Target Effect-site Concentration Research Articles

Comparison of pharmacodynamics and circulatory function of domestic and imported rocuronium

Objective To compare the phaimacodynamics and circulatory function of domestic and imported rocuronium. Methods This is a five center study of rocuronium. Two hundred and ten ASA Ⅰ or Ⅱ patients aged 18-65 yr undergoing elective surgery under general anesthesia were randomly divided into 2 groups (n = 105 each): domestic rocuronium group (group Ⅰ ) and imported rocuronium group (group Ⅱ ) . Anesthesia was induced and maintained with TCI of propofol (target plasma concentration = 3 mg/L) and remifentanil (target effect-site concentration = 2-4 μg/L) . Tracheal intubation was facilitated with intravenous rocuronium 0.6 mg/kg. The N-M function was assessed by accelerography (TOF-Watch(R) SX, Organon, Netherlands) using TOF stimulation of ulnar nerve. Onset time, clinical duration, 75% recovery time,recovery indexes, the extent of maximal NM blockade and intubation conditions (ease of laryngoscopy, position of vocal cords and airway reaction) were monitored and recorded. BP and HR were also recorded. Results There were no significant differences in the onset time, clinical duration, recovery indexes, the extent of maximal N-M blockade, the intubation conditions, BP, HR and adverse reactions between groups Ⅰ and Ⅱ ( P ＞ 0.05) . The 75% recovery time was significantly longer in group Ⅱ than in group Ⅰ (P ＜ 0.05＝. Conclusion The pharmacodynamics of domestic and imported rocuronium is comparable. The two drugs have no adverse effect on the circulatory function. Key words: Androstanols; Neuromuscular blockade; Dose-response relationship, drug; Blood circulation

Effect of dexmedetomidine on median effective target effect-site concentration of sufentanil inhibiting body movement evoked by skin incision in patients undergoing bilateral subtotal thyroidectomy

Objective To investigate the effect of dexmedetomidine on median effective target effect-site concentration ( EC50) of sufentanil inhibiting body movement evoked by skin incision in patients undergoing bilateral subtotal thyroidectomy. Methods Thirty-nine ASA I or II patients of both sexes aged 20-64 yr with a body mass index of 20-25 kg/m2 undergoing bilateral subtotal thyroidectomy were randomly divided into 2 groups: control group (group C) and dexmedetomidine group (group D). The patients were premedicated with intramuscular phenobarbital 0.1 g and scopolamine 0.3 mg. In group D dexmedetomidine 0.6 μg/kg was injected iv over 10 min at S min before induction of anesthesia. Anesthesia was induced with target-controlled infusion (TCI) of propofol and sufentanil. The target plasma concentration of propofol was set at 3.0 μg/ml which was maintained until the end of operation. TCI of sufentanil was started at 10 min after initiation of propofol TCI. The initial target effect-site concentration was set at 0.20 ng/ml and decreased/increased by 20% in the next patient according to whether the patient's body moved or not within 1 min after skin incision. Laryngeal mask airway was inserted at 3 min after initiation of sufentanil TCI. Spontaneous breathing was maintained. Skin incision was made at 10 min after initiation of sufentanil TCI. The EC50 and 95% confidence interval (CI) of sufentanil inhibiting skin incision-evoked body movement were calculated with sequential method. Results EC50, of sufentanil was 0.1148 ng/ml (95% CI 0.1055-0.1249 ng/ml) in group D and 0.1454 ng/ml (95% CI 0.1339-0.1580 ng/ml) in group C, and was significantly lower in group D than in group C. Conclusion Dexmedetomidine 0.6 μg/kg infused iv before operation can reduce the EC50 of sufentanil inhibiting body movement evoked by skin incision in patients undergoing bilateral subtotal thyroidectomy. Key words: Dexmedetomidine; Sufentanil; Drug delivery systems; Dose-response relationship, drug; Thyroidectomy

Feasibility of different doses of dexmedetomidine required to prevent sufentanil-induced cough during anesthesia induction

