Changes In Cardiac Output Research Articles

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>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.

Exploring Sex Differences of Beta-Blockers in the Treatment of Hypertension: A Systematic Review and Meta-Analysis.

In the prevention of cardiovascular morbidity and mortality, early recognition and adequate treatment of hypertension are of leading importance. However, the efficacy of antihypertensives may be depending on sex disparities. Our objective was to evaluate and quantify the sex-diverse effects of beta-blockers (BB) on hypertension and cardiac function. We focussed on comparing hypertensive female versus male individuals. A systematic search was performed for studies on BBs from inception to May 2020. A total of 66 studies were included that contained baseline and follow up measurements on blood pressure (BP), heart rate (HR), and cardiac function. Data also had to be stratified for sex. Mean differences were calculated using a random-effects model. In females as compared to males, BB treatment decreased systolic BP 11.1 mmHg (95% CI, -14.5; -7.8) vs. 11.1 mmHg (95% CI, -14.0; -8.2), diastolic BP 8.0 mmHg (95% CI, -10.6; -5.3) vs. 8.0 mmHg (95% CI, -10.1; -6.0), and HR 10.8 beats per minute (bpm) (95% CI, -17.4; -4.2) vs. 9.8 bpm (95% CI, -11.1; -8.4)), respectively, in both sexes' absolute and relative changes comparably. Left ventricular ejection fraction increased only in males (3.7% (95% CI, 0.6; 6.9)). Changes in left ventricular mass and cardiac output (CO) were only reported in males and changed -20.6 g (95% CI, -56.3; 15.1) and -0.1 L (95% CI, -0.5; 0.2), respectively. BBs comparably lowered BP and HR in both sexes. The lack of change in CO in males suggests that the reduction in BP is primarily due to a decrease in vascular resistance. Furthermore, females were underrepresented compared to males. We recommend that future research should include more females and sex-stratified data when researching the treatment effects of antihypertensives.

Comparison of heart rate and cardiac output of VVI pacemaker settings in patients with atrial fibrillation with bradycardia.

While most VVI pacemakers in bradycardic patients are set to a low limit of 60/min, the optimal lower limit rate for VVI pacemakers in atrial fibrillation has not been established. Although an increase in heart rate within the normal range in the setting of a VVI pacemaker might be expected to lead to an increase in cardiac output with the shortening of the diastolic time, the changes in cardiac output at different pacemaker settings have not been fully clarified. We included 11 patients with bradycardic atrial fibrillation who had VVI pacemakers implanted. Stroke volume was measured using the electrical cardiometry method (AESCULONⓇ mini; Osypka Medical) without pacing and at ventricular pacings of 60, 70, 80, and 90/min. Stroke volume decreased stepwise at ventricular pacing rates of 60, 70, 80, and 90/min (63.6 ± 11.2, 61.9 ± 10.6, 59.3 ± 12.2, and 57.5 ± 12.2 mL, p < .001), but cardiac output increased (3.81 ± 0.67, 4.33 ± 0.74, 4.74 ± 0.97, and 5.17 ± 1.09 L/min, p < .001). The rate of increase in cardiac output at a pacing rate of 70/min compared to 60/min correlated with left ventricular end-systolic volume (r = 0.711, p = .014). Cardiac output increased at a pacing rate of 70 compared to 60 in bradycardic atrial fibrillation patients, and the rate of increase in cardiac output was greater in those with larger left ventricular end-systolic volume.

Impact of pacing mode and different echocardiographic parameters on cardiac output (PADIAC).

