Changes In Cardiac Output Research Articles

Bilateral nephrectomy impairs cardiovascular function and cerebral perfusion in a rat model of acute hemodilutional anemia.

Anemia and renal failure are independent risk factors for perioperative stroke, prompting us to assess the combined impact of acute hemodilutional anemia and bilateral nephrectomy (2Nx) on microvascular brain Po2 (PBro2) in a rat model. Changes in PBro2 (phosphorescence quenching) and cardiac output (CO, echocardiography) were measured in different groups of anesthetized Sprague-Dawley rats (1.5% isoflurane, n = 5-8/group) randomized to Sham 2Nx or 2Nx and subsequently exposed to acute hemodilutional anemia (50% estimated blood volume exchange with 6% hydroxyethyl starch) or time-based controls (no hemodilution). Outcomes were assessed by ANOVA with significance assigned at P < 0.05. At baseline, 2Nx rats demonstrated reduced CO (49.9 ± 9.4 vs. 66.3 ± 19.3 mL/min; P = 0.014) and PBro2 (21.1 ± 2.9 vs. 32.4 ± 3.1 mmHg; P < 0.001) relative to Sham 2Nx rats. Following hemodilution, 2Nx rats demonstrated a further decrease in PBro2 (15.0 ± 6.3 mmHg, P = 0.022). Hemodiluted 2Nx rats did not demonstrate a comparable increase in CO after hemodilution compared with Sham 2Nx (74.8 ± 22.4 vs. 108.9 ± 18.8 mL/min, P = 0.003) that likely contributed to the observed reduction in PBro2. This impaired CO response was associated with reduced fractional shortening (33 ± 9 vs. 51 ± 5%) and increased left ventricular end-systolic volume (156 ± 51 vs. 72 ± 15 µL, P < 0.001) suggestive of systolic dysfunction. By contrast, hemodiluted Sham 2Nx animals demonstrated a robust increase in CO and preserved PBro2. These data support the hypothesis that the kidney plays a central role in maintaining cerebral perfusion and initiating the adaptive increase in CO required to optimize PBro2 during acute anemia.NEW & NOTEWORTHY This study has demonstrated that bilateral nephrectomy acutely impaired cardiac output (CO) and microvascular brain Po2 (PBro2), at baseline. Following acute hemodilution, nephrectomy prevented the adaptive increase in CO associated with acute hemodilution leading to a further reduction in PBro2, accentuating the degree of cerebral tissue hypoxia. These data support a role for the kidney in maintaining PBro2 and initiating the increase in CO that optimized brain perfusion during acute anemia.

Invasive haemodynamics at rest and exercise in cardiac amyloidosis.

Our aim was to investigate haemodynamics at rest and during exercise in patients with transthyretin cardiomyopathy (ATTR-CM) in light of the 2022 European Society of Cardiology (ESC) and European Respiratory Society (ERS) guidelines on pulmonary hypertension (PH). We performed right heart catheterization (RHC) in 57 subjects with ATTR-CM. The proportion of patients with PH was 77% according to the 2022 guidelines versus 47% when applying the 2015 guidelines. Isolated post-capillary PH and combined pre- and post-capillary PH were most prevalent. Thirty-six patients underwent a supine bicycle cardiopulmonary exercise test during RHC. Exercise-induced PH was defined as an increase in mean pulmonary arterial pressure from rest to exercise per increase in cardiac output (ΔmPAP/ΔCO) of > 3mmHg/L/min. An increase in pulmonary arterial wedge pressure per change in cardiac output (ΔPAWP/ΔCO) from rest to exercise >2mmHg/L/min was considered suggestive of post-capillary exercise-induced PH. All but two patients who exercised during RHC developed exercise-induced PH. The median ΔmPAP/ΔCO was 7.2mmHg/L/min and ΔPAWP/ΔCO was 5.1mmHg/L/min. The median ΔRAP/ΔCO was 3.6mmHg/L/min and ΔRAP/ΔPAWP was 0.6mmHg/L/min. Most patients with ATTR-CM have isolated post-capillary or combined pre- and post-capillary PH at rest, and almost all patients develop exercise-induced PH with a large post-capillary component. There was a pronounced, but balanced increase in atrial pressures on exercise.

Challenge or Threat? The Effects of the Standard and a Second-Generation Mindfulness Intervention with Buddhist Practices on Cognitive Appraisals of Stress: Secondary Analysis of a Randomized Controlled Experiment Performed in Switzerland.

