Stretchable pumps for soft machines.

Machines made of soft materials bridge life sciences and engineering1. Advances in soft materials have led to skin-like sensors and muscle-like actuators for soft robots and wearable devices1-3. Flexible or stretchable counterparts of most key mechatronic components have been developed4,5, principally using fluidically driven systems6-8; other reported mechanisms include electrostatic9-12, stimuli-responsive gels13,14 and thermally responsive materials such as liquid metals15-17 and shape-memory polymers18. Despite the widespread use of fluidic actuation, there have been few soft counterparts of pumps or compressors, limiting the portability and autonomy of soft machines4,8. Here we describe a class of soft-matter bidirectional pumps based on charge-injection electrohydrodynamics19. These solid-state pumps are flexible, stretchable, modular, scalable, quiet and rapid. By integrating the pump into a glove, we demonstrate wearable active thermal management. Embedding the pump in an inflatable structure produces a self-contained fluidic 'muscle'. The stretchable pumps have potential uses in wearable laboratory-on-a-chip and microfluidic sensors, thermally active clothing and autonomous soft robots.

SiCTeC: An inexpensive, easily assembled Peltier device for rapid temperature shifting during single-cell imaging.

Single-cell imaging, combined with recent advances in image analysis and microfluidic technologies, have enabled fundamental discoveries of cellular responses to chemical perturbations that are often obscured by traditional liquid-culture experiments. Temperature is an environmental variable well known to impact growth and to elicit specific stress responses at extreme values; it is often used as a genetic tool to interrogate essential genes. However, the dynamic effects of temperature shifts have remained mostly unstudied at the single-cell level, due largely to engineering challenges related to sample stability, heatsink considerations, and temperature measurement and feedback. Additionally, the few commercially available temperature-control platforms are costly. Here, we report an inexpensive (<$110) and modular Single-Cell Temperature Controller (SiCTeC) device for microbial imaging-based on straightforward modifications of the typical slide-sample-coverslip approach to microbial imaging-that controls temperature using a ring-shaped Peltier module and microcontroller feedback. Through stable and precise (±0.15°C) temperature control, SiCTeC achieves reproducible and fast (1-2 min) temperature transitions with programmable waveforms between room temperature and 45°C with an air objective. At the device's maximum temperature of 89°C, SiCTeC revealed that Escherichia coli cells progressively shrink and lose cellular contents. During oscillations between 30°C and 37°C, cells rapidly adapted their response to temperature upshifts. Furthermore, SiCTeC enabled the discovery of rapid morphological changes and enhanced sensitivity to substrate stiffness during upshifts to nonpermissive temperatures in temperature-sensitive mutants of cell-wall synthesis enzymes. Overall, the simplicity and affordability of SiCTeC empowers future studies of the temperature dependence of single-cell physiology.

Impact of parylene coating on heating performance of intravenous fluid warmer: a bench study.

BACKGROUND: Perioperative hypothermia is a common occurrence, particularly with the elderly and pediatric age groups. Hypothermia is associated with an increased risk of perioperative complications. One method of preventing hypothermia is warming the infused fluids given during surgery. The enFlow™ intravenous fluid warmer has recently been reintroduced with a parylene coating on its heating blocks. In this paper, we evaluated the impact of the parylene coating on the new enFlow's fluid warming capacity. METHODS: Six coated and six uncoated enFlow cartridges were used. A solution of 10% propylene glycol and 90% distilled H2O was infused into each heating cartridge at flow rates of 2, 10, 50, 150, and 200 ml/min. The infused fluid temperature was set at 4 °C, 20 °C, and 37 °C. Output temperature was recorded at each level. Data for analysis was derived from 18 runs at each flow rate (six cartridges at three temperatures). RESULTS: The parylene coated fluid warming cartridge delivered very stable output of 40 °C temperatures at flow rates of 2, 10, and 50 ml/min regardless of the temperature of the infusate. At higher flow rates, the cartridges were not able to achieve the target temperature with the colder fluid. Both cartridges performed with similar efficacy across all flow rates at all temperatures. CONCLUSIONS: At low flow rates, the parylene coated enFlow cartridges was comparable to the original uncoated cartridges. At higher flow rates, the coated and uncoated cartridges were not able to achieve the target temperature. The parylene coating on the aluminum heating blocks of the new enFlow intravenous fluid warmer does not negatively affect its performance compared to the uncoated model.

