OBJECTIVE: To examine the predicted effect-site concentration of propofol at two clinical end-points: loss of verbal contact (LVC) and loss of consciousness (LOC), and to explore the relationship between bispectral index (BIS) values, cerebral state index (CSI) values and the predicted effect-site concentration during the target-controlled infusion of propofol. METHODS: In 20 patients during the target-controlled infusion of propofol, the propofol infusion was set at an initial effect-site concentration of 0.5 mg/L, and increased by 0.5 mg/L every 5 min until 5 min after the modified observer's assessment of alertness/sedation scale (OAA/S) values reached zero. The predicted effect-site concentration of propofol, the values of CSI and BIS were recorded, and the sedation level was examined by the modified OAA/S every 20s. The predicted effect-site concentrations of propofol in target-controlled infusion (TCI) system were recorded when they increased by more than 0.1 mg/L. The predicted effect-site concentrations of propofol and the values of BIS and CSI at LVC and LOC in 5%, 50% and 95% of the patients were calculated. RESULTS: There was good linearity between BIS and the predicted effect-site concentration of propofol (R(2)=0.787), as well as between CSI and the predicted effect-site concentration of propofol (R(2)=0.792). The predicted effect-site concentrations of propofol at LVC in 5%, 50% and 95% of the patients were 1.1,1.8 and 2.4 mg/L, respectively. The values of BIS and CSI at LVC in 5%, 50% and 95% of the patients were 79.2, 69.2 and 59.2; 74.9, 65.9 and 56.8, respectively. The predicted effect-site concentrations of propofol at LOC in 5%, 50% and 95% of the patients were 1.5, 2.5 and 3.4 mg/L, respectively. At LOC, the values of BIS and CSI in 5%, 50% and 95% of the patient were 73.6, 57.1 and 40.6; 65.2, 54.8 and 44.3, respectively. CONCLUSION During target-controlled infusion of propofol, LVC and LOC occur within a definite range of predicted effect-site concentrations. There is the good linearity between BIS, CSI and the predicted effect-site concentrations of propofol. CSI may be more useful than BIS in predicting LVC and LOC.
Adult ; Anesthetics, Intravenous ; administration & dosage ; pharmacology ; Electroencephalography ; Female ; Humans ; Male ; Monitoring, Intraoperative ; Propofol ; administration & dosage ; pharmacology

Four major factors affecting anesthetic choices in surgery include the requirements of surgery (including type and location), anesthesiologist's experience and expertise, patient's preference, and the surgeon's preference. Especially, the type and location of surgical procedure may limit anesthetic techniques and choice of anesthetic agents. Available anesthetic techniques consist of three basic options: regional anesthesia, monitored anesthesia care (MAC), and general anesthesia. Recent advances in nerve stimulators and ultrasound guidance devices help to make regional blocks more successful with less complications. MAC is increasingly used with given advantages of supplying sedation, anxiolysis, additive analgesia, and improved safety to patients. Remarkable advances in general anesthesia include total intravenous anesthesia (TIVA) and fast-track anesthesia to use drugs with rapid action and short duration including propofol, desflurane, and sevoflurane, and advanced equipments such as target-controlled infusion pumps and monitoring devices of anesthetic depth. Advances in medical technology and pharmacology will continue to develop newer anesthetic agents, techniques, and patterns.
Analgesia ; Anesthesia ; Anesthesia, Conduction ; Anesthesia, General ; Anesthesia, Intravenous ; Anesthetics ; Humans ; Infusion Pumps ; Pharmacology ; Propofol ; Ultrasonography

OBJECTIVETo observe the effect of electro-acupuncture (EA) on auto regressive with exogenous input model (ARX-model) auditory evoked index (AAI) in patients anesthetized with different anesthetics.

METHODSForty-eight adult patients undergoing scheduled surgical operation were enrolled and divided into two groups (24 in each group) according to the anesthetics applied, Group A was anesthetized with propofol sedation and Group B with Isoflurane-epidural anesthesia. Group A was subdivided into three groups of low, middle and high concentration of target effect-site of 1.0 microg/ml, 1.5 microg/ml and 2.0 microg/ml through target controlled infusion (TCI) and Group B into 3 subgroups of minimum alveolar effective concentration of isoflurane (0.4 MAC, 0.6 MAC and 0.8 MAC for B1, B2 and B3 subgroups) respectively, with 8 patients in every subgroup. EA on acupoints of Hegu (LI4) and Neiguan (P6) was applied on all the patients during anesthesia, and the change of AAI at various time points was recorded.

