Adult respiratory distress syndrome in children

Partial liquid ventilation for the prevention of mortality and morbidity in paediatric acute lung injury and acute respiratory distress syndrome

BACKGROUND

Acute lung injury and acute respiratory distress syndrome are syndromes of severe respiratory failure. Children with acute lung injury or acute respiratory distress syndrome have high mortality and the survivors have significant morbidity. Partial liquid ventilation is proposed as a less injurious form of respiratory support for these children. Uncontrolled studies in adults have shown improvements in gas exchange and lung compliance with partial liquid ventilation. A single uncontrolled study in six children with acute respiratory syndrome showed some improvement in gas exchange during three hours of partial liquid ventilation. This review was originally published in 2004, updated in 2009 and again in 2012.

OBJECTIVES

To assess whether partial liquid ventilation reduces mortality or morbidity, or both, in children with acute lung injury or acute respiratory distress syndrome.

SEARCH METHODS

In this updated review, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 11); CINAHL (Cumulative Index to Nursing & Allied Health Literature) via Ovid (1982 to November 2011); Ovid MEDLINE (1950 to November 2011); and Ovid EMBASE (1982 to November 2011). The search was last performed in August 2008.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) which compared partial liquid ventilation with other forms of ventilation in children (aged 28 days to 18 years) with acute lung injury or acute respiratory distress syndrome. Trials had to report one or more of the following: mortality; duration of mechanical ventilation, respiratory support, oxygen therapy, stay in the intensive care unit, or stay in hospital; infection; long-term cognitive impairment, neurodevelopmental progress, or other long-term morbidities.

DATA COLLECTION AND ANALYSIS

We independently evaluated the quality of the relevant studies and extracted the data from the included studies.

MAIN RESULTS

Only one study enrolling 182 patients (reported as an abstract in conference proceedings) was identified and found eligible for inclusion; the authors reported only limited results. The trial was stopped prematurely and was, therefore, under-powered to detect any significant differences and at high risk of bias. The only available outcome of clinical significance was 28-day mortality. There was no statistically significant difference between groups, with a relative risk for 28-day mortality in the partial liquid ventilation group of 1.54 (95% confidence interval 0.82 to 2.9).

AUTHORS' CONCLUSIONS

There is no evidence from RCTs to support or refute the use of partial liquid ventilation in children with acute lung injury or acute respiratory distress syndrome. Adequately powered, high quality RCTs are still needed to assess its efficacy. Clinically relevant outcome measures should be assessed (mortality at discharge and later, duration of both respiratory support and hospital stay, and long-term neurodevelopmental outcomes). The studies should be published in full.

Partial liquid ventilation for the prevention of mortality and morbidity in paediatric acute lung injury and acute respiratory distress syndrome

BACKGROUND

Acute lung injury, and acute respiratory distress syndrome, are syndromes of severe respiratory failure. Children with acute lung injury or acute respiratory syndrome have high mortality and significant morbidity. Partial liquid ventilation is proposed as a less injurious form of respiratory support for these children. Uncontrolled studies in adults have shown improvement in gas exchange and lung compliance with partial liquid ventilation A single uncontrolled study in six children with acute respiratory syndrome showed some improvement in gas exchange during three hours of partial liquid ventilation.

OBJECTIVES

To assess whether partial liquid ventilation reduces either mortality or morbidity, or both, in children with acute lung injury or acute respiratory syndrome.

SEARCH STRATEGY

We searched The Cochrane Central Register of Controlled Trials (CENTRAL), The Cochrane Library issue 2, 2003; MEDLINE (1966 to April 2003); and CINAHL (1982 to April 2003); intensive care journals and conference proceedings; reference lists and 'grey literature'.

SELECTION CRITERIA

Randomized controlled trials which compared partial liquid ventilation with other forms of ventilation, in children (28 days - 18 years) with acute lung injury or acute respiratory syndrome, reporting one or more of the following: mortality; duration of mechanical ventilation, respiratory support, oxygen therapy, stay in the intensive care unit, or stay in hospital; infection; or long term cognitive impairment or neurodevelopmental progress or other long term morbidities.

DATA COLLECTION AND ANALYSIS

Two reviewers independently evaluated the quality of the relevant studies and extracted the data from the included studies.

