Feasibility study for the administration of remifentanil based on the difference between response entropy and state entropy †

BACKGROUND

Facial electromyography (FEMG) may have utility in the assessment of nociception during surgery. The difference between state entropy (SE) and response entropy (RE) is an indirect measure of FEMG. This study assesses an automated algorithm for remifentanil administration that is based on maintaining an entropy difference (ED) that is less than an upper boundary condition and greater than a lower boundary condition.

METHODS

The algorithm was constructed with a development set (n = 40), and then automated and studied with a validation set (n = 20) of patients undergoing anterior cruciate ligament repair. The percentage of time that the ED was maintained between the two boundary conditions was determined. Remifentanil and propofol predicted effect-site concentrations (Ce) were determined at surgical milestones and, after drug discontinuation, the time to response to verbal stimulation and orientation was measured.

RESULTS

The median (25th-75th percentile) per cent of time that the ED was recorded between the boundary conditions was 99.3% (98.1-99.8%). Predicted propofol (microg ml(-1)) and remifentanil (ng ml(-1)) Ce (sd), respectively, were 3.5 and 4.0 at induction, 1.9 (0.8) and 7.2 (3.7) at the end of surgery, and 1.1 (0.5) and 3.2 (2.2) at eye opening. The median time to eye opening and orientation was 3.8 and 6.8 min, respectively.

CONCLUSION

This feasibility study supports the concept that remifentanil may be delivered using an algorithm that maintains the difference between SE and RE between the upper and lower boundary condition.

Attitude of general public to risks associated with anaesthesia

OBJECTIVE

To identify specific fears being entertained about general anaesthesia.

METHODS

People who do work in any medical facility were targeted in this prospective questionnaire-based study. All respondents were literate. The questionnaire was divided into two sections; (a) The baseline information, which included age, sex, marital status, occupation, previous exposure to anaesthesia and patient preference for anaesthesia technique. (b) Fear about risks associated with general anaesthesia; respondents were expected to pick one of four options (very concerned, somewhat concerned, not concerned and not sure), to indicate how they feel about each of the eight risks listed in the questionnaire. The data obtained was analyzed using SSPS version 10 for Windows.

RESULTS

In a bivariate analysis, marital status, occupation and previous exposure to anaesthesia are not associated with the expressed fear by the respondents. Respondents had the highest concern for the fear of death (82%), followed by fear of postoperative pain (75.4%). Least concern was for awareness during anaesthesia (37.7%). The mean age of those who expressed concern about being aware during operation is 37.0 +/- 8.6 years while those not concerned is 31.8 +/- 8.5 years (p=0.034). More of those who are concerned with nakedness preferred general anaesthesia (p = 0.023). Also, more females (95.7%) than males (70.6%) expressed fear about pain during general anaesthesia (p = 0.019).

CONCLUSION

Fear of death is a great concern for our patients coming for general anaesthesia and it is followed closely by fear of postoperative pain, the later was of greater concern to females. Finally, more of those who were concerned about nakedness preferred general anaesthesia.

Gender differences between predicted and measured propofol C(P50) for loss of consciousness

OBJECTIVE

To investigate gender differences in the effective dose of 50% for loss of consciousness (C(P50LOC)) for propofol using Diprifusor, the most commonly used target-controlled infusion system.

DESIGN

Prospective, randomized, comparative study.

SETTING

University-affiliated hospital.

PATIENTS

50 ASA physical status I and II patients, aged 20 to 50 years, scheduled for minor surgery.

INTERVENTIONS

Patients were randomized into two groups of 25 patients each. A target-controlled infusion of propofol (Diprifusor) was maintained at a predetermined target concentration. After a 10-minute steady state, blinded investigators evaluated patients' consciousness using verbal commands. The propofol test concentration was predetermined using a modified version of Dixon's up-and-down method (starting at 2.5 mug/mL; step size of 0.1 microg/mL).

