RESUMEN

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.

Asunto(s)

Dióxido de Carbono/administración & dosificación , Síndrome del Corazón Izquierdo Hipoplásico/terapia , Nitrógeno/administración & dosificación , Oxígeno/administración & dosificación , Cuidados Preoperatorios , Respiración Artificial/métodos , Administración por Inhalación , Anestesia , Arterias/fisiopatología , Monitoreo de Gas Sanguíneo Transcutáneo/instrumentación , Encéfalo/metabolismo , Estudios Cruzados , Hemodinámica/efectos de los fármacos , Humanos , Síndrome del Corazón Izquierdo Hipoplásico/fisiopatología , Hipoxia/sangre , Hipoxia/inducido químicamente , Recién Nacido , Monitoreo Fisiológico , Oxígeno/análisis , Oxígeno/metabolismo , Estudios Prospectivos , Espectroscopía Infrarroja Corta

RESUMEN

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.

Asunto(s)

Desconexión del Ventilador , Algoritmos , Niño , Preescolar , Unidades de Cuidados Coronarios , Femenino , Humanos , Unidades de Cuidado Intensivo Pediátrico , Masculino , Estudios Prospectivos , Terapia Asistida por Computador/estadística & datos numéricos , Factores de Tiempo , Resultado del Tratamiento

RESUMEN

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.