The association of prior paracetamol intake with outcome of very old intensive care patients with COVID-19: results from an international prospective multicentre trial

BACKGROUND

In the early COVID-19 pandemic concerns about the correct choice of analgesics in patients with COVID-19 were raised. Little data was available on potential usefulness or harmfulness of prescription free analgesics, such as paracetamol. This international multicentre study addresses that lack of evidence regarding the usefulness or potential harm of paracetamol intake prior to ICU admission in a setting of COVID-19 disease within a large, prospectively enrolled cohort of critically ill and frail intensive care unit (ICU) patients.

METHODS

This prospective international observation study (The COVIP study) recruited ICU patients ≥ 70 years admitted with COVID-19. Data on Sequential Organ Failure Assessment (SOFA) score, prior paracetamol intake within 10 days before admission, ICU therapy, limitations of care and survival during the ICU stay, at 30 days, and 3 months. Paracetamol intake was analysed for associations with ICU-, 30-day- and 3-month-mortality using Kaplan Meier analysis. Furthermore, sensitivity analyses were used to stratify 30-day-mortality in subgroups for patient-specific characteristics using logistic regression.

RESULTS

44% of the 2,646 patients with data recorded regarding paracetamol intake within 10 days prior to ICU admission took paracetamol. There was no difference in age between patients with and without paracetamol intake. Patients taking paracetamol suffered from more co-morbidities, namely diabetes mellitus (43% versus 34%, p < 0.001), arterial hypertension (70% versus 65%, p = 0.006) and had a higher score on Clinical Frailty Scale (CFS; IQR 2-5 versus IQR 2-4, p < 0.001). Patients under prior paracetamol treatment were less often subjected to intubation and vasopressor use, compared to patients without paracetamol intake (65 versus 71%, p < 0.001; 63 versus 69%, p = 0.007). Paracetamol intake was not associated with ICU-, 30-day- and 3-month-mortality, remaining true after multivariate adjusted analysis.

CONCLUSION

Paracetamol intake prior to ICU admission was not associated with short-term and 3-month mortality in old, critically ill intensive care patients suffering from COVID-19.

TRIAL REGISTRATION

This prospective international multicentre study was registered on ClinicalTrials.gov with the identifier "NCT04321265" on March 25, 2020.

Diabetes in urban Guinea-Bissau; patient characteristics, mortality and prevalence of undiagnosed dysglycemia

Background

The burden of diabetes mellitus in Sub-Saharan Africa is growing rapidly, and yet the prevalence and patient characteristics are still largely unknown.

Objectives

We analyzed clinical and demographic characteristics of Type 2 diabetes (T2DM) patients attending a diabetes clinic in Guinea-Bissau from February 2008 to April 2014, and estimated the prevalence and risk factors of unknown-impaired fasting plasma glucose (FPG) and diabetes, as well as excess mortality associated with T2DM.

Methods

We characterized T2DM patients attending the national diabetes clinic in Bissau. Diabetes was diagnosed based on FPG. We matched T2DM patients 1:1 with non-diabetes community controls on age and sex to determine relevant risk factors for T2DM using logistic regression. Furthermore, we matched patients 1:6 with community controls to assess long-term survival (until February 2019) in a Cox regression using calendar time as the underlying timescale. Verbal autopsies determined the cause of death among T2DM patients and controls.

Results

The mean age among T2DM was 50.6 (SD 11.1), and the mean FPG at first consultation was high (13.2 mmol/L (SD 5.1)). Ethnicity, family history of diabetes, hypertension, and anthropometrics differed among T2DM patients, community controls with impaired FPG, and healthy controls. Family history of diabetes (OR = 5.65, 95% CI: 3.10–10.3) and elevated waist circumference (2.33, 1.26–4.29) were significant risk factors for T2DM. 20.4% (59/289) of community controls had abnormal FPG. T2DM patients had an excess mortality hazard ratio of 3.53 (95%CI: 1.92–6.52). Deaths caused by bacterial infections, including foot ulcers, were more common among T2DM patients, compared with community controls (54% (7/13) vs. 19% (5/27) (P = 0.02)).

Conclusion

Several risk factors including were associated with T2DM in Guinea-Bissau. We found a high prevalence of elevated FPG among randomly selected community controls. In combination with higher mortality among T2DM patients, an urgent need for better treatment options and increased awareness.

Gabor patterns as stimuli in a rodent visual attention task

BACKGROUND

Gabor patterns are defined as the product of a sinusoid function and a Gaussian envelope and are commonly used in visual and attentional research due to their ability to selectively stimulate the primary visual cortex. The aim of this study was to investigate whether Gabor patterns can be used as visual stimuli in the rodent continuous performance test (rCPT), a newly developed task to study attentional function and impulsivity.

