Significant Changes In Cardiac Output Research Articles

Mechanisms for blood pressure reduction following isometric exercise training: a systematic review and meta-analysis.

Isometric exercise training (IET) is established as an effective antihypertensive intervention. Despite this, the physiological mechanisms driving blood pressure (BP) reductions following IET are not well understood. Therefore, we aimed to perform the first meta-analysis of the mechanistic changes measured following IET. PubMed, Cochrane library and SPORTDiscus were systematically searched for randomized controlled trials published between January 2000 and December 2021 reporting the effects of IET on resting BP and at least one secondary mechanistic parameter following a short-term intervention (2-12 weeks). Eighteen studies with a pooled sample size of 628 participants were included in the final analysis. IET produced significant reductions in resting systolic and diastolic BP of 9.35 mmHg (95% confidence interval [CI] = -7.80 to -10.89, P < 0.001) and 4.30 mmHg (CI = -3.01 to -5.60, P < 0.001), respectively. Mechanistically, IET produced a statistically significant reduction in resting heart rate (mean difference [MD]: -1.55 bpm, CI = -0.14 to -2.96, P = 0.031) and a significant increase in stroke volume (MD: 6.35 ml, CI = 0.35 to 12.60, P = 0.038), with no significant change in cardiac output. Conversely, total peripheral resistance (TPR) significantly decreased following IET (MD: -100.38 dyne s -1 cm 5 , CI = -14.16 to -186.61, P = 0.023), with significant improvements in the low frequency to high frequency heart rate variability ratio (MD: -0.41, CI = -0.09 to -0.73, P = 0.013) and baroreceptor reflex sensitivity (MD: 7.43 ms/mmHg, P < 0.001). This work demonstrates that a reduction in TPR, potentially mediated through enhanced autonomic vasomotor control, is primarily responsible for BP reductions following IET. Furthermore, this novel analysis suggests wall squat interventions to be the most effective IET mode, with clinically relevant differences in BP reductions compared to handgrip and leg extension IET; although future direct comparative research is required.

Dynamic and Static Cardiac Function Measurements During Sepsis.

Dynamic and Static Cardiac Function Measurements During Sepsis.

Зміни центральної гемодинаміки у період раннього відновлення після різних режимів фізичного навантаження

We studied the changes in central hemodynamics in the early recovery period after physical load in 28 young men. Dynamic loading was induced using a modified Martine functional test, static loading - by maintaining on the standing dynamometer DS-200 muscle effort in the amount of 50% of maximum standing force. The change in central hemodynamic para- meters was recorded by tetrapolar thoracic impedance rheo- plethysmogram using a computerized diagnostic complex «Cardio +». Dynamic exercise during early recovery did not lead to a significant increase in heart rate, however, it caused a decrease in the resistance of resistive blood vessels and an increase in pulse blood pressure. The increase in minute blood volume in our study is mainly due to an increase in stroke volume, pointing for high functional reserves of the heart. In the case of static physical activity, the adaptive reactions of central hemodynamics and the course of the processes of early recovery of the circulatory system are radically different from similar indicators during dynamic physical activity. In subjects with a normodynamic type of response of the cardiovascular system to dynamic load, no significant changes in the minute volume of blood flow were registered at a similar volume of active muscle mass static load. In subjects with a normodynamic type of cardiovascular response to dynamic load, no significant changes in cardiac output were observed at a similar static load in terms of active muscle mass. However, during early recovery period, the total peripheral vascular resistance and systolic arterial pressure were increased. The increase in total peripheral resistance may be due to reactive hyperemia in ischemic skeletal muscle caused by increased blood flow to the capillaries after muscle relaxation and delayed outflow into the veins. The significant increase in systolic blood pressure can be explained by the mechanical obstruction of blood flow in the muscle capillaries during prolonged static contraction.

