Mechanisms of signal change during intraoperative somatosensory evoked potential monitoring of the spinal cord.

In scoliosis surgery, intraoperative somatosensory evoked potential (SSEP) monitoring has reduced the incidence of postoperative neurologic deficits. Many factors affect the amplitude and latency of SSEP waveforms during surgery. Somatosensory evoked potential amplitude decreases with ischemia and anoxia because of temporal dispersion of the afferent volley and conduction block in damaged axons. In conjunction with surgical manipulations, minor drops in blood pressure may result in substantial SSEP changes that reverse when perfusion pressure is increased. Irreversible anoxic injury to central nervous system white matter with loss of SSEP waveforms is dependent on calcium influx into the intracellular space. Somatosensory evoked potential monitoring may be less sensitive for detecting acute insults in the presence of preexisting white matter lesions. Increased extracellular potassium from acute baro-trauma can block axonal conduction transiently even when there is no axonal disruption. Marked temperature-related drops in SSEP amplitude may occur after exposure of the spine but before instrumentation and deformity correction. Hypothermia may increase false-negative outcomes. Short-interval double-pulse stimulation may improve the sensitivity of the SSEP in detecting early ischemic changes. For neurosurgical procedures on the spinal cord the use of SSEP monitoring in improving postoperative outcome is less well established.     

Inhibition of aldo-keto reductases by phenobarbital alters metabolism, pharmacokinetics and toxicity of doxorubicin in rats

Doxorubicin is an effective anticancer agent that is limited by numerous adverse effects, cardiotoxicity causing the most concern. Its alcohol metabolite, doxorubicinol, and free radicals have been implicated in the aetiology of this toxicity. This study was based on the premise that inhibition of aldo-keto reductases would improve the efficacy of doxorubicin by reducing its toxic metabolites and modifying its pharmacokinetics. We assessed the effect of in-vitro inhibition of aldo-keto reductases on the metabolism of doxorubicin in cytosolic fractions of heart and liver of rats in the presence of Na-phenobarbital. The inhibition was confirmed by a significant reduction in the formation of doxorubicinol. The results of the in-vitro study were further evaluated in-vivo. The concentrations of doxorubicin in plasma, bile and urine and its major metabolites in bile and urine were measured in Na-phenobarbital-pretreated rats. Each rat received 100 mg kg(-1)/day intraperitoneal injection of sodium phenobarbital for three days followed by a single intravenous dose of 10 mg kg(-1) [14C-14]doxorubicin (sp. act. 0.2 microCi mg(-1)) on the fourth day. The levels of drug in all biological samples were measured by HPLC. The pretreatment resulted in an increase in biological half-life (5.8 +/- 1.5 vs 3.7 +/- 0.93 h control group, P < 0.05) and area under plasma concentration-time curve (19.6 +/- 1.7 vs 14.65 +/- 1.68 mg h L(-1) control group, P < 0.05). The cumulative amount of doxorubicinol in the bile and urine of pretreated animals was reduced significantly. In terms of % dose, the amount in the bile declined from 4.2 +/- 0.8% in control to 2.4 +/- 0.3% and in urine from 0.18 +/- 0.08% to 0.12 +/- 0.07%. There were no significant changes in doxorubicin aglycone and doxorubicinol aglycone. Serum creatine kinase levels were measured as a biomarker of damage to cardiac muscle. The area under creatine kinase level-time curve was reduced by approximately 50% in phenobarbital-pretreated animals. The results indicate that the inhibition of aldo-keto reductase could provide a useful approach to improve the safety of doxorubicin by reducing its alcohol metabolite. Furthermore, if the reduction in the area under the serum creatine kinase-time curve represents a reduced damage to heart muscle, it can be concluded that doxorubicinol plays an important role in this injury.     

Natural and anthropogenic radioactivity levels and the associated radiation hazard in the soil of Oodalia Tea Estate in the hilly region of Fatickchari in Chittagong,Bangladesh

Radioactivity in the soil of a tea garden in the Fatickchari area in Chittagong, Bangladesh, was measured using a high-resolution HPGe detector. The soil samples were collected from depths of up to 20 cm beneath the soil surface. The activity concentrations of naturally occurring ²³⁸U and ²³²Th were observed to be in the range of 27 ± 7 to 53 ± 8 Bq kg⁻¹ and 36 ± 11 to 72 ± 11 Bq kg⁻¹, respectively. The activity concentration of ⁴⁰K ranged from 201 ± 78 to 672 ± 81 Bq kg⁻¹, and the highest activity of fallout ¹³⁷Cs observed was 10 ± 1 Bq kg⁻¹. The average activity concentration observed for ²³⁸U was 39 ± 8 Bq kg⁻¹, for ²³²Th was 57 ± 11 Bq kg⁻¹, for ⁴⁰K was 384 ± 79 Bq kg⁻¹ and for ¹³⁷Cs was 5 ± 0.5 Bq kg⁻¹. The radiological hazard parameters (representative level index, radium equivalent activity, outdoor and indoor dose rates, outdoor and indoor annual effective dose equivalents, and radiation hazard index) were calculated from the radioactivity in the soil.     

