Antinociceptive properties of intrathecal dexmedetomidine in rats.

Dexmedetomidine is a highly selective alpha 2-adrenoceptor agonist. In this study, the intrathecal administration of dexmedetomidine into the rat lumbar subarachnoid space produced dose-dependent, prolonged antinociception as measured by hot plate and tail flick testing. Intrathecal administration of 3 or 10 micrograms of dexmedetomidine increased hot plate and tail flick latencies to cutoff values within 15 min of injection. Animals receiving 1 microgram of intrathecal dexmedetomidine did not show any significant antinociception when compared to saline controls. The intrathecal administration of the alpha 2-adrenoceptor antagonist, idazoxan, ablated all measurable antinociception produced by the prior injection of 10 micrograms of dexmedetomidine.

The prognostic value of endotracheal tube-air leak following tracheal surgery in children.

In an effort to determine if the endotracheal tube-leak pressure has prognostic value in relation to a successful outcome after one-stage laryngotracheal reconstruction or cricoid split surgery, a retrospective analysis was performed on 17 children who had undergone such surgery. The daily leak pressures, length of intubation, and ultimate outcome of attempts at extubation were noted. One hundred percent of patients with a leak pressure of less than 20 cm H2O on the day before extubation were successfully extubated. In contrast, the failure rate was 100% in children extubated with a leak of greater than 30 mm H2O. The difference between these two groups was statistically significant (chi 2, 13.03). Sixty percent of patients with leak pressures in the range of 21 to 30 cm H2O were successfully extubated. The endotracheal tube-leak pressure is a parameter that has prognostic value, and should be considered in determining when to extubate children who have undergone tracheal reconstructive surgery.

Safety and efficacy of intravenous immunoglobulin prophylaxis in pediatric head trauma patients: a double-blind controlled trial.

Infection is one of the major complications of severe head trauma in children. To assess whether intravenous immunoglobulin (IVIg) decreases the incidence of secondary infection after head injury in children, a randomized, double-blind trial was performed. Thirty-three children (mean age, 6.67 years; mean injury severity score, 32.8; mean Glasgow coma score, 6.1) with severe head injuries were enrolled; 1 child was excluded, 18 received IVIg, and 14 received the placebo preparation. Four hundred milligrams per kilogram of IVIg or albumin placebo was administered within 48 hours of admission. IgG levels were obtained before the infusion and then 1 week later. Patients were monitored for evidence of infection for the next 21 days. There was a 66% increase in mean IgG levels in the treatment group compared with 45% in the control group (P = .057). One death occurred in the IVIg group and two in the placebo group. No significant differences in the incidence of pneumonia, sepsis, presumed sepsis, or any other type of infection was noted. There was no difference in the number of days on mechanical ventilation or in number of hospital days. There were no side effects. It is concluded that prophylactic administration of commercial IVIg at a dose of 400 mg/kg, although safe, had no effect on the incidence of secondary infections in children with severe head injuries.

The effects of fentanyl and sufentanil on intracranial pressure and cerebral blood flow in rabbits with an acute cryogenic brain injury.

The cerebrovascular response to the administration of equipotent doses of fentanyl and sufentanil was evaluated in New Zealand white rabbits following cryogenic brain injury. In a preliminary study consisting of 10 animals, it was documented that the cerebral blood flow response to alterations in the PaCO2 remained intact in this model of brain injury. Subsequently, 28 rabbits were anesthetized with 1.5% halothane in oxygen, paralyzed with pancuronium, and mechanically ventilated. A cryogenic lesion was created over the left hemisphere. One hour later, the intracranial pressure had risen to a mean value of 15 mm Hg. Baseline measurements were then made of monitored variables, which included heart rate, mean arterial pressure, central venous pressure, intracranial pressure, temperature, and arterial blood gases. Global cerebral blood flow was measured utilizing a hydrogen clearance technique. The animals were then randomized to receive an infusion of fentanyl (N = 9, 200 microg/kg), sufentanil (N = 10, 20 microg/kg), or an equal volume of normal saline (N = 9) by i.v. infusion over 5 min. At the conclusion of the opioid infusions, repeated measurements of hemodynamic variables and intracranial pressure were recorded for 15 min and a second cerebral blood flow measurement was made. There were no significant differences in mean arterial pressure, heart rate, central venous pressure, intracranial pressure, cerebral blood flow, or blood gas values between the three groups prior to the administration of fentanyl, sufentanil, or normal saline. At the conclusion of the 5 min infusion, the intracranial pressure had increased by approximately 5 mm Hg in all three groups. The mean arterial pressure decreased to a similar degree in the fentanyl and sufentanil groups and was significantly lower than the mean arterial pressure in the saline group. Although the cerebral perfusion pressure decreased in all three groups, cerebral blood flow was not significantly affected. These results suggest that there is no significant difference in the effects of fentanyl vs. sufentanil on mean arterial pressure, intracranial pressure, or cerebral blood flow in this model of acute brain injury and elevated intracranial pressure.