Real-Time Detection and Short-Term Prediction of Blast Furnace Burden Level Based on Space-Time Fusion Features.

Real-time, continuous and accurate blast furnace burden level information is of great significance for controlling the charging process, ensuring a smooth operation of a blast furnace, reducing energy consumption and emissions and improving blast furnace output. However, the burden level information measured by conventional mechanical stock rods and radar probes exhibit problems of weak anti-interference ability, large fluctuations in accuracy, poor stability and discontinuity. Therefore, a space-time fusion prediction and detection method of burden level based on a long-term focus memory network (LFMN) and an efficient structure self-tuning RBF neural network (ESST-RBFNN) is proposed. First, the space dimensional features are extracted by the space regression model based on radar data. Then, the LFMN is designed to predict the burden level and extract the time dimensional features. Finally, the ESST-RBFNN based on a proposed fast eigenvector space clustering algorithm (ESC) is constructed to obtain reliable and continuous burden level information with high accuracy. Both the simulation results and industrial verification indicate that the proposed method can provide real-time and continuous burden level information in real-time, which has great practical value for industrial production.

In vivo STED microscopy: A roadmap to nanoscale imaging in the living mouse.

Superresolution microscopy techniques are now widely used, but their application in living animals remains a challenging task. The first superresolution imaging in a live vertebrate was demonstrated with STED microscopy in the visual cortex of an anaesthetized mouse. Here, we explain the requirements for a simple but robust in vivo STED microscope as well as the surgical preparation of the cranial window and the mounting of the mouse in detail. We have developed a mounting stage with a heating plate to keep the mouse body temperature stable and that can be adjusted to the optical axis of the microscope. We have optimised the design to avoid inducing thermal drift, which is critical for nanoscale imaging. STED microscopy with a resolution of 60 nm requires special cranial window preparation to avoid motion artefacts. We have implemented a drain tube to reduce the fluid between the glass window and the surface of the brain, which has been identified as the main cause for the motion artefacts. Together, these advances in the preparation allow the use of a simple intraperitoneal anaesthesia and make the previously used venous infusion and artificial respiration obsolete.

Effects of different thermal insulation methods on the nasopharyngeal temperature in patients undergoing laparoscopic hysterectomy: a prospective randomized controlled trial.

BACKGROUND: This study explored the comparison of the thermal insulation effect of incubator to infusion thermometer in laparoscopic hysterectomy. METHODS: We assigned 75 patients enrolled in the study randomly to three groups: Group A: Used warming blanket; group B: Used warming blanket and infusion thermometer; group C: Used warming blanket and incubator. The nasopharyngeal temperature at different time points during the operation served as the primary outcome. RESULTS: The nasopharyngeal temperature of the infusion heating group was significantly higher than that of the incubator group 60 min from the beginning of surgery (T3): 36.10 ± 0.20 vs 35.81 ± 0.20 (P<0.001)90 min from the beginning of surgery (T4): 36.35 ± 0.20 vs 35.85 ± 0.17 (P<0.001). Besides, the nasopharyngeal temperature of the incubator group was significantly higher compared to that of the control group 60 min from the beginning of surgery (T3): 35.81 ± 0.20 vs 35.62 ± 0.18 (P<0.001); 90 min from the beginning of surgery (T4): 35.85 ± 0.17 vs 35.60 ± 0.17 (P<0.001). Regarding the wake-up time, that of the control group was significantly higher compared to the infusion heating group: 24 ± 4 vs 21 ± 4 (P = 0.004) and the incubator group: 24 ± 4 vs 22 ± 4 (P = 0.035). CONCLUSION: Warming blanket (38 °C) combined infusion thermometer (37 °C) provides better perioperative thermal insulation. Hospitals without an infusion thermometer can opt for an incubator as a substitute. TRIAL REGISTRATION: This trial was registered with ChiCTR2000039162 , 20 October 2020.

Promising Nanoparticle-Based Heat Transfer Fluids-Environmental and Techno-Economic Analysis Compared to Conventional Fluids.

