Systematic Characterization of High-Power Short-Duration Ablation: Insight From an Advanced Virtual Model

Background: High-power short-duration (HPSD) recently emerged as a new approach to radiofrequency (RF) catheter ablation. However, basic and clinical data supporting its effectiveness and safety is still scarce.Objective: We aim to characterize HPSD with an advanced virtual model, able to assess lesion dimensions and complications in multiple conditions and compare it to standard protocols.Methods: We evaluate, on both atrium and ventricle, three HPSD protocols (70 W/8 s, 80 W/6 s, and 90 W/4 s) through a realistic 3D computational model of power-controlled RF ablation, varying catheter tip design (spherical/cylindrical), contact force (CF), blood flow, and saline irrigation. Lesions are defined by the 50°C isotherm contour. Ablations are deemed safe or complicated by pop (tissue temperature >97°C) or charring (blood temperature >80°C). We compared HPSD with standards protocols (30–40 W/30 s). We analyzed the effect of a second HPSD application.Results: We simulated 432 applications. Most (79%) associated a complication, especially in the atrium. The three HPSD protocols performed similarly in the atrium, while 90 W/4 s appeared the safest in the ventricle. Low irrigation rate led frequently to charring (72%). High-power short-duration lesions were 40–60% shallower and smaller in volume compared to standards, although featuring similar width. A second HPSD application increased lesions to a size comparable to standards.Conclusion: High-power short-duration lesions are smaller in volume and more superficial than standards but comparable in width, which can be advantageous in the atrium. A second application can produce lesions similar to standards in a shorter time. Despite its narrow safety margin, HPSD seems a valuable new clinical approach.

PSIV-15 Examining the relationship between breed type and anabolic implant protocols in performance in the feedlot, health, and temperament of beef steers

The purpose of this research was to compare anabolic implant protocols in feedlot steers of two different breed types. Sixty steers were stratified by weight and breed in a 2 x 3 factorial design examining two different breeds: Angus (AN; n = 38) or Santa Gertrudis influenced (SG; n = 22), and three implant strategies: no implant (CON; n = 20), a moderate implant protocol (d0 implant: Revalor-G, d56 implant: Revalor-IS, d112 implant: Revalor-S; MOD; n = 20), or a vigorous implant protocol (d0 implant: Revalor-IS, d56 implant: Revalor-S, d112 implant: Revalor-200; VIG; n = 20). Steers were randomly placed into pens equipped with GrowSafe® bunks and fed the same ration. Weight, chute score (CS), exit velocity, blood, temperature, hip height and 12th rib fat thickness were collected approximately every 28d over a 112d period. Over the 112 d, SG steers tended (P = 0.10) to gain more hip height than AN steers. Anabolic implant protocol influenced total gain with both VIG and MOD steers gaining more (P < 0.01) than CON. On d 0, SG steers had a higher (P < 0.01) CS compared to AN steers, with this being maintained through the course of the trial. There was also as a tendency for there to be a breed*treatment effect (P = 0.06) on d112, with SG-MOD having a higher (P = 0.04) CS than AN-VIG, and a tendency (P = 0.08) for SG-VIG to have a higher CS than AN-VIG. Moderate and VIG implant protocols may be a useful tool to increase performance in feedlot steers. However, this research did find that SG influenced steers may have a more excitable temperament, but implant protocol did not influence (P > 0.05) temperament.

The Role of Deep Hypothermia in Cardiac Surgery

Hypothermia is defined as a decrease in body core temperature to below 35°C. In cardiac surgery, four stages of hypothermia are distinguished: mild, moderate, deep, and profound. The organ protection offered by deep hypothermia (DH) enables safe circulatory arrest as a prerequisite to carrying out cardiac surgical intervention. In adult cardiac surgery, DH is mainly used in aortic arch surgery, surgical treatment of pulmonary embolism, and acute type-A aortic dissection interventions. In surgery treating congenital defects, DH is used to assist aortic arch reconstructions, hypoplastic left heart syndrome interventions, and for multi-stage treatment of infants with a single heart ventricle during the neonatal period. However, it should be noted that a safe duration of circulatory arrest in DH for the central nervous system is 30 to 40 min at most and should not be exceeded to prevent severe neurological adverse events. Personalized therapy for the patient and adequate blood temperature monitoring, glycemia, hematocrit, pH, and cerebral oxygenation is a prerequisite and indispensable part of DH.