METHODS

Sixteen male C57BL/6 J mice were trained in the rCPT using Gabor patterns as visual stimuli and their performance was compared to sixteen mice that were trained using traditional high-contrast pattern stimuli. Mice were compared during training, baseline, and a variable stimulus duration probe.

RESULTS

The Gabor pattern group required more training sessions to reach criteria than the group with high-contrast patterns. At baseline, the Gabor pattern group showed a higher false alarm rate and a lower discriminability index. As task difficulty increased during the variable stimulus duration probe, differences between groups became more pronounced. Specifically, the Gabor pattern group showed decreased hit rate and discriminability index, as well as increased false alarm rate and premature responses compared to the high-contrast pattern group.

CONCLUSION

This feasibility study showed that it is possible to use Gabor patterns as visual stimuli in the rCPT, although it increases task demands. We discuss the differences between Gabor patterns and high-contrast patterns in the context of translatability of animal models in visual and cognitive research and give two examples of applicability.

Theory of Visual Attention (TVA) applied to mice in the 5-choice serial reaction time task

RATIONALE

The 5-choice serial reaction time task (5-CSRTT) is widely used to measure rodent attentional functions. In humans, many attention studies in healthy and clinical populations have used testing based on Bundesen's Theory of Visual Attention (TVA) to estimate visual processing speeds and other parameters of attentional capacity.

OBJECTIVES

We aimed to bridge these research fields by modifying the 5-CSRTT's design and by mathematically modelling data to derive attentional parameters analogous to human TVA-based measures.

METHODS

C57BL/6 mice were tested in two 1-h sessions on consecutive days with a version of the 5-CSRTT where stimulus duration (SD) probe length was varied based on information from previous TVA studies. Thereafter, a scopolamine hydrobromide (HBr; 0.125 or 0.25 mg/kg) pharmacological challenge was undertaken, using a Latin square design. Mean score values were modelled using a new three-parameter version of TVA to obtain estimates of visual processing speeds, visual thresholds and motor response baselines in each mouse.

RESULTS

The parameter estimates for each animal were reliable across sessions, showing that the data were stable enough to support analysis on an individual level. Scopolamine HBr dose-dependently reduced 5-CSRTT attentional performance while also increasing reward collection latency at the highest dose. Upon TVA modelling, scopolamine HBr significantly reduced visual processing speed at both doses, while having less pronounced effects on visual thresholds and motor response baselines.

CONCLUSIONS

This study shows for the first time how 5-CSRTT performance in mice can be mathematically modelled to yield estimates of attentional capacity that are directly comparable to estimates from human studies.

Automatic attraction of attention to former targets in visual displays of letters

Shiffrin and Schneider (1977, Experiment 4d) reported that after consistent training in search for particular alphanumeric characters, presentation of one of these characters (former targets) as a distractor impeded detection of simultaneously presented current targets. Even if presented in an irrelevant display location, the former target appeared to attract attention. Here, we analyze weaknesses in the design of Experiment 4d and report four follow-up experiments ranging from a fairly close replication of the original multiframe experiment to a rather conventional single-frame search study. In each experiment, presentation of former targets consistently impeded detection of simultaneously presented current targets. The results suggest that automatic attention attraction to individual alphanumeric characters develops not only in the special experimental paradigm used by Shiffrin and Schneider, but also in standard visual search tasks. The fact that attention appeared to be attracted by shapes as complex as individual letters supports the assumption that simultaneously presented visual stimuli can be compared in parallel against memory representations of alphanumeric characters.

Brain activation during mental transformation of size

Visual comparison between different-sized objects with respect to shape can be done by encoding one of the objects as a mental image, transforming the image to the size format of the other object, and then testing for a match (Bundesen, C., & Larsen, A. [1975]. Visual transformation of size. Journal of Experimental Psychology: Human Perception and Performance, 1, 214-220). To identify the brain structures implicated in mental transformation of size, we measured the distribution of regional cerebral blood flow (rCBF) by positron emission tomography (PET) in 12 normal subjects who compared random stimulus patterns with respect to shape regardless of variations in size in a one-back match-to-sample paradigm. Each subject was PET-scanned 12 times during repetitive injections of H(2)(15)O. In one condition (three scans), all stimulus patterns were small. In a second condition (three scans), all stimuli were large. In the third condition (six scans), the stimuli alternated between small and large. Mental transformation of size should occur in the alternating-size condition but not in the fixed-size conditions. As expected, behavioral measures (reaction time [RT], d', beta) were nearly the same for the two fixed-size conditions but mean RT was longer and d' smaller in the alternating-size condition. Changes in rCBF specific to mental transformation of size were estimated by contrasting the alternating-size with the fixed-size conditions by use of statistical parametric mapping (SPM96) at a threshold of p <. 05 corrected for multiple comparisons. The detected brain structures implicated in mental transformation of size were primarily located in the dorsal pathways, comprising structures in the occipital, parietal, and temporal transition zone (predominantly in the left hemisphere), posterior parietal cortex (bilaterally), area MT/V5 (left), and vermis (bilaterally). Contrasts between the two fixed-size conditions showed significant effects in only the occipital cortex.