MAIN RESULTS

Only one study enrolling 182 patients (only reported as an abstract in conference proceedings) was identified and found eligible for inclusion: the authors report only limited results. The trial was stopped prematurely and therefore under-powered to detect any significant differences. The only outcome of clinical significance available was 28 day mortality: there was no statistically significant difference between groups with a relative risk for 28 day mortality in the partial liquid ventilation group of 1.54 (95% confidence intervals of 0.82 to 2.9).

REVIEWERS' CONCLUSIONS

There is no evidence from randomized controlled trials to support or refute the use of partial liquid ventilation in children with acute lung injury or acute respiratory syndrome: adequately powered, high quality randomized controlled trials are still needed to assess its efficacy. Clinically relevant outcome measures should be assessed (mortality at discharge and later, duration of respiratory support and hospital stay, and long-term neurodevelopmental outcomes) and the studies should be published in full.

Increased tissue-type plasminogen activator antigen release is not accompanied by increased systemic fibrinolytic activity in severe neonatal respiratory distress syndrome

Intravascular and intraalveolar fibrin depositions in preterm infants with severe respiratory distress syndrome (RDS) have been attributed to activation of clotting. We questioned whether in the face of activated clotting, fibrinolysis is sufficient in these infants. We found, in infants with severe RDS within 6 to 12 h of birth, increased median thrombin-antithrombin III complex formation (11.1 versus 1.3 ng/mL in the group with mild-to-moderate RDS, p < 0.001), indicating activation of clotting. Simultaneously, we found increased tissue-type plasminogen activator antigen (t-PA) release in plasma of these infants represented by increased median t-PA plasma concentrations (8.3 versus 2.5 ng/mL in the group with mild-to-moderate RDS, p < 0.01). This increased t-PA release was not accompanied with more plasminogen and antiplasmin consumption and with more fibrin and fibrinogen degradation than in the infants with mild-to-moderate RDS because plasma plasminogen and antiplasmin activity and total fibrin and fibrinogen degradation product concentrations were similar in both groups. We have found that activated clotting and t-PA plasma concentrations are positively correlated with arterial-to-alveolar oxygen tension ratio and ventilator efficiency index values. Plasminogen and antiplasmin activity, and total fibrin and fibrinogen degradation product concentrations were not correlated with these continuous measures of RDS severity. In neonatal RDS, clotting activity contributes to disease severity. Insufficient fibrinolysis likely facilitates the deleterious effects of activated clotting.

Methylprednisolone attenuates the pulmonary hypertensive response in porcine meconium aspiration

Severe neonatal aspiration of meconium is frequently complicated by fatal pulmonary hypertension. The protective effect of an i.v. bolus of methylprednisolone on meconium aspiration-induced hypertensive lung injury was studied in anesthetized pigs with adapted lung circulation. Eleven 10-wk-old pigs received 3 mL/kg 20% human meconium via the endotracheal tube. Five of them were pretreated with 30 mg/kg methylprednisolone 30 min before aspiration. Ventilator settings were adjusted to keep arterial PO2 above 8 kPa and arterial PCO2 below 5 kPa. Meconium insufflation induced a biphasic pulmonary pressor response during the 6 h follow-up. Methylprednisolone tended to prevent the early (0-1 h) increase in pulmonary artery pressure and inhibited significantly the second phase (1-6 h) progressive rise in pulmonary artery pressure and pulmonary vascular resistance. This inhibition of resistance increase was most profound in the postarterial segment of the lung circulation, as determined by pulmonary artery occlusion. Additionally, the methylprednisolone pretreated group demonstrated a significant decrease in venous admixture together with improved oxygenation during the late phase after the insult, and further showed evidence of diminished lung edema formation. Although meconium aspiration-induced fall in blood leukocyte concentration was inhibited by methylprednisolone pretreatment, no histologic difference was found in pulmonary leukocyte sequestration. Our results thus show that in adapted porcine lungs methylprednisolone pretreatment improves oxygenation and attenuates the meconium aspiration-induced pulmonary hypertensive response by preventing the increase in the postarterial resistance.

Number and activation of circulating polymorphonuclear leukocytes and platelets are associated with neonatal respiratory distress syndrome severity

OBJECTIVE

To determine whether number and activation of circulating polymorphonuclear leukocytes (PMNs) and platelets are associated with disease severity in neonatal respiratory distress syndrome (RDS).