Providing optimal operating conditions is one of the major challenges for effective heating or cooling systems. Moreover, proper adjustment of the heat transfer fluid is also important from the viewpoint of the correct operation, maintenance, and cost efficiency of these systems. Therefore, in this paper, a detailed review of recent work on the subject of conventional and novel heat transfer fluid applications is presented. Particular attention is paid to the novel nanoparticle-based materials used as heat transfer fluids. In-depth comparison of environmental, technical, and economic characteristics is discussed. Thermophysical properties including thermal conductivity, specific heat, density, viscosity, and Prandtl number are compared. Furthermore, the possible benefits and limitations of various transfer fluids in the fields of application are taken into account.

New Concept Air Conditioning System for the Operating Room to Minimize Patient Cooling and Surgeon Heating: A Historical Control Cohort Study.

BACKGROUND: Intraoperative hypothermia is a common adverse event. For avoiding the complication due to hypothermia, many warming devices and methods have been used in perioperative period. It has been reported that more patients undergoing laparoscopic surgery tend to have hypothermia than with open surgery. To avoid intraoperative hypothermia, many kinds of warming tools have been used. But, it was also reported that some warming methods increased perceptions of distraction and physical demand. METHODS: To achieve both patients' normothermia and surgeons' comfort, new air conditioning (AC) system was designed with considering the characteristics of laparoscopic surgery. The temperature of the airflows to the patient and to the surgeons can be adjusted independently in this new system. The new system has two parts. One controls the temperature of the central area over the operation table. The air from this part falls on the patients. The other part is the lateral area beside the operating table; the air from this part falls on the surgeons. The subjects of this study were 160 gastric cancer patients and 316 colorectal cancer patients undergoing laparoscopic surgery. The temperature of the central flow was set 23.5 °C, and the temperature of the lateral flow was set 22 °C just after the anesthesia. The number of timepoints the patient spent in hypothermic state, defined as a temperature cooler by 0.5 °C or more than that at the starting point of surgery, was determined in each patient. RESULTS: In the results, the rate of hypothermic state in old operation rooms was 23.8% and that in new operation rooms was 2.7% in male gastric cancer patients (p < 0.01). And those were 37.1% in old operation rooms and 0.9% in new operation rooms in female gastric cancer patients (p < 0.01). The rate of hypothermic state in old operation rooms was 30.0% and that in new operation rooms was 9.5% in male colorectal cancer patients (p < 0.01). And those were 41.6% in old operation rooms and 8.9% in new operation rooms in female colorectal cancer patients (p < 0.01). The similar results were showed in the study, which subjects were limited the patients undergoing surgery in 2015 and 2016; which were the last year the old operation rooms were used and the first year the new operation rooms were used. CONCLUSIONS: Thus, the usefulness of the new air conditioning system for achieving both patients' normothermia and comfort of surgeons could be verified in this study.

In situ efficiency of filters in residential central HVAC systems.

High-efficiency filtration in residential forced-air heating, ventilation, and air conditioning (HVAC) systems protects equipment and can reduce exposure to particulate matter. Laboratory tests provide a measure of the nominal efficiency, but they may not accurately reflect the in situ efficiency of the filters because of variations in system conditions and changes in filter performance over time. The primary focus of this paper is to evaluate the effective filtration efficiency, which is inclusive of any loading and system impacts, in 21 occupied residential homes through in-duct concentration measurements. We considered the role of filter media by testing both electret and non-electret media, as well as the role of loading by considering new and used filters. The results show that filters with higher nominal efficiency generally had higher effective filtration efficiency in the same home. In terms of performance change, there is no significant difference in efficiency between initial and 3-month non-electret filters, but the efficiency of electret filters generally decreased over time. However, both nominal efficiency and performance change were vastly overshadowed by the wide variety in loading and system conditions across homes, making it hard to predict filter efficiency in a given home without in situ measurements.

Prevention of Perioperative Hypothermia: A Prospective, Randomized, Controlled Trial of Bair Hugger Versus Inditherm in Patients Undergoing Elective Arthroscopic Shoulder Surgery.

