Predictors of outcome of severe respiratory syncytial virus-associated respiratory failure treated with extracorporeal membrane oxygenation

Extracorporeal Membrane Oxygenation in Pediatric Burn Patients Without Inhalation Injury: A Unique Population?

Prolonged mechanical ventilation (MV) before the initiation of extracorporeal membrane oxygenation (ECMO) is associated with decreased survival. Pediatric burn patients without inhalational injury are a unique population as they may be intubated for longer durations due to frequent interventions such as dressing changes and burn excisions. This study utilized the Extracorporeal Life Support Organization registry and evaluated patients 0 to 18 years old placed on ECMO and with a burn injury from January 2010 to December 2020. Inhalation injury was excluded. Descriptive statistics and bivariate analyses were performed. Multivariable logistic regression was used to assess the association between mortality and precannulation MV duration before ECMO cannulation, and odds ratios and predicted probabilities of mortality were estimated. Our cohort of 47 patients had a median age of 2.7 years old. Mortality occurred in 48.9% of the cohort. The overall median number of days on ECMO was 6.3 days, with no difference between survivors and non-survivors (6.8 days vs 6.3 days; P = .67). Survivors were ventilated for 4.1 days and non-survivors for 4.8 days before cannulation (P = .25). Regression modeling demonstrated that with each additional day on MV before ECMO cannulation, the odds of mortality increases by 12% (P = .03). Our study suggests that, similar to pediatric patients without thermal injury, increasing precannulation MV duration is associated with an increasing risk of mortality in pediatric burn patients without inhalational injury. Though the pediatric burn population is unique, evaluation of burn patients with respiratory failure for ECMO should be similar to the general population.

Extracorporeal Membrane Oxygenation for Severe Pediatric Respiratory Failure

Extracorporeal membrane oxygenation (ECMO) was developed initially in the 1960s to support refractory respiratory failure in addition to the cardiac support inherent in a venoarterial bypass circuit. Early successes occurred predominantly in the neonatal population with subsequent randomized controlled trials and comprehensive reviews concluding therapeutic efficacy for ECMO in neonatal respiratory failure. In contrast, the evidence supporting ECMO for respiratory failure in children is less definitive. However, although pediatric randomized controlled trials have not been completed, sufficient evidence in support of ECMO as a beneficial therapy for pediatric respiratory failure exists. The acceptance of clinical utility and benefit from ECMO for pediatric ARDS and the trend toward increasing venovenous ECMO use have led to its inclusion in the Pediatric Acute Lung Injury Consensus Conference as a strongly agreed upon recommendation for severe pediatric ARDS. However, the Pediatric Acute Lung Injury Consensus Conference recommendations supporting the use of ECMO for pediatric ARDS highlight the lack of evidence-based selection criteria when determining ECMO candidacy in pediatric patients with ARDS. Ultimately, decisions to proceed with ECMO and the concomitant risk of potential life-threatening complications must consider multiple factors that balance potential risks and likelihood of benefit, pre-morbid conditions and impact on potential post-ECMO quality of life, candidacy for lung transplantation, and patient and family goals of care. This review will discuss ECMO for the support of pediatric respiratory failure, ventilator management during ECMO, considerations impacting timing of decannulation, and developing techniques.

FiO2 predicts outcome in infants with respiratory syncytial virus-induced acute respiratory distress syndrome

OBJECTIVE

Respiratory syncytial virus (RSV) infection can progress to acute respiratory distress syndrome (ARDS) in infants. ARDS is a life-threatening condition that is characterized by severe hypoxemia, defined as PaO(2)/FiO(2) ratio <300 mmHg. This ratio is used in many trials as the sole oxygenation criterion for ARDS. Recently, however, it has been shown in adults with ARDS that FiO(2), independently of the PaO(2)/FiO(2) ratio predicts mortality. Because epidemiology and outcome of ARDS differ strongly between children and adults, we determined if FiO(2) on admission (baseline FiO(2)) independently predicted the duration of mechanical ventilation (MV) and length of stay (LOS) in the pediatric intensive care unit (PICU) in infants with RSV-induced ARDS.

DESIGN

Retrospective observational study.

SETTING

A 14-bed pediatric intensive care unit.

