The influence of gender on loss of consciousness with sevoflurane or propofol

Studies have suggested that hypnotic requirements for general anesthesia and emergence may be influenced by gender. In this study, we examined the effect of gender on the hypnotic requirement for loss of consciousness (LOC) using either a volatile (sevoflurane) or an IV (propofol) anesthetic. One-hundred-fifteen unpremedicated, ASA physical status I-II patients, aged 18-40 yr old, received either sevoflurane by mask to a predetermined end-tidal concentration (%ET(sevo)) or propofol by target-controlled infusion (effect site) while breathing spontaneously. After sufficient time for equilibration, LOC was assessed by lack of response to mild prodding. The up-down method of Dixon was used to determine the hypnotic target concentration at 50% response (LOC(50)). No statistically significant difference in LOC(50) was noted between men and women for sevoflurane (0.83% +/- 0.1% and 0.92% +/- 0.09% ET, respectively). Men required significantly more propofol than women (2.9 +/- 0.2 versus 2.7 +/- 0.1 microg/mL, respectively). However, there was no difference in the bispectral index (BIS) at LOC for men or women with either hypnotic anesthetic. This investigation identified a small, statistically significant difference in hypnotic requirement at LOC(50) between men and women with propofol but not with sevoflurane. As defined by BIS, men and women had equivalent hypnotic states at LOC(50), indicating that gender had no clinically significant effect on hypnotic requirements. However, BIS at a defined clinical end-point (LOC(50)) was significantly different between the sevoflurane and propofol groups, suggesting that neurophysiological effects of these anesthetics may be different. IMPLICATIONS: Gender affects the dosing requirements for, and response to, many drugs used in anesthetic practice. Loss of consciousness is an early clinical marker of hypnotic drug effect. We found no significant difference to either an inhaled (sevoflurane) or IV (propofol) anesthetic related to patient gender.     

Propofol and remifentanil effect-site concentrations estimated by pharmacokinetic simulation and bispectral index monitoring during craniotomy with intraoperative awakening for brain tumor resection

Different anesthetic techniques have been suggested for craniotomy with intraoperative awakening. We describe an asleep-awake-asleep technique with propofol and remifentanil infusions, with pharmacokinetic simulation to predict the effect-site concentrations and to modulate the infusion rates of both drugs, and bispectral index (BIS) monitoring. Five critical moments were defined: first loss of consciousness (LOC1), first recovery of consciousness (ROC1), final of neurologic testing (NT), second loss of consciousness (LOC2), and second recovery of consciousness (ROC2). At LOC1, predicted effect-site concentrations of propofol and remifentanil were, respectively, 3.6+/-1.2 microg/mL and 2.4+/-0.4 etag/mL. At ROC1, predicted effect-site concentrations of propofol and remifentanil were, respectively, 2.1+/-0.3 microg/mL and 1.8+/-0.3 etag/mL. At NT, predicted effect-site concentrations of propofol and remifentanil were, respectively, 0.9+/-0.3 microg/mL and 1.8+/-0.2 etag/mL. At LOC2, predicted effect-site concentrations of propofol and remifentanil were, respectively, 2.1+/-0.2 microg/mL and 2.5+/-0.2 etag/mL. At ROC2, predicted effect-site concentrations of propofol and remifentanil were, respectively, 1.2+/-0.5 microg/mL and 1.4+/-0.2 etag/mL (data are mean+/-SE). A significative correlation was found between BIS and predicted effect-site concentrations of propofol (r=0.547, P<0.001) and remifentanil (r=0.533, P<0.001). Multiple regression analysis between BIS and propofol and remifentanil predicted effect-site concentrations at the different critical steps of the procedure was done and found also significative (r=0.7341, P<0.001).     

Early pregnancy does not reduce the C(50) of propofol for loss of consciousness.

