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Background: Intravenous (IV) infusions of volatile anesthetics in lipid emulsion may increase blood lipid concentration, potentially altering the anesthetic agent's blood solubility and blood-gas partition coefficient (BGPC). We examined the influence of a low-lipid concentration 20% sevoflurane emulsion on BGPC, and the anesthetic potency of this emulsion using dogs., Methods: We compared BGPC and anesthetic characteristics in 6 dogs between the IV anesthesia of emulsion and the sevoflurane inhalation anesthesia in a randomized crossover substudy. Minimum alveolar concentrations (MACs) were determined by tail-clamp stimulation by using the up-and-down method. Blood sevoflurane concentration and partial pressure were measured by gas chromatography; end-tidal sevoflurane concentration was measured using a gas monitor. The primary outcome was BGPC at the end of IV anesthesia and inhalation anesthesia. Secondary outcomes were time to loss/recovery of palpebral reflex, finish intubation and awakening, MAC, blood concentration/partial pressure at MAC and awakening, correlation between blood partial pressure and gas monitor, and the safety of emulsions., Results: BGPC showed no difference between IV and inhaled anesthesia (0.859 [0.850-0.887] vs 0.813 [0.791-0.901]; P = .313). Induction and emergence from anesthesia were more rapid in IV anesthesia of emulsion than inhalation anesthesia. MAC of emulsion (1.33% [1.11-1.45]) was lower than that of inhalation (2.40% [2.33-2.48]; P = .031), although there was no significant difference in blood concentration. End-tidal sevoflurane concentration could be estimated using gas monitor during IV anesthesia of emulsion. No major complications were observed., Conclusions: IV anesthesia with emulsion did not increase the BGCP significantly compared to inhalation anesthesia. It was suggested that the anesthetic potency of this emulsion may be equal to or more than that of inhalation., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2020 International Anesthesia Research Society.)

Disseminated carcinomatosis of the bone marrow (DCBM) is characterized by diffuse metastasis to bone marrow and sudden mortality. To the best of our knowledge, no studies to date have reported progression of oral squamous cell carcinoma to DCBM. Herein, we report a case of squamous cell carcinoma in the maxillary gingiva suspected of progressing to DCBM. A 64-year-old woman presented with white lesions on the left maxillary gingiva. The lesions were diagnosed as squamous cell carcinoma (T2, N0, M0), and partial maxillectomy performed. Two years and 5 months after surgery, metastasis was noted in the left cervical lymph node and left radical neck dissection carried out. The subsequent diagnosis was right cervical lymph node metastasis and multiple bone metastases. The patient also presented with thrombocytopenia, anemia, and elevated levels of alkaline phosphatase, probably due to metastatic bone disease. Although various antitumor therapies were administered, the patient died 6 months after diagnosis of multiple bone metastases.

In the present study, we evaluated activated areas of the cerebral cortex with regard to the mirror neuron system during swallowing. To identify the activated areas, we used magnetoencephalography. Subjects were ten consenting volunteers. Swallowing-related stimuli comprised an animated image of the left profile of a person swallowing water with laryngeal elevation as a visual swallowing trigger stimulus and a swallowing sound as an auditory swallowing trigger stimulus. As control stimuli, a still frame image of the left profile without an additional trigger was shown, and an artificial sound as a false auditory trigger was provided. Triggers were presented at 3,000 ms after the start of image presentation. The stimuli were combined and presented and the areas activated were identified for each stimulus. With animation and still-frame stimuli, the visual association area (Brodmann area (BA) 18) was activated at the start of image presentation, while with the swallowing sound and artificial sound stimuli, the auditory areas BA 41 and BA 42 were activated at the time of trigger presentation. However, with animation stimuli (animation stimulus, animation + swallowing sound stimuli, and animation + artificial sound stimuli), activation in BA 6 and BA 40, corresponding to mirror neurons, was observed between 620 and 720 ms before the trigger. Besides, there were also significant differences in latency time and peak intensity between animation stimulus and animation + swallowing sound stimuli. Our results suggest that mirror neurons are activated by swallowing-related visual and auditory stimuli.

