title: Detection of hypoventilation by capnography and its association with hypoxia in children undergoing sedation with ketamine.
abstract: OBJECTIVE
  Hypopneic hypoventilation, a decrease in tidal volume without a change in respiratory rate, is not easily detected by standard monitoring practices during sedation but can be detected by capnography. Our goal was to determine the frequency of hypopneic hypoventilation and its association with hypoxia in children undergoing sedation with ketamine.
  
  
  METHODS
  Children who received intravenous ketamine with or without midazolam for sedation in a pediatric emergency department were prospectively enrolled. Heart rate, respiratory rate, pulse oximetry, and end-tidal carbon dioxide (ET(CO2)) levels were recorded every 30 seconds.
  
  
  RESULTS
  Fifty-eight subjects were included in this study. Fifty percent of subjects had recorded ET(CO2) values less than 30 mm Hg without a rise in respiratory rate. Twenty-eight percent of subjects experienced a decrease in pulse oximetry less than 95%. Patients who experienced a persistent decrease in ET(CO2) at least 30 seconds in length were much more likely to have a persistent decrease in pulse oximetry than those with normal or transient decreases in ET(CO2) (relative risk, 6.6; 95% confidence interval, 1.4-30.5). Decreases in ET(CO2) occurred on an average of 3.7 minutes before decreases in pulse oximetry.
  
  
  CONCLUSIONS
  Hypopneic hypoventilation as detected by capnography is common in children undergoing sedation with ketamine with or without midazolam. Hypoxia is frequently preceded by low ET(CO2) levels. Further studies are needed to determine if the addition of routine monitoring with capnography can reduce the frequency of hypoxia in children undergoing sedation.
authors.affiliation: Section of Emergency Medicine, Department of Pediatrics, Yale University School of Medicine, New Haven, CT 06511, USA. Melissa.Langhan@yale.edu
authors.forename: Melissa L
authors.initials: ML
authors.lastname: Langhan
authors.forename: Lei
authors.initials: L
authors.lastname: Chen
authors.forename: Clement
authors.initials: C
authors.lastname: Marshall
authors.forename: Karen A
authors.initials: KA
authors.lastname: Santucci
mesh_terms: D000293:Adolescent; D000778:Anesthetics, Dissociative / Q000008:administration & dosage; D019296:Capnography / Q000379:methods*; D002245:Carbon Dioxide / Q000032:analysis*; D002648:Child; D002675:Child, Preschool; D016292:Procedural Sedation / Q000009:adverse effects* / Q000379:methods; D003937:Diagnosis, Differential; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007040:Hypoventilation / Q000150:complications / Q000175:diagnosis* / Q000378:metabolism; D000860:Hypoxia / Q000209:etiology* / Q000378:metabolism; D007223:Infant; D007275:Injections, Intravenous; D015278:Intensive Care Units, Pediatric; D007649:Ketamine / Q000008:administration & dosage*; D008297:Male; D011446:Prospective Studies; D015203:Reproducibility of Results; D055815:Young Adult
chemical_list: D000778:Anesthetics, Dissociative; D002245:Carbon Dioxide; D007649:Ketamine