Digital radiography of subtle pulmonary abnormalities: an ROC study of the effect of pixel size on observer performance

Forty conventional radiographs with examples of mild interstitial infiltrates and subtle pneumothoraces and 40 normal studies of the chest were selected and digitized, with pixel sizes of 1.0, 0.5, 0.2, and 0.1 mm. Observer performance tests were carried out using receiver operating characteristic analysis. Conventional radiographs and digitized images were compared. The results indicate that, in such cases, diagnostic accuracy increases significantly as the pixel size is reduced, at least to the 0.1-mm level. We conclude that, for digital systems using screen-film or similar image receptors, use of a pixel size substantially larger than 0.1 mm may result in some loss of diagnostic accuracy.     

Regional extraction of circulating norepinephrine, DOPA, and dihydroxyphenylglycol in humans

Dihydroxyphenylglycol (DHPG) is the main intraneuronal metabolite of the sympathetic neurotransmitter, norepinephrine (NE), and dihydroxyphenylalanine (DOPA) the immediate product of the rate-limiting step in catecholamine biosynthesis. Simultaneous measurements of regional rates of appearance (spillovers) of NE, DOPA, and DHPG in plasma have the potential to provide unique information about aspects of sympathoneural function but have not actually been measured in humans. In the present study, spillovers of DHPG, DOPA, and NE in the heart, head, leg, and lungs, were estimated from regional extraction fractions of infused [3H]-1-NE, DHPG, and [13C6]DOPA or unlabelled DOPA in humans during cardiac catheterization. There was little cardiac extraction of DHPG (7 +/- SEM 2%) or DOPA (8 +/- 4%) but substantial extraction of NE (69 +/- 4%). Values for cardiac spillover of DHPG and DOPA therefore were similar to values for the arteriovenous increment times plasma flow (arteriovenous production rate), whereas the cardiac spillover of NE averaged about 7-times the NE arteriovenous production rate. Cardiac DHPG spillover (28 +/- 3 ng/min) exceeded the spillovers of NE (9 +/- 2 ng/min) and DOPA (15 +/- 4 ng/min). In contrast, cranial DOPA spillover (159 ng/min) exceeded those of NE and DHPG by 8- and 2-fold and accounted for about 1/10 of the total spillover of DOPA into arterial plasma. In the femoral vascular bed, arteriovenous production rates of NE and DHPG were unrelated to femoral spillovers of NE and DHPG. Arterial and regional clearances of [13C6]DOPA were similar to those of unlabelled DOPA. The results suggest that (1) endogenous NE, DOPA, and DHPG all are released into the bloodstream by the heart, head, and limbs of humans; (2) DHPG and DOPA are not co-released with NE; (3) cardiac arteriovenous production rates of DOPA and DHPG can be used to indicate cardiac spillover of these catechols, whereas the cardiac NE arteriovenous production rate substantially underestimates cardiac NE spillover; and (4) estimates of limb spillover of NE and DHPG require concurrent measurements of the corresponding regional clearances.     

Sympathoadrenal excitation and inhibition by lower brainstem stimulation in cats

Effects of stimulation of brainstem sites on hemodynamics and plasma catecholamine levels were assessed in cats under chloralose-urethane anesthesia. Pressor areas of the dorsal medulla (DM) and ventrolateral medulla (VLM) and the depressor area of the paramedian reticular nucleus (PRN) were stimulated electrically using a monopolar electrode, or chemically using sodium glutamate microinjection. Plasma levels of norepinephrine (NE) and epinephrine (EPI) were measured in caval blood above the adrenal veins. Electrical stimulation of the DM and VLM produced increases in blood pressure and in plasma NE and EPI levels that were enhanced after acute vagotomies. The NE and EPI responses were attenuated after acute, bilateral adrenalectomies, confirming augmented adrenomedullary secretion, whereas the pressor responses were intact. Injection of sodium glutamate into the same pressor regions of the DM or VLM also produced pressor responses and elevated plasma catecholamine levels, indicating that the responses resulted from activation of neuronal perikarya. Stimulation of the PRN attenuated pressor and catecholamine responses during stimulation of the DM and VLM. The results indicate that pressor responses during stimulation of the DM and VLM are due at least partly to activation of perikarya in these regions, are associated with but not dependent on adrenomedullary activation, and are enhanced after vagotomy; and that neurons of the PRN exert inhibitory modulation of the pressor and adrenomedullary responses during stimulation of VLM and DM.     

