Life-threatening status asthmaticus treated with inhaled nitric oxide

Extracorporeal and advanced therapies for progressive refractory near-fatal acute severe asthma in children

Asthma is the most common chronic illness and is one of the most common medical emergencies in children. Progressive refractory near-fatal asthma requiring intubation and mechanical ventilation can lead to death. Extracorporeal membrane oxygenation (ECMO) can provide adequate gas exchange during acute respiratory failure although data on outcomes in children requiring ECMO support for status asthmaticus is sparse with one study reporting survival rates of nearly 85% with asthma being one of the best outcome subsets for patients with refractory respiratory failure requiring ECMO support. We describe the current literature on the use of ECMO and other advanced extracorporeal therapies available for children with acute severe asthma. We also review other advanced invasive and noninvasive therapies in acute severe asthma both before and while on ECMO support.

Current management of status asthmaticus in the pediatric ICU

Status asthmaticus (SA) in the pediatric ICU (PICU) can progress to a life-threatening emergency. The goal of management is to improve hypoxemia, improve bronchoconstriction, and decrease airway edema through the administration of continuous nebulized beta2 adrenergic agonist with intermittent anticholinergics, corticosteroids, and oxygen. Adjunctive therapies, such as magnesium, methylxanthines, intravenous beta-agonists, heliox, and noninvasive ventilation should be considered in the child who fails to respond to initial therapies. The restoration of adequate pulmonary functions, resolution of airway obstruction, and avoidance of mechanical ventilation should guide management. This article reviews the pathophysiology, assessment, and management of the child who has SA in the PICU to provide the critical care nurse with current information to facilitate optimal care.

Exposure of Intensive Care Unit Nurses to Nitric Oxide and Nitrogen Dioxide During Therapeutic Use of Inhaled Nitric Oxide in Adults With Acute Respiratory Distress Syndrome

• Background Although low concentrations of inhaled nitric oxide may by therapeutic, both nitric oxide and its oxidation product nitrogen dioxide are potentially toxic. The threshold limits for time-weighted average concentrations of nitric oxide and nitrogen dioxide issued by the American Conference of Governmental Industrial Hygienists are 25 and 3 ppm, respectively. The concentrations of these gases in the breathing space of hospital personnel during administration of nitric oxide to adult patients have not been reported.

• Methods Air was sampled from the breathing zone of intensive care unit nurses via collar-mounted tubes during the nurses’ routine duties attending patients who were receiving inhaled nitric oxide at 5 or 20 ppm. The exhaust ports of the mechanical ventilators were left open to the room. Nitric oxide and nitrogen dioxide were chemically assayed as nitrite from sorbent tubes by using spectrophotometry. Ambient nitric oxide levels were measured at sequential distances from the ventilator by using chemiluminescence.

• Results The time-weighted average concentrations of inspired gas for nurses during inhaled nitric oxide treatment were 0.45 ppm or less for nitric oxide and less than 0.29 ppm for nitrogen dioxide. Nitric oxide levels at the ventilator during delivery at 20 ppm were 9.2 ppm, but dropped off markedly beyond 0.6 m (2 ft), to a mean of about 30 ppb.

• Conclusion Inhaled nitric oxide therapy at doses up to 20 ppm does not appear to pose a risk of excessive occupational exposure to nitric oxide or nitrogen dioxide to nurses during routine delivery of critical care.

Tratamientos complementarios: óxido nítrico, posición en prono y surfactante

The management of hypoxic respiratory failure is based on oxygen delivery and ventilatory support with lung-protective ventilation strategies. Better understanding of acute lung injury have led to new therapeutic approaches that can modify the outcome of these patients. These adjunctive oxygenation strategies include inhaled nitric oxide and surfactant delivery, and the use of prone positioning. Nitric oxide is a selective pulmonary vasodilator that when inhaled, improves oxygenation in clinical situations such as persistent pulmonary hypertension of the newborn, pulmonary hypertension associated with congenital heart disease, and acute respiratory distress syndrome (ARDS). When applied early in ARDS, prone positioning improves distribution of ventilation and reduces the intrapulmonary shunt. The surfactant has dramatically decreased mortality caused by hyaline membrane disease in premature newborns, although the results have been less successful in ARDS. Greater experience is required to determine whether the combination of these treatments will improve the prognosis of these patients.

Inhaled nitric oxide in ARDS

The role of nitric oxide (NO) in numerous physiologic systems only recently has been discovered. When used as a gas, inhaled NO (iNO) has many unique properties that cause immediate improvements in pulmonary hemodynamics and oxygenation. Acute benefits in physiologic parameters have been demonstrated in numerous studies of iNO in acute respiratory distress syndrome (ARDS), but recent randomized controlled trials have failed to show improvement in outcome. The addition of other treatments that prolong or enhance the affect of iNO or its use with other ventilator modalities such as prone positioning or high-frequency ventilation offer hope that iNO may be beneficial in select groups of patients.

Exhaled nitric oxide decreases during exercise-induced bronchoconstriction in children with asthma

Nitric oxide (NO) produced in the airways can be either detrimental or protective to the host. To investigate the role of NO in the pathogenesis of exercise-induced bronchoconstriction (EIB), we measured exhaled NO (ENO) after exercise challenge in 39 asthmatic and six normal children. FEV(1) and ENO were measured before and at 0, 5, 10, and 15 min after exercise performed on a treadmill for 6 min. EIB was defined as a decrease in FEV(1) of more than 15% after the exercise. Normal children (control group) did not have EIB. Twenty-one patients with asthma had EIB (EIB group) whereas the remaining 18 patients did not (non-EIB group). The baseline ENO value was significantly higher in the asthmatic children than in the normal children, and there was a positive correlation between the maximal percent decrease in FEV(1) and the baseline ENO value (r = 0.501, p = 0.012). At the end of the exercise, ENO had decreased in all the subjects. In the non-EIB and control groups, ENO rebounded to above the baseline at 5 min after the exercise and thereafter. In contrast, ENO remained at a decreased level in the EIB group. The change in ENO did not correlate with the change in minute ventilation, and beta-agonist inhalation at the peak of EIB that accelerated the recovery of FEV(1) did not affect the depressed level of ENO, demonstrating that the reduction of ENO is not a simple consequence of increased ventilation nor airway obstruction. Among the EIB group, steroid-treated patients showed sooner recovery in ENO after the exercise than steroid-naive patients. Our study suggests that NO production in response to exercise may be impaired in patients with EIB, and that ENO represents not only airway inflammation but also a protective function of NO in EIB.