Helmar Bornemann

Bispectral-index-guided versus clinically guided remifentanil/propofol analgesia/sedation for interventional radiological procedures: an observer-blinded randomized study.

Patients undergoing potentially painful interventional radiological procedures generally require a combination of analgesia and sedation. This sedation/analgesia should allow the patient to communicate while also remaining calm. Bispectral index (BIS) monitoring could be useful in achieving this. The primary end-point of our study was to compare the percentage time with optimal sedation, defined as Sedation Agitation Scale (SAS) grade 4, between a BIS-guided remifentanil/propofol regimen and a clinically guided regimen in 54 randomly allocated patients. The mean ± sd percentage time with optimal sedation was significantly longer (P = 0.004) in the BIS group (76.6% ± 14.7%) than in the SAS group (63.8% ± 16.4%). There was a significant difference in the weighted mean infusion rates of remifentanil (P = 0.0067) and propofol (P = 0.0075) in the BIS group (0.066 ± 0.027 &mgr;g · kg−1 · min−1 1.59 ± 0.44 mg · kg−1 · h−1) compared with the SAS group (0.091 ± 0.036 &mgr;g · kg−1 · min−1 1.92 ± 0.43 mg · kg−1 · h−1), respectively. BIS values exhibited a temporal correlation to SAS scores (r2 = 0.72). In conclusion, a BIS-guided regimen was more effective than a SAS-guided regimen. The use of BIS resulted in fewer remifentanil and propofol doses. The targeted BIS range of 80–85 provided a sufficient functional level of sedation.

Sensitivity and specificity of bispectral index for classification of overt hepatic encephalopathy.A multicentre, observer-blinded, validation study

Background: The severity of hepatic encephalopathy is currently graded clinically using West Haven criteria and psychometric tests. Objective: To assess the discriminative power of the bispectral index (BIS) monitor to classify the degree and progression of hepatic encephalopathy. Design: A consecutive, multicentre, observer blinded validation study. Setting: Medical University of Graz (Graz, Austria), Zhejiang University First Affiliated Hospital (Hang Zhou, China), and Cairo University (Cairo, Egypt). Patients: 28 consecutive patients with hepatic encephalopathy were first enrolled at Medical University of Graz as a test set. The estimated BIS cut off values were subsequently tested in a validation set of 31 patients at Zhejiang University First Affiliated Hospital and 26 patients at Cairo University; 18 patients were reassessed later in a longitudinal study. Fifteen of 85 patients (18%) were excluded from the final analysis (11 became too agitated with high electromyographic activity; four fell asleep during the recording). Results: Applying the Austrian BIS cut off values of 85, 70, and 55 for discriminating West Haven grades 1 to 4 yielded agreement between BIS classification and West Haven grades in 40 of the 46 validation patients (87%), and in 16 of the 18 follow up patients (89%). Mean (SD) BIS values differed significantly between patients with West Haven grade 1 (90.2 (2.5)), grade 2 (78.4 (6.6)), grade 3 (63.2 (4.8)), and grade 4 (45.4 (5.0)). Conclusions: BIS is a useful measure for grading and monitoring the degree of involvement of the central nervous system in patients with chronic liver disease.

Geographic Regional Differences in Rocuronium Bromide Dose-Response Relation and Time Course of Action An Overlooked Factor in Determining Recommended Dosage

