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PubMed1993

Intraoperative awareness and recall during total hip arthroplasty.

A case of intraoperative recall and awareness in a patient with sickle cell disease who had received midazolam, 10 mg at induction of anesthesia, is reported. The patient was on opioids which may also have caused tolerance. Although the use of midazolam may have been judged to provide adequate amnesia, this was clearly not the case. Upon analysis of the reasons for recall, we predicted from a two-compartment model that the estimated blood level was 88 ng/mL-1; this level would have provided no amnesia. This case illustrates that recall can occur with the use of midazolam, especially if levels become subtherapeutic, and other measures should be taken to provide adequate anesthesia and amnesia.

Adult↗
PubMed2005

Increases in bispectral index lead to interventions that prevent possible intraoperative awareness.

In this case a woman underwent a cervical laminectomy with a total i.v. anaesthesia technique and during her care two problems occurred with propofol delivery. In both cases, bispectral index increases alerted caregivers to the decreased propofol delivery and allowed them to make corrections in a manner timely enough to prevent the occurrence of awareness during anaesthesia. The case illustrates how intraoperative processed electroencephalographic monitoring may decrease the incidence of recall of awareness following surgery.

Adult↗
PubMed2002

Intraoperative awareness: detected by the structured Brice interview?

BACKGROUND: Awareness is a rare complication in general anesthesia, but its consequences are stressful. Efforts must be undertaken to prevent, diagnose, and, if occurring, treat it. The incidence of awareness is higher following anesthesia involving the use of muscle relaxants. As a part of a quality assurance program at our short-stay surgery all patients exposed to general anesthesia are routinely subjected to a Brice interview, which aims to evaluate our standard anesthetic technique regarding awareness. METHODS: The Brice interview was used prospectively in 5216 patients given a propofol/opioid anesthetic for day-case or short-stay surgery. Neuromuscular blocks were used only for surgical needs, not routinely. All patients were interviewed on discharge from the recovery room. A second interview, according to Brice, was undertaken by telephone 3-7 days later in the case of a notable intraoperative event, or otherwise after postoperative patient complaints. All patients were also interviewed by telephone 1-2 days postoperatively. RESULTS: None of the patient interviews indicated awareness. This was also the case in five non-relaxed patients who had an incident of light anesthesia with eye opening and gross motor response without forewarning. Neuromuscular blockade was used in 7% of patients. DISCUSSION: We were unable to detect intraoperative awareness. The anesthetic regimen, including minimal use of muscle relaxants, might be beneficial for awareness prevention. Alternatively, the diagnostic power, the timing of the Brice interview, or the number of interviews performed may be questioned.

Adolescent↗
PubMed2002

High risk of intraoperative awareness during cardiopulmonary bypass with isoflurane administration via diffusion membrane oxygenators.

In cardiac surgery with the aid of extracorporeal circulation (ECC), inhalation anaesthetics can be administered via the oxygenator. Until the recent advent of a new type of diffusion membrane oxygenator, we routinely added the inhalation agent, isoflurane, to the gas flow of a microporous capillary membrane-type oxygenator. Applying this procedure to the diffusion-type oxygenators, the depth of anaesthesia appeared to be affected, which manifested itself through unusually high intraoperative perfusion pressures. This observation led to a prospective randomized study comprising 60 patients and two models of a microporous capillary membrane oxygenator, as well as two models of a diffusion membrane oxygenator. Simultaneous isoflurane concentration measurements at both the gas inlet and outlet ports of the oxygenators showed that, whereas in the microporous capillary-type oxygenators the isoflurane administered was reduced by about 50% during the passage of gas through the device, there was only a minimal transfer of isoflurane in the diffusion-type membrane oxygenators.

Anesthetics, Inhalation↗
PubMed2002

Intraoperative awareness and the depth of anesthesia in children: a perspective from pediatric anesthesia.

