Walking reduces the post-void residual volume in parturients with epidural analgesia for labor: a randomized-controlled study

BACKGROUND

The post-void residual volume is higher among parturients who received epidural analgesia than those who received no or alternative analgesia.

METHODS

This prospective, randomized, controlled, non-blinded study was performed in a tertiary referral center labor suite. The post-void residual volume was measured by a transabdominal ultrasound following a voiding attempt. Healthy parturients with low-dose epidural analgesia in active labor were randomized either to walk to the toilet or to use a bedpan for voiding. The primary outcome measure (post-void residual volume in labor) was compared between the study groups.

RESULTS

The toilet group (n=34) and the bedpan group (n=28) demonstrated similar post-void residual volumes (212 +/- 100 vs. 168 +/- 93 ml, P=0.289). Twenty patients (59%) randomized to the toilet group were unable to walk and actually voided in a bedpan. A secondary analysis was performed analyzing the groups as treated. The post-void residual volume was significantly lower in the actual toilet group (n=14, 63 +/- 24 ml) vs. the bedpan group (n=48, 229 +/- 200 ml), P=0.0052. Thirteen (93%) women who walked to the toilet managed to void before the ultrasound measurement vs. 20/48 (42%) using the bedpan, P=0.001. Fewer women who managed to walk to the toilet required urinary bladder catheterization during the labor than women who used the bedpan (6/14, 43% vs. 36/48, 75%) P=0.028.

CONCLUSION

Women who were randomized to walk to the bathroom with epidural analgesia and were able to do so during labor had a significantly reduced post-void residual volume and a reduced requirement for urinary catheterization.

Automated, real-time calibration of the respiratory inductance plethysmograph and its application in newborn infants

Respiratory inductive plethysmography (RIP) is widely used in infants, children and adults. The technique is well accepted as it provides important qualitative information on the pattern of breathing, although its ability to record volume accurately was questioned due to calibration uncertainties. Existing calibration methods require two-position calibration, or patient cooperation in performing various breathing manoeuvres, or prolonged calibration paradigms. The disadvantages from calibration difficulties are even more pronounced in infants. We present a computer system that is capable of performing a single-posture, real-time RIP calibration during natural breathing and is suitable for use in newborns. The calibration algorithm is based on interactive, point-by-point calculations of maximal correlation between airflow at the mouth, Vao, and summed differentiated RIP signals. The quantities are calculated interactively at every sample point, and the process continues until stable results are reached and convergence criteria met. A graphic user interface was developed to assist in the rapid implementation and ease of use. Validation schemes were evaluated in 33 newborn infants against actual Vao. Calibration factors were obtained within 21 +/- 11 s with a mean correlation coefficient of 0.97 +/- 0.03. All RIP-derived values were similar to actual airflow signals, with error values ranging from 0.4 +/- 3.0% for respiratory rate to 1.8 +/- 7.3% for tidal volume. Calibration was found to be stable and reliable for up to 3.5 h and in changing sleep states. It is concluded that the new single-posture real-time RIP calibration system is safe and simple to use, and also quick, accurate and stable. The system was found to be suitable for use in newborns during natural breathing while asleep.

Preliminary experimental evaluation of an inverse source imaging procedure using a decoupled coil detector array in magnetic resonance imaging

Recently, we have discussed several of the aspects involved in the detector array concept in magnetic resonance imaging where an image is obtained by applying inverse source procedures to the data assembled by an array of coil detectors surrounding the object. In this work we describe an experimental setup, where a detector array was constructed of 9 coils, that gives a coarse resolution of 3 x 3 pixels. By measuring the induced current signals over this array of coils, a relationship is established between the set of signals and the structure of the body under investigation. Through matrix inversion, reconstruction of the original source from the detected signals is possible. In this preliminary experimental setup, we did not use an actual nuclear magnetic resonance signal. Instead, a miniature solenoid was used as a source, to simulate a precessing magnetic moment.

Wall shear stress distribution along the cusp of a tri-leaflet prosthetic valve

High levels of wall shear stress on the surface of valvular cusps can cause mechanical damage to the blood cells and the cusp surfaces. The shear stresses are also responsible for mechanical failure of prosthetic heart valves. Qualitative measurements of wall shear stress in the vicinity of the leaflets are thus essential for diagnosis of suspected complications and provide important information for the design and fabrication of bioprosthetic heart valves. For this purpose we measured the velocity distribution along the inside wall of the cusps of a tri-leaflet heart valve with a two colour laser Doppler anemometer system. The wall shear stresses on the cusp surface were computed and found to range from 80 to 120 N/m2 during the ejection phase. Wall shear stresses of up to 180 N/m2 were measured in loci of cusp flexure and the accelerated boundary layer. The results of this study show a correlation between the high shear stress loci and the clinically (animal) observed regions of cusp calcification.