Background:Geographic location is not acknowledged as a stratifying factor that can directly affect drug potency, because drugs are still licensed with the same recommended dose for different geographic regions. The aim of the current study was to compare the potency and duration of action of rocuronium bromide in 54 patients in three countries with different life habits, diet, and ambient conditions, namely white Austrians, white North Americans, and Han Chinese in China. Methods:Neuromuscular block of six consecutive 50-&mgr;g/kg rocuronium incremental doses followed by 300 &mgr;g/kg was evaluated using the Relaxometer mechanomyograph (Groningen University, Groningen, Holland). Dose–response curves were created using log-dose-probit transformation. The authors compared rocuronium bromide ED50, ED90, and ED95 (effective doses required for 50%, 90%, and 95% first twitch depression, respectively) as well as Dur25 and Dur0.8 (times from last incremental dose administration until 25% first twitch and 0.8 train-of-four ratio recovery, respectively) in patients of the three countries. Results:Rocuronium ED50, ED90, and ED95 were significantly higher in Austrian patients (258 ± 68, 530 ± 159, and 598 ± 189 &mgr;g/kg) and Chinese patients (201 ± 59, 413 ± 107, and 475 ± 155 &mgr;g/kg) compared with American patients (148 ± 48, 316 ± 116, and 362 ± 149 &mgr;g/kg, respectively). Dur25 and Dur0.8 were significantly shorter in Austrian patients (22.3 ± 5.5 and 36.9 ± 12.8 min) and Chinese patients (30.4 ± 7.5 and 45.7 ± 15.9 min) compared with American patients (36.7 ± 8.5 and 56.2 ± 16.7 min, respectively). Conclusions:The authors demonstrated a significant difference in rocuronium potency and duration of action among patients in the three countries. Larger studies are required for determining dosage recommendations for different geographic regions.

Effect of sugammadex or neostigmine neuromuscular block reversal on bispectral index monitoring of propofol/remifentanil anaesthesia

BACKGROUND Sugammadex is a modified γ-cyclodextrin with a novel mechanism of action for reversing the steroidal neuromuscular blocking agent rocuronium. Bispectral index (BIS) is an EEG-derived measure which can be sensitive to frontal electromyographic (EMG) artifacts. We compared BIS values before and after sugammadex or neostigmine neuromuscular block (NMB) reversal in patients with or without high EMG activity. METHODS During stable propofol/remifentanil anaesthesia and rocuronium-induced block, 48 patients were randomly allocated to receive sugammadex 4 mg kg(-1) or neostigmine 50 μg kg(-1)/glycopyrrolate 10 μg kg(-1), 10 min after the end of surgery. RESULTS Five minutes after sugammadex administration, mean BIS 50.1 (10.3) increased (P=0.018) to 61.7 (7.9) in 11 patients with high EMG activity. In contrast, BIS 49.3 (4.9) remained at 51.9 (5.4) in 13 patients who had no EMG activity. Fifteen minutes after neostigmine administration, mean BIS 51.9 (8.1) increased (P=0.007) to 63.9 (8.1) in 13 patients who had reappearance of muscle activity. However, in 11 patients who had no EMG activity, BIS 52.3 (7.4) remained at 53.3 (6.8). There was no significant difference between the sugammadex and neostigmine groups over time. CONCLUSIONS We have shown that reversal of NMB with sugammadex or neostigmine increased BIS values dependent on the presence of EMG activity. Thus, the effect of muscle activity reappearance during rocuronium NMB reversal spuriously increasing the BIS value should be taken into consideration when relying on BIS monitoring for evaluating propofol/remifentanil recovery.

BIS-vista occipital montage in patients undergoing neurosurgical procedures during propofol-remifentanil anesthesia.