RESULTSIn the three subgroups of Group A, levels of AAI were significantly elevated in the first few minutes after EA, and significantly lowered 20 min after EA in subgroup A2. While in the subgroups of Group B, except the elevating in Group B1 1-2 min after EA, levels of AAI remained unchanged at other time points.

CONCLUSIONPain response could be reflected by AAI during EA. EA could enhance the sedative effect of propofol in middle concentration, but its effect on isoflurane epidural anesthesia is insignificant.

Acupuncture Points ; Adult ; Anesthesia, General ; Anesthetics ; pharmacology ; Anesthetics, Inhalation ; pharmacology ; Anesthetics, Intravenous ; pharmacology ; Conscious Sedation ; Electroacupuncture ; Evoked Potentials, Auditory ; drug effects ; Female ; Humans ; Isoflurane ; pharmacology ; Laparotomy ; Male ; Middle Aged ; Monitoring, Intraoperative ; Pain Measurement ; Propofol ; pharmacology

The deficiency of aquaporin-4 (AQP4) has been reported to alter release of neurotransmitters in the mouse brain. However, the functional relevance of AQP4 in mediating essential components of the general anaesthetic state is unknown. The aim of the present study was to investigate the role of AQP4 in general anaesthesia in mice lacking AQP4. The hypnotic effects of propofol, ketamine, and pentobarbital in AQP4 knockout (KO) and CD1 control mice were evaluated using the behavioural endpoint of loss of righting reflex (LORR). The effects of propofol on extracellular levels of amino acids in prefrontal cortex of freely moving mice were investigated using microdialysis coupled to high performance liquid chromatography with fluorescent detection. The result showed that, after receiving ketamine or pentobarbital, LORR occurred at earlier time in KO mice than that in control animals. Intraperitoneal injection of ketamine or pentobarbital increased the duration of LORR. After the administration of propofol, the duration of LORR was significantly reduced in KO mice compared with that in controls. Propofol increased the extracellular levels of aspartate, glutamate, and GABA, but not taurine, in prefrontal cortex. There were significant differences of increase patterns of the three kinds of neurotransmitters between KO and WT mice. Notably, the duration of GABA level increase correlated with the duration of LORR in two genotypes of mice. These results provide in vivo evidence of different responses in time-dependent release of excitatory and inhibitory neurotransmitters in prefrontal cortex of the two genotypes of mice. It is suggested that changes in anaesthetic reactions in mice with AQP4 loss may be related to neurotransmitter regulation, and that normal functioning of AQP4 plays an important role in the maintenance of anaesthetic hypnosis.
Anesthetics, Intravenous ; pharmacology ; Animals ; Aquaporin 4 ; deficiency ; genetics ; Hypnotics and Sedatives ; pharmacology ; Ketamine ; pharmacology ; Mice ; Mice, Knockout ; Neurotransmitter Agents ; metabolism ; Pentobarbital ; pharmacology ; Prefrontal Cortex ; drug effects ; metabolism ; Propofol ; pharmacology

OBJECTIVETo explore the anesthetic effects of repeated administration of propofol combined with vitamin C in mice.

METHODSForty mice were subjected to daily intraperitoneal injections of 80 mg/kg propofol (P80 group), 70 mg/kg propofol and 50 mg/kg vitamin C (P70+Vc50 group), 55 mg/kg propofol and 100 mg/kg vitamin C (P55+Vc100 group), or 50 mg/kg propofol and 200 mg/kg vitamin C (P50+Vc200 group) for 6 consecutive days, and the anesthesia induction time and anesthesia duration were recorded.

RESULTSCompared with the P80 group, the mice in P55 + Vc100 group and P50 + Vc200 group showed significantly shorter anesthesia duration on the first 3 days (P<0.05). In all the groups, anesthesia duration was significantly shortened in the following days compared with that on day 1 (P<0.01); anesthesia duration was shorter on day 3 than on day 2 in P50 + Vc200 group (P<0.01), and was shorter on days 4, 5, and 6 than on day 2 in all the groups (P<0.01). In all the groups, the rate of loss of righting reflex (LORR) decreased gradually with time in a similar pattern.

CONCLUSIONVitamin C can reduce the dose of propofol without obviously affecting the anesthetic effect to reduce the incidence of drug tolerance and potential dose-related side effects of propofol.

