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[Total intravenous anesthesia using propofol and alfentanil as compared to combined inhalation anesthesia reduces the flow velocity in the middle cerebral artery. A Doppler sonographic study].

Anesthesia for craniotomies should guarantee hemodynamic stability, preservation of cerebral autoregulation, and rapid postoperative recovery of consciousness. Increases in intracranial pressure (ICP) and postoperative respiratory depression should be avoided. Combined anesthesia (KA) with N2O and volatile anesthetics may increase cerebral blood flow (CBF), ICP, and cerebral oxygen consumption. According to recent studies, total intravenous anesthesia (TIVA) with propofol and alfentanil seems to best fulfill the requirements. Using transcranial Doppler sonography (TCD) (TC2-64, EME), we studied the influence of TIVA and KA under normo- and hyperventilation on the blood flow velocity (BFV) and pulsatility of the middle cerebral artery (MCA). METHODS. Two groups of 10 patients each undergoing craniotomy were investigated. Systolic and mean BFV, pulsatility index, mean arterial blood pressure, heart rate, and arterial CO2 tension were measured at four time intervals: (1) preoperatively; (2) 15 min after anesthesia induction under normoventilation, preoperatively; (3) 25 min after anesthesia induction under hyperventilation, preoperatively; and (4) 6 h postoperatively. The patients were premedicated with flunitrazepam 1 mg PO. TIVA was induced with 60 mg propofol, 1 mg alfentanil, and 6 mg vecuronium; simultaneously infusions of propofol (15 mg/min) and alfentanil (0.3 mg/min) were started and were maintained until the dura was completely opened. The infusion rates were then reduced to 6 mg/min propofol until skin suturing and 0.1 mg/min alfentanil until dural suturing was completed. Patients were ventilated with O2/air (fiO2 = 0.5). In the KA group anesthesia was induced with 4-6 mg/kg thiopental, 0.15 mg fentanyl, and 6 mg vecuronium and maintained with boluses of fentanyl, N2O (fiO2 = 0.5), and isoflurane (1.3 MAC). The time course is illustrated in Figs. 1 and 2 and the results are shown in Tables 1 and 2. They were tested using a one-factor analysis of variance and the Kruskal-Wallis range test. RESULTS. There was a significant decrease in systolic and mean BFV combined with an increase in pulsatility index after induction of TIVA, while KA induction effected no significant change in cerebral hemodynamics. The subsequent hyperventilation caused a similar decrease in mean BFV and increase in pulsatility index in both groups. CONCLUSION. Using the assumption that the diameter of the MCA is nearly constant, the reduction in BFV associated with an increase in pulsatility during TIVA is explainable as a decrease in CBF. By having a comparable influence on hemodynamics, the reduction in CBF with increase in cerebral vascular resistance seems to make TIVA the more advantageous anesthesia technique for patients with reduced intracranial compliance.

Adult↗

Total intravenous anesthesia with propofol and remifentanil is associated with a nearly twofold higher incidence in postanesthetic shivering than desflurane-fentanyl anesthesia.

BACKGROUND: Postanesthetic shivering (PAS) is a frequent side effect of general anesthesia. Previous reports on the incidence of PAS of propofol for the induction or maintenance of anesthesia have been controversial, but have not been studied in detail. The aim of the present study was to evaluate the incidence and severity of PAS in total intravenous anesthesia (TIVA) with propofol and remifentanil compared with an inhalative anesthesia. MATERIAL/METHODS: After ethics committee approval and written informed consent from the patients, 53 patients scheduled for urologic, gynecologic, or surgical operations were studied for shivering postoperatively using a five-point rating scale. They received desflurane-fentanyl based anesthesia (n=27) or TIVA with propofol and remifentanil (n=26). Hemodynamics and temperature were measured after induction of anesthesia (T0), and 5 min (T1), 15 min (T2), 30 min (T3), and 60 min (T4) after reaching the postanesthetic care unit (PACU). RESULTS: In the TIVA group, 18/26 (69.2%) patients suffered from PAS compared with 10/27 (37%) in the desflurane-fentanyl group (P<0.02). The severity of shivering was significantly higher with TIVA than with desflurane (P<0.02), whereas temperature showed no significant difference between the study groups. CONCLUSIONS: Postanesthetic shivering appears significantly more frequently and intensively after TIVA with propofol and remifentanil compared with an inhalative anesthesia with fentanyl and desflurane.