Objective To investigate the feasibility of different doses of dexmedetomidine required to prevent sufentanil-induced cough during anesthesia induction. Methods Two hundred and forty ASA Ⅰ or Ⅱ patients, aged 18-55 yr, weighing 45-78 kg, undergoing elective gynecological operations under general anaesthesia, were randomly divided into 4 groups ( n = 60 each) : Ⅰ -Ⅳ groups. Ⅱ -Ⅳ groups received iv infusion of dexmedetomidine 0.10, 0.25 and 0.50 fig/kg at a rate of 0.05 μg·kg-1·min-1 respectively before anesthesia induction. Anesthesia was induced with target-controlled infusion of propofol (target effect-site concentration 5 μg/ml) , when the BIS value reached 55, iv sufentanil 0.5 fig/kg was injected over 3 s. The occurrence and degree of cough were recorded within 1 min after sufentanil injection. Tracheal intubation was facilitated with succinylcholine 1-2 mg/kg after the observation. The adverse cardiovascular events (severe sinus bradycardia, hypotension) were also record ed from the start of dexmedetomidine infusion to 1 min after intubation. Results The incidences of cough were 25 % , 7 % , 7 % and 5 % , incidences of severe sinus bradycardia 0, 3 % , 15 % and 25 % , and incidences of hypotension 5% , 7% , 8% and 8% in Ⅰ - Ⅳ groups respectively. Compared with group Ⅰ , the incidences of cough were significantly decreased in Ⅱ - Ⅳ groups, while the incidences of severe sinus bradycardia increased in Ⅲ -Ⅳ groups (P ＜ 0.01) . There was no significant difference in the incidences of cough among Ⅱ - Ⅲ groups and in the degree of cough among the four groups (P ＞ 0.05). Conclusion Intravenous dexmedetomidine 0.10 μg/kg can be used to prevent sufentanil-induced cough during anesthesia induction. Key words: Dexmedetomidine; Sufentanil; Cough

Half-effective target effect-site concentration of sufentanil inhibiting urethroscope insertion response when combined with propofol by target-controlled infusion in elderly patients undergoing transurethral resection of prostate

Objective To determine the half-effective target effect-site concentration (EC50 ) of sufentanil inhibiting the urethroscope insertion response when combined with propofol by target-controlled infusion (TCI) in the elderly patients undergoing transurethral resection of prostate (TURP) . Methods Twenty-two ASA Ⅰ- Ⅲ patients, aged 65 -79 yr, weighing 47-81 kg, undergoing TURP, were enrolled in the study. Anesthesia was performed with TCI of propofol and sufentanil. The target plasma concentration of propofol was 4 μg/ml. The target effect-site concentration of sufentanil was determined by up-and-down sequential trial. The initial target effect-site concentration of sufentanil was 0.3 ng/ml and the ratio of the target concentrations between the two consecutive patients was 1.1. The ECW and 95% confidence interval of sufentanil required to inhibit the response to urethroscope insertion were calculated. Results The EC50 of sufentanil required to inhibit the urethroscope insertion response was 0.23 ng/ml (95% confidence interval 0.12-0.44 ng/ml). Conclusion When combined with propofol by TCI (target plasma concentration 4 μg/ml), the EC50 of sufentanil inhibiting the response to urethroscope insertion is 0,23 ng/ml in the elderly patients undergoing TURP. Key words: Piperidines; Propofol; Dose-response relationship, drug; Drug delivery systems

Effect of intraoperative wake-up test on postoperative delirium in patients undergoing scoliosis surgery under analgesia with sufentanil

