The Antoine equation is a semi-empirical equation which expresses vapour pressure as a function of temperature. A new, rapid and highly accurate method for obtaining its three constants from experimental data is presented and applied to ethanol, water and 14 anaesthetic substances. Alternative vapour pressure equations are discussed and references for original temperature--vapour pressure data are summarized. A series of equations utilizing vapour pressure is detailed: these formulas are of use in both the practice and teaching of anaesthesia.
BACKGROUND:Pediatric patients with isolated severe traumatic brain injury (TBI) treated at pediatric trauma centers (PTCs) have lower mortality than those treated at adult trauma centers (ATCs) or mixed trauma centers (MTCs). The primary objective of this study was to determine if adolescent patients (15-17 years) with isolated severe TBI also benefited from treatment at PTCs. METHODS:This was a cross-sectional analysis using a national sample of adolescent trauma patients obtained from the American College of Surgeons' Trauma Quality Program Participant Use Files for 2013 to 2017 (n = 3,524). Mortality, the primary outcome variable, was compared between Level I PTCs, ATCs, and MTCs using multiple logistic regression controlling for patient characteristics and injury severity. Secondary outcomes included discharge disposition, utilization of craniotomy, intensive care unit (ICU) utilization, ICU length of stay (LOS), and hospital LOS. RESULTS:Prior to adjustment, patients treated at ATCs (odds ratio [OR], 2.76; p = 0.032) and MTCs (OR, 2.36; p = 0.070) appeared to be at greater risk of mortality than those treated at PTCs. However, after adjustment, this difference disappeared (ATC OR, 1.21; p = 0.733; MTC OR, 0.95; p = 0.919). Patients treated at ATCs and MTCs were more severely injured than those treated at PTCs and more likely to be admitted to an ICU (ATC OR, 2.12; p < 0.001; MTC OR, 1.91; p < 0.001). No other secondary outcome differed between center types. CONCLUSION:Adolescent patients with isolated severe TBI treated at ATCs and MTCs had similar mortality risk as those treated at PTCs. The difference in injury severity across center types warrants additional research.
SummaryA study was undertaken to investigate the changes in pressure inside the epidural space in parturients in the$rst stage of labour. The purpose was to see whether acute local pressure changes in the epidural space were consistent with the hypothesis that there is physical movement of cerebrospinal j u i d with certain changes in maternal posture. Pressure changes were measured via the epidural catheter through which continuous infusion epidural analgesia was administered, using a pressure transducer kept at the level of the lumbar spine. The mothers moved through a series of postures that rejected those expected during the course of labour and delivery. The pressure within the catheter was recorded during these manoeuvres. The pressure changes which were found, taken in conjunction with the associated investigations of others, are consistent with the hypothesis. Key wordsAnaesthetic techniques, regional; epidural. Anaesthesia; obstetric.The evidence provided in clinical supports the hypothesis4 that physical movement of cerebrospinal fluid (CSF) after change of posture is the principal reason for high levels of spinal analgesia in late pregnancy. Acute changes in epidural pressure after alterations in maternal posture could provide indirect evidence in support of the hypothesis.Epidural pressure is an indirect indicator of CSF pressure,5 which in turn is a reflection of venous pressure. Change in venous pressure is transmitted directly to the CSF. The 'venous wall' which separates CSF from the thoracic abdominal and external pressures is extremely elastic6 There will be a pressure gradient if external pressure on the venous wall suddenly becomes greater in the lumbosacral section than in the thoracic section. It will cause an immediate shift of CSF cephalad, after which CSF pressure will rapidly revert to normal limits. Marx et al.,7 have shown that in the normal pregnant woman at term in the supine position, CSF pressures are within normal limits.The unique situation in obstetrics is the liability to rapid changes in the degree of inferior vena caval compression with alterations in maternal posture. The changes are reflected in epidural pressure changes. It is necessary to make immediate measurement of epidural pressure after alterations in posture, in order to gain an indication of its likely effect on the movement of CSF.Sprague* found that the most rapidly achieved, as well as the most effective, subarachnoid blocks for Caesarean section were obtained when the mothers received the injection lying on their right sides and were turned immediately through supine to the left semilateral position. Our interpretation is that this would guarantee transient and covert inferior vena caval compression sufficient to cause a cephalad surge of CSF. There is an increase in epidural pressure when posture is altered from lateral to supine even without caval compression.* The effect of caval compression is additive. Baseline extradural pressures decrease when it is relieved by left uterine displacement (LUD) in the sup...