Efficacy and safety of percutaneous pulmonary artery subtotal occlusion and CTO intervention in chronic thromboembolic pulmonary hypertension

Abstract Background Balloon pulmonary angioplasty (BPA) is an emerging percutaneous therapy for patients with inoperable chronic thromboembolic pulmonary hypertension (CTEPH), and patients with mean pulmonary artery pressure (mPAP) ≤30mmHg have an excellent survival. Common vascular lesion types are ring-like stenoses (type A), web lesions (type B), subtotal occlusions (type C), chronic total occlusions (CTO, type D) and tortuous lesions (type E). Occlusive lesions (i.e. subtotal occlusions and CTOs) are most challenging. While the CTO intervention the coronary arteries remains controversial, risk and benefit of pulmonary artery occlusive lesion intervention in CTEPH has not been studied yet. We evaluated the impact of percutaneous pulmonary artery subtotal occlusion and CTO intervention on BPA treatment response. Methods 120 patients underwent 712 BPA procedures between April 2014 and October 2019. Clinical features and hemodynamics were assessed at baseline and 6–12 months after the last BPA session. Results A total of 2542 lesions were targeted; 720 occlusions (28.3%; 352 CTOs and 368 subtotal occlusions) and 1822 non-occlusion lesions (71.7%). Complications occurred in 6.0% of all procedures (severe complications in 0.4% of all procedures). 45 patients completed BPA treatment after a median of 6 (4; 10) procedures per patient. In these patients, mPAP dropped from 40.1±10.8 to 25.6±5.1mmHg (p&amp;lt;0.001), without significant change in cardiac output (5.2±1.4 to 5.5±3.1L/min, p=0.409). In the overall cohort, success rate for recanalization of occlusions was 81% (subtotal occlusions (type C lesions): 98%; CTOs (type D lesions) 50%). Number of successfully treated lesions of any type (β −0.86 [−1.19; −0.53]; p&amp;lt;0.001), number of successfully treated occlusions (β −2.17 [−3.38; −0.97]; p=0.001) and number of successfully treated non-occlusion lesions (β −0.81 [−1.25; −0.37]; p&amp;lt;0.001) emerged as predictors of relative change in mPAP. The impact on relative change in mPAP was higher for CTOs (β −5.88 [−10.49; −1.26]; p=0.014) than for subtotal occlusions (β −2.51 [−4.18; −0.83]; p=0.004). Conclusions The number of successfully treated vascular lesions predicts treatment response to BPA. The number of successfully recanalized occlusions (particularly CTOs) appears to have the strongest impact on change in mPAP, highlighting the importance of advanced BPA technique. Funding Acknowledgement Type of funding sources: None. Visual overview

Successive perioperative management of laparoscopic liver resection in the reverse Trendelenburg position for a patient with Fontan physiology: a case report

BackgroundLaparoscopic surgery for a patient with Fontan physiology is challenging because pneumoperitoneum and positive pressure ventilation could decrease venous return and the accumulated partial pressure of arterial carbon dioxide (PaCO2) could increase pulmonary vascular resistance, which might lead to disruption of the hemodynamics.Case presentationA 25-year-old man with Fontan physiology was scheduled to undergo laparoscopic liver resection for Fontan-associated liver disease (FALD) with noninvasive monitoring of cardiac output (CO) by transpulmonary thermodilution in addition to transesophageal echocardiography. The abdominal air pressure was maintained low, and we planned to switch to open abdominal surgery promptly if hemodynamic instability became apparent because of the accumulated PaCO2 or postural change. Consequently, the pneumoperitoneum had limited influence on circulatory dynamics, but central venous pressure significantly decreased with postural change to the reverse Trendelenburg position. Laparoscopic liver resection for FALD was performed successfully with no significant changes in CO and central venous saturation.ConclusionsWith strict circulation management, laparoscopic surgery for a patient with Fontan physiology can be performed safely. Comprehensive hemodynamic assessment by noninvasive transpulmonary thermodilution can provide valuable information to determine the time for shift to open abdominal surgery.

Gravity Threshold and Dose Response Relationships: Health Benefits Using a Short Arm Human Centrifuge.