Objective To investigate the effect of the intraoperative wake-up test on the postoperative delirium in patients undergoing scoliosis operation under analgesia with sufentanil. Methods Sixty ASA Ⅰ or Ⅱ patients , aged 12-60 yr, scheduled for scoliosis surgery, were randomly divided into 2 groups ( n = 30 each) : control group (group C) and intraoperative wake-up test group (group W) . The intraoperative wake-up test was not performed during operation in group C. Anesthesia was induced with target-controlled infusion of sufentanil with the target effect-site concentration set at 0.5 ng/ml and iv injection of propofol 1-2 nig/kg. As soon as the patients lost consciousness, tracheal intubation was facilitated with 0.15 mg/kg cisatracurium besylate. The patients were mechanically ventilated. Anesthesia was maintained with target-controlled inhalation of sevoflurane (target end-tidal concentration 0. 8%-1. 5%), target-controlled infusion of sufentanil (target effect-site concentration 0.2-0.3 ng/ml) and iv infusion of cisatracurium besylate 0.1 mg- kg-1·h-1 . In group W, the patients underwent the intraoperative wake-up test. Postoperative analgesia was provided with sufentanil. The occurrence of intraoperative awareness and postoperative delirium was recorded. Results No significant difference was found in the incidences of intraoperative awareness and postoperative delirium between the two groups. Conclusion The intraoperative wake-up test is not the risk factor for postoperative delirium in patients undergoing scoliosis surgery under analgesia with sufentanil, and inhibition of perioperative pain and intraoperative awareness by analgesia with sufentanil may be involved in the mechanism. Key words: Sufentanil; Postoperative complications; Delirium; Scoliosis; Wake-up tests

Effects of different target effect-site concentrations of remifentanil on the sedative effect of propofol

Objective To investigate the effects of different target effect-site concentrations (Ces) of remifentanil on the sedative effect of propofol. Methods Fifty ASA Ⅰ or Ⅱ patients aged 20-55 yr weighing 48-86 kg with body mass index ＜ 30 kg/m2 were randomly divided into 5 groups ( n = 10 each) . Anesthesia was induced with TCI of remifentanil (Ce = 0, 2, 4, 6 and 8 ng/ml in groups R0-R4 respectively) and propofol. The initial Ce of propofol was 2.0 μg/ml in the 5 groups, and then the Ce of propofol increased by 0.5 μg/ml every 1 min until BIS value decreased to 50. BIS value and Ce of propofol were recorded as the patient lost consciousness. The effect-site concentration and consumption of propofol and the time required were recorded when BIS value decreased to 50.Results BIS value was significantly increased, while the effect-site concentration of propofol was significantly decreased as the patient lost consciousness, and the effect-site concentration and consumption of propofol were significantly decreased and the time required was shortened when BIS value decreased to 50 in R2-R4 groups compared with group R0 (P ＜ 0.05 or 0.01) . Conclusion The sedative effect of propofol can be enhanced when the Ce of remifentanil reaches 4 ng/ml, and the effects are comparable when the Ce of remifentanil reaches 4, 6 and 8 ng/ml. Key words: Piperidines; Propofol; Conscious sedation; Drug delivery system

Remifentanil does not impair left ventricular systolic and diastolic function in young healthy patients

Experimental studies and investigations in patients with cardiac diseases suggest that opioids at clinical concentrations have no important direct effect on myocardial relaxation and contractility. In vivo data on the effect of remifentanil on myocardial function in humans are scarce. This study aimed to investigate the effects of remifentanil on left ventricular (LV) function in young healthy humans by transthoracic echocardiography (TTE). We hypothesized that remifentanil does not impair systolic, diastolic LV function, or both. Twelve individuals (aged 18-48 yr) without any history or signs of cardiovascular disease and undergoing minor surgical procedures under general anaesthesia were studied. Echocardiographic examinations were performed in the spontaneously breathing subjects before (baseline) and during administration of remifentanil at a target effect-site concentration of 2 ng ml(-1) by target-controlled infusion. Analysis of systolic function focused on fractional area change (FAC). Analysis of diastolic function focused on peak early diastolic velocity of the mitral annulus (e') and on transmitral peak flow velocity (E). Remifentanil infusion at a target concentration of 2 ng ml(-1) did not affect heart rate or arterial pressure. There was no evidence of systolic or diastolic dysfunction during remifentanil infusion, as the echocardiographic measure of systolic function (FAC) was similar to baseline, and measures of diastolic function remained unchanged (e') or improved slightly (E). Continuous infusion of remifentanil in a clinically relevant concentration did not affect systolic and diastolic LV function in young healthy subjects during spontaneous breathing as indicated by TTE.