PURPOSE: To determine if a clinically significant difference in the core body temperature (CBT) exists between the Bair Hugger (BH) and Inditherm (IT) warming devices in patients undergoing arthroscopic shoulder surgery. METHODS: This was a parallel, 2-treatment, prospective, randomized, controlled trial conducted in patients undergoing elective arthroscopic shoulder surgery in the beach-chair position using room-temperature irrigation fluid. The BH was used as the indicative forced-air warming device, whereas the IT served as the indicative resistive heating system. By use of a minimal clinically significant difference of 0.6°C and standard deviation of 0.6°C, a power analysis showed that a sample size of 90 patients (45 per group) would be required. Patients fulfilling the inclusion criteria were recruited from the clinics of the senior authors. Anesthetic and surgical protocols were standardized. The intraoperative CBT was recorded every 5 minutes using a nasopharyngeal thermistor probe. Demographic data as well as the volume of irrigation fluid used were also noted. RESULTS: A steady decline in the CBT was observed in both groups up to 30 minutes after induction of anesthesia. Beyond 30 minutes, the BH group showed a gradual increase in temperature whereas it continued to decline in the IT group. A statistically significant difference in the CBT was observed from 60 minutes onward (P = .025). This difference continued to increase up to 90 minutes (P < .001). At no time was a rise in the CBT observed in the IT group. At completion of the study and surgical procedure, 13 of 47 patients in the BH group and 32 of 44 patients in the IT group had hypothermia (P = .0002). CONCLUSIONS: The CBT was statistically significantly better with the use of the BH compared with the IT mattress. However, the differences in the CBT did not reach the level of clinical significance of 0.6°C. Far fewer patients in the BH group had hypothermia at the end of surgery. Therefore, this study supports the use of the BH in elective arthroscopic shoulder surgery for the prevention of hypothermia. LEVEL OF EVIDENCE: Level I.

Erythema Ab Igne in an Adolescent With Chronic Pain: An Alarming Cutaneous Eruption From Heat Exposure.

Erythema ab igne (EAI) is a cutaneous finding caused by prolonged heat exposure and is characterized by a reticular, brownish-pigmented, often telangiectatic dermatosis. The eruption is reminiscent of livedo reticularis, which is typically seen in the setting of a number of rheumatologic conditions, most prominently vasculitis. Identification of key features distinguishing EAI from livedo reticularis can aid in the diagnosis of EAI and correct elucidation of the underlying etiology. Our patient presented with heating pad-induced EAI in the setting of chronic pain. Only 6 other pediatric cases of EAI associated with heat sources for chronic pain are reported (Acta Derm Venereol. 2014;94:365-367, J Pediatr. 2013;163:1789, Int J Eat Disord. 2013;46:381-383, Arch Dis Child. 2008;93:389, Arch Pediatr Adolesc Med. 2012;166:185-186, Br J Clin Pract. 1990;44:248-251). Our case highlights the need for awareness of this pathognomonic skin eruption in children with chronic pain conditions to help avoid an extensive workup for vasculitis.

Thermal burns of the spectacle associated with supplementary heating in native New Zealand geckos.

Case history: Gradual onset of ocular opacity was observed in three gold-striped geckos (Woodworthia chrysosiretica), and five Pacific geckos (Dactylocnemis pacificus) held in two adjacent terrariums in a zoological institution located in the North Island of New Zealand. Ultraviolet light and heat had been provided for the previous 3-4 years by a fluorescent bulb, but in the last 4 weeks of winter a ceramic heat bulb had been added, situated 10 cm above the upper mesh of the cageClinical findings: All eight geckos presented with mostly bilateral lesions of varying severity confined to the central or upper quadrant of the spectacles. These lesions ranged from variable areas of opacity within the stroma of the spectacle to similarly distributed ulcers of the surface epithelium of both spectacles. The spectacle lesions in the Pacific geckos responded well to treatment with topical combined antimicrobial therapy, within 18-29 days. The gold-striped geckos suffered complications including dysecdysis, severe spectacle ulceration and perforation, mycotic spectaculitis, and widespread mycotic dermatitis resulting in death or leading to euthanasia.Pathological findings: In the three gold-striped geckos, there were extensive areas of deep ulceration and replacement of the spectacle with a thick serocellular crust containing large numbers of fungal elements. The affected areas of the stroma were expanded by large deposits of proteinaceous and mucinous material, pyknotic cellular debris and moderate numbers of heterophils and macrophages as well as infiltrating fungal hyphae.Diagnosis: Mycotic spectaculitis with ulceration and perforation, and disseminated mycotic dermatitis likely secondary to thermal burns.Clinical relevance: This is the first report of thermal burns of the spectacle in any reptile. There was species variation in the burn severity with gold-striped geckos showing more severe lesions, possibly due to a mix of behavioural and anatomical factors. The thermal burns to the spectacles in three cases were complicated by delayed healing, perforation, dysecdysis and severe mycotic infection.