PurposeIncreasing the level of gravity passively on a centrifuge, should be equal to or even more beneficial not only to astronauts living in a microgravity environment but also to patients confined to bed. Gravity therapy (GT) may have beneficial effects on numerous conditions, such as immobility due to neuromuscular disorders, balance disorders, stroke, sports injuries. However, the appropriate configuration for administering the Gz load remains to be determined.MethodsTo address these issues, we studied graded G-loads from 0.5 to 2.0g in 24 young healthy, male and female participants, trained on a short arm human centrifuge (SAHC) combined with mild activity exercise within 40–59% MHR, provided by an onboard bicycle ergometer. Hemodynamic parameters, as cardiac output (CO), stroke volume (SV), mean arterial pressure (MAP), systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) were analyzed, as well as blood gas analysis. A one-way repeated measures ANOVA and pairwise comparisons were conducted with a level of significance p < 0.05.ResultsSignificant changes in heart rate variability (HRV) and its spectral components (Class, Fmax, and VHF) were found in all g loads when compared to standing (p < 0.001), except in 1.7 and 2.0g. There were significant changes in CO, cardiac index (CI), and cardiac power (CP) (p < 0.001), and in MAP (p = 0.003) at different artificial gravity (AG) levels. Dose-response curves were determined based on statistically significant changes in cardiovascular parameters, as well as in identifying the optimal G level for training, as well as the optimal G level for training. There were statistically significant gender differences in Cardiac Output/CO (p = 0.002) and Cardiac Power/CP (p = 0.016) during the AG training as compared to standing. More specifically, these cardiovascular parameters were significantly higher for male than female participants. Also, there was a statistically significant (p = 0.022) gender by experimental condition interaction, since the high-frequency parameter of the heart rate variability was attenuated during AG training as compared to standing but only for the female participants (p = 0.004).ConclusionThe comprehensive cardiovascular evaluation of the response to a range of graded AG loads, as compared to standing, in male and female subjects provides the dose-response framework that enables us to explore and validate the usefulness of the centrifuge as a medical device. It further allows its use in precisely selecting personalized gravity therapy (GT) as needed for treatment or rehabilitation of individuals confined to bed.

Measurements of Cardiac Output and Management of Blood Transfusions During Burn Surgery-An Observational Prospective Study.

Burn surgery can cause extensive bleeding, which lead to perioperative blood transfusions. The purpose of this study was to investigate whether blood transfusions during burn surgery, guided by standard monitoring with inspection of the operative field, measurements of blood pressure, heart rate, hourly diuresis, and concentrations of hemoglobin and lactate could sustain the preoperative cardiac output (CO) till end of surgery. We investigated 15 patients ≥18 years of age scheduled for burn surgery, where the perioperative monitoring included an arterial line. After induction of anesthesia and before start of surgery, we measured baseline values of CO with the minimally invasive LiDCOrapid, mean arterial pressure, and concentrations of hemoglobin and lactate in arterial blood. We measured these values every 30 minutes through surgery. The primary outcome was change in CO from baseline till end of surgery. Secondary outcomes included the change in concentrations of hemoglobin and lactate from baseline till end of surgery. We found no statistically significant change in CO from baseline till end of surgery (6.6 [±2.4] liters/min; 7.2 [±3.2] liters/min; P = .26). We found a statistically significant decrease in concentration of hemoglobin (7.2 [±0.8] mmol/liter; 6.2 [±0.9] mmol/liter; P = .0002), and a statistically significant increase in concentration of lactate (1.3 [±0.5] mmol/liter; 1.7 [±1] mmol/liter; P = .02). The perioperative blood transfusion guided by standard monitoring seemed to sustain CO from baseline till end of surgery; however, further research is needed to confirm this.

Edible additive effects on zebrafish cardiovascular functionality with hydrodynamic assessment