Influence of vessel diameter on the efficacy of distal protection devices during saphenous vein graft intervention

We sought to determine the influence of vessel diameter on the efficacy of distal protection devices during saphenous vein graft intervention. From the Filterwire EX Randomized Evaluation trial, in which patients who underwent saphenous vein graft stenting were randomized to distal protection with the GuardWire or FilterWire EX, outcomes in 572 patients were examined in vessel size tertiles. The 30-day composite incidence of major adverse cardiac events (MACEs) increased with vessel size and was 6.9%, 9.7%, and 14.9% in the smallest, middle, and largest tertiles, respectively (p = 0.04). MACE rates were relatively vessel size independent for the GuardWire but increased steadily with vessel size with the FilterWire EX. In the smallest tertile, MACEs were reduced by 71% with the FilterWire EX compared with the GuardWire (p = 0.05), with the devices showing similar event rates in the other tertiles.     

Outcomes of endoscopic treatment of gastroduodenal Dieulafoy's lesion with rubber band ligation and thermal/injection therapy

BACKGROUND: Dieulafoy's lesion is a rare but important cause of upper gastrointestinal bleeding. Current endoscopic methods used to treat Dieulafoy's lesion include injection, with or without thermal methods, and mechanical methods. The latter include variceal ligation and hemoclips. There are no studies comparing the outcomes of rubber band ligation and injection with or without thermal therapy. AIM: To report the outcomes of Dieulafoy's lesion treated endoscopically with rubber band ligation and injection with or without thermal therapy at a single institution. METHODS: Patients with the diagnosis of Dieulafoy's lesion treated endoscopically at the Carl T. Hayden VA Medical Center in Phoenix, between August 1994 and August 2002 were analyzed. Demographic data, mode of presentation, risk factors for gastrointestinal bleeding, hemodynamic parameters, blood transfusion requirements, endoscopic findings, details of endoscopic therapy, length of stay in ICU/hospital, complications, recurrence of bleeding, and mortality rates were collected and compared between those receiving endoscopic band ligation (EBL group) and those receiving injection with or without thermal therapy (non-EBL group). RESULTS: Twenty-three patients with Dieulafoy's lesion (14 in the EBL group and nine in the non-EBL group) were studied. All patients were men. The mean age, hemoglobin levels on admission, and the transfusion requirements before therapy were similar in both groups. Fourteen patients (eight in the EBL- and six in the non-EBL groups) presented with hematemesis and the remaining with melena. The majority of Dieulafoy's lesions (91.3%) were located in the stomach and two in the duodenum. Active bleeding at the time of endoscopy was seen in 61% of cases, and immediate hemostasis was achieved with either method in 100% of patients. Early rebleeding (within 72 hours of endoscopic therapy) occurred in only one patient treated with epinephrine plus heater probe therapy. The length of stay in ICU was longer in the non-EBL group (6.7 days) compared with the EBL group (1.8 days) (P = 0.2). There were six deaths (three in the non-EBL group and three in the EBL group) within 30 days of the index hospitalization. The causes of death included infection/sepsis (n = 3), complications of acute myocardial infarction (n = 2), and end-stage liver disease (n = 1). CONCLUSIONS: Endoscopic rubber band ligation is as effective as injection with or without thermal therapy in the treatment of Dieulafoy's lesion.     

Cognitive neuroscience of hemispatial neglect

Introduction. Patients with neglect often fail to be aware of stimuli located on their contralesional side - the side of space opposite their brain damage. Some patients show impairments in extrapersonal space; others within personal (body) space; and some in both. Although the neglect syndrome may be associated with a distorted perception of extrapersonal or personal space, recent investigations suggest that attentional, memory and motor deficits may be important additional components. Conclusion. Better understanding of these cognitive impairments holds the key to offering effective treatment for neglect, as well as providing important insights into normal brain function.