Validation in the sheep of an ultrasound velocity dilution technique for haemodialysis graft flow

BACKGROUND: A simple, rapid, inexpensive method for measuring the flow in a patient's vascular access would permit routine monitoring during haemodialysis, and hence provide information of access graft deterioration sufficiently early to increase the success of minimally invasive remedial procedures. This paper reports the validation of such a method in animals. METHODS: A PTFE graft was implanted in sheep between the carotid artery and the jugular vein. While the sheep was under general anaesthesia and on an haemodialysis circuit, ultrasound velocity in its blood was perturbed by the injection of a 5-10 ml bolus of isotonic NaCl. The pump tubing flow was measured by a transit-time blood flow meter. This flow was combined with the areas of perturbation generated by the injection before and after mixing in the access flow to estimate graft flow. The calculated graft flow was compared to flow measured directly by a transit-time probe on the same carotid artery. RESULTS: Over a 10-fold range, 120-1260 ml/min, graft flow measured by ultrasound velocity dilution agreed well with graft flow measured directly with a scatter of 76 ml/min about the regression line. CONCLUSION: Ultrasound velocity dilution provides a method for measuring flow in the graft accurate enough for clinical evaluation of patients on dialysis.      

Correlates of suicide in building industry workers.

Suicide within the construction industry in Queensland, Australia was reportedly high in a recent Royal Commission report. The current study examined the incidence and causes of suicide in this industry using psychological autopsy and focus group investigations. A total of 64 male suicides occurred over the seven-year period, representing a crude suicide rate of 40.3 per 100,000, significantly greater than the working age Australian male rate. Young employees were at excessive risk with separation/divorce, relationship problems, and untreated psychiatric conditions the major contributors. Focus groups emphasized the importance of work/home interface factors and industry-specific factors preceding suicide.     

The influence of rural physicians' perception on referral patterns to a university hospital.

The patient referral process is based on a complex set of social rewards and costs for the referring physician. For the physician or institution potentially receiving referrals, a key question is, why is one institution selected over other available choices? Factor analysis of a survey of rural physicians revealed five factors of reward and cost associated with the choice of where to refer patients. Further analysis of these factors suggested that the ability to have patients admitted and treated when necessary is central to the satisfaction of the referring physician and their willingness to continue the consultant relationship. Adequate information about the consultants was also important to satisfaction. Other factors have less influence. Further, “admissions when necessary” was the only reward/cost factor which predicted physicians who referred more to the university hospital than to other hospitals. If a university hospital wants to develop strategies to encourage referrals from rural physicians, it must be cognizant of these social reward-cost factors.     

Systemic Absorption and Block after Epidural Injection of Ropivacaine in Healthy Volunteers

Background: For local anesthetics, the process of removal from the site of administration influences the duration of anesthesia and the risk for systemic toxicity to develop. The systemic absorption of epidural ropivacaine and the time profile of sensory and motor block were studied in healthy volunteers.

Methods: Nine persons simultaneously received 150 mg ropivacaine hydrochloride (7.5 mg/ml) epidurally and 40 mg deuterium-labeled (sup 2 H sub 3)ropivacaine hydrochloride (0.25 mg/ml) intravenously. Peripheral arterial and venous plasma samples were collected, and assessments of sensory and motor block were made.

Results: The arterial plasma concentrations increased faster than the venous concentrations, with 50% higher maximum concentrations after both intravenous and epidural administration. The absorption was biphasic. A correlation was seen between the duration of sensory block and the slower absorption half-life; that is, the longer the half-life, the longer the duration. The extent of spread varied among the volunteers, with the median upper block level not exceeding T12. The motor block (Bromage score 1) was of slower onset (median, 0.4 h) and of shorter duration (median, 4.1 h) than the sensory block (onset, 0.2 h; duration, 6.5 h at L2 medians).     

EXAMINATION OF DEVELOPMENTAL NEUROTOXICITY BY THE USE OF TISSUE CULTURE MODEL SYSTEMS

1. The rotation-mediated three-dimensional reaggregate culture system is uniquely suited for studies on developmental neurotoxicity. In this system, it is possible to reconstruct central neuronal pathways and follow their development. 2. Exposure to drugs of abuse including methamphetamine and methylenedioxyamphetamine or the appetite suppressant, fenfluramine, reduces monoamines in the cultures in a dose-dependent manner and interrupts normal monoaminergic development. 3. While the monoaminergic neurones may attain normal rates of development following drug removal, the affected neurones are not capable of overcoming the drug-induced insults and a deficiency in monoamines persists throughout development. 4. In addition, the production of immortalized monoclonal hybrid cells obtained by fusion of fetal mesencephalic neurones with a neuroblastoma has yielded cell lines expressing a dopaminergic phenotype. 5. Such cells have been useful in establishing the relationship of neurotoxicity to cell lineage and can serve as models for the study of the cellular and molecular mechanisms of neurotoxicity.     

