A comparison of psoas compartment block and spinal and general anesthesia for outpatient knee arthroscopy

The optimal anesthetic technique for outpatient knee arthroscopy remains controversial. In this study, we evaluated surgical operating conditions, patient satisfaction, recovery times, and postoperative analgesic requirements associated with psoas compartment block, general anesthetic, or spinal anesthetic techniques. Sixty patients were randomized to receive a propofol/nitrous oxide/fentanyl general anesthetic, spinal anesthesia with 6 mg of bupivacaine and 15 micro g of fentanyl, or psoas compartment block with 40 mL of 1.5% mepivacaine. All patients received IV ketorolac and intraarticular bupivacaine. The frequency of postanesthesia recovery room admission was 13 (65%) of 20 for patients receiving general anesthesia, compared with 0 of 21 for patients receiving spinal anesthesia and 1 (5%) of 19 for patients receiving psoas block (P < 0.001). The median time from the end of surgery to meeting hospital discharge criteria did not differ across groups (131, 129, and 110 min for general, spinal, and psoas groups, respectively). In the hospital, 45% of general anesthesia patients received opioid analgesics, compared with 14% of spinal anesthesia and 21% of psoas block patients (P = 0.087). There was no difference among groups with respect to the time of first analgesic use or the number of patients requiring opioid analgesia. Pain scores were highest in patients receiving general anesthesia at 30 min (P = 0.032) and at 60, 90, and 120 min (P < 0.001). Patient satisfaction with anesthetic technique (P = 0.025) and pain management (P = 0.009) differed significantly across groups; patients receiving general anesthesia reported lower satisfaction ratings. We conclude that spinal anesthesia or psoas block is superior to general anesthesia for knee arthroscopy when considering resource utilization, patient satisfaction, and postoperative analgesic management. IMPLICATIONS: Outpatient knee arthroscopy may be performed using a variety of anesthetic techniques. We report that spinal anesthesia and psoas compartment block are superior to general anesthesia when considering resource utilization, patient satisfaction, and postoperative analgesic management.     

Anesthesia for craniotomy: total intravenous anesthesia with propofol and alfentanil compared to anesthesia with thiopental sodium, isoflurane, fentanyl, and nitrous oxide

STUDY OBJECTIVE: To compare a total intravenous (IV) anesthetic technique based on propofol and alfentanil with a commonly used anesthetic technique for craniotomy. DESIGN: Open-label, randomized, clinical study. SETTING: Neurosurgical clinic at a university hospital. PATIENTS: Forty patients, aged 18 to 55 years, scheduled for brain tumor surgery. INTERVENTIONS: In 20 patients, anesthesia was induced with fentanyl and thiopental sodium and maintained with fentanyl, dehydrobenzperidol, isoflurane, nitrous oxide (N2O), and a thiopental sodium infusion. Twenty patients were anesthetized with a propofol loading infusion followed by a maintenance infusion at a fixed rate. In addition, alfentanil was administered as a loading bolus, followed by a variable-rate infusion, with additional doses as necessary to maintain hemodynamic stability. MEASUREMENTS AND MAIN RESULTS: A decrease in blood pressure (BP) after induction with thiopental sodium was followed by a significant increase in BP and heart rate (HR) during intubation. BP and HR did not change during the propofol loading infusion. However, the administration of alfentanil was followed by a similar decrease in BP with a return to baseline values during the intubation period. Return of normal orientation (7 +/- 5 minutes vs 27 +/- 23 minutes) and concentration (12 +/- 12 minutes vs 35 +/- 37 minutes) was shorter and more predictable for the propofol-alfentanil-treated patients than for the thiopental sodium patients. Maintenance propofol concentration (nine patients) was between 3 +/- 0.69 micrograms/ml and 3.36 +/- 1.17 micrograms/ml, while the concentration at awakening was 1.09 microgram/ml. Alfentanil concentration at extubation (nine patients) was 79 +/- 34 ng/ml. CONCLUSION: A total IV anesthetic technique with propofol and alfentanil is a valuable alternative to a more commonly used technique based on thiopental sodium, N2O, fentanyl, and isoflurane.     

