Individual indicators of appropriate hypnotic level during propofol anesthesia: highest alpha power and effect-site concentrations of propofol at loss of response.

BACKGROUND: Electroencephalogram (EEG) waveforms vary widely among individuals, this decreases the usefulness of BIS™ monitors for assessing the effects of propofol. Practically, anesthesia is only seen as too deep when evidence of burst-suppression is seen. We designed an experiment to help towards better assessment of individual anesthetic needs. First, to mark the Ce (effect-site concentration) of propofol at loss of response to calling name and gently shaking shoulders (LOR), we defined Ce-LOR. To mark the transient power increase in the alpha range (9-14 Hz), common to all patients, when propofol concentration gradually increases, we defined Ce-alpha as the highest recorded alpha power for Ce. We also defined Ce-OBS as the Ce of propofol at initial observation of burst-suppression. Then we tried to predict Ce-LOR and Ce-alpha from Ce-OBS, vice versa, and considered the significance of these parameters. METHODS: We enrolled 26 female patients (age 33-65) who were undergoing scheduled mastectomy. During anesthesia, we recorded all raw EEG packets as well as EEG-derived parameters on a computer from BIS-XP™ monitor. Propofol was infused using a TCI pump. Target concentration was adjusted so that Ce of propofol was gradually increased. RESULTS: We obtained the following regression equation; Ce-alpha or Ce-OBS = Ce-LOR × 0.87 + 1.06 + dummy × 0.83 (for Ce-alpha dummy = 0, and for Ce-OBS = 1; adjusted r = 0.90, p < 2.2e-16) by ANCOVA. At Ce-alpha, BIS was 50.2 ± 7.7. CONCLUSION: Ce-alpha and Ce-OBS could be estimated from Ce-LOR. Based on Ce-LOR it is possible to manage the hypnotic level of individual patients.

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.

The impact of nitrous oxide on electroencephalographic bicoherence during isoflurane anesthesia.

BACKGROUND: We previously reported that electroencephalographic (EEG) bicoherence, the degree of phase coupling among the frequency components of a signal, showed 2 peaks during isoflurane anesthesia. Hayashi et al. (Br J Anaesth 2007;99:389-95) also revealed that the peak frequency of bicoherence around 10 Hz increased when ketamine was added. Because nitrous oxide (N(2)O) and ketamine share several common features, they are often treated as the same category of anesthetic. Here, we investigated the effect of N(2)O on EEG bicoherence and other EEG derivatives during isoflurane anesthesia. METHODS: Twenty patients (aged 34-72 years, ASA physical status I and II) of either gender who underwent elective laparoscopic surgery were included. Raw EEG data, along with EEG-derived parameters, were recorded using an A-1050 Bispectral Index (BIS) monitor and our self-authored Bispectral Analyzer for BIS software. We compared 2 peaks of EEG bicoherence (pBIC-low, around 4 Hz; and pBIC-high, around 10 Hz), as well as BIS and spectral edge frequency 95% (SEF95). Anesthesia was induced with 3 mg · kg(-1) thiopental and 3 µg · kg(-1) fentanyl. After tracheal intubation, anesthesia was maintained with isoflurane (expired concentration at 1.0%), oxygen, and nitrogen. Fentanyl was added and maintained at an estimated effect-site concentration of >1.5 ng · mL(-1). We obtained baseline data 1 hour after induction of anesthesia, then 70% N(2)O was added for 30 minutes. RESULTS: Before N(2)O, pBIC-low and pBIC-high were 49.3% ± 8.3% and 42.4% ± 11.0%. Ten minutes after starting N(2)O, pBIC-high decreased to 14.9% ± 5.9% (P < 0.001), and it was statistically significantly lower throughout the N(2)O period. Meanwhile, pBIC-low transiently decreased to 37.2% ± 12.8% (P = 0.01) during the early phase of N(2)O administration. Before N(2)O, BIS and SEF95 were 43.2 ± 4.9 and 13.1 ± 2.0 Hz, respectively. Both BIS and SEF95 slightly but statistically significantly decreased during N(2)O administration. Fifteen minutes after starting N(2)O, BIS and SEF95 were 35.7 ± 6.2 (P < 0.001) and 8.6 ± 1.8 Hz (P < 0.001) and they decreased more when large δ waves emerged. Fifteen minutes after stopping N(2)O, BIS, SEF95, as well as pBIC-low and pBIC-high returned to pre-N(2)O values. CONCLUSION: Dissimilar to the effect of ketamine, N(2)O significantly decreases pBIC-high during isoflurane anesthesia.

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 microg/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.

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.

Incidence of embolic events during acetabular prosthesis insertion in total hip arthroplasty, and effect of intramedullary decompression in preventing embolism: higher risk of embolism with one-piece type prosthesis.