Aged↗

[Changes in the concentrations of catecholamines and cortisol in balanced anesthesia and total intravenous anesthesia].

OBJECTIVE: To compare hormone response to stress caused by surgery performed under balanced general anesthesia and total intravenous anesthesia. PATIENTS AND METHOD: Two randomly formed groups of 24 patients each were studied. All patients were scheduled for lumbar laminectomy to correct disc hernias, with one group receiving balanced anesthesia with isoflurane (expiratory fraction between 0.5% and 0.6%), and the second group receiving total intravenous anesthesia (TIVA) (propofol infusion changed every 10 min from 12 to 6 mg/kg/h). Analgesics and relaxants were given by continuous infusion at preestablished doses (fentanyl 2 micrograms/kg/h; vecuronium 0.05 mg/kg/h). Cortisol and catecholamine (adrenalin, noradrenaline and dopamine) levels were determined at the following times: the morning of surgery (baseline), 5 min after intubation, 5 min after incision, 30 and 60 min after intubation; 5 min after tube removal and upon admission to the recovery unit. RESULTS: Cortisol levels decreased from baseline (14 +/- 3 pg/ml) until 30 min after intubation (4 +/- 2 pg/ml; p < 0.05) in the balanced anesthesia group. Adrenaline levels followed the same pattern (baseline 77 +/- 7 versus 57 +/- 10 pg/ml 30 min after intubation). Dopamine levels were statistically different (p < 0.05) at baseline (42 +/- 3 pg/ml), after intubation (38 +/- 2 pg/ml) and after incision (35 +/- 3 pg/ml), but the difference disappeared 30 minutes after intubation (38 +/- 8 pg/ml). Noradrenaline levels after incision (425 +/- 116 pg/ml) were significantly different from those at baseline (671 +/- 124 pg/ml), and the difference was evident until 60 min after incision. In the TIVA group we found significantly higher cortisol levels after intubation (21 +/- 0 pg/ml) than after baseline (14 +/- 2 pg/ml); this level decreased after extubation (7 +/- 0 pg/ml; p < 0.05). Adrenaline levels were significantly higher than at baseline (64 +/- 11 pg/ml) at times corresponding to intubation (76 +/- 5 pg/ml) and extubation (48 +/- 5 pg/ml). Noradrenaline increased significantly over baseline (497 +/- 99 pg/ml) after incision (597 +/- 90 pg/ml) and decreased significantly after 30 min. The increases in cortisol were significantly greater in the TIVA group than in the control group after intubation (21 +/- 0 versus 8 +/- 3 pg/ml, respectively) after intubation, after incision (18 +/- 2 versus 6 +/- 3 pg/ml) and 30 minutes after intubation (15 +/- 2 versus 4 +/- 2 pg/ml). Similar differences were found for dopamine after intubation (49 +/- 2 versus 38 +/- 2 pg/ml) and after incision (45 +/- 5 versus 35 +/- 3 pg/ml). CONCLUSIONS: Hormone levels are significantly higher during intravenous anesthesia than during balanced anesthesia, and the difference is evident from the earliest measurement performed.

Adult↗

Electronic anesthesia versus topical anesthesia for the control of injection pain.