Jugular bulb oxygen saturation under propofol or sevoflurane/nitrous oxide anesthesia during deliberate mild hypothermia in neurosurgical patients

Sevoflurane and propofol have been widely used as anesthetic agents for neurosurgery. Recent evidence has suggested that the influence of these anesthetics on cerebral oxygenation may differ. In the present study, the authors investigated jugular bulb oxygen saturation (SjO2) during propofol and sevoflurane/nitrous oxide anesthesia under mildly hypothermic conditions. After institutional approval and informed consent, 20 patients undergoing elective craniotomy were studied. Patients were randomly divided to the group S/N2O (sevoflurane/nitrous oxide/fentanyl anesthesia) or the group P (propofol/fentanyl anesthesia). After induction of anesthesia, the catheter was inserted retrograde into the jugular bulb and SjO2 was analyzed. During the operation, patients were cooled and tympanic membrane temperature was maintained at 34.5 degrees C. SjO2 was measured at normocapnia during mild hypothermia and at hypocapnia during mild hypothermia. There were no statistically significant differences in demographic variables between the groups. During mild hypothermia, SjO2 values were significantly lower in group P than in group S/N2O. The incidence of SjO2 less than 50% under mild hypothermic-hypocapnic conditions was significantly higher in group P than in group S/N2O. These results suggest that hyperventilation should be more cautiously applied during mild hypothermia in patients anesthetized with propofol and fentanyl versus sevoflurane/nitrous oxide/fentanyl.     

Prolonged mivacurium-induced neuromuscular block. Case report

A 38-year-old white male patient was admitted to the hospital for elective surgery. General anesthesia was performed with propofol, alfentanil, nitrous oxide and mivacurium as neuromuscular blocker. Seven months before he had the same surgery without anesthetic problems (he received: propofol, vecuronium bromide, fentanil, nitrous oxide). Neuromuscular monitoring was carried out because the patient was included in a study assessing the clinical effect of mivacurium in microlaryngoscopy surgery. After mivacurium administration the first signs of recovery from neuromuscular block were observed after 255 min. The tracheal tube was withdrawn after 410 min from mivacurium administration, at this time the T1 was 80% of the control values and 7 min later the T1 reached 98%.     

Percutaneous recording of muscle nerve sympathetic activity during propofol, nitrous oxide, and isoflurane anesthesia in humans

The effects of propofol, nitrous oxide, and/or isoflurane on efferent activity of sympathetic muscle nerve fibers (MSA) were studied using percutaneous microneurographic recordings from the peroneal nerve. Eight ASA Physical Status 1 patients (30-70 yr of age) scheduled for otorhinolaryngeal surgery entered the study. The effects of propofol (2-2.5 mg.kg-1.min-1) induction, tracheal intubation, and maintenance of anesthesia with isoflurane (0.3%, 0.6%, and 1.2% end-tidal concentrations) and/or 70% nitrous oxide were studied with respect to MSA, arterial blood pressure, heart rate, and indices of skin blood flow (laser doppler photometry and finger pulse plethysmography). Induction of anesthesia with propofol decreased MSA to 34 +/- 2% (mean +/- SEM) (P less than 0.05), and subsequent tracheal intubation increased MSA rapidly to 151 +/- 23% (P less than 0.05) of the control level. Isoflurane administration both with and without nitrous oxide led to a decrease of MSA (P less than 0.05). However, during nitrous oxide/isoflurane anesthesia (1.0 MAC) MSA was 76 +/- 38% higher than when isoflurane was used alone, although this implied a decrease in anesthetic depth to 0.5 MAC. This indicates that nitrous oxide and isoflurane have opposite effects on sympathetic outflow. During undisturbed propofol, nitrous oxide, and/or isoflurane administration (up to 1.0 MAC), MSA retained its normal pulse synchronous pattern, indicating that modulation of sympathetic outflow from arterial baroreceptors was still present. Skin blood flow increased sevenfold to tenfold in association with propofol induction (P less than 0.05) and was maintained at an 11- to 19-fold increase during nitrous oxide and/or isoflurane anesthesia, without any difference between the two anesthetics.(ABSTRACT TRUNCATED AT 250 WORDS)     

