EEG-based indices of anaesthesia: correlation between bispectral index and patient state index?

BACKGROUND AND OBJECTIVE: Both the bispectral and the patient state indices are derived from the electroencephalogram and have been proposed as a measure of the same clinical target, the hypnotic component of anaesthesia. The present study evaluated whether there is concordance between the bispectral and the patient state indices with regard to end-points measured simultaneously in patients undergoing surgery under general anaesthesia. METHODS: Fifty-seven patients scheduled for elective abdominal, orthopaedic (Groups 1 and 2) or cardiac surgery (Group 3) under general anaesthesia were enrolled in the study. Anaesthesia was performed using remifentanil/ sevoflurane (Group 1, 19 patients), remifentanil/propofol (Group 2, 19 patients) or sufentanil/propofol/isoflurane (Group 3, 19 patients). The bispectral and the patient state indices were simultaneously recorded. Pearson's correlation between these two indices was calculated for the complete data and each group. The percentage of bispectral index values in the recommended range for general anaesthesia (45-60) that were confirmed by levels of patient state index (25-50) was calculated and vice versa. RESULTS: Overall correlation between the bispectral and the patient state indices was 0.667, 0.671 in Group 1, 0.650 in Group 2 and 0.675 in Group 3 (P < 0.01). For values of the bispectral index between 45 and 60, only 40% of corresponding patient state index values were between 25 and 50. For patient state index values of 25-50, only 50% of the corresponding bispectral index values were in the range of 45-60. CONCLUSIONS: Concordance between the bispectral and patient state indices is relatively weak, whereas both are thought to reflect the same clinical target, the hypnotic component of anaesthesia. As a consequence, further studies are required to compare reliability of both indices as indicators of different levels of hypnosis.     

Does using the bispectral index (BIS) during craniotomy affect the quality of recovery?

One of the aims of neuroanesthesia is to provide early postoperative recovery and neurologic examination in patients undergoing supratentorial surgery. Our aim was to investigate the role of using the bispectral index (BIS) in recovery from anesthesia and altering drug administration in patients undergoing craniotomy. Fifty American Society of Anesthesiologists' (ASA) physical status I-II patients undergoing craniotomy were included in the study. The patients were randomly divided into two groups, and all patients received standard induction drugs, and 0.8%-1.5% sevoflurane was used for maintenance of anesthesia. In the BIS-guided group, the concentration of sevoflurane was titrated to maintain BIS at 40-60. In the control group, the anesthesiologist was blind to BIS, and the concentration of sevoflurane was changed according to the patients' hemodynamic changes. The hemodynamic data, BIS values, and sevoflurane concentrations were recorded every 15 minutes. In addition, the BIS value was recorded by the primary anesthetist in the BIS-guided group and by another independent anesthetist in the control group. At the end of the study, recovery criteria and Aldrete recovery scores were recorded every 15 minutes. Neurologic assessments were performed when the Aldrete score was 9-10. BIS values were higher, and sevoflurane concentrations (P < 0.05) and total doses of fentanyl (P < 0.01) were lower, in the BIS-guided group. Times to first spontaneous breathing, eye opening, and extubation (P = 0.035, P = 0.001, and P = 0.0001, respectively) were significantly shorter in the BIS-guided group. Time to an Aldrete score of 9-10 and adequate neurologic assessment were similar between the groups. In conclusion, BIS monitoring by supratentorial craniotomy under general anesthesia reduced the maintenance anesthetic concentration and narcotic drug usage and lowered the recovery times from general anesthesia.     

Does the use of electroencephalographic bispectral index or auditory evoked potential index monitoring facilitate recovery after desflurane anesthesia in the ambulatory setting?

