No time for drifting: Comparing performance and applicability of signal detrending algorithms for real-time fMRI.

As a consequence of recent technological advances in the field of functional magnetic resonance imaging (fMRI), results can now be made available in real-time. This allows for novel applications such as online quality assurance of the acquisition, intra-operative fMRI, brain-computer-interfaces, and neurofeedback. To that aim, signal processing algorithms for real-time fMRI must reliably correct signal contaminations due to physiological noise, head motion, and scanner drift. The aim of this study was to compare performance of the commonly used online detrending algorithms exponential moving average (EMA), incremental general linear model (iGLM) and sliding window iGLM (iGLMwindow). For comparison, we also included offline detrending algorithms (i.e., MATLAB's and SPM8's native detrending functions). Additionally, we optimized the EMA control parameter, by assessing the algorithm's performance on a simulated data set with an exhaustive set of realistic experimental design parameters. First, we optimized the free parameters of the online and offline detrending algorithms. Next, using simulated data, we systematically compared the performance of the algorithms with respect to varying levels of Gaussian and colored noise, linear and non-linear drifts, spikes, and step function artifacts. Additionally, using in vivo data from an actual rt-fMRI experiment, we validated our results in a post hoc offline comparison of the different detrending algorithms. Quantitative measures show that all algorithms perform well, even though they are differently affected by the different artifact types. The iGLM approach outperforms the other online algorithms and achieves online detrending performance that is as good as that of offline procedures. These results may guide developers and users of real-time fMRI analyses tools to best account for the problem of signal drifts in real-time fMRI.

Beta-adrenergic receptors (betaAR) regulate cardiomyocyte proliferation during early postnatal life.

Cardiomyocyte development switches from hyperplasmic to hypertrophic growth between postnatal days 3 and 4 in rats. The mechanisms responsible for this transition have been controversial. beta-Adrenergic receptor (betaAR) activation of mitogenic responses in vitro has been reported. We hypothesized that tonic activation of the betaAR signaling regulates cell division in neonatal cardiomyocytes via effects on signaling kinases known to be important in cell cycle regulation. The purpose of the current study was to elucidate the roles of betaAR in rat cardiomyocyte growth in vivo. We demonstrated that betaAR blockade induced a significant reduction in cardiomyocyte proliferation as measured by the BrdU labeling index. Blockade of betaAR did not affect p38 or p44/42 MAPK activities. We further demonstrated that betaAR blockade induced a prompt deactivation of the p70 ribosomal protein S6 kinase (p70 S6K). To confirm these results, we measured p70 S6K activity directly. Basal activity of p70 S6K in neonatal cardiomyocytes was fourfold higher than that of insulin-treated adult rat liver. The activity of p70 S6K was reduced by 60% within 1 min after betaAR blockade. We conclude that the betaAR are involved in regulation of neonatal cardiomyocyte proliferation and that this mitogenic control may be mediated via the p70 S6K pathway.

A case-control study of patients readmitted to the intensive care unit.

OBJECTIVE: To determine characteristics of patients requiring readmission to an intensive care unit (ICU). DESIGN: Retrospective case-control chart review. SETTING: Adult patients in an 8-bed medical and 16-bed surgical ICU in a 650-bed university teaching hospital during an 18-month period. INTERVENTIONS: None. METHODS: Each patient readmitted to either ICU was compared to a single control patient matched for age, sex, unit, and diagnosis. A total of 117 variables were obtained from chart review. The last value for each variable before ICU discharge was used. Chi-square analysis, linear regression factor analysis, correlation, and Student's t-test were used to identify significant factors predicting the patient's return to an ICU. Descriptive statistics were used to describe various subgroups. RESULTS: Mortality rate was 41.5% in the 82 readmitted patients (comprising 4.6% of the total ICU admissions) and only 7.3% in the controls. Mean (+/- SD) hospital length of stay was 47.8 +/- 42.0 days in the study group and 20.8 +/- 14.2 days (p < .0009) in the controls. Initial ICU length of stay was 8.3 +/- 16.1 days in the readmitted group and 4.0 +/- 5.0 days (p = .02) in the controls. Variables that predicted readmission to the ICU were: increased respiratory rate (24.2 vs. 20 breaths/min, p < .002), lower hematocrit value (31.9% vs. 34.4%, p = .01), positive fluid balance (p < .03), and positive blood cultures (six in the readmitted group, none in the controls, p = .002). More than 30% of readmissions were for a recurrence or worsening of the original problem. Fifty-four percent of the patients were readmitted with pulmonary failure. Mortality rate in both groups was related to advanced age, Acute Physiology and Chronic Health Evaluation (APACHE II) scores at ICU discharge, and increased blood urea nitrogen concentrations. Mortality rate in the control group, but not in the readmitted group, correlated with the level of consciousness, serum creatinine concentration, and use of hemodialysis. CONCLUSIONS: Readmission to an ICU carries a risk of high mortality rate and increased length of stay and may represent premature discharge in at least 30% of patients. Pulmonary failure is the immediate cause of readmission in more than half of the readmitted patients. Increased respiratory rate correlates with ICU readmission. Intermediate care areas for patients with poor pulmonary function may help to avoid readmission to an ICU, prevent death, and conserve hospital resources.