MEASUREMENT

Predicted and measured C(P50LOC) values and bispectral index (BIS) were obtained by averaging the crossover midpoint (ie, consciousness to unconsciousness). Those values were analyzed by unpaired t test: P < 0.05 was considered significant.

RESULTS

The predicted C(P50LOC) for men was 2.14 +/- 0.10 microg/mL, which was lower than that for women, 2.55 +/- 0.11 microg/mL (P < 0.0001). No significant difference was found for measured C(P50LOC) in men (2.37 +/- 0.41 microg/mL) and in women (2.30 +/- 0.28 microg/mL) or for BIS measurements.

CONCLUSION

Predicted C(P50LOC) by Diprifusor for men tended to be underestimated; that for women tended to be overestimated. Our data support a review of Diprifusor (Astra Zeneca, Osaka, Japan) pharmacokinetic parameters to avoid awareness during operation, particularly for women.

Bispectral index values during elective rigid bronchoscopy: a prospective observational pilot study

Rigid bronchoscopy is associated with a high incidence of haemodynamic disturbance and awareness under anaesthesia. Anaesthetic agents are given both to attenuate the sympathetic response to bronchoscopy and to prevent awareness. Use of the Bispectral index to guide anaesthesia has shown to reduce awareness and improve recovery times from general anaesthesia. We undertook a prospective observational study of BIS values in 50 patients during routine anaesthesia for rigid bronchoscopy. BIS values were found to be between 40-60 during bronchoscopy for only 0.5% of the time (0-11.5%[0-98.7%]), median (interquartile range [range]). Patients had a BIS < 40 for 99.6% (87.9-100%[0-100%]) of the duration of bronchoscopy. We identified one case of possible awareness. Few of our patients undergoing general anaesthesia for rigid bronchoscopy had BIS scores in the suggested range of between 40 and 60. BIS < 40 was more frequent than in previous studies of different surgical populations. There was no difference in the BIS values of patients anaesthetised with intermittent boluses or target controlled infusions of propofol.

The PediSedate device, a novel approach to pediatric sedation that provides distraction and inhaled nitrous oxide: clinical evaluation in a large case series

BACKGROUND

Pediatric sedation is of paramount importance but can be challenging. Fear and anticipatory anxiety before invasive procedures often lead to uncooperativeness. A novel device (PediSedate) provides sedation through a combination of inhaled nitrous oxide and distraction (video game). We evaluated the acceptability and safety of the PediSedate device in children.

METHODS

We enrolled children between 3 and 9 years old who were scheduled to undergo surgical procedures that required general inhalational anesthesia. After the device was applied, he/she played a video game while listening to the audio portion of the game through the earphones. Nitrous oxide in oxygen was administered via the nasal piece of the headset starting at 50% and increasing to 70%, in 10% increments every 8 min. Treatment failures, vital signs, arterial oxygen saturation, depth of sedation, airway patency, side effects, acceptance of the device and parental satisfaction were all evaluated.

RESULTS

Of 100 children included, treatment failure occurred in 18% mainly because of poor tolerance of the device. At least 96% of the children who completed the study exhibited an excellent degree of sedation, 22% had side effects, and none experienced serious airway obstruction. Nausea and vomiting were the most common side effects and no patients had hemodynamic instability.

CONCLUSIONS

The PediSedate device combines nonpharmacologic with pharmacologic methods of sedation. Most of the children we evaluated were able to tolerate the PediSedate device and achieved an adequate degree of sedation.

Bispectral index and electroencephalographic entropy in patients undergoing aortocoronary bypass grafting

BACKGROUND AND OBJECTIVE

This study was conducted to compare bispectral index, state entropy and response entropy in patients undergoing coronary artery bypass grafting.

METHODS

In 66 patients, anaesthesia was maintained at two different levels using bispectral index. Doses of sufentanil and midazolam were adjusted to achieve a bispectral index in the range of 45-55 in 33 patients (BIS 50 group) and 35-44 in another 33 patients (BIS 40 group). Simultaneously, state entropy and response entropy were recorded.