Requirements for inhaled anesthetics decrease during pregnancy. There are no published data, however, regarding propofol requirements in these patients. Because propofol is often used for induction of general anesthesia when surgery is necessary in early pregnancy, we investigated whether early pregnancy reduces the requirement of propofol for loss of consciousness using a computer-assisted target-controlled infusion (TCI). Propofol was administered using TCI to provide stable concentrations and to allow equilibration between blood and effect-site (central compartment) concentrations. Randomly selected target concentrations of propofol (1.5-4.5 microg/mL) were administered to both pregnant women (n = 36) who were scheduled for pregnancy termination and nonpregnant women (n = 36) who were scheduled for elective orthopedic or otorhinolaryngologic surgery. The median gestation of the pregnant women was 8 wk (range, 6-12 wk). Venous blood samples for analysis of the serum propofol concentration were taken at 3 min and 8 min after equilibration of the propofol concentration. After a 10-min equilibration period of the predetermined propofol blood concentration, a verbal command to open their eyes was given to the patients twice, accompanied by rubbing of their shoulders. Serum propofol concentrations at which 50% of the patients did not respond to verbal commands (C(50) for loss of consciousness) were determined by logistic regression. There was no significant difference in C(50) +/- SE of propofol for loss of consciousness between the Nonpregnant (2.1 +/- 0.2 microg/mL) and Pregnant (2.0 +/- 0.2 microg/mL) groups. These results indicate that early pregnancy does not decrease the concentration of propofol required for loss of consciousness. IMPLICATIONS: The C(50) of propofol for loss of consciousness in early pregnancy did not differ from that in nonpregnant women, indicating that there is no need to decrease the propofol concentration for loss of consciousness when inducing general anesthesia for termination of pregnancy.     

Propofol concentration requirement for laryngeal mask airway insertion was highest with the ProSeal, next highest with the Fastrach, and lowest with the Classic type, with target-controlled infusion

STUDY OBJECTIVE: To determine propofol concentration of plasma 50% (Cp50, concentration at which there is a 50% chance that patients show no movement in response) for the Classic-, Fastrach-, and ProSeal-type laryngeal mask airway (LMA) insertion using target-controlled infusion (TCI) technique. DESIGN: Prospective, randomized, comparative study. SETTING: University-affiliated hospital. PATIENTS: Sixty American Society of Anesthesiologists physical status I and II women scheduled for minor gynecologic operations. INTERVENTIONS: Propofol TCI (Diprifusor pharmacokinetic model) was started at target concentration using an anesthesia pump. After reaching target effect-site concentration of propofol, 1 of the 3 types of LMA was inserted. We recorded patient responses to LMA insertion as "movement" or "no movement." Test propofol concentrations started from a dosage of 4 microg/mL. Concentrations were then predetermined by a modified Dixon's up-and-down method with 0.4 microg/mL step size. MEASUREMENTS: Patient response to LMA insertion was classified as either of "no movement" or "movement." The midpoint was defined as the average concentration value of crossover (movement/no movement) response. The Cp50 value was defined as the average of the crossover midpoints in each group, and it was estimated from calculating the midpoints. MAIN RESULTS: Cp50 of the Classic, Fastrach, and ProSeal LMA insertion were 3.2+/-0.34, 4.0+/-0.22, and 4.9+/-0.20 microg/mL (mean+/-SD), respectively. CONCLUSION: Required propofol TCI concentrations for LMA insertion were significantly highest for the ProSeal, second highest for the Fastrach, and lowest for the Classic LMA.     

Target-controlled infusion of propofol for intraoperative sedation: determination of effect-site concentration and assessment of bispectral index

OBJECTIVES: To determine the effect-site concentration (Ce) of propofol, required to achieving adequate sedation. To assess the efficacy and safety of a target-controlled infusion system during monitored anaesthesia care and to evaluate the ability of bispectral index (BIS) to predict sedation level. Study design. - Prospective clinical study. PATIENTS: Women scheduled for insertion of tension-free vaginal tape under local anaesthetic infiltration. METHODS: After premedication with hydroxyzine, 1% propofol was infused using the Diprifusor system at an initial target plasma concentration (Cc) of 1 microg/ml and then adjusted by steps of 0.2 microg/ml at 5 min intervals. The level of sedation was assessed using the observer's assessment of alertness/sedation (OAA/S) scale; the objective was to obtain an OAA/S level at 4 or 3 (response to verbal stimulation). Ce of propofol and BIS were noted every 5 min. Relation between Ce or BIS and OAA/S scale was analysed by linear regression and probability of prediction (P(K)). RESULTS: Fifty patients aged 62 +/- 12 years were studied. Sedation at level 4 or 3 was observed in all patients. Ce of propofol and BIS to maintain this OAA/S score were, respectively, 1.0 +/- 0.2 microg/ml and 87 +/- 7. There was a linear relation between OAA/S scale and BIS or Ce; however, individual values demonstrate wide variability. The average of P(K) values computed for each patient for the BIS and Ce was 0.84 and 0.83, respectively. CONCLUSIONS: Target-controlled infusion of propofol provides easy and safe management of intraoperative sedation, allowing a fast and precise adjustment of the propofol concentration to the clinical response of the patient.     