Distribution of retroperitoneal metastases after chemotherapy in patients with nonseminomatous germ cell tumors.

For patients with advanced nonseminomatous germ cell tumors a retroperitoneal lymph node dissection is routinely performed following chemotherapy if the serum tumor markers have returned to normal. Bilateral retroperitoneal lymph node dissection has been recommended because metastatic deposits may be widespread. The aim of this study was to describe the distribution of retroperitoneal metastases following chemotherapy in patients with nonseminomatous germ cell tumor and determine if the extent of the retroperitoneal lymph node dissection can be modified. We studied 113 patients who had initially bulky retroperitoneal disease and underwent retroperitoneal lymph node dissection following chemotherapy. For the purposes of this study teratoma and malignant germ cell tumor are referred to as tumor. The most common location of tumor was the para-aortic area (91%) in patients with a left primary tumor and the interaortocaval area (78%) in those with a right tumor. Tumor was located outside the boundaries of a modified retroperitoneal lymph node dissection in 14 of the 60 patients with residual disease but the tumor was present within a palpable mass in 6 of these 14 patients. If the residual mass was removed and a modified retroperitoneal lymph node dissection was performed only 9 of the 113 patients (8%) would have tumor left in the retroperitoneum. For a select group of patients with advanced nonseminomatous germ cell tumor treated with chemotherapy, resection of the residual mass combined with modified retroperitoneal lymph node dissection is appropriate.     

Ossification of the posterior longitudinal ligament: a report of nine cases in non-Oriental patients

Ossification of the posterior longitudinal ligament (OPLL) is a progressive disorder of the spine which may result in spinal cord compression and myelopathy. While prevalent among Japanese, its occurrence in non-Orientals has been infrequently reported. Nine patients with OPLL have been diagnosed and followed at the Emory Clinic Spine Center over a 5-year period. All of the patients had been misdiagnosed before presentation. Five of the nine had undergone a total of eight ineffective operations. Failure to distinguish OPLL from other more common causes of myelopathy can result in delayed or inappropriate treatment. Illustrative cases and radiographic studies are presented.     

Comparison of risk stratification with pharmacologic and exercise stress myocardial perfusion imaging: A meta-analysis

BACKGROUND: Although pharmacologic stress myocardial perfusion imaging (MPI) and exercise stress MPI have comparable diagnostic accuracy, their comparative value for risk stratification of patients with known or suspected coronary disease is not known. METHODS AND RESULTS: The data of 14,918 patients were combined from 24 studies evaluating prognosis in patients undergoing either pharmacologic stress or exercise stress MPI. Studies were included if a 2 x 2 table for hard cardiac events (cardiac death and myocardial infarction [MI]) could be constructed from the data available. Excluded were studies performed for post-MI, post-revascularization, or preoperative risk stratification. A weighted t test was used to compare the cardiac events, and a random effects model was used to calculate summary odds ratios. Summary odds ratios for hard cardiac events were similar for pharmacologic stress and exercise stress MPI. Summary receiver operating characteristic curves also showed no difference in discriminatory power between the stressors. The cardiac event rates were significantly higher with normal and abnormal test results with pharmacologic stress MPI than with exercise stress MPI (1.78% vs 0.65% [P < .001] for normal results and 9.98% vs 4.3% [P < .001] for abnormal results). Subgroup analysis revealed that both cardiac death and nonfatal MI were significantly higher with pharmacologic stress MPI. Patients undergoing pharmacologic stress MPI had a significantly higher prevalence of poor prognostic factors, and meta-regression revealed that exercise capacity was the single most important predictor of cardiac events. CONCLUSIONS: This meta-analysis shows that exercise stress MPI and pharmacologic stress MPI are comparable in their ability to risk-stratify patients. However, patients undergoing pharmacologic stress studies are at a higher risk for subsequent cardiac events. This is true even for those with normal perfusion imaging results.