Publications by authors named "Surapong Chatpun"

22 Publications

  • Page 1 of 1

Carpal Tunnel Surgery Using a Wireless Endoscopic Visualization Instrument: A Cadaveric Study.

J Hand Surg Asian Pac Vol 2021 Sep;26(3):359-363

Institute of Biomedical Engineering, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand.

Endoscopic carpal tunnel release is a common treatment for moderate to severe carpal tunnel syndrome. Recently there have been various new techniques which offer improved accuracy and decreased recovery time. In this study, orthopedic surgeons and biomedical engineers from the Faculty of Medicine and Faculty of Engineering, Prince of Songkla University, designed a wireless endoscopic carpal tunnel release with a single portal technique and tested the efficacy and safety of the new technique in a cadaveric study. Ten fresh cadaveric forearms were used in the study. The surgical technique began with a surgical incision 15-20 mm above the wrist crease on the line between the middle finger and ring finger. The palmaris longus aponeurosis was retracted by Senn retractors. A visual enhancer was inserted to improve the internal visual field in order to see the flexor retinaculum clearly. The flexor retinaculum was cut distally to create an entry and the flexor retinaculum was cut by the scalpel. The flexor retinaculum length was observed until the release was completed. The median nerve was observed. Each flexor retinaculum was cut completely. All of the median nerves were carefully observed during the operation and none were injured. This technique showed the effectiveness and safety of minimally invasive carpal tunnel surgery. The study found that the new device using this technique is effective for carpal tunnel syndrome (CTS) surgery in terms of minimally invasive endoscopic carpal tunnel surgery.
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http://dx.doi.org/10.1142/S2424835521500326DOI Listing
September 2021

Optimization of the Rubber Formulation for Footwear Applications from the Response Surface Method.

Polymers (Basel) 2020 Sep 7;12(9). Epub 2020 Sep 7.

Department of Mechanical Engineering, Faculty of Engineering, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand.

Impact force remains the primary cause of foot injury and general discomfort with regard to footwear. The footwear industry traditionally relies on modified elastomers (including natural rubber) whose properties can be physically adjusted by varying the constituents in the rubber formulations. This work aims to investigate the effect of filler/plasticizer fractions on shock attenuation of natural rubber soles. The statistical response surface method (RSM) was used to optimize the loading of natural rubber, fillers (carbon black and china clay) and a plasticizer (paraffinic oil). A novel predictive equation addressing the effects of additives on the physical and mechanical properties of the shoe sole was successfully created using the RSM. Our results demonstrate how the concentrations of these components regulate final properties, such as impact force absorption and hardness, in the commercial manufacture of shoe soles. While a higher loading level of plasticizer promotes reductions in hardness and impact force, as well as energy dissipation, in these modified elastomers, these properties were improved by increasing the filler content.
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http://dx.doi.org/10.3390/polym12092032DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7563865PMC
September 2020

Changes in neural network connectivity in mice brain following exposures to palatable food.

Neurosci Lett 2020 01 16;714:134542. Epub 2019 Oct 16.

Department of Physiology, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand; Research Unit for EEG Biomarkers of Neuronal diseases, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand.

Previously, satiated animals or human subjects can still be motivated to eat by palatable food-associated cues. However, neural circuitries of hedonic hunger have not been well investigated. This study identified neural network connectivities between major brain areas in response to chocolate-associated cues following repeated exposures to chocolate. Adult male Swiss albino ICR mice were anesthetized and implanted with intracranial electrodes in the lateral hypothalamus (LHa), nucleus accumbens (NAc), olfactory bulb (OB) and hippocampus (HP) for local field potential (LFP) recording. LFP oscillations were recorded before and after repeated exposures to chocolate for chocolate experienced group whereas control group was not exposed to chocolate. On testing days, satiated animals were individually put into a place preference-like apparatus with two opposite chambers of chocolate and normal chow scent cues, separately. The results showed that chocolate experienced group significantly increased time spent in chocolate chamber whereas control group did not. One-way ANOVA revealed significant influence of chocolate sessions on LFP spectral powers of multiple frequencies in the LHa (delta, low gamma and high gamma) and NAc (high gamma). Moreover, coherence function analyses also highlighted significant increases in LHa-NAc and LHa-OB, and decrease in LHa-HP coherent activities in response to olfactory cues of chocolate. This study demonstrated modifications of neural network connectivity and associative learning following multiple exposures to palatable food. These findings might explain why energy homeostatic hunger is overridden by hedonic hunger.
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http://dx.doi.org/10.1016/j.neulet.2019.134542DOI Listing
January 2020

The insole materials influence the plantar pressure distributions in diabetic foot with neuropathy during different walking activities.

