Thoracoabdominal aortic aneurysm repair: interplay of spinal cord protecting modalities.

BACKGROUND: The purpose of this study was to assess the complementary use of different methods of measuring spinal cord perfusion during thoracoabdominal aortic surgery. METHODS: The spinal cords of 28 patients undergoing surgery on the thoracoabdominal aorta were monitored with transcranial electrical stimulation (tcMEP) and somatosensory-evoked potentials (SSEP). Available approaches of spinal cord-protection included: Moderate systemic hypothermia, constant cerebrospinal fluid (CSF) drainage and pressure monitoring, reimplantation of segmental arteries, cardiopulmonary bypass (CPB), and staged clamping. RESULTS: Fourteen of 19 patients (75%) undergoing open surgical treatment (Group I) exhibited loss of tcMEP after proximal aortic clamping. In nine cases (47%), we observed recovery of tcMEP after intraoperative interventions, while two patients subsequently developed paraplegia and three died. Seventeen of 19 patients showed loss of SSEP, with recovery in 12 cases (63%). During stent-graft implantation (Group II), one of nine patients (11%) demonstrated tcMEP loss with intraoperative, intervention-related recovery. The SSEP-recording course remained stable. CONCLUSIONS: tcMEP/SSEP monitoring has proved to be an excellent means of detecting spinal cord ischaemia during surgery on thoracoabdominal aortic aneurysms. The prognostic value of tcMEP monitoring should be considered superior to that of SSEP measurements, because of its direct and rapid response to spinal malperfusion. Through combined neurophysiological monitoring, vital parameter balancing and intraoperative interventions, spinal cord perfusion improves and recovery of tcMEP and SSEP is achievable, reducing the prevalence of postoperative paraplegia.

Improved spinal cord perfusion during thoracoabdominal aortic repair.

OBJECTIVES: The study's aim is to evaluate whether intraoperative neurophysiological monitoring with transcranial motor-evoked potentials (tcMEP) permits early recognition of neuronal lesions, thus making interventions to prevent irreversible spinal cord damage possible. MATERIAL AND METHODS: TcMEP monitoring was carried out in twelve patients (mean age 60 years) during open surgical thoracoabdominal aortic replacement. Current approaches for corrective, spinal cord-protecting interventions consist of: raising distal perfusion by increasing cardiopulmonary bypass (CPB) flow, catecholamine application, reducing central venous pressure, reimplantation of segmental arteries, and cerebrospinal fluid (CSF) drainage. RESULTS: Nine patients exhibited loss of tcMEP after segmental aorta clamping. In five patients we observed a recovery of tcMEP through counteractive measures. Three patients died intraoperatively, one patient presented with postoperative paraplegia and loss of tcMEP. CONCLUSION: TcMEP loss is associated with spinal cord ischaemia, causing postoperative paraplegia. TcMEP monitoring is an excellent method to detect spinal cord ischaemia at an early stage.

Setup of neurophysiological monitoring with tcMEP/SSEP during thoracoabdominal aneurysm repair.

OBJECTIVES: The article describes a procedure for the intraoperative neurophysiological placement of electrodes to control the spinal cord function during thoracoabdominal aortic aneurysm repair. MATERIAL AND METHODS: Intraoperative monitoring is performed by motor-evoked myogenic potentials after transcranial electric stimulation (tcMEP) and somatosensory-evoked potentials (SSEP). In tcMEP, the stimulating percutaneous needle electrodes are placed at C3 and C4 according to the 10 - 20 system for EEG recordings. TcMEP are recorded from the anterior tibial and gastrocnemius muscles on both sides. The SSEP electrodes are placed laterally and caudally onto the malleolus medialis in order to stimulate the tibial nerve. The stimulus is documented via electrodes attached to the scalp within the sensory cortex region. RESULTS: The application of the electrodes is both easy to learn and can be performed without further difficulties. Once attached, the electrodes provide a quick assessment and interpretation of spinal cord function. The identification of external sources of disturbance during the monitoring (e. g. insufficient impedance, unfavourable electrode positioning, and technical interference caused by medical equipment) enables the supervisor to differentiate between normal and abnormal neurological responses. CONCLUSIONS: TcMEP and SSEP allow an adequate, direct, and reliable intraoperative assessment of spinal cord function, enabling the surgeon to diagnose an impending ischaemia and act accordingly. This measurement technique provides the surgical team with a means of integrating neurological aspects during thoracoabdominal aneurysm repair.