Acute normovolaemic haemodilution decreases postoperative allogeneic blood transfusion after total knee replacement

We hypothesized that the success of postoperative blood conservation after acute normovolaemic haemodilution (NVHD) is influenced by the extent of intraoperative bleeding and surgical trauma, and the timing of autologous blood transfusion. As total knee replacement is associated with minimal intraoperative but extensive postoperative blood loss, this procedure is ideally suited to acute NVHD. Therefore, to test our hypothesis, 30 patients undergoing elective total knee replacement were enrolled in a prospective, randomized, controlled study. In groups NVHD-2 and NVHD-6, before induction of anaesthesia patients were bled to a target packed cell volume (PCV) of 28-30%, and in the post-anaesthesia care unit autologous blood was transfused over a 2-h period terminating after operation at 2 and 6 h, respectively. In the control group, NVHD was not performed. After operation, platelets, fibrinogen, prothrombin and partial thromboplastin time, and liver function, urea and electrolytes were measured and compared with preoperative baseline values. Significantly (P < 0.024) more allogeneic blood was transfused in the control group (21 u.) compared with either group NVHD-2 (7 u.) or group NVHD-6 (5 u.). In the control group, despite the allogeneic blood transfusion, postoperative PCV decreased until day 4 after operation. Coagulation profile, liver function and urea and electrolytes concentrations were unaffected by the method of treatment. We conclude that for total knee replacement, acute NVHD is an effective blood conservation strategy. However, there was no difference in allogeneic blood administration between the two NVHD groups. Coagulation and liver function, and urea and electrolyte concentrations were unaffected by treatment.      

Liver transplantation for erythropoietic protoporphyria liver disease.

In erythropoietic protoporphyria (EPP), there is excessive production of protoporphyrin, primarily in the bone marrow, resulting in increased biliary excretion of this heme precursor. Some patients will develop progressive liver disease that may ultimately require liver transplantation. However, excessive production of protoporphyrin by the bone marrow continues after transplantation, which may cause recurrent disease in the allograft. This study was performed to define post-transplant survival, the risk of recurrent disease, and specific management issues in patients transplanted for EPP liver disease. The patients studied consisted of twelve males and eight females, with an average age of 31 (range, 13-56) years at the time of transplantation. The estimated maximum MELD score prior to transplant was 21 (range, 15-29). Unique complications in the perioperative period were light induced tissue damage in four patients and neuropathy in six, requiring prolonged mechanical ventilation in four. Patient and graft survival rates were 85% at 1 year, 69% at 5 years, and 47% at 10 years. Recurrent EPP liver disease occurred in 11 of 17 patients (65%) who survived more than 2 months. Three patients were retransplanted at 1.8, 12.6, and 14.5 years after the initial transplant for recurrent EPP liver disease. In conclusion, the 5-year patient survival rate in patients transplanted for EPP liver disease is good, but the recurrence of EPP liver disease appears to diminish long term graft and patient survival.     

Prevention of recurrent myocardial infarction and sudden death with aspirin therapy

In October 1985, the Food and Drug Administration approved a new indication of aspirin for the secondary prevention of recurrent myocardial infarction (MI) and death in patients with MI or unstable angina. Clinical trials have demonstrated the efficacy of this drug, especially when treatment is begun soon after the initial event. The antiplatelet actions of aspirin seem to be the most plausible explanation for its efficacy in reducing mortality and the rate of reinfarction. A single daily 325-mg tablet is effective and produces side-effect incidences of only zero to two percent above those produced by placebo. This article assesses the current state of knowledge regarding the value of aspirin therapy in survivors of acute MI and the implications for clinical practice.     

The Decade of the Brain: an era of promise for neurosurgery and a call to action

On July 25, 1989, President Bush signed a bill declaring the 1990's to be the Decade of the Brain. This offers the clinical and basic neuroscience communities an opportunity to join with the National Institute of Neurological Disorders and Stroke in moving ahead vigorously with research aimed at preventing and treating neurological disease. Neurosurgery must be an active participant in this national endeavor; its influence, skills, and contributions are needed.     

Financial risk, hospital cost, complications and comorbidities (CCc) in non-CC stratified urology diagnostic related groups

The federal Medicare Diagnosis Related Group payment mechanism is undergoing constant change. Significant interest has been generated at the health policy level regarding reimbursement for patients with complications and comorbidities. The purpose of this study was to analyze hospital resource consumption for patients in the seventeen urology non-complicating condition (CC) stratified Diagnostic Related Groups (DRGs), currently 45 percent of urology DRGs. We analyzed 185 Medicare patients in these non-CC stratified urology DRGs and found that patients with more CCs per patient had higher total hospital costs per patient, financial risk under DRGs, a greater percentage of outliers, and a higher mortality, than patients in these same DRGs with fewer CCs per patient. These findings suggest that the current DRG system is inequitable to some patients and certain hospitals vis-a-vis non-CC stratified urology DRGs. The Health Care Financing Administration has not significantly changed the complicating condition urology DRG classification, as of its recent May, 1988 legislation. Financial disincentives to treat these patients may affect both their access and quality of care in the future.