With the founding of its Oral Cancer Center at the Ichikawa General Hospital, Tokyo Dental College established a support system for patients and family members that not only provides surgery and other conventional cancer-oriented treatments, but also palliative care, nutritional support, rehabilitation, and discharge support. With this in mind, the present study sought to examine the nature of support for oral cancer patients with postoperative eating and swallowing disorders by investigating these disorders and identifying their risk factors. The study population comprised 75 surviving oral cancer patients (46 men and 29 women) discharged from the Tokyo Dental College Oral Cancer Center following treatment over a 2-year period from April 2009 to March 2011. Risk factors affecting eating and swallowing function were identified by statistical analysis. Mean age of the patients was 67.3±13.7 years. Fifteen patients had stage I cancer, while 25 had stage II, 13 had stage III, and 22 had stage IV. The feeding route at the time of discharge was oral feeding in 74 patients and a combination of oral and gastrostomy tube feeding in 1 patient. The Tokyo Dental College Ichikawa General Hospital has standardized the expert evaluation and rehabilitation of oral cancer patients with eating and swallowing disorders by establishing a multidisciplinary support system from the preoperative stage onwards. In this context, the results of our analysis of factors influencing the ability of oral cancer patients to orally ingest food after treatment suggest that preoperative cancer stage classification, neck dissection, and tracheotomy are all influential factors. Patients affected by these factors require further multidisciplinary treatment, which in turn necessitates more extensive coordination with other medical professionals and community health care providers.

We analyze a duopolistic health care market in which a rural public hospital competes against an urban public hospital on medical quality, by using a Hotelling-type spatial competition model extended into a two-region model. We show that the rural public hospital provides excess quality for each unit of medical service as compared to the first-best quality, and the profits of the rural public hospital are lower than those of the urban public hospital because the provision of excess quality requires larger expenditure. In addition, we investigate the impact of the partial (or full) privatization of local public hospitals.

Background: Advancing a tracheal tube into the bronchus produces unilateral breath sounds. We created a Visual Stethoscope that allows real-time fast Fourier transformation of the sound signal and 3-dimensional (frequency-amplitude-time) color rendering of the results on a personal computer with simultaneous processing of 2 individual sound signals. The aim of this study was to evaluate whether the Visual Stethoscope can detect bronchial intubation in comparison with auscultation., Methods: After induction of general anesthesia, the trachea was intubated with a tracheal tube. The distance from the incisors to the carina was measured using a fiberoptic bronchoscope. While the anesthesiologist advanced the tracheal tube from the trachea to the bronchus, another anesthesiologist auscultated breath sounds to detect changes of the breath sounds and/or disappearance of bilateral breath sounds for every 1 cm that the tracheal tube was advanced. Two precordial stethoscopes placed at the left and right sides of the chest were used to record breath sounds simultaneously. Subsequently, at a later date, we randomly entered the recorded breath sounds into the Visual Stethoscope. The same anesthesiologist observed the visualized breath sounds on the personal computer screen processed by the Visual Stethoscope to examine changes of breath sounds and/or disappearance of bilateral breath sound. We compared the decision made based on auscultation with that made based on the results of the visualized breath sounds using the Visual Stethoscope., Results: Thirty patients were enrolled in the study. When irregular breath sounds were auscultated, the tip of the tracheal tube was located at 0.6 +/- 1.2 cm on the bronchial side of the carina. Using the Visual Stethoscope, when there were any changes of the shape of the visualized breath sound, the tube was located at 0.4 +/- 0.8 cm on the tracheal side of the carina (P < 0.01). When unilateral breath sounds were auscultated, the tube was located at 2.6 +/- 1.2 cm on the bronchial side of the carina. The tube was also located at 2.3 +/- 1.0 cm on the bronchial side of the carina when a unilateral shape of visualized breath sounds was obtained using the Visual Stethoscope (not significant)., Conclusions: During advancement of the tracheal tube, alterations of the shape of the visualized breath sounds using the Visual Stethoscope appeared before the changes of the breath sounds were detected by auscultation. Bilateral breath sounds disappeared when the tip of the tracheal tube was advanced beyond the carina in both groups.