Bispectral index is related to the spread of spinal sensory block in patients with combined spinal and general anaesthesia

BackgroundA relationship between the depth of sedation as measured by the bispectral index (BIS) and spinal sensory block height in patients with light to no additional sedation has been described previously. The present study was designed to investigate the hypothesis that BIS values closely correlate with the spread of spinal sensory block in patients deeply sedated with an i.v. target-controlled infusion of propofol. MethodsSubjects comprised 100 patients aged 20–64 yr and undergoing arthroscopic knee surgery. Patients were given spinal anaesthesia with bupivacaine 0.5% (3 ml). Propofol was administered to achieve a target effect-site concentration of 3.0 μg ml−1. The relationship between the spinal sensory level at 15 min after spinal anaesthesia and BIS values during 1–5, 6–10, 11–15, and 16–20 min time intervals after the estimated effect-site concentration reached 3.0 μg ml−1 was evaluated. ResultsThe sensory level of spinal analgesia significantly and strongly correlated with BIS values during each time period after the estimated effect-site concentration remained at 3.0 μg ml−1 (P<0.0001). The correlation coefficient values were 0.8 during 1–5 min, 0.844 during 6–10 min, 0.801 during 11–15 min, and 0.804 during 16–20 min time periods. ConclusionsWe demonstrated that BIS values significantly correlate with the level of spinal sensory block under deep sedation with propofol. The depth of sedation induced by spinal anaesthesia depends on the spread of spinal sensory block.

Effect of chronic alcohol intake on half- effective target effect- site concentration of propofol required for loss of consciousness

Objective To evaluate the effect of chronic alcohol intake on the sedative potency of propofol through investigating the effect of chronic alcohol intake on the half-effective target effect-site concentration ( EC50 )of propofol required for loss of consciousness in patients. Methods Fifty male ASA Ⅰ or Ⅱ patients, aged 25-60 yr, weighing 50-80 kg, scheduled for elective surgery, were divided into 2 groups according to the history of chronic alcoholic intake ( n = 25 each): control group (alcoholic intake per day ＜ 25 g) and chronic alcoholic group (alcoholic intake per day＞45 g, lasting for 2 yr or more). The EC50 and 95% confidence interval (CI)were determined by up-and-down sequential method. The initial target effect-site concentration was 2 μg/nl in chronic alcoholic group and 1.5μg/ml in control group, and the ratio between the two successive concentrations was 1.05. Loss of consciousness was defined as loss of response to verbal command and eyelash stimulation. Results The EC50 of propofol that produced loss of consciousness was 3.92 (95 % CI 3.56-4.63 ) μg/ml in chronic alcoholic group and 2.73 (95%CI 2.26-3.31)μg/ml in control group. The EC50 of propofol was significantly higher in chronic alcoholic group than in control group ( P ＜ 0.05). Conclusion Chronic alcohol intake can increase the EC50 of propofol required to induce loss of consciousness and reduce sedative potency in patients. Key words: Alcohol drinking; Propofol; Dose-response relationship, drug; Drug delivery system

The target concentration of remifentanil to suppress the hemodynamic response to endotracheal intubation during inhalational induction with desflurane

BackgroundAnesthesia induction with desflurane is troublesome because of the frequent sympathetic hyperactivity during desflurane administration. We thought that a low concentration of desflurane combined with a target-controlled infusion (TCI) of remifentanil would eliminate the desflurane-related complications and provide hemodynamic stability during desflurane induction. An up-and-down study was planned to find the target effect-site concentration of remifentanil to block the hemodynamic response to endotracheal intubation, the highest level of stimulus, during anesthesia induction with administering desflurane at 1 MAC.MethodsRemifentanil TCI was initiated before desflurane administration. When the preset target was achieved, spontaneous inhalation of desflurane 1 MAC was performed until the patients became unconscious. Laryngoscopic tracheal intubation was facilitated with rocuronium injection. The starting concentration of remifentanil and the test space were 5 and 1 ng/ml, respectively. The criteria for up-and-down was a 20% increase of the mean arterial pressure or heart rate after intubation. The median effective concentration (EC50) of remifentanil was calculated from 6 independent pairs. The complications related with remifentanil and desflurane were assessed during the study.ResultsWe studied 20 patients using 2-5 ng/ml of the effect-site concentrations of remifentanil. The EC50 of remifentanil was 3.7 ng/ml. Loss of consciousness was achieved at 125 ± 22 s after desflurane inhalation and this was irrespective of the combined remifentanil concentrations. Any remifentanil-related complication was not observed. Transient cough was seen in one patient who received 2 ng/ml of remifentanil.ConclusionsWe demonstrated that uncomplicated induction with desflurane was possible by the use of target-controlled remifentanil. The EC50 of remifentanil to block the hemodynamic response to tracheal intubation was 3.7 ng/ml during inhalational induction with 1 MAC desflurane.