Gait Posture 2019 10 5;74:154-161. Epub 2019 Sep 5.

Institute of Biomedical Engineering, Faculty of Medicine, Prince of Songkla University, Hatyai, Songkhla, Thailand. Electronic address:

Background: Abnormal peak plantar pressure in neuropathic diabetic foot during walking activities is well managed through the use of appropriate design and material selection for the fabrication of custom made insoles (CMI). The redistribution of plantar pressure is possible by selecting an appropriate material for the fabrication of CMI. The walking activities may alter the plantar pressure distribution; which may differ while using CMI with different materials.

Objective: The objective of the study was to evaluate the effectiveness of CMI's materials on plantar pressure distribution during different walking activities, in diabetic feet with neuropathy.

Methods: The study was conducted on sixteen diabetic neuropathic subjects. The subjects were provided with two types of CMI; CMI-A (Plastazote® and microcellular rubber) and CMI-B (Multifoam, Plastazote® and microcellular rubber). Maximum peak plantar pressure and plantar pressure distribution were determined by Pedar-X® sensor insole during level walking, ramp walking and stair walking.

Results: The CMI-B lessened the maximum peak plantar pressure from the forefoot throughout the walking activities compared to CMI-A. The contact area was observed as lower using CMI-A compared to CMI-B, while performing walking activities.

Conclusion: CMI-B, with multifoam as an additional top layer, provided more effective peak plantar pressure reduction at forefoot and it had better plantar pressure distribution compared to CMI-A during level walking and ramp ascending in diabetic foot with neuropathy.
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http://dx.doi.org/10.1016/j.gaitpost.2019.08.023DOI Listing
October 2019

Beta and gamma synchronous oscillations in neural network activity in mice-induced by food deprivation.

Neurosci Lett 2019 09 22;709:134398. Epub 2019 Jul 22.

Department of Physiology, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand; Research Unit for EEG Biomarkers of Neuronal diseases, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand. Electronic address:

Food deprivation is known to trigger hunger sensation and motivation to eat for energy replenishing. However, brain mechanisms associated with hunger and neural circuitries that mediate hunger driven responses remained to be investigated. To understand neural signaling of hunger, local field potentials (LFPs) in the lateral hypothalamus (LHa), nucleus accumbens (NAc), dorsal hippocampus (HP) and olfactory bulb (OB) and their interconnectivities were studied in freely moving adult male Albino mice during 18-20 h food deprivation and fed periods. Raw LFP signals were recorded and analyzed for mean values of spectral frequency power and coherence values. One-way repeated measures ANOVA revealed significant increases in spectral powers of beta and gamma frequency ranges induced by food deprivation in the LHa, HP, NAc but not OB. No change of spectral power in these brain regions was induced by food feeding. The analyses of coherent activity between brain regions also deliniated some distributed neural network activities correlated with hunger. In particular, coherent function indicated the increased beta and gamma phase synchrony between the pairs of LHa-HP and NAc-OB regions, and decreased gamma synchrony between the pairs of LHa-NAc and NAc-HP induced by food deprivation. It was found that plasma glucose level, locomotor count, travelled distance and time spent on moving were not altered by food deprivation. These results suggest that changes in LFP hallmarks in these brain regions were associated with hunger driven by negative energy balance.
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http://dx.doi.org/10.1016/j.neulet.2019.134398DOI Listing
September 2019

Correction to: Computational study on hemodynamic changes in patient-specific proximal neck angulation of abdominal aortic aneurysm with time-varying velocity.

Australas Phys Eng Sci Med 2019 03;42(1):191

Institute of Biomedical Engineering, Faculty of Medicine, Prince of Songkla University, 6th floor, 100-year Building, Hatyai, Songkhla, 90110, Thailand.

The name of the third author was incorrect in the initial online publication. The original article has been corrected.
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http://dx.doi.org/10.1007/s13246-019-00741-wDOI Listing
March 2019

Computational study on hemodynamic changes in patient-specific proximal neck angulation of abdominal aortic aneurysm with time-varying velocity.

Australas Phys Eng Sci Med 2019 Mar 14;42(1):181-190. Epub 2019 Feb 14.

Institute of Biomedical Engineering, Faculty of Medicine, Prince of Songkla University, 6th floor, 100-year Building, Hatyai, Songkhla, 90110, Thailand.