Contemplative approaches rooted in Buddhist traditions have been linked to the attenuation of response to social stress. Anticipatory cognitive appraisals of social situations potentially represent a mechanism explaining the stress-reducing effects of contemplative practices. The cognitive appraisal of threat is associated with an anticipated loss of social self-esteem. In contrast, the cognitive appraisal of challenge involves recognizing the potential for gain or growth in stressful situations and is associated with a more adaptive cardiovascular response. In this secondary analysis of a randomized controlled experiment performed in Switzerland, we evaluated the effects of two contemplative interventions on cognitive appraisals of challenge and threat and associated physiological profiles. The interventions were a standard Mindfulness-Based Stress Reduction (MBSR) program and a new program (MBSR-B), which included several elements from Buddhist practices. After an eight-week intervention, participants completed the Trier Social Stress Test (TSST) and underwent the assessment of primary cognitive appraisals and cardiovascular response to stress. The results demonstrated greater challenge appraisal in the MBSR (n = 20) and MBSR-B (n = 21) groups compared to Control (n = 24), and MBSR-B participants scored higher on the challenge than threat appraisal. At the physiological level, the groups did not differ on changes in cardiac output and total peripheral resistance. Still, an exploratory analysis demonstrated that the MBSR-B group's cardiovascular profile best resembled challenge appraisal. The results suggest that contemplative approaches foster challenge appraisal, contributing to a more adaptive response to stress.

Effects of empagliflozin on right ventricular adaptation to pressure overload.

Right ventricular (RV) failure is the prime cause of death in patients with pulmonary arterial hypertension. Novel treatment strategies that protect the RV are needed. Empagliflozin, a sodium-glucose co-transporter-2 inhibitor, shows cardioprotective effects on the left ventricle in clinical and preclinical studies, but its direct effects on RV remain elusive. We investigated the effects of empagliflozin on RV dysfunction induced by pulmonary trunk banding (PTB). Male Wistar rats (116 ± 10 g) were randomized to PTB or sham surgery. One week after surgery, PTB animals received empagliflozin mixed into the chow (300 mg empagliflozin/kg chow; PTB-empa, n = 10) or standard chow (PTB-control, n = 10). Sham rats (Sham, n = 6) received standard chow. After five weeks, RV function was evaluated by echocardiography, cardiac MRI, and invasive pressure-volume measurements. PTB caused RV failure evident by decreased cardiac output compared with sham. PTB-empa rats had a 49% increase in water intake compared with PTB-control yet no differences in hematocrit or blood glucose. Treatment with empagliflozin decreased RV end-systolic pressures without any changes in RV cardiac output or ventricular-arterial coupling (Ees/Ea). The decrease in RV end-systolic pressure was complemented by a slight reduction in RV cross sectional area as a sign of reduced hypertrophy. Load-independent measures of RV systolic and diastolic function were not affected in PTB-empa rats compared with PTB-control. Empagliflozin treatment reduced RV end-systolic pressure in RV failure induced by pressure overload. Further studies are needed to elucidate whether this simply relates to a diuretic effect and/or additional independent beneficial RV effects.

Is crystalloid co-loading necessary to prevent spinal hypotension during elective cesarean delivery? A randomized double-blind trial

BackgroundHypotension is common during spinal anesthesia for cesarean delivery. Preventive strategies include fluid loading and phenylephrine. We hypothesized that if prophylactic phenylephrine infusion is used, omission of fluid loading would be non-inferior to fluid co-loading in maintaining cardiac output. We assumed that if there was a difference, the increase in cardiac output would be greater in the no-loading than in the co-loading group. MethodsTerm pregnant women scheduled for elective cesarean delivery were randomized to receive 1 L crystalloid co-loading or maintenance fluids only. Phenylephrine was titrated to maintain blood pressure. Changes in cardiac output following spinal anesthesia were the primary outcome. The study was powered as a non-inferiority trial, allowing the no-loading arm to have a 50% greater change in cardiac output. Heart rate, dose of phenylephrine, occurrence of nausea and vomiting, Apgar scores and neonatal acid base status were secondary outcomes. ResultsData from 63 women were analyzed. In contrast to our hypothesis, there was 33% less increase in cardiac output with no loading (ratio 0.67, 95% CI 0.15 to 1.36), and 60% greater reduction of cardiac output with no loading (ratio 1.6, 95% CI 1.0 to 2.7). Total dose of phenylephrine was higher in the no-loading group. There may be a less favorable neonatal acid base status without volume loading. ConclusionOmission of crystalloid co-loading leads to a decrease in cardiac output which has a potentially unfavorable impact on neonatal acid base status. We conclude that crystalloid co-loading may be useful in the presence of phenylephrine infusion.