Background:Neurosurgical procedures that require a frontal approach could be an impediment for a successful Bispectral Index® (BIS®) frontal sensor placement. The aim of this study was to explore the utility of using the new BIS-Vista™ monitor (Aspect Medical Systems, Newton, MA) for occipital sensor placement in the patients undergoing brain neurosurgical procedures during propofol–remifentanil anesthesia. Methods:Two BIS® Quatro sensors (Aspect Medical Systems, Newton, MA) mounted on the occipital and frontal regions were connected to two BIS-Vista™ monitors at three anesthesia states: before induction, during anesthesia maintenance, and recovery. Results:There were significant differences before induction (P = 0.0002) and at anesthesia maintenance (P = 0.0014) between mean ± SD occipital (83.4 ± 4.8, 66.7 ± 7.2) and frontal (93.1 ± 3.4, 56.9 ± 9.1) BIS-Vista™ values. During anesthesia recovery, there was no difference (P = 0.7421) between occipital (54.6 ± 9.3) and frontal (53.1 ± 7.3) BIS-Vista™ values. Bland and Altman analysis revealed a BIS-Vista negative-bias (limits of agreement) of −9.7 (+1.1, −20.5) before anesthesia induction, +9.8 positive-bias (+22.8, −1.7) during anesthesia maintenance, and −0.9 bias (+10.9, −12.8) during anesthesia recovery. Conclusion:We demonstrated that not only the regional limits of agreement are too wide to allow data of the two montages to be used interchangeably but also the variation is a function of anesthetic depth. However, keeping in mind a relatively consistent BIS-Vista™ −10 bias before induction and +10 bias during anesthesia maintenance with limits of agreement of approximately ±11 BIS units, approximately double the clinically acceptable less than 10 BIS units level of agreement, BIS-Vista™ off-label occipital montage might be helpful in following a trend of propofol–remifentanil anesthesia in individual cases where frontal access is particularly difficult.

Effect of Flumazenil on Bispectral Index Monitoring in Unpremedicated Patients

Background:Flumazenil is an imidazobenzodiazepine that promptly reverses via competitive inhibition the hypnotic/sedative effects of benzodiazepines on γ-aminobutyric acid receptors. Endogenous benzodiazepine ligands (endozepines) were isolated in urine, cerebrospinal fluid, and breast milk of women who had not received benzodiazepines. The bispectral index (BIS), an electroencephalographically derived parameter widely used for monitoring the effects of anesthetic/hypnotic drugs, was shown to correlate to various conditions that could influence electroencephalography. The authors examined the hypothesis that 0.5 mg of flumazenil administered to healthy unpremedicated patients during deep surgical remifentanil/propofol anesthesia would increase the BIS value and might expedite recovery from anesthesia. Methods:Sixty healthy unpremedicated patients were randomly allocated to the flumazenil or control groups. After study drug administration, the authors compared BIS values and various recovery parameters in the flumazenil and control groups. Results:BIS baseline values in the flumazenil group (38.7 ± 3.8) increased 15 min after flumazenil administration (53.2 ± 4.7), with a significant difference over time (P < 0.0001) between the two groups. Mean recovery parameters time, comprising time to spontaneous breathing, eye opening/hand squeezing on verbal command, extubation, and date of birth recollection, was significantly shorter (P = 0.0002) in the flumazenil group (6.9 ± 2.6 min) compared with the control group (9.8 ± 2.9 min). Conclusions:This study demonstrates that flumazenil given to healthy unpremedicated patients during propofol/remifentanil anesthesia significantly increased the BIS value and allowed earlier emergence from anesthesia. This may indicate that flumazenil could be used on a case-by-case basis to reverse endogenous or exogenous endozepines that might play a role during anesthesia.

Effect of somatostatin analogue octreotide on pain relief after major abdominal surgery

Background: Octreotide acetate is an 8‐amino‐acids synthetic octapeptide analogue of somatostatin with much‐enhanced duration of action and lower incidence of side effects. We assessed the utility of using intravenous octreotide as an adjuvant to opioid analgesia that might exert a post‐operative opioid‐sparing effect.

The patient with coronary stents and antiplatelet agents: what to do and how to deal?

The management of patients with recent coronary artery stents presenting for noncardiac surgery has become a major topic of interest and concern for all perioperative care givers. The present review will update recent reports and particularly new guidelines as well as recommendations. Based on the available literature, all experts recommend avoiding premature discontinuation of antiplatelet drug therapy if possible except for a few surgical procedures. Drug-eluting stents obviously carry more risks than bare-metal stents.