Intravenous dexamethasone pretreatment reduces remifentanil induced cough.

BackgroundRemifentanil infusion is commonly used for general anesthesia but reflex cough can occur after an intravenous (IV) infusion. This study was designed to examine the effect of IV-dexamethasone on remifentanil-induced cough (RIC).MethodsOne hundred thirty patients scheduled for elective surgery were randomly assigned into two groups that received by either 2 ml of IV 0.9% saline (Group C, n = 68) or 10 mg of dexamethasone (Group D, n = 62) 5 min before administration of remifentanil at a target effect-site concentration of 5 ng/ml. The incidence and severity of coughs of each patient were recorded.ResultsThe overall incidence of cough was 6.5% (4/62 patients) in Group D and 26.5% (18/68 patients) in the Group C (P = 0.002). The severity of cough observed was significantly different by dexamethasone pretreatment (P = 0.02) but there were no significant hemodynamic changes.ConclusionsPretreatment with dexamethasone after IV administration was effective in suppressing the reflex cough induced by remifentanil infusion.

Effect-site concentration of remifentanil for blunting hemodynamic responses to tracheal intubation using light wand during target controlled infusion-total intravenous anesthesia

BackgroundTransillumination using a light wand is an alternative type of laryngoscope used for tracheal intubation. There is little information available on the effect-site concentration of remifentanil required to control hemodynamic changes induced by tracheal intubation using the transillumination method during total IV anesthesia. We therefore conducted this study to determine the effect-site concentration of remifentanil blunting hemodynamic responses after tracheal intubation in patients receiving propofol anesthesia.MethodsWe enrolled 26 healthy adult patients (ASA physical status I-II), aged 16-67 scheduled for surgery within 2 hours. All patients received a target-controlled infusion of 4 µg/ml propofol. The effect-site target-concentration of remifentanil of 5.0 ng/ml was chosen for the first patient. We used the Dixon's up-and-down sequential allocation method for determining the next remifentanil concentration. The time required for tracheal intubation was measured as the level of intubation stimulation.ResultsThe average intubation time was 13.9 ± 9.1 seconds. From the Dixon's method, the EC50 of remifentanil blunting the hemodynamic response to tracheal intubation was 2.94 ng/ml.ConclusionsThis study shows that effect-site concentrations of remifentanil of 2.94 ng/ml is effective in blunting sympathetic responses to tracheal intubation in 50% of patients with normal airway anatomy when combined with a target controlled infusion of propofol (4 µg/ml).

Pharmacodynamics of sufentanil required to inhibit body movement induced by tetanic stimulation and skin incision when combined with propofol in patients undergoing thoracic or abdominal surgery

