Background Previous studies evaluating the respiratory effects of sedation regimens have focused on events such as a decline in O2 saturation or apnea. The current study used both end-tidal carbon dioxide (ETCO2) monitoring and pulse oximetry to evaluate the respiratory effects of midazolam and ketamine.
Methods Fifty children who required sedation during invasive procedures formed the cohort for the study. During sedation, ETCO2 was sampled from nasal cannulae of spontaneously breathing patients and measured by a side-stream aspirating infrared device.
Results During the procedure, O2 saturation decreased by 3% or more in three patients. Supplemental oxygen at 2 liters per minute was administered to 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 and 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 O2 de-saturation, two ETCO2 values greater than 50 mmHg, and the episode of upper airway obstruction all occurred in three patients. Two of these patients had trisomy 21 with macroglossia, and the third had had a recent upper respiratory infection and a history of tonsillar hypertrophy.
Conclusion The incidence of adverse cardiorespiratory events associated with the current sedation regimen of midazolam-ketamine is lower than that reported with other commonly used regimens. The addition of ETCO, monitoring provides an additional monitor to allow for early detection of airway obstruction or subclinical degrees of respiratory depression.
© 1999 Lippincott Williams & Wilkins, Inc.