A leak quantification method using sulfur hexafluoride as tracer gas

Filter holders and continuous air monitors are used extensively in the nuclear industry. It is important to minimize leakage in these devices, and, in recognition of this consideration, a limit on leakage for sampling systems is specified in; however, the protocol given in the standard is really germane to measurement of significant leakage, e.g., several percent of the sampling flow rate. In the present study, we developed a technique for quantifying leakage and used that approach to measure the sealing integrity of a continuous air monitor and two kinds of filter holders. The methodology involves use of sulfur hexafluoride as a tracer gas with the device being tested operated under dynamic flow conditions. The leak rates in these devices were determined in the pressure range from 2.49 kPa (10 inches H2O) vacuum to 2.49 kPa (10 inches H2O) pressure at a flow rate of 56.6 L min-1 (2 cfm). For the two filter holders, the leak rates were less than 0.007% of the nominal flow rate. The leak rate in the continuous air monitors was less than 0.2% of the nominal flow rate. These values are well within the limit prescribed in the ANSI standard, which is 5% of the nominal flow rate. We suggest that the limit listed in the ANSI standard should be reconsidered as lower values can be achieved, and the methodology presented herein can be used to quantify lower leakage values in sample collectors and analyzers.     

In vitro,pharmacokinetic, and pharmacodynamic interactions of ketoconazole and midazolam in the rat

Interactions of midazolam and ketoconazole were studied in vivo and in vitro in rats. Ketoconazole (total dose of 15 mg/kg intraperitoneally) reduced clearance of intravenous midazolam (5 mg/kg) from 79 to 55 ml/min/kg (p < 0.05) and clearance of intragastric midazolam (15 mg/kg) from 1051 to 237 ml/min/kg (p < 0.05), increasing absolute bioavailability from 0.11 to 0.36 (p < 0.05). Presystemic extraction occurred mainly across the liver as opposed to the gastrointestinal tract mucosa. Midazolam increased electroencephalographic (EEG) amplitude in the beta-frequency range. Ketoconazole shifted the concentration-EEG effect relationship rightward (increase in EC(50)), probably because ketoconazole is a neutral benzodiazepine receptor ligand. Ketoconazole competitively inhibited midazolam hydroxylation by rat liver and intestinal microsomes in vitro, with nanomolar K(i) values. At a total serum ketoconazole of 2 microg/ml (3.76 microM) in vivo, the predicted reduction in clearance of intragastric midazolam by ketoconazole (to 6% of control) was slightly greater than the observed reduction in vivo (to 15% of control). However, unbound serum ketoconazole greatly underpredicted the observed clearance reduction. Although the in vitro and in vivo characteristics of midazolam in rats incompletely parallel those in humans, the experimental model can be used to assess aspects of drug interactions having potential clinical importance.     

Recurrent Carpal Tunnel Syndrome––Analysis of the Impact of Patient Personality in Altering Functional Outcome Following a Vascularised Hypothenar Fat Pad Flap Surgery

We retrospectively analysed 25 patients (27 hands) who had both clinical and electrophysiological confirmation of true recurrent carpal tunnel syndrome from January 2004 to December 2009. In all the patients, after releasing the nerve a vascularised fat pad flap was mobilised from the hypothenar region and sutured to the lateral cut end of flexor retinaculum. The patient characteristics, co-morbidities, duration of symptom, interval between first release and revision surgery and intra-operative findings were assessed against post-operative relief of pain, recovery of sensory and motor dysfunction. The average age of the patients was 58?years (43?C81) and the dominant hand was involved in 22 patients. Intra-operatively the nerve was compressed by scar tissue connecting the previously divided ends of the retinaculum in 18 and nine had scar tissue and fibrosis around the nerve. Following surgery 16 patients had complete recovery (asymptomatic at the first follow-up), eight had delayed recovery (partial recovery of symptoms at final follow-up) and three had a poorer outcome (persistence of preoperative symptoms at the final follow-up). The patients with delayed recovery/poorer outcome had a) Early recurrence; b) Diabetes mellitus; c) Obesity; d) Cervical spine problems; e) Involvement of non-dominant hand; and f) Intraoperative scar tissue and fibrosis. The hypothenar fat pad transposition flap provides a reliable source of vascularised local tissue that can be used in patients with recurrent carpal tunnel syndrome. The factors that were associated with poorer/delayed recovery were involvement of non-dominant hand, recurrence within a year from the previous surgery, intra-operatively scar tissue in the carpal tunnel and associated co-morbidities, like obesity diabetes mellitus and cervical spine problems.     

Functional outcome of an early anterior cruciate ligament reconstruction in comparison to delayed: Are we waiting in vain?

Background

Surgical techniques of ACL reconstruction (ACLR) have evolved over the past three decades along with debate regarding timing of reconstruction. It was a widespread belief that the timing of surgery was an important factor in determining the resulting stiffness after ACLR. Delayed rather than early reconstruction of the ACL is the current recommended treatment since it is thought to give a better functional outcome. However, there is no consensus in the literature regarding the optimal time of surgical intervention. The purpose of this study was to compare the range of motion and functional outcome in patients who underwent ACLR early with those that were delayed.