[Subarachnoid anesthesia: 100 years of an established technique]

Over the 100 years since the introduction of spinal anesthesia into clinical practice, this technique, like most others, has enjoyed varying degrees of popularity. The attraction of spinal anesthesia is easy to identify: a relatively simple technique is used to inject a very small amount of drug into a readily identifiable body compartment to provide deep anesthesia. However, the apparent simplicity of spinal anesthesia is as much as weakness as a strength, given that the technique can be put to use with relatively little understanding of its problems, which are what underlie the shifts in popularity that spinal anesthesia has suffered over the years. In addition to reviewing the history of spinal anesthesia and the local anesthetics and adjuvant drugs administered by this route, we discuss single-dose and continuous spinal injection, combined spinal-epidural technique, and spinal anesthesia for outpatient settings. The problems typical of dural puncture and placement of local anesthetics and adjuvant drugs into the intrathecal space are also reviewed.