SEARCH · PubMed Health

Results for “Intraoperative Awareness”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources

PubMed2006

Sensitivity and specificity of intraoperative recurrent laryngeal nerve stimulation test for predicting vocal cord palsy after thyroid surgery.

INTRODUCTION: Recurrent laryngeal nerve (RLN) palsy after thyroidectomy, although infrequently encountered, can decrease quality of life. In addition to the hoarseness that occurs with unilateral RLN palsy, bilateral RLN palsy leads to dyspnea and often to life-threatening glottal obstruction. Therefore, intraoperative awareness of the nerve's status is of great importance. This study examined the sensitivity and specificity of a palpation technique to detect contraction of the posterior cricoarytenoid muscle (PCA) through the posterior hypopharyngeal wall while the RLN was being stimulated with a disposable nerve stimulator during thyroid surgery (the laryngeal palpation test) to predict postoperative RLN deficits. METHODS: A total of 2197 RLNs in 1376 patients were identified to be at risk of injury during thyroidectomy performed between July 2003 and August 2004. Postoperative RLN integrity was assessed using direct laryngoscopy or laryngofiberoscopy to visualize vocal fold mobility. RESULTS: Altogether, 76 RLNs failed to elicit a PCA contraction in response to nerve stimulation, and 80 cases of temporary vocal cord palsy and 21 cases of permanent vocal cord palsy were recognized on postoperative evaluation. For postoperative vocal cord palsy, the sensitivity and specificity of the laryngeal palpation test were 69.3% and 99.7%, respectively, with a positive predictive value of 92.1% and negative predictive value of 98.5%. For permanent vocal cord palsy, the sensitivity and specificity were 85.7% and 97.3%, respectively, with a positive predictive value of 23.7% and negative predictive value of 99.8%. CONCLUSIONS: The laryngeal palpation test is not a particularly useful method for predicting the level of RLN function after thyroidectomy. All patients must be examined postoperatively by direct laryngoscopy or laryngofiberoscopy to check vocal cord mobility. Even if there is no contraction of the PCA and we detect vocal cord palsy immediately after surgery, vocal cord palsy often recovers within 1 year when visual preservation of RLN is successful.

Adolescent↗

PubMed2006

Comparison of the EEG-based SNAP index and the Bispectral (BIS) index during sevoflurane-nitrous oxide anaesthesia.

The BIS monitor (Aspect Medical Inc, Newton, USA) was the first electroencephalogram (EEG)-based monitor of the hypnotic effect reflected by a dimensionless figure ranging from 100 (awake state) to 0 (flat line EEG). Its widespread use makes it the most-studied and the best-known among same intended devices. Its algorithm processes low-frequency EEG oscillations in order to provide the Bispectral index. A BIS index ranging from 40 to 60 has been established as the proper for surgical performance. The BIS monitor permits a closer approach to the hypnotic component of anaesthesia beyond clinical signs and may reduce the probability of intraoperative awareness; therefore, it has become a recommended monitoring tool in routine practice. The SNAP monitor (Nicolet Biomedical, Madison WI, USA) is also intended for monitoring the hypnotic effect of anaesthetics, which is in turn displayed as an index ranging from 100 to 0, with 100 meaning a fully awake state and 0 meaning no brain activity. The algorithm of the SNAP monitor is featured by its additional processing of ultra-high EEG frequencies, which seem to be involved in the formation of consciousness. The use of these frequencies would theoretically improve responsiveness during increased brain activity. We studied its behaviour patterns and capability to monitor the hypnotic effect induced by sevoflurane-nitrous oxide by comparison with the BIS index. Seventy patients ASA I-III were induced with propofol, fentanyl and rocuronium, and maintained with sevoflurane-N(2)O. BIS and SNAP indices were simultaneously recorded before induction, after intubation, after incision, at the following 10, 30 and 50 minutes, awakening and extubation time points, together with heart rate and blood pressure. The Pearson correlation was R(2) = 0.68 (p < .05). The Bland and Altman test showed a bias of 14.3 for SNAP index values with respect to BIS index values. We concluded that the SNAP index correlates with variations in the hypnotic effect induced by sevoflurane-nitrous oxide anaesthesia when compared with the BIS index. In this context, a SNAP index ranging from 58 to 70 would be equivalent to the BIS index range 40 to 60 and, therefore, the accurate for surgical performance.