Comparing Forced-Air to Resistive-Polymer Warming for Perioperative Temperature Management: A Retrospective Study.

PURPOSE: Compare perioperative temperature management between forced-air warming (FAW) and resistive-polymer heating blankets (RHBs). DESIGN: A retrospective, quasi-experimental study. METHODS: Retrospective data analysis of nonspine orthopedic cases (N = 426) over a one-year period including FAW (n = 119) and RHBs (n = 307). FINDINGS: FAW was associated with a significantly higher final intraoperative temperature (P = .001, d = 0.46) than the RHB. The incidence of hypothermia was not found to be significantly different at the end (P = .102) or anytime throughout surgery (P = .270). Of all patients who started hypothermic, the FAW group had a lower incidence of hypothermia at the end of surgery (P = .023). CONCLUSIONS: FAW was associated with higher final temperatures and a greater number of normothermic patients than RHBs. However, no causal relationship between a warming device and hypothermia incidence should be assumed.

Stored platelet number and viscoelastic maximum amplitude are not altered by warming or rapid infusion.

BACKGROUND: Platelet transfusion is an important aspect of hemostatic resuscitation. Leading textbooks recommend never infusing platelets through warmers or rapid infusers, but there is no evidence to justify this position. MATERIALS AND METHODS: We obtained units of apheresis platelets in plasma from our hospital blood bank and drew a baseline sample from every unit. In the warmer arm, an aliquot from each unit was injected into a fluid warmer heated to 41°C (Ranger, 3M Corporation). After 5 minutes' incubation, the aliquot was withdrawn and sampled. In the infuser arm, we ran the remainder of the unit through a rapid infuser (RI-2, Belmont Instrument Corporation) at 500 mL/min while warmed, and obtained a sample from the outflow line. A platelet count and viscoelastic maximum amplitude (Haemonetics) was measured from every sample. RESULTS: We observed no clotting or device malfunctions. Average postwarmer temperature was 41.8°C (range, 41.0-43.0). There was no significant difference in postwarmer platelet count or viscoelastic maximum amplitude. Average postinfuser temperature was 37.4°C (range, 36.1-39.0). All units reached the goal infusion rate of 500 mL/min. There was a small increase in postinfuser platelet count. There was no significant change in postinfuser viscoelastic maximum amplitude. CONCLUSION: We were unable to detect any effect of warming or rapid infusion on the number or viscoelastic maximum amplitude of stored apheresis platelets. Contrary to common teaching, these results suggest that rapid infusion and warming does not meaningfully harm apheresis platelets.

Biogeography of thermophiles and predominance of Thermus scotoductus in domestic water heaters.

Built systems such as water heaters can harbor extremophiles similar to those residing in natural hot springs, but the extent of colonization is not well understood. To address this, we conducted a survey of thermophilic microorganisms in household water heaters across the United States. Filter samples and inoculated cultures were collected by citizen-scientists from 101 homes. Draft genomes were assembled from cultured isolates and 16S rRNA genes were sequenced from filter samples. 28% of households harbored communities with unambiguous DNA signatures of thermophilic organisms, 36% of households provided viable inocula, and 21% of households had both. All of the recovered cultures as well as the community sequencing results revealed Thermus scotoductus to be the dominant thermophile in domestic water heaters, with a minority of water heaters also containing Meiothermus species and a few containing Aquificae. Sequence distance comparisons show that allopatric speciation does not appear to be a strong control on T. scotoductus distribution. Our results demonstrate that thermophilic organisms are widespread in hot tap water, and that Thermus scotoductus preferentially colonizes water heaters at the expense of local environmental Thermus strains.

Postoperative Myocardial Injury in Middle-Aged and Elderly Patients Following Curative Resection of Esophageal Cancer With Aggressive or Standard Body Temperature Management: A Randomized Controlled Trial.