Temperature and haemodynamic effects of a 100 mL bolus of 20% albumin at room versus body temperature in cardiac surgery patients

OBJECTIVE: To study the temperature and haemodynamic effects of room versus body temperature 20% albumin fluid bolus therapy (FBT). DESIGN: Single-centre, prospective, before–after trial. SETTING: A tertiary intensive care unit (ICU) in Australia. PARTICIPANTS: Sixty ventilated post-cardiac surgery patients. INTERVENTION: Room versus body temperature 100 mL 20% albumin FBT. MAIN OUTCOME MEASURES: We recorded haemodynamic data from FBT start to 30 minutes after FBT. The cardiac index (CI) response was defined by a CI increase > 15%, and the mean arterial pressure (MAP) response was defined by a MAP increase > 10%. OUTCOMES: Immediately after FBT, median blood temperature decreased by -0.1°C (interquartile range [IQR], -0.1 to 0.0°C) with room temperature albumin versus 0.0°C (IQR, -0.1 to 0.0°C) with body temperature albumin (P < 0.001). The CI or MAP responses were similar. There was, however, a time and study group interaction for blood temperature (P < 0.001) for absolute and relative changes. In addition, mean pulmonary arterial pressure (PAP) (P = 0.002) increased more with body temperature albumin and remained higher for most of the observation period. CONCLUSION: Compared with room temperature albumin FBT, body temperature 20% albumin FBT prevents FBT-associated blood temperature fall and increases mean PAP. However, CI and MAP changes were the similar between the two groups, implying that fluid temperature has limited haemodynamic effects in these patients.

Temperature management on cardiopulmonary bypass: Is it standardised across Great Britain and Ireland?

Temperature management is an essential element of cardiopulmonary bypass (CPB), as indicated in the Guide to Good Practice in Clinical Perfusion, ‘The safe conduct of CPB requires the clinical perfusionist to measure and control. . . blood temperature. . . during the period of bypass’. To review current practice, we have conducted a research survey into the management of temperature on CPB. Surveys were distributed to each centre in Great Britain and the Republic of Ireland, investigating numerous temperature management practices, to elucidate current practice and assess if recent research into temperature management marry routine clinical practice. Our results demonstrate that nasopharyngeal temperature is the most common (52%) temperature site used across the many centres, which correlates with previous research as a routine site for cerebral temperature management. The arterial outlet of the oxygenator temperature was used in 33% of centres, however, all centres lacked the knowledge to maintain this temperature below 37°C. There was significant variation between all centres, especially regarding rewarming times (20–40 minutes), demonstrating a lack of uniformity among perfusion centres. Interestingly, most centres have been using the same protocol that has been in place over the previous 10 years. To conclude, the practice of temperature management is changing with the awareness of new research. Lower target temperatures are recommended for rewarming, ensuring a lower temperature gradient and a longer mean rewarming time.

Modeling and Simulation of an Invasive Mild Hypothermic Blood Cooling System

Nowadays, mild hypothermia is widely used in the fields of post-cardiac arrest resuscitation, stroke, cerebral hemorrhage, large-scale cerebral infarction, and craniocerebral injury. In this paper, a locally mixed sub-low temperature device is designed, and the cold and hot water mixing experiment is used to simulate the human blood transfer process. To set a foundation for the optimization of the heat transfer system, the static characteristics are analyzed by building the mathematic model and setting up the experimental station. In addition, the affection of several key structure parameters is researched. Through experimental and simulation studies, it can be concluded that, firstly, the mathematical model proved to be effective. Secondly, the results of simulation experiments show that 14.52 °C refrigeration can reduce the original temperature of 33.42 °C to 32.02 °C, and the temperature of refrigerated blood rises to 18.64 °C, and the average error is about 0.3 °C. Thirdly, as the thermal conductivity of the vascular sheath increases, the efficiency of the heat exchange system also increases significantly. Finally, as the input cold blood flow rate increases, the mass increases and the temperature of the mixed blood temperature decreases. It provides a research basis for subsequent research on local fixed-point sub-low temperature control technology.

Accuracy of zero-heat-flux thermometry and bladder temperature measurement in critically ill patients

Core temperature (TCore) monitoring is essential in intensive care medicine. Bladder temperature is the standard of care in many institutions, but not possible in all patients. We therefore compared core temperature measured with a zero-heat flux thermometer (TZHF) and with a bladder catheter (TBladder) against blood temperature (TBlood) as a gold standard in 50 critically ill patients in a prospective, observational study. Every 30 min TBlood, TBladder and TZHF were documented simultaneously. Bland–Altman statistics were used for interpretation. 7018 pairs of measurements for the comparison of TBlood with TZHF and 7265 pairs of measurements for the comparison of TBlood with TBladder could be used. TBladder represented TBlood more accurate than TZHF. In the Bland Altman analyses the bias was smaller (0.05 °C vs. − 0.12 °C) and limits of agreement were narrower (0.64 °C to − 0.54 °C vs. 0.51 °C to – 0.76 °C), but not in clinically meaningful amounts. In conclusion the results for zero-heat-flux and bladder temperatures were virtually identical within about a tenth of a degree, although TZHF tended to underestimate TBlood. Therefore, either is suitable for clinical use.German Clinical Trials Register, DRKS00015482, Registered on 20th September 2018, http://apps.who.int/trialsearch/Trial2.aspx?TrialID=DRKS00015482.