Effects of THAM and sodium bicarbonate on intracranial pressure and mean arterial pressure in an animal model of focal cerebral injury.

Episodes of arterial hypotension are associated with an increased mortality in head injury patients. Rapid infusion of sodium bicarbonate in such patients may cause hypotension and elevate intracranial pressure. Therefore, we examined the effects of tromethamine (THAM) versus bicarbonate on intracranial pressure and blood pressure in a model of focal cerebral injury. THAM is a buffer that in previous studies has been shown to lower intracranial pressure. After creation of a cryogenic lesion in 13 New Zealand white rabbits, equivalent infusions (15 s duration) of sodium bicarbonate and THAM (2 mEq/kg) were administered sequentially to each animal in random order. Rapid infusion was chosen to simulate the administration of these drugs during a resuscitation. THAM infusion was associated with a significantly lower intracranial pressure and blood pressure than bicarbonate. The fall in blood pressure was great enough that cerebral perfusion pressure after THAM infusion was significantly lower than after bicarbonate infusion. In this model of cerebral injury, rapid infusion of THAM offered no therapeutic advantage over bicarbonate.

Active galaxies. A fast and long-lived outflow from the supermassive black hole in NGC 5548.

Supermassive black holes in the nuclei of active galaxies expel large amounts of matter through powerful winds of ionized gas. The archetypal active galaxy NGC 5548 has been studied for decades, and high-resolution x-ray and ultraviolet (UV) observations have previously shown a persistent ionized outflow. An observing campaign in 2013 with six space observatories shows the nucleus to be obscured by a long-lasting, clumpy stream of ionized gas not seen before. It blocks 90% of the soft x-ray emission and causes simultaneous deep, broad UV absorption troughs. The outflow velocities of this gas are up to five times faster than those in the persistent outflow, and, at a distance of only a few light days from the nucleus, it may likely originate from the accretion disk.

Balloon directed pulmonary blood flow.

Recent advances in pulmonary care have involved improvement in the distribution of ventilation, but improvement in the distribution of pulmonary perfusion in a clinical setting has not been described. In this report, 2 pediatric patients are described with severe aspiration pneumonitis and hypoxia for whom conventional therapy with mechanical ventilation and high PEEP was of limited benefit. A 4-lumen pulmonary artery catheter was placed into the pulmonary artery supplying the lobe most diseased by chest radiograph. Pulmonary blood flow distribution was changed by total and partial inflation and deflation of the pulmonary artery balloon. This resulted in a marked alteration in shunt fraction and allowed significant reduction in F1O2. The pathophysiological and therapeutic implications of manipulating pulmonary artery blood flow distribution with a pulmonary artery catheter are discussed.

Management of acute epiglottitis in pediatric patients.

Of 41 pediatric cases of acute epiglottitis treated at the same institution during an 8-yr period, 33 patients were managed by nasotracheal intubation, one by tracheostomy performed at a referring hospital, and seven by intensive care observation and iv antibiotics. Twenty of the 33 nasotracheally intubated patients underwent intubation in the pediatric ICU by the pediatric anesthesiologist-intensivist, who used iv anesthetic agents and muscle relaxants. The remainder were intubated at referring hospitals. All of the intubated patients were paralyzed, sedated, and mechanically ventilated. The intubation technique caused no apparent complications; however, it required the skill and expertise of an experienced pediatric anesthesiologist-intensivist.