Aneurysms are considered as a critical cardiovascular disease worldwide when they rupture. The clinical understanding of geometrical impact on the flow behaviour and biomechanics of abdominal aortic aneurysm (AAA) is progressively developing. Proximal neck angulations of AAAs are believed to influence the hemodynamic changes and wall shear stress (WSS) within AAAs. Our aim was to perform pulsatile simulations using computational fluid dynamics (CFD) for patient-specific geometry to investigate the influence of severe angular (≥ 60°) neck on AAA's hemodynamic and wall shear stress. The patient's geometrical characteristics were obtained from a computed tomography images database of AAA patients. The AAA geometry was reconstructed using Mimics software. In computational method, blood was assumed Newtonian fluid and an inlet varying velocity waveform in a cardiac cycle was assigned. The CFD study was performed with ANSYS software. The results of flow behaviours indicated that the blood flow through severe bending of angular neck leads to high turbulence and asymmetry of flows within the aneurysm sac resulting in blood recirculation. The high wall shear stress (WSS) occurred near the AAA neck and on surface of aneurysm sac. This study explained and showed flow behaviours and WSS progression within high angular neck AAA and risk prediction of abdominal aorta rupture. We expect that the visualization of blood flow and hemodynamic changes resulted from CFD simulation could be as an extra tool to assist clinicians during a decision making when estimation the risks of interventional procedures.
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http://dx.doi.org/10.1007/s13246-019-00728-7DOI Listing
March 2019

Effect of total-contact orthosis on medial longitudinal arch and lower extremities in flexible flatfoot subjects during walking.

Prosthet Orthot Int 2017 Dec 19;41(6):579-586. Epub 2017 Feb 19.

1 Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand.

Background: Total-contact orthosis (TCO) is one kind of foot orthosis (FO) that is used to adjust biomechanics in flexible flatfoot.

Objective: To determine the effects of a TCO on the MLA moment, MLA deformation angle and lower limb biomechanics.

Study Design: Cross-sectional study.

Methods: Seven-flatfoot and thirteen-normal foot subjects were recruited by footprint and radiographs. The biomechanics of subjects with normal foot (NF), flatfoot with shoe only (FWOT) and flatfoot with TCO (FWT) were collected in a 3D motion analysis laboratory and force plates. The MLA and lower limb biomechanics in each condition during specific sub-phases of stance were analyzed.

Results: The NF had larger MLA eversion moment after shod walking ( p = 0.001). The FWT condition compared with the FWOT condition had a significantly larger peak MLA upward moment ( p = 0.035) during pre-swing, larger peak knee external rotation angle ( p = 0.040) during mid stance, smaller peak knee extension moment during terminal stance ( p = 0.035) and a larger ground reaction force in the anterior-posterior direction during early stance ( p < 0.05).

Conclusion: Our study found positive effects from the customized TCOs which included an increased TCO angle that led to a decreased peak MLA moment in the frontal plane in flexible flatfoot subjects during walking. Clinical relevance Lower limb biomechanics is different from normal in subjects with flexible flatfoot. The design of a TCO affects MLA, ankle and knee biomechanics and may be used to clinically correct biomechanical changes in flexible flatfoot.
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http://dx.doi.org/10.1177/0309364617691621DOI Listing
December 2017

Hippocampal CA1 local field potential oscillations induced by olfactory cue of liked food.

Neurobiol Learn Mem 2017 Jul 19;142(Pt B):173-181. Epub 2017 May 19.

Department of Physiology, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand; Brain Signal Research Unit, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand. Electronic address:

Eating motivation is induced not only by negative energy balance but also food related cues. However, neural processing for acquisition of learned food preference remains to be established. This study aimed to identify hippocampal neural signaling in response to olfactory cue (chocolate scent) after completion of repetitive chocolate sessions. Male Swiss albino mice implanted with intracranial electrode into the hippocampus were used for local field potential (LFP) recording. Animals were given chocolate sessions (a piece of 2g chocolate per each mouse to eat on day 1, 3, 5 and 7). Hippocampal CA1 LFP signals and exploratory behavior of animals receiving chocolate scent were analyzed before and after chocolate sessions. The experiment was performed in a place preference-like apparatus with the zones of normal food pellet and chocolate (both kept in a small perforated cup for smell dispersion) at the opposite ends. Following chocolate sessions, time spent in a chocolate zone and CA1 LFP patterns were analyzed in comparison to control levels. Two-way ANOVA revealed significant increase in time spent seeking for chocolate. Frequency analysis of LFP power spectra revealed significant increases in delta and theta powers. Phase-amplitude analysis showed significant increase in maximal modulation index and decrease in frequency for phase of theta-high gamma coupling. Taken together, neural signaling in the hippocampus was sensitive to chocolate olfactory cue that might underlie learning process in response to repeated chocolate consumptions that primed intense food approaching behavior. Ultimately, these LFP patterns might reflect motivation to eat and predict feeding probability.
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http://dx.doi.org/10.1016/j.nlm.2017.05.011DOI Listing
July 2017

Effectiveness of Total Contact Orthosis for Plantar Pressure Redistribution in Neuropathic Diabetic Patients During Different Walking Activities.