Hemodynamic effects of supplemental oxygen versus air in simulated blood loss in healthy volunteers: a randomized, controlled, double-blind, crossover trial

BackgroundTrauma patients frequently receive supplemental oxygen, but its hemodynamic effects in blood loss are poorly understood. We studied the effects of oxygen on the hemodynamic response and tolerance to simulated blood loss in healthy volunteers.MethodsFifteen healthy volunteers were exposed to simulated blood loss by lower body negative pressure (LBNP) on two separate visits at least 24 h apart. They were randomized to inhale 100% oxygen or medical air on visit 1, while inhaling the other on visit 2. To simulate progressive blood loss LBNP was increased every 3 min in levels of 10 mmHg from 0 to 80 mmHg or until hemodynamic decompensation. Oxygen and air were delivered on a reservoired face mask at 15 L/min. The effect of oxygen compared to air on the changes in cardiac output, stroke volume and middle cerebral artery blood velocity (MCAV) was examined with mixed regression to account for repeated measurements within subjects. The effect of oxygen compared to air on the tolerance to blood loss was measured as the time to hemodynamic decompensation in a shared frailty model. Cardiac output was the primary outcome variable.ResultsOxygen had no statistically significant effect on the changes in cardiac output (0.031 L/min/LBNP level, 95% confidence interval (CI): − 0.015 to 0.077, P = 0.188), stroke volume (0.39 mL/LBNP level, 95% CI: − 0.39 to 1.2, P = 0.383), or MCAV (0.25 cm/s/LBNP level, 95% CI: − 0.11 to 0.61, P = 0.176). Four subjects exhibited hemodynamic decompensation when inhaling oxygen compared to 10 when inhaling air (proportional hazard ratio 0.24, 95% CI: 0.065 to 0.85, P = 0.027).ConclusionsWe found no effect of oxygen compared to air on the changes in cardiac output, stroke volume or MCAV during simulated blood loss in healthy volunteers. However, oxygen had a favorable effect on the tolerance to simulated blood loss with fewer hemodynamic decompensations. Our findings suggest that supplemental oxygen does not adversely affect the hemodynamic response to simulated blood loss.Trial registration This trial was registered in ClinicalTrials.gov (NCT05150418) December 9, 2021

Cardiac output, cerebral blood flow and cognition in patients with severe aortic valve stenosis undergoing transcatheter aortic valve implantation: design and rationale of the CAPITA study.

Approximately one-third of patients with symptomatic severe aortic valve stenosis who are scheduled for transcatheter aortic valve implantation (TAVI) have some degree of cognitive impairment. TAVI may have negative cognitive effects due to periprocedural micro-emboli inducing cerebral infarction. On the contrary, TAVI may also have positive cognitive effects due to increases in cardiac output and cerebral blood flow (CBF). However, studies that systematically assess these effects are scarce. Therefore, the main aim of this study is to assess cerebral and cognitive outcomes in patients with severe aortic valve stenosis undergoing TAVI. In the prospective CAPITA (CArdiac OutPut, Cerebral Blood Flow and Cognition In Patients With Severe Aortic Valve Stenosis Undergoing Transcatheter Aortic Valve Implantation) study, cerebral and cognitive outcomes are assessed in patients undergoing TAVI. One day before and 3months after TAVI, patients will undergo echocardiography (cardiac output, valve function), brain magnetic resonance imaging (CBF, structural lesions) and extensive neuropsychological assessment. To assess longer-term effects of TAVI, patients will again undergo echocardiography and neuropsychological assessment 1year after the procedure. The co-primary outcome measures are change in CBF (in ml/100 g per min) and change in global cognitive functioning (Z-score) between baseline and 3‑month follow-up. Secondary objectives include change in cardiac output, white matter hyperintensities and other structural brain lesions. (ClinicalTrials.gov identifier NCT05481008) CONCLUSION : The CAPITA study is the first study designed to systematically assess positive and negative cerebral and cognitive outcomes after TAVI. We hypothesise that TAVI improves cardiac output, CBF and cognitive functioning.