Food coloring is often used as a coloring agent in foods, medicines and cosmetics, and it was reported to have certain carcinogenic and mutagenic effects in living organisms. Investigation of physiological parameters using zebrafish is a promising methodology to understand disease biology and drug toxicity for various drug discovery on humans. Zebrafish (Danio rerio) is a well-acknowledged model organism with combining assets such as body transparency, small size, low cost of cultivation, and high genetic homology with humans and is used as a specimen tool for the in-vivo throughput screening approach. In addition, recent advances in microfluidics show a promising alternative for zebrafish manipulation in terms of drug administration and extensive imaging capability. This pilot work highlighted the design and development of a microfluidic detection platform for zebrafish larvae through investigating the effects of food coloring on cardiovascular functionality and pectoral fin swing ability. The zebrafish embryos were exposed to the Cochineal Red and Brilliant Blue FCF pigment solution in a concentration of (0.02‰, 0.2‰) cultured in the laboratory from the embryo stage to hatching and development until 9 days post fertilization (d.p.f.). In addition, zebrafish swimming behaviors in terms of pectoral fin beating towards the toxicity screening were further studied by visualizing the induced flow field. It was evidenced that Cochineal Red pigment at a concentration of 0.2‰ not only significantly affected the zebrafish pectoral fin swing behavior, but also significantly increased the heart rate of juvenile fish. The higher concentration of Brilliant Blue FCF pigment (0.2%) increased heart rate during early embryonic stages of zebrafish. However, zebrafish exposed to food coloring did not show any significant changes in cardiac output. The applications of this proposed platform can be further extended towards observing the neurobiological/hydrodynamic behaviors of zebrafish larvae for practical applications in drug tests.

Effects of rapid and progressive ascent to Tibet plateau on cardiovascular function and stress factors of pre-selected expeditioners for Chinese Antarctic expedition for Kunlun station

Objective: To explore the different effects of rapid and progressive ascent to Tibet plateau on cardiovascular function and stress factors in pre-selected expeditioners for the 31st, 32nd and 33rd Chinese Antarctic expedition for inland station, to provide a scientific basis for the selection of qualified expeditioners. Methods: A total of 85 pre-selected expeditioners for the 31st, 32nd and 33rd Chinese Antarctic expedition for Kunlun station were enrolled in this study. According to the different manners of entering the plateau, they were divided into the rapid ascent group by aircraft (RAG, n=55) and the progressive ascent group by train (PAG, n=30). Hemodynamics and electrocardiogram were examined at 4 m (Shanghai), areas at altitude of 3 658 m (Lhasa) and 4 300 m(Yangbajain), respectively. Saliva levels of stress factors, including testosterone (T), cortisol (COR) and immunoglobulin A (IgA), were tested by ELISA. Results: The heart rates (HR) were increased significantly, while the SpO2 was decreased significantly in the two groups within 24 hours at altitudes of 3 658 m and 4 300 m (P＜0.05), while there was no significant difference between the two groups at the same altitude. Compared with 4 m, the blood pressure (BP) of the two groups at 3 658 m and 4 300 m was significantly increased (P＜0.05), and some indexes of myocardial contraction and pumping function were significantly reduced (P＜0.05). However, due to the increase of HR, there was no significant change in Cardiac Output (CO). At 4 300 m, the Thoracic Fluid Content (TFC) of the rapid ascent group was significantly higher than that of the progressive ascent group (P＜0.05). Compared with 4m, there was no significant difference in salivary testosterone change between the two groups at 3 658 m above sea level (P＞0.05), while COR and IgA changes in the rapid ascent group were significantly higher than those in another group (P＜0.05). Conclusion: Compared with the progressive ascent by train,expeditioners that rapid ascent to high altitude have significant effects on cardiovascular function and the stress hormones and immunoglobulin levels in saliva. It's suggested that hypoxia adaptation before Antarctic expediting for Kunlun Station could ensure the selected expeditioners' physical and psychological health, so that the mission could be finished smoothly.

Volumetric Capnography Monitoring and Effects of Epinephrine on Volume of Carbon Dioxide Elimination during Resuscitation after Cardiac Arrest in a Swine Pediatric Ventricular Fibrillatory Arrest.

