The three-way stopcock may be a weak component of total intravenous anaesthesia

Background: An intravenous line is needed to administer anaesthesia, particularly when total intravenous anaesthesia (TIVA) is performed. A disadvantage of TIVA is that the intravenous concentration of anaesthetics cannot be easily measured compared with volatile anaesthetics. If a three-way stopcock is accidentally unscrewed, TIVA drugs cannot reach the patient's veins, thus resulting in inadequate anaesthesia levels, possibly resulting in awareness. We therefore measured the required torque to open five different brands of three-way stopcocks in an attempt to make an intravenous-line including all elements safer.
Methods: The torque required to open one, two or three three-way stopcocks being connected in a perpendicular manner was measured with a biaxial servo hydraulic material testing machine.
Results: The force required to open three-way stopcocks connected with an intravenous catheter ranged in five different stopcock models from 5.03±0.75 to 2.21±0.51 N respectively; with two three-way stopcocks from 2.68±0.42 to 1.31±0.59 N, respectively, and with three three-way stopcocks from 1.29±0.27 to 0.82±0.05 N, respectively.
Conclusion: Turning a three-way stopcock to become loose with possibly leaking drugs requires minimal amounts of force and decreases significantly if not connected in-line.     

AMNIOTIC FLUID CONCENTRATIONS OF 3,3'',5''-TRI-IODOTHYRONINE (REVERSE T3), 3,3''-DI-IODOTHYRONINE, 3,5,3''-TRI-IODOTHYRONINE (T3) AND THYROXINE (T4) IN NORMAL AND COMPLICATED PREGNANCY

Amniotic fluid concentrations of 3,3',5'-tri-iodothyronine (rT3), 3,3'-Di-iodothyronine (3,3'-T2), 3,5,3'-tri-iodothyronine (T3) and T4 were studied in 384 women during normal and complicated pregnancy. An inverse correlation was observed between decreasing rT3 and increasing 3,3'-T2 concentrations in amniotic fluid with gestational age. The mean rT3 level in normal pregnancy was 2.81 nmol/1 at 12-20 weeks and decreased significantly to 1.06 nmol/1 at 36-42 weeks of gestation. The mean 3,3'-T2 concentration was 49.1 pmol/1 at12-20 weeks increasing to 119 pmol/1 at 36-42 weeks. The mean T4 value of 3.83 nmol/1 at 12-20 weeks was about half that of later periods. The T3 concentration in a random sample of 45 amniotic fluids ranged from less than 28 to 370 pmol/1 (mean 102 pmol/1). The mean rT3, 3,3'-T2 and T4 values measured in patients with intra-uterine malnutrition, gestation diabetes, tocolysis, placental insufficiency and rhesus incompatibility at 31-40 weeks of gestation were not significantly different from those in uncomplicated pregnancy. Significantly decreased rT3 and T4 concentrations were found in toxaemia. From the results obtained in complicated pregnancy it may be concluded that measurements of iodothyronines, especially rT3, in amniotic fluid have insignificant diagnostic value in the recognition of intra-uterine lesions with the probable exception of fetal hypothyroidism. The analysis of the dependence of iodothyronine concentrations on the gestational age showed a maximum of rT3 and T4 levels between 20 and 30 weeks of pregnancy. This marked rise of iodothyronine concentrations in amniotic fluid at mid-gestation may be due to the onsetting maturation of the hypothalamic-pituitary-thyroid control system of the fetus.     

Effect of varying gray-scale resolution for detectability of bone lesions in intraoral radiographs digitized for teletransmission

Abstract – Visual communicaltion equipments were developed early by radiologists for the transmission of analog signals, whereas today's transmission systems are based on digitization of the radiograph. For teletransmission of dental radiographs, it is essential to assess the diagnostic accuracy of various spatial and gray-scale resolutions. Each of 83 dry mandibles was divided into four regions. By random assignment it was decided for each region whether or not a hole should be drilled. Intraoral radiographs (3 × 4 cm) were performed of each region and interpreted. The radiographs were thereafter recorded by a video camera connected to an IBM-PC. The personal computer held a hardware digitization card defmed at a 512 × 512 spatial resolution with the possibility of selecting varying gray-scale resolutions. All radiographs were assessed in resolutions with 256 (8 bit), 128 (7 bit), 64 (6 bit), and 32 (5 bit) shades of gray. In no case was the original radiograph more accurate than the 512 × 512 × 8 resolution. In two of the regions evaluated, the images providing 32 shades of gray were less accurate (percentage of true positives and negatives) thao the other resolutions ( P <0.05) while in one region resolutions of 8 bit depth (256 shades of gray) provided a significantly greater accuracy than did the original radiograph and the other image resolutions ( P <0.05). This was due to fewer false negative scores and was not followed by an increase in false positive scores. It can be concluded thai a 512 × 512 spatial resolution is satisfactory for the detection of bone lesions in digitized intraoral radiographs and that 64 shades of gray provide an equally good diagnostic accuracy as do the original radiograph. This might be relevant when transmission times are of importance.