Objective: The purpose of this study was to investigate the reliability of cardiac output (CO) measured by a new ultrasound dilution method (COud) in comparison with CO by pulmonary artery thermodilution (COtd) in adult patients undergoing surgery., Design: A prospective study., Setting: A university hospital, single institutional., Participants: Twenty-nine adult patients undergoing abdominal surgery., Measurements and Main Results: After approval of the institutional ethics review board, 29 adult patients were evaluated. After induction, radial and pulmonary artery catheters were inserted. A disposable extracorporeal AV loop was connected between existing arterial and central venous catheters. Reusable ultrasound sensors that measure changes in blood ultrasound velocity after dilution by isotonic saline were clamped onto the arterial and venous limbs of the loop. Ultrasound dilution (UD) measurements (COstatus; Transonic Systems, Inc, Ithaca, NY) were obtained by injecting 30 mL of body-temperature isotonic saline into the venous limb of the AV loop. An average of 3 COud and 5 COtd was obtained for comparison. Bland-Altman plot and correlation analysis were used for statistical comparison. A total of 142 comparison measurements were obtained. The correlation coefficient between the 2 techniques was r = 0.91. Bland-Altman analysis did not produce any significant bias (bias = 0.02, standard deviation = 0.56). The percentage error of these data was 23.53%., Conclusions: COud measurements agreed well with COtd. The results of this study indicated that COud might be interchangeable with conventional COtd in perioperative adult patients.

We investigate a health care market with uncertainty in a mixed duopoly, where a partially privatized public hospital competes against a private hospital in terms of quality choice. We use a simple Hotelling-type spatial competition model by incorporating mean-variance analysis and the framework of partial privatization. We show how the variance in the quality perceived by patients affects the true quality of medical care provided by hospitals. In addition, we show that a case exists in which the quality of the partially privatized hospital becomes higher than that of the private hospital when the patient's preference for quality is relatively high.

Background: Although hemorrhagic shock decreases the minimum alveolar concentration (MAC) of inhaled anesthetics, it minimally alters the electroencephalographic (EEG) effect. Hemorrhagic shock also induces the release of endorphins, which are naturally occurring opioids. We tested whether the release of such opioids might explain the decrease in MAC., Methods: Using the dew claw-clamp technique in 11 swine, we determined the isoflurane MAC before hemorrhage, after removal of 30% of the estimated blood volume (21 mL/kg of blood over 30 min), after fluid resuscitation using a volume of hydroxyethylstarch equivalent to the blood withdrawn, and after IV administration of 0.1 mg/kg of the mu-opioid antagonist naloxone., Results: Hemorrhagic shock decreased the isoflurane MAC from 2.05% +/- 0.28% to 1.50% +/- 0.51% (P = 0.0007). Fluid resuscitation did not reverse MAC (1.59% +/- 0.53%), but additional administration of naloxone restored it to control levels (1.96% +/- 0.26%). The MAC values decreased depending on the severity of the shock, but the alterations in hemodynamic variables and metabolic changes accompanying fluid resuscitation or naloxone administration did not explain the changes in MAC., Conclusions: Consistent with previous reports, we found that hemorrhagic shock decreases MAC. In addition, we found that naloxone administration reversed the effect on MAC, and we propose that activation of the endogenous opioid system accounts for the decrease in MAC during hemorrhagic shock. Such an activation would not be expected to materially alter the EEG, an expectation consistent with our previous finding that hemorrhagic shock minimally alters the EEG.

Background: Epidural anaesthesia is an efficient method of providing both regional anaesthesia and post-operative pain relief. Detection of the epidural space is critical, but it is difficult to predict the depth of the epidural space. Published results are inconsistent. We retrospectively investigated the differences in the depth of the epidural space depending on the puncture site, approach type and physical findings of patients., Methods: All surgical patients from 1994 to 2005 were included in the study and 4964 cases were analysed. The recorded distance from the needle tip to the skin surface was defined as the depth of the epidural. The differences in the depth were compared according to the puncture site, level and approach. We then searched for the factors determining the depth using multivariate regression analysis., Results: The depth in upper thoracic sites (T1/2-T9/10) was 5.0 (1.0) cm [mean (SD), n= 465] via the midline approach and 5.2 (1.0) cm (n= 1226) via the paramedian approach. For lumbar sites, the depth was 4.1 (0.9) cm (n= 1835) via the midline approach and 4.6 (1.0) cm (n= 298) via the paramedian approach. In the multivariate regression analysis, patient age, body weight and more cephalad puncture were significantly and positively correlated with the depth at thoracic sites., Conclusions: The epidural space was deeper at upper thoracic sites than lower thoracic or lumbar sites. The depth with the paramedian approach was greater than with the midline approach at both sites. Patient age and weight were positive factors for depth.