BACKGROUND: Analogous to the Bispectral Index (BIS) monitor, the auditory evoked potential monitor provides an electroencephalographic-derived index (AAI), which is alleged to correlate with the central nervous system depressant effects of anesthetic drugs. This clinical study was designed to test the hypothesis that intraoperative cerebral monitoring guided by either the BIS or the AAI value would facilitate recovery from general anesthesia compared with standard clinical monitoring practices alone in the ambulatory setting. METHODS: Sixty consenting outpatients undergoing gynecologic laparoscopic surgery were randomly assigned to one of three study groups: (1) control (standard practice), (2) BIS guided, or (3) AAI guided. Anesthesia was induced with 1.5-2.5 mg/kg propofol and 1-1.5 microg/kg fentanyl given intravenously. Desflurane, 3%, in combination with 60% nitrous oxide in oxygen was administered for maintenance of general anesthesia. In the control group, the inspired desflurane concentration was varied based on standard clinical signs. In the BIS- and AAI-guided groups, the inspired desflurane concentrations were titrated to maintain BIS and AAI values in targeted ranges of 50-60 and 15-25, respectively. BIS and AAI values, hemodynamic variables, and the end-tidal desflurane concentration were recorded at 5-min intervals during the maintenance period. The emergence times and recovery times to achieve specific clinical endpoints were recorded at 1- to 10-min intervals. The White fast-track and modified Aldrete recovery scores were assessed on arrival in the PACU, and the quality of recovery score was evaluated at the time of discharge home. RESULTS: A positive correlation was found between the AAI and BIS values during the maintenance period. The average BIS and AAI values (mean +/- SD) during the maintenance period were significantly lower in the control group (BIS, 41 +/- 10; AAI, 11 +/- 6) compared with the BIS-guided (BIS, 57 +/- 14; AAI, +/- 11) and AAI-guided (BIS, 55 +/- 12; AAI, 20 +/- 10) groups. The end-tidal desflurane concentration was significantly reduced in the BIS-guided (2.7 +/- 0.9%) and AAI-guided (2.6 +/- 0.9%) groups compared with the control group (3.6 +/- 1.5%). The awakening (eye-opening) and discharge times were significantly shorter in the BIS-guided (7 +/- 3 and 132 +/- 39 min, respectively) and AAI-guided (6 +/- 2 and 128 +/- 39 min, respectively) groups compared with the control group (9 +/- 4 and 195 +/- 57 min, respectively). More importantly, the median [range] quality of recovery scores was significantly higher in the BIS-guided (18 [17-18]) and AAI-guided (18 [17-18]) groups when compared with the control group (16 [10-18]). CONCLUSION: Compared with standard anesthesia monitoring practice, adjunctive use of auditory evoked potential and BIS monitoring can improve titration of desflurane during general anesthesia, leading to an improved recovery profile after ambulatory surgery.     

Which is responsible for the haemodynamic response due to laryngoscopy and endotracheal intubation? Catecholamines, vasopressin or angiotensin?

BACKGROUND AND OBJECTIVE: We have investigated the concentrations of epinephrine, norepinephrine, vasopressin and angiotensin converting enzyme activity to explore the role of these mediators in the neuroendocrine response to laryngoscopy and tracheal intubation. METHODS: One hundred (50 male, 50 female) ASA I patients aged 20-50 yr (mean+/-SEM; 35.59+/-0.99) were included in the study. They were undergoing elective surgery under standard anaesthesia induction and maintenance using tracheal intubation. Plasma concentrations of epinephrine, norepinephrine and vasopressin as well as plasma angiotensin converting enzyme activity were determined at four time points, before (T1) and after (T2) induction, and 2 (T3) and 5 min (T4) after intubation. Blood pressure and heart rate were recorded at corresponding times to reveal if any correlation existed between haemodynamic parameters and neuroendocrine response. RESULTS: Heart rate increased after induction and intubation (P<0.05) and decreased significantly at T4 (P<0.05). Systolic blood pressure decreased significantly (P<0.05) after induction and increased slightly after intubation decreasing to below baseline value (P<0.05) at T4. Diastolic blood pressure increased slightly after intubation and decreased significantly (P<0.05) at T4. Plasma epinephrine and norepinephrine concentrations decreased after induction and increased at T3 and T4 without reaching significance. Vasopressin concentrations increased slightly at T2 and T3 and decreased significantly at T4 (P<0.05). Angiotensin converting enzyme activity was unaffected when compared with baseline values. CONCLUSIONS: Blood pressure, heart rate, plasma epinephrine, norepinephrine and vasopressin concentrations increased slightly in response to laryngoscopy and intubation, all returning to or below baseline 5 min later with no change in angiotensin converting enzyme activity in normotensive patients.     