RESULTS

The targeted values of bispectral index were achieved in both groups and the bispectral index values differed significantly during whole anaesthesia. Median response entropy and state entropy fell to 19-26 during anaesthesia in both groups. Response entropy and state entropy values in the two groups differed significantly only after induction of anaesthesia and did not differ during further anaesthesia. There was no explicit intraoperative recall in both groups. Patients in Group BIS 40 received significantly (P<0.05) more sufentanil than the BIS 50 group (704+/-181 microg vs. 490+/-107 microg, respectively) and midazolam (18.5+/-6.1 mg vs. 15.6+/-3.8 mg, respectively). After cardiopulmonary bypass, significantly (P<0.05) more patients in Group BIS40 needed inotropic support with dobutamine (79%) than in the BIS50 group (52%). Time to extubation did not differ between the two groups.

CONCLUSION

In patients undergoing coronary artery bypass grafting, no relationship was found between bispectral index levels and state entropy and response entropy at two different stages of a sufentanil-midazolam anaesthesia. A bispectral index level of 45-55 reduced anaesthetic medications used and the need for inotropic support.

The drug-induced helplessness test: an animal assay for assessing behavioral despair in response to neuroleptic treatment

RATIONALE

Neuroleptic dysphoria encompasses a range of unpleasant subjective responses and, as a result, is difficult to study in preclinical animal models.

OBJECTIVE

Based on the learned helplessness model of depression, increases in escape failures (EFs) in the drug-induced helplessness test (DH) are proposed to reflect drug-induced depressive-like state, a contributing factor to neuroleptic dysphoria in humans.

MATERIALS AND METHODS

Effects of the typical antipsychotic haloperidol and the atypical antipsychotics risperidone, olanzapine, aripiprazole, quetiapine, and clozapine were investigated in the DH test. We further characterized this test by examining compounds affecting motor function, cognition, anxiety, and those with antidepressant activity.

RESULTS

The antipsychotics haloperidol, risperidone, aripiprazole, and olanzapine, all increased EFs, while quetiapine had no effect, and clozapine reduced EFs. Amphetamine, diazepam, and ciproxifan, had no effect on EFs. Scopolamine significantly reduced EFs and MK-801 showed a trend toward reducing EFs at doses not significantly sti mulating locomotor activity. Subchronic, but not acute, imipramine and subchronic fluoxetine significantly reduced EFs at doses significantly suppressing locomotor activity. Dissociation appears to exist between performance in the DH test and compound effects on catalepsy or locomotor activity.

CONCLUSIONS

After discussing potential alternative interpretations of the drug-induced changes of EFs, we propose the DH test as a useful test for assessing a drug-induced, depressive-like state that may contribute to neuroleptic dysphoria.

Interaction of attention and graphomotor functions in children with attention deficit hyperactivity disorder

The present article provides a review of a series of studies in children with attention deficit hyperactivity disorder (ADHD) concerning (1) the effects of methylphenidate on various attentional functions, (2) the stimulant-induced changes of both qualitative and quantitative (i.e. kinematic) aspects of handwriting, (3) the interaction between conscious control of handwriting and fluency of handwriting movements, and (4) possible therapeutic approaches to graphomotor disturbances. Children with ADHD showed impairments in various aspects of attentional functioning. Pharmacological treatment of ADHD children with methylphenidate resulted in marked improvements of various components of attentional functioning. In comparison to the performance following the withdrawal of methylphenidate, children with ADHD on methylphenidate displayed a significant improvement in task accuracy in the areas of vigilance, divided attention, selective attention (inhibition, focused attention and integration of sensory information) and flexibility. However, the comparison with healthy children revealed considerable deficits regarding vigilance, divided attention, flexibility and selective attention (focused attention and integration of sensory information) in children with ADHD on methylphenidate. The comparison of writing movements of children on and off methylphenidate revealed that medication resulted in a better handwriting, but a deterioration in handwriting fluency as assessed by kinematic analysis. Children with ADHD may use their increased attentional capacities to focus on skills (e.g. handwriting) that are independent of conscious control or may even be disturbed by attention. The findings summarized in this paper indicate, therefore, that administration of methylphenidate alone is insufficient in the treatment of children with ADHD. Children with ADHD may benefit from instructions on how to best use their improved attentional capacities.