The aim of this study was to examine the use of volumetric capnography monitoring to assess cardiopulmonary resuscitation (CPR) effectiveness by correlating it with cardiac output (CO), and to evaluate the effect of epinephrine boluses on both end-tidal carbon dioxide (EtCO 2 ) and the volume of CO 2 elimination (VCO 2 ) in a swine ventricular fibrillation cardiac arrest model. Planned secondary analysis of data collected to investigate the use of noninvasive monitors in a pediatric swine ventricular fibrillation cardiac arrest model was performed. Twenty-eight ventricular fibrillatory arrests with open cardiac massage were conducted. During CPR, EtCO 2 and VCO 2 had strong correlation with CO, measured as a percentage of baseline pulmonary blood flow, with correlation coefficients of 0.83 ( p < 0.001) and 0.53 ( p = 0.018), respectively. However, both EtCO 2 and VCO 2 had weak and nonsignificant correlation with diastolic blood pressure during CPR 0.30 ( p = 0.484) (95% confidence interval [CI], -0.51-0.83) and 0.25 ( p = 0.566) (95% CI, -0.55-0.81), respectively. EtCO 2 and VCO 2 increased significantly after the first epinephrine bolus without significant change in CO. The correlations between EtCO 2 and VCO 2 and CO were weak 0.20 ( p = 0.646) (95% CI, -0.59-0.79), and 0.27 ( p = 0.543) (95% CI, -0.54-0.82) following epinephrine boluses. Continuous EtCO 2 and VCO 2 monitoring are potentially useful metrics to ensure effective CPR. However, transient epinephrine administration by boluses might confound the use of EtCO 2 and VCO 2 to guide chest compression.

Haemodynamic Effects of Pericardial Closure after Cardiac Surgery

Introduction: Whether pericardial closure should be done or not is still a debated topic. While many studies favour pericardial closure after cardiac surgery, many are still not in favour of the same. Objective : Objective of this study was to analyse the changes induced by pericardial closure on the haemodynamic of the patient using easily measurable variables. Methods : Data of 30 patients were analysed of which 14 underwent mitral valve replacement, 10 underwent coronary artery bypass grafting and 6 underwent double valve replacement. Results: There was statistically significant change in cardiac output (p&lt;0.01), central venous pressure (p&lt;0.05) and left ventricular end diastolic diameter (p&lt;0.01) after pericardial closure. Clinically the pericardial closure was well tolerated. Conclusion: Despite exhaustive experience, the topic of closing pericardium is still debated. Our study shows that clinically pericardial closure is well tolerated and in return it also safeguards the risks associated with re-do operations

Exercise is feasible in patients receiving vasoactive medication in a cardiac surgical intensive care unit: A prospective observational study

BackgroundPatients may require vasoactive medication after cardiac surgery. The effect and safety profile of exercise on haemodynamic parameters in these patients is unclear. ObjectivesThe objective of this study was to measure the effect of upright positioning and low-level exercise on haemodynamic parameters in patients after cardiac surgery who were receiving vasoactive therapy and to determine the incidence of adverse events. MethodsThis was a prospective, single-centre, observational study conducted in an adult intensive care unit of a tertiary, cardiothoracic university–affiliated hospital in Australia. The Flotrac-Vigileo™ system was used to measure haemodynamic changes, including cardiac output, cardiac index, and stroke volume. Normally distributed variables are presented as n (%) and mean (standard deviation), and non-normally distributed variables are presented as median [interquartile range]. ResultsThere were a total of 20 participants: 16 (80%) male, with a mean age of 65.9 (10.6) years. Upright positioning caused significant increases (p = 0.018) in the mean arterial pressure (MAP), with MAP readings increasing from baseline (supine), from 72.31 (11.91) mmHg to 77.44 (9.55) mmHg when back in supine. There were no clinically significant changes in cardiac output, heart rate, stroke volume, or cardiac index with upright positioning. The incidence of adverse events was low (5%). The adverse event was transient hypotension of low severity. ConclusionsLow-level exercise in patients after cardiac surgery receiving vasoactive medication was well tolerated with a low incidence of adverse events and led to significant increases in MAP. Upright positioning and low-level exercise appeared safe and feasible in this patient cohort.

Effects of dobutamine on cardiovascular function and oxygen delivery in standing horses.

Dobutamine is routinely used to improve cardiovascular function in anaesthetized horses. However, dobutamine in conscious horses is insufficiently investigated. Ten research horses that were already instrumented for a preceding trial were included into the study. Cardiovascular variables were recorded and blood samples taken after instrumentation (Baseline), before starting dobutamine and after 10min of dobutamine infusion (2µgkg-1 min-1 ). A significant increase in systemic blood pressure, mean pulmonary artery pressure and right atrial pressure, and a decrease in heart rate were observed with dobutamine compared with baseline measurements. Arterial and mixed venous haemoglobin and oxygen content, as well as mixed venous partial pressure of oxygen increased. No significant changes in cardiac output, stroke volume, systemic vascular resistance, arterial partial pressure of oxygen, or oxygen consumption, delivery and extraction ratio were detected. Concluding, dobutamine increased systemic blood pressure without detectable changes in stroke volume, cardiac output or systemic vascular resistance in conscious horses.

