Technologies to microfabricate electrochemical sensors and systems are rapidly advancing and will surely have an impact on critical fields such as medicine, environment, and information processing. It is a good opportunity to review the state of the art and trends in the technologies developed in this field during the last two decades of the 20th century and prepare for the coming decades. Here, developed electrochemical microsensors and microsystems will be reviewed in terms of techniques and performance along with the problems left as issues for the next century.

Advances in the Microfabrication of Electrochemical Sensors and Systems

https://www.internationaljournalofcardiology.com/article/S0167-5273(14)01646-5/pdf

CNS disease triggering Takotsubo stress cardiomyopathy.

A measurement concept has been realized for the detection of carbon dioxide, where the CO2 induced pressure generation by an enclosed pH-sensitive hydrogel is measured with a micro pressure sensor. The application of the sensor is the quantification of the partial pressure of CO2 (Pco2) in the stomach as diagnosis for gastrointestinal ischemia. The principle is put to the proof by examining the sensor response to changes in Pco2. Furthermore, the response time, temperature-sensitivity and resolution are determined. The sensor responds well to changes in Pco2 with a maximum pressure generation of 0.29× 105 Pa at 20 kPa CO2. The 90% response time varies between 1.5 and 4.5 minutes at 37∘C. The sensor shows a linear temperature-sensitivity which can easily be compensated for, and enables detection of Pco2 changes as small as 0.5 kPa CO2.

A Miniaturized Carbon Dioxide Gas Sensor Based on Sensing of pH-Sensitive Hydrogel Swelling with a Pressure Sensor

A 77-year-old female was admitted in our hospital for uterine prolapse surgery. She developed ventricular tachycardia during induction of general anaesthesia and after initial symptomatic measures, she was transferred to the coronary care unit. Heart failure persisted and electrocardiographic changes mimicking acute myocardial infarction appeared. Coronary angiography was normal and left ventriculography revealed akinesis of the apical region of the left ventricle and apical ballooning during systole, with relative sparing of the base of the heart. Complete recovery of left ventricular function occurred 8 days after the initial onset of symptoms. A diagnosis of Takotsubo syndrome was made on the basis of consistent clinical and laboratory findings, typical echocardiography and angiography findings, and reversible course. This case emphasises the importance of being aware of uncommon causes of cardiac dysfunction in stressful situations, especially during induction of general anaesthesia.

/pdf/takotsubo-syndrome-during-induction-of-general-anaesthesia-9at2vqcc0k.pdf

Takotsubo syndrome during induction of general anaesthesia

To permit CO 2 measurements behind stomatal pores of plant leaves a potentiometric CO 2 -biosensor was built with a tip diameter of 2 μm. The miniaturised sensor assembly consists of a H + carrier-based pH-microelectrode concentrically arranged within a sheathing micropipette. The tip of the latter is filled with carbonate buffer, the pH of which quickly responds to CO 2 concentration changes due to incorporated carbonic anhydrase. The CO 2 -microsensor shows a linear response to CO 2 in the physiologically relevant concentration range of 50–800 ppm (5.1–81.1 Pa). The 90% response time varied from sensor to sensor between 18 and 63 s (mean±S.E., 42±14 s; n =6). Sensor calibration and leaf experiments were performed in an open-flow tube-like minicuvette, allowing tangential air flow along the leaf surface with controlled gas mixtures and flow rates of choice. At 800 ppm external CO 2 concentration, CO 2 within the leaf was close to the external CO 2 concentration when stomatal pores were wide open. However, the concentration dropped to 350 ppm during stomatal closure due to CO 2 consumption by photosynthesis demonstrating distinct CO 2 -sensing of internal leaf CO 2 . Following ‘light-off’ internal CO 2 rapidly rose close to 700 ppm, a response which was completely reversed by ‘light-on’. We conclude that this sensor is a suitable tool for CO 2 monitoring in places too small to be accessible to conventional tools.