The ability of a dental transcutaneous electronic nerve stimulator to control pain from injection of local anesthesia was compared to the pain-controlling ability of topical anesthesia. Two maxillary infiltration injections were completed on 21 patients, one injection after electronic anesthesia, the other after topical anesthesia. Patients reported the level of pain caused when the needle pierced their tissue and the solution was injected and their overall evaluation of the injection. No difference was reported for piercing of the tissue; however, the level of pain was very low. Significantly less pain was reported for the injection of local anesthesia solution and the overall evaluation of the injection was more favorable when electronic anesthesia was used. The patients preferred the electronic technique three to one over the topical anesthesia.

Adolescent↗

Anesthesia monitoring by registered nurses during cataract surgery: assessment of need for intraoperative anesthesia consultation.

PURPOSE: To assess the frequency and risk factors for intraoperative anesthesia consultation when performing cataract surgery monitored by registered nurses. SETTING: Iowa City Veterans Affairs Medical Center, Iowa City, Iowa, USA. METHODS: This retrospective review was of 270 cataract surgeries performed under local anesthesia from April 1, 2002, to April 1, 2003. RESULTS: The American Society of Anesthesiologists (ASA) classification of each patient was determined: 1 patient was classified as ASA 1. One hundred fifty patients were classified as ASA 2. One hundred nineteen patients were classified as ASA 3. The anesthesiology department was consulted 24 times. Nineteen consultations involved patients who were ASA 3, and 5 consultations involved patients who were ASA 2 (P<.001). In most cases (23 of 24), the anesthesia service provided a consultation (eg, increase oxygen flow rate, clarification of electrocardiogram, start intravenous line, equipment repair) and left the nurses to continue to monitor the patient. In only 1 case (ASA 3), the anesthesia service converted the case to monitored anesthesia care and relieved the nurse to monitor the patient. CONCLUSIONS: In this study, monitoring of routine cataract surgery by registered nurses was associated with a low rate of intraoperative anesthesia consultation. Most consultations resulted in little intervention. The ASA classification appears predictive of the need for intraoperative anesthesia consultation.

Anesthesia, Local↗

A comparison of patient comfort during cataract surgery with topical anesthesia versus topical anesthesia and intracameral lidocaine.

OBJECTIVE: To determine whether intraocular lidocaine increases patient comfort during cataract surgery while under topical anesthesia. DESIGN: Prospective, randomized, double-masked, placebo-controlled clinical trial. PARTICIPANTS: Both men and women between 45 and 85 years of age who were scheduled for elective cataract surgery while under topical anesthesia participated. Sixty-eight patients were randomized to each group. INTERVENTION: Patients were randomized to receive either topical anesthesia plus intracameral 1% preservative-free lidocaine or intracameral balanced salt solution. MAIN OUTCOME MEASURES: Patient assessment of pain during delivery of the anesthesia, surgery, and after surgery using a visual analog pain scale was measured. Patients also recorded the degree to which they were bothered by tissue manipulation and the microscope light. Surgeon assessments of operative conditions, patient cooperation, and intraoperative complications were recorded. The attending anesthesiologist recorded any required supplemental intravenous sedation and any increase in pulse or increase in blood pressure. RESULTS: There was no significant difference in patient-reported pain scores for delivery of anesthesia (P = 0.902), surgery (P = 0.170), or after surgery (P = 0.680). Patients in the lidocaine group reported being less bothered by tissue manipulation (P = 0.021). The surgeon assessment showed more patient cooperation in the lidocaine group (P = 0.043). CONCLUSIONS: Both topical anesthesia alone and topical anesthesia plus intracameral lidocaine provide good operative conditions for the surgeon and comfortable surgical circumstances for the patient. Injection of intraocular lidocaine increases patient cooperation and decreases the degree to which patients are bothered by tissue manipulation, two outcomes that justify its use.

Administration, Topical↗

Cost analysis of xenon anesthesia: a comparison with nitrous oxide-isoflurane and nitrous oxide-sevoflurane anesthesia.

