Hemodynamic Variables Research Articles

Perioperative infusion of magnesium sulfate versus dexmedetomidine on the hemodynamic responses in patients undergoing laparoscopic cholecystectomy: A randomized controlled trial

Background: Laparoscopic cholecystectomy is associated with less post-operative pain, shorter hospitalization, and a faster functional recovery as compared to the open procedure. However, like any other surgery, a stress response is induced. Anesthesia interventions such as direct laryngoscopy, tracheal intubation, and extubation involve severe sympathetic stimulation. Magnesium can block the release of catecholamines from both the adrenal gland and adrenergic nerve terminals by inhibiting of activation of membrane Ca²⁺-ATPase and Na⁺-K⁺-ATPase. Aims and Objectives: Both magnesium sulfate and dexmedetomidine decrease the release of catecholamines and attenuate pressor responses to anesthesia and surgery. Materials and Methods: Eighty-four ASA I/II patients were randomly allocated to two groups. Group D received dexmedetomidine 1 μg/kg followed by 0.4 μg/kg/h and Group M received 2 g MgSO₄ followed by 15 mg/kg/h. hemodynamic variables were recorded as T0 (after loading dose of study drug), just before (T1) and 1, 2, and 3 min after ProSeal laryngeal mask airway (PLMA) insertion (T2 [i] [ii] [iii]), before and after peritoneal insufflation (T3 and T4), before and after table tilt (T5 and T6), after resuming flat position (T7), peritoneal deflation (T8), PLMA removal (T9), and on post-anesthesia care unit admission (T10). Data were collected and analyzed using SPSS 17 statistical software. Results: The demographic profile was comparable. After the study drug administration, there was a fall in mean arterial pressure (MAP) in both groups (Group D > Group M) and no pressor response to PLMA insertion. At peritoneal insufflation, the MAP increase was significantly more in Group M at T6, T7, and T8 (31.9%, 27.9%, and 35.6% above baseline, respectively). Although there was a fall in systolic blood pressure (SBP) from the baseline throughout the procedure in both groups, SBP was significantly higher at most times in Group M as compared to Group D (P<0.05). In both groups, there was a similar rise in diastolic blood pressure after peritoneal insufflation. The mean heart rate was significantly lower in Group D at all time points. Conclusion: Dexmedetomidine seemed to be superior to MgSO₄ for ameliorating hemodynamic responses in patients undergoing laparoscopic cholecystectomy.

Use of the cardiac power index to predict fluid responsiveness in the prone position: a proof-of-concept study

BackgroundThe primary aim of this proof-of-concept study was to investigate whether the Cardiac Power Index (CPI) could be a novel alternative method to assess fluid responsiveness in the prone position. MethodsPatients undergoing scheduled elective lumbar spine surgery in the prone position under general anesthesia were enrolled in the criteria of patients aged 19–75 years with American Society of Anesthesiologists (ASA) physical status I–II. The hemodynamic variables were evaluated before and after changes in posture after administering a colloid bolus (5 mL.kg−1) in the prone position. Fluid responsiveness was defined as an increase in the Stroke Volume Index (SVI) ≥ 10%. ResultsA total of 28 patients were enrolled. In responders, the CPI (median [1/4Q–3/4Q]) decreased to 0.34 [0.28–0.39] W.m−2 (p = 0.035) after the prone position. After following fluid loading, CPI increased to 0.48 [0.37–0.52] W.m−2 (p < 0.008), and decreased SVI (median [1/4Q–3/4Q]) after prone increased from 26.0 [24.5–28.0] mL.m−2 to 33.0 [31.0–37.5] mL.m−2 (p = 0.014). Among non-responders, CPI decreased to 0.43 [0.28–0.53] W.m−2 (p = 0.011), and SVI decreased to 29.0 [23.5–34.8] mL.m−2 (p < 0.009). CPI exhibited predictive capabilities for fluid responsiveness as a receiver operating characteristic curve of 0.78 [95% Confidence Interval, 0.60–0.95; p = 0.025]. ConclusionThis study suggests the potential of CPI as an alternative method to existing preload indices in assessing fluid responsiveness in clinical scenarios, offering potential benefits for responders and non-responders.

The Pivotal Role of Presepsin in Assessing Sepsis-Induced Cholestasis.

The serum levels of presepsin correlate with parameters indicating cholestasis in sepsis; however, the probability and significance of this association remain uncertain. We aimed to ascertain whether infection, as signaled by presepsin levels, is the primary determinant of elevated biliary parameters in sepsis. A unicenter, retrospective study included 396 COVID-free emergency-admitted patients, in which presepsin level was determined. Presepsin, neutrophil count, leukocyte count, C reactive protein, and fibrinogen evaluated the septic/inflammatory state. The statistically significant factors associated with cholestasis, ALT, and AST were analyzed by Fisher's exact test and Spearman regression with Bonferroni's correction. Presepsin emerged as the most likely variable correlated with all cholestasis markers: alkaline phosphatase (p = 7 × 10-8), gamma-glutamyl transferase (p = 5 × 10-10), and conjugated bilirubin (p = 4 × 10-15). Thrombocyte count, C reactive protein, age, creatinine, urea, lactate, and blood pressure, were associated with only one or two of these markers. In a sepsis setting, the increase in cholestasis-related parameters is associated with presepsin with a higher probability than hemodynamic, inflammatory, or coagulation-related variables. Determining this robust link between sepsis and cholestasis could eliminate unnecessary imaging procedures in critically ill patients, enabling clinicians to focus efforts on addressing the primary infectious cause.