Internal Carotid Artery Blood Flow Response to Anaesthesia, Pneumoperitoneum and Head-Up Tilt During Laparoscopic Cholecystectomy: A Clinical Study

Background: Control of cerebral blood flow (CBF) is complex and is only beginning to be elucidated. There is paucity of information on how implementation of pneumoperitoneum and head-up tilt under general anaesthesia affects CBF. This study was designed to observe changes that occur in the internal carotid artery (ICA) blood flow with pneumoperitoneum and head-up position and corelate these changes with changes in cardiac output in patients undergoing laparoscopic cholecystectomy.Methods: ICA blood velocity and diameter was measured by Doppler ultrasound in 35 ASA grade I and II patients undergoing laparoscopic cholecystectomy, at four time points: awake, after anaesthesia induction, after induction of pneumoperitoneum, and after head-up tilt; and ICA blood flow was calculated. Simultaneously, heart rate, blood pressure, and end-tidal carbon dioxide (ETCO2) were recorded, and cardiac output was calculated.Results: ICA blood flow decreased upon anesthesia induction from 164 mL/minute to 151 ml/minute (p&gt;0.05). ICA blood flow increased with pneumoperitoneum (from 164 mL/minute to 179ml/minute p= 0.04). Head-up tilt resulted in decrease in ICA blood flow (from 164 mL/minute to 151ml/ minute, P = 0.09).Conclusion: ICA blood flow significantly increased after the creation of pneumoperitoneum in patients undergoing elective laparoscopic cholecystectomy under general anaesthesia. Induction of anaesthesia and head-up tilt, however, did not have any significant change in ICA blood flow. We suggest that ICA blood flow during anaesthesia is influenced by an interplay of actions of anaesthetic agents, positive pressure ventilation and patient position besides the changes in blood pressure, ETCO2 and cardiac output.

Cardiac Vagal Nerve Activity Increases During Exercise to Enhance Coronary Blood Flow.

The phrase complete vagal withdrawal is often used when discussing autonomic control of the heart during exercise. However, more recent studies have challenged this assumption. We hypothesized that cardiac vagal activity increases during exercise and maintains cardiac function via transmitters other than acetylcholine. Chronic direct recordings of cardiac vagal nerve activity, cardiac output, coronary artery blood flow, and heart rate were recorded in conscious adult sheep during whole-body treadmill exercise. Cardiac innervation of the left cardiac vagal branch was confirmed with lipophilic tracer dyes (DiO). Sheep were exercised with pharmacological blockers of acetylcholine (atropine, 250 mg), VIP (vasoactive intestinal peptide; [4Cl-D-Phe6,Leu17]VIP 25 µg), or saline control, randomized on different days. In a subset of sheep, the left cardiac vagal branch was denervated. Neural innervation from the cardiac vagal branch is seen at major cardiac ganglionic plexi, and within the fat pads associated with the coronary arteries. Directly recorded cardiac vagal nerve activity increased during exercise. Left cardiac vagal branch denervation attenuated the maximum changes in coronary artery blood flow (maximum exercise, control: 63.5±5.9 mL/min, n=8; cardiac vagal denervated: 32.7±5.6 mL/min, n=6, P=2.5×10-7), cardiac output, and heart rate during exercise. Atropine did not affect any cardiac parameters during exercise, but VIP antagonism significantly reduced coronary artery blood flow during exercise to a similar level to vagal denervation. Our study demonstrates that cardiac vagal nerve activity actually increases and is crucial for maintaining cardiac function during exercise. Furthermore, our findings show the dynamic modulation of coronary artery blood flow during exercise is mediated by VIP.

Effect of home-based online training and activity feedback on oxygen uptake in patients after surgical cancer therapy: a randomized controlled trial

BackgroundExercise training is beneficial in enhancing physical function and quality of life in cancer patients. Its comprehensive implementation remains challenging, and underlying cardiopulmonary adaptations are poorly investigated. This randomized controlled trial examines the implementation and effects of home-based online training on cardiopulmonary variables and physical activity.MethodsOf screened post-surgical patients with breast, prostate, or colorectal cancer, 148 were randomly assigned (1:1) to an intervention (2 × 30 min/week of strength-endurance training using video presentations) and a control group. All patients received activity feedback during the 6-month intervention period. Primary endpoint was change in oxygen uptake after 6 months. Secondary endpoints included changes in cardiac output, rate pressure product, quality of life (EORTC QoL-C30), C-reactive protein, and activity behavior.ResultsOne hundred twenty-two patients (62 intervention and 60 control group) completed the study period. Change in oxygen uptake between intervention and control patients was 1.8 vs. 0.66 ml/kg/min (estimated difference after 6 months: 1.24; 95% CI 0.23 to 2.55; p = 0.017). Rate pressure product was reduced in IG (estimated difference after 6 months: − 1079; 95% CI − 2157 to − 1; p = 0.05). Physical activity per week was not different in IG and CG. There were no significant interaction effects in body composition, cardiac output, C-reactive protein, or quality of life.ConclusionsHome-based online training among post-surgery cancer patients revealed an increase of oxygen uptake and a decrease of myocardial workload during exercise. The implementation of area-wide home-based training and activity feedback as an integral component in cancer care and studies investigating long-term effects are needed.Trial registrationDRKS-ID: DRKS00020499; Registered 17 March 2020.