DESIGN

Prospective study.

SETTING

Tertiary neonatal intensive care unit.

PATIENTS

Preterm infants with severe (n = 18) or mild to moderate (n = 18) RDS who were consecutively admitted.

INTERVENTIONS

PMN and platelet counts and plasma concentrations of elastase-alpha1-proteinase inhibitor (E-alpha1-PI) and thromboxane B2 (TxB2) were recorded each day during the first 5 days of life. E-alpha1-PI-to-PMN and TxB2-to-platelet ratios were calculated to correct for the influence of the PMN and platelet count on elastase and thromboxane release.

RESULTS

From day 2, the severe RDS group had lower median PMN counts (1.5 vs 4.5 x 10/L), lower mean platelet counts (136 vs 230 x 10/L), and more elastase and thromboxane release, indicated by higher median E-alpha1-PI-to-PMN (39.2 vs 13.0 ng/10 PMNs on day 2) and TxB2-to-platelet (2.61 vs 0.52 pg/10 platelets on day 3) ratios than the mild-to-moderate group. Lower PMN and platelet counts and higher elastase and thromboxane release were correlated with birth asphyxia (lower 5-minute Apgar scores and umbilical arterial PH values), higher respiratory requirements (fraction of inspired oxygen and peak inspiratory pressure), and decreased values for continuous measures of RDS severity (ventilatory efficiency index and PaO2-to-alveolar oxygen tension ratio).

CONCLUSION

Decreased PMN and platelet counts and increased elastase and thromboxane release are correlated with increased RDS severity. Birth asphyxia (hypoxia and acidosis) and tissue injury caused by high-pressure ventilation and hyperoxia may promote this activation process.

Meconium aspiration induces ARDS-like pulmonary response in lungs of ten-week-old pigs

To investigate whether aspiration of meconium induces a hemodynamic and histologic pulmonary response similar to that frequently seen in experimental acute respiratory distress syndrome, twelve 10-week-old pigs with postnatally adapted lungs were studied. Six 10-week-old pigs received 3 ml/kg 20% human meconium via the endotracheal tube. Six control pigs of the same age were given sterile saline. Ventilator settings were adjusted to keep PaO2 above 8 kPa and PaCO2 below 5 kPa. The pulmonary hemodynamic response to aspiration consisted of two separate hypertensive components. An initial peak in pulmonary artery pressure (PAP) and pulmonary vascular resistance (PVR) was followed by a progressive increase in PAP and PVR in the meconium group, whereas in the saline group these parameters returned to baseline levels. The distribution of PVR, determined by pulmonary artery occlusion, was characterized by an increase in the postarterial resistance immediately after meconium aspiration and a progressive increase in both arterial and postarterial resistance during the later phase. On histological examination, marked neutrophil sequestration was seen in the meconium lungs. In addition, lung edema formation was significantly enhanced in the meconium group, as shown by an increased lung wet/dry weight ratio. Thus, meconium aspiration resulted in a biphasic pulmonary pressor response and severe pulmonary inflammation. This response resembled that of models of experimental acute respiratory distress syndrome following diverse types of precipitating insults; this suggests that similar pathophysiologic mechanisms are elicited and cause similar pulmonary dysfunction following different forms of lung injury.

Disease severity is correlated with plasma clotting and fibrinolytic and kinin-kallikrein activity in neonatal respiratory distress syndrome

This study was undertaken to determine whether simultaneous activation of clotting, fibrinolysis, and kinin-kallikrein is associated with disease severity in preterm infants with neonatal respiratory distress syndrome (RDS), during the first 5 d of life. In the infants with severe RDS, we found activation of clotting, fibrinolysis, and kinin-kallikrein within 6-12 h of birth, indicated by increased thrombin-antithrombin III complex formation [22.5 ng/ml versus 1.4 ng/ml (median values) in the mild/moderate RDS infants, p < 0.001], increased tissue-type plasminogen activator plasma concentrations [5.1 ng/ml versus 2.6 ng/ml (median values) in the mild/moderate RDS infants, p < 0.01], and increased plasma kallikrein activity [198% versus 189% of maximal activated human plasma (median values) in the mild/ moderate infants, p < 0.01], respectively. Thrombin generation, tissue-type plasminogen activator release, and kallikrein activity did not change significantly in the severe RDS group throughout the study. In these infants, kallikrein activity was accompanied by lower values of plasma kallikrein inhibitory activity. Activation of clotting, fibrinolysis, and kinin-kallikrein was accompanied with a transient decrease of the neutrophil count and a steady decrease of the platelet count in the severe RDS group. The studied parameters of clotting and fibrinolytic and kinin-kallikrein activation were significantly correlated with continuous measures of RDS severity. We, therefore, suggest that this activation process likely contributes to respiratory insufficiency in neonatal RDS.