Thoracic epidural anaesthesia for cardiac surgery: are we missing the point?

Anaesthetic techniques have always had to adapt to changingsurgical interventions. Several developments over the last 15yr have changed practice in cardiac surgery. First, standardaccess to the heart via median sternotomy can often be replacedby less invasive approaches, as used in minimally invasive directcoronary artery bypass surgery, robotic surgery, or endovascularvalve surgery.¹ Secondly, perioperative management strategieshave adopted more ‘physiological’ techniques, suchas normothermic extracorporeal circulation^{2 3} or blood cardioplegia.⁴Thirdly, off-pump aorto-coronary bypass grafting (OPCAB) avoidingextracorporeal circulation has been shown to have the potentialto decrease postoperative morbidity.^{5 6} The absence of extracorporealcirculation     

Does deflating the lungs and sawing from the xiphisternum reduce the chance of accidental pleurotomy during sternotomy?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether deflating the lungs or sawing from the xiphisternum, reduces the incidence of accidental pleurotomy when performing a sternotomy. Altogether 170 papers were identified using the below mentioned search, of which 4 papers presented the best evidence to answer the clinical question. The author, journal, date and country of publication, patient group, relevant outcomes and weaknesses were tabulated. We conclude that disconnection of the ventilator prior to sternotomy cannot be supported as a strategy to reduce the incidence of accidental pleurotomy. In addition there is little evidence to support sternotomy from the Xiphoid process upwards over sternal notch downwards.     

Does leukodepletion during elective cardiac surgery really influence the overall clinical outcome?

AIM: We examined the impact of leukocyte filtration during the entire bypass time on postoperative leukocytosis, perioperative hemorrhage and overall clinical outcome in patients undergoing elective cardiac surgery. METHODS: Eighty patients who electively underwent cardiac surgery were randomly allocated to a leukocyte depletion group (n=40) or a control group (n=40). In patients of the leukocyte depletion group an arterial line filter with leukocyte depleting capacity (Pall LG6) was applied instead of a standard arterial line filter. White blood cells and platelet count were estimated preoperatively and at various times postoperatively. Postoperative clinical outcomes were also recorded. RESULTS: Repeated measure analysis of variance between groups showed that leukocyte counts were significantly lower in the depletion group postoperatively (p=0.005) whereas no difference was found in the platelet counts (p=0.37). The catecholamine dose required at the time of weaning from cardiopulmonary bypass and during the first 12 postoperative hours was found to be lower in the leukodepletion group (p=0.027 and p=0.021, respectively). Furthermore leukodepleted patients showed a transient improvement in the oxygenation index (p=0.029) and a shorter period of mechanical ventilation (p<0.001). The incidences of postoperative complications were similar between the groups. No difference was observed in regard to postoperative blood loss (p=0.821) and amount of packed red blood cells required for transfusion during the first 24 hours (p=0.846). The duration of intensive care unit stay and of hospitalization were similar between the groups. CONCLUSION: Leukocyte depletion contributes to early postoperative improvement in heart and lung function but does not influence significantly the overall clinical outcome of patients undergoing elective cardiac surgery.     

Can the bispectral index be used to predict seizure time and awakening after electroconvulsive therapy?

