Masaki Takashina

The effects of propofol, isoflurane, and sevoflurane on oxygenation and shunt fraction during one lung ventilation

Propofols effect on hypoxic pulmonary vasoconstriction during one-lung ventilation (OLV) has not been determined. Twenty patients who had long-term OLV for esophageal surgery were allocated randomly to one of two study groups; one in which isoflurane administration preceded propofol, and another in which sevoflurane administration preceded propofol. Arterial and mixed venous blood samples and hemodynamics were measured as follows: before OLV, during OLV, OLV at 4 cm of positive end-expiratory pressure (PEEP), OLV after conversion from volatile anesthetics to propofol, OLV at 4 cm of PEEP, and after OLV. After the application of 4 cm of PEEP during propofol anesthesia, PaO2 increased significantly in both groups. The shunt fraction (Qs/Qt) increased significantly after the initiation of OLV in both groups and decreased significantly after the conversion from volatile anesthetics to propofol in both groups. Propofol can be used safely during OLV because PaO2 increased after the application of 4 cm of PEEP during propofol anesthesia, and Qs/Qt decreased significantly after the conversion from inhaled anesthetics to propofol anesthesia. Implications: During one-lung ventilation, the arterial partial pressure of oxygen values with propofol were greater than those with isoflurane and sevoflurane, and shunt fraction values with propofol were lower than those with both volatile anesthetics. Propofol improved oxygenation and shunt fraction during one-lung ventilation compared with volatile anesthetics. (Anesth Analg 1998;87:1164-9)

Practical issues in bispectral analysis of electroencephalographic signals.

IMPLICATIONS The aim of this report was to confirm the methodology of bispectral analysis of electroencephalogram. In developing a software for real-time bispectral analysis, we encountered several practical problems in bispectrum calculation. We settled those and concluded that 3 min of monitoring are required to obtain reliable and reproducible bicoherence values.

Electroencephalographic Bicoherence Is Sensitive to Noxious Stimuli during Isoflurane or Sevoflurane Anesthesia

BackgroundThe authors previously reported changes in electroencephalographic bicoherence during isoflurane anesthesia combined with epidural anesthesia. Here, they examined the influence of noxious stimuli on electroencephalographic bicoherence as well as on the Bispectral Index (BIS) and the 95% spectral edge frequency (SEF95). MethodsThe authors enrolled 48 elective abdominal surgery patients (aged 22–77 years; American Society of Anesthesiologists physical status I or II). Raw electroencephalographic signals as well as BIS and SEF95 were recorded on a computer using a BIS® monitor (A-1050) and Bispectrum Analyzer (BSA) for BIS (the authors’ original software). Using BSA for BIS, the authors evaluated the two peak heights of electroencephalographic bicoherence. Anesthesia was induced with 3 mg/kg thiopental and was maintained with, in air–oxygen, 1.0% isoflurane or 1.5% sevoflurane. After confirming the steady state, the authors recorded baseline values. In experiment 1, they administered 3 &mgr;g/kg fentanyl 5 min after incision and investigated the changes in electroencephalographic derivatives at 5 and 10 min after incision. In experiment 2, they administered a similar dose of fentanyl 5 min before incision and investigated the changes in electroencephalographic derivatives immediately before and 5 min after incision. ResultsIn experiment 1, after incision, both peak heights of electroencephalographic bicoherence significantly decreased but returned to control values after fentanyl administration. By contrast, after incision, BIS and SEF95 showed individual variability. In experiment 2, although fentanyl itself did not affect all electroencephalographic derivatives before incision, the variables remained unchanged after incision. ConclusionNoxious stimuli decreased the peak heights of electroencephalographic bicoherence, an effect that was counteracted by fentanyl analgesia.