STUDY OBJECTIVE: To determine the cost of xenon (Xe) anesthesia in relation to the anesthetic duration by conducting a cost analysis of this relatively expensive inhaled anesthetic. DESIGN: Cost analysis based on the literature on Xe anesthesia. SETTING: Anesthetic simulation based on data obtained in the operating rooms at a university hospital. PATIENTS: A 40-year-old, ASA physical status I adult patient model weighing 70 kg, undergoing elective minor surgery with endotracheal intubation and mechanical ventilation. INTERVENTIONS: Anesthesia was given in the following four techniques: 1) closed-circuit technique with Xe; 2) closed-circuit technique with nitrous oxide (N2O)-isoflurane; 3) semi-closed technique with N2O-isoflurane; and 4) semi-closed technique with N2O-sevoflurane. MEASUREMENTS AND MAIN RESULTS: Cost of each anesthetic technique was compared in U.S. dollars. The cost of Xe anesthesia was consistently higher than that of N2O-isoflurane or N2O-sevoflurane (for 240-min anesthesia; $356 with Xe, $52 with closed-circuit N2O-isoflurane, $94 with semi-closed N2O-isoflurane, and $84 with semi-closed N2O-sevoflurane). The major cost of Xe anesthesia was a result of the cost of priming and flushing; the cost of Xe used for its anesthetic effects was comparable with the other semi-closed techniques after 240 minutes. CONCLUSIONS: For Xe to be widely used in routine anesthesia, the methods of minimizing the amount of Xe necessary for priming and flushing must be developed.

Adult↗

Anesthesia and Prader-Willi syndrome: preliminary experience with regional anesthesia.

The constellation of neonatal hypotonia, developmental delay, hypogonadism and obesity caused by hyperphagia was first reported in 1956 and subsequently termed Prader-Willi syndrome (PWS). Genetic analysis has demonstrated abnormalities of chromosome 15. Anesthesia concerns of PWS include morbid obesity, the potential for difficulties with airway management, risk for perioperative respiratory failure, abnormalities in the central control of ventilation and temperature, rare reports of primary myocardial involvement, aggressive and at times violent behavior and glucose intolerance. For the first time, we report the use of regional anesthesia in four patients with PWS. A lumbar plexus catheter was used to provide postoperative analgesia in one patient while regional anesthesia (fasica iliaca block, spinal anesthesia, and lateral vertical infraclavicular block) was used to provide primary intraoperative anesthesia in three other patients while avoiding the need for general anesthesia. Previous reports of the anesthesia care of patients with PWS are reviewed and the potential perioperative implications of the sequelae of PWS are discussed.

Anesthesia, Conduction↗

[Clinical study on total intravenous anesthesia with droperidol, fentanyl and ketamine--15. Application for cardiac anesthesia].

Total intravenous anesthesia with droperidol, fentanyl and ketamine (DFK) was administered to 36 cardiac patients who underwent mostly coronary artery bypass graft or heart valve replacement. The induction and maintenance of anesthesia using this technique were almost satisfactory with little decrease in systolic blood pressure (SBP), although six patients among the early 21 patients developed hypotension below 90 mmHg (SBP) during the induction, and required vasopressors. Half of the patients had hypertensive episode of above 180 mmHg (SBP), from the start of operation to onset of cardiopulmonary bypass, which was safely and effectively overcome by a small dose of antihypertensive agents. Total intravenous anesthesia with DFK was accompanied with much more hypertensive episodes compared to anesthesia with moderate dose fentanyl (30 micrograms.kg-1) combined with enflurane. However, the incidence of cardiovascular complications following anesthesia was not statistically different between the two anesthesia groups. In addition, most of the patients with DFK showed a rapid awaking time with relatively good postoperative cardiovascular stability. These findings suggest that total intravenous anesthesia with DFK is accompanied with minimal hemodynamic changes during and after open heart surgery.

Aged↗

Comparison of retrobulbar anesthesia and intracameral anesthesia using preservative free bupivacaine hydrochloride 0.5% in phacoemulsification with posterior chamber intraocular lens implantation.