PATIENTS

One hundred twenty-nine mechanically ventilated infants with RSV-induced ARDS.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Independent predictors for outcome, including baseline FiO(2) and PEEP, were analyzed using the cox regression model. Endpoints were duration of MV and LOS in the PICU. A higher baseline FiO(2) was independently associated with a longer duration of MV (HR 0.12, CI 0.02-0.87, P = 0.036) and increased LOS in the PICU (HR 0.09, CI 0.01-0.57, P = 0.023). Neither baseline PEEP nor PaO(2)/FiO(2) ratio correlated with outcome.

CONCLUSIONS

FiO(2) level independently predicted outcome in infants with RSV-induced ARDS, whereas both PEEP and the PaO(2)/FiO(2) ratio did not. This suggests that FiO(2) should be taken into account in defining disease severity in infants with RSV-induced ARDS.

Current knowledge of acute lung injury and acute respiratory distress syndrome

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) continues to be a major cause of mortality in adult and pediatric critical care medicine. This article discusses the pulmonary sequelae associated with ALI and ARDS, the support of ARDS with mechanical ventilation, available adjunctive therapies, and experimental therapies currently being tested. It is hoped that further understanding of the fundamental biology, improved identification of the patient's inflammatory state, and application of therapies directed at multiple sites of action may ultimately prove beneficial for patients suffering from ALI/ARDS.

Critical appraisal of Zabrocki et al: Extracorporeal membrane oxygenation for pediatric respiratory failure: survival and predictors of mortality. Crit Care Med 2011; 39:364-370

OBJECTIVE

To review the findings and discuss the implications of pediatric respiratory failure treated with extracorporeal membrane oxygenation.

DESIGN

A critical appraisal of Extracorporeal membrane oxygenation for pediatric respiratory failure: Survival and predictors of mortality by Zabrocki et al (Crit Care Med 2011; 39:364370) and review of the relevant literature.

FINDINGS

In this review of international data from 1993 to 2007, pediatric patients diagnosed with respiratory failure that met inclusion criteria and were treated with extracorporeal membrane oxygenation had an overall survival of 57%. This percentage did not change significantly over the study period; however, the number of patients with comorbidities did increase from 19% in 1993 to 47% in 2007. Survival varied significantly depending on diagnosis (83% for status asthmaticus vs. 23% for fungal pneumonia) and associated comorbidities (59% for chronic lung disease vs. 5% for hematopoietic stem cell transplantation). Clinical features associated with decreased survival included precannulation mechanical ventilation in excess of 14 days and venoarterial cannulation.

CONCLUSIONS

This study confirms that precannulation diagnoses and variables play a role in prognosis when pediatric patients with respiratory failure are treated with extracorporeal membrane oxygenation. Results of this investigation demonstrate that survival is improving in patients without comorbidities and that patients can be mechanically ventilated for up to 14 days prior to extracorporeal support initiation before mortality is increased.

Factors associated with mortality in pediatric patients requiring extracorporeal life support for severe pneumonia

OBJECTIVES

In children with respiratory failure secondary to pneumonia, extracorporeal life support can be lifesaving. Our goal was to identify variables associated with mortality in children with pneumonia requiring extracorporeal life support.

DESIGN

Data query and abstraction from a multicenter, international registry of extracorporeal life support, the Extracorporeal Life Support Organization Registry.

SETTING

Extracorporeal Life Support Organization registry data from 1985 to 2010.

PATIENTS

Patients ≤ 18 yr of age who received extracorporeal life support for respiratory failure secondary to pneumonia.

INTERVENTIONS

None.

MEASUREMENTS AND OUTCOMES

Clinical variables, year of extracorporeal life support, and extracorporeal life support center location were collected. The primary outcome was survival at hospital discharge. Results are reported as predictive margins, which allow estimation of standardized mortality rates and differences for risk factors.

RESULTS

One thousand four hundred eighty-nine children were included. The median (interquartile range) age and duration of extracorporeal life support were 5.7 months (2.5-21.5) and 11 days (7-18). Arterial cannulation was performed in 65% of patients. Mortality was 39%. There was no relationship between mortality and age or pathogen. Duration of extracorporeal life support had a biphasic relationship on mortality; mortality decreased 1.3% per day on extracorporeal life support until 14 days and then increased by 1.8% per day thereafter. Other independent predictors of mortality (p < 0.05) were pre-extracorporeal life support factors including duration of mechanical ventilation, peak inspiratory pressure, arterial oxygen saturation, pH, cardiac arrest, need for an arterial cannula, decade of extracorporeal life support, international extracorporeal life support center, and decrease in FIO2 over the first 24 hrs on extracorporeal life support.