Comparison of adenosine triphosphate, microbiological load, and residual protein as indicators for assessing the cleanliness of flexible gastrointestinal endoscopes

BACKGROUND This study evaluated 3 potential indicators of gastrointestinal endoscope cleanliness: adenosine triphosphate (ATP), microbiological load, and protein. METHODS Before and after cleaning, ATP and microbiological load were determined from swabs of exterior surfaces and rinses of interior suction/accessory channels. Similarly, before and after cleaning, residual protein was determined from rinses of interior suction/accessory channels. RESULTS Before cleaning, ATP values were 10,417 relative light units (RLU) from the exterior endoscope surface and 30,281 RLU from the suction/accessory channel rinsates. After cleaning, these ATP values were decreased to 82 RLUs and 104 RLUs, a statistically significant difference. A similar trend was observed with microbiological load, but the change in residual protein from before cleaning to after cleaning was not significant. ATP values reliably reflected microbiological colony counts. CONCLUSIONS ATP measurement can provide a reliable, rapid and practical assessment of endoscope cleanliness for routine monitoring in the clinical setting.

Changes of Electroencephalographic Bicoherence during Isoflurane Anesthesia Combined with Epidural Anesthesia

Background The authors previously reported that, during isoflurane anesthesia, electroencephalographic bicoherence values changed in a fairly restricted region of frequency versus frequency space. The aim of the current study was to clarify the relation between electroencephalographic bicoherence and the isoflurane concentration. Methods Thirty elective abdominal surgery patients (male and female, aged 34–77 yr, American Society of Anesthesiologists physical status I–II) were enrolled. After electroencephalogram recording with patients in an awake state, anesthesia was induced with 3 mg/kg thiopental and maintained with oxygen and isoflurane. Continuous epidural anesthesia with 80–100 mg/kg 1% lidocaine was also administered. Using software they developed, the authors continuously recorded the FP1–A1 lead of the electroencephalographic signal and expired isoflurane concentration to an IBM-PC compatible computer. After confirming the steady state of each isoflurane (end-tidal concentration at 0.3, 0.5, 0.7, 0.9, 1.1, 1.3, and 1.5%), electroencephalographic bicoherence values were calculated. Results In a light anesthetic state, electroencephalographic bicoherence values were low (generally ≤ 15.0%). At increased concentrations of isoflurane, two peaks of electroencephalographic bicoherence emerged along the diagonal line (f1 = f2). The peak emerged at around 4.0 Hz and grew higher as isoflurane concentration increased until it reached a plateau (43.8 ± 3.5%, mean ± SD) at isoflurane 0.9%. The other peak, at about 10.0 Hz, also became significantly higher and reached a plateau (32.6 ± 9.2%) at isoflurane 0.9%; at isoflurane 1.3%, however, this peak slightly decreased. Conclusion Changes in the height of two electroencephalographic bicoherence peaks correlated well with isoflurane concentration.

Effectiveness of the ROBODOC system in preventing intraoperative pulmonary embolism.

Intraoperative pulmonary embolism occurs not only during cemented but also during cementless total hip arthroplasty (THA). We determined whether the ROBODOC femoral milling system can reduce intraoperative pulmonary embolism, by using of transesophageal echocardiography and hemo-dynamic monitoring. We did a prospective clinical trial with 71 patients (75 hips) who were divided into 2 groups: group 1, 46 patients (50 hips) who underwent cementless THA with preparation of the femoral canal using ROBODOC; group 2, 25 patients (25 hips) who underwent conventional cementless THA surgery in whom separate measurements were made during preparation of the femur, insertion of the stem and relocation of the hip. The incidence of severe embolic events was lower in group 1 than in group 2. Our findings suggest that the ROBODOC femoral milling system may reduce the risk of clinically significant pulmonary embolism during cementless THA

Serotonin2C receptor mRNA editing in neuropathic pain model.

We investigated the effects on 5HT(serotonin) 2C receptor RNA editing efficiency of contusive SCI (spinal cord injury). Using cloning followed by sequence analysis on spinal cord samples taken, we compared mRNA editing. Our results might be evidence of a functional adaptation mechanism in which increased expression of 5HT2C mRNA isoforms that encode receptors more sensitive to serotonin works to activate brainstem-spinal descending 5HT systems to, in effect, suppress transmission of nociceptive signals from primary afferent neurons to the spinal dorsal horn.

