Fifty Percent Effective Dose of Intranasal Dexmedetomidine Sedation for Transthoracic Echocardiography in Children with Cyanotic and Acyanotic Congenital Heart Disease.

In this study, the authors used Dixon’s up-and-down method sequential allocation design to determine the ED50 and ED95 of intranasal dexmedetomidine sedation for transthoracic echocardiography in children with cyanotic and acyanotic congenital heart disease.  This sequential allocation method, which was first described by Dixon and Mood in 1948, is a way to estimate the minimum dose which provides a 50% probability of a favourable response1.

50 patients under the age of 18 months were enrolled in the study (27 cyanotic, 23 acyanotic). 25 patients had successful sedation with initial administration, which was defined as successful completion of the TTE examination and adequate diagnostic quality images and report. The ED50 (95% CI) using Dixon’s method was 3.2 (2.78-3.55) micrograms/kg in the cyanotic group and 1.9 (1.69-2.06) micrograms/kg in the acyanotic group. Using isotonic regression with biased-corrected 95% confidence intervals derived by bootstrapping, the ED50 (95% CI) and ED95 (95%CI) were 3.3 (2.48-3.53) and 3.7 (3.44-3.73) micrograms/kg in the cyanotic group and 1.7 (1.00-2.03) and 2.2 (1.96-2.23) micrograms/kg in the acyanotic group.

The sedation onset time, TTE scan time and recovery time for patients who had successful sedation with initial administration were 13.9 ± 4.7 minutes, 10.8 ± 4.6 minutes and 34.2 ± 9.7 minutes in the cyanotic group and 17.5 ± 3.2 minutes, 5.8 ± 2.7 minutes and 32.6 ± 3.1 minutes in the acyanotic group, respectively. There were no adverse events, including unexpected changes in heart rate >20% of normal, with age-adjusted values and SpO2 reduction to <10% of baseline value.

Take home message

This small study adds to large evidence base of dexmedetomidine, particularly the safety of intranasal dexmedetomidine as a sedating agent for non-invasive investigations in children with congenital heart disease. It was interesting to note that children with cyanotic defects required a higher dose than those with acyanotic defects and were not adversely affected by this. The authors postulated that there are pathophysiological reasons why that may be the case, as well as the fact that the scan times for these patients tend to be longer due to their complexity. There were no adverse events recorded in this paper, but that should be considered in the context of a small sample size.

  1. Gorges M, Zhou G, Brant R & Ansermino JM (2017) Sequential allocation trial design in anesthesia: an introduction to methods, modelling, and clinical applications. Paediatr Anaesth, 27:240-247

Reviewed by Dr Scott Ma