Intravenous anaesthesia and the need for new agents.

Ideally one would like a water-soluble, non-irritant, rapidly-acting, smooth induction agent, with no antanalgesic action. Cardiovascular and respiratory depression should be minimal with normal dosage. Since these are unlikely to be achieved with a single drug, the combination of opioid and induction agent offers possibilities that should be explored. A slight delay in onset would not be a major obstacle, provided this is predictable, but the prime need is for a rapidly acting less toxic alternative to thiopentone.