Biomedical subjects
R R Livingston
Publications and source records attributed to R R Livingston.
Effects of ketamine and fentanyl on lung metabolism in perfused rat lungs.
The effects of ketamine and fentanyl on serotonin (5-hydroxytryptamine; 5-HT) metabolism, angiotensin-converting enzyme (ACE), and protein synthesis (PS) were investigated in an isolated lung model. Rat lungs were perfused in situ with a blood-free physiological salt solution. The pulmonary vasculature was exposed to ketamine (0.005-2.1 mM) or fentanyl (1.8-4.5 microM) for up to 2 h. After 1 h, accumulation of 5-[14C]hydroxyindoleacetic acid (5-HIAA) by the lung was monitored as an index of 5-HT metabolism. ACE activity was estimated from hydrolysis of [3H]benzoylphenylalanyl-alanyl-proline, a synthetic substrate for the enzyme. [3H]phenylalanine was added to the perfusate after 1 h, and its incorporation into acid-precipitable lung protein was measured over the subsequent hour. Ketamine inhibited 5-HT uptake in a concentration-related manner. The inhibition was characterized as competitive and reversible. Fentanyl had no effect on lung 5-HIAA accumulation. Neither drug altered ACE activity or protein synthesis over the concentration ranges tested. The results indicate an action by ketamine that inhibits the 5-HT membrane-transport process. The different effects observed by ketamine and fentanyl on this process could contribute to the diverse pharmacological properties of these two drugs.
High-resolution CT scanning in the evaluation of cervical spine fractures: comparison with plain film examinations.
Forty-nine patients with cervical spine fractures were identified among 160 patients who underwent CT of the cervical spine for blunt trauma. Although there was a high index of suspicion on the plain film interpretation, as well as a large percentage of false positives, many fractures were found on CT that were not suggested, even in retrospect, on the plain radiographs. Of the 136 fractures ultimately identified in these patients, CT detected 135 (99%) while only 64 (47%) were seen or suspected on the initial screening radiographs. At first glance, this might appear to discredit the plain films as a screening device. However, most of these "occult" fractures occurred in vertebrae that had been identified as probably fractured in other parts, for example, pedicle fractures found in vertebrae initially suspected of harboring only a vertebral body fracture. Most of the remainder of the uncovered fractures were in vertebrae immediately adjacent to ones that were initially identified as fractured. Indeed, of the 49 patients with fractures, only one had an adequately exposed and positioned plain film that was completely normal. The ability of CT to determine quickly and confidently the presence or absence of cervical fractures and to define the position of fragments in relation to the spinal canal is of considerable value in the medical and nursing management of the seriously traumatized patient. For example, when a fracture is seen or suspected on conventional films, a limited CT examination of the area is recommended. Plain films should be used to guide the CT examination so that an intact vertebra above and below the lesion is included. If an adequately exposed and positioned plain film series of the cervical spine is normal, it is unlikely that CT will reveal a fracture. While conventional radiographs fail to detect a surprising number of fractures, they retain their value as a screening tool and as a guide to selective CT imaging.
A device for maintaining cervical spine stabilization and traction during CT scanning.
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