Optimal Propofol-Alfentanil Combinations for Supplementing Nitrous Oxide for Outpatient Surgery

Background: The combination of propofol and alfentanil with nitrous oxide provides balanced anesthesia with rapid recovery and minimal emetic side effects. The object of this study was to compare recovery parameters at varying proportions of propofol and alfentanil, and to determine the dosing rate and plasma concentration of propofol necessary to supplement nitrous oxide in the presence of varying concentrations of alfentanil.

Methods: Forty-eight patients were anesthetized with nitrous oxide, targeted manual infusions of alfentanil (target plasma concentrations of 0, 50, 100, and 150 ng/ml), and propofol at rates that were varied up or down by 25% depending on the response (movement/no movement) of the preceding patient (at the same alfentanil target concentrations) to ulnar-nerve stimulation. The minimum concentrations of propofol and alfentanil required to prevent movement in 50% of patients (EC50) was determined by logistic regression. Speed of emergence and recovery of cognitive function, time of discharge, and incidence of side effects were compared for four different combinations of propofol and alfentanil with nitrous oxide.

Results: The EC50 for propofol alone with nitrous oxide was 6.1 [micro sign]g/ml. Alfentanil, at concentrations of 41 +/- 17 (SD), 113 +/- 54, and 130 +/- 61 ng/ml, reduced the EC50 of propofol to 3.3, 2.3, and 2.2 [micro sign]g/ml, respectively, and decreased emergence time (eye opening) to 8.1, 4.9, and 3.4 min, compared with 24.3 min for propofol alone. Side effects did not differ between groups.     

Remifentanil provides better analgesia than alfentanil during breast biopsy surgery under monitored anesthesia care

PURPOSE: To compare the analgesic effects of remifentanil and alfentanil during breast biopsy under monitored anesthesia care (MAC). METHODS: Sixty patients received sedation with propofol (50 microg.kg(-1).min(-1)). After receiving a loading dose of opioid (either remifentanil 0.5 microg.kg(-1), or alfentanil 2.5 microg.kg(-1)), an infusion was initiated (remifentanil 0.05 microg.kg(-1).min(-1) or alfentanil 0.25 microg.kg(-1).min(-1)), and this was supplemented with local anesthetic infiltration. The pain was evaluated with a ten-point visual analogue scale (VAS) during local anesthetic infiltration and deep tissue dissection. Inadequate analgesia, defined as VAS scores > or = 5, was treated first with boluses of opioid (remifentanil group 10 microg or alfentanil group 50 microg) and if inadequate after two treatments with additional local anesthetic. Postoperative times were recorded including the times until discharge criteria were achieved and patient's actual discharge. RESULTS: The pain scores were similar between the two groups during the initial injections of local anesthetic in the breast, however, patients in the remifentanil group had lower mean pain scores during deep tissue dissection (2.3 vs 4.3, P < 0.01). Patients in the remifentanil group required fewer rescue doses of opioid (1.9 vs 3.6, P < 0.03) and local anesthetic (5 vs 15, P < 0.006). The two study groups had comparable speed of recovery. CONCLUSION: Remifentanil was a better opioid choice than alfentanil for breast biopsy under MAC at the doses studied, but it did not increase the rapidity in which patients recovered postoperatively.     

Effects of Propofol or Isoflurane Anesthesia on Cardiac Conduction in Children Undergoing Radiofrequency Catheter Ablation for Tachydysrhythmias

Background: To determine suitability for ablation procedures in children, two commonly used anesthetic agents were studied: propofol and isoflurane.