Optimal atrioventricular (AV) pacing interval during temporary AV sequential pacing after cardiac surgery.

Temporary dual chamber atrioventricular (AV) pacing is often used to increase cardiac output (CO) after cardiac surgery. The AV interval was varied to investigate the effect on CO in 13 patients. CO was computed from the Fick principle using mixed venous oxygen saturation (SvO2), arterial oxygen saturation (SaO2), hemoglobin, and oxygen consumption (VO2). AV intervals were varied randomly from 0.025 to 0.300 seconds in 0.025-second increments. The effect on CO from increasing the AV interval was dependent on the control CO. In all patients, as the AV interval was increased from 0.025 to 0.100 seconds, CO progressively increased. In most patients, the highest (optimal) CO occurred with AV pacing and averaged 300 mL/min greater than with atrial (A) pacing alone (P < .0001). In patients with a high initial CO (> 6.0 L/min), CO peaked and averaged 0.5 L/min more than with A pacing. CO was maximal for each of these patients at a unique AV interval between 0.100 and 0.225 seconds, and at intervals greater than 0.225 seconds CO decreased (P < .01). In patients with intermediate CO (4-6 L/min) at AV intervals greater than 0.100 seconds, a plateau in CO was reached. No consistent pattern was seen in patients with low initial CO (< 4.0 L/min). Maximal CO may be achieved by optimizing the AV interval in patients following cardiac surgery. The optimal AV interval is between 0.100 and 0.225 seconds and is different for each patient. Continuous SvO2 monitoring allows rapid evaluation of CO changes and optimization of the AV pacing interval.

Hemodynamic and metabolic effects of dobutamine in 18 patients after open heart surgery.

Low cardiac output syndrome frequently follows cardiopulmonary bypass (CPB) surgery. In the present study, we used dobutamine to increase cardiac index (CI) and oxygen delivery (DO2) in 18 patients after open heart surgery. Using increasing doses of dobutamine up to 10 micrograms/kg.min-1, we observed statistically significant (p less than .01) increases in mean CI (2.50 +/- 0.10 to 3.56 +/- 0.18 L/min.m2) and in mean heart rate (HR) (83 +/- 3 to 105 +/- 3 beat/min). Mean systemic vascular resistance index decreased significantly (p less than .01) in all patients (2271 +/- 101 to 1648 +/- 83 dyne.sec/cm5.m2). Pulmonary vascular resistance index did not change in the ten coronary artery bypass graft patients, but decreased significantly (p less than .01) in the eight valve replacement patients (561 +/- 98 to 421 +/- 79 dyne.sec/cm5.m2). Mean DO2 increased in all patients, although there was no concomitant increase in oxygen consumption (VO2) in four patients. We observed a significant (p less than .01) increase in mean VO2 in the remaining 14 patients (110 +/- 6 to 148 +/- 12 ml/min.m2), in spite of significant decreases in PaO2 and increases in right-to-left intrapulmonary shunting. Although increases in HR and ventricular arrhythmias may limit its use, dobutamine increases CI and DO2 in patients after CPB. In the present study, dobutamine's varying metabolic effect exemplifies the need for close monitoring of hemodynamic and metabolic variables when using vasoactive drugs in the postoperative period.

Pulmonary artery catheter deterioration during hydrochloric acid infusion for the treatment of metabolic alkalosis.