The bispectral index (BIS) monitoring, using electroencephalographically-derived method, has shown some promise to measure 'depth of anesthesia' for various anesthetics. A large fraction of the literature that has investigated BIS monitoring demonstrates that BIS correlates well with clinically important endpoints and many clinical utility trials have been undertaken in adults to prove its effectiveness to improve perioperative patient care. As the use of the technology grows, other potential applications have been investigated; BIS as a monitor in pediatric anesthesia and BIS as a monitor to measure the depth of sleep may serve as examples. If the two are proved useful, these successes may bring clinicians another application of this technology: BIS to monitor unconsciousness state of babies to prevent sudden infant death syndrome or apparent life threatening event.

Journal Article↗
PubMed2002

Victims of awareness.

BACKGROUND: Intraoperative awareness with explicit recall may be followed by long-lasting mental symptoms. However, the average risk for developing mental sequelae after awareness, and the average severity and the duration of symptoms has not previously been illustrated in a consecutive series of awareness cases. METHODS: Nine patients among 18 consecutive, prospectively identified cases of intraoperative awareness with recall could be located after approximately 2 years and agreed to an interview about possible persisting problems. RESULTS: Four of the nine interviewed patients were still severely disabled due to psychiatric/psychological sequelae. All of these patients had experienced anxiety during the period of awareness, but only one had complained about pain. Another three patients had less severe, transient mental symptoms, although they could cope with these in daily life. Two patients denied any sequelae from their awareness episode. CONCLUSIONS: Up to 3 weeks after their unsuccessful anesthetic, repeated information and discussions had been offered. Despite the fact that all patients at that time claimed to be satisfied with this management, and eventually considered no further contacts necessary, this was obviously inaccurate. Therefore, professional psychiatric assessment, treatment and long-term follow-up should constitute standard practice for all patients who have experienced intraoperative awareness.

Adult↗
PubMed2006

[Awareness: a problem in paediatric anaesthesia?].

Intraoperative awareness has been reported to occur in 0.8-5.0% of paediatric patients undergoing anaesthesia and, therefore, seems to be more common than in adults (incidence 0.1-0.2%). In adult patients, the consequences of intraoperative awareness are well known and can be severe, in children, however, they have not yet been adequately studied. The causes for intraoperative awareness can be divided into three broad categories: First, no or only a light anaesthetic is given on purpose, second, an insufficient dose of an anaesthetic is given inadvertently, third, there is equipment malfunction or the anaesthesiologist makes an error. Unfortunately, especially in young children, painful interventions are still performed without adequate analgesia, e.g. awake intubation or fracture manipulation under midazolam sedation alone. The key issue is, however, that pharmacokinetics and pharmacodynamics change enormously from the 500 g preterm baby to the adolescent patient. Adequate dosing is much more difficult in paediatric patients compared to standard adult surgical patients. Solid knowledge of the pharmacokinetic and pharmacodynamic characteristics of commonly used drugs in different paediatric age groups, as well as aiming for perfection in daily care will help to reduce the incidence of awareness. Methods for monitoring the depth of hypnosis, e.g. the bispectral index, will be used increasingly, at least in children above 1 year of age. In addition to clinical parameters, they will hopefully help to further reduce the incidence of intraoperative awareness.

Adult↗
PubMed2006

Monitoring consciousness in the pediatric patient: not just a small adult.

Intraoperative awareness, defined as postoperative memory for intraoperative events, is believed to occur about 0.2% of the time in a general adult surgical population. A recent large-scale prospective study from a single institution revealed a strikingly high incidence (0.8%) of intraoperative awareness in children aged 5-12 years although the sequelae of awareness during surgery in children were reported to be relatively minor. This contrasts with awareness in adult patients, for whom this complication often causes psychological trauma, thus having medico-legal implications. Various monitors to detect intraoperative awareness have been used with varying success in adults. To date, however, no monitor has been shown to be effective in detecting intraoperative awareness during surgery in pediatric patients. Further research is required to clarify the rates of intraoperative awareness in the pediatric population as well as the need for monitoring this event during the clinical practice of pediatric anesthesiology.