Methods: Twenty patients presenting for a radiofrequency catheter ablation procedure were included and randomly assigned to two groups. A baseline electrophysiology study was performed during anesthesia with thiopental, alfentanil, nitrous oxide, and pancuronium in all patients. At the completion of the baseline electrophysiology study (EPS), 0.8-1.2% isoflurane was administered to patients in group 1 and 2 mg/kg propofol bolus plus an infusion of 150 micro gram *symbol* kg sup -1 *symbol* min sup -1 was administered to patients in group 2. Nitrous oxide and pancuronium were used throughout the procedure. After 30 min of equilibration, both groups underwent a repeat EPS. The following parameters were measured during the EPS: cycle length, atrial-His interval, His-ventricle interval, corrected sinus node recovery time, AV node effective refractory period, and atrial effective refractory period. Using paired t tests, the electrophysiologic parameters described above measured during propofol or isoflurane anesthesia were compared to those measured during baseline anesthesia. Statistical significance was accepted as P < 0.05.

Results: There was no statistically significant difference in the results obtained during baseline anesthesia when compared with those measured during propofol or isoflurane anesthesia.     

Differential effects of nitrous oxide and propofol on myogenic transcranial motor evoked responses during sufentanil anaesthesia

We have compared the effects of 50% nitrous oxide and propofol, each administered concurrently with sufentanil, on the amplitudes and latencies of the compound muscle action potential (CMAP) response to transcranial electrical stimulation. Using a crossover design, 12 patients undergoing spinal surgery were exposed to both 50% nitrous oxide and propofol, the latter in a bolus-infusion regimen. Six patients received nitrous oxide first and six received propofol first. CMAP were recorded from the tibialis anterior muscle in response to both single and paired transcranial electrical stimuli. With single pulse stimulation, median CMAP amplitude was significantly greater during administration of nitrous oxide than propofol (nitrous oxide 335 (10th-90th percentiles 35-849) microV; propofol 36 (0-251) microV) (P < 0.01). With paired stimulation, there was no significant difference in CMAP amplitude during the two regimens (nitrous oxide 1031 (296-1939) microV; propofol 655 (0-1867) microV). The results indicate that propofol caused more depression of transcranial electrical motor evoked responses than 50% nitrous oxide but that the difference was probably clinically unimportant when a paired stimulation paradigm was used.      

A comparison of local intraarticular anesthesia versus general anesthesia for ambulatory arthroscopic knee surgery

Various anesthetic techniques including local, regional, and general anesthesia have been utilized for ambulatory arthroscopic knee surgery. The choice of anesthetic technique for this surgical procedure can have a significant impact on postoperative recovery, side effects, and patient satisfaction. The objective of this randomized, prospective study is to evaluate the efficacy of utilizing either intraarticular (IA) local anesthesia or general anesthesia (GA) for patients undergoing outpatient arthroscopic knee surgery. Patients assigned to the local anesthesia group were administered an IA injection of 30 mL of bupivacaine 0.25% approximately 20-30 min before surgery. Intraoperative sedation was provided with the administration of propofol. Patients assigned to the GA group were administered propofol and fentanyl for induction and maintained with sevoflurane combined with nitrous oxide in oxygen by laryngeal mask airway. The surgeon injected 30 mL of bupivacaine 0.25% through the arthroscope at the completion of the surgical procedure. This study demonstrates that IA anesthesia provides for improved pain relief, decreased postoperative opioid use, postoperative nausea and vomiting (PONV), time spent in the recovery room, and improved patient satisfaction with similar operating conditions comparable to general anesthesia in patients undergoing outpatient arthroscopic knee surgery. Although both groups received a similar dose of IA bupivacaine, administering the local anesthetic prior to surgery resulted in more effective analgesia. We currently believe that intraarticular local anesthesia fulfills all the criteria for the optimal anesthetic technique for outpatient arthroscopic knee surgery.     

Use of propofol for office-based anesthesia: effect of nitrous oxide on recovery profile.