Adult↗

PubMed1984

Hormonal and haemodynamic responses to upper abdominal surgery during isoflurane and balanced anaesthesia.

The purpose of the study was to compare the protective role of different anaesthetic techniques against surgical stress. Sixty patients undergoing elective laparotomy were randomly divided into six groups of ten patients each: Group I was given 0.65 MAC nitrous oxide (66 per cent inspired) and 0.65 MAC isoflurane (0.75 per cent end-expired); Group II was given 0.65 MAC nitrous oxide and 1-1.2 MAC isoflurane (1.2-1.4 per cent end-expired); Group III was given the same anaesthetic management as patients in Group I but with the addition of fentanyl (2 micrograms X kg-1) before the skin incision and 1/8 of the initial dose every 15 minutes during surgery; Group IV was treated as patients in Group I with an additional infusion of lidocaine (30 micrograms X kg-1 X min-1); Groups V and VI were given 0.65 MAC of nitrous oxide and fentanyl, 7.5 and 15 micrograms X kg-1, respectively, before skin incision with 1/8 of the initial dose every 15 minutes during the operation; diazepam, 5 mg IV each hour of surgery, was given to prevent intraoperative awareness. Cortisol concentration was determined by radioimmunoassay method and catecholamines were measured by high performance liquid gas chromatography in blood samples taken at different stages perioperatively. All patients had satisfactory haemodynamic courses of anaesthesia. Statistically significant increases in both epinephrine and norepinephrine concentrations were observed during the immediate postoperative period in Group I patients only. Haemodynamic stability was maintained despite a two- to three-fold increase in cortisol which occurred during the operation and immediate postoperative period.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Effects of benzodiazepines on mid-latency auditory evoked potentials.

Midlatency auditory evoked potentials (MLAEP) reflect primary cortical processing of auditory stimuli. The effects of benzodiazepines on MLAEP have not yet been studied. We examined the effects of intravenous induction of general anaesthesia using the benzodiazepines midazolam, diazepam and flunitrazepam on MLAEP in 30 patients scheduled for minor gynaecological procedures. Anaesthesia was induced with midazolam (0.2-0.3 mg.kg-1, Group I, n = 10), diazepam (0.3-0.4 mg.kg-1, Group II, n = 10) or flunitrazepam (0.03-0.04 mg.kg-1, Group III, n = 10). Auditory-evoked potentials were recorded before and five to ten minutes after induction of general anaesthesia. Latencies of the peak V, Na, Pa, Nb and Pl (ms) and amplitudes Na/Pa, Pa/Nb and Nb/P1 (microV) were measured. In the awake state, MLAEP had high peak to peak amplitudes and a periodic waveform. After induction of anaesthesia there was no or only a small increase in latencies of the peaks Na, Pa, Nb and P1, which was significant only for P1 in the midazolam group. Amplitudes Na/Pa, Pa/Nb and Nb/P1 decreased only slightly and which reached statistical significance only for Na/Pa in the flunitrazepam group. The MLAEPs do not change markedly in amplitude or latency during induction of general anaesthesia with benzodiazepines. Primary cortical processing of auditory stimuli seems to be preserved under benzodiazepines. This may be seen in connection with cases of intraoperative awareness and especially the perception of auditory stimuli during anaesthetic regimens where benzodiazepines are used to suppress consciousness.

Acoustic Stimulation↗

PubMed2001

The attitude of the general public towards preoperative assessment and risks associated with general anesthesia.

