The Poulsen treatment is an expensive medical procedure intended to forestall the aging process and increase an individual's life span. A person's life can be extended indefinitely through several procedures, which must be repeated with increasing frequency as the individual ages (at which point that the procedure becomes an extensive daily routine as illustrated with the quasi-immortal poet, Martin Silenus, in the opening chapters of Endymion). In the second half of the Hyperion Cantos (Endymion and The Rise of Endymion) Poulsen treatments serve as an alternative to utilizing the Pax-modified cruciform for those unwilling to conform to the Holy See's monopoly on human virtual immortality.
Side effects include the subjects skin acquiring a bluish hue, most likely due to the life-extending solutions of the unnamed chemicals which are pumped through an individual's circulatory system during each Poulsen treatment (as individuals seem to become bluer after each treatment). Another side-effect of individuals whom utilize Poulsen treatments is a dependency on the treatments, though it is unsure whether this dependency is physical or psychological.
Androids such as A. Bettik are blue in color due to their internal Poulsen treatment system, which constantly rejuvenates their bodies, being partially responsible for their incredibly long lifespans.