The cardiovascular effects of partial liquid ventilation in newborn lambs after experimental meconium aspiration.

OBJECTIVE: To study the effects of partial liquid ventilation with perfluorocarbon on cardiovascular function, pulmonary gas exchange, and lung mechanics in term newborn lambs with pulmonary hypertension induced by tracheal instillation of human meconium. DESIGN: Prospective, randomized study. SETTING: Research Unit at a university-affiliated hospital. SUBJECTS: Twelve term newborn lambs (<6 days old). INTERVENTIONS: Lambs were studied in two groups (n = 6): meconium aspiration (3-5 ml/kg 20% meconium solution) managed on pressure-limited conventional mechanical ventilation with or without partial liquid ventilation with perfluorocarbon. MEASUREMENTS AND MAIN RESULTS: Heart rate, systemic and pulmonary arterial pressures, arterial pH and blood gases, cardiac output, and pulmonary mechanics were measured. Partial liquid ventilation in term newborn lambs with experimental meconium aspiration did not alter cardiovascular profile: heart rate, systemic arterial pressure, and cardiac output maintained initial values throughout the experiment. There was a significant improvement in gas exchange (oxygenation increased from values of <100 torr to 338 torr, and ventilation reached normal values in 15 mins). Dynamic compliance increased in 30 mins, reaching basal values (1.1 +/- 0.3 ml/cm H(2)O per kg). Despite the good response (blood gases and cardiovascular profile) to partial liquid ventilation in meconium aspiration syndrome, pulmonary hypertension did not decrease. CONCLUSIONS: Partial liquid ventilation with perfluorocarbon could be a good noninvasive alternative technique that improves gas exchange and pulmonary mechanics in meconium aspiration syndrome without impairing cardiovascular function.

[Extracorporeal membrane oxygenation (ECMO). II. The development of an experimental model in newborn lambs]. / Oxigenación por membrana extracorpórea (ECMO). II. Desarrollo de un modelo experimental en corderos recién nacidos.

OBJECTIVE: Extracorporeal membrane oxygenation (ECMO) is a technique used for cardiorespiratory support in the treatment of newborns with severe respiratory insufficiency. ECMO has not been used yet in newborns in Spain. The aim of this work was to develop an experimental veno-arterial ECMO model in newborn lambs for training the NICU medical and nursing staff before the clinical application of this technique. MATERIAL AND METHODS: Six newborn lambs were anesthetized, traqueotomized and connected to a neonatal ventilator. The right jugular vein and left carotid artery were cannulated and the catheters were located in the right atrium and aortic arch, respectively. A venous-arterial ECMO was performed during three hours, with an experimental ECMO circuit developed by us. Arterial pH and blood gases, systemic and airway pressures, heart rate, and rectal temperature were monitored. RESULTS: The experimental ECMO circuit developed by use had a very low cost, but was capable of maintaining adequate gas exchange, acid-base balance and a normal rectal temperature. CONCLUSIONS: The development of an experimental ECMO model in newborn lambs may allow the establishment of an initial training program and to maintain the expertise of the NICU staff of a perinatal center planning to start an ECMO program.

[Continuous hemofiltration. Development of an experimental model]. / Hemofiltración continua. Desarrollo de un modelo experimental.

OBJECTIVE: Continuous hemofiltration is an extracorporeal technique used to eliminate water and solutes by convective transport through a hemofilter. The aim of this study was to develop an experimental model of arterio-venous and veno-venous continuous hemofiltration in order to gain experience before its clinical application in human neonates. MATERIALS AND METHODS: Twelve white New Zealand adult rabbits were anesthetized, tracheotomized and connected to a continuous flow neonatal ventilator. Continuous arterio-venous hemofiltration (n = 6) was performed via catheters placed in the carotid artery and jugular vein and veno-venous hemofiltration (n = 6) by a double-lumen catheter located in the inferior vena cava. Heart rate, arterial pressure, pH and blood gases, and the volume of ultra-filtrate were monitored and recorded for a three hour period. RESULTS: In both groups a high rate of ultrafiltration was achieved. The volume of ultrafiltration decreased somewhat during the second hour and remained stable thereafter. No hemodynamic changes were detected. CONCLUSIONS: The development of an experimental model for continuous arterio-venous and veno-venous hemofiltration in rabbits, facilitated the implantation of these techniques in human neonates. The model may be used to train the staff of the Neonatal Intensive Care Unit and to eliminate difficulties with vascular access and the care of extracorporeal lines.