Objective To investigate the pharmacodynamics of sufentanil required to inhibit the body movement induced by tetanic stimulation and skin incision when combined with propofol in patients undergoing thoracic or abdominal surgery. Methods Fifty ASA Ⅰ or Ⅱ patients aged 18-57 yr undergoing elective thoracic or abdominal surgery were randomized into 5 groups sufentanil target effect-site concentration （Ce） （n = 10 each）：0.07, 0.10, 0.14, 0.20 and 0.28 ng/ml groups. Anesthesia was induced with TCI of propofol at the target plasma concentration of 3.0-3.2 μg/ml. As soon as the patients lost consciousness, infusion of sufentanil with the corresponding Ce was started in the each group. One tetanic stimulus （frequency 50 Hz, intensity 80 mA, wave length 0.25 ms） was given after the target effect-site and plasma concentrations were balanced. Tracheal intubation was facilitated with succinylcholine 1.5 mg/kg. The concentrations of propofol and sufentanil were maintained until 4 min after skin incision. The body movement was observed during tetanic stimulation and skin incision. The effective effect-site concentration （EC50, EC94） of sufentanil and 95% confidence interval （CI） were calculated using probit regression analysis. Results The EC50 and EC95 of sufentanil required to inhibit the body movement induced by tetanic stimulation when combined with propofol were 0.12 （95% CI 0.09-0.14） ng/ml and 0.20 （95% CI 0.17-0.31） ng/ml respectively. The EC50 and EC95 of sufentanil required to inhibit the body movement induced by skin incision when combined with propofol were 0.13 （95% CI 0.11-0.16） ng/ml and 0.21 （95% CI 0.17-0.29） ng/ml respectively. There was no significant difference in the EC50 and EC95 of sufentanil between the two different stimuli （P 〉 0.05）. Conclusion The EC50 and EC95 of sufentanil required to inhibit the body movement induced by tetanic stimulation （frequency 50 Hz, intensity 80 mA, wave length 0.25 ms） when combined with propofol were 0.12 and 0.20 ng/ml respectively, the EC50 and EC95 of sufentanil required to inhibit the body movement induced by skin incision when combined with propofol were 0.13 and 0.21 ng/ml respectively and there was no significant difference in the pharmacodynamics between the two different stimuli, indicating that tetanic stimulation as an alternative to skin incision can be used to evaluate the pharmacodynamics of anesthetics. Key words: Propofol; Sufentanil; Electric stimulation; Dose-respense relationship,drug; Drug delivery systems

Optimal target concentration of remifentanil during cataract surgery with monitored anesthesia care

Study objective To determine the effect-site target concentration (C et) of remifentanil that provides optimal conditions for patients and operators during cataract surgery during monitored anesthesia care using a target controlled infusion (TCI) of propofol and remifentanil. Design Prospective, randomized, double-blinded study. Setting Operating room and postoperative recovery area of a university-affiliated hospital. Patients 66 adult, ASA physical status I, II, and III patients undergoing cataract surgery Interventions Group I received C et of remifentanil 0.5 ng/mL; Group 2 received C et of remifentanil one ng/mL; and Group 3 received C et of remifentanil 1.5 ng/mL. After giving TCI propofol (C et; one μg/mL) - remifentanil, an ophthalmologist administered topical anesthesia. Measurements and main results Intraoperative hemodynamics, pain scores, sedation scores, patient satisfaction scores, and operators’ satisfaction scores regarding surgical conditions were recorded. No statistical differences in heart rate or mean blood pressure were detected among the three groups during surgery. Pain scores (Group 1: 31.9 ± 17.9 vs. Group 2: 11.8 ± 7.7 and Group 3: 11.8 ± 7.7; P < 0.05) were higher and patient satisfaction scores (Group 1: 4.7 ± 0.8 vs. Group 2: 5.4 ± 0.4 and Group 3: 5.5 ± 0.4; P < 0.05) were lower in Group 1 than Groups 2 and 3. On the other hand, surgeon satisfaction was lowest in Group 3 (Group 3: 2.9 ± 1.3 vs. Group 1: 4.7 ± 0.4 and Group 2: 4.6 ± 0.7; P < 0.05) due to ocular movement. Conclusion C et values of remifentanil and propofol of one ng/mL and one μg/mL, respectively, appear to provide optimal conditions for patients and operators during cataract surgery using monitored anesthesia care with TCI.

Predicted effect-site concentration of propofol and sufentanil for gynecological laparoscopic surgery