Advances in conventional and innovative therapies for respiratory distress syndrome in children

Adult respiratory distress syndrome is a phenomenon encountered by many pediatric critical care nurses. Care of these complex patients is multifaceted and requires an in-depth understanding of pathophysiology and therapeutic intervention. Several innovative treatments are now available as biomedical and technical advances have evolved. Outcomes will improve as clinicians improve patient selection, identify therapeutic endpoints, and risk/benefits. This article addresses the current understanding of pathophysiology, innovative treatments, and nursing care issues.

Selective inhibition of the inducible isoform of nitric oxide synthase prevents pulmonary transvascular flux during acute endotoxemia

The inducible isoform of nitric oxide synthase (iNOS) is expressed in various organs, including the lung, during systemic endotoxemia. Overproduction of nitric oxide (NO) by iNOS contributes significantly to the vascular failure and end-organ damage in endotoxemia. Using selective pharmacological inhibitors of iNOS, the purpose of this study was to define the role of iNOS in a rat model of endotoxin-induced pulmonary transvascular flux (TVF). Lung TVF was assessed by a method of Evans Blue permeability index (PI). Bacterial lipopolysaccharide (LPS) (15 mg/kg intraperitoneally [IP]) significantly increased pulmonary iNOS activity and serum levels of nitrite/nitrate (NO2/NO3). This was accompanied by a significant elevation of the PI 5 hours after injection. Selective iNOS inhibition with either S-methyl isothiourea (SMT; 5 mg/kg IP) or aminoguanidine (AG; 20 mg/kg IP), administered 2 hours after LPS injection, significantly prevented the increase in PI associated with LPS injection. Similarly, inhibition of the induction of iNOS with dexamethasone (10 mg/kg IP), given 3 hours before LPS, also inhibited the increase in PI. All three treatments significantly prevented the increase in both lung iNOS activity and serum NO2/NO3 associated with endotoxemia. In conclusion, the overproduction of NO generated by iNOS during systemic endotoxemia causes a vascular leak in the lung. Thus, it is speculated that selective inhibition of iNOS may be beneficial in preventing the development of acute respiratory failure in sepsis.

Leakage of protein into lungs of preterm ventilated rabbits is correlated with activation of clotting, complement, and polymorphonuclear leukocytes in plasma

We investigated whether leakage of protein in lungs of preterm ventilated rabbits of 28- and 29-d gestational age is correlated with activation of clotting, complement, and polymorphonuclear leukocytes (PMN) in plasma. We found signs of systemic activation of clotting, complement and PMN in ventilated 28-d gestational age rabbits, as indicated, respectively, by increased median plasma fibrin monomer concentrations (83 versus 40% of normal adult rabbit plasma in nonventilated 28-d gestational age rabbits, p < 0.01), decreased median plasma CH50 activity (112 versus 122 U/L in nonventilated 28-d gestational age rabbits, p < 0.05), and increased median plasma beta-glucuronidase concentrations (159 versus 97% of maximal activated adult rabbit plasma in nonventilated 28-d gestational age rabbits p < 0.05). We did not find signs of systemic activation in the ventilated 29-d gestational age group. Higher median total protein concentrations in alveolar wash of the ventilated 28-d gestational age rabbits (2.7 versus 1.3 mg/mL in the nonventilated rabbits. p < 0.01) indicated protein leakage into the lungs, and this protein leakage was more pronounced in the lungs of ventilated 28-d gestational age rabbits than in those of ventilated 29-d gestational age rabbits (2.1 mg/mL, p < 0.01). The total protein concentration in the alveolar wash of all 28-d gestational age rabbits was correlated with the concentration of fibrin monomers (p = 0.51, p = 0.035) and beta-glucuronidase (p = 0.61, p = 0.011), and the CH50 activity (p = -0.73, p = 0.002) in plasma. We conclude that leakage of protein in lungs of preterm ventilated rabbits of 28-d gestational age is correlated with activation of clotting, complement, and PMN in plasma. This activation process may contribute to lung injury by intravascular and intraalveolar deposition of fibrin and formation of proteinaceous edema.