CONCLUSIONS

In children with severe pneumonia receiving extracorporeal life support, prognostic factors associated with increased risk of death included extracorporeal life support treatment exceeding 14 days, arterial cannulation, longer duration of mechanical ventilation, and decreased ability to wean ventilator FIO2 over the first 24 hrs on extracorporeal life support. Analysis of the Extracorporeal Life Support Organization registry can identify prognostic variables, which may influence medical decision making, resource utilization, and family counseling.

Prolonged extracorporeal membrane oxygenation for children with respiratory failure

OBJECTIVE

Extracorporeal membrane oxygenation is used to support children with respiratory failure. When extracorporeal membrane oxygenation duration is prolonged, decisions regarding ongoing support are difficult as a result of limited prognostic data.

DESIGN

Retrospective case series.

SETTING

Multi-institutional data reported to the Extracorporeal Life Support Organization Registry.

PATIENTS

Patients aged 1 month to 18 yrs supported with extracorporeal membrane oxygenation for respiratory failure from 1993 to 2007 who received support for ≥ 21 days.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of the 3213 children supported with extracorporeal membrane oxygenation during the study period, 389 (12%) were supported ≥ 21 days. Median patient age was 9.1 months (interquartile range, 2.5-41.7 months). Median weight was 6.7 kg (interquartile range, 3.5-15.8 kg). Survival for this group was 38%, significantly lower than survival reported for children supported ≤ 14 days (61%, p < .001). Among children supported with extracorporeal membrane oxygenation for ≥ 21 days, no differences were found between survivors and nonsurvivors with regard to acute pulmonary diagnosis, pre-extracorporeal membrane oxygenation comorbidities, pre-extracorporeal membrane oxygenation adjunctive therapies, or pre-extracorporeal membrane oxygenation blood gas parameters. Only peak inspiratory pressure was significantly different in survivors. Complications occurring on extracorporeal membrane oxygenation were more common among nonsurvivors. The use of inotropic infusion (odds ratio 1.64; 95% confidence interval 1.07-2.52), acidosis (pH <7.2) during extracorporeal membrane oxygenation (odds ratio 2.62; 95% confidence interval 1.51-4.55), and male gender (odds ratio 1.95; 95% confidence interval 1.21-3.15) were independently associated with increased odds of death.

CONCLUSION

Survival declines with duration of extracorporeal membrane oxygenation. Male gender and inadequate cardiorespiratory status during extracorporeal membrane oxygenation increased the risk of death. Prolonged support with extracorporeal membrane oxygenation appears reasonable unless multiorgan failure develops.

Extracorporeal membrane oxygenation for pediatric respiratory failure: Survival and predictors of mortality

OBJECTIVE

The last multicentered analysis of extracorporeal membrane oxygenation in pediatric acute respiratory failure was completed in 1993. We reviewed recent international data to evaluate survival and predictors of mortality.

DESIGN

Retrospective case series review.

SETTING

The Extracorporeal Life Support Organization Registry, which includes data voluntarily submitted from over 115 centers worldwide, was queried. The work was completed at the Division of Pediatric Critical Care, Department of Pediatrics, Primary Children's Medical Center, University of Utah, Salt Lake City, UT.

SUBJECTS

Patients aged 1 month to 18 yrs supported with extracorporeal membrane oxygenation for acute respiratory failure from 1993 to 2007.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

There were 3,213 children studied. Overall survival remained relatively unchanged over time at 57%. Considerable variability in survival was found based on pulmonary diagnosis, ranging from 83% for status asthmaticus to 39% for pertussis. Comorbidities significantly decreased survival to 33% for those with renal failure (n = 329), 16% with liver failure (n = 51), and 5% with hematopoietic stem cell transplantation (n = 22). The proportion of patients with comorbidities increased from 19% during 1993 to 47% in 2007. Clinical factors associated with mortality included precannulation ventilatory support longer than 2 wks and lower precannulation blood pH.