this study was to estimate the predicted effect-site concentration of propofol administered by a target-controlled infusion (TCI) for maintenance of anesthesia based on the bispectral (BIS) index as a measure of hypnosis in laparoscopic surgery. one-hundred and sixty unpremedicated patients undergoing gynecologic laparoscopy were assigned randomly to receive one of the target effect-site concentrations of propofol 2.0, 2.5, 3.0, 3.5 and 4.0 microg/ml during TCI with propofol and sufentanil. The dose-response relationship of propofol for the maintenance of adequate anesthesia based on BIS, movement and hemodynamic response was investigated using a fixed effect-site concentration of sufentanil (0.2 ng/ml). The BIS values, hemodynamic variables, time course during emergence and intraoperative awareness were also assessed. the predicted effect-site propofol concentrations for adequate anesthesia at the skin incision in 50% (EC(50) ) and 95% (EC(95) ) of patients undergoing gynecologic laparoscopy were 2.2 and 3.7 microg/ml, respectively. The predicted propofol EC(50) and EC(95) to maintain adequate anesthesia in these patients were 2.6 microg/ml (95% CI 2.3-2.7 microg/ml) and 3.6 microg/ml (95% CI 3.3-4.0 microg/ml), respectively. The BIS values, effect-site concentration of propofol, hemodynamic data and time course during emergence and post-operative adverse events were comparable in each group. There were no reports of intraoperative awareness in the post-anesthetic care unit. based on the anesthetic depth assessed by the clinical signs and BIS monitoring, the predicted effect-site propofol concentrations for the maintenance of anesthesia in patients undergoing gynecologic laparoscopy were similar in those administered adequate anesthesia at the skin incision during TCI.

Effect of Remifentanil on Arterial Oxygenation during One-Lung Ventilation

This study was designed to assess the dose-related effects of remifentanil on arterial oxygenation during one-lung ventilation (OLV) under total intravenous anaesthesia with propofol. A total of 104 patients scheduled for elective lung resection surgery requiring OLV were randomly assigned to one of four groups with a target effect-site concentration (Ce) of remifentanil of 0.5, 1, 2 or 4 ng/ml. Patients were anaesthetized with propofol and remifentanil in 100% oxygen. Arterial blood gas analysis was performed after 15 min of two-lung ventilation (TLV15, baseline) and after 15 and 30 min of OLV (OLV15 and OLV30). Mean arterial oxygen tension (PaO2) decreased significantly at OLV15 and OLV30 compared with baseline in all groups, but was comparable in the four groups at each time point, suggesting that remifentanil infusion with a Ce < or =4 ng/ml can be successfully used for anaesthesia with propofol during OLV in lung surgery without any significant changes in PaO2.

Effect of malignant tumor on neuromuscular block of cisatracurium

Objective To investigate the effect of malignant tumor on neuromuscular block of cisatracurium. Methods Sixty ASA Ⅰ or Ⅱ patients with head and neck neoplasms (15 cases with benign tumor, 45 with malignant tumor), aged 18-64 yr, were randomly divided into 4 groups ( n = 15 each): Ⅰ benign tumor group (group B,3 × ED95 ); Ⅱ -Ⅳ different dose cisatracurium group (group C1 (2 × ED95 ), C2 (3 × ED95 ) and C3 (4 ×ED95)). Neuromuscular block was assessed with accelerograph F (TOF-watch SX). Single stimulation of ulnar nerve was used. Anesthesia was induced with TCI of propofol (target plasma concentration 3 μg/ml) and remifentanil (target effect-site concentration 3 ng/ml). Tracheal intubation was facilitated with cisatracurium 0.15 mg/kg in group B, and with cisatracurium 0.10, 0.15 and 0.20 mg/kg in group C1, C2 and C3 respectively. The onset time, clinical duration, time for recovery of T/Tc to 75 % and recovery index were recorded. Results The clinical duration, time for recovery of T/Tc to 75 % and recovery index were significantly longer in group C2 than in group B (P ＜ 0.05). The onset time was significantly shorter, while the clinical duration and time for recovery of T/Tc to 75% were significantly longer in group C2 and C3 than in group C1 , and in group C3 than in group C2 ( P ＜0.05) .Conclusion The duration of action and recovery times of cisatracurium were prolonged in patients with malignant tumor. Key words: Atracurium; Neoplasms; Neuromuscular blockade

Propofol and Remifentanil Differentially Modulate Frontal Electroencephalographic Activity