PURPOSE: To survey the general public's attitude towards preoperative assessment and commonly perceived fears about general anesthesia. METHODS: A province wide telephone survey was conducted in Alberta. General and regional anesthesia were defined, a scenario involving major knee surgery was described, and participants were asked to choose between regional and general anesthesia. Respondents used a seven-point scale to rate the importance of seeing an anesthesiologist preoperatively and were questioned about the timing of such a visit. Attitudes towards commonly perceived fears associated with anesthesia were also assessed. RESULTS: A total of 1,216 people were surveyed. Over 30% of respondents felt that it was very important to see an anesthesiologist preoperatively, with a total of over 60% attributing a high degree of importance to this. Fifty percent felt that this assessment should occur on the day prior to surgery. A preference for regional or general anesthesia was not expressed in the situation. Approximately 20% of respondents were very concerned about brain damage, waking up intraoperatively and memory loss. Twelve percent were concerned about dying intraoperatively. Nine percent expressed concern about postoperative pain, with 12% reporting being concerned about nausea and vomiting. CONCLUSIONS: The general public considers anesthetic assessment on the day prior to surgery an important part of preoperative preparation. Fears of brain damage, death and intraoperative awareness associated with general anesthesia remain prevalent, suggesting that preoperative education of patients should address these concerns. The general population was less concerned about realistic fears such as nausea, vomiting and postoperative discomfort.

Adult↗

PubMed1998

[Sevoflurane and the nervous system].

During sevoflurane anaesthesia cerebral blood flow is preserved or slightly decreased. Cerebral oxygen consumption is reduced to 50% under 1 MAC sevoflurane. Autoregulation of cerebral blood flow and responsiveness of cerebral blood flow to changes in Pa CO2 are widely preserved. Sevoflurane produces a dose dependent increase in intracranial pressure and a decrease in cerebrovascular resistance that can not be observed under hypocapnic conditions. Central stimulus processing, the electroencephalogram and sensory evoked potentials are suppressed under sevoflurane in a dose dependent fashion. The electrophysiological data indicate that intraoperative awareness phenomena should be suppressed with sevoflurane 1.5-2.0 vol.%. Recovery of cognitive and psychomotor functions seems to be faster and more complete after sevoflurane than after isoflurane anaesthesia. In inducing seizure like EEG or muscle activity, sevoflurane seems to be comparable with isoflurane. There is no limitation of sevoflurane use in patients with concomitant psychiatric or neurological diseases, and sevoflurane may be valuable addition in neurosurgery or carotid surgery.

Anesthetics, Inhalation↗

PubMed2004

[Nitrous oxide. Sense or nonsense for today's anaesthesia].

Nitrous oxide has been used in addition to other volatile anaesthetics to provide general anaesthesia and short time sedation for more than 150 years. However, the exact mechanisms of action remain unclear. For decades nitrous oxide was considered to be the ideal anaesthetic because of his favourable physical properties and low cardiovascular side effects. However, the known side effects of nitrous oxide as well as the implementation of new anaesthetic agents and short acting opiates led to more and more criticism about the administration of this gas. Nitrous oxide is still frequently used for mask induction primarily in paediatric anaesthesia and gynaecology. However, recent studies have shown that omitting nitrous oxide can also be a risk factor because of an increased susceptibility to intraoperative awareness. Careful consideration of the illustrated contraindications and side effects as well as the available alternatives, shows that nitrous oxide is still an option in general anaesthesia.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗

PubMed1994

[Total i.v. anesthesia with S-(+)-ketamine in orthopedic geriatric surgery. Endocrine stress reaction, hemodynamics and recovery].