Miniaturised carbon dioxide sensor designed for measurements within plant leaves

A 75-year-old woman with amyotrophic lateral sclerosis (ALS) underwent surgical gastrostomy and repair of incisional hernia Anesthesia was induced with propofol and high concentrations of sevoflurane Tracheal intubation was performed without muscle relaxants Anesthesia was maintained with sevoflurane and thoracic epidural anesthesia (bupivacaine and fentanyl) Surgery, emergence and extubation were completed uneventfully She was transferred to ICU for postoperative observation On the 2 nd POD, however, she was re-intubated due to sudden dyspnea and desaturation caused by failed sputum exhaustion Simultaneously, her ECG showed ischemic change in leads I, III, aVF, and V3-6 Left ventriculogram showed an "Ampulla" or so called "Takotsubo" shape with intact coronary angiogram After medication with nitroglycerin and diltiazem, her ECG returned to normal She showed no deterioration of neurological symptoms No respiratory and cardiac events were reported until her discharge from hospital We conclude that an extreme care is required in patient with ALS to avoid perioperative complications

["Takotsubo" cardiomyopathy developed in the postoperative period in a patient with amyotrophic lateral sclerosis].

Gastric PCO2 monitoring during canine hemorrhagic shock encountered occasional baseline drift to higher direction when conventional PCO2 sensor was used. As a result of chemical analysis of gastric juice of dogs and human, hydrogen sulfide and acetic acid were identified as causative compounds. It was speculated that these weak acid molecules would permeate gas-permeable silicone membrane to be accumulated in the inner solution of Severinghaus-type PCO2 sensors. In order to prevent this phenomenon, double-membrane type PCO2 sensor was constructed. In this sensor, acid-neutralizing solution was installed between the inner and the outer membranes in order to dissociate weak acid molecules into corresponding ions, which can not diffuse into the inner silicone membrane. In addition, Cu2O particles were mixed in the inner silicone membrane to trap hydrogen sulfide in this membrane. It was confirmed by experiments in vitro that the readings of improved gastric PCO2 sensors were not affected by acetic acid or hydrogen sulfide. As a result of a preliminary clinical evaluation, continuous monitoring of gastric PCO2 was carried out for 72 h without detectable baseline drift or the change of sensitivity.

Gastric PCO2 monitoring system based on a double membrane type PCO2 sensor

待機的胃癌手術に持続硬膜外麻酔併用全身麻酔を行ったところ, 術直後からTh10以下の感覚および運動神経麻痺を呈した症例を経験した. 術後の硬膜外造影で血腫は否定された. MRIおよび脊髄造影の所見から脊髄動静脈奇形 (arterio- venous malformation: AVM) と診断した. 胸髄完全麻痺のため, 外科的治療の適応がなく, 治療はメチルプレドニゾロンの大量投与とリハビリとなった. 2ヵ月後対麻痺が回復することはなく, 合併症の悪化により死亡した. あらかじめ無症候性の脊髄AVMを診断することは困難であるが, 硬膜外麻酔後に対麻痺が出現したときには留意すべき疾患の１つと考える.

A Case of a Spinal Arteriovenous Malformation Discovered after General Anesthesia Combined with Epidural Anesthesia

Anesthetic Management in a Patient with Pulmonary Artery (PA) Perforation by PA Flow-directed Catheter

A 31-year-old man was admitted to the ICU with a diagnosis of primary pulmonary hypertension and severe hypoxemia caused by hemoptysis. Examinations revealed 112/56mmHg of systemic artery pressure, 113/54mmHg of pulmonary artery pressure and a PaO2/FIO2 ratio of 87. Continuous intravenous infusion of PGE1 and dopamine worsened the pulmonary hypertension. Continuous intravenous infusion of PGE1 and amrinone improved pulmonary hypertension (75/53mmHg; vs. systemic artery pressure 110/70mmHg) and raised the PaO2/ FIO2 ratio to 300.The patient died of massive hemoptysis several days later, however amrinone may be an effective agent for treating primary pulmonary hypertension.

https://www.jstage.jst.go.jp/article/jsicm1994/4/4/4_4_371/_pdf

Satoshi Ohtsu

Papers

["Takotsubo" cardiomyopathy developed in the postoperative period in a patient with amyotrophic lateral sclerosis].

Gastric PCO2 monitoring system based on a double membrane type PCO2 sensor

A Case of a Spinal Arteriovenous Malformation Discovered after General Anesthesia Combined with Epidural Anesthesia

Anesthetic Management in a Patient with Pulmonary Artery (PA) Perforation by PA Flow-directed Catheter

Beneficial effects of amrinone in a patient with primary pulmonary hypertension and severe hypoxemia