End-tidal carbon dioxide monitoring during sedation with a combination of midazolam and ketamine for children undergoing painful, invasive procedures

Background: Previous studies evaluating the respiratory effects of sedation regimens have focused on events such as a decline in O-2 saturation or apn ea, The current study used both end-tidal carbon dioxide (ETCO2) monitoring and pulse oximetry to evaluate the respiratory effects of midazolam and ke tamine, Methods: Fifty children who required sedation during invasive procedures fo rmed the cohort for the study, During sedation, ETCO2 was sampled from nasa l cannulae of spontaneously breathing patients and measured by a side-strea m aspirating infrared device, Results: During the procedure, O-2 saturation decreased by 3% or more in th ree patients, Supplemental oxygen at 2 liters per minute was administered t o these patients. The lowest oxygen saturation was 84%, During the total of 767 minutes of monitoring, there were 3068 ETCO2 values recorded. The high ETCO2 values ranged from 37 to 53 mmHg (40.5 +/- 3.3 mmHg), Ninety percent , or 2760, of the values were 40 mmHg or less, 7% or 214 were between 41 an d 45 mmHg, 3% or 92 were between 46 and 49 mmHg, and 2 isolated values were greater than 50 mmHg, One episode of airway obstruction was identified by noting cessation of the ETCO2 waveform. This was relieved by repositioning the patient's airway. The three episodes of O-2 desaturation, two ETCO2 val ues greater than 50 mmHg, and the episode of upper airway obstruction all o ccurred in three patients. Two of these patients had trisomy 21 with macrog lossia, and the third had had a recent upper respiratory infection and a hi story of tonsillar hypertrophy, Conclusion: The incidence of adverse cardiorespiratory events associated wi th the current sedation regimen of midazolam-ketamine is lower than that re ported with other commonly used regimens. The addition of ETCO2 monitoring provides an additional, monitor to allow for early detection of airway obst ruction or subclinical degrees of respiratory depression.