UNLABELLED: Clinically-used ketamine is a racemic mixture of two isomers, S-(+)- and R-(-)-ketamine. Previous investigations showed the anaesthetic potency of S(+)-ketamine to be three times higher than that of R-(-)-ketamine. It was the aim of this study to compare the effects of S-(+)-ketamine and racemic ketamine on endocrine and cardiovascular parameters, recovery, and side effects in geriatric patients during total intravenous anaesthesia (TIVA) for orthopaedic surgery. METHODS: Forty patients over 60 years of age scheduled for elective hip or knee replacement were investigated in a double-blind, randomised design. For induction of TIVA, patients received 0.1 mg midazolam, 0.5 mg atropine, 1 mg/kg S(+)-ketamine or 2 mg/kg racemic ketamine, respectively, 2 mg vecuronium, and 1.5 mg/kg suxamethonium. After intubation and relaxation with a total dose of 0.1 mg/kg vecuronium, a continuous infusion of 2 mg/kg per hour S-(+)- or 4 mg/kg per hour racemic ketamine was administered throughout surgery. Blood samples were taken through a central venous catheter at seven time-points, before induction as well during and after surgery, until the 1st postoperative morning for analysis of adrenaline, noradrenaline (by high-pressure liquid chromatography with electrochemical detection), anti-diuretic hormone (ADH), adrenocorticotropic hormone (ACTH), cortisol (by radioimmunoassay), glucose, and lactate. In addition, systolic arterial pressure (SAP), heart rate (HR), and arterial oxygen saturation were measured, and the time intervals between the end of ketamine infusion and the return of consciousness and orientation were protocolled. The incidence and assessment of dreams and other side effects were reported by the patients. RESULTS: Biometric data of the groups were comparable, the mean age of both groups being 68 years. Plasma adrenaline, noradrenaline, ADH, ACTH, cortisol, and glucose as well as SAP and HR increased significantly (P < 0.05) during the course of anaesthesia. The influence on lactate levels was not significant. There were no differences between S(+)- and racemic ketamine with respect to these parameters. Three patients in the ketamine-racemate group showed severe arterial hypertension and were withdrawn from the study. Recovery clearly improved after administration of S(+)-ketamine compared to the racemate. Simple orders were followed after 2.0 +/- 3.4 versus 4.9 +/- 6.8 min (P = 0.07), orientation with respect to person returned after 5.7 +/- 4.0 versus 14.6 +/- 10.0 min (P < 0.001) and spatial orientation after 8.2 +/- 5.4 versus 17.4 +/- 9.7 min (P < 0.001). After racemic ketamine, 1 patient remembered a negative dream and 1 patient a positive dream. In the S(+)-group, 1 positive dream was reported. No intraoperative awareness was reported, and all patients would accept the same anaesthesia again. CONCLUSIONS: Increases in cardiovascular parameters and insufficient reduction of the stress response with respect to ADH, ACTH, and cortisol seem to require a more potent hypnotic element during TIVA with ketamine. With regard to endocrine and cardiovascular parameters, the pharmacodynamic effects of racemic and S-(+)-ketamine were comparable. Because of the significant improvement in recovery and the reduced quantitative drug load, S-(+)-ketamine offers a clinical advantage compared with currently used racemic ketamine.

Aged↗

PubMed2005

Nitrous oxide: a unique drug of continuing importance for anaesthesia.

Early attempts to use nitrous oxide as a sole anaesthetic foundered because of its low potency. It has been used successfully as an adjunct to more potent anaesthetics, however, since 1868. By enabling reduced doses of more potent anaesthetics, nitrous oxide reduces the cost of anaesthesia and limits cardiorespiratory side effects. Nitrous oxide does increase the incidence of postoperative nausea and vomiting in cases where risk of this side effect is increased, but it seems likely that use of antiemetics prophylactically will negate this factor. Perhaps the greatest argument for the continued use of nitrous oxide is that it reduces the incidence of recall of intraoperative awareness. Reduced pharmacokinetic variability compared with other anaesthetics, especially intravenous agents, is likely to be a most important reason for this, although evidence is emerging that nitrous oxide also has pharmacodynamic advantages. There are specific situations in which nitrous oxide should not be used, but in the absence of these, its use can be favourably recommended.

Anesthesia, Inhalation↗

PubMed2006

Update on bispectral index monitoring.