STUDY OBJECTIVE: To evaluate the effect of nitrous oxide (N2O) on the recovery profile and the incidence of postoperative nausea and vomiting (PONV) after office-based surgery performed under propofol anesthesia. DESIGN: Prospective, randomized, single-blind study. SETTING: Office-based surgical center. PATIENTS: 69 ASA physical status I, II, and III healthy, consenting outpatients undergoing superficial surgical procedures lasting 15 to 45 minutes. INTERVENTIONS: After a standard propofol induction (1.5 mg.kg-1 i.v.), anesthesia was initially maintained with propofol, 100 micrograms.kg-1.min-1 i.v., in combination with either air or N2O 65% in oxygen. The propofol infusion rate was subsequently varied to maintain an adequate depth of anesthesia. All patients received local anesthetic infiltration prior to the surgical incision, as well as during the operation. No prophylactic antiemetics were administered. MEASUREMENTS AND MAIN RESULTS: Recovery times and the incidences of PONV were recorded during the first 24 hours after surgery. Early and late recovery variables were similar in the two treatment groups; however, 65% N2O produced a 19% decrease in the propofol maintenance dosage requirement. One patient (3%) experienced nausea prior to discharge in the propofol-N2O group, and two patients (6%) experienced nausea at home in the propofol alone group. None of the patients vomited or received antiemetic medication during the 24 hours postdischarge period. Ninety-seven percent of patients receiving propofol alone and all of the patients in the propofol-N2O group were "very satisfied" with their anesthetic experience. CONCLUSIONS: In outpatients undergoing office-based surgical procedures with propofol anesthesia, administration of 65% N2O decreased the anesthetic requirement without increasing PONV. Therefore, use of a propofol-N2O combination may be a cost-effective alternative to propofol alone for office-based anesthesia.     

EEG-assisted titration of propofol infusion during neuroanesthesia: effect of nitrous oxide

Total intravenous anesthesia (TIVA) with propofol is an alternative to standard techniques for neuroanesthesia. The present study compared the hemodynamic and recovery profiles of 46 neurosurgical patients randomly assigned to one of three different anesthetic treatment groups. Group 1 was anesthetized with a TIVA technique in which propofol was titrated using an EEG-assisted quantification method. Group 2 received a similar propofol-based infusion technique in combination with nitrous oxide. Group 3 (control) received a standard anesthetic technique consisting of thiopental, nitrous oxide, fentanyl, and isoflurane. Significantly less propofol was required in group 2 than in group 1 (7.4 +/- 1.9 vs. 9.0 +/- 1.0 mg/kg/h, respectively). The propofol blood concentration at the first appearance of EEG burst suppression was also higher in group 1 compared to group 2 (5.8 +/- 1.1 vs. 4.8 +/- 0.8 microg/ml). However, 25% of the patients in group 2 were treated for hypotension after induction, compared to none in groups 1 and 3. Hypertensive episodes, on the other hand, were more frequent in groups 1 (43%) and 3 (31%) than in group 2 (12%). Time to awakening was significantly shorter in the control group (6 +/- 6 min) than in groups 1 (14 +/- 10 min) or 2 (12 +/- 16 min). In conclusion, titration of propofol to achieve a burst suppressive EEG pattern resulted in a slower emergence from anesthesia than a standard "balanced" technique. Use of nitrous oxide with propofol produced more hypotension during induction; however, its use improved hemodynamic stability during the maintenance period.     

Opioid supplementation during propofol anaesthesia

Sixty patients of ASA grade 1 or 2 who presented for minor daycase gynaecological or urological procedures were randomly allocated to three groups. Group A received fentanyl 1 microgram/kg and Group B alfentanil 5 micrograms/kg prior to induction. Group C received no pre-induction opioid. anaesthesia was induced intravenously with propofol and maintained using nitrous oxide 67% in oxygen supplemented with 20-mg bolus doses of propofol as required. The pre-induction administration of fentanyl or alfentanil was not found significantly to affect either the doses of propofol required for induction or maintenance or the quality of anaesthesia compared with propofol alone. These results suggest that for minor outpatient procedures under general anaesthesia, the concomitant use of a short-acting opioid confers no benefits over propofol with oxide and oxygen alone.     

