Dexmedetomidine for infant pulmonary function testing.

For the last thirty years, oral chloral hydrate has been used for sedation of infants for lung function testing. Recently, however, availability of chloral hydrate became severely limited in the United States after two manufacturers discontinued manufacturing in 2012. Due to these limitations and the recent and ongoing shortage of chloral hydrate, other medications have been proposed for lung function testing, including midazolam and propofol. Herein, we describe our limited experience using intravenous dexmedetomedine (DMED), a medication thus far described as having minimal effect on pulmonary function or respiratory drive.

Pulmonary and Radiographic Outcomes of VEPTR (Vertical Expandable Prosthetic Titanium Rib) Treatment in Early-Onset Scoliosis.

BACKGROUND: VEPTR (vertical expandable prosthetic titanium rib) expansion thoracoplasty is used to manage thoracic insufficiency syndrome in early-onset scoliosis. Literature regarding the effects of this technique on pulmonary function is scarce. The aim of this study was to report the intermediate-term results of VEPTR expansion thoracoplasty. METHODS: Twenty-one children with thoracic insufficiency syndrome underwent VEPTR expansion thoracoplasty from 2002 to 2012 and had complete chart data, preoperative and follow-up radiographs, and pulmonary function tests performed at the index implantation, first expansion, and last expansion. Pulmonary function tests with forced and passive deflation techniques developed for children under general anesthesia were performed prior to the index implantation and each expansion surgery under the same anesthetic conditions. Pulmonary and radiographic parameters were analyzed longitudinally. RESULTS: Mean follow-up was six years, and mean age at implantation was 4.8 years. The mean number of expansion procedures per patient was eleven, and the mean number of pulmonary function tests was ten. The mean interval between surgical procedures was 6.4 months. Mean forced vital capacity (FVC) increased from 0.65 to 0.96 L (p < 0.0001). However, the percentage of the predicted FVC decreased from 77% to 58%. Respiratory system compliance normalized on the basis of body weight, Crs/kg, decreased by 39%, from 1.4 to 0.86 mL/cm H2O/kg. The mean Cobb angle before treatment was 80°, and the mean maximum thoracic kyphosis angle was 57° (range, 7° to 107°). The initial coronal correction was maintained at the time of final follow-up (67°); however, there was a trend toward a decrease in the maximum thoracic kyphosis angle (to 66°, p = 0.08). Clinically apparent proximal thoracic kyphosis occurred in four patients, and spinal imbalance occurred in seven. The mean gain in T1-T12 height during the treatment period was 18 mm (2.9 mm/year). CONCLUSIONS: FVC improved over time; however, this increase in lung volume did not keep up with the growth of the child, as the percentage of the predicted FVC decreased, and the chest wall stiffness increased. Coronal correction was maintained, but the increase in proximal thoracic kyphosis is concerning. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

The effect of cisatracurium and rocuronium on lung function in anesthetized children.

BACKGROUND: Neuromuscular blocking drugs have been implicated in intraoperative bronchoconstrictive episodes. We examined the effects of clinically relevant doses of cisatracurium and rocuronium on the lung mechanics of pediatric subjects. We hypothesized that cisatracurium and rocuronium would have bronchoconstrictive effects. METHODS: We studied ASA physical status I and II pediatric subjects having elective dental or urological procedures, requiring general anesthesia with endotracheal intubations with either cisatracurium or rocuronium. Pulmonary function tests were performed before and after neuromuscular blocking drug dosing and again after albuterol administration. Using forced deflation and passive deflation techniques, forced vital capacity (FVC) and maximum expiratory flow rate at 10% (MEF10) of FVC were obtained. Fractional changes from the baseline were used to compare subjects. Changes in MEF10 of >30% were considered clinically significant. A Shapiro-Wilk test, paired t test, and Wilcoxon rank sum test were used to analyze the data. RESULTS: Twenty-five subjects (median age = 5.25 years; range = 9 months-9.9 years) were studied; 12 subjects received cisatracurium and 13 subjects received rocuronium. Data are shown as mean proportional change ± SD or, in the case of not normally distributed, median proportional change (first, third quartile) with P values. In the cisatracurium group, there were no differences between baseline and postneuromuscular blocker administration in the fractional change from the baselines of FVC (1.00 ± 0.04, P = 0.5), but there was a significant decrease in MEF10 (0.80 ± 0.18, P = 0.002). In the rocuronium group, there were small yet significant decreases of FVC (0.99 [first quartile 0.97, third quartile 1], P = 0.02) and significant decreases in MEF10 (0.78 ± 0.26, P = 0.008). After administration of albuterol in the cisatracurium group, FVC increased slightly but significantly from baseline values (1.02 ± 0.02, P = 0.005). MEF10 increased significantly beyond baseline values (1.24 ± 0.43, P =0.04). In the rocuronium group, there were also significant differences between baseline and postalbuterol administration from the baseline value of FVC (1.02 ± 0.02, P = 0.004) and MEF10 (1.23 ± 0.29, P = 0.01). CONCLUSIONS: At clinically relevant doses, both cisatracurium and rocuronium caused changes in lung function, indicating constriction of smaller airways. In general, these changes were mild and not clinically detectable. However, in the rocuronium group, 3 of 13 patients showed more noticeable decreases in MEF10 (≤50%), demonstrating the potential for significant broncho-bronchiolar constriction in susceptible patients.

