CONTROL OF END-TIDAL HALOTHANE CONCENTRATION: Part B: Verification in Dogs

Conventional anaesthetic techniques do not allow for the automatic control of end-tidal halothane concentration and, therefore, brain concentration cannot be predicted. In this study, eight dogs were ventilated with halothane in oxygen using a new closed-loop anaesthetic breathing system which provided a constant end-tidal concentration. During the first 60 min the end-tidal concentration was maintained at 0.87 vol% (1 MAC). Then followed 60 min of halothane wash-out and a further 120-min period of halothane at 1.74 vol% (2 MAC). Halothane concentrations were measured in the inspired and expired air, and in the arterial, cerebral venous and mixed venous blood. Haemodynamic and respiratory variables were measured. The system reached 95% of the target end-tidal concentration within 6 min without over-shooting. After 2 h of wash-in, significant gradients still persisted between end-tidal, arterial and cerebral venous blood concentrations. Measured uptake differed from theoretically calculated uptake by 18.3-57.6%, depending on the model used. Measured arterial and cerebral venous concentrations differed from theoretically calculated values by 7% and 17.5%, respectively. It was shown that the required end-tidal concentrations can be obtained rapidly and accurately, and that brain tissue concentrations can be predicted within certain limit

DETERMINATION OF THE PARTIAL PRESSURE OF HALOTHANE (OR ISOFLURANE) IN BLOOD

A gas chromatographic method is described for the direct quantitative determination of the partial pressure of halothane {or isoflurane) in blood as well as the blood-gas partition coefficient. A head space technique and a flame ionization detector were used. Standard blood was obtained by equilibrating patients' blood with known gas concentrations in a tonometer. Using an infra-red analyser to measure the halothane gas concentration in the tonometer and within the anaesthetic system allowed for the direct comparison of the partial pressure in blood to the partial pressure in the inspired gas. Technical problems associated with this procedure, and with comparable methods, are discusse

Post-Transplant Diabetes Mellitus in Renal Allograft Recipients: A Matched-Pair Control Study

The incidence of post-transplant diabetes mellitus was evaluated retrospectively in 901 consecutive renal transplant recipients. Thirty-two (3.6%) patients developed diabetes mellitus requiring drug therapy. 18 of 32 became hyperglycaemic within 3 months of transplantation. Post-transplant diabetes mellitus occurred in 24 of 628 (3.8%) patients treated with conventional therapy consisting in azathioprine and prednisone, and in 8 of 273 (2.9%) patients receiving cyclosporin A (CsA) in addition (triple therapy). To identify predisposing factors 32 nondiabetic patients matched for age, sex, number of graft, immunosuppressive protocol, and graft function at onset of diabetes were used as case controls. Thirteen of 32 patients with diabetes mellitus and 5 of 32 control patients had abnormal glucose tolerance pretransplant (P<0.025). HLA-B8 was significantly more frequent in patients with post-transplant diabetes mellitus than in control patients (9 of 29 vs 2 of 31, (P<0.02). Twelve (38%) patients became diabetic during or immediately after anti-rejection therapy with intravenous pulse prednisone. Four diabetic patients experienced chronic pancreatitis pre-transplant. Family history of diabetes mellitus, bodyweight, number of rejection episodes, and immunosuppressive drug doses were similar in both groups. Actuarial patient and graft survival was not significantly different in diabetic patients and controls, although 10-year data tended to be better in controls. Thus, post-transplant diabetes mellitus was not a frequent complication in patients sometimes predisposed by an impaired glucose tolerance pre-transplant and was triggered by pulse prednisone therapy in 38

IS THE END-TIDAL PARTIAL PRESSURE OF ISOFLURANE A GOOD PREDICTOR OF ITS ARTERIAL PARTIAL PRESSURE?