Arytenoid dislocation after cardiac surgery.

Occurring most usually as complications of upper aerodigestive tract instrumentation during endotracheal intubation or extubation, arytenoid cartilage dislocation and arytenoid subluxation are uncommon laryngeal injuries. Their precise cause, however, is usually difficult to determine. We encountered arytenoid dislocation following cardiac surgery requiring the use of transesophageal echocardiography (TEE). This case prompted us to review some of the mechanisms of injury to the cricoarytenoid joint. We conclude that even very subtle force may dislocate the arytenoid cartilage. We speculate that careless insertion of a TEE probe is mechanically capable of causing arytenoid dislocation and arytenoid subluxation.

Pregnancy does not enhance volatile anesthetic sensitivity on the brain: an electroencephalographic analysis study.

Backgrounds:Parturients are thought to be more sensitive to inhalational anesthetics because their minimum alveolar concentration is decreased. However, this conventional theory may be wrong, because, according to recent animal studies, minimum alveolar concentration indicates anesthetic effect on the spinal cord but not on the brain. The aim of this electroencephalographic study was to investigate the differences in the hypnotic effect of sevoflurane on parturients and nonpregnant patients. Methods:Fifteen parturients undergoing cesarean section and 15 patients undergoing elective gynecologic surgery were enrolled. Anesthesia was induced with 4 mg/kg thiopental, 2 &mgr;g/kg fentanyl, and 2 mg/kg suxamethonium or 0.15 mg/kg vecuronium. Anesthesia was maintained with sevoflurane and fentanyl. The electroencephalographic signals, obtained from the bispectral index monitor, were recorded on a computer. We calculated 95% spectral edge frequency, amplitude, and bicoherence using custom software (Bispectrum Analyzer for bispectral index). After confirming that end-tidal sevoflurane had reached equilibrium, we measured electroencephalographic parameters of sevoflurane at 2.0 and 1.5% during surgery and at 1.0 and 0.5% after surgery. Results:With the decrease of end-tidal sevoflurane concentration from 2.0 to 0.5%, 95% spectral edge frequency, amplitude, bispectral index, and bicoherence values changed dose-dependently in pregnant and nonpregnant women (P < 0.0001). However, there were no significant differences in those electroencephalographic parameters in pregnant and nonpregnant women. Conclusions:This electroencephalographic study has shown that pregnancy does not enhance hypnotic effect of sevoflurane. These results suggested that the decrease in minimum alveolar concentration during pregnancy does not mean an enhanced volatile anesthetic effect on the brain.

Infrared transmission of electronic information via LAN in the operating room.

Recent advances in technology have brought many kinds of monitoring devicesinto the operating room (OR). The information gathered by monitors can bechanneled to the operating ward information system via a local area network(LAN). Connecting patients to monitors and monitors to the LAN, however,requires a large number of cables. This wiring is generally inconvenient andparticularly troublesome if the layout of the OR is rearranged. From thispoint of view, wireless transmission seems ideally suited to clinicalsettings. Currently, two modes of wireless connectivity are available:radio-frequency (RF) waves or infrared (IR) waves. Some reports suggest thatRF transmission is likely to cause electromagnetic interference (EMI) inmedical devices such as cardiac pacemakers or infusion pumps. The risk ofmalfunctioning life-sustaining devices and the catastrophic consequences thiswould have on seriously ill patients rules out the use of RF. Here, we reportan IR system using IR modems for LAN connectivity in the OR. In this study,we focused on the possible detrimental effects of EMI during wirelessconnectivity. In our trial, we found no evidence of EMI of IR modems with anyof the medical devices we tested. Furthermore, IR modems showed similarperformance to a wired system even in an electrically noisy environment. Weconclude that IR wireless connectivity can be safely and effectively used inORs.