Background: beta-Adrenergic blocking agents may interact with anaesthetics, and several studies suggest that beta-blockers attenuate electroencephalographic responses during general anaesthesia. We have investigated the influence of landiolol, an ultra-short-acting beta 1-adrenoceptor antagonist, on the electroencephalographic effect of isoflurane in pigs., Methods: Ten swine were anaesthetized through inhalation of 2% isoflurane. The inhalational concentration was then decreased to 0.5% and maintained for 25 min, before being returned to 2% and maintained for a further 25 min (control period). After control measurements, infusion of landiolol (at 0.125 mg kg(-1) min(-1) for 1 min, and then at 0.04 mg kg(-1) min(-1)) was started. After a 20 min stabilization period, the inhalational concentration was varied as in the control period (40 gamma landiolol). Finally, infusion of landiolol was increased from 0.04 to 0.2 mg kg(-1) min(-1), and after a 20 min stabilization period, the inhalational concentration was again varied as in the control period (200 gamma landiolol). End-tidal isoflurane concentrations and spectral edge frequencies were recorded throughout the study. Analysis of the pharmacodynamics was performed using a sigmoidal inhibitory maximal effect model for spectral edge frequency vs effect-site concentration., Results: There were no significant differences in the effect of isoflurane among the conditions used. Landiolol did not shift the concentration-effect relationship [the effect-site concentration that produced 50% of the maximal effect was 1.35 (0.17)% under control conditions, 1.30 (0.12)% at 40 gamma landiolol, and 1.38 (0.30)% at 200 gamma landiolol]., Conclusion: Landiolol does not alter the electroencephalographic effect of isoflurane.

Background: The authors have previously reported that hemorrhage does not alter the electroencephalographic effect of isoflurane under conditions of compensated hemorrhagic shock. Here, they have investigated the influence of decompensated hemorrhagic shock and subsequent fluid resuscitation on the electroencephalographic effect of isoflurane., Methods: Twelve swine were anesthetized through inhalation of 2% isoflurane. The inhalational concentration was then decreased to 0.5% and maintained for 25 min, before being returned to 2% and maintained for 25 min (control period). Hemorrhagic shock was then induced by removing 28 ml/kg blood over 30 min. After a 30-min stabilization period, the inhalational concentration was varied as in the control period. Finally, fluid infusion was performed over 30 min using a volume of hydroxyethyl starch equivalent to the blood withdrawn. After a 30-min stabilization period, the inhalational concentration was again varied as in the control period. End-tidal isoflurane concentrations and spectral edge frequency were recorded throughout the study. The pharmacodynamics were characterized using a sigmoidal inhibitory maximal effect model for spectral edge frequency versus effect site concentration., Results: Decompensated hemorrhagic shock slightly but significantly shifted the concentration-effect relation to the left, demonstrating a 1.12-fold decrease in the effect site concentration required to achieve 50% of the maximal effect in the spectral edge frequency. Fluid resuscitation reversed the onset of isoflurane, which was delayed by hemorrhage, but did not reverse the increase in end-organ sensitivity., Conclusions: Although decompensated hemorrhagic shock altered the electroencephalographic effect of isoflurane regardless of fluid resuscitation, the change seemed to be minimal, in contrast to several intravenous anesthetics.