Hydrochloric acid (HCl) infusions for the correction of metabolic alkalosis have been used for 20 yr. In the critical care setting, HCl is usually infused through a central venous or pulmonary artery (PA) catheter. In two patients receiving HCl infusions through a PA catheter, we observed and examined solid yellow particulate material in the aspirating syringe while testing the proximal lumen for patiency. We carried out in vitro investigation infusing PA catheters with 0.1, 0.2, 0.3, and 0.4 normal HCl at 20 degrees, 38 degrees, and 42 degrees C for 24 and 48 h. Although frank catheter deterioration could not be documented, the surface and interior of those catheters infused with greater than 0.1 normal HCl changed texture, indicating a change in catheter composition. Exceeding a concentration of 0.1 normal is not recommended when HCl is infused through PA catheters.

Efficacy of an attachable subcutaneous cuff for the prevention of intravascular catheter-related infection. A randomized, controlled trial.

We performed a randomized controlled trial of an attachable subcutaneous cuff for the prevention of central vascular catheter-related infection among patients receiving intensive care. Catheters were placed percutaneously into new sites with or without a cuff and were dressed with polyantibiotic ointment containing polymyxin, neomycin, and bacitracin. Microbial colonization developed in 34.5% of 29 control and 7.7% of 26 cuffed catheters. Catheter-related bloodstream infection occurred with 13.8% of control vs 0% of cuffed catheters. The cuff was not associated with adverse effects. An unexpectedly large proportion (75%) of catheter infections were due to Candida albicans. This may have been due, in part, to the use of polyantibiotic ointment, as suggested by a pooled analysis of previous trials that demonstrated increased Candida colonization of catheters with the ointment, which is not fungicidal. These data suggest that the cuff can reduce the incidence of catheter-related infection among high-risk patients receiving catheter site care with an antibacterial ointment.

Decreased prolactin secretion by decidual tissue of pre-eclampsia in vitro.

In vitro prolactin (hPrl) secretion by explants of decidual tissue was studied in pre-eclampsia and normal controls. Our results indicate diminished hPrl production by decidua of pre-eclampsia as compared to the normal controls. Incubation of normal decidual tissue in the presence of serum obtained from pre-eclamptic patients did not induce an inhibitory effect on hPrl production.

Hereditary heat-labile hexosaminidase B: a variant whose homozygotes synthesize a functional HEX A.

Homozygosity for a mutant allele at the beta-chain locus of hexosaminidase (HEX), resulting in a variant of heat-labile HEX B, is reported for the first time in two healthy children. HEX activity in their sera, leukocytes, and cultured skin fibroblasts is severely deficient when measured on the synthetic substrate 4-MU-GLcNAc. However, their cultured skin fibroblasts synthesize and process both alpha and beta chains of HEX, and their lymphoid cells hydrolyze normally the natural ganglioside GM2. This mutation is, therefore, different from at least one of the beta-chain mutations found in previously published families with heat-labile HEX B.

Hereditary heat-labile hexosaminidase B: its implication for recognizing Tay-Sachs genotypes.

Two pairs of alleles, at the two loci of hexosaminidase (HEX), were found to segregate in an Arab inbred family: the normal and the mutant Tay-Sachs (TSD) alleles of HEX A, and the normal and a mutant allele of HEX B. Since the mutant HEX B is heat labile, no reliable identification of TSD genotypes can be obtained in its presence, as long as the proportions of HEX A and B are estimated by the routinely used heat-inactivation method. The genotypes may be correctly identified in such cases by separation of the two isoenzymes on ion-exchange chromatography, estimating their individual activities, and calculating the ratio between them. Of the nine genotype combinations possible with these two pairs of alleles, five have been identified in the reported family by this procedure.

Death on every weekend.

This essay is a personal account of situations experienced by a medical technician in a large emergency room. It includes examples of stressful situations that daily confront medical personnel and the inability of medical institutions to aid them in understanding and coping with death and.dying. Stemming from these stressful situations, the paper illustrates the importance of the need for medical institutions to pay direct attention to the stressful topic of death itself if the medical personnel are to work efficiently in an environment where death and dying are everyday occurrences. Although some institutions do offer in-service sessions to nurses, these services are far and few between. But the stress for all medical personnel remains high, and there remains an unfulfilled need to teach effective thanatological techniques to all medical personnel.