Analysis of the effect of external heating in the human tissue: A finite element approach

Thermal therapy which involves either raising or lowering tissue temperature to treat malignant cells needs precise acknowledgment of thermal history inside the biological system to ensure effective treatment. For this purpose, this study presents a two-dimensional unsteady finite element model (FEM) of the bioheat transfer problem based on Pennes bio-heat equation to analyze the thermal response of tissue subject to external heating. Crank-Nikolson scheme was used for the unsteady solution. A finite element code was developed using C language to calculate results. The obtained numerical result was compared with the analytical and other numerical results available in the literature. A good agreement was found from the comparison. Temperature distribution inside the human body due to constant and sinusoidal spatial and surface heating were analyzed. Response to point heating was also investigated. Moreover, a sensitivity analysis was carried out to know the effect of various parameters, i.e. blood temperature, thermal conductivity, and blood perfusion rate on tissue temperature. The outcome of this study will be helpful for the researchers and physicians involved in the thermal treatment of human tissue.

Expeditionary Immersion Circulating Heating Device: A Promising Technique for Treating Frostbite Injuries and Warming Intravenous Fluids in a Forward Deployed Cold Weather Environment

Introduction Cold weather injuries require prompt warm water immersion therapy, which proves to be a difficult task in the cold austere environment. Current guidelines recommend 104 °F water immersion, but producing and maintaining large volumes of warm water is challenging in sub-freezing temperatures. We describe a novel process of utilizing a sous vide immersion circulator to maintain warm fluids for immersion therapy and efficient fluid rewarming in a cold forward-deployed setting for the treatment of cold weather injuries in an effort to bridge the gap between current medical guidelines and practices. Materials and Methods Large water cans were warmed to 104 °F with the immersion circulator. A thermometer was inserted into a 1-inch steak, frozen to 30 °F, and placed in a basin with only the warmed water while the internal temperature was monitored until physiologic temperature was achieved. The time to this endpoint was recorded. A 1-L bag of normal saline and a 450-mL bag of whole blood were also separately warmed by the same technique. The temperature of the normal saline was monitored at 0-, 5-, 7-, 8-, 9-, and 10 -minute intervals. The process was similarly repeated, measuring the whole blood temperature at 0-, 5-, 7-, and 10-minute intervals. Results Ambient internal tent temperatures averaged 54 °F; outdoor temperatures were consistently sub-freezing. The 5-gallon cans of water at ambient temperature heated to 104 °F in 15 minutes. The water temperature remained constant for 3 weeks with the circulator running. The frozen steak started at 30 °F and reached 98 °F in 52 minutes and 45 seconds. The bag of normal saline and whole blood, refrigerated to 39 °F, achieved temperatures of 102 °F and 94 °F respectively after 10 minutes. Conclusion A heating immersion circulator device is a lightweight, flameless, and inexpensive way to consistently heat large volumes of water for treatment of cold weather injuries, hypothermia, and whole blood rewarming in a cold austere environment.

Blood temperature monitoring–guided vascular access intervention improved dialysis adequacy

Objectives: The aim of this study was to investigate whether blood temperature monitoring–guided vascular access intervention could improve dialysis adequacy. Methods: We retrospectively evaluated all patients who received outpatient-based prevalent hemodialysis patients ( n = 84) in our artificial kidney room between January 2019 and October 2019. Through blood temperature monitoring, access blood flow was calculated every month and Kt/ V was calculated every 3 months. The reference point was set at the time of vascular intervention in the patients ( n = 27) who underwent intervention or at the middle of the study period in patients ( n = 57) who did not undergo intervention. The mean blood temperature monitoring–estimated access flow and Kt/ V before and after the reference point were calculated and compared. Results: Among 84 patients, 30 (35.7%) showed access flow rates of <500 mL/min, calculated by blood temperature monitoring during the study period. Twenty-seven patients (32.1%) underwent vascular intervention, of whom 24 (28.6%) showed access flow rates of <500 mL/min, 2 (2.4%) showed weak bruit or thrill incapable of needling, and 1 (1.2%) presented acute occlusion. Six patients (7.1%) whose access flow rates were <500 mL/min refused to undergo intervention. All angiographies in the patients whose access flow rates were <500 mL/min who underwent intervention showed a significant stenosis. The mean change in blood temperature monitoring–estimated access flow and Kt/ V before and after vascular intervention was 483.3 ± 490.6 and 0.19 ± 0.21, respectively, which showed significant differences (all p < 0.05). A weak positive correlation between the mean change in blood temperature monitoring–estimated access flow and Kt/ V was shown in all study patients by Pearson’s correlation analysis ( r = 0.234, p = 0.033). Conclusion: Access flow estimation by blood temperature monitoring might identify candidates who require vascular intervention. Blood temperature monitoring–guided vascular intervention significantly improved access flow and dialysis adequacy.