P6325Gas exchange improvements during exercise correlate with hemodynamic changes in heart failure patients with a left ventricular assist device

Abstract Background The implantation of left ventricular assist devices (LVAD) has established its role in therapy for patients with end stage heart failure. Benefits in survival as well as an improved quality of life, compared to optimized medical therapy (OMT) alone, has been proven. There are limited data in the literature on the metabolic changes during exercise in LVAD patients, and in most studies no increase in peak oxygen consumption on cardiopulmonary exercise test (CPET) could be shown early after surgery. However, recent data suggests an improvement in peak oxygen uptake (VO2) as a late effect after rehabilitation. To further investigate these findings we sought to analyse CPET data from patients before LVAD implantation as well as in the early and late follow up in correlation with hemodynamic changes at these times. Methods We collected and retrospectively analysed data of heart failure patients who had undergone LVAD implantation, and in whom a right heart catheterization, a cardiopulmonary exercise test and an echocardiography had been performed at time before, as well as 6 Months and 12 months after LVAD implantation, respectively. Results Data of 43 patients implanted with an LVAD between 2011 and 2017 were analysed. There was significant improvement in cardiac output (3,2 vs 4,3 L/min, p&lt;0,001) and VE/VCO2 slope (46 vs 38, p=0,001) 6 months after LVAD implant as well as a significant reduction in PCWP (26 vs 11 mmHg, p&lt;0,001), PAP mean (40 vs 22 mmHg, p&lt;0,001), RA mean (12 vs 8 mmHg, p=0,002) and PVR (4,2 vs 2,5 WU, p&lt;0,001). However, there was no significant increase in peak VO2 after 6 months. 12 months after LVAD implantation there were no further significant changes in cardiac output, intracardiac pressures or VE/VCO2 slope, which all remained similar to the 6 months follow up. However, at that point, a significant increase in peak VO2 was seen, compared to baseline (1060 vs 1410ml/min, p=0,001) and to 6 months after surgery (Figure 1). Conclusion Cardiac output increases in heart failure patients early after LVAD implantation. Consequently, permanent ventricular off loading results in the reduction of intracardiac pressures and improvement in the VE/VCO2 slope 6 months after surgery. However, a significant rise in peak oxygen consumption could only be noted 12 months after surgery, suggesting either a delayed long-term effect of improved hemodynamics or other causes such as enhanced mobility or training due to improved quality of life.

Acute Metabolomic Changes after Implantation of a Left Ventricular Assist Device

Purpose Implantation of a left ventricular assist device (LVAD) is associated with a significant change in cardiac output for patients with severe heart failure. We hypothesized that this abrupt change circulatory flow would be associated with acute metabolic changes related to tissue oxygen delivery. Methods We enrolled 32 patients in a prospective observational cohort study undergoing elective LVAD placement at the University of Colorado from 2013 to 2017 and collected blood immediately before surgery and 24 hours post-operatively and performed clinical follow up for a minimum of 1 year. We performed UHPLC-MS based metabolomics to quantify 24 metabolites with heavy isotope labelled standards and measured an additional 91,413 features with a minimum signal to noise ratio of 3 and minimum relative ion intensity of 1000. We performed the statistical analysis with JMP v14 and for the metabolomics analysis we report false discovery rate corrected p values. Results Subsequent heart transplantation significantly increased survival in patients undergoing elective LVAD placement (Table 1). After surgery, we noted significant changes in patients’ metabolomic profile with glutamate decreasing and kynurenine and leucine/isoleucine increasing. We also identified 6941 out of 91,413 features with an FDR corrected p value less 0.05 that were significantly different between the pre-surgery and post-surgery samples (Figure 1) Conclusion LVAD placement resulted in significant metabolomic changes after 24 hours. Subsequent analyses have the potential to identify metabolomic profiles that predict clinical outcomes or guide therapies.