Since 1997, bispectral index (BIS; Aspect Medical Systems Inc., Natick, MA) has been in clinical practice and a wealth of experimental research has accumulated on its use. Originally, the device was approved only for monitoring hypnosis and has now received an indication for reducing the incidence of intraoperative awareness during anesthesia. Numerous studies have documented the ability of BIS to reduce intermediate outcomes such as hypnotic drug administration, extubation time, postoperative nausea and shortened recovery room discharge. Two recent large-scale outcome studies using BIS (one randomized controlled trial and one prospective, nonrandomized historical cohort study) identified an approximately 80% reduction in the incidence of recall after anesthesia. BIS provides clinicians with unique information that can be used to tailor hypnotic drug doses to individual patient requirements. BIS does not predict movement or hemodynamic response to stimulation, nor will it predict the exact moment consciousness returns. This review will also discuss other BIS applications including use in pediatrics, intensive care and for procedural sedation. Some limitations exist to the use of BIS and it is not useful for some individual hypnotic agents (ketamine, dexmedetomidine, nitrous oxide, xenon, opioids). BIS technology is moving out of the operating room and into diverse environments where conscious and deep sedation are provided. Anesthesiologists need to be actively involved in promoting patient safety and helping transition this technology into broader use.

Adult↗

PubMed2006

Evidence of acute tolerance to remifentanil in intensive care but not in anesthesia.

We report the case of a 19-year-old man with a drug abuse history, admitted to the intensive care unit for head and chest trauma, who experienced an acute tolerance to sedative and respiratory depression effects of remifentanil, which was given as the sole agent for sedation. He did not exhibit any signs of drug tolerance or intraoperative awareness during prolonged remifentanil-based anesthesia using propofol or sevoflurane as adjuvants. Several recent studies support the hypothesis of a possible involvement of N-methyl-d-aspartate glutamate receptors. The clinical relevance of this report is that if a patient with a previously acute tolerance to remifentanil during sedation undergoes long-term surgery, and propofol or sevoflurane is coadministered in a remifentanil-based anesthesia, the patient will not necessarily develop opioid tolerance. It is of interest for anesthesiologists, given the high frequency of patients with drug abuse history who are admitted to intensive care units, often sedated with remifentanil, who undergo anesthesia for emergency surgery.

Adjuvants, Anesthesia↗

PubMed1996

Morbidity outcome in early versus conventional tracheal extubation after coronary artery bypass grafting: a prospective randomized controlled trial.

INTRODUCTION: We undertook a prospective, randomized, controlled clinical trial to evaluate morbidity outcomes and safety of a modified anesthetic technique to provide shorter sedation and early extubation (1 to 6 hours) than those of the conventional anesthetic protocol used for prolonged sedation and extubation (12 to 22 hours) in patients after coronary artery bypass grafting. METHODS: One hundred twenty patients undergoing elective coronary artery bypass grafting were prospectively assigned randomly to either an early extubation group (n = 60; 15 micrograms.kg-1 fentanyl and 2 to 6 mg.kg-1.hour-1 propofol and isoflurane) or to a conventional extubation group (n = 60; 50 micrograms.kg-1 fentanyl and 0.1 mg.kg-1 midazolam and isoflurane). Cardiac morbidity (postoperative myocardial ischemia, postoperative myocardial infarction, and perioperative sympathoadrenal stress response), respiratory morbidity (postextubation apnea, alveolar-arterial oxygen gradient, pulmonary shunting, oxygen consumption, atelectasis, and reintubation), hemodynamic values and vasoactive medication requirements, intraoperative awareness, postoperative cognitive function, 30 day mortality, and intensive care unit and hospital lengths of stay were compared between the two groups. RESULTS: Fifty-one of the 60 patients in each group (85%) were extubated within the defined time period. Postoperative extubation time and intensive care unit and hospital lengths of stay were significantly shorter in the early group. At 48 hours after operation, there were no significant differences between the two groups in myocardial ischemia incidences, ischemia burdens, or creatine kinase isoenzyme MB levels. Four patients in the conventional group, but not in the early group, had postoperative myocardial infaction. The extubation anesthetics used were effective in suppressing the perioperative plasma catecholamine stress response in both groups. Postextubation apnea characteristics were similar between the groups. Intrapulmonary shunt fraction improved significantly in the early group at 4 hours after extubation. The incidences and degree of atelectasis did not differ significantly between the two groups. The incidences of treated postoperative complications were comparable between the two groups, but three patients in the conventional group died as a result of stroke or postoperative myocardial infarction. CONCLUSION: Early extubation after coronary artery bypass grafting is safe and does not increase perioperative morbidity. There is an improvement in postextubation intrapulmonary shunt fraction and a reduction in intensive care unit and hospital lengths of stay.