Foot Ankle Int 2017 Aug 29;38(8):901-908. Epub 2017 Apr 29.

1 Institute of Biomedical Engineering, Faculty of Medicine, Prince of Songkla University, Hat Yai, Songkhla, Thailand.

Background: Using a total contact orthosis (TCO) is an effective method to offload in diabetic patients with foot neuropathy. However, the redistribution of peak plantar pressure is mostly observed during level walking, which may differ from other walking activities. The aim of this study was to investigate the plantar pressure from 4 regions of the foot during different walking activities (level walking, ramp ascending, ramp descending, stair ascending, and stair descending) in neuropathic diabetic patients with and without a TCO.

Methods: Sixteen neuropathic diabetic patients aged 40 to 60 years with calluses and hallux valgus were included in this study and were provided with TCOs made up of multifoam, Plastazote, and microcellular rubber. The plantar pressure and contact area with the TCO and without the TCO were recorded using the Pedar X system during different walking activities.

Results: A significant reduction of plantar pressure during different walking activities at the toes and forefoot regions was observed while walking with the TCO compared with walking without the TCO (control condition). Plantar pressure increased at the midfoot region when walking with the TCO, and no significant difference was observed at the hindfoot region between the control and TCO conditions. Furthermore, maximum contact area was observed during level walking with the TCO compared with other walking activities.

Conclusion: The TCO significantly reduced and redistributed the peak plantar pressure from the sites where the ulceration rate is higher at the toes and forefoot compared with the other regions of the foot.

Level Of Evidence: Therapeutic level II, lesser quality randomized controlled trial.
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http://dx.doi.org/10.1177/1071100717704427DOI Listing
August 2017

Characterization and physiological effect of tapioca maltodextrin colloid plasma expander in hemorrhagic shock and resuscitation model.

J Mater Sci Mater Med 2016 May 25;27(5):98. Epub 2016 Mar 25.

National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Klong Luang, Pathum Thani, 12120, Thailand.

Plasma expanders (PEs) are administered fluids to replace blood volume when massive blood loss has occured. Maltodextrin from tapioca starch was selected as a study candidate to prepare a colloid PE due to an uncomplicated production process. The formulations of mixture between tapioca maltodextrin and 0.9 % sodium chloride solution were prepared and then characterized. This was to investigate the effects of a dextrose equivalent (DE) and the concentration on the physical properties. Storage stability of each formulation was also determined and compared with clinically used PE [6 % hydroxyethyl starch (HES), 130/0.4]. The effects on the circulatory system in hamsters with hemorrhagic shock and resuscitation using prepared PE were also investigated. The results showed that low DE value led to high retrogradation, turbidity and viscosity but low colloid osmotic pressure and poor solubility. Among the prepared solutions, tapioca maltodextrin with DE6 at 10 % w/v concentration had comparable properties with 6 % HES 130/0.4. Animals resuscitated with 10 % DE6 PE had improved mean arterial blood pressure similar to those resuscitated with 6 % HES 130/0.4. However, several parameters in animals resuscitated with 10 % DE6 PE were lower than those resuscitated with 6 % HES 130/0.4, i.e., heart rate, functional capillary density. Therefore, if using tapioca maltodextrin for PE, some properties have to be considered and efficiently optimized.
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http://dx.doi.org/10.1007/s10856-016-5708-3DOI Listing
May 2016

Medial longitudinal arch biomechanics evaluation during gait in subjects with flexible flatfoot.

Acta Bioeng Biomech 2015 ;17(4):121-30

Institute of Biomedical Engineering, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand.

Purpose: Medial longitudinal arch (MLA) strengthening has been considered an important part of successful flatfoot treatment. But, to date, the biomechanical loading behavior of the medial arch in flatfoot has not been evaluated. This study aimed to evaluate the MLA moment, MLA deformation angle, foot kinematics and ground reaction forces (GRF) in both normal foot and flatfoot groups.

Methods: Each participant's foot was classified according to arch type using foot prints and radiographs. Twenty-eight non-obese adults (13 flatfeet and 15 normal feet) were involved. The biomechanics data were collected in a 3D motion analysis laboratory. The MLA biomechanics were calculated. Hindfoot and forefoot kinematics were also analyzed.