BACKGROUND: Risk of intraoperative hypothermia is relatively high in middle-aged and elderly patients undergoing curative resection of esophageal cancer, which may cause myocardial ischemia during the early postoperative period. The objective of this study was to compare aggressive or standard body temperature management for lowering the incidence of postoperative myocardial injury that was assessed by troponin levels collected at a priori defined set times in these patients. METHODS: Seventy patients undergoing elective curative resection of esophageal cancer were randomly assigned to undergo aggressive body temperature management (nasopharyngeal temperature ≥36°C) or standard body temperature management (n = 35 in each arm). The primary outcome was myocardial injury, defined as the occurrence of elevated troponin I (>0.06 µg/L) or elevated high-sensitivity troponin T (≥0.065, or 0.02 µg/L≤ high-sensitivity troponin T <0.065 µg/L, but with an absolute change of at least 0.005 µg/L) or both during 2 days after surgery. Secondary outcomes included (1) severe arrhythmia, including atrial fibrillation, supraventricular tachycardia, frequent premature ventricular contractions intraoperatively or during 3 days postoperatively; (2) hypoxemia or metabolic acidosis during the first 12 h postoperatively; and (3) deep vein thrombosis or pulmonary embolism during 3 days postoperatively. RESULTS: Incidence of postoperative 2-day myocardial injury was 8.6% (3/35) among patients receiving aggressive body temperature management and 31.4% (11/35) among patients receiving standard body temperature management (P = .017, χ). Relative risk of myocardial injury in the aggressive body temperature management group was 0.27 (95% CI, 0.08-0.89). Incidence of intra- and postoperative 3-day severe cardiac arrhythmia was 2.9% (1/35) among patients receiving aggressive body temperature management and 28.6% (10/35) among patients receiving standard body temperature management. Incidence of postoperative 12-h hypoxia was 17.1% (6/35) with aggressive body temperature management and 40.0% (14/35) with standard body temperature management. Incidence of postoperative 12-h metabolic acidosis was 20% (7/35) among patients receiving aggressive body temperature management and 48.6% (17/35) among patients receiving standard body temperature management. Incidence of postoperative 3-day deep vein thrombosis or pulmonary embolism was 0% (0/35) with aggressive body temperature management and 2.9% (1/35) with standard body temperature management. CONCLUSIONS: Aggressive body temperature management may be associated with a lower incidence of postoperative myocardial injury.

Quantitative filter forensics with residential HVAC filters to assess indoor concentrations.

Analysis of the dust from heating, ventilation, and air conditioning (HVAC) filters is a promising long-term sampling method to characterize airborne particle-bound contaminants. This filter forensics (FF) approach provides valuable insights about differences between buildings, but does not allow for an estimation of indoor concentrations. In this investigation, FF is extended to quantitative filter forensics (QFF) by using measurements of the volume of air that passes through the filter and the filter efficiency, to assess the integrated average airborne concentrations of total fungal and bacterial DNA, 36 fungal species, endotoxins, phthalates, and organophosphate esters (OPEs) based on dust extracted from HVAC filters. Filters were collected from 59 homes located in central Texas, USA, after 1 month of deployment in each summer and winter. Results showed considerable differences in the concentrations of airborne particle-bound contaminants in studied homes. The airborne concentrations for most of the analytes are comparable with those reported in the literature. In this sample of homes, the HVAC characterization measurements varied much less between homes than the variation in the filter dust concentration of each analyte, suggesting that even in the absence of HVAC data, FF can provide insight about concentration differences for homes with similar HVAC systems.

Comparison of portable blood-warming devices under simulated pre-hospital conditions: a randomised in-vitro blood circuit study.