Aged↗

PubMed1995

Propofol-fentanyl versus isoflurane-fentanyl anesthesia for coronary artery bypass grafting: effect on myocardial contractility and peripheral hemodynamics.

To avoid intraoperative awareness and postoperative respiratory depression from high-dose opioid anesthesia, propofol (P), or isoflurane (I) has been combined with moderate-dose opioid with varying results. However, the effects of both P and I on myocardial contractility and left ventricular afterload have not been completely quantified. The end-systolic pressure-diameter relationship (ESPDR) of the left ventricle (LV) is a reliable method to quantitatively assess LV contractility because it is relatively independent of changes in preload and incorporates afterload changes. The purpose of this study was to quantify the cardiodynamic effects of propofol-fentanyl (PF) anesthesia in comparison with isoflurane-fentanyl (IF) anesthesia in patients undergoing coronary artery bypass grafting (CABG). Thirty patients with normal or moderately impaired LV function (ejection fraction > or = 40% with LV end-diastolic pressure < or = 18 mmHg, no preoperative akinesia or dyskinesia) undergoing elective CABG were studied. After premedication with flunitrazepam, 2 mg orally, all patients were induced with thiopental, 1 mg/kg, fentanyl, 20 micrograms/kg, and vecuronium, 0.1 mg/kg, and were ventilated with oxygen/air (F(1)O2 0.6). Anesthesia was maintained throughout the procedure with a zero-order intravenous (IV) continuous infusion of P, 3 mg/kg/h (PF group), or with isoflurane inhalation of 0.6% (IF group), supplemented by intermittent boluses (5 micrograms/kg) of fentanyl (up to a total maintenance dose of 30 micrograms/kg). After intubation, a cross-section of the LV was visualized by two-dimensional transesophageal echocardiography and an m-mode echocardiogram was obtained at the maximum anterior-posterior diameter. The radial artery pressure tracing and the ECG were simultaneously recorded with the M mode.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2000

Comparison of two different anesthesia regimens in patients undergoing aortocoronary bypass grafting surgery: sufentanil-midazolam versus remifentanil-propofol.

OBJECTIVE: To compare intraoperative hemodynamics and depth of anesthesia using sufentanil-midazolam (SM) versus remifentanil-propofol (RP) anesthesia. DESIGN: Prospective, randomized study. SETTING: Clinical investigation in an urban, university-affiliated hospital. PARTICIPANTS: Forty patients undergoing elective first-time coronary artery bypass graft surgery. INTERVENTIONS: Twenty patients were anesthetized using SM and 20 patients using RP. MEASUREMENTS AND MAIN RESULTS: Hemodynamic monitoring included a 5-lead electrocardiogram, a radial artery catheter, and a pulmonary artery catheter. Depth of anesthesia was assessed using bispectral index (BIS). Data were obtained after induction of anesthesia (T1), after sternotomy (T2), after pericardiotomy (T3), 5 minutes after cardiopulmonary bypass (CPB) (T4), after closure of thorax (T5), and at the end of surgery (T6). The 2 groups were comparable with regard to demographic and perioperative data. There were no significant differences of any hemodynamic parameter at any time between the 2 groups. In both groups, systemic vascular resistance increased at T2 and decreased at T4 from baseline value (p < 0.05). Cardiac index increased at T4 in both groups from baseline value (p < 0.05); 55% of the patients of both groups needed low-dose dobutamine after CPB. During CPB, 40% of the RP patients needed norepinephrine versus 35% of the SM patients. BIS was lower in the RP than in the SM group at T2 and T3 (p < 0.05). BIS values indicating intraoperative awareness were not noted. CONCLUSION: Both anesthesia regimens provided stable hemodynamics and adequate anesthesia in patients undergoing coronary artery bypass graft surgery.