The electroencephalogram (EEG) bispectral index (BIS) measures the hypnotic component of the anesthetic state and correlates with emergence from general anesthesia. Therefore, we hypothesized that the BIS would be useful in predicting electroconvulsive therapy (ECT)-induced seizure times and awakening from methohexital anesthesia. Twenty-five consenting patients with major depressive disorders underwent 100 maintenance ECT treatments. All patients were premedicated with glycopyrrolate 0.2 mg IV, and anesthesia was induced with methohexital 1 mg/kg IV. The BIS was monitored continuously, and the values were recorded at specific end-points, including before anesthesia (baseline), after the induction of anesthesia (pre-ECT), at the end of ECT (peak), after ECT (suppression), and on awakening (eye opening). The pre-ECT BIS value correlated with the duration of both the motor (r = 0.3) and EEG (r = 0.4) seizure activity (P < 0.05). The peak post-ECT BIS value correlated with the duration of the EEG seizure activity (r = 0.5) (P < 0.05). A positive correlation was also found between the EEG seizure duration and the time to eye opening (r = 0.4) (P < 0.05). However, the BIS values on awakening from methohexital anesthesia varied from 29 to 97 and were <60 in 75% of the cases. We conclude that the BIS value before the ECT stimulus is applied could be useful in predicting the seizure time. However, the BIS values on awakening were highly variable, suggesting that it reflects both the residual depressant effects of methohexital and post-ictal depression. IMPLICATIONS: The bispectral index (BIS) value immediately before the electroconvulsive therapy (ECT) stimulus correlates with the duration of the motor and electroencephalogram (EEG) seizure activity during methohexital anesthesia. In addition, the increase in the BIS value during the ECT-induced seizure was proportional to the duration of EEG seizure activity. However, the BIS value on awakening from anesthesia varied widely, from 29 to 97.     

Does the frailty index predict discharge disposition and length of stay at the hospital and rehabilitation facilities?

IntroductionMany geriatric hip fracture patients utilize significant healthcare resources and require an extensive recovery period after surgery. There is an increasing awareness that measuring frailty in geriatric patients may be useful in predicting mortality and perioperative complications and may be useful in helping guide treatment decisions. The primary purpose of the study is to investigate whether the frailty index predicts discharge disposition from the hospital and discharge facility and length of stay.MethodsIn this retrospective cohort study, patients aged 65 years and older presenting to a level 1 trauma center with a hip fracture and a calculated frailty index were eligible for inclusion. The primary outcome was discharge disposition. Secondary outcomes were hospital and discharge facility length of stay, 90-day hospital mortality and readmissions, and return to home.ResultsA total of 313 patients were included. The frailty index was a robust predictor of discharge to a skilled nursing facility (OR 1.440 per 0.1 point increase). Patients with a higher frailty index were at higher risk of 90-day mortality and less likely to return to home at the end of follow-up. There was a very weak correlation between the frailty index and hospital length of stay (ρ=0.30) and rehab length of stay (ρ=0.26).ConclusionThe frailty index can be used to predict discharge destination from both the hospital and rehabilitation facility, 90-day mortality, and return to home after rehabilitation. In this study, the frailty index had a very weak correlation with length of stay in the hospital and in discharge destination. The frailty index can be used to help guide medical decision making, goals of care discussions, and to determine which patients benefit from intensive rehabilitation.     

General anaesthesia for the cocaine abusing patient. Is it safe?

Background. Commonly, cocaine abusing patient are scheduledfor elective surgery with a positive urine test for cocainemetabolites. As many of these patients were clinically non-toxic[normal arterial pressure and heart rate, normothermic, anda normal (or unchanged from previous) ECG, including a QTc interval<500 ms], we have recently proceeded with elective surgeryrequiring general anaesthesia in this patient group. Methods. Forty urine cocaine positive patients were comparedwith an equal number of drug-free controls in a prospective,non-randomized, blinded analysis. Intraoperative mean arterialblood pressure, ST segment analysis, heart rate and body temperaturewere recorded and compared. Results. Cardiovascular stability during and after general anaesthesiain cocaine positive, non-toxic patients was not significantlydifferent when compared with an age and ASA matched drug-freecontrol group. Conclusions. These results demonstrate that the non-toxic cocaineabusing patient can be administered general anaesthesia withno greater risk than comparable age and ASA matched drug-freepatients.     

Does the evidence support the use of spinal and epidural anesthesia for surgery?

When spinal and epidural anesthesia were introduced into clinical practice, their primary use was as an alternative to general anesthesia. Later, largely as a result of the realization that opioids could be safely and effectively used to produce selective spinal analgesia, spinal and epidural (neuraxial) analgesia began to be used specifically for the treatment of perioperative pain. We present a systematic review of the literature on neuraxial anesthesia and analgesia, new meta-analyses that illustrate the powerful effect of improvements in perioperative safety in general on the ability of neuraxial techniques to make a difference, and a consideration of why a literature analysis does not provide clear answers.     