Anesthesia ; Anesthesia Recovery Period ; Anesthetics, Intravenous ; administration & dosage ; pharmacology ; Animals ; Ascorbic Acid ; administration & dosage ; pharmacology ; Drug Tolerance ; Mice ; Propofol ; administration & dosage ; pharmacology

Anesthetics, Intravenous ; pharmacology ; Animals ; Aorta, Thoracic ; drug effects ; physiology ; Endothelium, Vascular ; physiology ; Female ; In Vitro Techniques ; Male ; Norepinephrine ; pharmacology ; Potassium Channels ; physiology ; Propofol ; pharmacology ; Rabbits ; Vasodilation ; drug effects

PURPOSE: Opioids may affect changes in the corrected QT interval (QTc) during anesthetic induction. This study examine whether a single bolus of remifentanil would prolong QTc after laryngeal mask airway (LMA) insertion during sevoflurane induction. MATERIALS AND METHODS: Forty women of American Society of Anesthesiologists physical status 1 (ASA PS1) undergoing gynecological surgery were studied. All patients were induced using three vital capacity inhalation inductions with 5% sevoflurane. Two minutes after induction, the inspiratory concentration of sevoflurane was reduced to 2%. Using double-blinded randomization, patients were allocated into one of two groups, receiving either saline (placebo group, n = 20) or 0.25 microg.kg-1 remifentanil (remifentanil group, n = 20) over a period of thirty seconds. Sixty seconds later, LMA insertion was performed. Recordings were taken with a 12-lead electrocardiogram at baseline, 2 min after induction and 1 and 3 min after LMA insertion. QTc was calculated by Bazett's formula. The mean arterial pressure (MAP) and heart rate (HR) were also measured at each time point. RESULTS: The QTc interval was significantly prolonged in the placebo group as compared to the remifentanil group at 1 min after LMA insertion (467.8 +/- 16.5 vs. 442.7 +/- 21.3 ms, p < 0.001). However, there was no significant difference in QTc at 3 min after LMA insertion between the two groups. MAP and HR were significantly higher in the placebo group (p < 0.001). CONCLUSION: A single bolus of remifentanil is safe method to attenuate prolonged QTc associated with insertion of LMA.
Adult ; Anesthetics, Inhalation/adverse effects/*pharmacology ; Anesthetics, Intravenous/administration & dosage/*pharmacology ; Electrocardiography/drug effects ; Female ; Gynecologic Surgical Procedures/adverse effects ; Heart Rate/*drug effects ; Humans ; Methyl Ethers/adverse effects/*pharmacology ; Middle Aged ; Piperidines/*pharmacology

BACKGROUNDPrevious studies demonstrated general anesthetics affect potassium ion channels, which may be one of the mechanisms of general anesthesia. Because the effect of etomidate on potassium channels in rat hippocampus which is involved in memory function has not been studied, we investigated the effects of etomidate on both delayed rectifier potassium current (I(K(DR))) and transient outward potassium current (I(K(A))) in acutely dissociated rat hippocampal pyramidal neurons.

METHODSSingle rat hippocampal pyramidal neurons from male Wistar rats of - 10 days were acutely dissociated by enzymatic digestion and mechanical dispersion according to the methods of Kay and Wong with slight modification. Voltage-clamp recordings were performed in the whole-cell patch clamp configuration. Currents were recorded with a List EPC-10 amplifier and data were stored in a computer using Pulse 8.5. Student's paired two-tail t test was used for data analysis.

RESULTSAt the concentration of 100 micromol/L, etomidate significantly inhibited I(K(DR)) by 49.2% at +40 mV when depolarized from -110 mV (P < 0.01, n = 8), while did not affect I(K(A)) (n = 8, P > 0.05). The IC(50) value of etomidate for blocking I(K(DR)) was calculated as 5.4 micromol/L, with a Hill slope of 2.45. At the presence of 10 micromol/L etomidate, the V1/2 of activation curve was shifted from (17.3 +/- 1.5) mV to (10.7 +/- 2.9) mV (n = 8, P < 0.05), the V1/2 of inactivation curve was shifted from (-18.3 +/- 2.2) mV to (-45.3 +/- 9.4) mV (n = 8, P < 0.05). Etomidate 10 micromol/L shifted both the activation curve and inactivation curve of I(K(DR)) to negative potential, but mainly affected the inactivation kinetics.