Differential effects of isoflurane/nitrous oxide on posterior tibial somatosensory evoked responses of cortical and subcortical origin

Posterior tibial somatosensory evoked responses (SSERs) were recorded during administration of isoflurane and nitrous oxide. Responses arising from cortical and subcortical neural generators were examined to compare their relative resistance to anesthetic-related degradation. Recordings were performed in ten adults during anesthesia with 0.5 MAC isoflurane/60% N2O, 1.0 MAC isoflurane/60% N2O, and 1.5 MAC isoflurane/60% N2O. Thereafter, N2O was omitted and recordings were repeated during anesthesia with 1.5 and 1.0 MAC isoflurane/O2. Isoflurane resulted in a significant (P less than 0.001) dose-related decrease in the amplitude of cortical waveforms. The amplitude loss was substantial; e.g., for the first cortical waveform, amplitude decreased from 1.21 +/- 0.67 microV during 0.5 MAC isoflurane/N2O to 0.28 +/- 0.29 microV during 1.5 MAC/N2O. Elimination of N2O resulted in an increase in amplitude of approximately 100% (P less than 0.04). By contrast, the amplitude of the subcortical response as recorded in vertex to linked mastoid and vertex to upper cervical spine derivations was not significantly altered by changing concentrations of isoflurane or N2O. The results suggest that subcortical SSERs may be preferable to those of cortical origin for spinal cord monitoring in situations where isoflurane and nitrous oxide, especially in varying concentrations, are the primary anesthetic agents.     

Nitrous oxide prevents movement during orotracheal intubation without affecting BIS value

We sought to determine whether the addition of nitrous oxide (N(2)O) to an anesthetic with propofol and remifentanil modifies the bispectral index (BIS) during the induction of anesthesia and orotracheal intubation. Thirty ASA physical status I or II patients were randomly allocated to receive either 50% air in oxygen (control group) or 60%-70% N(2)O in oxygen (N(2)O group) that was commenced via a mask simultaneously with the induction of anesthesia. Anesthesia was performed in all the patients with IV propofol at the target effect compartment site concentration of 4 microg/mL throughout the study. A target-controlled infusion (TCI) of remifentanil was initiated 3 min after the TCI of propofol and maintained at the effect-site concentration of 4 ng/mL until the end of the study. After loss of consciousness, and before the administration of vecuronium 0.1 mg/kg, a tourniquet was applied to one arm and inflated to a value more than the systolic blood pressure. An examiner, blinded to the presence of N(2)O, sought to detect any gross movement within the first minute after tracheal intubation, which was performed 10 min after remifentanil TCI began. Inspired and expired oxygen, N(2)O, and carbon dioxide were continuously monitored. A BIS value was generated every 10 s. Arterial blood pressure and heart rate (HR) were measured noninvasively every minute. Measures of mean arterial pressure (MAP), HR, and BIS were obtained before the induction, before the start of the remifentanil TCI, before laryngoscopy, and 5 min after intubation. No significant intergroup differences were seen in BIS, HR, and MAP throughout the study. Maximum changes in BIS, HR, and MAP with intubation were significant (P < 0.01) for both groups but comparable. Six patients in the control group and none in the N(2)O group moved after intubation (P < 0.05). IMPLICATIONS: We demonstrated that 0.6 minimal alveolar concentration of nitrous oxide combined with a potent anesthetic and an opioid prevents movement after orotracheal intubation without affecting the bispectral index. This demonstrates that the bispectral index is not a useful neurophysiologic variable to monitor the level of anesthesia when nitrous oxide is added to a general anesthetic regimen using propofol and remifentanil.     

A cost comparison of methohexital and propofol for ambulatory anesthesia.