End-tidal partial pressure of isoflurane (PE′iso) may be used as a measure of anaesthetic depth. During uptake, an arterial partial pressure (Paiso) which is considerably less than PE′iso(Paiso/PE′iso<<1) leads to underestimation of depth of anaesthesia and, during elimination, PE′iso/Paiso<<1 will lead to an overestimation of anaesthetic depth. We measured Paiso/PE′iso during a 60-min uptake period of 1% isoflurane and PE′iso/Paiso during the subsequent 60-min elimination period in 26 patients (age 13-88 yr, ASA I-III) undergoing various surgical procedures. After 15 min of isoflurane uptake, Paiso/PE′iso of 26 patients was mean 0.78 (SD 0.10) and this increased only marginally at 60 min (0.79 (0.09)), whereas during elimination, PE′iso/Paiso was in the range 0.79 (0.14)-0.83 (0.11). Predictability of Paiso in a given patient is hindered by the high SD of Paiso/PE′iso and PE′iso/Paiso, but it may be improved by taking into account age, ASA physical status category, vital capacity, inspired minus end-tidal isoflurane partial pressure and arterial minus end-tidal carbon dioxide partial pressure during uptake; and obesity, end-tidal isoflurane partial pressure and arterial minus end-tidal carbon dioxide partial pressure during elimination. However, even with multiple regression analysis (to account for the various possible variables), clinically useful prediction of Paiso/PE′iso and PE′iso/Paiso in a particular patient is not possible (residual SD 0.084 and 0.113, respectively

Production of Ultra-Cold-Neutrons in Solid \alpha-Oxygen

Our recent neutron scattering measurements of phonons and magnons in solid \alpha-oxygen have led us to a new understanding of the production mechanismen of ultra-cold-neutrons (UCN) in this super-thermal converter. The UCN production in solid \alpha-oxygen is dominated by the excitation of phonons. The contribution of magnons to UCN production becomes only slightly important above E >10 meV and at E >4 meV. Solid \alpha-oxygen is in comparison to solid deuterium less effcient in the down-scattering of thermal or cold neutrons into the UCN energy regime.Comment: 4 pages, 5 figuer

The Magnetic Distortion Calibration System of the LHCb RICH1 Detector

The LHCb RICH1 detector uses hybrid photon detectors (HPDs) as its optical sensors. A calibration system has been constructed to provide corrections for distortions that are primarily due to external magnetic fields. We describe here the system design, construction, operation and performance.Comment: 9 pages, 14 figure

Optimal interpolation of satellite and ground data for irradiance nowcasting at city scales

We use a Bayesian method, optimal interpolation, to improve satellite derived irradiance estimates at city-scales using ground sensor data. Optimal interpolation requires error covariances in the satellite estimates and ground data, which define how information from the sensor locations is distributed across a large area. We describe three methods to choose such covariances, including a covariance parameterization that depends on the relative cloudiness between locations. Results are computed with ground data from 22 sensors over a 75×80 km area centered on Tucson, AZ, using two satellite derived irradiance models. The improvements in standard error metrics for both satellite models indicate that our approach is applicable to additional satellite derived irradiance models. We also show that optimal interpolation can nearly eliminate mean bias error and improve the root mean squared error by 50%

HST/WFPC2 morphologies and color maps of distant luminous infrared galaxies

Using HST/WFPC2 imaging in F606W (or F450W) and F814W filters, we obtained the color maps in observed frame for 36 distant (0.4<z<1.2) luminous infrared galaxies (LIRGs), with average star formation rates of ~100 M_sun/yr. Stars and compact sources are taken as references to align images after correction of geometric distortion. This leads to an alignment accuracy of 0.15 pixel, which is a prerequisite for studying the detailed color properties of galaxies with complex morphologies. A new method is developed to quantify the reliability of each pixel in the color map without any bias against very red or blue color regions.Based on analyses of two-dimensional structure and spatially resolved color distribution, we carried out morphological classification for LIRGs. About 36% of the LIRGs were classified as disk galaxies and 22% as irregulars. Only 6 (17%) systems are obvious ongoing major mergers. An upper limit of 58% was found for the fraction of mergers in LIRGs with all the possible merging/interacting systems included. Strikingly, the fraction of compact sources is as high as 25%, similar to that found in optically selected samples. From their K band luminosities, LIRGs are relatively massive systems, with an average stellar mass of about 1.1x10^11 solar mass. They are related to the formation of massive and large disks, from their morphologies and also from the fact that they represent a significant fraction of distant disks selected by their sizes. The compact LIRGs show blue cores, which could be associated with the formation of the central region of these galaxies. We suggest that there are many massive disks still forming a large fraction of their stellar mass since z=1. For most of them, their central parts (bulge?) were formed prior to the formation of their disks.Comment: 20 pages, 14 figures, accepted for publication in A&