The effect of pathologic venous valve on neighboring valves: fluid-structure interactions modeling

Understanding the hemodynamics surrounding the venous valve environment is of a great importance for prosthetic valves design. The present study aims to evaluate the effect of leaflets' stiffening process on the venous valve hemodynamics, valve's failure on the next proximal valve hemodynamics and valve's failure in a secondary daughter vein on the healthy valve hemodynamics in the main vein when both of these valves are distal to a venous junction. Fully coupled, two-way fluid-structure interaction computational models were developed and employed. The sinus pocket region experiences the lowest fluid shear stress, and the base region of the sinus side of the leaflet experiences the highest tissue stress. The leaflets' stiffening increases the tissue stress the valve is experiencing in a very low fluid shear region. A similar effect occurs with the proximal healthy valve as a consequence of the distal valve's failure and with the mother vein valve as a consequence of daughter vein valve's failure. Understanding the described mechanisms may be helpful for elucidating the venous valve stiffness-function relationship in nature, the reasons for a retrograde development of reflux and the relationship between venous valves located near venous junctions, and for designing better prosthetic valves and for improving their positioning.

Traumatic macroglossia: a life-threatening complication

OBJECTIVE

To describe the use of muscle relaxants and a bite raiser to avoid continued tongue trauma.

DESIGN

Case report.

SETTING

A tertiary general intensive care unit (ICU).

INTERVENTIONS

Muscle relaxation and bite raiser.

MAIN RESULTS

Muscle relaxation and a bite raiser were used in a 17-yr-old male with traumatic macroglossia, which allowed for rapid resolution of edema and prevented additional trauma to the tongue.

CONCLUSION

Early use of a bite raiser together with muscle relaxants allows for more rapid solution of edema and prevention of additional trauma to the tongue in patients with traumatic macroglossia.

Brightness contrast-contrast induction model predicts assimilation and inverted assimilation effects

In classical assimilation effects, intermediate luminance patches appear lighter when their immediate surround is comprised of white patches and appear darker when their immediate surround is comprised of dark patches. With patches either darker or lighter than both inducing patches, the direction of the brightness effect is reversed and termed as "inverted assimilation effect." Several explanations and models have been suggested, some are relevant to specific stimulus geometry, anchoring theory, and models that involve high level cortical processing (such as scission, etc.). None of these studies predicted the various types of assimilation effects and their inverted effects. We suggest here a compound brightness model, which is based on contrast-contrast induction (second-order adaptation mechanism). The suggested model predicts the various types of brightness assimilation effects and their inverted effects. The model is composed of three main stages: (1) composing post-retinal second-order opponent receptive fields, (2) calculations of local and remote contrast, and (3) adaptation of the second-order (contrast-contrast induction). We also utilize a variation of the Jacobi iteration process to enable elegant edge integration in order to evaluate the model is performance.

Adhesion molecule expression by osteogenic cells cultured on various biodegradable scaffolds

Design of tissue-engineered cell-loaded device involves cells seeding onto scaffolds in vitro, allowing them to settle and grow before in vivo transplantation. Interaction between scaffold and cells is important in the development of desired tissues. The present study aimed to investigate the effect of cell-polymer interactions on cell morphology and expression of surface markers of osteogenic MBA-15 cells cultured on various bioresorbable polymers. In this study, we used various polymers: poly(L-lactic acid) (PLLA), poly(DL-lactic acid) (PDLLA), poly(L-lactic-glycolic acid) (PLGA), and poly(DL-lactide-glycolide acid) PDLGA1 and PDLGA2. Expression of integrinalpha-M (CD11b), selectin-E (CD62E), and PECAM-1 (CD31), important in cell-cell and cell-matrix interactions, were quantified by flow-cytometry analysis. Cells grown on PDLGA1 films demonstrated fivefold increase in CD62E expression and two-folds increase in CD11b expression. None of the polymers affected the levels of CD31. Identified differential effect of polymers on the expression of cell-adhesion molecules by osteoprogenitors in vitro might help to choose optimal parameters for successful engraftment of cell-loaded constructs.

