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Pain is commonly assessed subjectively by interpretations of patient behaviour and/or reports from patients. When this is impossible the availability of a quantitative objective pain assessment tool based on objective physiological parameters would greatly benefit clinical practice and research beside the standard self-report tests. Vasoconstriction is one of the physiological responses to pain. The aim of this study was to investigate whether pulse transit time (PTT) and pulse wave amplitude (PWA) decrease in response to this vasoconstriction when caused by heat-induced pain. The PTT and PWA were measured in healthy volunteers, on both index fingers using photoplethysmography and electrocardiography. Each subject received 3 heat-induced pain stimuli using a Temperature-Sensory Analyzer thermode block to apply a controlled, increasing temperature from 32.0 °C to 50.0 °C to the skin. After reaching 50.0 °C, the thermode was immediately cooled down to 32.0 °C. The study population was divided into 2 groups with a time-interval between the stimuli 20s or 60s. The results showed a significant (p  <  0.05) decrease of both PTT and PWA on the stimulated and contralateral side. Moreover, there was no significant difference between the stimulated and contralateral side. The time-interval of 20s was too short to allow PTT and PWA to return to baseline values and should exceed 40s in future studies. Heat-induced pain causes a decrease of PTT and PWA. Consequently, it is expected that, in the future, PTT and PWA may be applied as objective indicators of pain, either beside the standard self-report test, or when self-report testing is impossible.

Fluid therapy after initial resuscitation in critically ill, septic patients may lead to harmful overloading and should therefore be guided by indicators of an increase in stroke volume (SV), i.e. fluid responsiveness. Our objective was to investigate whether tissue perfusion and oxygenation are able to monitor fluid responsiveness, even after initial resuscitation. Thirty-five critically ill, septic patients underwent infusion of 250 mL of colloids, after initial fluid resuscitation. Prior to and after fluid infusion, SV, cardiac output sublingual microcirculatory perfusion (SDF: sidestream dark field imaging) and skin perfusion and oxygenation (laser Doppler flowmetry and reflectance spectroscopy) were measured. Fluid responsiveness was defined by a ≥5 or 10% increase in SV upon fluids. In responders to fluids, SDF-derived microcirculatory and skin perfusion and oxygenation increased, but only the increase in cardiac output, mean arterial and pulse pressure, microvascular flow index and relative Hb concentration and oxygen saturation were able to monitor a SV increase. Our proof of principle study demonstrates that non-invasively assessed tissue perfusion and oxygenation is not inferior to invasive hemodynamic measurements in monitoring fluid responsiveness. However skin reflectance spectroscopy may be more helpful than sublingual SDF.

The skin's rewarming rate of diabetic patients is used as a diagnostic tool for early diagnosis of diabetic neuropathy. At present, the relationship between microvascular changes in the skin and diabetic neuropathy is unclear in streptozotocin (STZ) diabetic rats. The aim of this study was to investigate whether the skin rewarming rate in diabetic rats is related to microvascular changes and whether this is accompanied by changes observed in classical diagnostic methods for diabetic peripheral neuropathy. Computer-assisted infrared thermography was used to assess the rewarming rate after cold exposure on the plantar skin of STZ diabetic rats' hind paws. Peripheral neuropathy was determined by the density of intra-epidermal nerve fibers (IENFs), mechanical sensitivity, and electrophysiological recordings. Data were obtained in diabetic rats at four, six, and eight weeks after the induction of diabetes and in controls. Four weeks after the induction of diabetes, a delayed rewarming rate, decreased skin blood flow and decreased density of IENFs were observed. However, the mechanical hyposensitivity and decreased motor nerve conduction velocity (MNCV) developed 6 and 8 weeks after the induction of diabetes. Our study shows that the skin rewarming rate is related to microvascular changes in diabetic rats. Moreover, the skin rewarming rate is a non-invasive method that provides more information for an earlier diagnosis of peripheral neuropathy than the classical monofilament test and MNCV in STZ induced diabetic rats.

