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J O Johnson

Publications and source records attributed to J O Johnson.

27 records · Page 2Linked to original sources
PubMed1994

An effectiveness study of a new piezoelectric sensor for train-of-four measurement.

We have developed an easy-to-use, noninvasive piezoelectric sensor for quantitative monitoring of neuromuscular block. In a clinical evaluation with 23 patients, the piezo sensor was objectively compared to a mechanomyogram (MMG) for its ability to measure train-of-four (TOF) ratio from the adductor pollicis. After administration of succinylcholine (120-200 mg intravenously [i.v.]) to facilitate intubation, neuromuscular block was maintained with vecuronium by either boluses (1-2 mg i.v.) or an infusion (0.4-1.0 micrograms.kg-1.min-1 i.v.). Paired measurements were made of the TOF ratio from both sensors over a complete range of block levels (8%-100%). The difference in the TOF ratio measurement between the sensors showed a bias of 0.018. The SD of the difference between the sensors was +/- 0.129. The limits of agreement, which define the range in which 95% of the differences between the sensor measurements lie, were from -0.24 to 0.275. The sensitivity of the piezo sensor for detecting recovery based on a TOF ratio greater than 0.70 was shown to be 0.74 with specificity of 0.91. Under the conditions tested, the piezo sensor was not as accurate as the MMG. However, it was able to predict recovery of neuromuscular block with better accuracy than shown previously by manual evaluation of the TOF ratio, making it a reasonable, convenient alternative for quantitative monitoring of recovery from neuromuscular block.

Humans↗
PubMed1993

Endotracheal tube cuff pressure increases significantly during anterior cervical fusion with the Caspar instrumentation system.

To determine whether endotracheal tube cuff pressure increases significantly with surgical retraction and cervical spine distraction during anterior cervical spine surgery with Caspar instrumentation, we prospectively studied 10 patients undergoing this procedure. The tracheas of all patients were intubated with a Mallinckrodt Hi-Lo endotracheal tube. Tracheal tube cuff pressures measured with a transducer system were 42.4 mm Hg +/- 7.0 mm Hg (SEM) after intubation and cuff inflation. Air was removed from the endotracheal tube cuff until the trachea was just barely sealed at a cuff pressure of 15.2 mm Hg +/- 1.6 mm Hg. The endotracheal tube cuff pressure was readjusted to "just-seal" pressure before the surgeons introduced the Caspar instrumentation. The cuff pressure with traction and distraction was 43.2 mm Hg +/- 5.0 mm Hg. This pressure was significantly increased from the "just-seal" pressure, and from the cuff pressure after instrumentation was discontinued (9.8 mm Hg +/- 2.3 mm Hg). We conclude that anterior cervical spine surgery with Caspar instrumentation is associated with a significant increase in endotracheal tube cuff pressure.

Cervical Vertebrae↗
PubMed1990

Monoamine receptors in an animal model of affective disorder.

After a relatively mild course of uncontrollable shocks, two distinct groups of rats can be defined in terms of their performance in learning to escape from a controllable stressor. Response-deficient (RD) rats do not learn to terminate the controllable stressor, whereas nondeficient (ND) rats learn this response as readily as do untreated control rats. The current studies were designed to determine the neurochemical correlates of the behavioral differences between these groups of rats. The major findings concerned postsynaptic beta-adrenergic effects in the hippocampus of RD rats. These included an up-regulation of beta-adrenergic receptors and, in parallel experiments, an increase in the sensitivity of adenylyl cyclase to stimulation by norepinephrine. There was no difference in brain levels of catecholamines between the three groups of rats. A statistically significant increase in levels of 5-hydroxytryptamine was noted in the hippocampus and hypothalamus of RD rats as compared to levels in ND rats, but no significant differences were measured between groups of rats in terms of S1 or S2 serotonergic receptor binding. These results implicate both beta-adrenergic and serotonergic mechanisms in the behavioral deficit caused by uncontrollable shock.

Adenylyl Cyclases↗
PubMed1990

Differentiation of seminomatous from nonseminomatous testicular tumors with MR imaging.