The extent of the hemodynamic benefit from AV-synchronous pacing in patients with sinus rhythm and AV block is not completely understood. Thus, we systematically investigated the association of an array of echocardiographic and epidemiological parameters with the change in cardiac output depending on the stimulation mode (AV-synchronous or AV-asynchronous pacing). Patients in sinus rhythm after previous dual chamber pacemaker implantation underwent a thorough basic echocardiographic assessment of diastolic and systolic left ventricular function, and atrial function (26 echo parameters, including novel speckle tracking strain measurements). Then, stroke volume was measured with AV-synchronous (DDD) and AV-asynchronous (VVI) pacing. Each patient represented their own control, and the sequence of stroke volume measurements was randomized. In this prospective single-center study (NCT04068233, registration August 22nd 2019), we recruited 40 individuals. The stroke volume was higher in all patients when applying AV-synchronous DDD pacing [median increase 12.8 ml (16.9%), P < 0.001]. No echo parameter under investigation was associated with the extent of stroke volume increase in a linear regression model. Of all epidemiological variables, a history of acute myocardial infarction (AMI) was associated with an attenuated stroke volume gain in a univariate and a multivariate regression model that adjusted for confounders. A- and S-wave velocities were reduced in the AMI group. In our cohort of patients, each subject benefited from AV-synchronous DDD pacing. No single echo parameter could predict the amount of stroke volume increase. The beneficial effect of AV-synchronous pacing on stroke volume was attenuated after prior acute myocardial infarction.ClinicalTrials.gov identifier (NCT number): NCT04068233.

Cardiac output and the pharmacology of general anesthetics: a narrative review

The relationship between cardiac output and anesthetic drugs is important to anesthesiologists, since cardiac output determines the speed with which a drug infused into the bloodstream reaches its target and the intensity of the drug’s effect. But rather than focus on how anesthetic drugs affect cardiac output, this narrative review focuses on how changes in cardiac output affect the pharmacokinetics and pharmacodynamics of general anesthetics during the three phases of anesthesia.&#x0D; At induction, an increase in cardiac output shortens both the onset time of propofol for hypnosis and the neuromuscular blocking effect of rapid-acting neuromuscular blockers, favoring the conditions for rapid sequence intubation.&#x0D; During maintenance, changes in cardiac output are followed by opposite changes in the drug plasma concentration of anesthetic drugs. Thus, an increase in cardiac output followed by a decrease in the plasma concentration of the anesthetic could expose the patient to a real risk of intraoperative awakening, which can be avoided by increasing the dose of hypnotic drugs.&#x0D; At emergence, an increase in cardiac output secondary to an increase in pCO2 allows for a more rapid recovery from anesthesia. The pCO2 can be increased by adding CO2 to the respiratory circuit, lowering the ventilatory rate, or placing the patient on partial rebreathing. Finally, the reversal action of sugammadex for rocuronium-induced neuromuscular block can be shortened by increasing the cardiac output.

Detecting the Change in Total Circulatory Flow with a Wireless, Wearable Doppler Ultrasound Patch: A Pilot Study.

Prospective observational pilot study. Patients undergoing elective, on-pump coronary artery bypass grafting (CABG) surgery. Fourteen patients were referred for elective coronary artery bypass grafting surgery. Cardiopulmonary bypass (CPB) pump flow changes during surgery, as chosen by the perfusionist. A hands-free, wearable Doppler patch was used for CCA velocity measurements with the aim of preventing user errors in ultrasound measurements. Maximum CCA velocity was determined from the spectrogram acquired by the Doppler patch. CPB flow rates were recorded as displayed on the CPB console, and further measured from the peristaltic pulsation frequency visible on the recorded Doppler spectrograms. Changes in CCA maximum velocity tracked well with changes in CPB flow. On average, a 13.6% change in CCA maximum velocity was found to correspond to a 10% change in CPB flow rate. Changes in CCA velocity may be a useful surrogate for determining fluid responsiveness when user error can be mitigated.