Haemodynamics of coronary artery-saphenous vein bypass

The velocity distribution of a suspension of red blood cell ghosts in an idealized model of the coronary artery-saphenous vein bypass has been investigated with the aid of laser Doppler anemometry. Pulsatile flow simulated pressure variations in the ascending aorta and ghost cell velocities were determined by the Doppler shift of scattered laser light. Using four different model bypasses it was demonstrated that turbulent flow at the graft-coronary intersection can be delayed by decreasing the discontinuity in diameter between the bypass vein and coronary artery, and also by reducing the bypass vein and host coronary artery intersection angle.

Pitfalls to avoid in the medical management of mass casualty incidents following terrorist bombings: the hospital perspective

BACKGROUND

The unique patterns of injury following explosions together with the involvement of numerous physicians, most of whom are not experienced in trauma, may create problems in the medical management of mass casualty incidents.

METHODS

Four hundred patient files admitted in 19 mass casualty events following bombing incidents were reviewed and possible areas which could impact survival were defined.

RESULTS

Forty-nine (9.3 %) patients had an Injury Severity Score ≥16. Of 205 patients in whom triage decisions were available, 5 of 25 severely injured patients were undertriaged by the triage officers at the door of the hospital. Following primary evaluation inside the emergency department critical injuries in two patients were missed due to distracting, less serious injuries. Of 68 (16.1 %) patients who were operated, 28 were in need of either immediate, urgent or high-priority operations. Except for neurosurgical cases which needed to be transferred to other hospitals, there was no delay in surgery. One patient underwent negative laparotomy. There were 15 in-hospital deaths, 6 of which were deemed as either anticipated or unanticipated mortality with possibility for improvement.

CONCLUSION

Medical management should be evaluated following MCIs as this may illustrate possible problems which many need to be addressed in contingency planning.

Calculation of the mutual induction between coplanar circular surface coils in magnetic resonance imaging

The induced current in a coil due to the presence of alternating currents in an adjacent coil is calculated here for a case of two similar and coplanar, circular coils. By using an overlapping configuration, the mutual inductance is nullified as is predicted theoretically and confirmed experimentally.

Mechanical Compression Effects on the Secretion of vWF and IL-8 by Cultured Human Vein Endothelium

Short peripheral catheters are ubiquitous in today's healthcare environment enabling effective delivery of fluids and medications directly into a patient's vasculature. However, complications related to their use, such as short peripheral catheter thrombophlebitis (SPCT), affect up to 80% of hospitalized patients. While indwelling within the vein, the catheters exert prolonged constant pressure upon the endothelium which can trigger inflammation processes. We have developed and studied an in-vitro model of cultured endothelial cells subjected to mechanical compression of modular self-designed weights, and explored their inflammatory response by quantification of two key biomarkers- vWF and IL-8. Evaluation was performed by ELISA immunoassay and processing of vWF-labeled immunofluorescence images. We found that application of weights correspond to 272 Pa yielded increased release of vWF and IL-8 up to 150% and 250% respectively, comparing to the exertion of 136 Pa. Analyses of the immunofluorescence images revealed significantly longer and more extracellular vWF-strings as well as higher intensity stained-pixels in cells exposed to elevated pressures. The release of both factors found to be significantly dependent on the extent of the exerted pressure. The research shed a light on the relationship between induced mechanical compression and the pathogenesis of SPCT. Minimizing, let alone eliminating the contact between the catheter and the vein wall will mitigate the pressure acting on the endothelium, thereby reducing the secretion of inflammatory factors and lessen the incidence of SPCT.

Preparedness for anthrax attack: the effect of knowledge on the willingness to treat patients

Little is known about the factors that may impact on the willingness of physicians and nurses to treat patients during a bioterrorism attack. This survey was conducted among 76 randomly selected nurses and physicians in the emergency rooms of three public hospitals in order to analyse the relationship between knowledge, profession and the willingness to treat anthrax. The study finds that the willingness of physicians and nurses to come to work is 50% greater among the group with the highest knowledge about anthrax (P < 0.0001). Within that group, the willingness to treat patients suspected of being infected with anthrax was 37% greater (P < 0.0001) and the willingness to treat patients diagnosed with anthrax was 28% greater (P = 0.004) than in the other groups. These results imply that enhancement of knowledge among health care workers may improve their willingness to come to work and treat patients infected with anthrax during a bioterrorism attack.