Distinguishing seminomatous from nonseminomatous testicular neoplasms preoperatively is useful because treatment of these two tumors types is different. We evaluated whether the distinction could be made with MR imaging in six patients with seminomatous and nine patients with nonseminomatous testicular tumors (including teratoma, teratocarcinoma, embryonal cell, and choriocarcinoma). The MR diagnoses, which were obtained from the formal reports of the MR studies done and interpreted before orchiectomy, were compared with the pathologic diagnosis. The distinction between the two tumor types on MR images was based on the signal intensity and heterogeneity of the lesion. We also retrospectively compared the MR findings with tissue histology. MR scans in nonseminomatous tumors showed a marked heterogeneous mix of signals, with some regions less intense and others more intense than normal testicular tissue on both proton-density and T2-weighted images. The typical background signal was nearly equal to normal testicular tissue. The tumors also had a dark band at their periphery that correlated with a fibrous tumor capsule on histologic examination. In contradistinction, seminomatous tumors were isointense with testis on proton-density images and consistently hypointense and relatively homogeneous on T2-weighted images. These tumors typically lacked a capsule on MR images. One lesion, only 3 mm in diameter, could not be characterized on MR images because of limitations in spatial and contrast resolution. In 13 of the 14 lesions that could be characterized, the histologic type was predicted correctly on the basis of the MR appearance. The one error occurred in a patient with pure seminoma. Although the MR appearance of the lesion was otherwise similar to the other seminomas, the lesion had a single focus of bright signal that was due to hemorrhage. This focus was interpreted incorrectly as a nonseminomatous element. Our findings in this small series of patients suggest that MR imaging can be used to distinguish seminomatous from nonseminomatous testicular tumors.

Adult↗
PubMedDate not supplied

Biliary ductal shave biopsy with use of the Simpson atherectomy catheter.

PURPOSE: The authors performed percutaneous biliary ductal shave biopsy through an existing transhepatic biliary drainage tract with use of the Simpson atherectomy catheter. The technical feasibility, sensitivity, and complications of this endoluminal biopsy method were studied when used for diagnosis of biliary ductal and pancreatic neoplasm. PATIENTS AND METHODS: Nineteen bile duct shave biopsies were performed in 18 patients with symptomatic biliary obstruction by using a 9-F Simpson directional atherectomy catheter. Seven of the 18 patients underwent nine negative percutaneous needle biopsies prior to undergoing percutaneous biliary drainage. Results of previous transcatheter brush biopsies performed through the transhepatic tract were negative in all patients. RESULTS: A histologic diagnosis was obtained in 15 of the 19 procedures (sensitivity, 0.79) and included cholangiocarcinoma (n = 7), pancreatic carcinoma (n = 5), metastatic carcinoma (n = 2), and primary sclerosing cholangitis (n = 1). Two complications occurred in the 19 procedures (10.5%), both transient but significant hemorrhage, one of which necessitated transfusion. CONCLUSIONS: Percutaneous biliary ductal shave biopsy with the Simpson atherectomy catheter can be performed successfully through the transhepatic approach and is a sensitive endoluminal biopsy technique, particularly in patients with tumors of the biliary tree that are not diagnosed by means of percutaneous needle biopsy or endoscopic methods. Disadvantages of this method include the high cost of the device and risk of hemorrhage. Atherectomy shave biopsy should be used cautiously and only after more conventional biopsy methods have been employed.

Atherectomy↗
PubMedDate not supplied

Advances in magnetic resonance imaging of the pelvis at 0.15 tesla.

The recent development of improved commercial radiofrequency coils and multiecho, multislice software for low field strength magnetic resonance systems has markedly increased the clinical utility of magnetic resonance imaging (MRI) of the pelvis at low field strengths. An evaluation of 70 patients with a variety of pelvic lesions and 14 normal volunteers who were studied using 0.15 T resistive magnet scanner revealed that anatomic structures and a variety of mass lesions could be clearly depicted in transaxial, sagittal and coronal planes using this updated system. Accurate characterization of lesions was possible in many instances using T2 weighted multiecho scans with echo time (TE) ranging from 30 ms to 120 ms (45 ms-180 ms using a reduced bandwidth technique). T1 weighted multislice scans demonstrated anatomic structures to best advantage and calculation of T1 and T2 relaxation times frequently facilitated more accurate differential diagnosis, particularly in the case of ovarian lesions.

Bone Neoplasms↗