Detection of hypoglycemia with the GlucoWatch biographer.

OBJECTIVE: Hypoglycemia is a common acute complication of diabetes therapy. The GlucoWatch biographer provides frequent and automatic glucose measurements with an adjustable low-glucose alarm. We have analyzed the performance of the biographer low-glucose alarm relative to hypoglycemia as defined by blood glucose < or = 3.9 mmol/l. RESEARCH DESIGN AND METHODS: The analysis was based on 1,091 biographer uses from four clinical trials. which generated 14,487 paired (biographer and blood glucose) readings. RESULTS: The results show that as the low-glucose alert level of the biographer is increased, the number of true positive alerts (alarm sounds and blood glucose < or = 3.9 mmol/l) and false positive alerts (alarm sounds but blood glucose >3.9 mmol/l) increased. When analyzed as a function of varying low-glucose alert levels, the results show receiver operator characteristic curves consistent with a highly useful diagnostic tool. Setting the alert level from 1.1 to 1.7 mmol/l above the level of concern is likely to optimize the trade-off between true positives and false positives for each user. When the same blood glucose data are analyzed for typical monitoring practices (two or four measurements per day), the results show that fewer hypoglycemic events are detected than those detected with the biographer.

A constraint on eliminating semantic priming by repeating a prime.

Repeated semantic primes have been shown to generate an additive semantic priming effect when those primes are different words, but repetition priming of the prime seems to eliminate semantic priming of lexical decisions for reasons that are not clear. These studies replicated this effect but also showed that repetition priming of the prime does not eliminate semantic priming with a longer lag between the repeated primes. The implications of these results for understanding the basic effect are discussed.

The GlucoWatch biographer: a frequent automatic and noninvasive glucose monitor.

The GlucoWatch (Cygnus, Inc, Redwood City, CA, USA) biographer provides automatic, frequent and noninvasive blood glucose measurements for up to 12 h. The device extracts glucose through intact skin where it is measured by an amperometric biosensor. Clinical trials in a variety of environments have shown that the biographer provides accurate and precise glucose measurements when compared with serial fingerstick blood glucose measurements. Mean difference between these measurements was 0.26 mmol/L in the home environment (r = 0.80). Over 94% of biographer readings were in the clinically acceptable A+B region of the Clarke Error Grid. A slight positive bias is observed for the biographer readings at low glucose levels. Biographer precision, as measured by coefficient of variation (CV)%, is approximately 10%. The low glucose alert function of the biographer was able to detect up to 75% of hypoglycaemic episodes with a low false alert level. Skin irritation, characterized by erythema and oedema was either nonexistent or mild in over 87% of subjects and resolved in virtually all subjects without treatment in several days. The GlucoWatch biographer has been shown to be a safe and effective method to track glucose level trends and patterns, which should enable improved glycaemic control for many patients.

Noninvasive glucose monitoring: comprehensive clinical results. Cygnus Research Team.

CONTEXT: Intensive diabetes management using frequent blood glucose measurements to guide therapy has been shown to significantly improve short- and long-term outcomes. Development of a device that makes possible frequent, automatic, painless, and accurate measurements of glucose would facilitate intensive management. OBJECTIVE: To determine the accuracy of the GlucoWatch automatic glucose biographer (Cygnus Inc) compared with that of serial blood glucose measurements. DESIGN: Multicenter comparative study of the GlucoWatch biographer and the HemoCue blood glucose analyzer (Aktiebolaget Leo) performed between August 29 and October 17, 1998. Participants wore up to 2 biographers during the 15-hour study session and performed 2 fingersticks per hour for comparative blood glucose measurements. The biographers were calibrated with a single HemoCue measurement after a 3-hour warm-up period. Diet and insulin were manipulated to produce a broad glycemic range during the study. SETTING: Controlled clinical environment at 2 diabetes centers and 3 contract research organizations in the United States. PARTICIPANTS: A total of 92 subjects (mean [SD] age, 42.1 [15.1] years; 59.8% women) with type 1 or 2 diabetes requiring treatment with insulin. MAIN OUTCOME MEASURES: Mean error, mean absolute error, correlation, slope, and intercept using Deming regression, and clinical significance of differences between biographer readings and blood glucose measurements using the Clarke error grid. RESULTS: Results showed close tracking of blood glucose over a range of 2.2 to 22.2 mmol/L (40-400 mg/dL) for up to 12 hours using a single point calibration. The biographer readings lagged behind serial blood glucose values by a mean of 18 minutes. An analysis of 2167 data pairs shows a linear relationship (r = 0.88; slope = 1.03; intercept = -0.33 mmol/L [-6 mg/dL]) between biographer readings and serial glucose measurements. The mean absolute error between the 2 measurements was 15.6% (mean error [SD], -0.07 [1.82] mmol/L [-1 [33] mg/dL]), and 96.8% of the data fell in the therapeutically relevant regions of the error grid analysis. CONCLUSION: These results demonstrate close agreement between GlucoWatch biographer readings and blood glucose measurements using repeated fingerstick blood samples. The automatic, frequent, and noninvasive measurements obtained with the biographer provides more information about glucose levels than the current standard of care.