CONCLUSIONS

Although the survival of pediatric patients with acute respiratory failure treated with extracorporeal membrane oxygenation has not changed, this treatment is currently offered to increasingly medically complex patients. Mechanical ventilation in excess of 2 wks before the initiation of extracorporeal membrane oxygenation is associated with decreased survival.

The evolution of patient selection criteria and indications for extracorporeal life support in pediatric cardiopulmonary failure: next time, let's not eat the bones

Bill James, baseball statistician and author, tells the story of hungry cavemen sitting about a campfire, waiting for tomatoes to ripen. One has the inspiration to throw an ox on the fire, and the first barbecue ensued and was endured. After eating, the conversation goes something like this. "There were some good parts." "Yeah, but there were some bad parts." And the smart one says, "This time, let's not eat the bones." The evolution of patient selection criteria for the use of extracorporeal support (ECLS) is a bit like those cavemen and their first barbecued ox. Extracorporeal life support technology and application to patient care is the unique result of a long standing history of ambitious attempt, evaluation, debate, collaboration and extension.

Factors associated with survival in pediatric extracorporeal membrane oxygenation--a single-center experience

AIM

We aimed to examine outcomes of extracorporeal membrane oxygenation (ECMO) therapy in the pediatric population and identify pre-ECMO and on-ECMO characteristics that are associated with survival.

METHODS

We retrospectively reviewed the ECMO records at our institution between 1999 and 2008 and selected pediatric patients who were cannulated for respiratory failure or hemodynamic instability resistant to conventional interventions. We recorded details of pre-ECMO clinical characteristics, including blood gas variables and mechanical ventilatory support, and details of ECMO therapy including survival off ECMO and to hospital discharge. Predictors of survival were analyzed using logistic regression modeling and a prediction algorithm was developed.

RESULTS

Of the 445 ECMO runs, data from 58 consecutive patients were analyzed: 57% were successfully decannulated, and 48% survived to discharge from the hospital. The cohort included 32 (55%) female patients, 22 postoperative patients (38%), and 15 (26%) with an immunosuppressive condition, with a median age of 5 years and weight 19.5 kg, The mean duration of pre-ECMO respiratory support was 3 days, in the form of high-frequency oscillatory ventilation (n = 28, 48%) and conventional mechanical ventilation (n = 13, 22%). The median duration (interquartile range) of ECMO support was 142 hours (60, 321) or 5.9 days. Pre-ECMO pH above 7.2 (P < .001) and oxygenation index below 35 (P = .021) were associated with the highest survival rates. Pre-ECMO PaCO(2) and duration of mechanical ventilation were not associated with survival.

CONCLUSIONS

Based on our results, ECMO therapy should be considered early in children with oxygenation index greater than 35 with worsening metabolic status. The restriction of ECMO based on ventilator days alone needs to be revisited in this era of lung protective ventilation.

Serious and lethal respiratory tract infections of viral etiology in children

Viruses may lead to serious and lethal pulmonary infections in immunocompetent and immunocompromised children. Series of children with acute respiratory distress syndrome and series of children requiring extracorporeal membrane oxygenation, as well as reported series of nosocomial viral illness, offer an insight into the extent of serious viral disease documented in the medical literature. Series of children with specific viral respiratory illness also will be reviewed, as will the means of diagnosis in these groups of patients. Copyright © 2000 by W.B. Saunders Company

Current treatment for acute viral bronchiolitis in infants

This paper provides an update and critical review of available data on the treatment of acute viral bronchiolitis in previously healthy infants, with special focus on new or promising therapies. The main potential benefits of medical assistance in these patients reside in the careful monitoring of their clinical status, the maintenance of adequate hydration and oxygenation, the preservation of the airway opened and cleared of secretions and the option to perform parental education. There is no convincing evidence that any other form of therapy will reliably provide beneficial effects in infants with bronchiolitis and currently, any treatment beyond supportive care should be prescribed on a case-by-case basis with watchful appraisal of its effects. Therapies such as ribavirin, IFN, vitamin A, antibiotics, mist therapy or anticholinergics, have not demonstrated any measurable clinical effect. Several studies and meta-analyses with beta(2)-agonists and corticosteroids have failed to show any benefit of significant extent, however, physicians keep favouring their use. Presently, adrenaline has received rather consistent support from clinical trials but it is not yet widely prescribed. There are other therapeutic strategies, for instance, heliox, hypertonic saline, noninvasive ventilation, physical therapy techniques, thickened feeds or palivizumab that have shown promising potential benefits, but evidence supporting its use is still limited and further studies should be warranted. In the meantime, infants with acute viral bronchiolitis should be treated following evidence-based clinical practice guidelines, keeping the patient central in the process and being sensitive to social, cultural and familiar influences on their treatment strategy.