Mediastinal tube placement in children with pneumomediastinum: hemodynamic changes and description of technique.

OBJECTIVE: To describe the technique, hemodynamic response, and complication rate after the insertion of a percutaneous mediastinal tube for drainage of pneumomediastinum. DESIGN: A combined retrospective and prospective study in mechanically ventilated children with pneumomediastinum. SETTING: Multidisciplinary pediatric intensive care unit at a children's hospital. PATIENTS: The medical records and chest radiographs of 25 (15 retrospective and 10 prospective) patients who had placement of a mediastinal tube for drainage of pneumomediastinum from 1990 to 1995 were reviewed. Hemodynamic data were collected prospectively in the ten consecutive children from January 1994 to April 1995. INTERVENTION: Mediastinal tube placement: The subxyphoid area was cleansed with povidone-iodine and draped. An 18-gauge, thin-walled introducer needle was inserted 1 to 2 cm below the xyphoid process at an angle of 20 degrees from the anterior abdominal wall, directed at the substernal space. Either a 9-Fr or 11-Fr pericardiocentesis catheter was inserted over a wire and advanced to the third intercostal space. The catheter was secured and connected to 10 cm H2O suction, using a standard thoracostomy tube drainage device. MEASUREMENTS AND MAIN RESULTS: The size of the mediastinal air column on a lateral chest radiograph was measured before and after placement of the mediastinal tube. The mean change in the size of the mediastinal air column was -1.6 cm (median -1.5, p < .001). In the ten prospective patients, hemodynamic data were recorded immediately before and after placement of a mediastinal tube from previously placed arterial and central venous pressure catheters. The mean hemodynamic changes after the mediastinal tube placement were: heart rate -4 beats/min (median = -1, p = .14); systolic blood pressure 16 mm Hg (median = 10, p = .007); diastolic blood pressure 11 mm Hg (median = 11, p = .005); mean arterial pressure 12 mm Hg (median = 8, p = .005); and central venous pressure -2 mm Hg (median = -1, p = .04). In four patients with pulmonary artery thermodilution catheters, the mean increase in cardiac index immediately following placement of the mediastinal tube was 34%. No complications, including bleeding, cardiac puncture, or infection occurred. CONCLUSIONS: These findings suggest that hemodynamic compromise commonly accompanies pneumomediastinum in children. Decompression of the mediastinal space and drainage of the pneumomediastinum, using this simple bedside technique for continuous drainage, can be performed rapidly and safely in children, resulting in immediate hemodynamic improvement, and allowing for continuous drainage.

Helium-oxygen mixture does not improve gas exchange in mechanically ventilated children with bronchiolitis.

STATEMENT OF FINDINGS: Varying concentrations of helium-oxygen (heliox) mixtures were evaluated in mechanically ventilated children with bronchiolitis. We hypothesized that, with an increase in the helium:oxygen ratio, and therefore a decrease in gas density, ventilation and oxygenation would improve in children with bronchiolitis. Ten patients, aged 1-9 months, were mechanically ventilated in synchronized intermittent mandatory ventilation (SIMV) mode with the following gas mixtures delivered at 15-min intervals: 50%/50% nitrogen/oxygen, 50%/50% heliox, 60%/40% heliox, 70%/30% heliox, and return to 50%/50% nitrogen/oxygen. The use of different heliox mixtures compared with 50%/50% nitrogen/oxygen in mechanically ventilated children with bronchiolitis did not result in a significant or noticeable decrease in ventilation or oxygenation.

New concepts in the treatment of children with acute respiratory distress syndrome.

