Yoshio Kinefuchi

Relationship between aortic-to-radial arterial pressure gradient after cardiopulmonary bypass and changes in arterial elasticity.

Background An aortic-to-radial arterial pressure gradient may develop during and after cardiopulmonary bypass (CPB). The mechanisms of this pressure gradient remain controversial. To clarify the cause of the pressure gradient after CPB, the authors investigated the relationship between the pressure gradient and changes in the pulse wave velocity (PWV) before and after CPB. Methods The pressure gradient from the aorta to the radial artery and a change in PWV were measured with a wire (0.37 mm in diameter) tipped with a miniature pressure transducer in 12 patients undergoing cardiac surgery. The pressure distributions and waveforms were measured and recorded with electrocardiograph. The PWV was calculated by measuring the propagation time between the R wave of the electrocardiograph and the rising point of the arterial pressure waveform at 10-cm intervals. Results After CPB, 7 of 12 patients demonstrated a marked pressure gradient. In these patients, the pressure distribution showed a gradual decrease toward the periphery without a precipitous step-down in pressure at any one specific anatomic location. The PWV decreased as the intraarterial pressure decreased from the aorta to the radial artery, and the relative arterial elasticity decreased linearly toward the periphery. Conclusions The results showed that the decrease in PWV implies a decrease in arterial elasticity, and the decrease in the arterial elasticity correlated with the decrease in intraarterial pressure. These findings demonstrated that a radial artery pressure lower than the aortic pressure after CPB may be due to the decrease in arterial elasticity.

One-lung ventilation with the Univent tube in a pediatric patient undergoing video-assisted thoracoscopic surgery

required. In order to obtain a deflated lung for VATS, it was imperative to use an uncuffed Univent tube 8mm in external diameter, because the patient’s tracheal size was 10mm, as observed from the preoperative chest Xray (Fig. 1). No premedication was given. Anesthesia was induced by injecting 60mg of propofol, 25 μg of fentanyl, and 3mg of vecuronium intravenously. A small, uncuffed Univent tube, 3.5 mm in internal diameter was the placed in the trachea (Fig. 2). After induction of general anesthesia, a blocker tube was advanced into the right main bronchus under bronchoscopy, and a blocker balloon was positioned in place to deflate the right lung. A 22-gauge catheter was placed in the left radial artery. General anesthesia was maintained with 40%–100% oxygen and sevoflurane; occasionally, nitrous oxide and intravenous fentanyl (total, 200 μg) were administered. After pressure controlled ventilation (PCV) had been initiated, arterial blood gas analysis under bilateral ventilation showed a pH of 7.385, PaCO2 of 43.7mmHg, and PaO2 of 158mmHg, with a peak airway pressure of 15 cmH2O, FiO2 of 0.4, and ventilation frequency of 10 ·min21. By inflating the blocker cuff, we could block the right bronchus. However, a leak of anesthetic gas around the tracheal tube became obvious at an airway pressure of 18 cmH2O, causing difficulty in maintaining the static airway pressure of 20cmH2O. We expected that the proper levels of PaCO2 and PaO2 could be maintained during one lung anesthesia by increasing the frequency of ventilation. After the posture of the patient had been changed to the lateral position, one-lung anesthesia was initiated, and the fully deflated right lung was provided with a blocker cuff of 2.5ml. However, the leak increased beyond expectation, and the patient developed hypercapnia. The results of arterial blood analysis were pH 7.291, PCO2 66.3mmHg, and PO2 107 mmHg, with PCV peak airway pressure 20 cmH2O, ventilation frequency 15 ·min21, and 100% oxygen. Gauze was packed into the

Use of personal computers for translation and publication of an anesthesia textbook

We used personal computers extensively for translating and publishing in Japanese an anesthesia textbook originally written in English. The procedure included optical character recognition, scanning of figures, use of computer translation, use of electronic mail and computer type-setting. While these have individually been done previously, this is process of any medical textbook published in Japanese. The advantages of combining these technologies are good exchange of information among individual authors/translators, rapid translation process, preliminary visualization of the final product, and overall high quality of the published book.