Altered autonomic control or coronary artery blood flow by the aortic body chemoreceptors in conscious normotensive and hypertensive sheep

Peripheral arterial chemoreceptors monitor the chemical composition of the blood. While, the carotid bodies located at the bifurcation of the common carotid arteries have been extensively studied. The physiological role of the aortic bodies located in the walls of the aortic arch remains relatively under-studied, and its role in hypertension is unexplored.We hypothesized that activation of the aortic bodies would increase coronary blood flow in the normotensive state and that the parasympathetic nerves to the heart would mediate this.Experiments were conducted in conscious and anesthetized ewes instrumented to record arterial pressure, coronary blood flow, and cardiac output. Two groups of animals were studied, one made hypertensive using a 2 kidney one-clip model (HTN. n=6) and a sham-clipped normotensive group (Con. n=6). Unilateral renal clipping increased resting mean arterial pressure (Con: 84±5 vs HTN 115±6 mmHg). The aortic body chemoreceptors were stimulated by a bolus infusion of potassium cyanide (KCN; 10-30 μg/kg) into the left ventricle.Activation of the aortic bodies in the normotensive and hypertensive animals resulted in a significant increase in coronary blood flow ( P&lt;0.05, 2-way ANOVA, interaction effect), which was not different between groups. In normotensive sheep, the aortic body chemoreflex-mediated coronary vasodilation was attenuated by atropine infusion. Interestingly, the coronary vasodilation in hypertensive animals was not altered by the blockade of muscarinic receptors but was attenuated after propranolol infusion ( P&lt;0.05, interaction effect). Bilateral vagotomy is not possible in conscious animals; under anesthesia, the coronary blood flow response to aortic body stimulation was significantly attenuated in normotensive sheep. Neither atropine nor propranolol affected the aortic body chemoreflex meditated changes in either group's blood pressure, heart rate, or cardiac output. This data suggests that the aortic bodies play an important role in modulating coronary blood flow and that their effector mechanism is altered in hypertension. Many patients with hypertension are on beta-blockers. Our finding indicates that the aortic bodies modulate coronary blood flow via a beta-adrenergic mechanism in hypertension, which may have important implications for regulating coronary blood flow during exertion in hypertensive patients. Work is supported by the Health Research Council (HRC) of New Zealand. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Arterial hypotension: epidemiology, etiopathogenesis, symptomatology, and diagnosis

Arterial hypotension is a systemic hemodynamic disorder that is defined as a decrease in blood pressure below 90/60 mm Hg, caused by changes in cardiac output or systemic vascular resistance or both of these values, and that can lead to organ and tissue hypoperfusion. The review considers the epidemiology, etiology, and pathogenesis of this condition. Particular attention is paid to the classification of hypotension based on various biometric parameters, by the rate of occurrence and time of exposure, taking into account the impact on organ perfusion. The symptomatology and diagnosis of hypotension are analyzed; its complications are described.

The Effect of Pharmacologically Induced Blood Pressure Manipulation on Cardiac Output and Cerebral Blood Flow Velocity in Patients with Aneurysmal Subarachnoid Hemorrhage.

Vasopressors are used in patients with subarachnoid hemorrhage (SAH) to increase blood pressure with the idea of reversing the ischemic process. The current study is designed to evaluate the changes in systemic and cerebral hemodynamics, including cerebral blood flow autoregulation, at different pharmacologically augmented blood pressure levels using norepinephrine in patients with spontaneous aneurysmal SAH following surgery. This prospective observational study was carried out in patients with ruptured anterior circulation aneurysms who underwent surgical clipping and required norepinephrine infusion. Postoperatively, when the treating physician decided to start a vasopressor, norepinephrine infusion was started at 0.05 µg/kg/min. The infusion rate was increased by 0.05 µg/kg/min every 5 minutes to achieve a 20% and then 40% increase in the systolic blood pressure (SBP). When the blood pressure stabilized at each level for 5 minutes, hemodynamic and transcranial doppler (TCD) parameters in the middle cerebral artery (MCA) were recorded. Peak systolic, end-diastolic, and mean flow velocities in the MCA increased with targeted blood pressure increase in the hemispheres with impaired autoregulation and not in the hemispheres with intact autoregulation. The interaction of changes in TCD flow velocities between hemispheres with and without intact autoregulation was significant (p < 0.001). Cardiac output changes following norepinephrine infusion were not significant (p = 0.113). Hypertensive therapy with norepinephrine increases cerebral blood flow velocity only when autoregulation is impaired, an effect that is desirable in patients with focal cerebral ischemia following SAH. Lakshmegowda M, Muthuchellapan R, Sharma M, Ganne SUR, Chakrabarti D, Muthukalai S. The Effect of Pharmacologically Induced Blood Pressure Manipulation on Cardiac Output and Cerebral Blood Flow Velocity in Patients with Aneurysmal Subarachnoid Hemorrhage. Indian J Crit Care Med 2023;27(4):254-259.