Pediatric Extracorporeal Life Support After High Frequency Ventilation: Predictors of Survival

Previous studies of extracorporeal life support in pediatric patients have identified variables associated with survival. However, none of these studies focused on extracorporeal life support after failure of high frequency ventilation (HFV). In the present study, we determined variables associated with survival for pediatric respiratory failure patients who received HFV prior to extracorporeal life support, using data reported to the Extracorporeal Life Support Organization Registry from 1992 to 1998. Patients with neonatal diagnoses, immune compromising conditions, or congenital cardiac defects were excluded. The 243 patients who met inclusion criteria had a 58% survival rate (95% CI 48-66%). The mean age was 22 +/- 39 months. Mean duration of mechanical ventilation prior to extracorporeal life support was 6.6 +/- 5.8 days. Venoarterial extracorporeal life support was used in 72% of the patients; venovenous in 28%. The survival rate for the subset of patients with an oxygenation index greater than 42 cm H2O/torr on HFV (n = 122) was not significantly different from the overall sample. We determined that lower mean airway pressure, lower pressure amplitude, decreased oxygenation index, increased PaO2, and increased oxygen saturation on HFV were associated with increased survival in patients who were subsequently treated with extracorporeal life support.

Acute respiratory distress syndrome caused by respiratory syncytial virus

Acute respiratory distress syndrome (ARDS) complicating severe respiratory syncytial virus (RSV) infection has been described in only a few infants. In contrast to the low mortality rates usually associated with RSV infections (< 5%), mortality rates in the range of 40-70% have been reported in pediatric patients with ARDS. However, studies on patients with ARDS are usually lumped with respect to causation, and the disease course of RSV-induced ARDS has not been previously studied. We examined the pulmonary function abnormalities of 37 infants with RSV-induced respiratory failure who were admitted to our pediatric intensive care unit for assisted ventilation. Measurements included respiratory mechanics, maximum expiratory flow-volume curves, and lung volumes. These allowed the calculation of a Murray lung injury score (modified for pediatric use) in which radiographic findings, ventilator settings, lung compliance, and blood gas results were considered. We identified ten infants with severe restrictive lung disease who fulfilled the clinical criteria for classification as ARDS. All had lung injury scores above 2.5, compatible with a diagnosis of ARDS. Twenty-seven infants had obstructive patterns of lung function consistent with a clinical diagnosis of RSV bronchiolitis. The patients with RSV-induced ARDS were significantly younger, and had a longer time on assisted ventilation (P < 0.05) and a higher proportion of predisposing illnesses (P < 0.05, odds ratio = 6.67, two-tailed Fisher's exact test) when compared with the patients who had obstructive disease. Only one patient (who had immunodeficiency) died, and all others were successfully managed on conventional mechanical ventilation. We conclude that RSV-induced respiratory failure represents a relatively benign cause of ARDS in pediatric patients. Our observations support the notion of differentiating ARDS with respect to causation, especially when novel and experimental therapy is considered and mortality rates are analyzed.

Extracorporeal life support for the treatment of viral pneumonia: collective experience from the ELSO registry. Extracorporeal Life Support Organization

Viral pneumonia is the most common indication for pediatric extracorporeal life support (ECLS). Despite this fact, no previous studies have directly stratified patient outcome according to viral etiology.

METHODS

Using the Extracorporeal Life Support Organization (ELSO) registry database, the authors reviewed the national experience of patients undergoing ECLS with culture or serologically demonstrated viral pneumonia and compared outcome parameters according to viral etiology.

