Comparison of pleural fluid pH values obtained using blood gas machine, pH meter, and pH indicator strip.

STUDY PURPOSE: The purpose of this study was to compare the pleural fluid pH values obtained with a blood gas machine (pHbg), with a pH meter (pHmet), and with a pH indicator strip (pHstrip), to determine if the pleural fluid pH measured by a pH meter or a pH indicator strip was sufficiently accurate for clinical decisions. METHODS: The pleural fluid pH was determined, within 20 min after being collected anaerobically, by a blood gas machine (CIBA-Corning model 288), pH meter (Corning pH meter 610A), and pH indicator strip (Baxter Diagnostic) following routine laboratory procedures in 50 pleural fluids. Pleural fluid pH was determined in seven additional samples with the blood gas machine and a pH meter at 25 and 37 degrees C respectively, initially, and after 30 min. RESULTS: The mean pHbg (7.42+/-0.01) was significantly less than the mean pHmet (7.58+/-0.02) or the mean pHstrip (8.23+/-0.06). There were significant differences between the pHbg and the pHmet (p < 0.001), and between the pHbg and the pHstrip (p < 0.001). Analysis of the additional seven samples demonstrated that when the blood gas machine was set at 25 degrees C, the pHbg (pHbg = 7.54+/-0.02) and the pHmet (7.53+/-0.01) were almost identical. CONCLUSION: When the pleural fluid pH is going to be used for decision making, only the pH values provided by the blood gas machine are sufficiently accurate.

Nuclear magnetic resonance imaging of the spine.

Forty subjects were examined to determine the accuracy and clinical usefulness of nuclear magnetic resonance (NMR) examination of the spine. The NMR images were compared with plain radiographs, high-resolution computed tomograms, and myelograms. The study included 15 patients with normal spinal cord anatomy and 25 patients whose pathological conditions included canal stenosis, herniated discs, metastatic tumors, primary cord tumor, trauma, Chiari malformations, syringomyelia, and developmental disorders. Saturation recovery images were best in differentiating between soft tissue and cerebrospinal fluid. NMR was excellent for the evaluation of the foramen magnum region and is presently the modality of choice for the diagnosis of syringomyelia and Chiari malformation. NMR was accurate in diagnosing spinal cord trauma and spinal canal block. The normal disc was seen, but with rare exceptions bulging of the annulus and herniation of the nucleus pulposus were not visualized.

Intravenous digital subtraction angiography of the intracranial veins and dural sinuses.

When combined with computed tomography, IV DSA is usually of sufficient quality to replace conventional angiography in most patients with abnormalities of the larger intracranial veins and sinuses. Preoperatively, IV DSA can be used to evaluate normal anatomic variations of venous outflow to determine what sinuses can be safely occluded if necessary in the region of the temporal bone, jugular fossa, and base of the skull. Patients with glomus jugular tumors and carotid-cavernous fistulas also need conventional angiograms to define the feeding vessels of these lesions for obliteration by embolization or surgery.