Cardiac Effects of Long-Duration Space Flight

BackgroundVentricular mass responds to changes in physical activity and loading, with cardiac hypertrophy after exercise training, and cardiac atrophy after sustained inactivity. Ventricular wall stress (ie, loading) decreases during microgravity. Cardiac atrophy does not plateau during 12 weeks of simulated microgravity but is mitigated by concurrent exercise training. ObjectivesThe goal of this study was to determine whether the current exercise countermeasures on the International Space Station (ISS) offset cardiac atrophy during prolonged space flight. MethodsWe measured left ventricular (LV) and right ventricular (RV) mass and volumes (via magnetic resonance imaging) in 13 astronauts (4 females; age 49 ± 4 years), between 75 and 60 days before and 3 days after 155 ± 31 days aboard the ISS. Furthermore, we assessed total cardiac work between 21 and 7 days before space flight and 15 days before the end of the mission. Data were compared via paired-samples t-tests. ResultsTotal cardiac work was lower during space flight (P = 0.008); however, we observed no meaningful difference in LV mass postflight (pre: 115 ± 30 g vs post: 118 ± 29 g; P = 0.053), with marginally higher LV stroke volume (P = 0.074) and ejection fraction postflight (P = 0.075). RV mass (P = 0.999), RV ejection fraction (P = 0.147), and ventricular end-diastolic (P = 0.934) and end-systolic volumes (P = 0.145) were not different postflight. There were strong positive correlations between the relative change in LV mass with the relative changes in total cardiac output (r = 0.73; P = 0.015) and total cardiac work (r = 0.53; P = 0.112). ConclusionsThe current exercise countermeasures used on the ISS appear effective in offsetting reductions in cardiac mass and volume, despite overall reductions in total cardiac work, during prolonged space flight.

Effect of assessing velocity time integral at different locations across ventricular outflow tracts when calculating cardiac output in neonates

This study aims to evaluate the effect of assessing velocity time integral at different locations across ventricular outflow tracts for calculating cardiac output (CO) in neonates. Velocity time integral (VTI) and CO were measured at 3 different locations across right and left ventricular outflow tracts using transthoracic echocardiography in healthy term neonates without any major congenital heart disease. ANOVA with Bonferroni correction was used to determine the differences between the VTI and CO sampled at these three locations. Forty-one neonates met inclusion criteria with mean gestational age of 38.6 ± 1 weeks and mean birth weight of 3155 ± 463 g. The median hours after birth when echocardiography was obtained was 23 h (range 11–68 h after birth). Left CO were 121 ± 30 mL/kg/min, 155 ± 38 mL/kg/min, and 176 ± 36 mL/kg/min measured below the valve, hinges of the valve, and tip of the valve, respectively. Right CO were 197 ± 73 mL/kg/min, 270 ± 83 mL/kg/min, and 329 ± 104 mL/kg/min measured below the valve, hinges of the valve, and tip of the valve, respectively. A statistically significant difference (P < 0.001) was found in the VTI and CO measured at the 3 different locations across both left and right ventricular outflow tracts. Conclusions: There is a significant difference in measurements of VTI and CO depending on the location of Doppler gate sampling across the ventricular outflow tracts. Consistency and precision in Doppler gate location are essential for measuring VTI and calculating CO while assessing changes in hemodynamic status in critically ill infants.What is Known:• Targeted Neonatal Echocardiography is increasingly applied to measure cardiac output in critically ill neonates and serial assessments are performed to assess the trend in changes in cardiac output.• Noninvasive measurement using velocity time integral to calculate cardiac output is commonly performed. However, location of Doppler sample gate to measure ventricular outflow tract velocity time integral is not consistent.What is New:• Statistically significant changes in measured velocity time integral and cardiac output are noted based on the location of Doppler gate sampling.• To monitor the cardiac output for trending, it is important to be consistent with regards to the location of the Doppler sample gate to assess changes in cardiac output in critically ill newborns.