Results: The flatfoot group had a significantly greater peak eversion MLA moment (p = 0.005) and a smaller peak MLA deformation angle (p < 0.05) during specific subphases. The peak of hindfoot plantarflexion (p < 0.05) and internal rotation (p < 0.05) and the peak of forefoot abduction ( p < 0.05) in the specific subphases were greater in the flatfoot group. The flatfoot group also had significantly smaller peak vertical GRF ( p < 0.05) during late stance and larger peak medial GRF (p < 0.05) during mid stance.

Conclusions: This study found a significantly greater eversion deforming force acting at the MLA structure, greater hindfoot and forefoot motion, less MLA flexibility and abnormal GRF in a flatfoot group during walking, which reflected the deficit of foot function in a flatfoot group.
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October 2016

Gamma wave oscillation and synchronized neural signaling between the lateral hypothalamus and the hippocampus in response to hunger.

J Physiol Sci 2015 Jul;65(Suppl 2):S17-S22

Department of Physiology, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand.

The lateral hypothalamus plays an important role in homeostasis. It is sensitive to negative energy balance and believed to interact with other brain regions to mediate food seeking behavior. However, no neural signaling of hunger in the lateral hypothalamus has been studied. Male Swiss albino mice implanted with intracranial electrodes into the lateral hypothalamus and the hippocampus were randomly treated with drinking water for control condition, 18-20 h deprivation of food for hunger condition, and fluid food for satiety condition. Therefore, local field potential (LFP) and locomotor activity of animals were simultaneously recorded. One way ANOVA with Tukey's post hoc test was used for statistical analysis. Frequency analysis of LFP revealed that food deprivation significantly increased the power of gamma oscillation (65-95 Hz) in the lateral hypothalamus and the hippocampus. However, satiety did not change the oscillation in these regions. Moreover, no significant difference among groups was observed for locomotor count and speed. The analysis of coherence values between neural signaling of these two brain areas also confirmed significant increase within a frequency range of 61-92 Hz for hunger. No change in coherence value was induced by satiety. In summary, this study demonstrated neural signaling of the lateral hypothalamus in response to hunger with differential power spectrum of LFP and the interplay with the hippocampus. The data may suggest critical roles of the lateral hypothalamus in detection of negative energy balance and coordination of other higher functions for food related learning or behaviors through the connectivity with the hippocampus.
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http://dx.doi.org/10.1007/BF03405851DOI Listing
July 2015

Characterization of in utero valproic acid mouse model of autism by local field potential in the hippocampus and the olfactory bulb.

Neurosci Res 2015 Sep 2;98:28-34. Epub 2015 May 2.

Department of Physiology, Faculty of Science, Prince of Songkla University (PSU), Hat Yai, Songkhla 90112, Thailand. Electronic address:

Valproic acid (VPA) mouse model of autism spectrum disorder (ASD) has been characterized mostly by impaired ultrasonic vocalization, poor sociability and increased repetitive self-grooming behavior. However, its neural signaling remained unknown. This study investigated the local field potentials (LFPs) in the dorsal hippocampal CA1 and the olfactory bulb while animals exploring a novel open field. VPA was administered at gestational day 13. The results demonstrated three core features of ASD in male offspring. However, there was no difference in Y-maze performance and locomotor activity. Analysis of hippocampal LFP power revealed significantly increased slow wave (1-4 Hz) and high gamma (80-140 Hz) oscillations and decreased theta (4-12 Hz) activity in VPA mice. In the olfactory bulb, VPA animals showed greater slow wave (1-4 Hz) and beta (25-40 Hz) activity and lower activity of low gamma (55-80 Hz) wave. Regression analysis revealed positive correlations between hippocampal theta power and locomotor speed for both control and VPA-exposed mice. There was no significant difference between groups for modulation index of theta (4-12 Hz) phase modulated gamma (30-200 Hz) amplitude. These findings characterized VPA mouse model with LFP oscillations that might provide better understanding of neural processing in ASD.
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http://dx.doi.org/10.1016/j.neures.2015.04.006DOI Listing
September 2015

Physicochemical properties and responses in microcirculation of native tapioca starch-based plasma expander.

J Biomed Mater Res B Appl Biomater 2016 Feb 17;104(2):395-401. Epub 2015 Apr 17.

Department of Pathology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand.