Modelling catheter-vein biomechanical interactions during an intravenous procedure

A reliable intravenous (IV) access into the upper extremity veins requires the insertion of a temporary short peripheral catheter (SPC). This so common procedure is, however, associated with a risk of developing short peripheral catheter thrombophlebitis (SPCT) which causes distress and potentially prolongs patient hospitalization. We have developed and studied a biomechanical SPC-vein computational model during an IV procedure, and explored the biomechanical effects of repeated IV episodes on onset and reoccurrences of SPCT. The model was used to determine the effects of different insertion techniques as well as inter-patient biological variability on the catheter-vein wall contact pressures and wall deformations. We found that the maximal pressure exerted upon the vein wall was inhomogeneously distributed, and that the bending region was exposed to significantly greater pressures and deformations. The maximal exerted contact pressure on the inner vein's wall was 2938 Pa. The maximal extent of the SPC penetration into the vein wall reached 3.6 μm, which corresponds to approximately 100% of the average height of the inner layer, suggesting local squashing of endothelial cells at the contact site. The modelling describes a potential biomechanical damage pathway that can explain the reoccurrence of SPCT.

Effects of contact-induced membrane stiffening on platelet adhesion

The adhesion of platelets plays an essential role in thrombogenesis. Adhesion occurs at sites called focal adhesions (FA), where cell-membrane receptors bind specifically to substrate proteins and couple to each other and to the cytoskeleton via various cellular proteins. The resulting molecular structure suggests that the cortex stiffens at the FA, which likely affects platelet adhesion. This hypothesis is explored by structural analysis and parametric investigation. The cortex is modeled as a shell anchored to the substrate by adhesion forces and subjected to a detachment force. Equilibrium considerations result in a non-linear, two-point boundary value problem that is solved numerically. The results show that cortex stiffening significantly influences the force required for detachment as well as the cell-membrane internal stresses. The magnitude of these effects depends on the ratio of adhesion-to-bending energies and on the inclination of the detachment force. Because the cortex stiffening depends on cellular events, these results suggest a possible mechanism by which platelets can control their adhesion and protect themselves from damage.

Reverse engineering of the spindle assembly checkpoint

The Spindle Assembly Checkpoint (SAC) is an intracellular mechanism that ensures proper chromosome segregation. By inhibiting Cdc20, a co-factor of the Anaphase Promoting Complex (APC), the checkpoint arrests the cell cycle until all chromosomes are properly attached to the mitotic spindle. Inhibition of Cdc20 is mediated by a conserved network of interacting proteins. The individual functions of these proteins are well characterized, but understanding of their integrated function is still rudimentary. We here describe our attempts to reverse-engineer the SAC network based on gene deletion phenotypes. We begun by formulating a general model of the SAC which enables us to predict the rate of chromosomal missegregation for any putative set of interactions between the SAC proteins. Next the missegregation rates of seven yeast strains are measured in response to the deletion of one or two checkpoint proteins. Finally, we searched for the set of interactions that correctly predicted the observed missegregation rates of all deletion mutants. Remarkably, although based on only seven phenotypes, the consistent network we obtained successfully reproduces many of the known properties of the SAC. Further insights provided by our analysis are discussed.

Shear Stress Related Blood Damage along the Cusp of a Tri-Leaflet Prosthetic Valve

Blood flowing through a prosthetic heart valve can be damaged by flow-induced shear forces. Fluid dynamics variables and geometric factors play an important role in the evaluation of shear-stress-related blood damage. Central-flow prosthetic valves have been considered as an optimal replacement for mechanical and biological valves. Recently it was shown that shear stress distribution along the surface of a polyurethane cusp reaches values that can damage the blood elements. A mathematical model correlating the effects of shear stresses on blood corpuscles with clinical findings was employed in vitro. The model can be applied to the effects of blood-surface interaction and is of clinical relevance

The Cardiocoil Stent-Artery Interaction

An analytical approach for the mechanical interaction of the self-expanding Cardiocoil stent with the stenosed artery is presented. The damage factor as the contact stress at the stent-artery interface is determined. The stent is considered as an elastic helical rod having a nonlinear pressure-displacement dependence, while the artery is modeled by an elastic cylindrical shell. An influence of a moderate relative thickness of the shell is estimated. The equations for both the stent and the artery are presented in the stent-associated helical coordinates. The computational efficiency of the model enabled to carry out a parametric study of the damage factor. Comparative examinations are conducted for the stents made of the helical rods with circular and rectangular cross sections. It was found, in particular, that, under same other conditions, the damage factor for the stent with a circular cross section may be two times larger than that for a rectangular one.