Density-modulated t's array, a new technique of processed electroencephalogram, for monitoring the effects of midazolam and nitrous oxide during spinal anesthesia

We have investigated the utility of a new electroencephalogram (EEG) processing system, density-modulated ts array (DTA), which we have installed in a laptop personal computer together with density-modulated spectral array (DSA) for clinical monitoring. Ten patients scheduled for orthopedic operations on the lower extremities were anesthetized with 0.5% bupivacaine intrathecally, 50% nitrous oxide in oxygen by mask, and midazolam at a dose of 0.1 mg/kg intravenously. Immediately following the administration of the drugs, the power at the frequencies between 15 and 20 Hz increased. However, the power at these higher frequencies disappeared gradually and the power in the delta band and the smaller one in the alpha band became predominant. This pattern of dominant-band shift on the DSA and DTA was observed in all the patients. In three of the patients, the sedation level remained stable as judged by the absence of body movement, quiet, regular breathing and stable hemodynamics as well as steady EEG frequency distribution throughout the operations. They awoke from anesthesia rapidly on withdrawal of nitrous oxide, with return of the power at the higher frequencies. In the other seven patients, the power at the higher frequencies suddenly reappeared on the DSA and DTA during operation and slight movements of the head and upper limbs were observed with rises in blood pressure and heart rate. In three of these seven patients, the EEG change notably preceded the physiological activities by a few minutes. On the DTA, the occurrence of any significant clinical phenomenon was displayed in a color representing at value greater than ±3. The DTA, testing power changes in the EEG at each 1-Hz interval for significant difference, permits the visual and quantitative assessment of EEG changes.

Natural frequency/damping coefficient relationship of the catheter-manometer system required for high-fidelity measurement of the pulmonary arterial pressure.

Using a digital simulation method, we analyzed the relationship between natural frequency (fn) and damping coefficient (ζ) of the catheter-manometer system required for high-fidelity measurement of the pulmonary arterial pressure. The pulmonary artery pressure waveform was obtained with a catheter-tip transducer and it was fed into a dynamic simulator programmed on a computer. The original waveform and the output of the simulator were compared and judged visually for the fidelity. From this analysis, the combination offn and ζ was obtained and was plotted on afn-ζ diagram. It showed as an area, which was convex on the left side and open on the right side. The left-convex endpoint was located at a damping coefficient of about 0.1. At a lower heart rate, this area was extended to the lower frequency side, while, at a higher heart rate, this area was limited to the higher frequency side. Thefn-ζ diagram was also constructed theoretically by calculating the relations between natural frequencies and damping coefficients of a second order system with the amplitude and phase error tolerance set at +/-5% respectively.

Management of Anesthesia Record Using Hyper-Text System

Transfer and storage of pertinent data from original anesthesia records into a data base on personal computers for future reference involve the difficult problems of who and how to do input chores. The process should be user-friendly, that is, it should be simple enough so that any inexperienced users (residents) can handle it. Also, there should be some safe-guards against inevitable mistyping or misspelling errors on the keyboard. Just as much important is the standardized nomenclature in terms of diagnosis, operative procedure and drugs and so forth, otherwise the data base is of no practical use. Extensive lists of standardized diagnostic, procedural, pharmaceutical terms relevant to each surgical subspecialties have been compiled in our department from our own anesthesia records accumulated during the past 15 years. They have been in use on packaged soft-wares (e.g. DBASE III) as well as on programs of our own compilation in data processing and statistical works. The present work is an additional step in facilitating data-input chores by incorporating our diagnostic/procedural lists to “Hypertext” on Macintosh PC making full use of the device of mouse and minimizing the need for keyboard input. Figure 1 shows the tree structure of Hypertext, and Figure 2 shows examples of the contents of Hypertext cards for otolaryngology displaying anatomical sites of the disease, diagnostic categories, and operative procedures associated respectively.

Intra-Operative EEG Monitoring: Monitoring of Background Rhythm and Paroxysmal Activity

The value of EEG monitoring as noninvasive brain monitoring in patients under anesthesia or in critical conditions is readily conceived but simple observation of running EEG wave patterns tells very little. Detection of abrupt appearances of deviation from the on-going background patterns would certainly be helpful in early recognition of grave changes in cerebral function or metabolism. We have developed a prototype EEG analyzer capable of doing this.

An Assessment of Fequency Characteristics of the Fluid-Filled Catheter-Manometer System

A pulmonary artery pressure waveform observed on the screen is an end-product of the force applied to the tip of the catheter subjected to various distortions as it travels down through the mass of fluid in the lumen with its inherent inertial, frictional and elastic moments. The aim of this study is to construct a system of evaluation of the distortion in the pressure waveforms in terms of amplitude and phase angle. The experimental setup consists of the pressure source (a loudspeaker), measurering chamber (a dome) which is open to the reference transducer and the second transducer through the length of the pulmonary artery catheter. The pressure output of the latter is fed to the personal computer through an AD converter and are plotted against frequency.