Methohexital is eliminated more rapidly than thiopental, and early recovery compares favorably with propofol. We designed this study to evaluate the recovery profile when methohexital was used as an alternative to propofol for the induction of anesthesia before either sevoflurane or desflurane in combination with nitrous oxide. One hundred twenty patients were assigned randomly to one of four anesthetic groups: (I) methohexital-desflurane, (II) methohexital-sevoflurane, (III) propofol-desflurane, or (IV) propofol-sevoflurane. Recovery times after the anesthetic drugs, as well as the perioperative side effect profiles, were similar in all four groups. A cost-minimization analysis revealed that methohexital was less costly for the induction of anesthesia. At the fresh gas flow rates used during this study, the costs of the volatile anesthetics for maintenance of anesthesia did not differ among the four groups. However, at low flow rates (< or = 1 L/min), the methohexital-desflurane group would have been the least expensive anesthetic technique. In conclusion, methohexital is a cost-effective alternative to propofol for the induction of anesthesia in the ambulatory setting. At low fresh gas flow rates, the methohexital-desflurane combination was the most cost-effective for the induction and maintenance of general anesthesia. Implications: Using methohexital as an alternative to propofol for the induction of anesthesia for ambulatory surgery seems to reduce drug costs. When fresh gas flow rates < or = 1 L/min are used, the combination of methohexital for the induction and desflurane for maintenance may be the most cost-effective general anesthetic technique for ambulatory surgery.     

Does functional ability in the postoperative period differ between remifentanil- and fentanyl-based anesthesia?

STUDY OBJECTIVES: To compare patients' functional ability in the 24-hour postoperative period following a remifentanil compared to a hypnotic-fentanyl-treated anesthesia regimen using a 24-Hour Functional Ability Questionnaire. DESIGN: Prospective, 1:1 single-blind, randomized, controlled effectiveness study. SETTING: Multicenter study including 156 hospitals and ambulatory surgery facilities. PATIENTS: 2438 patients (1496 outpatients and 942 inpatients) 18 years of age or older, scheduled for elective surgeries under general endotracheal anesthesia, with an expected duration of unconsciousness of > or =30 minutes. INTERVENTIONS: Patients were randomized to receive either intravenous remifentanil (0.5 microg/kg/min for induction and intubation; with the infusion rate decreased to 0.25 microg/kg/min after intubation) or fentanyl (administered according to anesthesiologists' usual practice) as the opioid during surgery. Concomitant hypnotic drugs were propofol and/or isoflurane (with or without nitrous oxide) titrated according to protocol. Transition analgesia with either morphine or fentanyl was given in the remifentanil patients and at the discretion of the anesthesiologists in the fentanyl patients. MEASUREMENTS: A validated set of measurements of functional ability, rather than more traditional clinical psychological methods, to compare the recovery of patients from remifentanil- and fentanyl-treated anesthetic regimens up to 24 hours after surgery. MAIN RESULTS: Remifentanil was statistically superior to fentanyl for the four functional assessments evaluated: walking without dizziness, thinking clearly, concentration, and communicating effectively. These differences reflect events occurring within the first 24 hours after anesthesia and surgery. CONCLUSIONS: A remifentanil-treated anesthetic demonstrated earlier return to some functions than a fentanyl-treated technique. Although functional assessment is a field that is still in its infancy, a questionnaire to assess functional ability during the 24 hours after anesthesia may provide more practical information about anesthetic recovery than previously used, traditional psychomotor evaluations.     