Efficacy and Safety of Leadless Pacemakers for Atrioventricular Synchronous Pacing: A Systematic Review and Meta-Analysis

Leadless pacemakers with an atrioventricular synchrony algorithm represent a novel technology for patients qualified for VDD pacing. The current evidence of their performance is limited to several small-scale observational studies. This systematic review and meta-analysis aimed to evaluate the efficacy and safety of this new technology. We systematically searched the PubMed, Embase, and Cochrane library databases from their inception to 12 September 2022. The primary efficacy outcome was atrioventricular synchrony after implantation, whereas the secondary efficacy outcome was the change in cardiac output represented by the left ventricular outflow tract velocity time integral (LVOT-VTI). The primary safety outcome was major complications related to the procedures and the algorithm. Means or mean differences with 95% confidence interval (95% CI) were combined using a random-effects model or a fixed-effects model. Finally, 8 published studies with 464 participants were included in the qualitative analysis. The pooled atrioventricular synchrony proportion was 78.9% (95% CI 71.9-86.0%), and a further meta-regression did not screen factors that contributed significantly to the heterogeneity. Additionally, a significant increase in atrioventricular synchrony of 11.3% (95% CI 7.0-15.7%, p < 0.01) was achieved in patients experiencing programming optimization. LVOT-VTI was significantly increased by 1.9 cm (95% CI 1.2-2.6, p < 0.01), compared with the VVI pacing mode. The overall incidence of complications was approximately 6.3%, with major complications related to the algorithm being extremely low. Overall, leadless pacemakers with atrioventricular synchronous pacing demonstrated favorable safety and efficacy. Future data on their long-term performance are required to facilitate their widespread adoption in clinical practice.

Pulmonary artery wedge pressure and left ventricular end-diastolic pressure during exercise in patients with dyspnoea.

Pulmonary artery wedge pressure (PAWP) during exercise, as a surrogate for left ventricular (LV) end-diastolic pressure (EDP), is used to diagnose heart failure with preserved ejection fraction (HFpEF). However, LVEDP is the gold standard to assess LV filling, end-diastolic PAWP (PAWPED) is supposed to coincide with LVEDP and mean PAWP throughout the cardiac cycle (PAWPM) better reflects the haemodynamic load imposed on the pulmonary circulation. The objective of the present study was to determine precision and accuracy of PAWP estimates for LVEDP during exercise, as well as the rate of agreement between these measures. 46 individuals underwent simultaneous right and left heart catheterisation, at rest and during exercise, to confirm/exclude HFpEF. We evaluated: linear regression between LVEDP and PAWP, Bland-Altman graphs, and the rate of concordance of dichotomised LVEDP and PAWP ≥ or < diagnostic thresholds for HFpEF. At peak exercise, PAWPM and LVEDP, as well as PAWPED and LVEDP, were fairly correlated (R2>0.69, p<0.01), with minimal bias (+2 and 0 mmHg respectively) but large limits of agreement (±11 mmHg). 89% of individuals had concordant PAWP and LVEDP ≥ or <25 mmHg (Cohen's κ=0.64). Individuals with either LVEDP or PAWPM ≥25 mmHg showed a PAWPM increase relative to cardiac output (CO) changes (PAWPM/CO slope) >2 mmHg·L-1·min-1. During exercise, PAWP is accurate but not precise for the estimation of LVEDP. Despite a good rate of concordance, these two measures might occasionally disagree.

