Clinical uses of intravenous anesthetic and analgesic infusions

Renewed interest in i.v. anesthetic techniques has resulted from the availability of more rapid and shorter-acting i.v. drugs. With recent advances in the area of infusion pump technology, it has become easier to administer i.v. anesthetics and analgesics by continuous infusion techniques. The newer sedative-hypnotic (midazolam, propofol) and analgesic (sufentanil, alfentanil) drugs are better suited pharmacologically to continuous administration techniques than the traditional i.v. agents because they can be more accurately titrated to meet the unique and changing anesthetic needs of the individual patient. With the newer sedative and analgesic drugs, it is now possible to administer i.v. anesthetics in a titrated manner analogous to that which is possible when volatile anesthetics are used. In this way, the drug infusion rate is varied depending on the patient's responses to noxious surgical stimuli. In titrating i.v. drug infusions, consideration must also be given to the age of the patient, pre-existing disease states, potential drug interactions, and proximity to the end of the operative procedure. The availability of rapid and short-acting i.v. drugs like alfentanil and propofol, as well as intermediate-acting muscle relaxants makes it possible to employ total intravenous anesthetic techniques during general surgery. Many non-sedative and non-analgesic i.v. drugs are being investigated in anesthesia for use by continuous infusion techniques, e.g., muscle relaxant, and local anesthetics. Several recent studies have demonstrated the efficacy of continuous infusions of local anesthetics for obstetrical analgesia. The use of continuous local anesthetic infusions makes it possible to achieve improved analgesia (i.e., a more constant degree of analgesia) with lower doses. Improved delivery systems for administering i.v. drugs will make it easier to use continuous infusion techniques in the future. With continued progress in the development of infusion devices and i.v. drugs designed for continuous administration, the use of intravenous anesthetic techniques will become more widespread. In the near future, infusion pumps will likely become standard equipment on all anesthesia machines and anesthesiologists should find these techniques easier to use in their clinical practices.