Systematic analysis of deficits in visual attention

A variety of impairments in visual attention can follow damage to the brain. The authors develop systematic methods for analyzing such impairments in terms of C. Bundesen's (1990) Theory of Visual Attention and apply these in a group of 9 patients with parietal lobe lesions and variable spatial neglect. In whole report, patients report letters from brief, vertical arrays in left or right visual field. The results show substantial, largely bilateral impairments in processing capacity, implying a major nonlateralized aspect to neglect. In partial report, arrays contain 1 or 2 letters in red and/or green. The task is to report only those letters in a specified target color. In addition to the expected bias against left-sided letters, patients show striking, bilateral preservation of top-down control, or attentional priority for targets. The results show how differentiation of attentional impairments can be informed by a theory of normal function.

Systematic analysis of deficits in visual attention

A variety of impairments in visual attention can follow damage to the brain. The authors develop systematic methods for analyzing such impairments in terms of C. Bundesen's (1990) Theory of Visual Attention and apply these in a group of 9 patients with parietal lobe lesions and variable spatial neglect. In whole report, patients report letters from brief, vertical arrays in left or right visual field. The results show substantial, largely bilateral impairments in processing capacity, implying a major nonlateralized aspect to neglect. In partial report, arrays contain 1 or 2 letters in red and/or green. The task is to report only those letters in a specified target color. In addition to the expected bias against left-sided letters, patients show striking, bilateral preservation of top-down control, or attentional priority for targets. The results show how differentiation of attentional impairments can be informed by a theory of normal function.

A computational theory of visual attention

A computational theory of visual attention is presented. The basic theory (TVA) combines the biased-choice model for single-stimulus recognition with the fixed-capacity independent race model (FIRM) for selection from multi-element displays. TVA organizes a large body of experimental findings on performance in visual recognition and attention tasks. A recent development (CTVA) combines TVA with a theory of perceptual grouping by proximity. CTVA explains effects of perceptual grouping and spatial distance between items in multi-element displays. A new account of spatial focusing is proposed in this paper. The account provides a framework for understanding visual search as an interplay between serial and parallel processes.

Effects of spatial separation in visual pattern matching: evidence on the role of mental translation

Effects of the spatial separation between 2 simultaneously presented random patterns on the ability to determine whether the patterns are identical up to a translational displacement across the retina were investigated by using signal-detection methods. The patterns to be compared were presented on the periphery of an imaginary circle centered on fixation. Exposures were brief and postmasked. In Experiments 1 and 2, sensitivity (d') varied with exposure duration but not with the spatial separation between the patterns. In Experiment 3, the task was changed so that members of a "same" pair could differ by both a translation and a rotation. When the rotational component was O, d' was a monotonic decreasing function of the spatial separation between the stimuli. Apparently, in the special case, performance was based on mental alignment by a process of gradual mental translation of one of the members of a stimulus pair to the location of the other one.

Effects of spatial separation in visual pattern matching: evidence on the role of mental translation

Effects of the spatial separation between 2 simultaneously presented random patterns on the ability to determine whether the patterns are identical up to a translational displacement across the retina were investigated by using signal-detection methods. The patterns to be compared were presented on the periphery of an imaginary circle centered on fixation. Exposures were brief and postmasked. In Experiments 1 and 2, sensitivity (d') varied with exposure duration but not with the spatial separation between the patterns. In Experiment 3, the task was changed so that members of a "same" pair could differ by both a translation and a rotation. When the rotational component was O, d' was a monotonic decreasing function of the spatial separation between the stimuli. Apparently, in the special case, performance was based on mental alignment by a process of gradual mental translation of one of the members of a stimulus pair to the location of the other one.

Is visual attention automatically attracted to one's own name?