[Pulmonary mechanism in preterm neonates without respiratory problems]. / Estudio de la mecánica pulmonar en recién nacidos pretérmino sin problemas respiratorios.

Pulmonary function was measured by computerized pneumotacography in 26 preterm-newborn infants without respiratory problems. Mean (+/- SD) for birth weight, gestation and postnatal age were 2,034 +/- 412 g, 34.1 +/- 1.7 weeks, and 2.2 +/- 1.6 days, respectively. An esophageal balloon, a differential transducer and nasal prongs were used to measure pressure and flow. The following parameters were measured in each respiration by the mean squares method: Dynamic compliance (Cdyn), total respiratory resistance (RRt) and work (WRt), respiratory time constant (KTt), rate (f) and maximal inspiratory and expiratory flows (PIF, PEF). Replication of the method was found to be good, as the differences between two determinations were not significant (p less than 0.05). The mean differences were less than 6.26%. The mean (+/- SD) and the 3rd and 97th percentiles for each parameter were the following: f: 52 +/- 7 (39-66) r.p.m., Tv: 6.6 +/- 1.1 (4.5-8.7) ml/kg, Vmin: 342 +/- 82 (128-502) ml/min, Cdin: 3.7 +/- 1.1 (1.5-6) ml/cm, RRt: 83 +/- 47 (37-204) cm/L/sec, TRt: 27 +/- 15 (2-57.1) g/cm/kg, PIF: 2.2 +/- 0.5 (1.1-3.2) L/min and PEF: 1.9 +/- 0.6 (0.7-3) L/min.

[Treatment of preterm neonates with severe respiratory distress syndrome using exogenous natural surfactants of porcine origin]. / Tratamiento con surfactante natural exógeno de origen porcino de recién nacidos pretérmino con síndrome del distrés respiratorio grave.

From September 1989 to September 1990, a total of 25 newborn infants with severe RDS (on mechanical ventilation and with a FiO2 above 0.6) were treated with porcine surfactant (Curosurf), since its efficacy has been demonstrated in a prior clinical trial (Pediatrics 1988; 82: 683-91). The mean birth weight and gestational age were 1,327 +/- 566 g and 29.5 +/- 3.8 weeks, respectively. Twenty-four percent of the babies had an arterial pH below 7.1. At a mean postnatal age of 9.1 +/- 10.7 hours, a dose of 200 mg/Kg of Curosurf was given by the tracheal route. Mean paO2 rose from 47 +/- 14 mm Hg to 166 +/- 64 mm Hg (p less than 0.001). The paO2 increased in 24 of the 25 cases and in 20 (80%) the post-treatment paO2 was a least two times higher than the pre-treatment value. An hour after surfactant treatment, the paCO2 decreased from 58 +/- 21 mm Hg to 45 +/- 16 mm Hg (p less than 0.01) and the pH increased from 7.19 +/- 0.15 to 7.28 less than 0.11 (p less than 0.001). The following complications were observed: pulmonary interstitial emphysema (16%), pneumothorax (8%), patent ductus arteriosus (36%), intraventricular hemorrhage (28%) and bronchopulmonary dysplasia (24%). The neonatal survival rate and the survival rate after discharge from the hospital were 76% and 64%, respectively. The combined survival and absence of DBP was 32%. Nonsurvivors had lower birth weights and gestation ages, as well as lower paO2 5 min after treatment and higher FiO2 24 hours after surfactant treatment than did the survivors.