Closed loop control of anaesthesia: an assessment of the bispectral index as the target of control

We investigated the performance of a closed-loop system for administration of general anaesthesia, using the bispectral index as a target for control. One hundred patients undergoing gynaecological or general surgery were studied. In 60 patients, anaesthesia was maintained by intravenous infusion of a propofol/alfentanil mixture. In 40, an isoflurane/nitrous oxide based technique was used. For each technique, patients were randomly allocated to receive either closed-loop or manually controlled administration of the relevant agents (propofol/alfentanil or isoflurane), with an intra-operative target bispectral index of 50 in all cases. Closed-loop and manually controlled administration of anaesthesia resulted in similar intra-operative conditions and initial recovery characteristics. During maintenance of anaesthesia, cardiovascular and electro-encephalographic variables did not differ between closed-loop and manual control groups and deviation of bispectral index from the target value was similar. Intra-operative concentrations of propofol, alfentanil and isoflurane were within normal clinical ranges. Episodes of light anaesthesia were more common in the closed-loop group for patients receiving propofol/alfentanil anaesthesia and in the manual group for patients receiving isoflurane/nitrous oxide anaesthesia. Convenience aside, the closed-loop system showed no clinical advantage over conventional, manually adjusted techniques of anaesthetic administration.     

Cost comparison between three different general anaesthetic techniques for elective arthroscopy of the knee

INTRODUCTION: We compared three anaesthetic techniques for elective knee arthroscopy with special reference to cost-effectiveness. METHOD: Seventy-five ASA I-II patients having elective arthroscopy of the knee joint were randomised to receive an anaesthetic technique based on propofol, fentanyl for induction followed by sevoflurane in oxygen:nitrous oxide (1:2 l/min) for maintenance of one of two intravenous techniques: propofol alfentanil or propofol-remifentanil infusions in combination with oxygen in air. RESULTS: All patients had an uncomplicated course. No differences were seen with regard to emergence, postoperative pain or emesis or time to discharge. The anaesthetic technique based on sevoflurane was associated with the lowest cost US$ 14.7 as compared to US$ 18 for the propfol/alfentanil and US$ 19.9 for the propofol/remifentanil technique, including both cost for wastage as well as premedication and other fixed drug costs. Looking only at the anaesthetic drugs consumed, the cost per minute was US$ 0.56 for sevoflurane/nitrous oxide as compared to US$ 0.68 and 0.63 per minute for the propofol/alfentanil and proprofol/remifentanil, respectively. When the cost for wastage was taken into account, the difference in mean anaesthetic drug cost was more pronounced: the sevoflurane anaesthetic technique US$ 0.58, the propofol/alfentanil US$ 0.74 and the propofol/remifentanil US$ 0.84 per minute respectively. CONCLUSION: From a cost-minimisation point of view, anaesthesia based on sevoflurane in oxygen:nitrous oxide is the technique of choice.     

Ventilatory effects of nitrous oxide during continuous infusion of fentanyl or alfentanil

Two groups of eight patients received infusions of either fentanyl at 3 micrograms kg-1 h-1 or alfentanil at 20 micrograms kg-1 h-1 as supplements to 66% N2O in oxygen anaesthesia, during and after body surface surgery. At the end of surgery, the N2O was reduced to 50% and after measurement of ventilatory frequency, minute ventilation, and the ventilatory response to carbon dioxide, N2O was discontinued. The opioid infusions were continued for a further hour and the ventilatory measurements repeated. Both sets of measurements were compared with preoperative values. Minute ventilation (P less than 0.01), frequency (P less than 0.01) and the response to carbon dioxide (P less than 0.01) were reduced during the infusion of fentanyl with N2O; with fentanyl alone, minute ventilation (P less than 0.05) and the response to carbon dioxide (P less than 0.01) were reduced but to a lesser degree. The elimination of nitrous oxide from the inspired gas mixture produced an increase in frequency (P less than 0.05) and increases in the slope (P less than 0.01) and ventilation at 7.3 kPa (P less than 0.025) of the carbon dioxide response curve. Minute ventilation (P less than 0.01) frequency (P less than 0.05) and response to carbon dioxide (P less than 0.01) were all reduced during the infusion of alfentanil with nitrous oxide; with alfentanil alone, minute ventilation (P less than 0.01), tidal volume (P less than 0.05), the slope (P less than 0.025) and the ventilation at 7.3 kPa (P less than 0.01) of the carbon-dioxide response curve were still reduced.(ABSTRACT TRUNCATED AT 250 WORDS)