Error-processing deficits in patients with cocaine dependence

Cocaine abuse and addiction can be characterized by a persisting use of cocaine in the face of adverse consequences. In the present study we focus on one specific element of adverse consequences: the making of errors. The aim of this study was to determine whether cocaine-dependent persons have error-processing deficits as measured using error-related negativity (ERN) and error positivity (Pe). Event-related potentials (ERPs) during an Eriksen flanker task were recorded from cocaine-dependent patients and a control group. Cocaine-addicted patients showed reduced ERN and Pe components as compared to a control group. On the behavioral level, patients showed reduced post-error accuracy improvement. The present findings reveal that cocaine addiction is associated with reduced error processing and impaired behavioral correction of errors after an error is made. These deficits may be associated with a compromised dopamine system. It is argued that these cognitive deficits may contribute to the maintenance of the cocaine addiction.

Depth of Anesthesia Monitoring

Depth-of-anesthesia monitoring with EEG or EEG combined with mLAER is becoming widely used in anesthesia practice. Evidence shows that this monitoring improves outcome by reducing the incidence of intra-operative awareness while reducing the average amount of anesthesia that is administered, resulting in faster wake-up and recovery, and perhaps reduced nausea and vomiting. As with any monitoring device, there are limitations in the use of the monitors and the anesthesiologist must be able to interpret the data accordingly. The limitations include the following. The currently available monitoring algorithms do not account for all anesthetic drugs, including ketamine, nitrous oxide and halothane. EMG and other high-frequency electrical artifacts are common and interfere with EEG interpretation. Data processing time produces a lag in the computation of the depth-of-anesthesia monitoring index. Frequently the EEG effects of anesthetic drugs are not good predictors of movement in response to a surgical stimulus because the main site of action for anesthetic drugs to prevent movement is the spinal cord. The use of depth-of-anesthesia monitoring in children is not as well understood as in adults. Several monitoring devices are commercially available. The BIS monitor is the most thoroughly studied and most widely used, but the amount of information about other monitors is growing. In the future, depth-of-anesthesia monitoring will probably help in further refining and better understanding the process of administering anesthesia.

An open trial of paroxetine for the "offensive subtype" of taijin kyofusho and social anxiety disorder

The taijin kyofusho (TKS) offensive subtype is thought to be a culture-bound syndrome similar to social anxiety disorder (SAD). In Western countries, such patients would be diagnosed as having delusional disorder, somatic subtype, or body dysmorphic disorder. Recently, open trials for the TKS offensive subtype and a randomized controlled trial for body dysmorphic disorder demonstrated that selective serotonin reuptake inhibitors (SSRIs) might be as effective in TKS as in SAD. This study investigated the efficacy of the SSRI paroxetine in patients with the TKS offensive subtype, both on anxiety and fears, as well as insight. This study was a 12-week open trial using paroxetine in 22 patients with TKS. Subjects were diagnosed based on the original diagnostic criteria for the TKS offensive subtype. Insight regarding TKS symptoms was assessed by the 11th supplement subscale "Insight into obsessions and compulsions" of the Yale-Brown Obsessive Compulsive Scale (Y-BOCS). The Liebowitz Social Anxiety Scale (LSAS), the Beck Depression Inventory (BDI), the State-Trait Anxiety Inventory (STAI), Rosenberg's Self-Esteem Scale, and the Interpersonal Distrust subscale of the Eating Disorder Inventory were also administered. Offensive anxiety was assessed by the original TKS offensive anxiety subscale (0-3 points). The primary efficacy variable was the Clinical Global Impression scale (CGI) global improvement item. Nineteen patients completed the study. Forty-seven percent (9/19) were responders to the drug treatment (scoring 2 or less on the CGI). Last observation carried forward (LOCF) analysis (N=22) demonstrated a statistically significant reduction in LSAS total score and offensive anxiety in TKS, and the insight scale score of the Y-BOCS also significantly improved. Interpersonal distrust showed a trend toward improvement.