Background: Hypovolemia alters the effect of several intravenous anesthetics by influencing pharmacokinetics and end-organ sensitivity. The authors investigated the influence of hypovolemia on the effect of an inhalation anesthetic, isoflurane, in a swine hemorrhage model., Methods: Eleven swine were studied. After animal preparation with inhalation of 2% isoflurane anesthesia, the inhalation concentration was decreased to 0.5% and maintained at this level for 25 min before being returned to 2% (control). After 25 min, hypovolemia was induced by removing 14 ml/kg of the initial blood volume via an arterial catheter. After a 25-min stabilization period, the inhalation concentration was decreased to 0.5%, maintained at this level for 25 min, and then returned to 2% (20% bleeding). After another 25 min, a further 7 ml/kg blood was collected, and the inhalation concentration was altered as before (30% bleeding). End-tidal isoflurane concentrations and an electroencephalogram were recorded throughout the study. Spectral edge frequency was used as a measure of the isoflurane effect, and pharmacodynamics were characterized using a sigmoidal inhibitory maximal effect model for the spectral edge frequency versus end-tidal concentration., Results: There was no significant difference in the effect of isoflurane among the conditions used. Hypovolemia did not shift the concentration-effect relation (the effect site concentration that produced 50% of the maximal effect was 1.2 +/- 0.2% under control conditions, 1.2 +/- 0.2% with 20% bleeding, and 1.1 +/- 0.2% with 30% bleeding)., Conclusions: Hypovolemia does not alter the electroencephalographic effect of isoflurane, in contrast to several intravenous anesthetics.

The concentrations of nitrous oxide, sevoflurane and oxygen in the circle system of a closed-circuit anaesthesia machine, the PhysioFlex, were measured in seven patients. During anaesthesia, the settings for each gas were changed and their concentrations recorded. At the induction of anaesthesia, it took 80-510s (median 190s) for the end-tidal sevoflurane concentration to reach 2.0%, and 920-2640s (median 1500s) for the oxygen in the breathing circuit to reach 30%. At this time, the nitrous oxide concentration was 60+/-3% (mean+/-SD). During anaesthesia, it took 90-480s (median 140s) for the end-tidal sevoflurane concentration setting to decrease from 3.0 to 1.0%, and 90-400s (median 110s) to return from 1.0 to 3.0%. When the inspired oxygen was increased from 30 to 50%, circuit concentrations reached equilibrium in 40-60s (median 40s), and when decreased from 50% back to 30%, equilibrium took 310-470s (median 450s). During recovery from anaesthesia, inspiratory sevoflurane concentration took 40-70s (median 50s) to decrease to 0.2%. The PhysioFlex provided adequate control of sevoflurane and oxygen concentrations, but not of increasing nitrous oxide concentrations.

Sevoflurane anaesthesia was conducted using a totally closed circuit PhysioFlex anaesthesia machine (PhysioFlex group) or with a standard Modulus CD anaesthesia machine (Modulus group) (n = 8 in each group). The PhysioFlex was used under closed system conditions and the Modulus was used under low-flow system conditions (flow rate 1 litre min-1). Concentrations of sevoflurane degradation products and the temperature of soda lime were compared. Degradation products in the circuit were measured hourly, and the temperature of soda lime was monitored. The only degradation product detected was CF2 = C(CF3)-O-CH2F (compound A). Maximum concentrations of compound A were significantly lower (median 8.5 (range 5.4-15.9) ppm) in the PhysioFlex than in the Modulus group (21.2 (16.5-27.4) ppm) (P < 0.05). The maximum temperature of soda lime was also significantly lower in the PhysioFlex group (35.3 (32.1-36.3) degrees C vs 44.6 (43.0-47.1) degrees C, respectively) (P < 0.05). Hourly compound A concentrations were lower in the PhysioFlex group than in the Modulus group. End-tidal sevoflurane concentrations during measurement of degradation products were not different between groups. Therefore, use of the totally closed PhysioFlex system may significantly reduce compound A concentrations compared with low-flow anaesthesia using a standard anaesthesia machine.