RESULTS

Patients differed with respect to age and weight according to the viral type. Patients with respiratory syncytial virus (RSV, median age 3 months), herpes simplex virus (HSV, 0.13 months), cytomegalovirus (CMV, 2.5 months), and adenovirus (0.6 months) were younger than those with other viruses (5.5 months). The patient groups did not significantly differ with respect to pre-ECLS Pao2 mean airway pressure (MAP), oxygenation index (OI), mode, or duration of ECLS. The overall survival of patients with viral pneumonia was 57%, although patients with RSV or CMV were found to have a 67% survival. Patients infected with HSV and adenovirus had a significantly lower survival rate (31% and 25%, respectively) when compared with those with RSV. In addition RSV pneumonia was associated with fewer cardiovascular complications than several of the other viral types. When comparison was made between survivors and nonsurvivors, a higher last pre-ECLS MAP and increased incidence of elevated creatinine and renal failure requiring dialysis were noted among nonsurvivors.

CONCLUSION

ECLS remains an important modality in the treatment of neonatal and pediatric patients with respiratory failure secondary to viral pneumonia. The survival rate of these patients varies according to the type of viral infection.

The impact of gender on outcome from mechanical ventilation

OBJECTIVE

To determine the relation of gender to outcome for patients requiring mechanical ventilation.

DESIGN

A prospective cohort study.

SETTING

Medical and surgical ICUs in two university-affiliated teaching hospitals.

PATIENTS

Three hundred fifty-seven patients requiring mechanical ventilation.

INTERVENTIONS

Prospective patient surveillance and data collection.

MEASUREMENTS AND RESULTS

The primary outcome measure was hospital mortality. Secondary outcome measures included need for reintubation, hospital and ICU length of stay, duration of mechanical ventilation, and hospital charges. The hospital mortality rate for women (n = 189) was significantly greater than the hospital mortality rate for men (n = 168) (28.0% vs 17.3%; p = 0.016). This difference in hospital mortality was observed despite similar baseline demographic characteristics, severity of illness, indications for mechanical ventilation, and number of dysfunctional organ systems in these two groups of patients. The duration of mechanical ventilation and ICU length of stay was also significantly longer for female patients compared with male patients (p < or = 0.056). In a logistic-regression analysis, female gender was found to be independently associated with hospital mortality (adjusted odds ratio [AOR] = 2.38; 95% confidence interval [CI] = 1.70 to 3.35; p = 0.010). The presence of ARDS (AOR = 10.69; 95% CI = 5.86 to 19.51; p < 0.001), the number of dysfunctional organ systems (AOR = 2.07; 95% CI = 1.78 to 2.41; p < 0.001), Acute Physiology and Chronic Health Evaluation (APACHE) II predicted mortality (AOR = 1.15; 95% CI = 1.11 to 1.19; p < 0.001), and patient age (AOR = 1.04; 95% CI = 1.03 to 1.06; p < 0.001) were also found to be independently associated with hospital mortality. The number of dysfunctional organ systems present at the start of mechanical ventilation was the major independent predictor of hospital mortality (54% of total explanatory power). Patient gender was the least important independent predictor of hospital mortality (5% of total explanatory power).

CONCLUSIONS

In this patient cohort, women requiring mechanical ventilation were at greater risk for hospital mortality than men. Physicians should be aware that outcome differences according to gender can occur when evaluating or designing clinical trials involving mechanically ventilated patients. Future studies are necessary to determine the general applicability of these findings and to identify explanations for such observed gender-specific differences in outcome.

Mechanical ventilation and arterial blood gas measurements 24 hours postextracorporeal life support for survivors of pediatric respiratory failure

OBJECTIVE

To summarize our institutional experience concerning mechanical ventilation support and blood gas measurements in the 24-hr period following extracorporeal life support (ECLS) for pediatric acute respiratory failure.

DESIGN

Descriptive study.

SETTING

A tertiary pediatric referral center.

PATIENTS

Children aged 1 month to 18 yrs treated with ECLS for acute respiratory failure at University of Michigan Hospitals from November 1982 to June 1993. All patients aged 1 month to 18 yrs who received ECLS for acute respiratory failure were included. Patients who received ECLS primarily for cardiac support or who had a diagnosis of congenital gastrointestinal malformation (i.e. congenital diaphragmatic hernia) were excluded.

INTERVENTIONS

ECLS for severe pediatric respiratory failure.