Detektion intraoperativer Wachheit bei einem Kleinkind mit akustisch evozierten Potenzialen

Intraoperative wakefulness is not only limited to adults and can also be found at a similar percentage (0.8%) in paediatric anaesthesia. For prevention of awareness neurophysiologic methods like auditory evoked potentials might be helpful. We report a case of a 2-year-old boy receiving balanced anaesthesia with sevoflurane and alfentanil. Midlatency auditory evoked potentials (MLAEPs) were recorded continuously before, during and after the surgical procedure. During the surgical procedure sevoflurane was withdrawn unintentionally. After a short period of time the boy started coughing and moved his legs, which was interpreted as insufficient analgesia. Several boli of alfentanil did not lead to the expected clinical effect on the depth of anaesthesia. After a recheck of the anaesthetic ventilator the error was determined and delivery of the volatile anaesthetic restored. The postoperative evaluation of the MLAEPs revealed the inadequate suppression of auditory processing during this incident with latencies comparable to the awake state. After reapplication of sevoflurane the MLAEPs were almost completely suppressed demonstrating adequate anesthetic depth. Exemplarily this case suggests that MLAEPs could be used to detect intraoperative awareness also in paediatric anaesthesia. Investigations to prove the validity and reproducibility of MLAEPs in children will be necessary.

Intraoperative awareness in children: myth or reality?

PURPOSE OF REVIEW

This review will outline old and recent data about the prevalence, causes and potential consequences of intraoperative awareness in children and give details on its detection.

RECENT FINDINGS

Recent studies have confirmed the higher incidence of intraoperative awareness in children than in adults while using modern anaesthetic techniques. To detect this complication in children, the Brice interview, commonly used in adults, has to be adapted to children's cognitive capacities, with an extended follow-up. Neither the old nor the recent studies clearly identify predictive risk factors. Children describe the same perceptions as adults during their awareness period (mainly auditory and tactile sensations), but with fewer negative thoughts. Moreover, they do not seem to be affected by this experience, as they do not have long-term psychological sequelae. The prevention of intraoperative awareness in children is the same as in adults, the major factor being awareness of this complication.

SUMMARY

Intraoperative awareness is a reality in school-aged children. A larger multicentre study and large-scale follow-up is required in order to confirm the higher incidence of awareness and identify the risk factors and long-term psychological sequelae of this complication in the paediatric population.

Preserved sensitivity to beta2-adrenergic receptor agonists in patients with type 1 diabetes mellitus and hypoglycemia unawareness

BACKGROUND AND OBJECTIVE

Use of beta(2)-adrenergic receptor agonists has been advocated for the treatment of hypoglycemia unawareness in type 1 diabetes. In vitro, however, hypoglycemia unawareness has been associated with reduced beta(2)-adrenergic sensitivity. Therefore, in vivo sensitivity to beta(2)-adrenergic receptor agonist stimulation was compared between type 1 diabetic patients with and without hypoglycemia unawareness and nondiabetic controls.

METHODS

Ten type 1 diabetic patients with hypoglycemia unawareness, 12 type 1 diabetic patients with intact hypoglycemic awareness, and 11 healthy controls were enrolled. beta(2)-Adrenergic sensitivity was determined by measuring the forearm vasodilator response to intraarterial infusion of salbutamol. Salbutamol was infused in six increasing doses ranging from 0.003 to 1.0 mug(1).min(-1).dl(-1). Forearm blood flow (FBF) was bilaterally measured by venous occlusion plethysmography. Diabetic patients received low-dose insulin before FBF measurements to ensure that experiments were carried out under normoglycemic conditions.