Comparison of the anaesthetic requirement with target-controlled infusion of propofol to insert the laryngeal tube vs. the laryngeal mask

BACKGROUND AND OBJECTIVE: The target effect-site concentration of propofol to insert a laryngeal mask airway was recently reported as almost 5 microg mL(-1). The present study aimed to determine the target effect-site concentration with target-controlled infusion of propofol to place classical larnygeal mask airway or current laryngeal tube in adult patients. METHODS: We included 40 patients scheduled for short gynaecological and radiological procedures under general anaesthesia in a randomized, double-blind manner using the Dixon's up-and-down statistical method. Monitoring included standard cardiorespiratory monitors, and bispectral index monitoring was used for all patients. Anaesthesia was conducted with a target-controlled infusion system: Diprifusor. The initial target plasma concentration of propofol was 5 microg mL(-1), and was changed stepwise by 0.5 microg mL(-1) increments according to Dixon's up-and-down method. Criteria for acceptable insertion were: Muzi's score < or = 2, and mean arterial blood pressure, heart rate or bispectral index variation <20% the baseline values. RESULTS: Target effect-site concentration of propofol required to insert laryngeal tube was 6.3 +/- 0.3 microg mL(-1) with Dixon method and ED50 was 6.1 microg mL(-1) (5.9-6.4) with logistic regression method. In the case of larnygeal mask airway they were 7.3 +/- 0.2 microg mL(-1) (Dixon method) and 7.3 microg mL(-1) (7.1-7.5; with logistic regression) respectively (P < 0.05). ED95 (logistic regression) was 6.8 microg mL(-1) (5.9-7.6) for laryngeal tube and 7.7 microg mL(-1) (7.3-8.0) for larnygeal mask airway (P < 0.05). Haemodynamic incidents were 55% in the larnygeal mask airway group vs. 30% in the laryngeal tube group (P < 0.05). CONCLUSIONS: The target effect-site concentration of propofol for insertion of laryngeal tube was lower than for larnygeal mask airway (P < 0.05), with a consequent reduction of the propofol induced haemodynamic side-effects.     

Absence of implicit and explicit memory during propofol/remifentanil anaesthesia

BACKGROUND AND OBJECTIVE: High doses of opioid associated with low doses of hypnotic is a popular anaesthetic technique since the use of remifentanil has become widespread. This type of anaesthesia could result in a higher incidence of implicit memory. METHODS: Ten patients were anaesthetised with a target-controlled infusion of remifentanil (target concentration of 8 ng mL(-1)) combined with a target-controlled infusion of propofol with progressive stepwise increases until loss of consciousness was reached. A tape containing 20 words was then played to the patients. Bispectral index (BIS, Aspect Medical Systems, Newton, MA, USA) was continuously monitored during the whole study period. Implicit and explicit memories were tested between 2 and 4 h after recovery. RESULTS: Loss of consciousness was obtained with a mean calculated propofol plasma concentration of 1.3 +/- 0.4 microg mL(-1). At this low hypnotic concentration no implicit or explicit memory was found in the three postoperative memory tests. Median (range) BIS value during word presentation was 93 (80-98). CONCLUSIONS: In our group of young American Society of Anesthesiologists (ASA) I/II patients, no explicit or implicit memory was found when the calculated concentration of propofol combined with a high concentration of remifentanil was maintained at the level associated with loss of consciousness with high BIS values.     

Brain tumors may alter the relationship between bispectral index values and propofol concentrations during induction of anesthesia

STUDY OBJECTIVE: To compare propofol-predicted effect-site concentrations (PropCe) and bispectral index (BIS) of the electroencephalogram during induction of anesthesia in patients with small brain tumors and to analyze BIS and PropCe at loss of consciousness (LOC). DESIGN: Prospective investigation. SETTING: Operating theater of a university hospital. PATIENTS: 26 ASA physical status I and II patients, 13 of whom were scheduled for nontumor spinal surgeries, and the other 13, for brain surgery for small brain tumor removal. INTERVENTIONS: Anesthesia was induced with a propofol 1% constant infusion rate of 200 mL/h until LOC. MEASUREMENTS: BIS, PropCe, heart rate, and mean arterial pressure were analyzed at the beginning of the propofol infusion and every 30 seconds during induction. MAIN RESULTS: The BIS values were significantly higher in patients with brain tumors in the period from 150 to 210 seconds, with PropCe similar to patients without brain tumors. Loss of consciousness occurred 3.6 +/- 0.8 minutes in patients without brain tumors and 3.9 +/- 0.7 minutes in patients with brain tumors. No differences were observed between groups in the time to LOC (3.6 +/- 0.8 in group 1 vs 3.9 +/- 0.7 in group 2) or in BIS at LOC (48.7 +/- 11.4 in group 1 vs 58.6 +/- 21.7 in group 2). CONCLUSIONS: For similar propofol concentrations, patients with small brain tumors show higher BIS values on induction of anesthesia with propofol.     