Thoracic malformation with early-onset scoliosis: effect of serial VEPTR expansion thoracoplasty on lung growth and function in children.

The effect on pulmonary function of serial VEPTR expansion thoracoplasty was studied longitudinally in anesthetized children with spondylothoracic dysplasia using a special mobile unit. The median age of 24 children at the start of surgery was 4.6 years (1.8-10.8) and most exhibited a moderate-to-severe restrictive lung defect. After a median of 3.2 years (1.0-6.5), their forced vital capacity (FVC) was found to have increased by an average of 11.1%/year. The rate of increase was greater in children who were younger than 6 years at the start of the study than in older children (14.5% versus 6.5%, p<0.01). The average specific respiratory system compliance (C(rs)) was mildly-to-moderately decreased at the start, and over the study it decreased on average to 56% of the initial value in spite of clinically successful expansion thoracoplasty and lung growth, indicating increasing stiffness of the thorax with growth.

The effect of lung expansion and positive end-expiratory pressure on respiratory mechanics in anesthetized children.

BACKGROUND: Imaging studies have shown that general anesthesia in children results in atelectasis. Lung recruitment total lung capacity (TLC) maneuvers plus positive end-expiratory pressure (PEEP) are effective in preventing atelectasis. However, physiological changes in children during general anesthesia have not been elucidated. METHODS: In eight anesthetized and mechanically ventilated children (median age: 3.5 years; range: 2.3-6.5), we measured static respiratory system elastance (E(st)), flow resistance (R(int)), and elastance and resistance components resulting from tissue viscoelasticity (deltaE and deltaR, respectively) using the constant inflow, end-inspiratory occlusion method preceded by TLC maneuvers, both with zero PEEP (ZEEP) and PEEP (5 cm H2O) for comparison. RESULTS: With constant inspiratory flow V(I) and ZEEP, increases in end-inspiratory lung volume above relaxation volume (tidal volume, V(T)) from 8 to 20 mL x kg(-1) resulted in decreases in E(st) from 1.06 to 0.82 cm H2O x mL(-1) x kg, deltaE from 0.16 to 0.09, and R(int) from 0.13 to 0.11 cm H2O x mL(-1) x s x kg, whereas deltaR increased from 0.08 to 0.12 (P < 0.05). Similar relationships were found with PEEP. Increases in V(I) (8 to 26 mL x s(-1) x kg) with constant V(T) and ZEEP resulted in decreases in E(st) from 1.09 to 0.9 and deltaR from 0.17 to 0.06 (P < 0.01), whereas deltaE and R(int) did not change. There was a similar flow and volume dependence of elastance and resistance with PEEP. CONCLUSIONS: The observed steady decreases in E(st) with increasing V(T) (up to 16 mL/kg with PEEP) indicate marked reductions in end-expiratory relaxation volume (functional residual capacity) even with PEEP. Similarity in results with ZEEP and PEEP suggests that TLC-maneuvers and O2-N2 ventilation prevented airway closure throughout the study.

American College of Chest Physicians consensus statement on the respiratory and related management of patients with Duchenne muscular dystrophy undergoing anesthesia or sedation.

This statement on the management of patients with Duchenne muscular dystrophy (DMD) undergoing procedural sedation or general anesthesia represents the consensus opinion of a multidisciplinary panel convened under the auspices of the American College of Chest Physicians. Expert recommendations on this subject are needed for several reasons. First, patients with DMD have an increased risk of complications when they undergo sedation or general anesthesia. In addition, due to improved cardiopulmonary therapies, patients with DMD are experiencing an unprecedented duration of survival. As a result, it is more common for them to require procedures involving sedation or general anesthesia. The risks related to anesthesia and sedation for DMD patients include potentially fatal reactions to inhaled anesthetics and certain muscle relaxants, upper airway obstruction, hypoventilation, atelectasis, congestive heart failure, cardiac dysrhythmias, respiratory failure, and difficulty weaning from mechanical ventilation. This statement includes advice regarding the highly interrelated areas of respiratory, cardiac, GI, and anesthetic management of patients with DMD undergoing general anesthesia or procedural sedation. The statement is intended to aid clinicians involved in the care of patients with DMD and to be a resource for other stakeholders in this field, including patients and their families. It is an up-to-date summary of medical literature regarding this topic and identifies areas in need of future research.