Anesthesia↗
PubMed1995

[Awareness during general anesthesia. Definition, incidence, clinical relevance, causes, avoidance and medicolegal aspects].

The possibility that a patient during general anaesthesia is aware of the operation going on and aware of severe pain that might be remembered postoperatively must be very alarming to patients and anaesthetists alike. Furthermore, there is experimental evidence showing that conscious recall of intraoperative events is only the tip of an iceberg; it seems very probable that there is even a higher incidence of unconscious perception during general anaesthesia. Therefore, the following stages of intraoperative awareness must be distinguished: (1) conscious awareness with explicit recall and with severe pain; (2) conscious awareness with explicit recall but no complaints of pains; (3) conscious awareness without explicit recall and possible implicit recall; (4) subconscious awareness without explicit recall and possible implicit recall; (5) no awareness. The incidence of conscious awareness with explicit recall and severe pain has been estimated at less frequent than 1/3000 general anaesthetics. Conscious awareness with explicit recall but no complaints of pain has been reported in the literature with an incidence of 05-2%. With 7-72%, conscious awareness without explicit recall and possible implicit recall shows a very wide range of variation and its occurrence probably depends on the anaesthetic drugs used. Subconscious awareness with possible implicit recall has an incidence of up to 80%, but there are many methodological problems in demonstrating implicit memory of intraoperative events. Reports of intraoperative awareness do not come exclusively from cardiac surgery and obstetrics, but also from all other operative specialties. Postoperatively, patients who experience intraoperative awareness may develop a so-called post-traumatic stress syndrome. Symptoms involve re-experiencing the event awake or in dreams, sleep disturbances, depression, avoidance of stimuli associated with the event. The probability of the development of the post-traumatic stress syndrome seems to coincide with the experience of severe pain. When a patient complains of intraoperative awareness postoperatively the anaesthesiologist should discuss the event frankly with the patient. When the symptoms of the post-traumatic stress syndrome persist a psychotherapy should follow. Causes for intraoperative awareness may be: equipment failure, too-light anaesthesia, e.g. for a caesarean section or for emergency surgery in severely injured or polytraumatized patients, during cardiac surgery, bronchoscopy of difficult intubation. There is interindividual variability in anaesthetic effect; for example, chronic drug or alcohol abuse or overweight may make increased anaesthetic doses necessary. They are at risk for intraoperative awareness. Some general anaesthetics or anaesthetic procedures, e.g. the combination of a relaxant and N2O, opioid mono-anaesthetics, or opioids combined with benzodiazepines, seem to involve a higher risk of intraoperative awareness than do volatile anaesthetics. The bases of litigation are medical malpractice, breach of contract by the anaesthesiologist or lack of informed consent from the patient. Therefore, patients who are at risk of intraoperative awareness should be given detailed information on this special risk before the operation.

Anesthesia, General↗
PubMed1996

Recall of awareness during cardiac anaesthesia: influence of feedback information to the anaesthesiologist.

We interviewed 303 cardiac surgery patients to evaluate the incidence of intraoperative awareness with recall. First, we randomly interviewed 99 patients, of whom four patients (4%) reported awareness and recall. We informed the cardiac anaesthesiologists of the results of these interviews, and we also gave general information regarding means to reduce awareness and recall during general anaesthesia. Thereafter, we interviewed 204 consecutive cardiac surgery patients. Now, three of the patients (1.5%) had intraoperative awareness with recall. The reduction in the incidence from 4% to 1.5% was not significant. However, the doses of principal anaesthetic drugs had increased significantly between the two interview phases, while the dose of pancuronium, the main muscle relaxant used, had decreased significantly. Also, there was a significant increase in the number of anaesthesias where anaesthetic agents had been administered continuously instead of bolus or non-continuous dosing techniques. Between the patients with awareness and recall and those without it, there was no difference in the doses of anaesthetic agents given. The patients with awareness were significantly younger than those not aware. In conclusion, with educational measures and vigilance over the problem, the incidence of intraoperative awareness during cardiac anaesthesia may be reduced. The incidence figure of 1.5% we observed is of the magnitude reported recently by others with modern cardiac anaesthesia techniques.