Changes in transcranial near-infrared spectroscopy values reflect changes in cardiac index during cardiac surgery.

To determine whether changes in transcranial near-infrared spectroscopy (NIRS) values reflect changes in cardiac index (CI) in adult cardiac surgical patients. Single-center prospective post hoc analysis. University hospital. One hundred and twenty-four adult patients undergoing cardiac surgery. In each patient, several CI measurements were taken, and NIRS values were collected simultaneously. We used a hierarchical linear regression model to assess the association between NIRS values and CI. We calculated a crude model with NIRS as the only factor included, and an adjusted model, where mean arterial pressure, end-tidal CO2 , and oxygen saturation were used as confounding factors. A total of 1301 pairs of NIRS and CI values were collected. The analysis of separate NIRS and CI pairs revealed a poor association, which was not statistically significant when adjusted with the chosen confounders. However, when the changes in NIRS from baseline or from the previous measurement were compared to those of CI, a clinically and statistically significant association between NIRS and CI was observed also in the adjusted model. Compared to the baseline and to the previous measurement, respectively, the regression coefficients with 95% confidence intervals were 0.048 (0.041-0.056) and 0.064 (0.055-0.073) in off-pump coronary artery bypass patients and 0.022 (0.016-0.029) and 0.026 (0.020-0.033) in patients who underwent cardiopulmonary bypass. In an unselected cardiac surgical population, the changes in NIRS values reflect those in CI, especially in off-pump coronary artery bypass patients. In this single-center post hoc analysis of data from a prospectively collected database of cardiac surgery patients, paired measurements of cardiac output and NIRS revealed that while there was a no correlation between individual paired measurements, a small correlation was found in changes in the two measurements from baseline values. This highlights a potential to utilize changes in NIRS from baseline to suggest changes in cardiac output in cardiac surgical populations.

Volumetric evaluation of fluid responsiveness using a modified passive leg raise maneuver during experimental induction and correction of hypovolemia in anesthetized dogs

ObjectiveTo demonstrate if modified passive leg raise (PLRM) maneuver can be used for volumetric evaluation of fluid responsiveness (FR) by inducing cardiac output (CO) changes during experimental induction and correction of hypovolemia in healthy anesthetized dogs. The effects of PLRM on plethysmographic variability index (PVI) and pulse pressure variation (PPV) were also investigated. Study designProspective, crossover study. AnimalsA total of six healthy anesthetized Beagle dogs. MethodsDogs were anesthetized with propofol and isoflurane. They were mechanically ventilated under neuromuscular blockade, and normothermia was maintained. After instrumentation, all dogs were subjected to four stages: 1, baseline; 2, removal of 27 mL kg–1 circulating blood volume; 3, after blood re-transfusion; and 4, after 20 mL kg–1 hetastarch infusion over 20 minutes. A 10 minute stabilization period was allowed after induction of each stage and before data collection. At each stage, CO via pulmonary artery thermodilution, PVI, PPV and cardiopulmonary variables were measured before, during and after the PLRM maneuver. Stages were sequential, not randomized. Statistical analysis included repeated measures anova and Tukey’s post hoc test, considering p < 0.05 as significant. ResultsDuring stage 2, PLRM at a 30° angle significantly increased CO (mean ± standard deviation, 1.0 ± 0.1 to 1.3 ± 0.1 L minute–1; p < 0.001), with a simultaneous significant reduction in PVI (38 ± 4% to 21 ± 4%; p < 0.001) and PPV (27 ± 2% to 18 ± 2%; p < 0.001). The PLRM did not affect CO, PPV and PVI during stages 1, 3 and 4. Conclusions and clinical relevanceIn anesthetized dogs, PLRM at a 30° angle successfully detected FR during hypovolemia, and identified fluid nonresponsiveness during normovolemia and hypervolemia. Also, in hypovolemic dogs, significant decreases in PVI and PPV occurred in response to PLRM maneuver.