SummaryWe report a case df profound hypotension, after induction of Key wormComplications; cardiac tamponade, bradycardia. Case historyA 25-year-old male student was admitted as an emergency after transfer by mountain rescue RAF helicopter over a distance of 60 miles. He had fallen some 30 metres on to scree while hill-walking in the Scottish Highlands.He was pale in appearance, drowsy but conscious and orientated, on arrival in the Accident and Emergency Department. He gave a history of a few seconds loss of consciousness but no retrograde amnesia. On examination, there were multiple superficial abrasions over legs, buttocks, chest, back, arms and face, and a large haematoma over his forehead with a laceration at the hair line. His back was tender over the upper lumbar vertebrae and there was a compound fracture dislocation of the right elbow. Sternal tenderness was noted but rib springing was pain free. Pupils were equal and reacting to light and there were no focal neurological signs. His core temperature was 32°C increasing to 3 5 T , and his arterial blood pressure was 90 mmHg systolic on admission. For this reason he had received 400 ml of plasma protein solution and 1 unit of SAG-M blood. These had been administered into a central vein cannula inserted via a low right supraclavicular approach. Arterial blood pressure was subsequently recorded as 120/56 mmHg, and pulse as 80/minute, sinus rhythm. Air entry on chest auscultation was equal on both sides with no added sounds. Abdominal palpation revealed neither tenderness nor distension.Chest and skull X rays were normal in appearance but abdominal films showed evidence of ileus, as well as some free peritoneal fluid. Dorsal spine X ray revealed a compression wedge fracture of the body of the first lumbar vertebra. A right elbow dislocation and separated fracture of the medial epicondyle were noted.White cell count was raised at 42.5 x 109/litre, haemoglobin was 120 g/litre, platelets 400 x 109/litre. Electrolytes were normal and the urea was 8.7 mmol/litre. Arterial blood gas analysis (no2, 0.5) showed a pH of 7.1 I , Pco2 6.3 kPa, Po2 24 kPa, and a base deficit of 13.5 mmol/litre. The orthopaedic surgeons wished to proceed with internal fixation urgently, in view of the compound dislocation fracture of the elbow, accompanied by lavage and dressing of the various lacerations and abrasions. Arrangements for theatre were made, since the patient was apparently stable.Peripheral venous access was established with an intravenous 16-gauge cannula inserted into a left forearm vein, after arrival in the anaesthetic room. Blood was already being given slowly via the internal jugular cannula. Anaesthesia was induced, after 5 minutes pre-oxygenation, with intravenous alfentanyl 1 mg, thiopentone 150 mg and suxamethonium 100 mg, and cricoid pressure was applied. A 9-mm cuffed oral tracheal tube was inserted and the lungs were ventilated using a Manley Pulmovent ventilator, set to deliver a minute volume of 9 litres of 50% nitrous oxide in oxygen with isoflurane 0.5-...
The authors measured the relative permittivity of SiO2 deposited with a focused Ga+ ion beam by creating small parallel plate capacitors on a gold substrate. The relative permittivity of SiO2 ranged from a low of 7.5 to a high of 10.5 depending on the deposition yield, Y, defined as the film volume per ion dose. Lower Y led to the incorporation of metallic Ga0 clusters that increased the relative permittivity. The authors then used the SiO2 to create a parallel plate capacitor that acted as a capacitive delay in a 28 nm technology circuit to improve performance and timing marginality. The circuit segment in question had failed at an overvoltage of 106.1% of the nominal value, providing insufficient margin of operation and reliability. The addition of a 20 fF capacitor increased the upper limit of the performance margin from 106.1% to 108.5% of nominal supply voltage. The realized circuit edit provided conceptual confirmation that an additional delay in the clock signal would improve device performance as predicted by modeling.
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