OBJECTIVE: To compare the retrobulbar anesthesia and intracameral anesthesia using preservative-free bupivacaine hydrochloride 0.5% in terms of effectiveness, complications and comfort to the patient during phacoemulsification with posterior chamber intraocular lens implantation. METHODS: This was a hospital based comparative study of two methods of anesthesia, conducted at LRBT Free Eye and Cancer Hospital, Lahore from January to July 2000. Study included 200 patients with uncomplicated age-related cataract, equally divided in two groups on simple random basis. Group A (100 patients) received the retrobulbar anesthesia and Group B (100 patients) received the intracameral anesthesia with bupivacaine hydrochloride 0.5% for phacoemulsification with posterior chamber intraocular lens implantation. Outcome measures like pain, visual acuity, intraocular pressure and anterior chamber reaction were compared. RESULTS: On day 1, 79% of the patients in group A and 82% patients in group B had unaided visual acuity ranging between 6/6-6/18. On day 7, this was 88% in group A and 89% group B. On day 1, 99% in group A and 98% in group B had <1+ cells in the anterior chamber while on day 7 this increased up to 100%. On day 1, 97% in group A and 98% group B had intraocular pressure less than 20 mmHg. On day 7, it increased up to 100% in both groups. 97% patients in group A and 96% patients in group B had painless surgery. Results were analysed using computer software SPSS version 10.0. Results showed no significant statistical difference between two groups in terms of pain, visual acuity, intraocular pressure, anterior chamber reaction and patient comfort. CONCLUSION: In the hands of expert surgeons and in selected patients, intracameral anesthesia with preservative-free bupivacaine hydrochloride 0.5% is a safe and effective technique of ocular anesthesia for phacoemulsification with posterior chamber intraocular lens implantation.

Aged↗

[Doctoral theses and memoirs about anesthesia. Documents for a history of Spanish anesthesia].

Based on the importance of document files and first-hand bibliographic sources for studying the history, we have recently investigated the chapter of Doctoral Thesis and Reports on anesthetic topics since we believe that these are fundamental to gain insight into the knowledge of our history. This investigation was planned to find such documents by reviewing the data of several Spanish archives and libraries. We collected 80 works: 14 Reports and 66 Doctoral Theses performed during a period of 95 years (heuristic limits 1847-1942). These papers were classified in several subgroups according to the subjects they deal with: 21 works on inhalation anesthesia, 7 on intravenous general anesthesia, 20 on spinal anesthesia, 10 on locoregional, 7 on anesthesia and metabolism, 12 on obstetric anesthesia, and 3 works on varied anesthesia issues. Analysis of these documents revealed that the authors (physicians and Spanish medical corporations) undertook an accurate consideration of the more relevant scientific subjects at the time of their investigation. We conclude that the works analyzed in the present study represented the beginning of the Spanish investigation on anesthesia. Further investigations may contribute to enrich our historiography.

Academic Dissertations as Topic↗

The Thai Anesthesia Incidents Study (THAI Study) on nerve injury associated with anesthesia.

OBJECTIVES: The Thai Anesthesia Incidents Study (THAI Study) database was used to identify the incidence, outcome and contributing factors of nerve injuries associated with anesthesia in Thai people. MATERIAL AND METHOD: A prospective multicenter study was conducted in 20 hospital in Thailand from February 1, 2003 to January 31, 2004. All patients underwent anaesthesia were monitored for nerve injuries during the first 24 hours. The details of nerve injuries were recorded and analysed. RESULTS: The overall incidence of nerve injuries associated with anesthesia was 1.6 per 10,000 patients. Considering on spinal and regional anesthesia, the incidence was 5.2 per 10,000 patients. Lumbosacral roots comprised 65.4% of the injuries, the brachial plexus nerve 11.5%, and femoral nerve 7.7%. Contributing factors included type and duration of surgery and regional anesthesia. CONCLUSION: The incidence of nerve injuries associated with anesthesia in Thailand was 1.5 per 10,000 patients. The spinal anesthesia was predominantly associated with injury of lumbosacral root.