CONCLUSIONSEtomidate potently inhibited I(K(DR)) but not I(K(A)) in rat hippocampal pyramidal neurons. I(K(DR)) was inhibited by etomidate in a concentration-dependent manner, while I(K(A)) remained unaffected.

Anesthetics, Intravenous ; pharmacology ; Animals ; Delayed Rectifier Potassium Channels ; drug effects ; physiology ; Etomidate ; pharmacology ; Male ; Potassium Channels ; drug effects ; physiology ; Pyramidal Cells ; drug effects ; physiology ; Rats ; Rats, Wistar

OBJECTIVETo study the effect of propofol at different effect-site concentrations on approximate entropy (ApEn) of transient evoked otoacoustic emission (TEOAE) signals in adults and investigate the possibility of using ApEn for monitoring anesthesia depth.

METHODSFifteen ASA class I or II patients (aged 18-49 years with normal hearing) undergoing elective surgery under general anesthesia were enrolled in this study. Anesthesia was maintained with target-controlled infusion of propofol. With the effect-site concentrations of 1, 2, 3 and 4 microg/ml, TEOAE signals were monitored and recorded before and after anesthesia. ApEn of TEOAE in 4 frequency ranges (0-2, 1-3, 2.5-4.5, and 4-6 kHz) were calculated using MATLAB software.

RESULTSThe ApEn of TEOAE in different frequency ranges showed no significant differences at the same effect-site concentration of propofol, or at different effect-site concentrations in the same frequency range (P>0.05).

CONCLUSIONAnesthesia with propofol at different effect-site concentrations does not obviously affect ApEn of TEOAE signals in adults, and ApEn can not be used as the indicator for evaluating the depth of anesthesia.

Adolescent ; Adult ; Anesthetics, Intravenous ; pharmacology ; Entropy ; Female ; Humans ; Male ; Middle Aged ; Monitoring, Intraoperative ; methods ; Otoacoustic Emissions, Spontaneous ; drug effects ; Propofol ; pharmacology ; Young Adult

BACKGROUNDAs a new electroencephalogram (EEG) signal processing technique for monitoring the depth of anesthesia, entropy consists of two indices: reaction entropy (RE) and state entropy (SE). Our study compared entropy with classical bispectral index (BIS) in reduction of myoelectrical interference and noxious stimuli with EEG signals.

METHODSTwo hundred and eighty patients (ASA I-II, 18-60 years old) undergoing scheduled surgeries from seven medical centers were enrolled. Anesthesia induction was managed with propofol via the target-controlled infusion (TCI) system. The results of BIS, RE, SE, mean arterial pressure (MAP) and heart rate (HR) were recorded before anesthesia induction, at the moment of unconsciousness, before and 2 minutes after administration of muscle relaxant, and before and one and three minutes after the tracheal intubation.

RESULTSThe values of half maximum effective concentrations (EC50), 5% effective concentrations (EC05) and 95% effective concentrations (EC95) of propofol effect-site concentration at the onset of unconsciousness were 1.2 (1.1-1.3 µg/ml), 2.5 (2.4-2.5 µg/ml) and 3.7 (3.7-3.8 µg/ml), while those of the predicted plasma propofol concentration were 2.8 (2.7-2.9 µg/ml), 3.9 (3.8-3.9 µg/ml) and 4.9 (4.8-5.0 µg/ml), respectively. The values of BIS, SE and RE were 62, 59 and 63 when 50% of patients lost consciousness, and 79, 80, 85 and 42, 37, 44, respectively, when 5% and 95% of patients were unconscious. The values of BIS, RE and SE dropped two minutes after the injection of muscle relaxant, but there were no significant differences between RE and SE. MAP and HR increased visibly, which indicated a reaction to tracheal intubation; the values of BIS, RE and SE, however, did not display any significant changes.

CONCLUSIONSThis large-sample multicentric study confirmed the values of RE and SE as approximating BIS value, at the onset of unconsciousness during propofol TCI anesthesia. After elimination of myoelectrical activation, all values of RE, SE and BIS decreased significantly and the three indices were less sensitive to noxious stimuli than cardiovascular responses.

Adult ; Anesthesia ; Anesthetics, Intravenous ; pharmacology ; Blood Pressure ; Electroencephalography ; Electromyography ; Entropy ; Female ; Heart Rate ; Humans ; Male ; Middle Aged ; Monitoring, Physiologic ; Propofol ; blood ; pharmacology