MEASUREMENTS AND MAIN RESULTS

Forty-nine children were treated at our center with ECLS for acute respiratory failure 36 (73%) survived. Ventilator settings immediately after decannulation from ECLS for survivors were as follows: FIO2 0.53 +/- 0.18 (SD); intermittent mandatory ventilation (IMV) 29.6 +/- 1.18 breaths/min, positive end-expiratory pressure 5.3 +/- 1.6 cm H2O, mean airway pressure 12.6 +/- 2.9 cm H2O, and peak inspiratory pressure 31.7 +/- 5.5 cm H2O. Arterial blood gas measurements at decannulation were PaO2 89.4 +/- 30.9 torr (11.9 +/- 4.1 kPa), PaCO2 43.7 +/- 9.7 torr (5.8 +/- 1.3 kPa), and pH 7.39 +/- 0.07. Twenty-four hours after decannulation, ventilator settings and arterial blood gas measurements were as follows: FIO2 0.42 +/- 0.14, IMV 27.4 +/- 13.5 breaths/min, positive end-expiratory pressure 5.2 +/- 1.6 cm H2O, mean airway pressure 12.0 +/- 3.4 cm H2O, peak inspiratory pressure 31.1 +/- 6.5 cm H2O, PaO2 77.0 +/- 16.9 torr (10.3 +/- 2.3 kPa), PaCO2 44.9 +/- 8.4 torr (6.0 +/- 1.1 kPa), and pH 7.40 +/- 0.07. Variables associated with oxygenation status (P[A-a]O2) and mean airway pressure (oxygenation index) improved during the immediate 24-hr period postbypass (p < .05).

CONCLUSIONS

Successful decannulation from ECLS for > 24 hrs resulted in long-term survival in 97% (36/37) of children. Ventilator parameters and arterial blood gas measurements during the 24-hr period following bypass have been described for this population. Such conventional support may indicate safe levels of oxygen and mechanical ventilation pressures for the postbypass recovering lung.

Invasive monitoring in infants with respiratory syncytial virus infection

OBJECTIVE

Coincident with a change in the physician staff in our pediatric intensive care unit (PICU), the frequency and duration of invasive monitoring were decreased. We examined the impact of this change on outcomes, complications, and hospital charges in infants admitted to the PICU with respiratory syncytial virus (RSV) infection.

STUDY DESIGN

We reviewed medical records of all children less than 1 year of age who were admitted to the PICU from January 1989 to July 1993 with confirmed RSV infection. Patient characteristics, therapeutic interventions, outcomes, and hospital charges were extracted and compared.

RESULTS

Seventy-eight patients were identified, 38 admitted from January 1989 through July 1991 (group 1) and 40 from July 1991 through July 1993 (group 2). The groups were well matched in age, preexisting disease, and cardiorespiratory status on admission. Group 1 had significantly greater use of invasive monitoring, pharmacologic paralysis, inotropes, blood products, antibiotics, and parenteral nutrition. Outcomes were not different, but group 1 patients had significantly longer stays, more complications, and higher hospital charges.

CONCLUSIONS

Routine use of invasive monitoring of PICU patients with RSV disease was associated with increased laboratory testing, overtreatment, and significant increases in costs and morbidity without improvement in outcome.

Viral respiratory infections

Viral infections constitute more than 60% of acute lower respiratory illnesses. Respiratory syncytial virus (RSV) and parainfluenza viruses are the most frequent etiologic agents. After transmission by large droplet aerosol or direct contact, the viruses gain entry into host cells through specific viral surface proteins; subsequently, pathogenetic mechanisms cause tissue injury and result in clinical disease. In the intensive care unit the mainstay of treatment is primarily supportive. Nonspecific treatment may include nebulized beta-agonists, aminophylline, and steroids. Ribavarin is the only specific antiviral agent approved for respiratory syncytial virus infection but its efficacy remains controversial. New therapies and vaccines offer hope for improved outcome from viral respiratory infections such as RSV.