Subjects were presented with briefly exposed visual displays of words that were common first names with a length of four to six letters. In the main experiment, each display consisted of four words: two names shown in red and two shown in white. The subject's task was to report the red names (targets), but ignore the white ones (distractors). On some trials the subject's own name appeared as a display item (target or distractor). Presentation of the subject's name as a distractor caused no more interference with report of targets than did presentation of other names as distractors. Apparently, visual attention was not automatically attracted by the subject's own name.

A template-matching pandemonium recognizes unconstrained handwritten characters with high accuracy

Psychological data suggest that internal representations such as mental images can be used as templates in visual pattern recognition. But computational studies suggest that traditional template matching is insufficient for high-accuracy recognition of real-life patterns such as handwritten characters. Here we explore a model for visual pattern recognition that combines a template-matching and a feature-analysis approach: Character classification is based on weighted evidence from a number of analyzers (demons), each of which computes the degree of match between the input character and a stored template (a copy of a previously presented character). The template-matching pandemonium was trained to recognize totally unconstrained handwritten digits. With a mean of 37 templates per type of digit, the system has attained a recognition rate of 95.3%, which falls short of human performance by only 2%-3%.

Concept of visual sensation in a theory of visual attention: a theoretical note

An integrated account of visual sensation, recognition, and attentional selection is sketched in outline.

Visual selection of features and objects: is location special? A reinterpretation of Nissen's (1985) findings

Nissen (1985) compared selection by location with selection by color or shape in partial-report experiments. Her analysis of response contingencies when a target was defined in terms of one attribute (location, color, or shape), and when the task was to report the two remaining attributes, suggested a special role for selection by location: It appeared that cross-referencing between color and shape was mediated by location. An alternative interpretation is developed here: The findings are explained by a theory of attention (Bundesen, 1990), in which selection by location is treated on a par with selection by color or shape.

A theory of visual attention

A unified theory of visual recognition and attentional selection is developed by integrating the biased-choice model for single-stimulus recognition (Luce, 1963; Shepard, 1957) with a choice model for selection from multielement displays (Bundesen, Pedersen, & Larsen, 1984) in a race model framework. Mathematically, the theory is tractable, and it specifies the computations necessary for selection. The theory is applied to extant findings from a broad range of experimental paradigms. The findings include effects of object integrality in selective report, number and spatial position of targets in divided-attention paradigms, selection criterion and number of distracters in focused-attention paradigms, delay of selection cue in partial report, and consistent practice in search. On the whole, the quantitative fits are encouraging.

Visual selection from multielement displays: measuring and modeling effects of exposure duration

In a partial-report experiment, subjects reported the digits from a circular array of digits and letters terminated by a pattern mask. Individual frequency distributions of the number of correctly reported digits were analyzed as functions of number of digits (2, 4, or 6) and number of letters (0, 2, 4, 6, or 8) at nine exposure durations ranging from 10 to 200 ms. The distributions (hundreds of data points per subject) were accurately predicted by a four-parameter fixed-capacity independent race model that assumes exponentially distributed processing times, limitations in both processing capacity and storage capacity, and time-invariant selectivity. Estimated from the data, processing capacity C was 45 items/s, selectivity alpha (ratio between the amount of processing capacity devoted to a distractor and the amount devoted to a target) was 0.48, short-term storage capacity K was 3.5 items, and the longest ineffective exposure duration t0 was 18 ms.

Measuring efficiency of selection from briefly exposed visual displays: a model for partial report

In the proposed model for partial report, performance reflects the number of targets in a short-term memory buffer. The total number of items (targets, distractors, or extraneous noise) entering the buffer is independent of the number of targets and distractors in the stimulus. Entrance is determined by selective sampling according to a Luce (1959) ratio rule. The model was tested in a variety of conditions with partial reports based on brightness, color, shape, or alphanumeric class. With three parameters, the model accounted for 99% of the variance with number of targets and number of distractors in data obtained by averaging across conditions. Parameter K (number of items entering the buffer) showed little variation with the selection criterion, and estimates for parameter epsilon (total impact of extraneous noise with impact per target as the unit) were rather small. Estimates for parameter alpha (impact per distractor with impact per target as the unit) varied widely across conditions. Parameter alpha is a measure for the efficiency of selecting targets rather than distractors.

Measuring efficiency of selection from briefly exposed visual displays: a model for partial report

In the proposed model for partial report, performance reflects the number of targets in a short-term memory buffer. The total number of items (targets, distractors, or extraneous noise) entering the buffer is independent of the number of targets and distractors in the stimulus. Entrance is determined by selective sampling according to a Luce (1959) ratio rule. The model was tested in a variety of conditions with partial reports based on brightness, color, shape, or alphanumeric class. With three parameters, the model accounted for 99% of the variance with number of targets and number of distractors in data obtained by averaging across conditions. Parameter K (number of items entering the buffer) showed little variation with the selection criterion, and estimates for parameter epsilon (total impact of extraneous noise with impact per target as the unit) were rather small. Estimates for parameter alpha (impact per distractor with impact per target as the unit) varied widely across conditions. Parameter alpha is a measure for the efficiency of selecting targets rather than distractors.