Comparison of a new neuromuscular transmission monitor compressomyograph with mechanomyograph

BACKGROUND We developed a new neuromuscular transmission monitor, the compressomyograph (CMG, European patent number: EP 06018557.6, US patent number: US 60/824.541). This is the first preliminary report comparing neuromuscular block monitored by CMG and the Relaxometer mechanomyograph (MMG). METHODS The two monitors were randomly allocated to the left or right hands of 16 patients. T1, first twitch of the train-of-four (TOF) expressed as percentage of control response, and the TOF ratio (T4:t1) were used to evaluate the neuromuscular block produced by rocuronium 0.6 mg kg(-1). RESULTS The CMG monitor exhibited no pre-relaxation reverse fade (T4>T1) or T1 exceeding 100%. There was no significant difference in mean (SD) onset time, Dur(25) (time to T1 25% recovery), or Dur(0.9) (time to 0.9 TOF ratio recovery) measured by the CMG [2.4 (0.9), 22.6 (4.1), 43.1 (10.3) min, respectively] compared with MMG [2.1 (0.9), 22.9 (3.3), 43.3 (10.0) min, respectively]. According to Bland and Altman analysis, the bias (upper and lower limits of agreement) for T1% was -0.3% (+13.4% and -13.8%) and for TOF ratio was -0.009 (+0.068 and -0.085). CMG showed 100% sensitivity and 75% specificity in indicating full relaxation for tracheal intubation, and 80% sensitivity with 86% specificity in predicting MMG 0.9 TOF ratio. CONCLUSIONS The CMG could be a reliable clinical monitor in the daily anaesthesia practice that does not require time to set up or rigid support of the arm.

Different Propofol–Remifentanil or Sevoflurane–Remifentanil Bispectral Index Levels for Electrocorticographic Spike Identification during Epilepsy Surgery

Background:Medical therapy, the cornerstone of managing epilepsy, still fails a substantial portion of patients. Little information is available regarding the potential impact of different bispectral index (BIS) levels on electrocorticographic spike identification for surgical epileptic foci resection. Methods:Twenty-two intractable epilepsy subjects were randomly allocated to the propofol–remifentanil or sevoflurane–remifentanil groups, and were further randomized to four BIS85 (BIS 71–85), BIS70 (BIS 56–70), BIS55 (BIS 41–55), and BIS40 (BIS ⩽40) sequence order. Results:Two-way ANOVA revealed no differences between groups in spike frequency (P = 0.720), spike amplitude (P = 0.647), or number of spiking leads (P = 0.653). In the propofol and sevoflurane groups, decreasing BIS levels increased mean ± SD spike/min frequency (P < 0.001 and P < 0.001) at BIS85 (10 ± 12 and 10 ± 8), BIS70 (19 ± 17 and 17 ± 15), BIS55 (22 ± 17 and 18 ± 8), and BIS40 (25 ± 15 and 23 ± 17). Furthermore, in the propofol and sevoflurane groups, decreasing BIS levels increased spike microvolt amplitude (P = 0.006 and P = 0.009) at BIS85 (1,100 ± 400 and 750 ± 400), BIS70 (1,200 ± 460 and 850 ± 490), BIS55 (1,300 ± 560 and 940 ± 700), and BIS40 (1,400 ± 570 and 1,300 ± 700). Whereas, in the propofol and sevoflurane groups, there was no difference in the location or number of spiking leads (P = 0.057 and P = 0.109) at the four BIS levels. Compared with BIS85, spike frequency in the propofol and sevoflurane groups increased 100 and 170% at BIS70, 116 and 180% at BIS55, and 132 and 230% at BIS40. Compared with BIS85, spike amplitude increased 108 and 113% at BIS70, 121 and 125% at BIS55, and 128 and 170% at BIS40. Conclusion:Decreasing BIS levels in the propofol and sevoflurane groups enhanced epileptogenic spike frequency and amplitude with the same location and number of spiking leads.