Objective: To develop an ergonomically designed computerized recordkeeping tool for anesthesiologists that allows the clinician to maintain visual contact with the patient while performing recordkeeping., Methods: To simplify the human interface software, we developed two general use software components. All purpose menu type 1 (APM1) was used for entering events using a tree structured menu. APM1 was designed to adapt to the limits of human memory, by using Miller's rule of 7 to guide the input process. APM1 can be considered to be a three-dimensional table list consisting of 7 vertical and 7 horizontal choices, which has further 5 tree-structured divergences. APM1 is also completely configurable by the user. All purpose menu 2 (APM2) was used to implement the system-initiated human interface where the system will prompt the user by voice for each entry. When users touch a key on APM1 and APM2, the system was designed to respond with a voice prompt. A touch-screen was also utilized and designed to fit the anesthesia machine. The screen is equipped with a small speaker for voice response and a microphone for voice recognition. The positions of the screen are adjustable supported by a long flexible limb (85 cm)., Results: After improving the design, systems were assembled for 10 operating rooms. Of the multiple features of the VOCAAR user interface, the following were well accepted by users and employed daily: touch-screen input, and voice response. The noncompulsory use rate was 87% during the initial 2 weeks, increased to 94% after 2 weeks and 100% after two months. The mean sound emission by voice response (n = 10, mean +/- SD) was 8.2 +/- 2.3 dB at the main anesthetist site (35 cm from the speaker mounted on the touch-screen), 2.2 +/- 1.3 dB at the staff site (1.5 m from the touch-screen), which was only audible for anesthesiologist but for surgeon., Discussion: An EARK system was designed to allow the user to maintain visual contact with the patient while performing recordkeeping tasks. The combination of a mobile touch screen and voice response/recognition facilitated the design goals of the system. Although the system has enjoyed universal clinical acceptance, the voice functions remain too limited to satisfy the needs of a completely handsfree user interface. Enhancements to voice recognition technology will offer the potential for improved functionality. Additional research is also needed to better define the relationship between vigilance and visual contact with the patient.

Objective: In order to predict the partial pressure of volatile anesthetics in brain tissue, we developed a pharmacokinetic simulation model suitable for real time application. The accuracy of this model was examined by comparing the predicted values against measured values for blood sampled from the internal jugular vein, which was used as a measure of the partial pressure in the brain., Methods: Our model consists of six compartments: alveoli, arterial blood, a group of vessel-rich organs (VRG), muscle, fat, and venous blood. A volatile anesthetic, sevoflurane partial pressure in each compartment were calculated using the parameters of volume, blood flow, and solubility for each tissue as reported in previous studies. Simulated sevoflurane partial pressures in VRG were considered to reflect those in the brain. We studied 11 patients undergoing elective abdominal surgery or mastectomy. Sevoflurane was maintained at a concentration of 3% (by vaporizer setting) for 25 min. Sampling points were at 0 min (before sevoflurane administration) and 1, 2, 4, 9, 16, and 25 min after the start of inhalation. We measured the sevoflurane partial pressure in inspiratory gas (PI(S)), in end-expiratory gas (PET(S)), in arterial blood (Pa(S)), and in internal jugular vein blood (Pj(S)). These values were compared against those for the simulated brain (PB(S)sim)., Results: The sevoflurane partial pressures increased, in order from least rapid to most rapid, as follows: Pj(S), PB(S)sim, Pa(S), PET(S), and PI(S). The differences between Pj(S) and PB(S)sim were significantly smaller than those between Pj(S) and PET(S) at all sampling points. PB(S)sim did not differ significantly from Pj(S) at any sampling points after 4 min of inhalation, while PET(S) differed significantly from Pj(S) at all sampling points., Conclusion: We conclude that our model is clinically useful for predicting sevoflurane partial pressure in the brain, assuming that Pj(S) reflects the sevoflurane partial pressure in the brain.

Background: The propofol awakening concentration can vary. However, the effect site awakening propofol concentration will be a fixed value. The purpose of this study was to determine the awakening propofol concentrations obtained from infusion Schede using abrupt discontinuation of propofol (half-maximal effective concentration [EC50]) or a descending decrease in concentration to allow blood-effect site equilibration (EC50eq)., Methods: Patients undergoing short-term (group 1) and long-term (group 2) elective surgery were anesthetized with computer-assisted continuous infusion of propofol and fentanyl, with both groups receiving the same propofol (3 microg/ml) and fentanyl (1 ng/ml) concentrations 20-30 min before the end of surgery until the end. Then both groups were further divided into two subgroups: subgroup A abrupt discontinuation, and subgroup B descending concentrations of propofol (15-min duration per concentration). In the A subgroups, the response to verbal command was evaluated every 30 s. In the B subgroups, the blood propofol concentrations just permitting and just preventing response to command were averaged individually. The EC50 and EC50eq values were determined by probit analysis., Results: The EC50 of group 1A was 1 microg/ml, which was significantly less than the 1.6 microg/ml of group 2A (P < 0.05). The awakening time of group 1A was 5.2 +/- 1.8 min, which was significantly shorter than the 9.3 +/- 3.5 min of group 2A (means +/- SD). The EC50eq of both groups 1B and 2B was 2.2 microg/ml., Conclusions: The EC50eq was independent of propofol infusion length, compared with the EC50. Thus the potential for hysteresis during emergence from propofol anesthesia was confirmed.