Target-controlled infusion of propofol induction with or without plasma concentration constraint in high-risk adult patients undergoing cardiac surgery

BACKGROUND: Calculated plasma (Cp) and calculated effect site concentrations (Ce) of propofol associated with loss of consciousness (LOC) have been studied in young healthy patients. The aim of the study was to evaluate the calculated propofol concentrations required to induce LOC in ASA III adult patients undergoing cardiac surgery using a smooth target controlled infusion of propofol. METHODS: After informed consent, 44 patients were premedicated with 0.5 mg alprazolam orally. Propofol TCI using the pharmacokinetic set of Marsh et al. incorporated in the Diprifusor (ThalfKeo of 2.6 min) was used. Propofol Ce was progressively increased by 0.5 micro g/ml until LOC was obtained. The constraint on the maximum gradient between Cp and Ce was either 1 micro g/ml in group 1 or not limited in group 2. Hemodynamic variations were assessed. RESULTS: Mean preoperative left ventricular ejection fractions were 44 +/- 15.4% and 56 +/- 11.4% in groups 1 and 2, respectively (P < 0.01). At LOC, mean Cp was 1.9 micro g/ml in both groups but mean Ce was 1.08 +/- 0.31 and 1.43 +/- 0.42 micro g/ml in groups 1 and 2, respectively (P < 0.01). The mean induction time was 12.8 +/- 7.1 min in group 1 and 8.5 +/- 2.7 min in group 2 (P < 0.05). No episode of hypotension has been observed in either group. CONCLUSION: In ASA III patients undergoing cardiac surgery, smooth propofol TCI induction, using the pharmacokinetic set of Marsh et al. incorporated in the Diprifusor, is associated with LOC at a low mean calculated plasma concentration of 1.9 micro g/ml and good hemodynamic stability.     

Target-controlled infusion of propofol for fibreoptic intubation

BACKGROUND AND OBJECTIVE: In a retrospective study, we examined the suitability of a departmental clinical protocol for anaesthesia induction with target-controlled infusion of propofol developed for fibreoptic intubation in spontaneously breathing patients scheduled for outpatient oral surgery at the dental clinic of the Vienna University Hospital. METHODS: Propofol was administered using target-controlled infusion (Diprifusor) at increasing target plasma concentrations starting at 2.5 microg mL(-1). After 10 min, an intravenous dose of alfentanil (5-10 microg kg(-1)) was given for pain reduction. After a further 2 min, the patient was evaluated for response to auditory stimulation. If unresponsive, fibreoptic intubation was performed, otherwise the target concentration was increased by 0.2 microg mL(-1) every 2 min until non-responsiveness was attained. RESULTS: Tracheal intubation was successful in all patients without any haemodynamic instability. However, one patient required facemask ventilation for 2 min. No patient was aware of intubation. The plasma concentration required for non-responsiveness was 2.8 +/- 0.4 microg mL(-1) (mean +/- SD). CONCLUSIONS: When using a target-controlled infusion of propofol, fibreoptic intubation can be performed with complete amnesia of the procedure for the patient. However, assisted ventilation of the lungs may be necessary as spontaneous ventilation may cease.     

卵巢周期对患者异丙酚镇静效应的影响

目的 评价卵巢周期对患者异丙酚镇静效应的影响.方法 择期拟行妇科腹腔镜手术患者加例,ASA分级Ⅰ或Ⅱ级,年龄20.加岁,体重指数20～25 kg/m2,根据孕酮水平分为卵泡期组(F组,血清孕酮浓度0.31～1.52 ng/ml)和黄体期组(L组,血清孕酮浓度5.16～18.56 ng/ml),每组20例.麻醉诱导时靶控输注异丙酚,初始血浆靶浓度2 μg/ml,达到预期血浆靶浓度后每隔30 s递增0.5μg/ml直至患者意识消失及BIS值降至50.记录患者意识消失时的BIS值、异丙酚血浆靶浓度,记录BIS值降至50时的异丙酚血浆靶浓度.结果 与L组比较,F组意识消失时和BIS值降至50时的异丙酚血浆靶浓度升高(P＜0.05或0.01),意识消失时的BIS值差异无统计学意义(P＞0.05).结论 卵巢周期可影响异丙酚的镇静效应,表现为卵泡期的镇静效应低于黄体期.