Adolescent↗

[Endocrine reaction pattern: midazolam-fentanyl anesthesia versus inhalation anesthesia].

In a randomised controlled study in 16 orthopaedic patients, the influence of midazolam-fentanyl-N2O/O2 anesthesia (group A) resp. halothane-N2O/O2 anesthesia (group B) on the plasma concentrations of the endocrine parameters ACTH, aldosterone, cortisol, 17-DHEA, insulin, prolactin, T3, T4, TBG (thyroxine bounded globuline) as well as adrenaline, noradrenaline, and dopamine was investigated. Additionally the metabolites glucose, lactate, free glycerin, and acetacetate were measured. Beside prolactin values, only the values for ACTH, aldosterone, cortisol, and 17-DHEA differed with respect to both anesthesia methods. Under halothane-N2O/O2 anesthesia free T4 rose initially also, here represented by T4/TBG-ratio (= FTI). However, the fall of T3 concentration showed no phase - resp. anesthesia-specific changes. Catecholamine levels reached highest values towards the end of operation resp. one hour after extubation in both groups. The insulin secretion, however, was not significantly raised in either group during acute stress phases. As an expression of modified metabolic regulation comparable rises of plasma levels of glucose, lactate, free glycerin, and acetacetate were observed under midazolam-fentanyl-N2O/O2 anesthesia as well as under halothane-N2O/O2. According to presented data, both methods of anesthesia modulated the endocrine metabolic response of the organism to surgical stress, without showing any clinically relevant advantages or disadvantages attributable to either method.

Adult↗

Opioid analgesics in anesthesia: with special reference to their use in cardiovascular anesthesia.

In this article, an attempt has been made to review the use of receptor stimulating pure agonist opioids in anesthesia, especially in patients with cardiovascular disease. Particular emphasis has been placed on the use of opioids in high doses to produce anesthesia, techniques that recently have become popular in cardiovascular anesthesia. A major benefit of opioid anesthesia is the cardiovascular stability obtained during induction and throughout operation, even in patients with severely impaired cardiac function. There is a considerable body of evidence to support this claim when fentanyl is used. Anesthetic doses of morphine are associated with a higher incidence of cardiovascular disturbances and other problems, and, therefore, more attention to detail is required in order to achieve adequate anesthesia and hemodynamic stability. Although other opioids have been used as sole or principal agents in anesthesia for cardiovascular surgery, none have gained widespread acceptance. Meperidine, for example, which is widely used in lower (nonanesthetic) doses as a supplement to nitrous oxide in cardiac and noncardiac surgery, has proved unsuitable because of severe hemodynamic disturbances when high doses are given. However, initial reports concerning two of the newer agonist opioids, sufentanil and alfentanil, suggest that they may prove to be suitable alternatives and perhaps provide advantages over morphine and fentanyl in patients with or without cardiovascular disease. Although cardiovascular stability usually can be assured in the chronically sick cardiac patient with opioid anesthesia, this is not always so with the healthier patient, particularly those presenting for coronary artery surgery. A frequently occurring problem in these patients is hypertension during or after sternotomy, which can result in myocardial ischemia and infarction. The incidence of severe hypertension (increases in systolic blood pressure greater than 20% of control values) can be reduced drastically by increasing the dose of opioid, e.g., up to 140 micrograms/kg of fentanyl. However, despite such large doses, some patients will continue to need treatment with vasodilators, inhalation anesthetics, or other supplements at certain periods during cardiovascular operations. The use of very large doses of opioids also will prolong postoperative respiratory depression. High doses of opioids can reduce or prevent the hormonal and metabolic responses to the stress of surgery. However, even very large doses of fentanyl or its newer analogues do not prevent marked increases in plasma catecholamine concentrations in response to cardiopulmonary bypass.(ABSTRACT TRUNCATED AT 400 WORDS)

Alfentanil↗

Comparison of sequential combined spinal-epidural anesthesia and spinal anesthesia for cesarean section.

