Risk Factors Leading to Failed Procedural Sedation in Children Outside the Operating Room

Objectives: Deep sedation enables effective performance of imaging or procedures in children, but failed sedation still occurs. We desired to determine the factors that were associated with failed sedation in children receiving deep sedation by a dedicated nonanesthesia sedation service and hypothesized that the presence of an upper respiratory infection (URI) and/ or other risk factors would increase the probability of failing sedation. Results: Seven of the 13 predictors were significantly associated with failed sedation; these are as follows: (1) URI (P = 0.008); (2) congenital heart disease (P = 0.021); (3) obstructive sleep apnea (OSA)/snoring (P G 0.001); (4) the American Society of Anesthesiologists (ASA) class of above II (P G 0.001); (5) obesity (P G 0.001); (6) increased weight (P G 0.001); and (7) older age (P G 0.001). Sex, prematurity, asthma, gastroesophageal reflux, and cerebral palsy/developmental delay were not associated with failure. Pulmonary hypertension was not able to be assessed because only 1 patient with pulmonary hypertension was sedated. A forward stepwise regression identified 5 variables that could be considered useful predictors of failed sedation, which are as follows: Key Words: procedural sedation, upper respiratory tract infection, obstructive sleep apnea, snoring, failed sedation, risk factors, obesity (Pediatr Emer Care 2014;30: 381Y387) T he use of procedural sedation and sedation services has become the standard of care to enable effective completion of many pediatric imaging studies and procedures. Through the use of anesthetics such as propofol, the inability to complete a study due to adverse respiratory events or other complications of sedation, defined as a failed sedation, is uncommon. 1 Specifically, a failed sedation results in wasted time for parents, patients, and the sedation service, potential exposure of patients to adverse events, and increased costs. Improved prediction of patients who are likely to fail sedation could potentially increase the safety and efficiency of pediatric procedural sedation provided outside the operating room. A paucity of data exists on risk factors associated with failed pediatric procedural sedation, and little in the literature addresses the role of a recent or current upper respiratory infection (URI) that plays in a failed sedation. Most of the studies report on risk factors associated with respiratory complications of children undergoing general anesthesia in an operating room. 2Y7 These studies have shown conflicting results with regard to whether a URI is associated with adverse respiratory events such as laryngospasm, bronchospasm, oxygen desaturation, and upper airway obstruction. Most studies, however, conclude that a URI, use of an endotracheal tube, a history of snoring, and passive smoking contribute to respiratory complications during general anesthesia. A single study included pediatric procedural sedation data. However, it is not comparable with the typical outpatient sedation population because of the differences in anesthetic use. METHODS Study Population We conducted a retrospective chart review, approved by the institutional review board, of patients requiring sedation for magnetic resonance imaging (MRI), computed tomographic (CT), nuclear medicine scans, and brief procedures (including auditory brainstem response [ABR] tests, lumbar punctures, peripherally inserted central catheter [PICC] line placements, and renal biopsies) at Children's Healthcare of Atlanta at Egleston and at a freestanding radiology facility managed by Children's at Eggleston. Children's Healthcare of Atlanta at Egleston is a quaternary care, free-standing children's hospital in Atlanta, Ga, that provides inpatient and outpatient procedural sedation to approximately 3500 pediatric patients per year. Sedation services are provided by sedation physicians trained in pediatric intensive care, pediatric emergency medicine, or anesthesiology. Almost all patients in the service receive intravenous propofol by bolus dose for induction and maintenance with propofol infusion for the duration of the imaging study or procedure. Sedation service records were reviewed from January 2007 to December 2011 to identify all patients who received sedation. If the imaging or procedure was not completed because of adverse events or complications, this was defined as a failed sedation. For comparison, a convenience sample of all patients successfully receiving sedation during January to February 2009 was obtained. Successful sedation was defined as completion of imaging or procedure in a sedated patient without requirement for rescheduling or general anesthesia. This large sample was identified to allow statistically relevant comparison with the total failed sedation group. The period during winter months was also selected to increase the likelihood of patients with URIs or respiratory symptoms within the group of successful sedations. Patients were included in this study from the ages of birth to 21 years. Characteristics of patients compiled included age, sex, weight, American Society of Anesthesiologists (ASA) class, and history of prematurity. Presence of asthma, current URI, gastroesophageal reflux (GER), cerebral palsy/developmental delay (CP/DD), obstructive sleep apnea (OSA)/snoring, congenital heart disease, or pulmonary hypertension (PHTN) were obtained from a standardized presedation history and physical evaluation form. Heights were not obtained on any of the patients and thus did not allow for the calculation of a body mass index as an objective measure of obesity. Obesity was defined as a weight greater than the 95th percentile for sex and age based on the Centers for Disease Control and Prevention growth curves. 9 Procedure start and end times, type of procedure or imaging study, medications administered, complications experienced, and interventions performed during sedation were all obtained from a standard anesthesia record that was scanned into an electronic medical record. Patients who had an ASA class IV status were excluded from review because of the severity of illness. The complications listed in Sample Size and Power We conservatively estimated that 0.6% of all sedations are unable to be completed. Given approximately 3500 sedations per year, during the period of 4 years, we estimated that approximately 84 failed sedations could be identified from our retrospective chart review. In addition, we estimated that approximately 25% of children undergoing sedation have symptoms of a URI. Power was calculated using a 2-sided z test with pooled variance and significance level of 0.05. In addition, the test assumes that the proportion of cases with URI is 0.25 under the null hypothesis and 0.40 under the alternative hypothesis. Based on the previously mentioned assumptions, group sample sizes of 84 cases and 528 controls achieve 80% power to detect an odds ratio (OR) of 2.0. Sedation Protocol The Children's Sedation Service follows protocols and procedures in accordance with the American Academy of Pediatrics Guidelines for Sedation. 10Y12 The final choice of sedation medication for each patient is at the discretion of the sedation service physician; however, most physicians used propofol. The sedation protocols and practice patterns of physicians in the Children's Sedation Service at Egleston have been published. 10 For MRIs, end-tidal carbon dioxide monitoring using a nasal prong apparatus was routinely used, but these values and trends were not tracked in this study. If sedation was inadequate, additional propofol boluses were given to achieve the desired level of sedation and the maintenance infusion dosage was increased at the discretion of the sedation physician. Once the procedure was completed, the infusion was discontinued, and the patients were monitored until complete recovery criteria were met using the Aldrete score. 14 Statistical Analysis Patients with an ASA class I and II physical status were grouped together for the purposes of data analysis. The goal of analysis was to determine patient characteristics and comorbidities associated with increased odds of failed sedation. To accomplish this, univariate analysis of each potential risk factor was performed to determine if there was an association between the covariate and the outcome failed sedation. This was accomplished by performing W 2 tests of association for categorical variables and 2-sample t tests for continuous variables. Based on the results from the univariate analysis, a set of potential predictors was identified that were significantly associated with failed sedation and could be further analyzed for possible interactions with one another using multivariate logistic regression models. A forward-stepwise logistic regression technique was used to determine a subset of variables that were associated with increased odds of failed sedation. A significance level of 0.2 was required to allow the variable to enter the model, and a significance level of 0.1 was required for the variable to stay in the model. Two and three-way interactions were added to the model but were removed if not statistically significant. The Hosmer and Lemeshow goodness-of-fit test was used to assess the fit of the final model. RESULTS Summary of Sample Eighty-three failed procedural sedations were identified between January 2007 and December 2011. Five hundred twentythree patients with successful sedations were identified in the comparison group. Summary of Failed Sedation