Abstract：

Objective To investigate the effect of ovarian cycle on the sedative effect of propofol in patients. Methods Forty ASA Ⅰ or Ⅱ patients, aged 20-40 yr, with body mass index 20-25 kg/m2 , scheduled for elective gynecologic laparoscopic surgery, were divided into 2 groups according to the progesterone level ( n = 20 each): follicular phase group (group F, serum progesterone concentration 0.31-1.52 ng/ml) and luteal phase group (group L, serum progesterone concentration 5.16-18.56 ng/ml). Anesthesia was induced with target-controlled infusion (TCI) of propofol and iv injection of fentanyl and cisatracurium. The initial target plasma concentration (Cp) of propofol was set at 2 μg/ml, after the Cp reached the predetermined level, the Cp increased by 0.5 μg/ml every 30 s until the patients lost consciousness and BIS value was decreased to 50. The BIS value and Cp of propofol was recorded when the patients lost consciousness. The Cp of propofol was also recorded when BIS value was decreased to 50. The patients were tracheal intubated and mechanically ventilated. Anesthesia was maintained with TCI of propofol combined with remifentanil. BIS value was maintained at 45-55 by adjusting the Cp of propofol. Results The Cps of propofol were significantly higher when the patients lost consciousness and when BIS value was decreased to 50 in group F than in group L ( P ＜ 0.05 or 0.01) . There was no significant difference in BIS value when the patients lost consciousness between the two groups (P ＞ 0.05). Conclusion Ovarian cycle can affect the sedative effect of propofol in patients, which shows that the sedative effect during the follicular phase is lower than that during the luteal phase.     

Effects of fentanyl, alfentanil, remifentanil and sufentanil on loss of consciousness and bispectral index during propofol induction of anaesthesia

The bispectral index (BIS) and a sedation score were used todetermine and compare the effect of propofol in the presenceof fentanyl, alfentanil, remifentanil and sufentanil. Seventy-fivenon-premedicated patients were assigned randomly into five groups(15 in each) to receive fentanyl, alfentanil, remifentanil,sufentanil or placebo. Opioids were administered using a target-controlledinfusion device, to obtain the following predicted effect-siteconcentrations: fentanyl, 1.5 ng ml^–1; alfentanil, 100ng ml^–1; remifentanil, 6 ng ml^–1; and sufentanil,0.2 ng ml^–1. After this, a target-controlled infusionof propofol (Diprifusor) was started to increase concentrationgradually, to achieve predicted effect-site concentrations of1, 2, and 4 µg ml^–1. At baseline and at each successivetarget effect-site concentration of propofol, the BIS, sedationscore and haemodynamic variables were recorded. At the momentof loss of consciousness (LOC), the BIS and the effect-siteconcentration of propofol were noted. The relationship betweenpropofol effect-site concentration and BIS was preserved withor without opioids. In the presence of an opioid, LOC occurredat a lower effect-site concentration of propofol and at a higherBIS₅₀ (i.e. the BIS value associated with 50% probability ofLOC), compared with placebo. Although clinically the hypnoticeffect of propofol is enhanced by analgesic concentrations ofµ-agonist opioids, the BIS does not show this increasedhypnotic effect. Br J Anaesth 2001; 86: 523–7     

Effect site concentrations of remifentanil maintaining cardiovascular homeostasis in response to surgical stimuli during bispectral index guided propofol anestesia in seriously obese patients