PURPOSE: In total hip arthroplasty (THA), there is a high risk of bone marrow embolism during femoral prosthesis insertion. However, the incidence during acetabular prosthesis insertion has received less attention. The first goal of this study was to determine the incidence of bone marrow embolism associated with acetabular prosthesis insertion. The second goal was to evaluate the effects of intramedullary decompression of the acetabulum in suppressing bone marrow embolism. METHODS: To achieve the first goal, we evaluated the effects of prosthesis insertion on the incidence of bone marrow embolism, and on respiratory and cardiovascular dynamics. For the evaluation of bone marrow embolism, images obtained by transesophageal echocardiography were rated using Pitto's classification. To achieve the second goal, patients undergoing THA with a one-piece type acetabular prosthesis were divided into a control group and an acetabulum-decompression group, and the effects of insertion were analyzed in the same fashion. RESULTS: In the 150 patients in the study, bone marrow embolism was rated as grade 0 in 9, grade 1 in 46, grade 2 in 61, and grade 3 in 34 patients. Patients rated as grade 2 and 3 exhibited significant reductions in blood pressure and Pa(O) (2) 5 min after acetabular prosthesis insertion. The results of multivariate analysis suggested that the incidence of bone marrow embolism was higher for the one-piece type prosthesis than for the two-piece type. Among the 60 patients who underwent THA with a one-piece type prosthesis, the incidence of bone marrow embolism was significantly lower in the decompression group. CONCLUSION: As there are increasing indications for one-piece type acetabular prostheses in Japan, we must pay attention to the possibility of bone marrow embolism, not only during femoral prosthesis insertion but also during acetabular prosthesis insertion.

[Teaching the use of fiberoptic intubation in anesthetized patients].

BACKGROUND: Fiberoptic bronchoscope (FOB)-guided intubation is an important and useful technique for unanticipated difficult airway in anesthetized patients. However, many staff anesthesiologists seemed to find it difficult to perform. We speculated that it was because they had not been well trained in the technique. We worked out an easy method for FOB-guided intubation. We had our residents try our method and measured the elapsed time in introducing FOB from the mouth to the tracheal carina. METHODS: After IRB approval and having obtained informed consent, we enrolled twenty residents with experience of two to four years and twenty patients scheduled for thoracic surgery. After induction of anesthesia, we inserted a Berman airway and let the residents try to introduce FOB from the mouth to the tracheal carina. Staff anesthesiologists gave verbal advises only by watching the video image and we measured the elapsed time. RESULTS: The elapsed time was 83+/-43 sec (mean+/-SD). Although three residents required interruptions for ventilation during their trials, they were able to accomplish their missions in their second or third attempt. In all cases, Sp02 was kept at 100% throughout the trials. CONCLUSIONS: We showed that our method helped anesthesiologists to master FOB-guided intubation.

Suctioning prevents emboli during insertion of acetabular components without holes.

Embolic events can occur when inserting uncemented press-fit acetabular components (cups), especially those without holes. However, there is a paucity of literature regarding prevention of embolic events. We asked whether suctioning in the acetabulum might be as effective as suctioning during femoral insertion. We compared embolic events in 30 hips (27 patients) (Group 1) that had conventional press-fit cup fixation without holes, with 30 hips (27 patients) (Group 2) treated by suctioning from a cannula in the ilium during cup impaction. We evaluated embolic events using transesophageal echocardiography, blood gas (PaO2, PaCO2), and blood pressure preoperatively and 5 minutes after cup placement. Echocardiography showed less severe embolic events in Group 2 (23%) than in Group 1 (100%). The decrease in rate of the PaO2 and the blood pressure from baseline to 5 minutes after cup placement were lower in Group 2 than in Group 1. Our data suggest the suctioning technique is effective to reduce embolic events by cup without holes which may cause intraoperative embolic complications.

Electroencephalographic bicoherence is sensitive to noxious stimuli during isoflurane or sevoflurane anesthesia.

BACKGROUND: The 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). METHODS: The 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 microg/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. RESULTS: In 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. CONCLUSION: Noxious stimuli decreased the peak heights of electroencephalographic bicoherence, an effect that was counteracted by fentanyl analgesia.

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 hemodynamic 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.

[Occupational exposure of operating room staff to anesthetic gases during inhaled induction--a comparison with intravenous anesthesia induction].

BACKGROUND: The risk of occupational exposure to waste anesthetic gases still remains during inhaled induction. In this study we investigated how much we were occupationally exposed to anesthetic gases during induction period. METHODS: Twenty-six adult patients were induced with sevoflurane 5% using a face mask for three minutes and maintained with sevoflurane 1% after end-tracheal intubations (IH-Group). Twenty-two adult patients were induced with intravenous anesthetics and maintained with sevoflurane 1% after end-tracheal intubations(IV-Group). The concentration of sevoflurane was measured by Multi-gas Monitor 1302 (Bruel & Kjaer: Denmark) every 70 seconds. Sample gas was suctioned from breathing zone of anesthesiologists. All of our operating rooms are equipped with waste gas scavenging system. RESULTS: The peak concentration of sevoflurane is significantly higher in IH-Group (15.91 +/- 22.64 ppm) compared with IV-group (0.36 +/- 0.25 ppm). The period when sevoflurane concentration exceeded 0.5 ppm is significantly longer IH-Group (18.55 +/- 10.51 min.) compared to IV-Group (1.92 +/- 4.56 min.). CONCLUSION: The induction with intravenous anesthetics is a better method in order to reduce occupational exposure of anesthesiologists to anesthetic gases.

Embolic events during total hip arthroplasty: an echocardiographic study.

We performed transesophageal echocardiography on 88 patients treated with cementless or hybrid total hip arthroplasty (THA). We observed a significantly higher frequency of severe embolic events among patients without cup holes during insertion of press-fit cups (46.0%) than in patients with holes (15.6%) (P<.005). During stem insertion, severe embolic events occurred in 61.5% of hybrid operations and 5.9% of cementless operations. PaO(2), systolic blood pressure, and arterial oxygen saturation decreased significantly in severe embolic events (P<.05). The results indicate that embolic events may occur during THA whether or not cement is used. Based on these findings, we make several recommendations for technique modifications during insertion of both femoral and acetabular components in THA.

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 < or = 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.