1.0 also resulted in decreased amounts of phosphatidylglycerol. The decreased amount of phosphatidylglycerol occurred in females given an FIO2 of 0.5. Amounts of total protein in males and females given an FIO2 of 0.5 and in females given an FIO2 of 1.0 were found to be increased. CONCLUSIONS: Our findings support the hypothesis that hyperoxia alters surfactant composition. Further investigation is warranted to determine the mechanisms affecting secretion of phosphatidylcholine and phosphatidylglycerol into the bronchoalveolar space and to explore the gender difference in secretion.

Tumor necrosis factor-alpha alters phospholipid content in the bronchoalveolar lavage-accessible space of isolated perfused rat lungs.

OBJECTIVES: To examine the effect of tumor necrosis factor-alpha (TNF-alpha) on pulmonary artery pressure and on total protein, phospholipid, lysophosphatidylcholine, phosphatidylcholine, phosphatidylinositol, and phosphatidylglycerol content in the bronchoalveolar lavage-accessible space of the isolated perfused rat lung, and to evaluate the role of the lung in the clearance of TNF-alpha from the perfusion medium in this model. DESIGN: Prospective, controlled trial. SETTING: Research laboratory. SUBJECTS: Adult male Sprague-Dawley rats. INTERVENTIONS: The lungs from all subjects were isolated, perfused, and ventilated in the same manner. After a baseline sampling bronchoalveolar lavage, a reduction bronchoalveolar lavage was performed to establish a uniform amount of phospholipid in all lungs. This procedure was followed by the zero time sampling bronchoalveolar lavage, which verified the efficacy of the reduction lavage. After 5 mins, isoproterenol was added to the perfusion medium to promote surfactant secretion. Five minutes later, TNF-alpha (experimental group) and/or its carrier solution (control group) was added to the perfusion medium. Sampling bronchoalveolar lavages were repeated at 1 and 2 hrs after the zero time. Bronchoalveolar lavage samples were subsequently analyzed for protein and phospholipid content. After each sampling bronchoalveolar lavage, perfusion medium was obtained for immediate determinations of pH and the partial pressures of oxygen and carbon dioxide and the subsequent determination of TNF-alpha content. Pulmonary arterial pressures were continuously measured. MEASUREMENTS AND MAIN RESULTS: The pH and PCO2 in the perfusion medium remained in the physiologic range for all lungs, while the PO2 remained consistently increased. Mean pulmonary arterial pressures did not differ between groups. TNF-alpha levels were constant throughout the 2-hr period in the experimental group, and no TNF-alpha was detected in the perfusion medium of the control group. Amounts of total protein, total phospholipid, and lysophosphatidylcholine did not differ between the two groups. Although not statistically significant, phosphatidylglycerol was lower in the experimental group (p < .07). An increase in phosphatidylinositol content in the experimental group with a concomitant decrease in the control group between 60 and 120 mins was noted (p < .01). Amounts of phosphatidylcholine were found to be lower in the experimental group throughout the 2-hr period (p < .02). CONCLUSIONS: a) TNF-alpha alters the amounts of phosphatidylcholine, phosphatidylinositol, and possibly phosphatidylglycerol present in the lavage-accessible space of the isolated perfused rat lung. Possible mechanisms might include a direct effect of TNF-alpha on phospholipid secretion and/or reuptake, or an indirect effect via alteration of the type II pneumocytes' response to beta-adrenergic receptor stimulation. b) Increases in pulmonary arterial pressures seen in vivo with TNF-alpha administration are not due to a direct effect. Alterations in cardiac function or the interaction of other agents may be necessary to develop changes in pulmonary arterial pressure. c) This in vitro model does not demonstrate the rapid clearance of TNF-alpha from the circulation that is seen in vivo, suggesting that TNF-alpha metabolism does not occur primarily in the lung. Our findings support the hypothesis that TNF-alpha may alter surfactant composition, which may in turn contribute to the development of the adult respiratory distress syndrome.

Large-airway collapse due to acquired tracheobronchomalacia in infancy.

Seven infants with wheezing and cyanotic spells were diagnosed as having tracheobronchomalacia by bronchoscopy or fluoroscopy. These studies demonstrated narrowing of the central airways by 75% or more on exhalation. Five patients were premature infants who had been ventilated for hyaline membrane disease. The mean time from onset of symptoms to diagnosis was six months. Determination of the optimal positive end-expiratory pressure (PEEP) during fluoroscopy facilitated subsequent management. Six of the seven patients required PEEP of 8 to 18 cm H2O for at least three months, and five of the seven still require mechanical ventilation. All patients improved, with decreased cyanotic spells and a reduced requirement for ventilatory support. Tracheostomy without PEEP did not appear to be helpful. Tracheobronchomalacia may be more frequent than usually appreciated; the treatment of choice appears to be long-term PEEP.

Aspiration during induction of anaesthesia in patients with colon interposition.

The risk of aspiration during induction of anaesthesia in patients with oesophageal disease is not well defined, and controversy exists with respect to patients who have undergone pharyngeal-gastric colon interposition. Excellent gastrooesophageal competence has been documented in many of these patients, and propulsive peristalsis has been demonstrated in interposed colonic segments, suggesting that aspiration risk is low. This report, however, describes recent anaesthetic experiences in two patients with colon interpositions and shows that these patients may have markedly redundant interposed segments that retain food or other particulate residue and, thus, present a significant risk of particulate aspiration. Awake intubation may be the best approach to avoid aspiration in these patients.