Haemodynamic Tolerance of Cardiac Surgical Patients Receiving Vasoactive Therapy in Upright Positioning

Introduction: There is a lack of consensus regarding when it is safe to commence exercise with cardiac surgical patients in the Intensive Care Unit (ICU) receiving vasoactive therapy. Patients receiving vasoactive therapy may therefore be subject to unnecessary bed rest. Objectives: The aims were to measure the effect of exercise in upright positioning on haemodynamic parameters of cardiac surgical patients receiving vasoactive therapy, to clarify what level of vasoactive medication may allow safe exercise, and determine the incidence of adverse events. Methods: This was a prospective, single-centre, cohort study conducted in the ICU of a cardiothoracic tertiary, university-affiliated hospital in Australia. Eligible participants were recruited from August 2017 to May 2018. The Flotrac-Vigileo system was utilized to obtain haemodynamic measurements. Subjects were progressively positioned from supine, standing and marching on spot and returned to supine. A between-within repeated measures ANOVA was conducted to compare haemodynamic variables over various positions and interactions with positions and dose of low vs medium to high levels of vasoactive medication. Results: 20 participants; 16 (80%) male; mean age of 65.9 (10.6) years; were studied, with 6 (30%) receiving low dose vasoactive medication and 14 (70%) receiving a moderate to high dose. There were significant increases in mean arterial pressure (MAP) (p = 0.018), heart rate (HR) (p = 0.050) and respiratory rate (RR) (p = 0.049) with upright positioning. There was no significant interaction between position and dose. There were no significant changes in cardiac output, stroke volume or cardiac index during upright positioning. One minor adverse event occurred in a participant on low dose Dopamine. This was a transient decrease in MAP. Conclusions: Exercise caused an increase in MAP, HR and RR, and led to no significant increases in other hemodynamic parameters. Our findings suggest that vasoactive therapy alone should not be considered a contraindication to exercise post-cardiac surgery.

Pharmacokinetics of intramuscular alfaxalone and its echocardiographic, cardiopulmonary and sedative effects in healthy dogs.

The pharmacokinetics and the effects of a single intramuscular (IM) dose of alfaxalone on sedation and cardiopulmonary and echocardiographic variables was studied in dogs. Twelve healthy adult Beagles (3 females, 9 males) were used in this prospective controlled cross-over trial. Echocardiography was performed with and without 4 mg kg-1 alfaxalone IM with a week wash-out interval. Sedation (19-point scale; 0 = no sedation), cardiopulmonary parameters, blood gas analysis and plasma concentration of alfaxalone were assessed every 5 minutes following the injection (T0). The influence of the alfaxalone plasma concentration and time on physiological variables was tested using a linear model whereas echocardiographic measurements were compared between conscious and alfaxalone-administered dogs using paired t-tests. Compared to baseline, alfaxalone administration was followed by an increase in heart rate (HR) from T5 to T30 and a decrease in mean arterial pressure (MAP) at T10, T25 and T30, in stroke volume (SV; 15 ± 5 to 11 ± 3 ml; P<0.0001), and end-diastolic volume (EDV; 24.7 ± 5.7 to 19.4 ± 4.9 ml). Cardiac output (CO) and blood gas analysis did not change significantly throughout. Mean plasma half-life was 29 ± 8 minutes, volume of distribution was 1.94 ± 0.63 L kg-1, and plasma clearance was 47.7 ± 14.1 ml kg-1 minute-1. Moderate to deep sedation was observed from T5 to T35. Ten dogs showed paddling, trembling, nystagmus and strong reaction to sound during the procedure. Although there were no significant changes in CO and oxygenation, the impact of HR, MAP, SV, EDV alterations requires further investigations in dogs with cardiac disease.

Hemodynamic Effects of the Light Stabilizer Tinuvin 770 in Dogs In Vivo.

