Treatment of Severe Non-Neonatal ARDS in Children with Surfactant and Nitric Oxide in a “PRE-ECMO”-Situation

The use of exogenous surfactant and nitric oxide in neonates has reduced the number of infants requiring ECMO. The purpose of this study was to demonstrate whether these two therapeutic options might reduce the number of over 28 days old children with severe ARDS requiring ECMO, without reducing changes of survival and morbidity. Over a 30 month period all non-neonatal ARDS patients transferred to our institution for ECMO evaluation were treated based on a study-algorithm. If they did not fulfill “fast entry criteria” (paO2< 40 for more than 3 hrs.) we first tried different ventilation, vasodilatation, and hemodynamic strategies for max. 4 hrs. (inv. I/E ratio, HFOV, epoprostenol, high doses norepinephrine. If the 01 did not decrease by< 10, 30-280 mg natural surfactant or 1-20 ppm nitric oxide were treatment options depending on the degree of pulmonary hypertension measured by echocardiography and by mixed venous saturation measurements. It was possible to use NO and surfactant sequentially. The patients had different etiologies of ARDS as near drowning, pneumonia, immunosuppression, and sepsis. If their 01 did not decrease by 10 in 8 hrs. ECMO was installed. Nineteen patients were evaluated, 6 improved with conventional therapy, their 01 decreased without a relapse (mean 01 at begin of the study: 38). Six patients improved with surfactant therapy alone (mean 01: 54), 4 patients improved after surfactant and sequential NO-treatment, 3 patients were initially treated with NO, 1 sequentially with surfactant. One patient did not show any benefit from NO or surfactant and was put on ECMO. Three patients died (withdrawal of life support because of severe brain damage caused by the underlying disease). We could not observe any respiratory related failure. No patient had to be discharged on oxygen. A sophisticated treatment algorithm integrating different modern ARDS treatment options can reduce the number of patients requiring ECMO. We speculate however that these options can only be used effectively in centers involved in ARDS treatment quite frequently and that these centers have to provide ECMO as one of their therapeutic tools.

Acute Respiratory Failure in Pregnancy

Acute respiratory failure in pregnancy has multiple etiologies, including thromboembolism, amniotic fluid embolism, venous air embolism, aspiration of gastric contents, respiratory infections, asthma, beta-adrenergic tocolytic therapy, and pneumomediastinum and pneu mothorax. Proper management of acute respiratory fail ure in pregnancy requires an understanding of the specific diseases and the normal gestational changes that occur in maternal respiration (decreased functional re sidual capacity, increased minute ventilation, mild respi ratory alkalosis) and hemodynamics (increased cardiac output, increased blood and plasma volume, unchanged central pressures). Knowledge of the determinants of oxygen delivery to fetal tissue (uterine blood flow, pla cental transfer, fetal circulation) and how they are af fected by changes in maternal hemodynamics, position, acid-base status, and medications can help sustain nor mal fetal development, whenever possible, without compromising maternal care. Diagnostic testing such as radiography, hemodynamic monitoring, and fetal moni toring are considered in terms of attendant risk to the mother or the fetus, alterations in normal values related to gestation, and indications for usage. Similarly, the risks and benefits of supportive and specific therapies for the various etiologies of acute respiratory therapy are reviewed.

Thoracic compartment syndrome: a case report

Thoracic compartment syndrome has been observed after trauma and after mediastinal and cardiac procedures; however, an adult respiratory distress syndrome (ARDS)-like presentation has not been described as a part of thoracic compartment syndrome. We describe the case of an obese patient who underwent coronary artery bypass (his third such procedure) and hiatal hernia reduction during the same operation, followed by transmyocardial laser revascularization and full chest closure the next day. The patient was hypoxic after chest closure. Two days later, his peak airway pressure increased, and his cardiac and urine outputs decreased. Chest radiography findings suggested ARDS without hemodynamic instability. After we reopened the sternal incisions, the patient's symptoms reversed. Although our patient initially appeared to have ARDS, we believe the organ-volume displacement that occurred during the lengthy dual operation produced a thoracic and abdominal compartment syndrome that responded to decompression of the chest.

Treatment of ARDS

Improved understanding of the pathogenesis of acute lung injury (ALI)/ARDS has led to important advances in the treatment of ALI/ARDS, particularly in the area of ventilator-associated lung injury. Standard supportive care for ALI/ARDS should now include a protective ventilatory strategy with low tidal volume ventilation by the protocol developed by the National Institutes of Health ARDS Network. Further refinements of the protocol for mechanical ventilation will occur as current and future clinical trials are completed. In addition, novel modes of mechanical ventilation are being studied and may augment standard therapy in the future. Although results of anti-inflammatory strategies have been disappointing in clinical trials, further trials are underway to test the efficacy of late corticosteroids and other approaches to modulation of inflammation in ALI/ARDS.

Exacerbation of acute pulmonary edema during assisted mechanical ventilation using a low-tidal volume, lung-protective ventilator strategy

STUDY OBJECTIVES

To assess the magnitude of negative intrathoracic pressure development in a patient whose pulmonary edema acutely worsened immediately following the institution of a low-tidal volume (VT) strategy.

DESIGN

Mechanical lung modeling of patient-ventilator interactions based on data from a case report.

SETTING

Medical ICU and laboratory.

PATIENT

A patient with suspected ARDS and frank pulmonary edema.

INTERVENTIONS

The patient's pulmonary mechanics and spontaneous breathing pattern were measured. Samples of arterial blood and pulmonary edema fluid were obtained.

MEASUREMENTS

A standard work-of-breathing lung model was used to mimic the ventilator settings, pulmonary mechanics, and spontaneous breathing pattern observed when pulmonary edema worsened. Comparison of the pulmonary edema fluid-to-plasma total protein concentration ratio was made.

RESULTS

The patient's spontaneous VT demand was greater than preset. The lung model revealed simulated intrathoracic pressure changes consistent with levels believed necessary to produce pulmonary edema during obstructed breathing. A high degree of imposed circuit-resistive work was found. The pulmonary edema fluid-to-plasma total protein concentration ratio was 0.47, which suggested a hydrostatic mechanism.

CONCLUSION

Ventilator adjustments that greatly increase negative intrathoracic pressure during the acute phase of ARDS may worsen pulmonary edema by increasing the transvascular pressure gradient. Therefore, whenever sedation cannot adequately suppress spontaneous breathing (and muscle relaxants are contraindicated), a low-VT strategy should be modified by using a pressure-regulated mode of ventilation, so that imposed circuit-resistive work does not contribute to the deterioration of the patient's hemodynamic and respiratory status.

Adult respiratory distress in pregnancy: critical care issues

Adult respiratory distress syndrome (ARDS) is a complex disease process involving noncardiogenic pulmonary edema, central hypovolemia, widespread atelectasis, and, in the final stages, an inability to perfuse end organs. Uteroplacental perfusion is usually compromised in such situations, which may be catastrophic, depending on the amount of fetal oxygen reserve. ARDS is often preceded by sepsis and frequently ends in maternal death, despite aggressive intervention. Inflammatory responses, complement activation, and prostaglandins have been implicated as probable mediators of both sepsis and ARDS. Invasive hemodynamic monitoring and mechanical ventilation are usually warranted to provide detailed assessment and support. However, when a critical illness affects the family unit, emotional and spiritual issues must receive significant attention to provide holistic care.