AIM: The aim of this prospective study was to determine the effect site concentrations of remifentanil maintaining cardiovascular homeostasis in response to surgical stimuli during bispectral index (BIS) guided propofol anesthesia in seriously obese patients. METHODS: Twenty-two patients, female/male 15/7, ASA physical status II - III, aged 29-69 years, body mass index (BMI) 54.5+/-12, undergoing major open bariatric surgery, were enrolled to receive a propofol-remifentanil total intravenous anesthesia. All patients were intubated by using a flexible fiberoptic bronchoscopic technique facilitated by a target controlled effect site concentration of remifentanil set at 2.5 ng/mL. After endotracheal intubation, anesthesia was started with a target controlled infusion of propofol initially set at 6 microg/mL, then adjusted to maintain a BIS value between 40 and 50. The mean effect site concentration of remifentanil was recorded at different intervals time during surgery: skin incision-opening of peritoneum (T1), bowel resection (T2), cholecystojejunal anastomosis (T3), ileojejunal anastomosis (T4), closing of peritoneum (T5). RESULTS: The mean plasma concentrations of propofol required to maintain a BIS value between 40 and 50 were 4+/-0.55, 3.8+/-0.64, 3.8+/- 0.63, 3.8+/-0.65 and 3.8+/-0.63 microg/mL at T1, T2, T3, T4 and T5 interval time, respectively. The mean values of remifentanil target effect site concentration were 5.2+/-1.3, 7.7+/-1.7, 9.1+/-1.8, 9.7+/- 2.2 and 9.9+/-2.5 ng/mL at T1, T2, T3, T4 and T5 interval time. CONCLUSIONS: This study suggests that tolerance to remifentanil infusion is profound and develops very rapidly in morbidly obese patients submitted to open bariatric surgery during BIS guided propofol anesthesia. The administration of opiates during anesthesia based on target-controlled infusion should include corrections for the development of tolerance.     

Absence of explicit and implicit memory in unconscious patients using a TCI of propofol

BACKGROUND: Episodes of implicit memory have been described during propofol anaesthesia. It remains unclear whether implicit memory is caused by short periods of awareness or occurs in an unconscious subject. METHODS: Sixty patients were randomized in an experimental group (EG), a control group (CG) and a reference group (RG). Loss of consciousness (LOC) was obtained by progressive stepwise increases of propofol using a target-controlled infusion device (Diprifusor, Alaris Medical Systems, San Diego, CA). A tape containing 20 words was played to the patients in the CG before the start of anaesthesia and to the patients in the EG at a constant calculated concentration of propofol associated with LOC. The tape was not played to the patients in the RG. Three memory tests were performed postoperatively. RESULTS: Explicit and implicit memories were evidenced in the CG but not in the EG. CONCLUSION: In our group of young ASA I/II patients, in the absence of any noxious stimulus, no implicit or explicit memory was found when the calculated concentration of propofol using a Diprifusor was maintained at the level associated with LOC.     

BIS - AAI and clinical measures during propofol target controlled infusion with Schnider's pharmacokinetic model

AIM: The A-line autoregressive index (AAI) and the Bispectral Index Score (BIS) are two commercially available indexes of anesthetic depth widely used in clinical practice. The aim of the current study was to compare the accuracy of AAI, BIS, Schnider's predicted effect-site concentration of propofol (Ce propofol) to assess depth of anesthesia. METHODS: Forty-four patients scheduled for major elective abdominal surgery received target effect-site controlled infusion of propofol. Target effect-site (Ce propofol) was started at 1.5 mug/mL and increased every 4 min by 1.0 microg/mL until 5.5 microg/mL were achieved. At every step sedation level was estimated, using AAI, BIS, Observer's Assessment of Alertness/Sedation scale (OAA/S), loss of eyelash reflex and Ce propofol. RESULTS: We enrolled 44 patients, 20 males and 24 females, ASA I/II 18/26, 48+/-10 years, 68.2+/-9 kg, 165+/-7.1 cm, body mass index (BMI) 25+/-3.5. At increasing Ce propofol BIS-AAI values decreased progressively (BIS range 97-38) (AAI range 97-17). Values of BIS < or = 50, of AAI < or = 48 and of Ce propofol > or = 5.1 resulted in OAA/S=0, while values of BIS < or = 62, AAI < or = 53 and Ce propofol < or = 3.5 resulted in OAA/S=2. Loss of eyelash reflex occurred when values were BIS < or = 64 and AAI < or 61. CONCLUSION: BIS, AAI, propofol site effect concentration revealed information on sedation level and consciousness but no gold standard yet exists because of consistent overlap between 'conscious' and 'not conscious' states.     