Adult↗
PubMedDate not supplied

[The effect of encephalogram bispectral index monitoring during total intravenous anesthesia with propofol in outpatient surgery].

OBJECTIVE: To assess the effect of monitoring the encephalogram bispectral index (BIS) during outpatient surgery. Outcome measures were amount of propofol administered, awakening and discharge. MATERIAL AND METHODS: Forty consecutive outpatient surgery patients were studied. The patients gave informed consent and received general intravenous anesthesia with propofol administered through a laryngeal mask using a computerized system (Diprifusor(R)). Two groups were formed: in group A, BIS was monitored, although the information was hidden from the anesthesiologists, who used the usual signs (loss of blinking reflex, pupil size and hemodynamic response) to guide anesthesia; in group B the anesthesiologists used BIS monitoring to guide propofol administration. Measurements were blood pressure, heart rate and BIS at six times during the procedure (T1-T6). Other data recorded were age, weight, height, propofol consumption in relation to weight and duration of procedure, consumption of rocuronium and alfentanil, duration of propofol infusion, time from withdrawal of propofol until eye opening, duration of stay in the post-anesthesia intensive care unit and time until total recovery. A questionnaire assessed the presence of intraoperative awareness and degree of satisfaction. The data were analyzed by Student's t and a chi square tests, with statistical significance at p < 0.05. RESULTS: Demographic variables (age, weight and height) were similar, as were duration of propofol infusion, total dose of alfentanil and rocuronium, evolution of blood pressure and heart rate. Statistically significant differences in BIS were observed at two times, T4 and T5; total propofol administered was 32.6% lower in group B; and time until eye opening was significantly shorter in group B. No significant differences were observed for time until full recovery. No instances of intraoperative awareness were reported and satisfaction was high in both groups. CONCLUSION: BIS monitoring allows for propofol titration that leads to a mean reduction of 32.6% in consumption, shortening the time until eye opening without causing intraoperative awareness or reducing patient satisfaction.

Adult↗
PubMed2003

Bispectral index-guided anesthesia in patients undergoing aortocoronary bypass grafting.

In this prospective, randomized study, we compared hemodynamics, oxygenation, possible intraoperative awareness, and costs in 62 patients undergoing first-time elective coronary artery bypass grafting at 2 different levels of anesthesia. Depth of anesthesia was assessed with bispectral index (BIS). All patients were anesthetized with sufentanil/midazolam. The dosage of sufentanil/midazolam was adjusted to achieve a BIS level of 45-55 in 32 patients (Group BIS 50), whereas in 30 patients a BIS level of 35-45 was intended (Group BIS 40). Data were obtained at six different time points before, during, and after surgery. All patients were asked about possible intraoperative awareness on the third postoperative day. There were no significant differences of any hemodynamic or oxygenation variables at any time between the two groups. BIS 40 patients received significantly (P < 0.05) more sufentanil (BIS 40, 888 +/- 211 microg; BIS 50, 514 +/- 99 microg) and midazolam (BIS 40, 22.4 +/- 5.6 mg; BIS 50, 16.6 +/- 3.7 mg) than BIS 50 patients. The reduction in anesthetic drugs used saved euro;13.78/US$12.54 per patient (P < 0.05) in Group BIS 50, but one BIS electrode caused additional costs of 19.95 Euros/18.15 US dollars. Time to extubation was not significantly prolonged in Group BIS 40 (BIS 40, 14.3 +/- 4.6 h; BIS 50, 11.8 +/- 3.8 h). There was no explicit memory during anesthesia in either group. BIS-guided reduction of anesthetic medication saved costs and did not increase the risk of intraoperative awareness. However, total costs were increased by monitoring BIS, because of the BIS electrodes.

Aged↗