Plasma expanders (PEs) such as hydroxyethyl strach are widely used for volume replacement. The plantation and production of tapioca in Thailand is abundant which may provide a new source for PEs starch with novel properties. This work investigated the properties and circulatory effects of native tapioca starch-based PE (TPE). Various formulations of mixture between native tapioca starch and 0.9% sodium chloride solution were prepared and characterized in order to obtain the proper physicochemical and rheological properties. About 1% concentration by weight per volume of TPE was compared with 6% hydroxyethyl starch 130/0.4 in 0.9% sodium chloride (HES130/0.4) using an acute hemodilution by 40% of blood volume in an animal protocol. TPE had higher turbidity and viscosity but lower colloid osmotic pressure compared with HES 130/0.4. The in vivo study demonstrated that Golden Syrian hamsters hemodiluted with TPE maintained a mean arterial blood pressure and no significant difference compared to HES 130/0.4. The arterial vasodilation and functional capillary density in the animals hemodiluted with TPE had higher values than in the animals hemodiluted with HES 130/0.4. Although the in vivo study reported positive results using this native tapioca starch-based PE, the product needs work to improve some of its physiochemical properties.
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http://dx.doi.org/10.1002/jbm.b.33367DOI Listing
February 2016

Response of cardiac endothelial nitric oxide synthase to plasma viscosity modulation in acute isovolemic hemodilution.

Asian J Transfus Sci 2014 Jul;8(2):100-4

Institute of Biomedical Engineering, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand.

Background: Endothelial nitric oxide synthase (eNOS) is generally expressed in endocardial cells, vascular endothelial cells and ventricular myocytes. However, there is no experimental study elucidating the relationship between cardiac eNOS expression and elevated plasma viscosity in low oxygen delivery pathological conditions such as hemorrhagic shock-resuscitation and hemodilution. This study tested the hypothesis that elevated plasma viscosity increases cardiac eNOS expression in a hemodilution model, leading to positive effects on cardiac performance.

Materials And Methods: Two groups of golden Syrian hamster underwent an acute isovolemic hemodilution where 40% of blood volume was exchanged with 2% (low-viscogenic plasma expander [LVPE]) or 6% (high-viscogenic plasma expander [HVPE]) of dextran 2000 kDa. In control group, experiment was performed without hemodilution. All groups were performed in awake condition. Experimental parameters, i.e., mean arterial blood pressure (MAP), heart rate, hematocrit, blood gas content and viscosity, were measured. The eNOS expression was evaluated by eNOS Western blot analysis.

Results: After hemodilution, MAP decreased to 72% and 93% of baseline in the LVPE and HVPE, respectively. Furthermore, pO2 in the LVPE group increased highest among the groups. Plasma viscosity in the HVPE group was significantly higher than that in control and LVPE groups. The expression of eNOS in the HVPE group showed higher intensity compared to other groups, especially compared with the control group.

Conclusion: Our results demonstrated that cardiac eNOS has responded to plasma viscosity modulation with HVPE and LVPE. This particularly supports the previous studies that revealed the positive effects on cardiac function in animals hemodiluted with HVPE.
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http://dx.doi.org/10.4103/0973-6247.137444DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4140050PMC
July 2014

Nitric oxide synthase inhibition attenuates cardiac response to hemodilution with viscogenic plasma expander.

Korean Circ J 2014 Mar 12;44(2):105-12. Epub 2014 Mar 12.

Department of Bioengineering, University of California, San Diego, CA, USA.

Background And Objectives: Increased vascular wall shear stress by elevated plasma viscosity significantly enhances the endothelial nitric oxide synthase (eNOS) activity during an acute isovolemic hemodilution. Also the modulation of plasma viscosity has effects on the cardiac function that were revealed if a left ventricular (LV) pressure-volume (PV) measurement was used. The aim of this study was to assess cardiac function responses to nitric oxide synthase (NOS) inhibitors with the presence of an elevated plasma viscosity but a low hematocrit level. Furthermore, systemic parameters were monitored in a murine model.

Materials And Methods: As test group five anesthetized hamsters were administered with N(G)-nitro-L-arginine methyl ester (L-NAME), NOS inhibitor, whereas five other hamsters were used as control group without L-NAME infusion. The dosage of L-NAME was 10 mg/kg. An isovolemic hemodilution was performed by 40% of estimated blood volume with 6% w/v dextran 2000 kDa, high viscosity plasma expanders (PEs) with viscosity 6.34 cP. LV function was measured and assessed using a 1.4 Fr PV conductance catheter.

Results: The study results demonstrated that NOS inhibition prevented the normal cardiac adaptive response after hemodilution. The endsystolic pressure increased 14% after L-NAME infusion and maintained higher than at the baseline after hemodilution, whereas it gradually decreased in the animals without L-NAME infusion. The admission of L-NAME significantly decreased the maximum rate of ventricular pressure rise (+dP/dtmax), stroke volume and cardiac output after hemodilution if compared to the control group (p<0.05).

Conclusion: This finding supports the presumption that nitric oxide induced by an increased plasma viscosity with the use of a high viscosity PE plays a major role in the cardiac function during an acute isovolemic hemodilution.
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http://dx.doi.org/10.4070/kcj.2014.44.2.105DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3958604PMC
March 2014

Improving cardiac function with new-generation plasma volume expanders.