Narcotrend,bispectral index,and classical electroencephalogram variables during emergence from propofol/remifentanil anesthesia

The aim of this study was to investigate modern and classical electroencephalographic (EEG) variables in response to remifentanil and propofol infusions. We hypothesized that modern EEG variables may indicate the effects of propofol but not of remifentanil. Twenty-five patients were included in the study after the end of elective spine surgery without any surgical stimulation. Baseline values were defined with remifentanil 0.3 microg. kg(-1). min(-1) and target-controlled infusion of propofol 3.0 microg/mL. EEG changes were evaluated 1, 3, 5, 7, and 9 min after the stop of remifentanil infusion, followed by a step-by-step reduction (0.2 microg/mL) every 3 min of target-controlled infusion propofol. Narcotrend (NT; classifying EEG stages from awake to deep anesthesia), bispectral index (BIS), EEG spectral frequency bands (%), 50% (Median) and 95% percentiles (spectral edge frequency), mean arterial blood pressure, heart rate, and oxygen saturation were detected at every time point. The end of remifentanil application resulted in significant increases in %alpha, spectral edge frequency, mean arterial blood pressure, and %theta and decreases in %delta (P < 0.05). NT, BIS, Median, heart rate, and oxygen saturation were unchanged. Decreases in propofol concentration were associated with statistically significant increases in NT and BIS (P < 0.05). Thus, the sedative-hypnotic component of propofol could be estimated by modern EEG variables (NT and BIS), whereas the analgesic component provided by remifentanil was not indicated. However, during conditions without surgical stimulation, neither NT nor BIS provided an adequate assessment of the depth of anesthesia when a remifentanil infusion was used. IMPLICATIONS: We investigated modern and classical electroencephalographic (EEG) variables during emergence from propofol/remifentanil anesthesia. Modern EEG variables indicate changes of infusion in propofol, but not in remifentanil. Thus, modern EEG variables did not provide an adequate assessment of depth of anesthesia when remifentanil was used.     

BIS监测异丙酚复合瑞芬太尼全麻患儿麻醉深度的准确性

目的 评价脑电双频谱指数(BIS)监测异丙酚复合瑞芬太尼全麻患儿麻醉深度的准确性.方法 择期手术患儿60例,ASA Ⅰ或Ⅱ级,年龄3～8岁,体重14～40kg,随机分为4组(n=15),人室后开放手背静脉,稳定5 min.C组静脉输注0.9%生理盐水0.2 ml·kg-1·h-1;R1组、R2组和R3组分别静脉输注瑞芬太尼0.1、0.3或0.5 μg·kg-1·min-1,瑞芬太尼或生理盐水输注10 min开始靶控输注异丙酚,起始效应室浓度为1 μg/ml,逐渐递增至2、3、4μg/ml.分别于稳定5min、瑞芬太尼静脉输注10min、异丙酚效应室浓度达到l、2、3、4μg/ml稳定1 min及意识消失时记录BIS和警觉,镇静(OAA/S)评分;记录意识消失时间.采用logistic回归法计算意识消失时的BIS50、BIS95和意识消失时异丙酚的EC50、EC95.BIS与OAA/S评分、异丙酚效应室浓度作直线相关分析.结果 C组、R1.组、R2组和R3组BIS与OAA/S评分均呈正相关,r分别为0.89、0.90、0.87、0.82(P<0.05);BIS与异丙酚效应室浓度均呈负相关,r分别为-0.87、-0.90、-0.87、-0.92(P<0.05);与C组比较,其余3组患儿意识消失时异丙酚效应室浓度降低,意识消失时间缩短,R2组和R3组意识消失时BIS升高,BIS50和BIS95升高,异丙酚EC50和EC95降低(P<0.05);与R1组比较,R2组BIS50和BIS95升高,R3组异丙酚EC50和EC95降低(P<0.05).结论 瑞芬太尼复合异丙酚麻醉下,采用BIS监测患儿麻醉深度存在一定局限性.     

Effects of epidural anesthesia with 0.2% and 1% ropivacaine on predicted propofol concentrations and bispectral index values at three clinical end points