AIM: The aim of our study was to prove that by using sequential combined spinal-epidural (CSE) anesthesia it is possible to overcome the limits connected to the use of spinal anesthesia (SA) alone for elective cesarean section. METHODS: We examined 100 women submitted to cesarean section; SA was administered to 50 patients and sequential CSE technique to the other 50. In every woman before execution of the anesthesia we infused 500 mL of a plasma expander and a previous administration of 5 mg of ephedrine. The CSE was executed at the L1-L2 intervertebral space, administering in spinal anesthesia 5 mg of levobupivacaine with 5 _g of sufentanil, and in peridural anesthesia 10-12 mL of levobupivacaine 0.25% according to the patient's height. The peridural catheter for postoperative analgesia was then positioned. In the group of women submitted only to SA, 7.5-8 mg of levobupivacaine was injected, according to the patient's height, in the L1-L2 intervertebral space, with 5 _g of sufentanil. We considered the following adverse effects: hypotension; bradycardia; vomiting; intraoperative discomfort and motor block. RESULTS: The results obtained showed that, with a P < or = 0.05, the incidence of motor block (P < 0.001), discomfort (P < 0.001) and hypotension (P = 0.021) in the SA group is greater than in the CSE group. The difference in the incidence of vomiting (P = 0.147) and bradycardia (P = 0.067) between the 2 groups is not statistically significant. CONCLUSIONS: In our opinion sequential CSE can be considered an important step forward in the regional anesthesia used for elective cesarean section.

Anesthesia, Epidural↗

[Experience with continuous epidural anesthesia used in the complex of combined anesthesia at gastropancreatoduodenal surgery].

The purpose of this study was to assess the experience with long-term epidural space administration of 1% lidocaine in combination with general anesthesia. Anesthesia based on the long-term epidural lidocaine administration in combination with general anesthesia versus total intravenous anesthesia based in ketamine and ataralgesia was analyzed. The anesthesia based on the long-term epidural lidocaine administration in combination with general anesthesia was shown to provide steady-state hemodynamic parameters and an adequate antinociceptive protection and to contribute to the early activation of patients.

Adult↗

[Does propofol have advantages over midazolam and isoflurane? Comparative study of 2 total intravenous anesthesia techniques using midazolam and propofol, versus balanced anesthesia with isoflurane].