Synthesis and biological evaluation of 4-chloro-3, 5-dinitrobenzotrifluoride analogues as antileishmanial agents.

Desnitro analogues of 4-chloro-3,5-dinitrobenzotrifluoride (chloralin) (2), an in vitro microtubule inhibitor of several Leishmania species, have been synthesized from 2-halo-5-(trifluoromethyl)benzenesulfonyl chlorides 4 and 5. The analogues exhibited moderate to excellent activity when tested against Leishmania donovani amastigotes in vitro. Two representative compounds, 7f and 8, were tested against the Khartoum strain of L. donovani in a hamster model using chloralin (2) and Glucantime (one of the current therapeutics of choice in the treatment of Leishmania) as standards, the results of which will be discussed herein.

Critical phenomena and thermodynamics of dilute aqueous sodium chloride to 823 K.

Semiempirical equations are developed that represent the behavior of dilute solutions of NaCl in water (steam) in the range 723-823 K where ion pairing is extensive. This supplements the equations given earlier for more concentrated solutions. In this temperature range the system NaCl/H(2)O shows critical behavior with two phases below the critical pressure. The equations for the dilute solutions yield critical behavior. Though the equations for concentrated solutions do not yield critical behavior at the critical pressure, only a very small interpolation function is required to connect smoothly the two equations. The ion-pairing equilibrium constants are reported as well as the Gibbs energies of hydration for both ions and ion pairs.

Thermodynamics of aqueous sodium chloride to 823 K and 1 kilobar (100 MPa).

It is shown that a very simple semiempirical equation represents quite accurately the thermodynamic properties of aqueous sodium chloride from 373 to 823 K. The equation comprises one Margules term and a Debye-Hückel term. Just the one Margules parameter is freely adjustable because the Debye-Hückel parameter is determined by the properties of water. The equation is valid from the saturation composition down to infinite dilution for solvent density above 0.75 g.cm(-3) but at lower density only above a solute mole fraction of about 0.1 on an ionized basis. Both solute and solvent activity coefficients are fitted from the lowest pressure of solution existence up to 1 kilobar (1 bar = 100 kPA). Derivation of enthalpy and other related functions is discussed.

Dielectric constant of water at very high temperature and pressure.

Pertinent statistical mechanical theory is combined with the available measurements of the dielectric constant of water at high temperature and pressure to predict that property at still higher temperature. The dielectric constant is needed in connection with studies of electrolytes such as NaCl/H(2)O at very high temperature.

Phase equilibria for highly unsymmetrical plasmas and electrolytes.

The conclusion of classical Debye-Hückel theory that a phase separation may occur in highly unsymmetrical plasmas or electrolytes is shown to be false and to arise from a serious error in the treatment of the interaction of pairs of the most highly charged ions. After an approximate correction for this error, no phase separation is predicted. Specific application to iron in the solar plasmas is discussed.

How Much Research?: The educational aspect is crucial in justifying further growth in research.

In conclusion, I believe the components which I have discussed constitute an outline of a sound program for federal support of science in universities, which provides first, a basic minimum of funding proportional to the growth of the research student population, and second, a pattern of grants based upon justified need and individual merit for more costly instruments, post-doctoral appointments, and other factors that allow our best scientists to be more productive. In addition, there is, of course, the array of major national facilities and programs, each judged individually, in fields requiring very costly equipment.