Efectos del reto de líquidos sobre el acople ventrículo arterial en un biomodelo porcino de choque endotóxico

Introduction: fluid challenges (FCs) consist of measuring hemodynamic response through changes in cardiac output (CO) after fluid administration, although only measuring CO proves insufficient. Ventriculo-arterial coupling (V-A) (effective arterial elastance / tele-systolic elastance: E(a)/Ets) are variables used for a comprehensive cardiac and circulatory status appraisal. Objective: to evaluate V-A in an endotoxic shock bio-model by FCs. Materials and methods: an endotoxic shock bio-model (9 pigs). Hemodynamic variables were measured every hour from time 0 (T0) to T6. Five FCs were performed between T0 and T4. Hypotension time was referred to as HT. The median differences in variables between T0-T4 were calculated. Challenges were classified into two groups according to V-A delta (post-challenge V-A - pre-challenge V-A). In ΔV-A≤0 o&gt;0, variables were measured before and after each FC. The lactate to pyruvate (L/P) ratio was determined at T0, T3 and T6. Correlations between the LP T6-T0 difference and hemodynamic variables, were established. Results: V-A increased (1.58 to 2,02, p=0.042) as Eae increased (1.74 to 2.55; p=0.017). CO (4.32 to 5.46, p=0.032) and cardiac power (CP) (0.61 to 0.77, p=0,028) increased, in the ΔV-AC≤0 group. The ΔLP correlated with the systolic and diastolic shock index (r=0.73), but not with V-A. Conclusion: V-A increased significantly during endotoxic shock. The ΔAVA≤0 group, showed elevated CO and CP during FC. ΔLP did not correlate with any of the V-A variables.

Changes in cardiac output, rhythm regularity, and symptom severity after electrical cardioversion of atrial fibrillation

Objectives Symptoms in atrial fibrillation (AF) range from none to disabling. The physiological correlates of AF symptoms are not well characterized. This study investigated the association between physiological parameters and symptom severity before and after electrical cardioversion (EC) of AF. Design We studied 44 patients with persistent AF (age 66.2 ± 7.9 years, 16% females) 4 ± 2 days before and 5 ± 2 days after EC. Physiological parameters included cardiac output (CO; non-invasive inert gas rebreathing), heart rate (HR), RR variability and resting and ambulatory blood pressure (BP). Symptoms and quality of life (QoL) were assessed by the modified European Heart Rhythm Association score (mEHRA), the Atrial Fibrillation Effect on Quality of Life (AFEQT) and the Symptom Checklist for frequency and severity of symptoms (SCL). Results 28 of 44 patients were still in sinus rhythm (SR) at post EC evaluation. Those in SR had a decreased HR (-15.4 ± 13.1 bpm, p < 0.001), and an increased CO (+0.8 ± 0.7 L/min, p < 0.001) as compared to those with recurrent AF. Changes in CO after EC correlated with symptom improvement as scored by AFEQT (r = 0.36; p < 0.05), AFEQT symptoms subscore (r = 0.46; p < 0.01), SCL for frequency (r = 0.62; p < 0.01) and severity (r = 0.33; p < 0.05) of symptoms, and the mEHRA score (r = 0.50; p < 0.01). A decrease in RR variability showed similar correlations with these measures of symptom improvement. Conclusions Improvements in symptoms and quality of life experienced by patients after electrical conversion of atrial fibrillation are correlated with an increase in CO and a decreased RR variability.

A large arteriovenous fistula steals a considerable part of systemic blood flow during veno-arterial extracorporeal circulation support in a porcine model.

Background: Veno-arterial extracorporeal membrane oxygenation (V-A ECMO) is one of the most frequently used mechanical circulatory support devices. Distribution of extracorporeal membrane oxygenation flow depends (similarly as the cardiac output distribution) on regional vascular resistance. Arteriovenous fistulas (AVFs), used frequently as hemodialysis access, represent a low-resistant circuit which steals part of the systemic perfusion. We tested the hypothesis that the presence of a large Arteriovenous fistulas significantly changes organ perfusion during a partial and a full Veno-arterial extracorporeal membrane oxygenation support. Methods: The protocol was performed on domestic female pigs held under general anesthesia. Cannulas for Veno-arterial extracorporeal membrane oxygenation were inserted into femoral artery and vein. The Arteriovenous fistulas was created using another two high-diameter extracorporeal membrane oxygenation cannulas inserted in the contralateral femoral artery and vein. Catheters, flow probes, flow wires and other sensors were placed for continuous monitoring of haemodynamics and organ perfusion. A stepwise increase in extracorporeal membrane oxygenation flow was considered under beating heart and ventricular fibrillation (VF) with closed and opened Arteriovenous fistulas. Results: Opening of a large Arteriovenous fistulas (blood flow ranging from 1.1 to 2.2L/min) resulted in decrease of effective systemic blood flow by 17%-30% (p < 0.01 for all steps). This led to a significant decrease of carotid artery flow (ranging from 13% to 25% after Arteriovenous fistulas opening) following VF and under partial extracorporeal membrane oxygenation support. Cerebral tissue oxygenation measured by near infrared spectroscopy also decreased significantly in all steps. These changes occurred even with maintained perfusion pressure. Changes in coronary artery flow were driven by changes in the native cardiac output. Conclusion: A large arteriovenous fistula can completely counteract Veno-arterial extracorporeal membrane oxygenation support unless maximal extracorporeal membrane oxygenation flow is applied. Cerebral blood flow and oxygenation are mainly compromised by the effect of the Arteriovenous fistulas. These effects could influence brain function in patients with Arteriovenous fistulas on Veno-arterial extracorporeal membrane oxygenation.

