Dexmedetomidine: what next?

Drs. McLaughlin and Marik have summarised very well the problem of critical illness delirium and how the results of our trial (Dexmedetomidine to Lessen ICU Agitation: ‘DahLIA’) add to the existing body of evidence supporting dexmedetomidine as a useful drug for its treatment. Our study was confined to patients with both agitation and delirium at the time of randomisation, as we reasoned that the sedative properties of dexmedetomidine would have the greatest benefit in agitated patients. However, both delirium and agitation are fluctuating conditions, and it is likely that in the absence of treatment many of our patients would have manifest both hyperactive and hypoactive forms of delirium at different times. As we noted in the trial manuscript, we cannot say whether the benefit observed with dexmedetomidine was due to a direct anti-delirium effect or due to the reduction in other sedatives, many of which are thought to have a deliriogenic effect. Theoretically, patients with hypoactive delirium should have required little or no sedation. If dexmedetomidine works only by reducing the use of other sedatives, one would therefore expect it to be less effective in patients with long periods of hypoactive delirium. However, in practice, continuous sedative infusions are sometimes titrated at infrequent intervals (especially at night) and being randomised to dexmedetomidine may have resulted in more frequent sedative titration. The bottom line is that we do not know if our results were solely due to a sedative-sparing effect of dexmedetomidine.