Aged↗

PubMed2002

Patients' conscious recollections from cardiac anesthesia.

OBJECTIVE: To estimate the current incidence of conscious recollections from the time of anesthesia, the contribution of anesthetic drugs to this incidence, and the patients' experience of cardiac anesthesia and surgery. DESIGN: Prospective, horizontal survey of cardiac surgery patients using structured interview method. SETTING: Tertiary care university hospital. PARTICIPANTS: All cardiac surgery patients during 1 year (n = 1,218). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Of 1,218 patients operated on, 929 were interviewed. The patients' memories were classified to estimate the number of patients with possible or definite intraoperative awareness and later conscious recall. The use of anesthetics was estimated from anesthetic charts for patients with awareness and recall and control patients. These charts were compared using Poisson regression. The incidence of definite awareness with recall was 0.5% (5 patients), and the incidence of possible recall was 2.3% (21 patients). A lower dose of midazolam was used for the patients with awareness and recall. Only 1 patient rated the experience of awareness as the worst perioperative memory. Benzodiazepine premedication caused amnesia for the preoperative period but not for the time of anesthesia. CONCLUSION: The incidence of awareness and recall is similar to the incidence reported during general surgery. Cardiac surgery does not carry increased risk of awareness. Benzodiazepines given during anesthesia are effective in decreasing the incidence of recalled awareness, and the experience of awareness is not often particularly traumatizing. Premedication with benzodiazepine is not effective in preventing recollection of anesthesia, however.

Aged↗

PubMed1993

[Mid-latency auditory evoked potentials during increasing doses of fentanyl].

OBJECTIVE: Intraoperative awareness, and especially the perception of auditory stimuli occur occasionally under general anaesthesia with high-dose opioids. Mid-latency auditory evoked potentials (MLAEP) reflect the primary cortical processing of auditory stimuli. Hence, we studied the effects of fentanyl on MLAEP. METHODS: Institutional approval and informed consent was obtained in 20 patients scheduled for cardiac surgery. Anaesthesia was induced with fentanyl (10 micrograms/kg every 7[ up to a total dosage of 50 micrograms/kg). Auditory evoked potentials were recorded before and 5[ after every fentanyl dose on vertex (positive) and mastoids on both sides (negative). Auditory clicks were presented binaurally at 70 dBnHL at a rate of 9.3 Hz. Using the electrodiagnostic system Pathfinder I (Nicolet), 1000 successive stimulus responses were averaged over a 100 ms post-stimulus interval and analysed off-line. Latencies of the peak V, Na, Pa, Nb P1 and amplitudes Na/Pa, Pa/Nb, Nb/P1 were measured. V belongs to the brainstem generated potentials, which demonstrates that auditory stimuli were correctly transduced. Na, Pa, Nb, P1 are generated in the primary auditory cortex of the temporal lobe and are the electrophysiological correlate of the primary cortical processing of the auditory stimuli. By means of a Fast-Fourier transformation power spectra of the AEP were calculated. RESULTS: In the awake state AEP peak latencies were in the normal range. Power spectra indicated high energy in the 30-40 Hz frequency range. During increasing dosages of fentanyl the brainstem response V was stable. P1 increased in latency and Nb/P1 decreased in amplitude after 10 micrograms/kg of fentanyl significantly. The primary cortical potentials Na, Pa, Nb changed only very slightly in latencies or amplitudes even under highest doses of fentanyl (50 micrograms/kg) and could be identified like in the awake patients. In the power spectra high energy persisted in the 30 Hz frequency range. CONCLUSION: MLAEP and especially the primary cortical potentials Na, Pa, Nb did not change markedly in amplitude or latency during high-dose fentanyl analgesia. There is no dose-dependent effect of fentanyl on MLAEP as it can be observed under volatile anaesthetics (isoflurane, enflurane). The primary cortical processing of auditory stimuli can be completely blocked by volatile anaesthetics, but is still preserved under highest doses of fentanyl. This may be seen in connection with cases of awareness and perception of auditory stimuli during high-dose fentanyl analgesia.