Haemodynamic effects of methoxyflurane versus fentanyl and placebo in hypovolaemia: a randomised, double-blind crossover study in healthy volunteers

BackgroundMethoxyflurane is approved for relief of moderate to severe pain in conscious adult trauma patients: it may be self-administrated and is well suited for use in austere environments. Trauma patients may sustain injuries causing occult haemorrhage compromising haemodynamic stability, and it is therefore important to elucidate whether methoxyflurane may adversely affect the haemodynamic response to hypovolaemia. MethodsIn this randomised, double-blinded, placebo-controlled, three-period crossover study, inhaled methoxyflurane 3 ml, i.v. fentanyl 25 μg, and placebo were administered to 15 healthy volunteers exposed to experimental hypovolaemia in the lower body negative pressure model. The primary endpoint was the effect of treatment on changes in cardiac output, while secondary endpoints were changes in stroke volume and mean arterial pressure and time to haemodynamic decompensation during lower body negative pressure. ResultsThere were no statistically significant effects of treatment on the changes in cardiac output, stroke volume, or mean arterial pressure during lower body negative pressure. The time to decompensation was longer for methoxyflurane compared with fentanyl (hazard ratio 1.9; 95% confidence interval 0.4–3.4; P=0.010), whereas there was no significant difference to placebo (hazard ratio −1.3; 95% confidence interval −2.8 to 0.23; P=0.117). ConclusionsThe present study does not indicate that methoxyflurane has significant adverse haemodynamic effects in conscious adults experiencing hypovolaemia. Clinical trial registrationClinicalTrials.gov (NCT04641949) and EudraCT (2019-004144-29) https://www.clinicaltrialsregister.eu/ctr-search/trial/2019-004144-29/NO.

Hemodynamic effects of a low versus a high dose of propofol during induction of anesthesia. A randomized trial.

Hypotension is common after anesthesia induction with propofol and is associated with increased morbidity. It is important to examine the effects of the proposed interventions to limit preventable hypotension, as suggested by the reduction in the dose of propofol. Our objective was to investigate whether a high dose of propofol is inferior to a low dose with respect to changes in systolic arterial blood pressure (SAP). This randomized, double-blind, dose-controlled, non-inferiority study included 68 healthy women scheduled for gynecological surgery at the Day Surgery Unit, Haugesund Hospital, Norway. The patients were randomly allocated 1:1 to a low or high dose (1.4 mg/kg total body weight (TBW) versus 2.7 mg/kg TBW of propofol corresponding to maximal effect site concentrations (Ce) of 2.0 μg/mL versus 4.0 μg/mL. The dose of remifentanil was 1.9-2.0 μg/kg TBW, with maximal Ce of 5.0 ng/mL. The patients were observed for 450 s from the start of the infusions. The first 150 s was the sedation period, after which a bolus of propofol and remifentanil was administered. Baseline was defined as 55-5 s before the bolus doses. LiDCOplus was used for invasive beat-to-beat hemodynamic monitoring of changes in SAP, heart rate (HR), cardiac output (CO), stroke volume (SV), and systemic vascular resistance (SVR). A difference of 10 mmHg in the change in SAP was considered to be clinically important. The SAP change difference for low versus high dose was -2.9 mmHg (95% CI -9.0-3.1). The relative changes for low versus high dose were SAP -31% versus -36%, (p < .01); HR -24% versus -20%, (p = .09); SVR -20% versus -31%, (p < .001); SV -16% versus -20%, (p = .04); and CO -35% versus -32%, (p = .33). A high dose of propofol was not inferior to a low dose, and a reduction in the dose of propofol did not result in clinically important attenuation of major hemodynamic changes during induction in healthy women. ClinicalTrials.gov identifier NCT03861364, January 3, 2019.