Recent advances in mechanical ventilation, accompanied with a better understanding of the pathophysiology of ARDS, have resulted in a brighter outlook for the child who acquires this still dreaded disease. A greater understanding of the pathophysiology of ARDS has led to a heightened awareness that the care of these patients should be more than just supportive. The potential for exacerbation of lung injury by mechanical ventilation is real. Many new therapies are being evaluated for the treatment of ARDS; all are intended to reduce ventilator-induced injury. With the recognition of "volutrauma" as a serious complication of mechanical ventilation in ARDS, the mode of ventilation used should minimize the potential for this complication in a child with signs of progressive lung disease requiring mechanical ventilation. Optimal integration of the many new techniques into the treatment of pediatric ARDS will require more research and experience. Surfactant replacement in ARDS as an adjunct to the basic care of these patients may be beneficial. Liquid ventilation is another exciting new ventilation technique that has a significant protective effect in animal models of ARDS. Other therapies, such as tracheal gas insufflation, or other new modes of ventilation may also improve outcome. Techniques of high-frequency ventilation and ECMO in the treatment of children already show potential for improved outcome. The decision between using ECMO or "nonconventional" forms of mechanical ventilation should be considered carefully, after the morbidity of the procedures, the duration of therapy, and the cost have been weighed. Centers with experience using ECMO in the setting of pediatric ARDS have better results than those where ECMO is infrequently used for this purpose. It is imperative that future studies of both mechanical ventilation and ECMO describe ventilation strategy and prospectively identify protocols or algorithms for ventilator management. Coupled with severity scores, ventilator techniques and ECMO can then be systematically compared in children with ARDS.

Mandibular fractures in association with chin trauma in pediatric patients.

The combination of chin trauma and bleeding from the ear should alert the physician to the possibility of a mandibular fracture. Not all hemotympanums represent basilar skull fractures, especially when they occur in association with chin trauma. Diagnosis of mandibular condylar fractures or temporomandibular joint disruptions can be very difficult. A high index of suspicion and a proper choice of imaging modalities are necessary to ensure a timely diagnosis.

Percutaneous catheter drainage of tension pneumatocele, secondarily infected pneumatocele, and lung abscess in children.

OBJECTIVE: To describe the use of percutaneous catheter drainage of tension pneumatocele, secondarily infected pneumatocele, and lung abscess in children. DESIGN: Retrospective case series. SETTING: A 24-bed pediatric intensive care unit. PATIENTS: Patients with tension pneumatocele, secondarily infected pneumatocele, or lung abscess. Tension pneumatocele was defined as an expanding intraparenchymal cyst compressing adjacent areas of the lung. Infected pneumatocele and lung abscess were defined, respectively, as intraparenchymal thin-walled cyst or thick-walled cavity containing an air-fluid level and purulent fluid. INTERVENTIONS: Seven pneumatoceles/lung abscesses were percutaneously drained in five patients. After computed tomography of the chest was obtained to localize the optimum site for drainage, a modified Seldinger technique was used to insert an 8.5-Fr soft catheter percutaneously into the cyst/cavity. The catheter was left in place until drainage (fluid and air) stopped. MEASUREMENTS AND MAIN RESULTS: All patients had clinical and radiologic improvement and were afebrile within 24 hrs after drainage. Bacterial culture grew aerobic bacteria from three cysts/cavities, anaerobic bacteria from one, and mixed bacteria from three. One patient had three secondarily infected pneumatoceles. Four of five secondarily infected pneumatoceles were under tension in two patients receiving mechanical ventilation. In both patients, the trachea was extubated within 24 hrs of drainage after prolonged mechanical ventilation. The number of days the catheter was in place ranged from 1 to 20 days. CONCLUSIONS: Percutaneous catheter drainage of tension pneumatocele, secondarily infected pneumatocele, and lung abscess can be performed safely and effectively in children. Early drainage is helpful, both as a diagnostic and therapeutic procedure. Drainage of tension pneumatocele may assist in weaning from mechanical ventilation. Computed tomography of the chest is helpful in determining the optimum site for percutaneous drainage.

High-frequency pressure-control ventilation with high positive end-expiratory pressure in children with acute respiratory distress syndrome.