The bispectral index system in pediatrics--is it related to the end-tidal concentration of inhalation anesthetics?

BACKGROUND AND GOAL OF STUDY: Bispectral Index (BIS) has been used in adults to measure depth of anesthesia using various protocols. Though less investigated in children, there is growing evidence that bispectral index seems adequately calibrated for monitoring the depth of isoflurane and sevoflurane anesthesia in pediatric patients. A range of BIS scores (40-60) has been seen to be an indicator for an acceptable level of hypnosis and anesthesia. Davidson and Czarnecki have reported that, at an end-tidal concentration of 1 MAC, the BIS for halothane was significantly greater than isoflurane (56.5 +/- 8.1 vs. 35.9 +/- 8.5). The explanation given is the fact that the volume concentration of the MAC value is inversely related to the BIS value. Accordingly, it is expected that the BIS value at 1 MAC of desflurane must be less than halothane and isoflurane. MATERIALS AND METHODS: This is a clinical cross-over, prospective, randomized double blinded study. 90 pediatric patients scheduled for below umbilical surgery, under general and caudal analgesia, were allocated into 4 study groups. The BIS values at a relatively equipotent doses of the previously mentioned agents were compared with each other in the same group and between other groups. RESULTS: At a relatively equipotent doses, the mean BIS value for halothane {60.4 +/- 5.6} was significantly higher than isoflurane {45.5 +/- 9.2} and desflurane {38.5 +/- 9.2} P<0.001). Equivalent end-tidal doses of different inhalational anesthetics do not necessarily have the same effects on cortical and sub-cortical functions and consequently on EEG. Conclusion: The use of a relatively equipotent end-tidal concentration of different inhalational agents may result in different BIS values.     

Can epiaortic ultrasound reduce the incidence of intraoperative stroke during cardiac surgery?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether changing operative technique based on epiaortic ultrasound reduces the incidence of intra-operative stroke during cardiac surgery? Altogether 179 papers were found using the reported search, of which eight presented the best evidence to answer the clinical question. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results, and study weaknesses of these papers are tabulated. We conclude that epiaortic ultrasound is superior to manual palpation in detecting atherosclerosis in the ascending aorta, and the severity of atherosclerosis found is closely correlated to the incidence of postoperative stroke. No touch techniques in patients with severe atherosclerosis may avert this increase in the incidence of stroke.     

Is the ARX index a more sensitive indicator of anesthetic depth than the bispectral index during sevoflurane/nitrous oxide anesthesia?

BACKGROUND: During general anesthesia, hypnotic components have been monitored with electroencephalogram. The bispectral index is derived from a cortical electroencephalogram, but the A-line ARX index is the electroencephalographic response to auditory stimuli. The purpose of this study was to compare the changes of the A-line ARX index and the bispectral index during sevoflurane - nitrous oxide anesthesia. METHODS: One hundred females aged 30-60 years, and scheduled for partial mastectomy, were divided into two groups. Anesthesia was induced with sevoflurane 5% and nitrous oxide in oxygen for 3 min. A laryngeal mask airway was inserted, and anesthesia was maintained with sevoflurane 1-2% and nitrous oxide in oxygen. During surgery, the sevoflurane end-tidal concentration was kept at 0.5%, 1%, or 2% for 5 min before each measurement. Blood pressure, heart rate, and the A-line ARX index (n = 50), and the bispectral index (n = 50) were measured. RESULTS: Blood pressure and heart rate increased following laryngeal mask airway insertion and blood pressure decreased at 2% sevoflurane in both groups similarly. The A-line ARX index, but not the bispectral index, increased significantly by laryngeal mask airway insertion and skin incision. The A-line ARX index decreased at 2% sevoflurane compared with 0.5%, while the bispectral index remained unchanged. CONCLUSION: During sevoflurane-nitrous oxide anesthesia, the A-line ARX index might be a more sensitive indicator of anesthetic depth than the bispectral index.