Cerebral blood flow relationships associated with a difficult tone recognition task in trained normal volunteers

Tone recognition is partially subserved by neural activity in the right frontal and primary auditory cortices. First we determined the brain areas associated with tone perception and recognition. This study then examined how regional cerebral blood flow (rCBF) in these and other brain regions correlates with the behavioral characteristics of a difficult tone recognition task. rCBF changes were assessed using H2(15)O positron emission tomography. Subtraction procedures were used to localize significant change regions and correlational analyses were applied to determine how response times (RT) predicted rCBF patterns. Twelve trained normal volunteers were studied in three conditions: REST, sensory motor control (SMC) and decision (DEC). The SMC-REST contrast revealed bilateral activation of primary auditory cortices, cerebellum and bilateral inferior frontal gyri. DEC-SMC produced significant clusters in the right middle and inferior frontal gyri, insula and claustrum; the anterior cingulate gyrus and supplementary motor area; the left insula/claustrum; and the left cerebellum. Correlational analyses, RT versus rCBF from DEC scans, showed a positive correlation in right inferior and middle frontal cortex; rCBF in bilateral auditory cortices and cerebellum exhibited significant negative correlations with RT These changes suggest that neural activity in the right frontal, superior temporal and cerebellar regions shifts back and forth in magnitude depending on whether tone recognition RT is relatively fast or slow, during a difficult, accurate assessment.      

Determinants of vancomycin clearance by continuous venovenous hemofiltration and continuous venovenous hemodialysis

The clearance of vancomycin is significantly reduced in patients with acute, as well as, chronic renal failure. Although multiple-dosage regimen adjustment techniques have been proposed for these patients, there is little quantitative data to guide the individualization of vancomycin therapy in acute renal failure patients who are receiving continuous renal replacement therapy (CRRT). To determine appropriate vancomycin dosing strategies for patients receiving continuous venovenous hemofiltration (CVVH) and continuous venovenous hemodialysis (CVVHD), we performed controlled clearance studies in five stable hemodialysis patients with three hemofilters: an acrylonitrile copolymer 0.6 m2 (AN69), polymethylmethacrylate 2.1 m2 (PMMA), and polysulfone 0.65 m2 (PS). Patients received 500 mg of vancomycin intravenously at least 12 hours before the start of the clearance study. The concentration of vancomycin in multiple plasma and dialysate/ultrafiltrate samples was determined by EMIT (Syva, Palo Alto, CA). The diffusional clearance and sieving coefficient (SC) of vancomycin were compared by a mixed-model repeated-measures analysis of variance (ANOVA) with filter and blood (Q(B)), dialysate inflow (Q(DI)), or ultrafiltration rate (Q(UF)) as the main effects and patient as a random effect. Vancomycin was moderately protein bound in these patients; free fraction ranged from 49% to 83%. The SCs of the three filters were similar and significantly correlated with the free fraction of vancomycin (P = 0.01; r2 = 0.465). Significant linear relationships were observed between the diffusional clearance of vancomycin and Q(DI) for all three filters: AN69 (slope = 0.482; r2 = 0.880); PMMA (slope = 0.853; r2 = 0.966); and PS (slope = 0.658; r2 = 0.887). The slope of this relationship for the PMMA filter was significantly greater than that of the AN69 and PS filters. The clearance of vancomycin, urea, and creatinine, however, was essentially constant at all Q(B)s for all three filters. Thus, the clearance of vancomycin was not membrane dependent during CVVH. However, during CVVHD, membrane dependence of vancomycin clearance was noted at a Q(DI) greater than 16.7 mL/min; vancomycin clearance with PMMA at a Q(DI) of 25 mL/min was 66% and 43% greater than that with the AN69 and PS filters, respectively. CVVH (62% to 262%) and CVVHD (90% to 540%) can significantly augment the clearance of vancomycin in acute renal failure patients. Dosing strategies for individualization of vancomycin therapy in patients receiving CVVH and CVVHD are proposed.     

Acute posttraumatic renal failure: a multicenter perspective.

Acute renal failure (ARF) following trauma is rare. Historically, ARF has been associated with a high mortality rate. To investigate this entity we conducted a retrospective review of 72,757 admissions treated at nine regional trauma centers over a 5-year period. Seventy-eight patients (0.098%) developed acute renal failure requiring hemodialysis. Detailed demographic, clinical, and outcome data were collected. Patients with pre-existing medical conditions (group I) had a 70% increase in mortality over those without pre-existing conditions (p less than 0.004). Twenty-four patients (31%) developed ARF less than 6 days after injury (group II). The remainder (group III) developed late renal failure (mean time to first dialysis, 23 days). The predominant cause of death was multiple organ failure (82%). There were no differences in mortality because of multiple organ failure among the three groups of patients. Of the 33 survivors, six (18%) were discharged with renal insufficiency, three (9%) were discharged on dialysis, 23 (70%) were discharged home or to rehabilitation, and 27 (82%) had no significant evidence of renal insufficiency. Conclusion: Posttraumatic renal failure requiring hemodialysis is rare (incidence, 107 per 100,000 trauma center admissions), but the mortality rate remains high (57%). Two thirds of the cases of posttraumatic renal failure develop late and are secondary to multiple organ failure; one third of the cases of posttraumatic renal failure develop early and may result from inadequate resuscitation.     