STUDY OBJECTIVE: To compare the effects of 0.2% epidural ropivacaine and those of 1% epidural ropivacaine on predicted propofol concentrations and bispectral index scores (BISs) at three clinical end points. DESIGN: Randomized double-blind study. SETTING: University hospital. PATIENTS: Thirty-five (35) ASA physical status I and II patients scheduled for elective surgery of the lower abdomen. INTERVENTIONS: Patients were randomly divided into 2 groups to receive epidurally 8 mL of 0.2% or 1% ropivacaine followed by the same solution at a rate of 6 mL/h. MEASUREMENTS: Twenty minutes after starting ropivacaine, a target-controlled infusion of propofol was started to provide a predicted blood concentration of 3 microg/mL; it increased by 0.5 microg/mL every 60 seconds until all 3 clinical end points were reached, as follows: P1, when patients lost consciousness; P2, when patients failed to show pupillary dilation and skin vasomotor reflex to transcutaneous electric stimulation applied to the upper level of loss of cold sensation; and P3, when patients failed to show pupillary dilation and skin vasomotor reflex to transcutaneous electric stimulation applied to C5. MAIN RESULTS: The effective concentration 50 values for both predicted blood and effect-site propofol concentrations were significantly larger in the 0.2% group than in the 1% group at all end points. The BIS at every end point was significantly smaller in the 0.2% group than in the 1% group. CONCLUSIONS: During combined epidural-propofol anesthesia, unconsciousness and lack of response to noxious stimulation occurred at lower predicted concentrations with 1% epidural ropivacaine than with 0.2% epidural ropivacaine. The results also suggest that the BIS may not be a good indicator when propofol anesthesia is combined with epidural anesthesia.     

Narcotrend monitoring allows faster emergence and a reduction of drug consumption in propofol-remifentanil anesthesia

BACKGROUND: The Narcotrend is a new electroencephalographic monitor designed to measure depth of anesthesia, based on a six-letter classification from A (awake) to F (increasing burst suppression) including 14 substages. This study was designed to investigate the impact of Narcotrend monitoring on recovery times and propofol consumption in comparison to Bispectral Index (BIS) monitoring or standard anesthetic practice. METHODS: With institutional review board approval and written informed consent, 120 adult patients scheduled to undergo minor orthopedic surgery were randomized to receive a propofol-remifentanil anesthetic controlled by Narcotrend, by BIS(R), or solely by clinical parameters. Anesthesia was induced with 0.4 micro x kg-1 x min-1 remifentanil and a propofol target-controlled infusion at 3.5 microg/ml. After intubation, remifentanil was reduced to 0.2 micro x kg-1 x min-1, whereas the propofol infusion was adjusted according to clinical parameters or to the following target values: during maintenance to D(0) (Narcotrend) or 50 (BIS); 15 min before the end of surgery to C(1) (Narcotrend) or 60 (BIS). Recovery times were recorded by a blinded investigator, and average normalized propofol consumption was calculated from induction and maintenance doses. RESULTS: The groups were comparable for demographic data, duration of anesthesia, and mean remifentanil dosages. Compared with standard practice, patients with Narcotrend or BIS monitoring needed significantly less propofol (standard practice, 6.8 +/- 1.2 mg x kg-1 x h-1 vs. Narcotrend, 4.5 +/- 1.1 mg x kg-1 x h-1 or BIS(R), 4.8 +/- 1.0 mg x kg-1 x h-1; P < 0.001), opened their eyes earlier (9.3 +/- 5.2 vs. 3.4 +/- 2.2 or 3.5 +/- 2.9 min), and were extubated sooner (9.7 +/- 5.3 vs. 3.7 +/- 2.2 or 4.1 +/- 2.9 min). CONCLUSIONS: The results indicate that Narcotrend and BIS monitoring are equally effective to facilitate a significant reduction of recovery times and propofol consumption when used for guidance of propofol titration during a propofol-remifentanil anesthetic.     

Does cerebral monitoring improve ophthalmic surgical operating conditions during propofol-induced sedation?

Sudden movements from over-sedation during ophthalmic surgery can be detrimental to the eye. Bispectral index (BIS) and middle-latency auditory-evoked potentials (Alaris AEP index, AAI) were reported to be accurate indicators for the level of sedation and loss of consciousness. We assessed these monitors during sedation with special emphasis on preventing over-sedation. One-hundred patients scheduled for elective eye surgery were sedated with target-controlled propofol infusion and randomly allocated to BIS-guided, AAI-guided, BIS/AAI-guided, or clinically guided groups (n = 25 each). The initial target concentration was 0.5 microg x mL(-1) in patients >70 yr and 1.0 microg x mL(-1) in all other patients. The concentration was increased every 3 min by 0.1 or 0.2 microg x mL(-1), respectively until the patient had reached a BIS value of 75 (range 70-90) or an AAI of 40 (range 35-60). The surgeon who was blinded to group allocation assessed treatment quality after the procedure. Sedation was converted into general anesthesia in four patients because of excessive head movements. BIS was out of range 7% of the time vs 58% for AAI. No significant differences in treatment quality were observed among the four groups. We conclude that propofol sedation, guided by BIS or AAI monitoring, did not enhance ophthalmic surgical operating conditions over sedation guided by clinical observation only.