Multiphasic MR imaging: a new method for direct imaging of pulsatile CSF flow

A new technique is described that allows for the creation of pure pulsatile flow magnetic resonance (MR) images in a single acquisition. Five to 16 electrocardiographically gated images spanning the entire cardiac cycle are obtained with use of a gradient-echo pulse sequence. The section can be varied from 4 mm thick to full thickness projection. Taken singly, each image provides direct assessment of flow direction and velocity. Subtraction of image pairs eliminates signal detected from stationary protons, producing images of pulsatile flow. In this study the technique was used to image the flow of cerebrospinal fluid (CSF) in healthy subjects and in one patient with syringohydromyelia. The data suggest that multiphasic MR imaging provides a powerful means for the noninvasive assessment of CSF pulsatile flow dynamics and may have potential clinical application for the investigation of a variety of abnormalities such as normal pressure hydrocephalus, syrinx, and spinal block.     

Pressure-controlled inverse-ratio synchronised independent lung ventilation for a blast wound to the chest.

Massive unilateral pulmonary injury poses a severe ventilatory problem. We used pressure-controlled, inverse-ratio, independent lung ventilation for a shotgun injury. Two synchronised Siemens Servo 900C ventilators were connected to a double lumen endotracheal tube. Arterial pO2 tripled in 15 minutes, and the patient remained on SILV for 36 hours.     

Determination of fentanyl in whole blood at subnanogram concentrations by dual capillary column gas chromatography with nitrogen sensitive detectors and gas chromatography/mass spectrometry

Two methods for the determination of fentanyl at subnanogram concentrations in whole blood have been developed and evaluated. The initial screening was by gas chromatography with nitrogen sensitive detection (GC/NPD) in a splitless injection onto two fused-silica, 0.32-mm i.d. capillary columns (5% and 50% phenyl methyl silicone). Confirmation was by gas chromatography/mass spectrometry (GC/MS) using selected ion monitoring of a splitless injection onto a 0.1-mm i.d., 0.34-microns 5% phenyl methyl silicone capillary column. The methods were studied at fentanyl concentrations over the range 0.05 to 5.0 ng/mL using 2 mL of blood. The detection limits were set at 0.10 ng/mL for GC/NPD and 0.05 ng/mL for GC/MS. The overall recovery of fentanyl was found to be greater than 75% over the range of 0.25 to 2.5 ng/mL. The within-run precision determined at fentanyl concentrations of 0.25 and 1.0 ng/mL showed coefficients of variation ranging from 8.7 to 14.8%. The between-run precision determined at concentrations of 0.4 and 0.8 ng/mL showed coefficients of variation ranging from 3.3 to 11.6%. The blood calibration curves in the range of 0.25 to 2.5 ng/mL monitored over a 3-month period showed a mean correlation coefficient of 0.99 for both the GC/NPD and GC/MS methods.     

Common duct exploration or endoscopic sphincterotomy for choledocholithiasis?

The relative indications for operative common duct exploration (CDE) and endoscopic sphincterotomy (ES) in treating common duct stones are often unclear. This prospective study compared CDE and ES in treating choledocholithiasis after excluding patients with acute cholecystitis, idiopathic pancreatitis, sphincter of Oddi dysfunction and malignant disease. One hundred and two patients had 105 CDE and a further 50 patients had 57 ES. Of the patients having CDE, 76 also had cholecystectomy for gall-bladder (GB) disease while 26 had prior cholecystectomy. With ES, in 16 the GB was present and not removed while 34 patients had had prior cholecystectomy. Hospitalization was significantly less following ES. There was one peri-operative death after CDE and none after ES. There were two late biliary-related deaths, 3 and 27 months after ES, in patients who developed acute cholecystitis. In post-cholecystectomy patients having ES, complications were fewer and less severe after ES (15%) than CDE (41%). In patients with an intact GB, peri-operative complications occurred in 30% after cholecystectomy and CDE. Following ES alone, complications occurred in 33% with the majority of these complications arising from the diseased GB. It is concluded that the optimal treatment for post-cholecystectomy patients with bile-duct stones is ES. In elderly patients with an intact GB, the bile-duct stones can be treated by ES; whether subsequent cholecystectomy is necessary should be assessed on the likelihood of future GB complications.     

Effects of diltiazem on lactate, ATP, and cytosolic free calcium levels in ischemic hearts.

Changes in tissue lactate, ATP, and cytosolic free calcium (Cai) were examined in isolated, perfused rat hearts receiving 20 min of zero-flow global ischemia (37 degrees C). Addition of diltiazem before ischemia caused a concentration-dependent decrease in lactate accumulation. This effect was not mediated by modulation of norepinephrine release since depletion of catecholamines by reserpine did not alter lactate accumulation, and diltiazem treatment reduced lactate accumulation in catecholamine-depleted hearts. Diltiazem-treated hearts showed a concentration-dependent decrease in tissue ATP utilization that was associated with the decrease in tissue lactate during ischemia. Basal time averaged Cai, determined by fluorine NMR using 5FBAPTA, was 620 nM. Diltiazem (0.9 microM) decreased this value to 489 nM and reduced heart rate and maximum pressure developed (81.3 and 53.9% of control, respectively) before ischemia. Cai increased fourfold between 9 and 15 min of ischemia in hearts receiving no drug, while there was no increase in Cai in diltiazem-treated hearts. These results show that diltiazem reduces the use of ATP and therefore production of lactate during ischemia, and indicate a relationship between preservation of ATP and maintenance of Cai that may be important in the beneficial effects of diltiazem during myocardial ischemia.