Patients have reservations regarding general anesthesia due to fear of complications. This has led to greater use of total intravenous anesthesia for breast augmentation surgery. This type of anesthesia has some advantages over general anesthesia with endotracheal intubation such as having none of the side effects associated with inhalation anesthetic agents that are used in general anesthesia. Moreover, because patients have mobility under total intravenous anesthesia, deep vein thrombosis might not occur at all, and the expenditure on anesthesia can be reduced. In addition, the time spent on the induction of anesthesia and endotracheal intubation can also be reduced.
The use of anesthetic agents with prompt action and a short half-life would be both more convenient and safer for performing a surgical procedure under intravenous anesthesia [12
]. The intravenous anesthetics that are commonly used in a clinical setting are benzodiazepine, propofol, barbiturate, opioid, ketamine, and β-2 agonist. Considering the overall status of patients, the types and scope of surgery, and the severity of pain, these anesthetics might be used solely or concomitantly. In particular, propofol is a sedative that is commonly used. A 3-compartment model study showed that the initial distribution half-life of propofol is approximately 2 to 4 minutes [13
]. The effects of sedation and anesthesia are seen 40 seconds after administration. Even after prolonged administration, patients recover rapidly [13
]. Several studies have reported that it causes a lower incidence of nausea and vomiting following surgery [14
Local anesthesia might insufficiently control pain. In these cases, opioid can be infused. Remifentanil is a recently introduced opioid that is an analgesic substance that acts on the µ receptors. It is promptly degraded by the action of non-specific esterase present in the plasma and tissue. Approximately 4 minutes elapses until the plasma level of remifentanil decreases by 50% after its infusion has been terminated following a long-term infusion. It is therefore characterized by a lack of deposition despite repeated dosing or long-term infusion [16
]. In particular, if remifentanil is concomitantly used with propofol, it undergoes an independent pathway from propofol [17
]. Moreover, compared with other types of opioid, remifentanil has hemodynamic stability during most of the surgical procedure [18
If drugs are administered for the purpose of performing total intravenous anesthesia, the continuous administration of drugs rather than the intermittent administration of drugs helps to maintain the plasma level of drugs above a certain level of concentration and thereby to keep the sedative effects optimal. In particular, TCI is a system for administering drugs continuously at a dose that has been calculated using a computer based on the status of the patient and the pharmacokinetic characteristics of the drugs to ensure that the theoretical target concentration is maintained. The major benefits of this approach are that clinicians can take immediate measures against an inappropriate depth of anesthesia without any complicated mathematical calculations.
The clinical application of TCI was first introduced by Schwilden and Schuttler [19
] in 1990. Since then, it has been developed into the current type of TCI system such that the methods of infusion based on the pharmacokinetic profile can be selected using software. It has already had pharmacokinetic parameters for various types of drugs installed. It has been designed to infuse drugs to achieve a level of concentration at the target sites as well as the plasma concentration. A recent study has shown that the degree of hemodynamic stability was higher following the use of TCI than after the manual administration of remifentanil [20
As described here, while maintaining a relatively accurate level of the plasma concentration with the use of a TCI system, the depth of anesthesia can be simply adjusted. This establishes an environment where surgeons can concentrate on the surgical procedure. However, monitoring and management of patients should be performed with the same level of attention as is paid during general anesthesia. Patients can be abruptly converted from minimal sedation to a deep level. This might also lead to respiratory depression, hypoxia, and pulmonary aspiration. Meticulously monitoring patients is therefore mandatory. Finally, the status of consciousness should be appropriately evaluated. For the evaluation of a patient's state of consciousness, clinical parameters should be used. It can also be evaluated using objective parameters based on electrophysiologic methods such as the bispectral index [6
Our results showed some of the patients showed involuntary movement to some extent depending on the magnitude of intraoperative pain or each patient's sensitivity to pain. The time of the persistent presence of stimuli was relatively short. Additionally, the range of motion was limited. Accordingly, there were no interferences with the surgical procedure.
The limitation of the current study is that no cost-effectiveness analysis was attempted. Several studies have explained that anesthesia using propofol and remifentanil is more expensive than other anesthetic methods [21
]. Considering the medical personnel and equipment associated with anesthesia, however, it would be more cost-effective to use these drugs than traditional anesthesia; this deserves further study.
In conclusion, the following matters should be considered in performing safe surgery under total intravenous anesthesia using the TCI system: 1) A patient's choice is a key factor. Most of the patients who are in need of breast augmentation correspond to the American Society of Anesthesiologists status I or II group. 2) Surgeons should be familiar with the drugs that are used for anesthesia; that is, they should be aware of the variability of intravenous anesthetics and their side effects. 3) In emergency situations, surgeons should use equipment to maintain the airway. Thus, appropriate measures should be taken against hemodynamic derangements such as the abrupt occurrence of respiratory insufficiency and hypotension. A patient's safety should be the first priority, even over cost effectiveness. Therefore, a thorough medical history and physical examination should be performed for each patient. Backup support of anesthesiologists or experienced medical practitioners is also needed as well as an adequate patient transfer system to inpatient hospitals. The anesthetic techniques presented in this paper may require the help and supervision of an anesthesiologist at first.
A retrospective analysis of our clinical series of patients suggests that anesthetic methods under total intravenous anesthesia based on the TCI system using propofol and remifentanil are more convenient than manually controlled infusion and the procedure might replace general anesthesia with endotracheal intubation in breast augmentation surgery.