Factors affecting the neonatal response to artificial surfactant

OBJECTIVE

To define the individual neonatal response to the artificial surfactant, Exosurf, and factors that may influence the response.

METHODOLOGY

Eighty-two consecutive, preterm neonates with respiratory distress syndrome, who received Exosurf at < 12 h of age were studied. Their response was categorized from the graphical change in the oxygenation index with postnatal age, for 12 h after each of two doses of surfactant and assessed independently by two observers. Clinical factors were analysed for their effect on the four pre-defined categories of response, namely: none; mild; good: relapsed; and good: sustained.

RESULTS

Within the first 12 h, 11% of the neonatas showed no response, 5% a mild response and 84% a good response, but 34% relapsed. By 24 h, 6% still showed no response (all died), 11% showed a mild response and 83% a good response, of whom half relapsed. At 24 h, no response was significantly associated with low gestational age and asphyxia, mild response with less severe lung disease. According to the response there was a gradation in the risk of death during the first week.

CONCLUSIONS

The response to Exosurf can be individually and reproducibly categorized and demonstrated that 83% of neonates had a good response but half relapsed. No response was associated with extreme prematurity and asphyxia.

Activation of circulating polymorphonuclear leukocytes in preterm infants with severe idiopathic respiratory distress syndrome

We have studied activation of circulating polymorphonuclear leukocytes (PMN) in plasma of preterm infants with severe idiopathic respiratory distress syndrome (IRDS group, n = 15) and without IRDS (reference group, n = 15) during the first 5 postnatal days. We have observed lower median PMN counts in the IRDS group than in the reference group from d 2 (1.4 x 10(9)/L versus 4.8 x 10(9)/L in the reference group, p < 0.001) to d 4 to 6 (1.6 x 10(9)/L versus 4.0 x 10(9)/L, p < 0.01). Lower PMN counts in the IRDS infants were accompanied by lower median plasma elastase-alpha1-proteinase inhibitor (PI) concentrations (53.6 ng/mL versus 128.0 ng/mL in the reference group on d 2, p < 0.05). Simultaneously, median elastase-alpha1-PI/PMN ratios of these infants were significantly higher (40.8 ng/10(6) PMN versus 21.8 ng/10(6) PMN on d 2, p < 0.05), indicating activation of circulating PMN. Activation of circulating PMN in the IRDS group is associated with platelet-activating factor (PAF) release and complement activation from within 6 to 12 h of birth but not with release of tumor necrosis factor-alpha. PAF release was represented by significantly reduced inhibiting capacity (58% of normal human plasma, p < 0.01) and complement activation by higher median plasma C3a des-Arg concentrations (1680 ng/mL versus 325 ng/mL in the reference group, p < 0.001). We conclude that circulating PMN are activated in preterm infants with severe IRDS, which might be caused by systemic PAF release and complement activation. This activation process may play a role in the pathogenesis of the IRDS by influx of activated PMN into the lungs.

Critical care of the pediatric oncology patient

The survival rate of children with neoplastic disease has increased significantly because of advances in the diagnosis and treatment of malignancy. The consequences of these scientific advances have led to increased malignancy-related critical complications requiring the expertise of intensive care practitioners. In this article, the authors review common complication associated with malignancies that require admission to the pediatric intensive care unit. Disorders are grouped according to the pathophysiologic mechanism: mechanical effects, systemic effects, related to brain tumors, and complications of intensive chemotherapy or chemo-radiotherapy regimens. Superior vena cava syndrome and brain tumors are described in detail. In conclusion, there is a discussion of outcome data for children with neoplastic disease who are admitted to the pediatric intensive care unit and the role of the advanced practice nurse in influencing patient and family perceptions of the experience.