Am J Emerg Med 2013 Jan 3;31(1):54-63. Epub 2012 Aug 3.

Department of Bioengineering, University of California-San Diego, La Jolla, CA 92093, USA.

Background: Plasma expander (PE) based on polyethylene glycol (PEG) conjugated to albumin has shown positive results maintaining blood volume during hemodilution and restoring blood volume during resuscitation from hemorrhagic shock. Polyethylene glycol conjugation to human serum albumin (HSA), PEG-HSA, increases size, weight, and colloidal osmotic pressure, with minor effects on solution viscosity.

Methods: This study was designed to test the hypothesis that PEG-HSA (2 g/dL) produced by direct PEGylation chemistry improves cardiac function during 2 experimental models, (i) moderate hemodilution and (ii) resuscitation from hemorrhagic shock, compared with a conventional colloidal PE (Dextran 70 kd [Dx70], 6 g/dL). Cardiac function was studied using a miniaturized pressure volume conductance catheter implanted in the left ventricle and evaluated in terms of cardiac indices derived from the pressure volume measurements.

Results: Polyethylene glycol-HSA increased cardiac output, stroke volume, and stroke work and decreased systemic vascular resistance compared with Dx70 in both experimental models. The improvements induced by PEG-HSA in cardiac function were sustained over the observation time. Polyethylene glycol-HSA cardiac mechanoenergetics changes are the result of increased energy transferred per stroke and decreased resistance of the vasculature connecting the heart. In summary, PEG-HSA decreased left ventricle ejection impedance.

Conclusion: Ejection of blood diluted with PEG-HSA presented a reduced load to the heart, increased contractile function, and lowered the energy consumed per unit volume compared with Dx70. Our results emphasize the importance of heart function as a parameter to be included in the evaluation changes induced by new PEs.
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http://dx.doi.org/10.1016/j.ajem.2012.05.031DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3510356PMC
January 2013

Exogenous intravascular nitric oxide enhances ventricular function after hemodilution with plasma expander.

Life Sci 2012 Jan 26;90(1-2):39-46. Epub 2011 Oct 26.

Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093-0412, USA.

Aims: This study evaluated the hypothesis that exogenous nitric oxide (NO) supplementation during acute hemodilution with plasma expander (PE) provides beneficial effects on cardiac function.

Main Methods: Acute hemodilution in golden Syrian hamsters was induced by a 40% of blood volume exchange with dextran 70 kDa. Intravascular NO supplementation after hemodilution was accomplished with a NO donor, diethylenetriamine NONOate (DETA NONOate). The test group was treated with DETA NONOate, while the control group received only vehicle. Left ventricular cardiac function was studied using pressure-volume measurements obtained with a miniaturized conductance catheter.

Key Findings: Cardiac output increased to 122±5% and 107±1% of the baseline in the group treated with NO donor and the vehicle group, respectively. Stroke work per stroke volume (SW/SV) after hemodilution reduced to 90% of the baseline and the NO donor significantly reduced SW/SV compared to the vehicle. The minimum rate of pressure change (dP/dt(min)) was significantly lower in animals treated with the NO donor compared to vehicle treated animals. Systemic vascular resistance (SVR) decreased to 62±5% of the baseline in the NO donor group whereas the vehicle group SVR decreased to 83±5% of the baseline. Using intravital microscopy analysis of microvessel in the dorsal skinfold window chamber, we established that the NO donor group induced significant vasodilation compared to the vehicle group.

Significance: NO supplementation in an acute hemodilution with PE has beneficial effects on cardiac performance. However, the NO supplementation effects with a NO donor are dose-independent and short-lasting.
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http://dx.doi.org/10.1016/j.lfs.2011.10.013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3246102PMC
January 2012

Cardiac mechanoenergetic cost of elevated plasma viscosity after moderate hemodilution.

Biorheology 2010 ;47(3-4):225-37

Department of Bioengineering, University of California-San Diego, La Jolla, CA 92093, USA.