OBJECTIVE: Animal models suggest that high-frequency ventilation with low tidal volumes and high positive end-expiratory pressure (PEEP) minimize secondary injury to the lung. We hypothesized that using a high-frequency pressure-control mode of ventilation with high PEEP in children with severe acute respiratory distress syndrome (ARDS) would be associated with improved survival. DESIGN: The study was a retrospective and prospective clinical study at a 24-bed tertiary care pediatric critical care unit. Fifty-three patients with severe ARDS were studied during a 37-month period, 30 prospectively and 23 retrospectively. Severe ARDS was defined as (1) rapid onset of severe bilateral infiltrates of noncardiac origin, (2) partial pressure of oxygen (arterial)/fraction of inspired oxygen less than 200 on PEEP of 6 cm H2O or more for 24 hours or longer, and (3) Murray disease severity score greater than 2.5. All patients meeting these criteria underwent ventilation in the pressure-control mode; the protocol for ventilation had the following general guidelines: (1) fraction of inspired oxygen limited to 0.5, (2) mean airway pressure titrated with PEEP to maintain arterial partial pressure of oxygen of 55 mm Hg or greater (7.3 kPa), (3) peak inspiratory pressure minimized to allow hypercapnia (arterial partial pressure of carbon dioxide, 45 to 60 mm Hg (6.0 to 8.0 kPa), and (4) ventilator rates of 40 to 120/min. Percutaneous thoracostomy and mediastinal tubes were placed for treatment of air leak. RESULTS: The survival rate was 89% (47/53) in children with severe ARDS. Nonsurvivors had significantly higher peak inspiratory pressures (75 vs 40 cm H2O, p = 0.0006), PEEP (23 vs 17 cm H2O, p = 0.0004), mean airway pressure (40 vs 28 cm H2O, p = 0.04), alveolar-arterial oxygen gradient (579 vs 540 mm Hg, p = 0.03), and oxygenation index (43 vs 19, p = 0.0008) than survivors. Air leak was present in 51% of patients; there was no difference in the incidence of air leak between survivors and nonsurvivors (p = 0.42). CONCLUSIONS: The high-frequency positive-pressure mode of ventilation was safe and was associated with an improved survival rate (89%) for children with severe ARDS. Limitation of both inspired oxygen and tidal volume, along with aggressive treatment of air leak, may have contributed to the improved survival rate.

Continuous intravenous terbutaline for pediatric status asthmaticus.

OBJECTIVES: To determine the clinical effects of intravenous terbutaline at >0.4 microg/kg/min in children with status asthmaticus; to describe the clinical findings associated with such therapy, including creatinine phosphokinase-myocardial band isoenzyme (CPK-MB) concentrations, electrocardiographic alterations, and decreased diastolic blood pressure (DBP) with terbutaline usage; and to assess the requirement for epinephrine to counteract the decrease in diastolic blood pressure. DESIGN: A retrospective review of children admitted with status asthmaticus who failed emergency room therapy and required intravenous terbutaline. SETTING: San Diego Children's Hospital Pediatric Intensive Care Unit. PATIENTS: Eighteen children with status asthmaticus, based on clinical and laboratory criteria, between September 1994 and July 1996. INTERVENTIONS: Epinephrine was added for below-normal decreases in diastolic blood pressure. MEASUREMENTS AND MAIN RESULTS: Continuous monitoring for arrhythmias, ST-segment changes, and DBP values during variations in the dose of intravenous terbutaline, with or without epinephrine. CPK-MB concentrations were determined in 15 of 18 patients. CONCLUSIONS: Intravenous terbutaline was well tolerated in asthmatic children for < or =305 continuous hours and at varying doses up to a maximum of 10 microg/kg/min. There was no relationship between the magnitude of CPK-MB concentrations and the terbutaline or epinephrine doses used. Arrhythmias were rare and not related to either terbutaline or epinephrine doses. However, ST-segment depression did occur in two patients requiring high-dose epinephrine. Terbutaline significantly lowered DBP when used between 0.4 and 1.0 microg/kg/min, which required epinephrine to be initiated. Epinephrine was not required at terbutaline doses of >2 microg/kg/min. There was no mortality.

Successful organ donation in victims of child abuse.

Organ transplantation has become a valuable and accepted treatment for many patients with organ failure. A major limitation to transplantation is the shortage of organ donors. Due to lack of willingness by medical examiners to release child abuse cases for organ donation, child abuse victims are a greatly underutilized pool of potential donors. This paper presents a model to facilitate organ recovery in the child abuse victim. This protocol has been in consistent use in San Diego County since midyear 1991. In all cases of child abuse where the victim was brain dead and the family consented to organ donation, the medical examiner's office released the body for organ donation. Since institution of the model described in this paper, organ donation among child abuse victims has risen dramatically in San Diego County. If similar protocols are established at other pediatric centers, the disparity between supply and demand in pediatric organ donation will diminish.