The Study of EEG Spectrum Analysis as a Method of Monitoring the Depth of Anesthesia / 대한마취과학회지

BACKGROUND: Monitoring the "depth of anesthesia" is an ongoing problem. To identify a useful parameter for determining the depth of anesthesia with enflurane, EEG data was obtained using a Physiolab 800. METHODS: Variations in EEG signals were measured and analyzed by the stage of anesthesia. EEG data was obtained from 15 patients during general anesthesia with enflurane. The EEG signal was acquired and analyzed in 5 steps (one day before anesthesia, during induction, during skin incision, at end of anesthesia, and one day after anesthesia). Fp1 electrode and the EEG data mainly from the forehead were used to determine the depth of anesthesia using EEG characteristics during enflurane anesthesia. All data were preprocessed by filtering, baseline correction and using the linear detrend method to reliable analyze of sample data in the surgical environment. Data obtained were transformed to frequency and power spectrum analysis was performed. RESULTS: alpha, beta, delta and theta waves were detected by frequency area separation and the trend of each wave was observed during each anesthesia stage. EEG data was slowed down and the theta wave ratio increased as the depth of anesthesia increased. Accordingly, spectral edge frequency (SEF) and median frequency (MF) were used as parameters to determine the depth of anesthesia. The frequencies of SEF and MF decreased during anesthesia and returned to the preanesthetic level after the cessation of anesthesia. CONCLUSIONS: Our results suggest that SEF and MF can contribute as useful parameters to determine the depth of anesthesia. Anesthetics not only affect the central nervous system, but also affect the autonomic nervous system. If the autonomic nervous system signals such as heart rate variability are taken into account, more reliable evaluations would be possible.

TThe Evaluation of Anesthesia Depth Using Detrended Fluctuation Analysis Parameters / 대한마취과학회지

BACKGROUND: We examined the use of DFA-Detrended fluctuation analysis-of heart rate variability during general anesthesia in order to assess the depth of anesthesia. METHODS: In this study, we observed changes in alpha1, the short range scaling exponent, in alpha2, the long range scaling exponent, and in the alpha2/alpha 1 ratio during enflurane anesthesia. We monitored 7 stages during general anesthesia, i.e., 1) preoperation (awake state), 2) during induction, 3) after induction, 4) during maintenance, 5) before extubation, 6) after extubation, and 7) postoperation (Next day). RESULTS: The alpha 2/alpha 1 ratio increased during the induction and extubation state compared to preoperation (awake state). This may be related to increased sympathetic activity due to stimulation of the autonomic nervous system. In the postoperation (awakened state), the ratio returned to the preoperation value (awake state). These results are similar to low frequency (LF), high frequency (HF) and LF/HF ratio values which reflect activity of autonomic nervous system. CONCLUSIONS: Detrended fluctuation analysis parameters, especially the alpha 2/alpha 1 ratio, would be used for monitoring the depth of anesthesia. Also these parameters are useful indexes with the LF/HF ratio for the evaluation of sympathetic activity during general anesthesia.

The effect of transcutaneous acupoints stimulation on enflurane anesthesil for craniotomy / 中华麻醉学杂志

The effect of transcutaneous stimulation to Hegu, Fengchi and Yuyao points with Han's Acupoint Nerve Stimulator on enflurane anesthsia and the hemodynamic changes during craniotomy were studied in 80 neurosurgical patients. The results showed that acupoint electric stimulation decreased the inhalating concentration and consumption of enflurane. The expired concentration of enflurane in HANS group was significantly lower than that in control group by a reduction of 37.8 % -47. 0%. The cardiovascular depression was lesser during operation, and the patients recovered faster and more stable after operation in HANS group. It was concluded that acupoint stimulation with HANS significantly potentiated the anesthetic effect and decraesed the side effect of enflurane.

Effect of Enflurane Anesthesia on Patients Treated with Isoniazid / 대한마취과학회지

Enflurane is metabolized in the liver by the hepatic microsomal enzyme system, cytochrome P-450 and induces enzyme during the enflurane exposure. Enhanced biotransformation might occur after enflurane itself and several other drugs, isoniazid (INH), ethanol and cholorpromazine. Increased inorganic fluroide, one of the enflurane metaboites, could impair renal function. The possibility of increased enflurane defluorination follwing treatment with isoniazid, isoniazid group (n=10) and control group (n= 11) was investigated by the measuring the serum and urine F in the preoperative period and 2 hrs after anesthesia, immediate postoperative and 24th postoperative hour. According to the serum inorganic fluoride concentration, the isoniazid group was divided again into INH high F- and INH low F- groups. In the preoperative, immediate postoperative period and 24th postoperative hour, the changes of renal function were measured by the BUN and creatinine and liver function was measured by the SGOT and SGPT. The results were as follows: 1) Serum inorganic fluoride increased in enflurane anesthesia significantly in all three groups and decreased in the 24th postoperative hour. Among the three groups, enhanced defluorination was the highest in the INH high F group. 2) Urine inorganic fluoride was increased in the control and INH high F group. 3) There were no changes in renal and hepatic function after enflurane anesthesia. Our study indicated that enflurane does not harm the INH treated patient.

Responses of vasopressin release in patients with cardiopulmonary bypass anesthetized with enflurane and morphine

Changes in plasma level of arginine vasopressin (AVP), arterial pressure, and urine flow were studied before, during and after cardiopulmonary bypass (CPB) in 11 patients with congenital heart disease. Anesthesia was induced with thiopental sodium (3-5 mg/kg) and was maintained with enflurane (1.0-1.5%), 50% N2O in O2 and morphine (0.5 mg/kg). Concentration of plasma AVP increased slightly from 3.8 +/- 1.5 pg/ml after induction and increased 3-fold after sternotomy. Plasma AVP level increased to 132 +/- 26 pg/ml and 218 +/- 54 pg/ml after 5 and 60 min on CPB, respectively. When the circulation returned to normal, plasma AVP level decreased gradually but was still significantly higher at 24 hr (13.4 +/- 2.5 pg/ml). Marked osmolar diuresis was induced with mannitol in the priming solution used during the CPB: increases in urine flow, Na excretion and osmolar clearance. Possible mechanisms of marked increase in AVP release and differences of AVP responses during CPB reported by other investigators are discussed.