Tension pneumoperitoneum may force gas into a small injured vessel if the opening is kept patent by surrounding tissues. However, the amount of carbon dioxide (CO2) that penetrates through injured or noninjured peritoneum has not been systematically determined. In 25 patients undergoing elective laparoscopic ultrasonography and cholecystectomy, CO2 output (VCO2) and O2 uptake (VO2) were measured at baseline and during anesthesia, pneumoperitoneum, laparoscopic surgical procedure (Surgery), and after hemostasis of the surgical field (Postsurgery). Before anesthesia, VCO2/BSA and VO2/BSA were 97.7 +/- 11.3 and 116.0 +/- 10.0 ml x min(-1) x m(-2), respectively. During anesthesia, they fell to 72.3 +/- 6.0 and 89.8 +/- 7.6 ml x min(-1) x m(-2), respectively (p < 0.05). VCO2/BSA increased to 96.0 +/- 11.1 at pneumoperitoneum (p < 0.05) and increased further to 126.1 +/- 11.0 ml x min(-1) x m(-2) at Surgery. It fell to 111.7 +/- 10.9 ml x min(-1) x m(-2) Postsurgery. VO2/BSA remained unchanged during pneumoperitoneum. Minute volume increased from 2.24 +/- 0.20 in anesthesia to 2.89 +/- 0.25, 4.01 +/- 0.32, and 3.46 +/- 0.28 L x min(-1) x m(-2) during pneumoperitoneum, Surgery, and Postsurgery, respectively, to maintain PaCO2. We conclude that the amount of CO2 absorbed following pneumoperitoneum prior to surgery is lower than that during Surgery or Postsurgery. The amount of CO2 absorbed through the surgical field was 2.3 times higher than that through the nonsurgical field while that from the peritoneum after hemostasis of surgical field was 1.6 times higher.

Long-time oral intake of magnesium-silicate-containing drugs is thought to be a causative factor inducing silicate urolithiasis. Besides, magnesium seems to play an anti-urolithogenic part in the formation of calcium oxalate stones. We report a recurrent calcium oxalate former who had been treated with magnesium aluminometasilicate antacid for gastric ulcer for approximately 17 years. One of the fragments found during extracorporeal shock wave lithotripsy was identified as 100% silicate. Deposition of silica was also found on other fragments. A large dose of magnesium (given in a part of the drug) might have little influence on the formation of calcium oxalate.

We developed a miniature mixing chamber, the bymixer, that aids in the measurement of respiratory gas metabolism and inhalation anesthetic uptake. A small fraction of total respiratory gas flow is bypassed from the inspiratory or expiratory limb of the breathing circuit to the bymixer. We tested the relationship between total flow and bypass flow. To analyze the error and response time of the system, we compared the mixed expired carbon dioxide from the bymixer (capacity, 0.3 L, ratio of bypass flow to total flow, 1/4.5) with that from a conventional 2.0-L mixing chamber in 15 volunteers and 12 anesthetized patients during spontaneous or controlled ventilation. Bypass flow correlated well with total flow (r2 = 0.999 to 1.000) when total flow ranged from 0 to 70 L/min and the ratio of bypass flow to total flow ranged from 1/3 to 1/20. The difference between the values of mixed expired carbon dioxide from the two mixing chambers was small, ranging from -0.03 to 0.01 vol% in both of the ventilatory modes. The relative error was within 2.3% of the carbon dioxide values obtained from the conventional chamber. We observed the error at the lowest minute volume (4 L/min). The 90% response time of the bymixer (24.8 seconds) was similar to that of the conventional chamber (19.1 seconds) at a minute volume of 7.5 L/min. For clinical use, we combined a conventional breathing circuit with two bymixers, one for mixing inspired gas and the other for mixing expired gas. We found this device accurate and easy to use.