RESULTS

At baseline, FBF was 1.9 +/- 0.3 ml(1).min(-1).dl(-1) in controls, 2.3 +/- 0.4 ml(1).min(-1).dl(-1) in patients with intact awareness, and 1.4 +/- 0.1 ml(1).min(-1).dl(-1) in patients with hypoglycemia unawareness (P = 0.048 vs. aware patients). In response to salbutamol, FBF increased 9.1-fold in controls, 8.0-fold in patients with intact awareness, and 10.7-fold in patients with hypoglycemia unawareness (P = NS). Heart rate increased in all groups due to systemic spillover of salbutamol but appeared blunted, considering a greater fall in mean arterial pressure in patients with hypoglycemia unawareness.

CONCLUSIONS

Sensitivity to beta(2)-adrenergic receptor agonist stimulation is preserved in type 1 diabetic patients with hypoglycemia unawareness.

EEG parameters and their combination as indicators of depth of anaesthesia / EEG-Parameter und deren Kombination für das Narkosemonitoring

EEG parameters for assessment of depth of anaesthesia are typically based on different signal processing methods, such as spectral and complexity analysis. In the present study, the parameters investigated (WSMF, qWSMF, approximate entropy and Lempel-Ziv complexity) do not correlate monotonically to depth of anaesthesia. To obtain this correlation, parameters are combined based on fuzzy inference, whereby each parameter only operates in a specific range. Fuzzy inference seems to be a suitable approach, as the indicator designed separates wakefulness from unconsciousness as well as the best single parameter does and correlates to the depth of anaesthesia.

Cerebral state index response to incision: a clinical study in day-surgical patients

BACKGROUND

Inadequate anaesthesia, with somatic/autonomic response or awareness, is often revealed at intubation and surgical incision. Anaesthetic depth monitors should be able to prevent this risk. This explorative study examined the ability of the cerebral state monitor to predict autonomic/somatic responses to incision.

METHODS

Forty-two ASA I-II day-surgical patients [19 men and 23 females; mean age 52 (29-79) years, mean weight 77 (50-118) kg] were induced clinically with fentanyl/propofol with sevoflurane after placement of the laryngeal mask airway. The cerebral state index (CSI) was blindly recorded 4 min prior to and 4 min after incision.

RESULTS

During the 4 min prior to incision, the mean CSI was 45 (16-62) and increased by 9 (-13-40) when the mean value for the first 4 min after incision was subtracted from the value prior to incision, corresponding to a relative change of 21% (-21-118). The change in CSI did not show any consistent relation to the value before incision. Five patients showed minor movements after incision and six patients had > 25% increase in blood pressure. Neither CSI nor the change in index differed between patients who did or did not respond somatically or autonomically to incision. The last CSI value just prior to incision was 44 for non-responders and 40 and 42 for somatic and autonomic responders, respectively.

CONCLUSION

The CSI in the majority of patients was within acceptable ranges during clinically adjusted anaesthesia prior to incision but seems not to be able to reliably predict an autonomic or somatic response to incision.

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.

Depth of anaesthesia monitoring: what's available, what's validated and what's next?

Depth of anaesthesia monitors might help to individualize anaesthesia by permitting accurate drug administration against the measured state of arousal of the patient. In addition, the avoidance of awareness or excessive anaesthetic depth might result in improved patient outcomes. Various depth of anaesthesia monitors based on processed analysis of the EEG or mid-latency auditory-evoked potentials are commercially available as surrogate measures of anaesthetic drug effect. However, not all of them are validated to the same extent.

Awareness under anesthesia during electroconvulsive therapy treatment

Awareness under general anesthesia is an infrequent phenomenon during which patients become cognizant of some or all events during surgery or any procedure conducted under anesthesia. Awareness experiences can frighten patients and impact their memories in ways that can leave emotional and psychological problems that, over time, may develop into posttraumatic stress disorder. Inadequate anesthesia has been implicated in the causation of awareness under anesthesia. We report first case of patient gaining awareness while under anesthesia undergoing electroconvulsive therapy treatment. The case reported here would suggest that clinicians administering electroconvulsive therapy should be alert to the possibility of awareness during anesthesia and take appropriate measures to maintain professional conduct and adjust anesthetic medication dose to avoid reoccurrence.