The purpose of this study was to investigate how plasma viscosity affects cardiac and vascular function during moderate hemodilution. Twelve anesthetized hamsters were hemodiluted by 40% of blood volume with two different viscosity plasma expanders. Experimental groups were based on the plasma expander viscosity, namely: high viscosity plasma expander (HVPE, 6.3 mPa · s) and low viscosity plasma expander (LVPE, 2.2 mPa · s). Left ventricular (LV) function was intracardiacally measured with a high temporal resolution miniaturized conductance catheter and concurrent pressure-volume results were used to calculate different LV indices. Independently of the plasma expander, hemodilution decreased hematocrit to 28% in both groups. LVPE hemodilution reduced whole blood viscosity by 40% without changing plasma viscosity, while HVPE hemodilution reduced whole blood viscosity by 23% and almost doubled plasma viscosity relative to baseline. High viscosity plasma expander hemodilution significantly increased cardiac output, stroke volume and stroke work compared to baseline, whereas LVPE hemodilution did not. Furthermore, an increase in plasma viscosity during moderate hemodilution produced a higher energy transfer per unit volume of ejected blood. Systemic vascular resistance decreased after hemodilution in both groups. Counter-intuitively, HVPE hemodilution showed lower vascular resistance and vascular hindrance than LVPE hemodilution. This result suggests that geometrical changes in the circulatory system are induced by the increase in plasma viscosity. In conclusion, an increase in plasma viscosity after moderate hemodilution directly influenced cardiac and vascular function by maintaining hydraulic power and reducing systemic vascular resistance through vasodilation.
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http://dx.doi.org/10.3233/BIR-2010-0574DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4130999PMC
June 2011

Effects of plasma viscosity modulation on cardiac function during moderate hemodilution.

Asian J Transfus Sci 2010 Jul;4(2):102-8

Department of Bioengineering, University of California, San Diego, La Jolla, CA, USA.

Background: Previous studies have found that increasing plasma viscosity as whole blood viscosity decrease has beneficial effects in microvascular hemodynamics. As the heart couples with systemic vascular network, changes in plasma and blood viscosity during hemodilution determine vascular pressure drop and flow rate, which influence cardiac function. This study aimed to investigate how changes in plasma viscosity affect on cardiac function during acute isovolemic hemodilution.

Materials And Methods: Plasma viscosity was modulated by hemodilution of 40% of blood volume with three different plasma expanders (PEs). Dextran 2000 kDa (Dx2M, 6.3 cP) and dextran 70 kDa (Dx70, 3.0 cP) were used as high and moderate viscogenic PEs, respectively. Polyethylene glycol conjugated with human serum albumin (PEG-HSA, 2.2 cP) was used as low viscogenic PE. The cardiac function was assessed using a miniaturized pressure-volume conductance catheter.

Results: After hemodilution, pressure dropped to 84%, 79%, and 78% of baseline for Dx2M, Dx70 and PEG-HSA, respectively. Cardiac output markedly increased for Dx2M and PEG-HSA. Dx2M significantly produced higher stroke work relative to baseline and compared to Dx70.

Conclusion: Acute hemodilution with PEG-HSA without increasing plasma viscosity provided beneficial effects on cardiac function compared to Dx70, and similar to those measured with Dx2M. Potentially negative effects of increasing peripheral vascular resistance due to the increase in plasma viscosity were prevented.
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http://dx.doi.org/10.4103/0973-6247.67034DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2937285PMC
July 2010

Cardiac systolic function recovery after hemorrhage determines survivability during shock.

J Trauma 2011 Apr;70(4):787-93

Department of Bioengineering, University of California, San Diego, La Jolla, California 92093-0412, USA.

Background: Small animal model has not been available to study cardiac pathophysiology during hemorrhagic shock. The main purpose of this study, therefore, was to establish earlier differences in left ventricle functional disturbances during hypovolemia comparable in survival and nonsurvival animals. Ventricular pressure-volume relationships have become well established as the most rigorous and comprehensive venue to assess intact heart function.

Methods: Studies were performed in anesthetized hamsters subjected to a 40% of blood volume hemorrhage to induce the hypovolemic shock. A miniaturized conductance catheter was used to measure left ventricular pressure and volume. Derived from the pressure-volume measurements, cardiac performance was evaluated using systolic and diastolic function indices.

Results: Thirteen animals were included; all animals survived the hemorrhage. Survival rate after 30 minutes of hypovolemic shock was 61.5%. End-systolic pressure was improved at the late stage of shock in the survival group, whereas no change of this index was found in the nonsurvival group. No significant differences in end-diastolic pressure and relaxation time constant were found between the nonsurvival and the survival groups. Fifteen minutes after the hemorrhage, the stroke work per stroke volume ratio significantly improved in the survival compared with nonsurvival, which also restored blood pressure.

Conclusion: The unique advantage of the pressure-volume methodology over all other available approaches to measure cardiac function is that it enables more specific measurement of the left ventricle performance independently from loading conditions and heart rate. Our findings demonstrated that failure to recover cardiac systolic function after hemorrhage, is a major determinant of mortality during hypovolemic shock.
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http://dx.doi.org/10.1097/TA.0b013e3181e7954fDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4133180PMC
April 2011
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