Advances in Total Intravenous anesthesia Using Target Controlled Infusion

Abstract

TIVA has become popular, practical and possible only in relatively recent times. There are two main reasons for this. Firstly, unlike other popular intravenous agents of the past, the pharmacokinetic and pharmacodynamic properties of modern drugs like propofol and the newer synthetic, short acting opioids make them very suitable for administration by continuous infusion. Secondly, new concepts in pharmacokinetic modeling and advances in computer technology have allowed the development of sophisticated delivery systems which make control of anesthesia given by the intravenous route as straightforward and user friendly as conventional inhalational techniques. Target controlled infusion is a new mode for total intravenous anesthesia; it is a way of delivering intravenous anesthesia and specifically anesthetic drugs. It avoids the inhalational route and therefore decreases its potential for pollution. The rational for TCI is based on setting a desired “target” concentration which the device achieves and maintains in plasma. Continuous infusions of intravenous anesthetics and analgesics are now commonly used to induce and maintain sedation and general anesthesia. Propofol is the most widely used sedative/hypnotic agent it has a rapid onset due to rapid blood brain equilibration and a relatively rapid offset, Remifentanil is the most commonly used opioid, it is ultra short acting opioid which has a rapid blood brain equilibration. Unintended intraoperative awareness (one of the commonest complication of TIVA), occurs under general anesthesia when a patient becomes aware of some or all events during surgery or a procedure, and has direct recall of those events. All anesthetized patients should be monitored with routine anesthesia monitoring consisted of ECG, pulse oximetry, non invasive arterial pressure at least 5 min interval and a capnography. Bispectral index (BIS) monitor, the first anesthesia depth monitor approved by the FDA is derived from the EEG and measures sedation, hypnosis and loss of consciousness. It has been reported that BIS monitoring is useful to reduce drug consumption and awareness and to shorten recovery time.