Treatment of airway obstruction by metallic stents in infants and children.

OBJECTIVE: The internal metallic stent is a relatively new and controversial method for the treatment of airway collapse in infants and children. The study examined the outcomes of this treatment in a large group of patients and defined clear indications for airway stenting. METHODS: A retrospective review was conducted of 32 patients in whom 42 stents were inserted. The patients were divided into three groups with respect to the stented segment: group A, trachea (n = 14); group B, bronchi (n = 16); and group C, trachea and bronchi (n = 2). RESULTS: In 30 cases, there was immediate improvement of respiratory obstruction, and 23 patients could be weaned, at least temporarily, from ventilation. Excessive granulation developed after the stenting in 26 patients. In 6 patients, all in group A, the granulation and inflammatory reaction generated severe airway obstruction, necessitating thoracotomy in 2 cases. One patient died of airway obstruction, and another died during the attempt to remove the stent; both were in group A. Stents placed for 2 to 72 months (mean 8.7 months) have now been removed in 11 patients. Six children are alive and well with stents in place, 2 from group A and 4 from group B. Fifteen patients died during the follow-up period; in 13 cases, death was related to the associated disease. CONCLUSION: The use of metallic stents, especially in the trachea, is associated with a high rate of complications. Granulation tissue, which often develops after stenting, is a major concern. Removal of the stents is arduous and carries a high risk of complications. The use of stents should be restricted to the limited situations in which conventional initial therapy has failed.

Middle cerebral artery flow velocity decreases and electroencephalogram (EEG) changes occur as acute hypercapnia reverses.

OBJECTIVE: To define the changes in middle cerebral artery flow velocity (Vmca) and the electroencephalogram (EEG) during rapid reduction in arterial carbon dioxide (PCO2) from acute hypercapnia. DESIGN. Human volunteer study. SETTING: University-affiliated hospital experimental laboratory. PARTICIPANTS: Nine healthy volunteers aged 25-35 years. INTERVENTIONS: Subjects rebreathed exhaled gas from a bag pre-filled with 5% carbon dioxide (CO2) in oxygen, up to an end-tidal CO2 of 10% or to the limit of discomfort, when they were disconnected. MEASUREMENTS AND RESULTS: Middle cerebral artery blood flow velocity was continuously measured by transcranial Doppler ultrasound, quantitative EEG was recorded and hemodynamics were monitored non-invasively. Vmca closely correlated with end-tidal CO2 changes (r=0.65, p<0.001). When rebreathing ceased, there was a rapid decline in end-tidal CO2 and in Vmca to baseline within 42+/-14 s, followed by a rapid further decline in both variables to below baseline. End-tidal CO2 reached a nadir of 4.4+/-1.1% at 146+/-79 s, with Vmca decreasing to 37+/-10 cm/s at 104+/-65 s (a 40% reduction and 31% below basal values). Electroencephalogram alpha activity significantly decreased and delta activity increased during hypercapnia. During subsequent hypocapnia, delta activity decreased back to baseline, while alpha activity increased, but remained below baseline. CONCLUSIONS: These findings demonstrate the rapid changes occurring in cerebral blood flow during rapid declines in arterial CO2 and the consequent potential for producing brain ischemia and hemodynamic alterations if inadvertent hyperventilation occurs following institution of mechanical ventilation for acute hypercapnia.