Introduction:Tinuvin 770 [bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, Ciba-Geigy, Basel, Switzerland] is a UV light stabilizer that is a component of many plastic materials used world-wide in the medical and food industries. We report on the acute hemodynamic effects of Tinuvin 770 examined in dogs.Materials and Methods:Tinuvin 770 was dissolved in a mixture of saline and ethanol (1:1 v/v) and was administered to 12 intravenously narcotized and respirated dogs in increasing doses (T1-T7: 1, 3.3, 6.6, 10, 33.3, 66.6 and 100 mg, respectively). The doses were given as bolus injections over a three minute period, and the effects were recorded for 12 minutes. The vehicle was used as a control. Hemodynamic parameters (heart rate, blood pressure, end-diastolic pressure, dp/dt, cardiac output) and ECG were monitored continously.Results:At doses T1-T4, systolic and diastolic blood pressures, mean pressure and ventricular contractility were significantly decreased without significant changes in cardiac output, heart rate, or PQ interval. At doses T5 and T6, declines in blood pressure and myocardial contractility were observed. At doses T6 and T7, heart rate and PQ interval decreased substantially. Irreversible circulatory failure occured in one dog after administering dose T6 and in 8 dogs following dose T7.Conclusion:Tinuvin 770 induces acute hemodynamic alterations. In lower doses, it causes peripheral vasodilatation, however at higher doses acute cardiac failure occured. Plastics containing Tinuvin 770 should be used with care in medical practice and the laboratory.

Cardiovascular and respiratory effects of lumbosacral epidural bupivacaine in isoflurane-anesthetized dogs: The effects of two volumes of 0.25% solution.

The purpose of this study was to compare cardiovascular and respiratory effects of two volumes of bupivacaine 0.25% (0.2 mL kg-1—treatment BUP02—and 0.4 mL kg-1 –treatment BUP04) administered epidurally at the lumbosacral intervertebral space in dogs anesthetized with isoflurane. This experimental prospective randomized crossover design trial used six mixed breed adult dogs, four neutered males and two spayed females. Each dog was anesthetized on three different occasions: the first for isoflurane minimum alveolar concentration (MAC) measurement, and the following two assigned treatments (BUP02 or BUP04). On the two treatment days, anesthesia was induced and maintained with isoflurane at 1.3 MAC during the experiments. Cardiovascular and respiratory measurements were recorded before (T0) and 5, 15, 30, 60 and 90 minutes after the epidural administration of bupivacaine. Comparisons between and within groups were performed by a mixed-model ANOVA and Friedman’s test when appropriate followed by Bonferroni post-hoc test or Dunnet’s test to compare time points within each treatment with T0 (p < 0.05). Mean arterial pressure decreased significantly from 15 to 90 minutes after the administration of BUP02 and from 5 to 60 minutes in BUP04, with lower values in BUP04 than in BUP02 lasting up to 30 minutes after bupivacaine administration. No significant changes in cardiac output and systemic vascular resistance were observed in either treatment. Hypoventilation was only detected in BUP04. Hemoglobin concentration and arterial oxygen content decreased after both treatment of bupivacaine with no significant decrease in oxygen delivery. Two dogs in BUP04 developed Horner’s syndrome. The epidural administration of 0.4 mL.kg-1 of bupivacaine to dogs in sternal recumbency anesthetized with isoflurane 1.3 MAC caused more cardiovascular and respiratory depression than 0.2 mL.kg-1.

Effects of 8 Weeks' Training on Systemic and Muscle Oxygen Dynamics in University Rugby Players.

The aim of this study was to investigate the effects of 8 weeks of training on O2 dynamics in university rugby players. University rugby players (n = 15) participated in 5 strength training sessions and 4 field-based training sessions per week for 8 weeks. Before and after 8-weeks' training, the subjects performed ramp cycling exercise until exhaustion. Muscle O2 saturation (SmO2), relative changes from rest in deoxygenated hemoglobin concentration (∆Deoxy-Hb) and total hemoglobin concentration, cardiac output (CO), and pulmonary O2 uptake (VO2) were monitored continuously during exercise. Peak VO2 and CO were normalized by fat-free mass. Though peak VO2 tended to be increased after training, there were no significant changes in CO, nor any muscle O2 dynamic variables at peak exercise between before and after training. However, an increase in peak VO2 was significantly correlated with diminishment of deoxy-Hb and an increase in SmO2. Changes in CO caused by training were not related to improved peak VO2. The improvement of peak VO2 during 8 weeks of rugby training may have been caused by muscle O2 supply, rather than increased CO or muscle O2 extraction.