Visual apparent movement: transformations of size and orientation

Sequential alternation between same-shaped stimuli differing in size (size ratio s) and orientation (angular difference v) produced a visual illusion of translation in depth and concurrent rotation. The minimum stimulus-onset asynchrony required for the appearance of a rigidly moving object was approximately a linearly increasing function of (s-1)/(s+1) for simple translation in depth and a linearly increasing function of v for simple rotation. The extrapolated zero intercept was lower for translation than for rotation, but estimated transformation times were additive in combined transformations. The results suggest that (a) the processes of apparent translation in depth and apparent rotation are individually sequential-additive in structure, and (b) apparent translations and rotations are combined by fine-grained alternation of steps of apparent translation and steps of apparent rotation. Similar principles account for recent data on imagined spatial transformations of visual size and orientation.

Velocity constraints on apparent rotational movement

The visual illusion of apparent rigid rotation was produced by sequential alternation of two views of the same object in different orientations. The minimum stimulus-onset asynchrony required for the appearance of rigid rotation was a linearly increasing function of the angular difference in orientation between the two views. Variation in the size of the object affected the zero-intercept of the function, but the slope was virtually constant. The slope invariance suggests that the appearance of rigid rotation is constrained by an upper bound on the apparent angular velocity of the object as a whole, rather than a bound on the linear velocity of its parts.

Size scaling in visual pattern recognition

Human visual recognition on the basis of shape but regardless of size was investigated by reaction time methods. For successive matching of random figures, reaction time increased linearly with the linear size ratio of stimulus pairs. For single-character classification, reaction time increased with divergence between cued size format and stimulus format such that for character nonrepetitions, the increment in latency was approximately proportional to the logarithm of the linear size ratio of the two formats. However, when reactions to character repetitions were faster than those to nonrepetitions, the repetition reaction time function was similar to that for successive matching of random figures. The results suggested two processes of size scaling: mental-image transformation and perceptual-scale transformation. Image transformation accounted for matching performance based on visual short-term memory, whereas scale transformation accounted for size invariance in recognition based on comparison against visual representations in long-term memory.

Size scaling in visual pattern recognition

Human visual recognition on the basis of shape but regardless of size was investigated by reaction time methods. For successive matching of random figures, reaction time increased linearly with the linear size ratio of stimulus pairs. For single-character classification, reaction time increased with divergence between cued size format and stimulus format such that for character nonrepetitions, the increment in latency was approximately proportional to the logarithm of the linear size ratio of the two formats. However, when reactions to character repetitions were faster than those to nonrepetitions, the repetition reaction time function was similar to that for successive matching of random figures. The results suggested two processes of size scaling: mental-image transformation and perceptual-scale transformation. Image transformation accounted for matching performance based on visual short-term memory, whereas scale transformation accounted for size invariance in recognition based on comparison against visual representations in long-term memory.

Concept of visual sensation

A direct-realist account of visual sensation is outlined. The explanatory notion of elements in visual sensation (atomic sensations) is reinterpreted, and the suggested interpretation is formally justified by constructing a Boolean algebra for visual sensations. The related notion of sensory levels (visual field vs visual world) is discussed.

Visual transformation of size

To investigate human visual identification of different-sized objects as identically shaped, matching reaction times were measured for pairs of simultaneously presented random figures. In three experiments, reaction time for correct reactions to test pairs of figures of the same shape and orientation consistently increased approximately linearly as a function of the linear size ratio of the figures. In the second experiment, where this ratio was defined for control pairs as well as for test pairs, reaction time for correct reactions to control pairs showed a similar increase as a function of size ratio. The results suggest that the task was performed by a gradual process of mental size transformation of one of the members of each pair of figures to the format of the other one.

Visual transformation of size

To investigate human visual identification of different-sized objects as identically shaped, matching reaction times were measured for pairs of simultaneously presented random figures. In three experiments, reaction time for correct reactions to test pairs of figures of the same shape and orientation consistently increased approximately linearly as a function of the linear size ratio of the figures. In the second experiment, where this ratio was defined for control pairs as well as for test pairs, reaction time for correct reactions to control pairs showed a similar increase as a function of size ratio. The results suggest that the task was performed by a gradual process of mental size transformation of one of the members of each pair of figures to the format of the other one.