Corpus linguistics allows researchers to process millions of words. However, the more words we analyse, i.e., the more data we acquire, the more urgent the call for correct data interpretation becomes. In recent years, a number of studies saw the light attempting to profile some prolific authors' linguistic decline, linking this decline to pathological conditions such as Alzheimer's Disease (AD). However, in line with the nature of the (literary) work that was analysed, numbers alone do not suffice to 'tell the story'. The one and only objective of using statistical methods for the analysis of research data is to tell a story--what happened, when, and how. In the present study we describe a computerised but individualised approach to linguistic analysis--we propose a unifying approach, with firm grounds in Information Theory, that, independently from the specific parameter being investigated, guarantees to produce a robust model of the temporal dynamics of an author's linguistic richness over his or her lifetime. We applied this methodology to six renowned authors with an active writing life of four decades or more: Iris Murdoch, Gerard Reve, Hugo Claus, Agatha Christie, P.D. James, and Harry Mulisch. The first three were diagnosed with probable Alzheimer Disease, confirmed post-mortem for Iris Murdoch; this same condition was hypothesized for Agatha Christie. Our analysis reveals different evolutive patterns of lexical richness, in turn plausibly correlated with the authors' different conditions., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

The propagation time of arterial pulse waves provides information about arterial stiffness. Pulse arrival time (PAT) is calculated as the time between the R-wave (ECG) and three reference points on photoplethysmographic (PPG) pulse waves: foot, first derivative and peak. Because large variation in PAT-values between patients exists, measurements of the contra-lateral arm as reference could be a solution. However, anatomical differences between arteries of the arms could introduce an offset of PAT. Furthermore, when arterial stiffness decreases (e.g. after axillary blockade (AxB)) and pulse wave amplitude increases (vasodilation), the pulse waveform can change. The aim of this study was to investigate whether there is a difference between the PAT of both arms and to evaluate the effect of vasodilation after AxB on PAT. ECG and PPG was measured on both hands in 34 patients, starting 2 min before the injection of local anaesthetic of an AxB and continuing for a period of 30 min after block placement. PAT of the baseline and after AxB were calculated and compared. The mean-PAT of both arms were not significantly different for the three reference points. After AxB, PAT significantly increased for all reference points. PAT can be used for intra-subject comparison.

Background: It can take up to 30 min to determine whether or not axillary block has been successful. Pulse transit time (PTT) is the time between the R-wave on electrocardiography (ECG) and the arrival of the resulting pressure pulse wave in the fingertip measured with photoplethysmography. It provides information about arterial resistance. Axillary block affects vasomotor tone causing loss of sympathetic vasoconstriction resulting in an increased PTT. Early objective assessment of a block can improve efficacy of operating room time and minimize patient's fear of possible conversion to general anesthesia. This study explores whether PTT can objectively, reliably and quickly predict a successful axillary block., Methods: Forty patients undergoing hand surgery under axillary block were included. A three-lead ECG and photoplethysmographic sensors were placed on both index fingers. Measurements were made from 2 min before until 30 min after induction of the block or less if the patient was transferred for operation. Afterwards, PTT was calculated as the time between the R-wave on ECG and a reference point on the photoplethysmogram. To assess the change in PTT caused by the block, the PTT difference between the control and blocked arm was calculated. Sensitivity and specificity of PTT difference were calculated using receiver operating characteristic analysis., Results: In a successful block, the mean PTT difference significantly increased after 3 min by 12 (standard error of the mean 3.9) ms, sensitivity 87% and specificity 71% (area under the curve 0.87, P = 0.004)., Conclusions: PTT is a reliable, quick and objective method to assess whether axillary block is going to be successful or not., (© 2012 The Authors. Acta Anaesthesiologica Scandinavica © 2012 The Acta Anaesthesiologica Scandinavica Foundation.)