Aged↗

PubMed2002

Randomized, double-blind comparison of different inspired oxygen fractions during general anaesthesia for Caesarean section.

BACKGROUND: The optimal inspired oxygen fraction FI(O(2)) for fetal oxygenation during general anaesthesia for Caesarean section is not known. METHODS: We randomized patients having elective Caesarean section to receive one of the following: FI(O(2)) 0.3, FI(N(2))(O) 0.7 and end-tidal sevoflurane 0.6% (Group 30, n=20); FI(O(2)) 0.5, FI(N(2))(O) 0.5 and end-tidal sevoflurane 1.0% (Group 50, n=20), or FI(O(2)) 1.0 and end-tidal sevoflurane 2.0% (Group 100, n=20) until delivery. Neonatal outcome was compared biochemically and clinically. RESULTS: At delivery, for umbilical venous blood, mean PO(2) was greater in Group 100 (7.6 (SD 3.7) kPa) compared with both Group 30 (4.0 (1.1) kPa, P<0.0001) and Group 50 (4.7 (0.9) kPa, P=0.002) and oxygen content was greater in Group 100 (17.2 (1.6) ml dl(-1)) compared with both Group 30 (12.8 (3.6) ml dl(-1), P=0.0001) and Group 50 (13.8 (2.6) ml dl(-1), P=0.0001). For umbilical arterial blood, PO(2) was greater in Group 100 (3.2 (0.4) kPa) compared with Group 30 (2.4 (0.7) kPa, P=0.003), and in Group 50 (2.9 (0.8) kPa) compared with Group 30 (2.4 (0.7) kPa, P=0.04); oxygen content was greater in Group 100 (10.8 (3.5) ml dl(-1)) than in Group 30 (7.0 (3.0) ml dl(-1), P<0.01). Apgar scores, neonatal neurologic and adaptive capacity scores, and maternal arterial plasma concentrations of epinephrine and norepinephrine before induction and at delivery were similar among groups. No patient reported intraoperative awareness. CONCLUSIONS: Use of FI(O(2)) 1.0 during general anaesthesia for elective Caesarean section increased fetal oxygenation.

Adult↗

PubMed2003

Plasma propofol concentration and EEG burst suppression ratio during normothermic cardiopulmonary bypass.

BACKGROUND: During cardiopulmonary bypass (CPB), several factors affect drug disposition and action. This topic has not been studied extensively during normothermic CPB. In this study, we related propofol dose to plasma propofol concentration and burst suppression of the EEG during normothermic bypass. METHODS: After institutional approval and informed consent, 45 patients having cardiac surgery were assigned randomly to receive propofol infusions at 4 (Group A), 5 (Group B) and 6 (Group C) mg kg(-1) h(-1) during normothermic CPB. In all patients, small to moderate doses of fentanyl were also administered. Plasma propofol concentration and burst suppression ratio (BSR) were measured at the following times: (1) 10 min before CPB, (2) 10 min after the start of CPB, (3) 30 min after the start of the CPB, (4) just after aortic declamping, and (5) 60 min after CPB. RESULTS: At baseline, plasma propofol concentrations were similar among the three groups. After the start of CPB, the concentrations of propofol decreased significantly by 41, 35, and 30% of control values in Groups A, B, and C, respectively. In Group A, the concentration of propofol during CPB remained unchanged at less than the concentration before bypass. In Groups B and C, plasma propofol concentrations gradually increased during CPB to the pre-bypass concentrations. In Group A, BSR values did not change significantly during CPB. In Groups B and C, BSR values gradually increased and became significantly greater than baseline values. No patient reported intraoperative awareness. CONCLUSION: The pharmacokinetics and pharmacodynamics of propofol change during normothermic CPB. During normothermic CPB, the efficacy of propofol may be enhanced compared with before CPB.

Adult↗