The purpose of this study was to evaluate a new, physiologically inspired method for the analysis of the electroencephalogram during propofol-remifentanil anesthesia. Based on fixed-order autoregressive moving-average modeling, this method was hypothesized to be capable of dissociating the effects that hypnotic and analgesic agents have on brain electrical activity. Raw electroencephalographic waves from a previously published study were reanalyzed. In this study, 45 American Society of Anesthesiologists status I patients were randomly allocated to one of three groups according to a specific target effect-site remifentanil concentration (0, 2, and 4 ng/ml). All patients received stepwise-increased targeted effect-site concentrations of propofol (CePROP). At each step change in target CePROP, the Observer's Assessment of Alertness/Sedation score was evaluated. Raw electroencephalograph was continuously acquired from frontal electrodes. Electroencephalography traces were analyzed using a fixed-order autoregressive moving average model to give derived measures of Cortical State and Cortical Input. Response surfaces were visualized and modeled using Hierarchical Linear Modeling. Cortical State (a measure of cortical responsiveness) and Cortical Input (a measure of the magnitude of cortical input) were shown to respond differently to CePROP and effect-site remifentanil concentration. Cortical Input decreased significantly with increasing effect-site remifentanil concentration, whereas Cortical State remained unchanged with increasing effect-site remifentanil concentration but decreased with increasing CePROP. Because Cortical State responds principally to variations in CePROP, it is a potential measure of hypnosis, whereas the dependence of Cortical Input on effect-site remifentanil concentration suggests that it may be useful as a measure of analgesic efficacy and the nociceptive-antinociceptive balance.

Half-effective target plasma concentration of remifentanil inhibiting airway response when combined with propofol by TCI in patients undergoing fiberoptic bronchoscopy

Objective To determine the half-effective target plasma concentration （EC50） of remifentanil inhibiting airway response when combined with propofol by TCI in patients undergoing fiberoptic bronchoscopy. Methods Forty ASA I or II patients, aged 20-64 yr, undergoing elective fiberoptic bronchoscopy, were randomly divided into 2 groups （ n = 20 each）. Anesthesia was performed with TCI of remifentanil and propofol in both groups. The target effect site concentration of propofol was 3 ug/ml. The target effect site concentration of remifentanil was determined by up-and-down sequential trial. The target effect site concentration of remifentanil was set at 5 ug/ml in the first patient and the ratio of the target concentrations between the two consecutive patients was 1.1. BIS ≤ 60 was defined as the suitable depth of anesthesia in group A. The airway response ≤ grade II was defined as the suitable depth of anesthesia in group B. The EC50 and 95% confidence interval （CI） required to inhibit the airway response were calculated in the two groups. Results The EC50 and 95 % CI of remifentanil required to inhibit the airway response were 4.50 ug/L （95% CI 3.88-5.36 ug/L） in group A and 4.10ug/L （95 % CI 3.31-5.00 ug/L） in group B. The EC50 of remifentanil inhibiting airway response was significantly higher in group A than in group B. Conclusion The EC50 of remifentanil inhibiting airway response is 1. 10 ug/L when combined with propofol by TCI （effect site concentration 3 ug/ml） in patients undergoing bronchoscopy. BIS is not a suitable index assessing the depth of propofol-remifentanil anesthesia. Key words: Propofol ; Piperidines ; Drug delivery systems ; Bronchoscopy ; Dose-response relationship, drug

Effect‐site concentration of propofol for reduction of remifentanil‐induced cough

This study examined the effectiveness of different propofol infusion target concentrations on cough suppression, during a target-controlled remifentanil infusion. Four hundred patients were randomly assigned to receive propofol target effect-site concentrations of 0, 3.0, 4.5, or 6.0 microgxml(-1). When the propofol effect-site concentration reached the target, remifentanil was administered at a target effect-site concentration of 4.0 ngxml(-1). Episodes of cough were recorded over a 2-min period after remifentanil commencement, and graded as mild (1-2), moderate (3-4), or severe (5 or more). The overall incidence of cough was significantly decreased in by propofol 6.0 microgxml(-1) compared with 0 or 3.0 microgxml(-1) propofol (p < 0.001). The incidence of severe cough was significantly lower with propofol 6.0 microgxml(-1) compared with 3.0 microgxml(-1) (p = 0.03). A propofol target effect-site concentration of 6.0 microgxml(-1) effectively suppressed remifentanil-induced cough when remifentanil was administrated at a target effect-site concentration of 4.0 ngxml(-1).