Effect of desglycinamide(9)-lysine(8)-vasopressin and prolyl-leucyl-glycinamide on oral ethanol intake in the rat.

Rats given ethanol in their drinking water at a concentration that permitted adequate fluid intake gradually accepted higher concentrations and consumed larger amounts of ethanol. These increases were augmented when daily subcutaneous injections of 1 microgram of desglycinamide9-lysine8-vasopressin (DGLVP) or 10 microgram of prolyl-leucyl-glycinamide (PLG) were given concomitantly. Nonsignificant changes in ethanol consumption were seen with injections of 1 microgram PLG, or 0.42 or 42 microgram of lysine8-vasopressin (LVP). In a second experiment 4 microgram DGLVP given every second day as a long-acting zinc phosphate complex, commencing after the increases in ethanol intake had taken place, failed to produce any change in ethanol consumption subsequently. In both Experiments 1 and 2, the rats were switched from forced ethanol intake to a choice between ethanol and tap water. On these tests there was only marginal evidence of peptide-produced changes in ethanol intake.     

Severe hepatic trauma: a multi-center experience with 1,335 liver injuries

The experience of six regional trauma centers with severe hepatic trauma was reviewed to identify trends in management, mortality, and postoperative complications. During the 5-year period ending June 1987, 210 complex liver injuries were identified at laparotomy. There were 92 Class III, 59 Class IV, and 59 Class V injuries. Mechanism of injury was blunt in 101 (48%) patients and penetrating in 109 (52%). Shock was observed in 38%, 46%, and 85% of Class III, IV, and V patients, respectively. Emergency department thoracotomy was performed in 31 patients. There was only one (3%) survivor. Resuscitative operating room thoracotomy was performed in 34 patients with three (9%) survivors. Class III injuries were most frequently treated with hepatotomy and individual vessel ligation (41%) and deep liver suturing (25%). Class IV injuries were most often managed by resectional debridement (36%). Class V injuries required caval shunt placement in 38 (64%) patients. There were only four (10%) survivors after caval shunt placement. There were 20 (59%) survivors of 34 patients treated with packing placed as an adjunct after hepatic injury repair. There was no significant increase in the incidence of abscess formation after perihepatic packing. Routine peritoneal drainage was used in 94% of patients. Overall mortality rates for Class III, IV, and V injuries were 25%, 46%, and 80%, respectively (p less than 0.01). Death rates due to the liver injury in Class III, IV, and V patients were 7%, 30%, and 66%, respectively (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Nonoperative management of blunt splenic trauma: a multicenter experience

The experience of six referral trauma centers with 832 blunt splenic injuries was reviewed to determine the indications, methods, and outcome of nonoperative management. During this 5-year period, 112 splenic injuries were intentionally managed by observation. There were 40 (36%) patients less than 16 years old and 72 adults. The diagnosis was established by computed tomography in 89 (79%) patients, nuclear scan in 23 (21%), ultrasound in four (4%), and arteriography in two (2%). There were 28 Class I, 51 Class II, 31 Class III, two Class IV, and no Class V splenic injuries. Nonoperative management was unsuccessful in one (2%) child and 12 (17%) adults (p less than 0.05). Failure was due to ongoing hemorrhage in 12 patients and delayed recognition of pancreatic injury in one patient. Of the 12 patients ultimately requiring laparotomy for control of hemorrhage, seven (58%) were successfully treated with splenic salvage techniques. Overall mortality was 3%; none of the four deaths was due to splenic or associated abdominal injury. This contemporary multicenter experience suggests that patients with Class I, II, or III splenic injuries after blunt trauma are candidates for nonoperative management if there is: 1) no hemodynamic instability after initial fluid resuscitation; 2) no serious associated abdominal organ injury; and 3) no extra-abdominal condition which precludes assessment of the abdomen. Strict adherence to these principles yielded initial nonoperative success in 98% of children and 83% of adults. Application of standard splenic salvage techniques to treat the patients with persistent hemorrhage resulted in ultimate splenic preservation in 100% of children and 93% of adults.     

Hypomagnesemia: higher risk using total parenteral nutrition in the treatment of patients with malignancies

The syndrome of hypomagnesemia in patients receiving total parenteral nutrition (TPN) is well known. To determine particular high-risk groups for the development of this syndrome, 26 consecutive patients on TPN were initially evaluated for serum magnesium (Mg) and followed at regular intervals. Seventeen had a diagnosis of solid tumor or hematologic malignancy (CA); nine had inflammatory bowel disease and/or small bowel fistulae (ID). All met the standard criteria for being malnourished--anergy, low serum albumin, and recent weight loss. During TPN, all patients received an average of 24 mEq of magnesium sulfate per day, and all had satisfactory anabolic response in terms of weight gain and increase in serum albumin. Ten patients had at least one magnesium determination below the lower limits of normal, and four of these developed symptoms of tremor which responded to increased amounts of magnesium in their TPN. Eight of these ten (80%) had a diagnosis of CA, and four of four (100%) of those requiring additional magnesium to alleviate symptoms had CA. None of the patients with ID developed symptomatic hypomagnesemia. We conclude that patients with solid tumor malignancy are more likely to develop hypomagnesemia, possibly because of the increased requirements for magnesium in lymphocytolysis of tumor cells., and they must be carefully monitored to prevent this complication.