OBJECTIVES: To compare two techniques for total intravenous anesthesia (TIVA): midazolam-alfentanil-flumazenil and propofol-alfentanil, contrasting them with combined anesthesia (thiopental-isoflurane-alfentanil) and assessing the efficacy of flumazenil in continuous perfusion for preventing resedation in TIVA with midazolam. PATIENTS AND METHODS: The efficacy and clinical tolerance of the 3 anesthetic techniques with propofol, midazolam or isoflurane were studied in 63 patients undergoing elective breast, lumbar or gynecological surgery. Anesthetic induction was achieved with midazolam 0.3 mg/kg-1 (group M), propofol 2.5 mg/kg-1 (group P) or thiopental 3 mg/kg-1 (group I); all patients also received 50 micrograms/kg-1 alfentanil and vecuronium bromide 0.12 mg/kg-1/h-1. Maintenance was achieved with midazolam in perfusion at 0.12 mg/kg-1/h-1 (group M); propofol in perfusion at 7 mg/kg-1/h-1 and a pre-incision dose of 1.5 mg/kg-1 (group P); and isoflurane at 1.15% (group I). The 3 groups also received one pre-incision dose of alfentanil 25 micrograms/kg-1 and post-incision perfusion at 60 micrograms/kg-1/h-1. The infusion of alfentanil was changed by amounts of 20 micrograms/kg-1/h-1 in accordance with the patient's response to surgery. After surgery patients in group M received flumazenil 0.5 mg i.v. over 30 sec and a perfusion of flumazenil 0.5 mg over 60 min. Parameters indicating efficacy were: 1) total dose and timing of alfentanil; 2) number of instances of inadequate anesthesia; 3) peri-operative amnesia; 4) times of awakening and extubation after surgery, and 5) the number of patients in each group who required naloxone. Parameters indicating tolerance were: 1) hemodynamic variables; 2) the number of postoperative desaturations; 3) level of sedation, comprehension and motor coordination and orientation; 4) the "G/g detection" test and the memory recall test; 5) adverse side effects; 6) need for postoperative analgesia, and 7) evaluation of the anesthetic technique. RESULTS: The 3 techniques afforded effective control of hemodynamic response to intubation and surgical incision. Anesthetic maintenance was easy and safe with isoflurane and propofol. Higher doses of alfentanil, however, were needed with midazolam and we found a higher incidence of signs of superficial anesthesia. Reversion of midazolam with flumazenil 0.5 mg i.v. produced earlier awakening, although this was followed later by relapse into hypno-sedation that could not be prevented with a perfusion of flumazenil. Although recovery from anesthesia was slower with propofol than with isoflurane, we observed no differences in level of sedation, motor coordination and postoperative comprehension. Maintenance with isoflurane produced a higher incidence of adverse side effects such as tremors and nausea after surgery. CONCLUSIONS: None of the TIVA techniques proved superior in all the parameters studied during anesthetic maintenance when compared with balanced isoflurane-alfentanil, although the propofol-alfentanil combination was found to be superior to that of midazolam-alfentanil. After anesthesia, however, recovery was better with the association of propofol-alfentanil and adverse side effects were fewer. Flumazenil at the doses used was ineffective for preventing resedation due to midazolam.

Adolescent↗

Cerebellar nitric oxide is increased during isoflurane anesthesia compared to halothane anesthesia: a microdialysis study in rats.

BACKGROUND: This study examined the influences of isoflurane versus halothane anesthesia on basal and agonist-stimulated nitric oxide in the cerebellum of intact rats. Nitric oxide was measured using the hemoglobin-trapping method in an in vivo microdialysis technique. This method uses the stoichiometric reaction of nitric oxide with oxyhemoglobin to produce methemoglobin and nitrate; the change in methemoglobin concentration is measured spectrophotometrically to estimate nitric oxide concentration. METHODS: Male Wistar rats were anesthetized with isoflurane (1.4%) or halothane (1.2%), mechanically ventilated and paralyzed (intravenous pancuronium, 1 mg/kg). Microdialysis probes were implanted into the cerebellum. Bovine oxyhemoglobin dissolved in artificial cerebrospinal fluid was pumped through the probe (2 microl/min) and assayed at 15-min intervals. The glutamatergic agonist, kainic acid (KA, 5 mg/kg, intraarterially), was used to stimulate nitric oxide production. NG-nitro L-arginine methyl ester (L-NAME, 40 mg/kg, intravenously) was used to inhibit nitric oxide synthase. RESULTS: Unstimulated cerebellar nitric oxide concentrations were stable and greater during anesthesia with isoflurane (532+/-31 nM; mean +/- SEM) than with halothane (303+/-23 nM). L-NAME pretreatment reduced nitric oxide concentrations during isoflurane, but not halothane, anesthesia. Infusion of KA increased nitric oxide in both groups; however, the increase in nitric oxide was significantly greater during isoflurane anesthesia. Pretreatment with L-NAME inhibited the response to KA in both groups. CONCLUSIONS: Nitric oxide production in the cerebellum, monitored by microdialysis, was greater during isoflurane anesthesia than during halothane anesthesia. Increased nitric oxide production during isoflurane anesthesia would be expected to impact central neuronal function and cerebral blood flow and vascular resistance.

Anesthetics, Inhalation↗