Patients' age, low preoperative kana-hiroi test score, and low preoperative rSO2 were important risk factors for postoperative delirium.

The relationship between bispectral index (BIS) and electroencephalographic parameters was evaluated during nitrous oxide/isoflurane anesthesia. At surgical levels of anesthesia, BIS and the relative synchrony of fast and slow wave (a parameter derived from bispectral analysis) or burst-compensated spectral edge frequency 95% (a parameter derived from power spectral analysis) are well correlated.

We describe a patient in whom the bispectral index (BIS) decreased to 0 during surgery. A 42-yr-old man with chronic renal failure was scheduled to undergo construction of an arteriovenous shunt. He had a history of acute cerebral hemorrhage. An intracranial hematoma had been removed a month earlier with almost complete neurological recovery. He had uncontrolled hypertension. His systolic blood pressure was 180 mm Hg before anesthesia induction. Anesthesia was induced with 100 mg of propofol and 3% sevoflurane. After laryngeal mask insertion, anesthesia was maintained with nitrous oxide 60% in oxygen and sevoflurane. BIS decreased to near 0 on 2 occasions: after anesthesia induction and shortly after the start of the surgery. His systolic blood pressure decreased to 110 mm Hg and BIS increased when his blood pressure was increased to 130-140 mm Hg. The decrease in BIS was suspected to be the result of decreased cerebral blood flow. The systolic blood pressure of 110 mm Hg (mean blood pressure, 80 mm Hg) was probably less than the lower limit of autoregulation. Although BIS has some limitations as a cerebral monitor, it was useful for detecting possible cerebral hypoperfusion in this case.

Sedation for short-term procedures is increasingly being used in clinical practice. Selection of appropriate drugs is important for effective and safe sedation; however, an ideal sedative remains unavailable. Remimazolam is a novel, ultrafast-acting benzodiazepine with a shorter duration of action than other agents in this class. It is currently expected to become a popular agent for short-term procedural sedation. Remimazolam shows higher clearance, a smaller volume of distribution, and a shorter half-life than midazolam. It showed dose-dependent sedative action, with onset of sedation within 60s of administration. The results of clinical trials indicate that remimazolam is more useful than midazolam for short procedural sedation such as in patients who undergo colonoscopy and that its safety profile is comparable with that of midazolam. Anesthesia-induced vascular pain is lesser and reduction in blood pressure is lesser with remimazolam than with propofol. Moreover, the availability of flumazenil (a benzodiazepine antagonist) is a specific advantage of remimazolam. These characteristics and the results of clinical trials suggest that remimazolam will be a safer alternative to previous sedative drugs for sedation during the short surgical procedures. Although short-acting agents are useful, they might lead to immediate hyper-sedation. Remimazolam is a promising agent for short-term procedural sedation; however, clinicians should be mindful of the risks of this agent.

The most surprising finding of this study is that total intravenous anesthesia (TIVA) was used in 21 of the 24 (88%) cases of definite and possible awareness. Although the incidence of intraoperative awareness was compatible with the previous studies, meticulous care should be taken when anesthesia is performed by TIVA for high-risk patients. The results of this survey should be verified, as well as further continuous survey and prospective study, because this study was performed by an anonymous questionnaire survey conducted over only 1-year period.

No abstract

No abstract

With the introduction of bispectral index (BIS) as a measure of a patient's sedation during general anesthesia, attention has been directed toward bispectral analysis of electroencephalography (EEG). In the present study we evaluated the relationship between EEG bicoherence and sevoflurane concentration. Sixteen ASA physical status I-II patients scheduled for elective abdominal surgery were enrolled in the study. Anesthesia was induced with 5% sevoflurane and maintained with sevoflurane and oxygen (50%). Just before surgery, IV fentanyl (2 microg/kg) was given and then continuously infused (2 microg x kg(-1) x h(-1)). Using software we developed, EEG bicoherence, BIS, and 95% spectral edge frequency (SEF95) were recorded at end-tidal sevoflurane concentrations of 0.5%, 0.8%, 1.1%, 1.4%, 1.7%, 2.0%, and 2.3%. Under light anesthesia, EEG bicoherence values were low. With increasing sevoflurane concentrations, 2 peaks of bicoherence emerged along the diagonal line (f1 = f2). Both the first (at around 4 Hz) and second (at around 10 Hz) grew higher (37.7% +/- 7.5% and 35.1% +/- 9.0%, respectively) as the sevoflurane concentration increased to 1.4%. However, the first peak leveled off whereas the second tended to decrease slightly with further increases in sevoflurane concentration. The BIS value decreased as the sevoflurane concentration increased and leveled off at 1.4% and higher concentrations of sevoflurane. The SEF 95 also decreased as the sevoflurane concentration increased up to 2.3%. Thus the distribution pattern of the two bicoherence peaks is likely to be better than BIS of the anesthetic effect of sevoflurane during surgery.