The Effect of Colloid Osmotic Pressure on the Survival of Sheep following Cardiac Surgery

The occurrence of late complications in implanted cardiac prosthetic valves has emphasized the need for the development of an animal model in which these complications are reproducible. Sheep constitute an excellent model for chronical and pathological studies of prosthetic devices. In our experience, survival of sheep following implantation of prosthetic valves is closely related to postoperative serum colloid osmotic pressure (C.O.P.). The normal range as measured in 28 healthy sheep was 16.67 ± 0.55 mm Hg. A protocol was developed to maintain the colloid hydrostatic pressure gradient (C.H.P.G.) as close as possible to the normal physiological range, and to delay the extubation until the C.O.P. was within this range, and the C.H.P.G. > 7mm Hg. Using the above protocol, a new tri-leaflet Polyurethane valve was inserted into eight, five to seven month old sheep in place of the mitral and tricuspidal valves. One hour after terminating the extacorporeal circuit, the C.O.P. was measured at 13.10 ± 0.96; but within five to six hours, it rose to 17.1 ± 1.1. During the same period, the C.H.P.G. increased from 3.02 ± 0.96 to 7.6 ± 0.50 mm Hg. The postoperative period was uneventful, and all animals survived. We have thus concluded that the routine measurement and monitoring of C.O.P. constitutes a guide of great clinical importance.

Lopinavir/ritonavir for the treatment of SARS, MERS and COVID-19: a systematic review

OBJECTIVE

Lopinavir/ritonavir has been used for the treatment of Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS) coronavirus infections. It has been suggested that, based on this experience, this drug should also be studied in SARS-CoV2 infection.

MATERIALS AND METHODS

We performed a systematic review of the literature regarding the use of lopinavir/ritonavir for the treatment of these three infections. We systematically searched the PubMed database from inception to April 30th, 2020, to identify in-vitro and animal studies and any reports of human use of lopinavir/ritonavir for the treatment of SARS, MERS and COVID-19. We also searched the Clinicatrial.gov to identify ongoing trials.

RESULTS

Five in-vitro studies evaluated the effect of lopinavir/ritonavir in SARS. Three additional in-vitro studies reported the EC50 of the antiviral activity of lopinavir/ritonavir in MERS. We identified no in vitro studies evaluating the effect of lopinavir/ritonavir on the novel coronavirus. Two retrospective matched-cohort studies reported the use of lopinavir/ritonavir in combination with ribavirin for SARS patients. Three case reports and one retrospective study described the use of lopinavir/ritonavir in MERS. Twenty-two papers describe the use of lopinavir/ritonavir in adult patients with COVID-19.

CONCLUSIONS

The existing literature does not suffice for assessing whether Lopinavir/ritonavir has any benefit in SARS, MERS or COVID-19.

Association between intra-operative cardiac arrest and country Human Development Index status: a systematic review with meta-regression analysis and meta-analysis of observational studies. Anaesthesia 2021;76:1259-1273. [PMID: 33512708 DOI: 10.1111/anae.15374]

Intra-operative cardiac arrests differ from most in-hospital cardiac arrests because they reflect not only the patient's condition but also the quality of surgery and anaesthesia care provided. We assessed the relationship between intra-operative cardiac arrest rates and country Human Development Index (HDI), and the changes occurring in these rates over time. We searched PubMed, EMBASE, Scopus, LILACS, Web of Science, CINAHL and SciELO from inception to 29 January 2020. For the global population, rates of intra-operative cardiac arrest and baseline ASA physical status were extracted. Intra-operative cardiac arrest rates were analysed by time, country HDI status and ASA physical status using meta-regression analysis. Proportional meta-analysis was performed to compare intra-operative cardiac arrest rates and ASA physical status in low- vs. high-HDI countries and in two time periods. Eighty-two studies from 25 countries with more than 29 million anaesthetic procedures were included. Intra-operative cardiac arrest rates were inversely correlated with country HDI (p = 0.0001); they decreased over time only in high-HDI countries (p = 0.040) and increased with increasing ASA physical status (p < 0.0001). Baseline ASA physical status did not change in high-HDI countries (p = 0.106), while it decreased over time in low-HDI countries (p = 0.040). In high-HDI countries, intra-operative cardiac arrest rates (per 10,000 anaesthetic procedures) decreased from 9.59 (95%CI 6.59-13.16) pre-1990 to 5.17 (95%CI 4.42-5.97) in 1990-2020 (p = 0.013). During the same time periods, no improvement was observed in the intra-operative cardiac arrest rates in low-HDI countries (p = 0.498). Odds ratios of intra-operative cardiac arrest rates in ASA 3-5 patients were 8.48 (95%CI 1.67-42.99) times higher in low-HDI countries than in high-HDI countries (p = 0.0098). Intra-operative cardiac arrest rates are related to country-HDI and decreased over time only in high-HDI countries. The widening gap in these rates between low- and high-HDI countries needs to be addressed globally.