Effects on lung function of multiple expansion thoracoplasty in children with thoracic insufficiency syndrome: a longitudinal study.

STUDY DESIGN: Longitudinal study of intraoperative pulmonary function in young children with thoracic hypoplasia and scoliosis undergoing multiple expansion thoracoplasty using the vertical expandable prosthetic titanium ribs (VEPTRs). OBJECTIVE: To test the long-term efficacy of VEPTR multiple expansion thoracoplasty. SUMMARY OF BACKGROUND DATA: To our knowledge, no direct measurements of pulmonary function have been reported with VEPTR expansion thoracoplasty. METHODS: There were 10 children with thoracic insufficiency syndrome, secondary to thoracic hypoplasia with progressive scoliosis, studied. A mobile pulmonary function laboratory unit was used to study forced vital capacity (FVC), maximum expiratory flow volume curves, and respiratory system compliance (Crs) with the patient under general anesthesia immediately before and after expansion thoracoplasty. Studies were repeated every 6 months at each subsequent operation for expansion thoracoplasty for the duration up to 33 months. RESULTS: At the baseline studies, FVC showed a moderate-to-severe decrease (69% of predicted values), indicating the presence of significant restrictive lung defect. Only 1 of 10 children had severe airway obstruction. The baseline Crs was markedly decreased in part because of the presence of significant atelectasis. Crs increased with an average of 42% after repeated hyperinflation (deep sighs). There was no change in lung volume or function immediately before versus after completion of expansion thoracoplasty. FVC increased significantly over time, with an average rate of 26.8% per year, the rate of increase similar to that of healthy children of comparative ages. In terms of percent-predicted values, FVC did not change significantly between the baseline and last test, indicating that in most children studied, lung growth kept up with body growth. CONCLUSION: Although it is difficult to assess the extent of the efficacy without a proper or historical control group for comparison, the present study indicates that in children with severe thoracic insufficiency syndrome, the insertion of VEPTRs with multiple expansion thoracoplasties is beneficial over time, by allowing the lungs to expand with body growth without further deterioration in lung function.

The effect on lung mechanics in anesthetized children with rapacuronium: a comparative study with mivacurium.

UNLABELLED: The administration of rapacuronium increases the risk of severe bronchospasm. There have been no studies of pulmonary function directly demonstrating airway constriction with rapacuronium in children. In this study, 10 ASA physical status I or II patients (aged 2-6 yr) were randomly divided into 2 equal groups, receiving either rapacuronium or mivacurium. Anesthesia was induced with sevoflurane and maintained with remifentanil (0.2-0.3 microg. kg(-1). min(-1)) and propofol (200-250 microg. kg(-1). min(-1)) infusions. We performed three sets of pulmonary function tests: baseline, after the administration of muscle relaxant, and after the administration of a beta(2) agonist. In both groups, there were no changes in static respiratory compliance. The increase in total respiratory system resistance after the administration of rapacuronium did not reach statistical significance (214.4% +/- 122.65% of baseline, P approximately 0.1), whereas maximal expiratory flow at 10% of forced vital capacity (MEF)(10) and MEF(functional residual capacity) on partial flow-volume curves by the forced deflation technique decreased markedly (53.4% +/- 18.49%, P < 0.01 and 41.3% +/- 27.42%, P < 0.001, respectively). With the administration of mivacurium, no changes were observed in respiratory system resistance (109.5% +/- 30.28%). MEF(10) decreased slightly (77.0% +/- 9.03%, P < 0.005) whereas MEF(FRC) did not (81.2% +/- 29.85%, not significant). After the administration of a beta(2) agonist, all measurements returned to baseline. Thus, the administration of rapacuronium consistently results in lower airway obstruction with minimal changes in static respiratory compliance when compared with mivacurium. IMPLICATIONS: Pulmonary function tests in the present study showed that rapacuronium consistently causes severe bronchoconstriction, confirming clinical case reports of bronchospasm. The bronchoconstriction is reversible with albuterol. Mivacurium also causes very mild subclinical bronchoconstriction.