The clinical application of ultrasound for acute kidney injury during sepsis-from macroscopic to microscopic renal perfusion perspectives

The aim was to quantify macroscopic renal blood flow and renal cortical microcirculation in patients with septic acute kidney injury (AKI) using ultrasound and contrast-enhanced ultrasound. In this case-control study, patients in the intensive care unit diagnosed with septic AKI were divided into stages 1-3 based on the 2012 KDIGO (Kidney Disease: Improving Global Outcomes) AKI diagnostic criteria. The patients were categorized into mild (stage 1) and severe (stages 2 and 3) groups, while septic patients without AKI served as the control group. Ultrasound parameters such as macrovascular renal blood flow and time-averaged velocity, as well as cardiac function parameters such as cardiac output and cardiac index, were measured. The time-intensity curve in the microcirculation was analyzed through contrast-enhanced ultrasound imaging software to calculate imaging parameters such as peak time, rise time, fall half-time and mean transit time of the interlobar arteries in the renal cortex. In terms of macrocirculation, renal blood flow and time-averaged velocity decreased gradually with the progression of septic acute renal injury (p=0.004, p < 0.001). There was no difference in cardiac output and cardiac index values among the three groups (p=0.17 and p=0.12). In terms of microcirculation, ultrasonic Doppler parameters of the renal cortical interlobular artery, such as peak intensity, risk index and ratio of peak systolic velocity to end-diastolic velocity, gradually increased (all p values <0.05). The temporal contrast-enhanced ultrasound parameters-time to peak, rise time, fall half-time and mean transit time-were prolonged in AKI groups when compared with the control group (p < 0.001, p=0.003, p=0.004 and p=0.009, respectively). In patients with septic AKI, the renal blood flow and time average velocity of macrocirculation in the kidneys are reduced, while the time parameters of microcirculation such as time to peak, rise time, fall half-time and mean transit time are prolonged, especially in patients with severe AKI. These changes are not related to changes in cardiac output or cardiac index.

Design and Implementation of a Rat Ex Vivo Lung Perfusion Model.

Ex vivo lung preparations are a useful model that can be translated to many different fields of research, complementing corresponding in vivo and in vitro models. Laboratories wishing to use isolated lungs need to be aware of important steps and inherent challenges to establish a setup that is affordable, reliable, and that can be easily adapted to fit the topic of interest. This paper describes a DIY (do it yourself) model for ex vivo rat lung ventilation and perfusion to study drug and gas effects on pulmonary vascular tone, independent of changes in cardiac output. Creating this model includes a) the design and construction of the apparatus, and b) the lung isolation procedure. This model results in a setup that is more cost-effective than commercial alternatives and yet modular enough to adapt to changes in specific research questions. Various obstacles had to be resolved to ensure a consistent model that is capable of being used for a variety of different research topics. Once established, this model has proven to be highly adaptable to different questions and can easily be altered for different fields of study.

Variation in central venous oxygen saturation to evaluate fluid responsiveness: a systematic review and meta-analysis

BackgroundSince oxygen content and oxygen consumption typically remain unchanged within a short period, variation in central venous oxygen saturation (ΔScvO2) during fluid challenge can theoretically track the changes in cardiac output (CO). We conducted this meta-analysis to systematically assess the diagnostic performance of ΔScvO2 during a fluid challenge for fluid responsiveness in mechanically ventilated patients receiving volume expansion.MethodsElectronic databases were systematically searched to identify relevant studies published before October 24, 2022. As the cutoff value of ΔScvO2 was expected to vary across the included studies, we estimated the area under the hierarchical summary receiver operating characteristic curve (AUHSROC) as the primary measure of diagnostic accuracy. The optimal threshold of ΔScvO2 and the corresponding 95% confidential interval (CI) were also estimated.ResultsThis meta-analysis included 5 observational studies comprising 240 participants, of whom 133 (55%) were fluid responders. Overall, the ΔScvO2 during the fluid challenge exhibited excellent performance for defining fluid responsiveness in mechanically ventilated patients receiving volume expansion, with an AUHSROC of 0.86 (95% CI 0.83–0.89), a pooled sensitivity of 0.78 (95% CI 0.69–0.85), a pooled specificity of 0.84 (95% CI 0.72–0.91), and a pooled diagnostic odds ratio of 17.7 (95% CI 5.9–53.2). The distribution of the cutoff values was nearly conically symmetrical and concentered between 3 and 5%; the mean and median cutoff values were 4% (95% CI 3–5%) and 4% (95% CI not estimable), respectively.ConclusionsIn mechanically ventilated patients receiving volume expansion, the ΔScvO2 during the fluid challenge is a reliable indicator of fluid responsiveness.Clinical trial registration PROSPERO, https://www.crd.york.ac.uk/prospero/, registry number: CRD42022370192.