Acute effects of inhaled nitric oxide in children with severe hypoxemic respiratory failure

To determine the physiologic effects of inhaled nitric oxide (NO) on oxygenation and hemodynamics in children with severe hypoxemic respiratory failure, we studied the acute response to inhaled NO during mechanical ventilation in 17 pediatric patients. Diagnoses included adult respiratory distress syndrome (ARDS) (10 patients), bronchopulmonary dysplasia with viral pneumonitis (6 patients), and acute pneumonitis, caused by respiratory syncytial virus, without chronic lung disease (1 patient). Gas exchange and hemodynamic measurements were compared before and during exposure to inhaled NO (20 ppm) without changing ventilator settings for 30 minutes. Hemodynamic variables, including pulmonary artery pressure, pulmonary capillary wedge pressure, and cardiac index, were measured in 10 patients with ARDS. Inhaled NO acutely improved oxygenation in 15 of 17 patients; mean arterial oxygen tension increased from 58 +/- 13 mm Hg (baseline) to 86 +/- 25 mm Hg after 30 minutes (p < 0.01). Inhaled NO lowered mean pulmonary artery pressure (42 +/- 6 mm Hg at baseline to 31 +/- 6 mm Hg; p < 0.01) and intrapulmonary shunt (39% +/- 7% vs 32% +/- 7%; p < 0.01) without changing systemic arterial pressure or pulmonary capillary wedge pressure. Cardiac index increased by 14% (p < 0.01). Fifteen patients were subsequently treated with low-dose inhaled NO (3 to 10 ppm) for 1 to 24 days; 5 (50%) of 10 patients with ARDS and 7 (100%) of the 7 non-ARDS patients survived. We conclude that inhaled NO acutely improves oxygenation and lowers pulmonary vascular resistance without causing adverse hemodynamic effects in severe hypoxemic respiratory failure in pediatric patients. Inhaled NO may be a useful adjuvant therapy in children with acute hypoxemic respiratory failure, including infants with bronchopulmonary dysplasia, but whether prolonged low-dose inhalational NO therapy can reduce morbidity or improve survival rates remains unknown.

Extracorporeal life support for severe pediatric respiratory failure: an updated experience 1991-1993

OBJECTIVE

The purpose of this study was to examine our recent experience with children who had acute respiratory failure managed with extracorporeal life support (ECLS) from 1991 to 1993, to determine whether a change in survival rate had occurred in comparison with our previous experience.

DESIGN

Historic and prospective cohort study.

SETTING

A tertiary pediatric referral center.

PATIENTS

All non-neonatal pediatric patients treated with ECLS for severe, life-threatening respiratory failure were examined. Overall, 25 patients have been managed with this life-support technique in the past 28 months. Eighty-four percent (21/25) were transferred to our medical center because of failure of conventional mechanical ventilation therapy. Descriptive data of the recent cohort were as follows (mean +/- SD): age 60 +/- 75 months, weight 23.6 +/- 24.8 kg, and male gender 44%. Duration of intubation before ECLS was 5.8 +/- 2.7 days. Arterial blood gas values and ventilator settings immediately before ECLS were as follows: fraction of inspired oxygen, 0.98 +/- 0.08; mean airway pressure, 21.6 +/- 6.2 cm H2O; peak inspiratory pressure, 45.5 +/- 9.6 cm H2O; positive end-expiratory pressure, 11.0 +/- 4.3 cm H2O; partial pressure of oxygen (arterial), 56 +/- 20 mm Hg (7.4 +/- 2.7 kilopascals); partial pressure of carbon dioxide (arterial), 46 +/- 17 mm Hg (6.1 +/- 2.3 kPa); and estimated alveolar-arterial oxygen tension difference, 572 +/- 81 mm Hg (76.3 +/- 10.8 kPa). Mean duration of ECLS was 373 +/- 259 hours. Of 25 recently treated patients, 22 (88%) survived their life-threatening respiratory illness to be discharged home; this represented a statistically improved survival rate in comparison with the 58% survival rate previously reported by us for similar patients (p < 0.05). Comparisons of arterial blood gas and mechanical ventilation-related variables measured 24 hours before and again immediately before bypass were similar in the two cohorts with the exception of higher mean partial pressure of carbon dioxide (arterial) 24 hours before bypass in the recent treatment group. For our entire experience, younger age groups had greater survival rates; 100% of infants less than 1 year of age survived.

CONCLUSIONS

Treatment with ECLS is an evolving pulmonary rescue therapy with an 88% survival rate in our recent experience. The survival rate has improved to levels that may not greatly improve in the near future, especially for patients less than 1 year of age. Better patient selection or improved management strategies or both may be responsible for the improved patient outcome.