The effects of stimulus timing features on P300 speller performance

ObjectiveDespite numerous examinations of factors affecting P300 speller performance, the impact of stimulus presentation parameters remains incompletely understood. This study examines the effects of four distinct stimulus presentation parameters (stimulus-off time [ISI¹], interstimulus interval [ISI], flash duration, and flash-duration:ISI ratio) on the accuracy and efficiency of the P300 speller performance.MethodsEEG data from a 32-electrode set were recorded from six subjects using a row–column paradigm of the speller task and analyzed offline.ResultsP300 speller accuracy is affected by the number of trial repetitions (F(14,354) = 69.002, p < 0.0001), as expected. In addition, longer ISI and ISI¹ times resulted in higher accuracy and characters per minute [CPM] rates. Subsets of the entire group (i.e. good vs. poor performers) were compared to show consistency of performance trends despite great variance among subjects. Moreover, the same significant effects were observed whether using the entire 32-electrode dataset or the reduced 8-channel set described by Sharbrough et al. (1991).ConclusionsDespite variability in user performance, both ISI¹ and ISI can affect P300 speller performance.SignificanceP300 system optimization must consider critical stimulus timing features including ISI¹ and ISI. Further characterization of the impact of these timing features in online experiments is warranted and the differential effect on accuracy and CPM should be more comprehensively explored.     

Pre- and post-intervention study to assess the impact of a sedation protocol in critically ill surgical patients

Introduction

Sedation and pain management for mechanically ventilated critically ill surgical patients pose many challenges for the intensivist. Even though daily interruption of sedatives and opioids is appropriate in medical intensive care unit (ICU) patients, it may not be feasible in the surgical patients with pain from surgical incision or trauma. Therefore we developed an analgesia/sedation based protocol for the surgical ICU population.

Methods

We performed a two-phase prospective observational control study. We evaluated a prescriber driven analgesia/sedation protocol (ASP) in a 12-bed surgical ICU. The pre-ASP group was sedated as usual (n = 100) and the post-ASP group was managed with the new ASP (n = 100). Each phase of the study lasted for 5 mo. Comparisons between the two groups were performed by χ² or Fisher’s exact test for categorical variables and the Mann-Whitney test for nonparametric variables. A P value <0.05 was statistically significant.

Results

We found a significant reduction in the use of fentanyl (P < 0.001) and midazolam (P = 0.001). We achieved sedation goals of 86.8% in the post-ASP group compared to 74.4% in the pre-ASP (P < 0.001). Mean mechanical ventilations days in pre- and post-ASP group were 5.9 versus 3.8 (P = 0.033).

Conclusion

In our cohort of critically ill surgery patients implementation of an ASP resulted in reduced use of continuously infused benzodiazepines and opioids, a decline in cumulative benzodiazepine and analgesic dosages, and a greater percentage of Richmond Agitation Sedation Scale scores at goal. We also showed reduced mechanical ventilation days.     

African American Renal Transplant Recipients (RTR) Require Higher Tacrolimus Doses to Achieve Target Levels Compared to White RTR: Does Clotrimazole Help?

The number of African Americans (AAs) on the kidney waiting list is increasing in the United States. Several studies showed that AAs are at higher risk for rejection and graft loss. Because of genetic polymorphisms, AAs may metabolize calcineurin inhibitors faster than Caucasian (C) individuals. The goal of this study is to evaluate the tacrolimus (TAC) dose required to reach therapeutic levels and to assess the impact of clotrimazole on TAC metabolism in AAs compared to C patients. One hundred forty-two AA renal transplant recipients (RTRs) were compared to 309 C RTRs. Demographics were similar in both groups. Induction therapy and maintenance immunosuppression were similar in both groups and included TAC, mycophenolate acid (MPA), and steroids. The goal in all RTRs was to maintain a 12-hour trough level of 10 to 15 ng/mL in the first 3 months, 8 to 10 ng/mL for the first year, and 5 to 8 ng/mL thereafter. To achieve these levels, AA RTRs require a significantly higher dosage of TAC compared to C patients (5.9 ± 2.9 vs 3.6 ± 2 mg/d, respectively, P < .0001). By multivariate analysis, TAC dose requirements were not affected by age, gender, MPA or prednisone dose, diabetes, and renal function. Adding clotrimazole (CTM) to the RTR regimen significantly reduced the TAC dose requirements in all RTRs. When CTM was used, the TAC dose requirement was not statistically significantly different between AA and C patients (2.6 ± 1.2 mg/d vs 1.8 ± 1.5 mg/d, P = .07). We conclude that AAs required a higher TAC dose to reach the desired trough level in RTRs compared to C RTRs. The use of CTM eliminates the need for higher doses of TAC in AA RTRs. Thus, CTM may aid AA RTRs in achieving therapeutic TAC levels while reducing drug costs.     

Structural and pharmacological profile of generic enoxaparins used in Brazil

Generic active pharmaceutical ingredients (APIs) have been commonly used in Brazil, since 1999, but most of them are synthetic and small molecules. Recently, a large number of generic enoxaparins were introduced into the market raising concerns related to product-to-product interchangeability, efficiency, and drug counterfeiting. These drugs are produced from biological sources and their production involves complex procedures and purification processes. The present article evaluates several generic enoxaparins, structurally and pharmacologically, and compares them with the branded products. Structural analysis showed that the generic products are, indeed, quite similar to the branded products, however, this similarity cannot be extended to their pharmacological activities. The results showed that generic products must go through extensive structural, pharmacological, and clinical evaluation in order to assess their quality, efficacy and, ultimately, avoid drug counterfeiting before clinical use. Variation was also observed between the branded products, showing that such drugs must be at constant surveillance.     

The impact of hemodialysis on retinal and choroidal thickness in patients with chronic renal failure

International Ophthalmology - Patients with chronic renal failure are commonly cared using a blood filtration mechanism like hemodialysis. Little information is available regarding ocular changes...