Pre-hospital transfusion of blood products is a vital component of many advanced pre-hospital systems. Portable fluid warmers may be utilised to help prevent hypothermia, but the limits defined by manufacturers often do not reflect their clinical use. The primary aim of this randomised in-vitro study was to assess the warming performance of four portable blood warming devices (Thermal Angel, Hypotherm X LG, °M Warmer, Buddy Lite) against control at different clinically-relevant flow rates. The secondary aim was to assess haemolysis rates between devices at different flow rates. We assessed each of the four devices and the control, at flow rates of 50 ml.min-1 , 100 ml.min-1 and 200 ml.min-1 , using a controlled perfusion circuit with multisite temperature monitoring. Free haemoglobin concentration, a marker of haemolysis, was measured at multiple points during each initial study run with spectrophotometry. At all flow rates, the four devices provided superior warming performance compared with the control (p < 0.001). Only the °M Warmer provided a substantial change in temperature at all flow rates (mean (95%CI) temperature change of 21.1 (19.8-22.4) °C, 20.4 (19.1-21.8) °C and 19.4 (17.7-21.1) °C at 50 ml.min-1 , 100 ml.min-1 and 200 ml.min-1 , respectively). There was no association between warming and haemolysis with any device (p = 0.949) or flow rate (p = 0.169). Practical issues, which may be relevant to clinical use, also emerged during testing. Our results suggest that there were significant differences in the performance of portable blood warming devices used at flow rates encountered in clinical practice.

Characterisation of aluminium release by the enFlow® fluid-warming system in crystalloids and blood products.

The use of uncoated aluminium-heated plates in an intravenous fluid-warming system has been shown to produce high levels of aluminium in Sterofundin 1/1E, a balanced crystalloid solution. However, the effect of this fluid-warming device on other balanced crystalloid solutions and blood products has not been studied. Using mass spectrometry we measured aluminium levels in Plasma-Lyte 148, compound sodium lactate solution, 4% human albumin solution, expired resuspended packed red cells and fresh frozen plasma that were pumped through an enFlow® fluid-warming system at 2 ml.min-1 . Samples were taken at baseline before heating and then at 10-min intervals up to 60 min with the system set to warm the fluids to 40 °C. High concentrations of aluminium were found for Plasma-Lyte 148 and compound sodium lactate solutions (mean (SD) 223 (0.6) µmol.l-1 and 163 (0.2) µmol.l-1 at 60 min, respectively); both concentrations were significantly greater than the United States Food and Drug Administration recommended maximum limit for aluminium in intravenous nutrition of 25 µg.l-1 (0.9 µmol.l-1 ). Lower aluminium levels were found in 4% human albumin solutions, expired resuspended red cells and fresh frozen plasma at 60 min (mean (SD) 5.7 (0.1) µmol.l-1 , 2.7 (0.0) µmol.l-1 and 2.3 (0.4) µmol.l-1 , respectively). The process allowing addition of aluminium to be added to Sterofundin 1/1E by the enFlow fluid warmer also occurs in Plasma-Lyte 148 and compound sodium lactate solutions and to a lesser degree in blood products. The exact mechanism facilitating this process and its clinical significance remain unclear.

Investigation and Evaluation of Potential Aerosol Release by Maquet/Getinge Heater-Cooler Units Used during Cardiac Surgery.

BACKGROUND: Heater-Cooler units (HCUs) supply tempered water through blood heat exchangers and through warming/cooling blankets to control the body temperature of heart surgery patients. Bacteria which potentially colonize the stored water may escape from the tank into the environment and are carried by the device's cooling air exhaust into the sterile field and finally may infect open chest heart surgery patients. Reports from several countries are connecting the infection of open chest heart surgery patients to airborne transmitted Mycobacteria chimaera which were found in the water of heater-cooler devices. As a consequence of the vigilance system for medical products, we investigated the potential release and the possible transmission of bacteria from the tank water into the sterile operating field. MATERIALS AND METHODS: In the absence of an evaluation standard for this problem, measurable acceptance criteria for particle releases and a qualitative method for bacteria transmission assessment have been deployed. To assess potential bacteria transmission into the sterile field, tank water of the test devices was inoculated with high concentrations of Pseudomonas aeruginosa (reference strain ATCC15442) and operated in an operating room with simulated use. RESULTS: The particle release at the tank lids of the Maquet/Getinge HCU 30 and HCU 40 during the filling of the tubes with water (deaeration) and during the removal of water from the tubes (emptying) increased slightly, but close to the blank readings for the larger particles. As expected, the particle release at the cooling air grids was higher than around the tank openings. Consistent with the particle measurements, no bacteria from the tank water were found in the sterile field during simulated use of all highly inoculated machines in an operating room. CONCLUSION: In summary, we assess the risk of infecting open chest heart surgery patients with aerosol-transmitted bacteria from water inside the Maquet/Getinge HCU 40, HCU 30 to be negligible, if handled in accordance with common clinical hygienic precautions.