Monitoring of Anesthetic Depth by BIS & Anemon Monitor / 대한마취과학회지

BACKGROUND: Monitoring of "Depth of anesthesia" is an ongoing problem in anaesthesia. In this study, the author has compared the bispectral index (BIS) and Anemon monitor for monitoring depth of anesthesia in propofol or isoflurane anesthesia. METHODS: Anemon-1 and BIS index were obtained from 24 patients (ASA I, II) during general anesthesia with propofol or isoflurane. For patients in the propofol group, anesthesia was induced with fentanyl 100ng followed by propofol 2 mg/Kg. For patients in the isoflurane group, anesthesia was induced with thiopental 5 mg/Kg. The author observed changes of these values at 5 major times: before induction, during induction, after induction, at sKin incision, before extubation, after extubation. RESULTS: The anemon index showed a significant increase during induction (propofol group: 86.9 +/- 26.4, isoflurane group: 106.0 +/- 18.6) and at sKin incision (propofol group: 89.9 +/- 22.7, isoflurane group: 92.0 +/- 23.1), but this did not correlate with the level of consciousness. The BIS index showed a significant decrease in the score after induction (propofol group: 55.0 +/- 9.6, isoflurane group: 61.0 +/- 17.2), but no response to surgical stimuli. CONCLUSIONS: BIS had a good correlation with level of consciousness. The Anemon-1 index was recognized to reflect invasive stimulus. As the BIS and Anemon-1 had no correlation, it was not possible to assume changes of each index from the other. Both the anemon-1 index and BIS are useful to monitor the anesthesia level during surgery.

The Relationship between Intraoperative Spirometry and Prognosis of Lung Volume Reduction Surgery in Patients with Severe Emphysema / 대한마취과학회지

BACKGROUND: Lung volume reduction surgery (LVRS) for severe emphysema can significantly improve maximal expiratory flow rates and ameliorate dyspnea on exertion, probably by reducing airway resistance and by reducing hyperinflation with corresponding improvement in inspiratory muscle function. We have recently experienced 12 cases of bilateral LVRS in patients with severe emphysema in an effort to improve pulmonary function. Among these patients we examined the relationship between intraoperative spirometry and prognosis of LVRS. METHODS: Intraoperative total dynamic lung compliance (CT) and % of breath exhaled in one second (V1.0%) obtained immediately pre-lung reduction was compared with immediate post-lung reduction. In addition we also compared a preoperative pulmonary function test (PFT) [FEV1, TLC, and FRC] with 3 month postoperative values. RESULTS: Six of the twelve patients demonstrated post-reduction improvement in dynamic CT and V1.0% during LVRS. These six patients demonstrated an increase in FEV1 and a decrease in TLC, and FRC 3 months after an LVRS. The other six patients without improvement in V1.0% during an LVRS had no change in the PFT three months after an LVRS. CONCLUSIONS: It appears that sidestream spirometry with immediate intraoperative measurement of dynamic CT and V1.0% could play a role in predicting the expected follow-up objective PFT; improvement in both CT and V1.0% may predict significant increases in PFT.

Effect of Continuous Infusion of Low Concentrations of Ketamine on the Bispectral Index and Recovery from Propofol-N2O-O2 Anesthesia / 대한마취과학회지

BACKGROUND: Ketamine as an analgesic adjunct in propofol-based anesthesia has the benefit of potent analgesic action and more stable vital signs due to sympathetic stimulation. However, its impact on the bispectral index and speed of recovery is still controvertial. The aim of this study was to evaluate the effects of continuous infusion of low concentrations of ketamine (0.1 microgram/ml) on the bispectral index and speed of recovery from propofol-N2O-O2 anesthesia. METHODS: Forty ASA I or II adult patients scheduled for elective orthopedic surgery were randomly allocated to one of two groups according to intraoperative ketamine use. In group P, anesthesia was induced and maintained with propofol (Ct: 3 - 6 microgram/ml), 67% nitrous oxide and 33% oxygen and the target concentration of propofol was kept at 4 microgram/ml at least 20 min before the end of propofol infusion. In group P + K, the method of anesthesia was same as in group P, but the low concentration (0.1 microgram/ml) of ketamine was continuously infused until discontinuation of propofol using computer-assisted continuous infusion. Bispectral index, recovery time from anesthesia, current/effect concentration of drugs, vital signs before and at induction, end of drug infusion, eye opening time on verbal command, and orientation time were checked. RESULTS: Changes in vital signs showed no differences between the groups. For bispectral index, there was no difference between groups initially, but it was higher (4 - 8) after the end of drug infusion in group P K than in group P. Also, recovery from anesthesia was delayed significantly in group P + K (P < 0.05). CONCLUSIONS: From these observations, we concluded that the use of low concentrations of ketamine during propofol-N2O-O2 anesthesia increased BIS, delayed eye opening and recovery from anesthesia without any benefit to vital sign stability.

Correlations among Bispectral Index, Observer's Assessment of Alertness/sedation (OAA/S) Scale and Blood Concentration during Anesthesia Induction with Etomidate / 대한마취과학회지

BACKGROUND: Etomidate is a rapid-acting sedative/hypnotic agent with little or no cardiovascular effect and a high therapeutic index. For this reason, etomidate has been used as an anesthetic induction and maintenance agent in patients with poor cardiovascular reserve. Bispectral index (BIS), a parameter derived from electroencephalography (EEG), has been proposed as a measure of anesthetic effect and is shown to correlate with increasing sedation and loss of consciousness. To establish its utility for this purpose, it is important to determine the correlation among BIS, measured drug concentration, and increasing levels of sedation. This study was designed to evaluate this relation for etomidate. METHODS: Eighteen adult patients scheduled for elective surgery, ASA physical status I or II, were included. Etomidate was administerd until loss of consciousness (loss of verbal contact) using syringe pump with a constant rate (150 ml/h) and patients were observed until regaining consciousness as decided by prompt verbal response on command of "open your eyes". A BIS was monitored, arterial blood samples were obtained for analysis of drug concentration, and the patients were evaluated for level of sedation by the responsiveness portion of the modified observer's assessment of alertness/sedation (OAA/S) scale. RESULTS: The BIS (r = 0.86) correlated significantly with the OAA/S more than the etomidate plasma concentration (r = 0.57). The BIS values, OAA/S, and blood concentrations were 50, 1.26, and 1337 ng/ml at induction and 75, 4.6, and 236 ng/ml at awakening, respectively. CONCLUSIONS: We concluded that the BIS accurately predicted level of sedation with etomidate during anesthesia induction, but the correlation between blood concentration and level of sedation was less strong.

An Experience of BIS Monitoring for the Measurement of Hypnotic State during General Anesthesia Using a Propofol TCI / 대한마취과학회지

Understanding depth of anesthesia is essential for the anesthesiologist. Although electroencephalogram (EEG) has been proposed and studied as a method of determining anesthetic depth, major limitations restrict its usefulness. For example, spectral edge frequency (SEF) dose not correlate well with the level of sedation. However, recently introduced bispectral index (BIS) which is derived from frequency, amplitude and coherence of the EEG is strongly correlated with clinical measurements of sedation and hypnosis. BIS monitoring may be used to guide the titration of anesthetic agents to achieve effective dosing without increasing the risk of awareness and to allow a better balance of hypnotic and analgesic administration. We report two cases of successful BIS monitoring for the measurement of intraoperative hypnotic state of patient during propofol target controlled infusion (TCI).