Evaluating tissue hypoxia and the response to fluid administration in septic shock patients: a metabolic cluster analysis

BackgroundThe selection of adequate indicators of tissue hypoxia for guiding the resuscitation process of septic patients is a highly relevant issue. Current guidelines advocate for the use of lactate as sole metabolic marker, which may be markedly limited, and the integration of different variables seems more adequate. In this study, we explored the metabolic profile and its implications in the response to the administration of a fluid challenge in early septic shock patients.MethodsObservational study including septic shock patients within 24 h of ICU admission, monitored with a cardiac output estimation system, with ongoing resuscitation. Hemodynamic and metabolic variables were measured before and after a fluid challenge (FC). A two-step cluster analysis was used to define the baseline metabolic profile, including lactate, central venous oxygen saturation (ScvO2), central venous-to-arterial carbon dioxide difference (PcvaCO2), and PcvaCO2 corrected by the difference in arterial-to-venous oxygen content (PcvaCO2/CavO2).ResultsSeventy-seven fluid challenges were analyzed. Cluster analysis revealed two distinct metabolic profiles at baseline. Cluster A exhibited lower ScvO2, higher PcvaCO2, and lower PcvaCO2/CavO2. Increases in cardiac output (CO) were associated with increases in VO2 exclusively in cluster A. Baseline isolated metabolic variables did not correlate with VO2 response, and changes in ScvO2 and PcvaCO2 were associated to VO2 increase only in cluster A.ConclusionsIn a population of early septic shock patients, two distinct metabolic profiles were identified, suggesting tissue hypoxia or dysoxia. Integrating metabolic variables enhances the ability to detect those patients whose VO2 might increase as results of fluid administration.

Effectiveness of intracuff alkalinized lidocaine associated with intravenous dexamethasone in reducing laryngotracheal morbidity in children undergoing general anesthesia for tonsillectomy: a randomized controlled trial

BackgroundPostoperative sore throat is one of the main postoperative complaints in patients undergoing tonsillectomy. As the primary outcome, we aimed to determine whether endotracheal tube cuffs filled with alkalinized lidocaine are associated with a lower incidence of postoperative sore throat and anesthesia emergence phenomena in children undergoing tonsillectomy or adenotonsillectomy. We also assessed the potential additional benefits of IV dexamethasone in reducing postoperative laryngotracheal morbidity. MethodsThis is a clinical prospective, randomized, controlled trial. Patients were randomly allocated to one of four groups, as follows: air – endotracheal tube cuff filled with air; air/dex – endotracheal tube cuff filled with air and intravenous dexamethasone; lido – endotracheal tube cuff filled with alkalinized lidocaine; and lido/dex – endotracheal tube cuff filled with alkalinized lidocaine and intravenous dexamethasone. Perioperative hemodynamic parameters and the incidence of postoperative nausea and vomiting, coughing and hoarseness were recorded. Postoperative sore throat was assessed in the postanesthetic care unit and 24 hours post tracheal extubation. ResultsIn total, 154 children aged 4–12 years, ASA physical status I or II, undergoing general anesthesia for elective tonsillectomy and adenotonsillectomy, were assessed for postoperative sore throat in this study. The incidence of postoperative sore throat 24 hours after tracheal extubation was significantly lower in the lido/dex group compared to groups air and air/dex (p = 0.01). However, no additional reduction in these symptoms was observed from the intravenous administration of dexamethasone when comparing the lido and lido/dex groups. Similarly, there were no differences among groups regarding perioperative hemodynamic variables or postoperative nausea and vomiting, coughing, and hoarseness during the study period. ConclusionIntracuff alkalinized lidocaine, associated with intravenous dexamethasone, might be effective in reducing sore throat 24 hours post-tonsillectomy or adenotonsillectomy in children when compared to the use of air as the cuff insufflation media.

Continuum of Preshock to Classic Cardiogenic Shock in the Critical Care Cardiology Trials Network Registry

BackgroundThe prognostic implications of phenotypes along the preshock to cardiogenic shock (CS) continuum remain uncertain. ObjectivesThis study sought to better characterize pre- or early shock and normotensive CS phenotypes and examine outcomes compared to those with conventional CS. MethodsThe CCCTN (Critical Care Cardiology Trials Network) is a registry of contemporary cardiac intensive care units. Consecutive admissions (N = 28,703 across 47 sites) meeting specific criteria based on hemodynamic variables, perfusion parameters, and investigator-reported CS were classified into 1 of 4 groups or none: isolated low cardiac output (CO), heart failure with isolated hypotension, normotensive CS, or SCAI (Society of Cardiovascular Angiography and Intervention) stage C CS. Outcomes of interest were in-hospital mortality and incidence of subsequent hypoperfusion among pre- and early shock states. ResultsA total of 2,498 admissions were assigned to the 4 groups with the following distribution: 4.8% isolated low CO, 4.4% isolated hypotension, 12.1% normotensive CS, and 78.7% SCAI stage C CS. Overall in-hospital mortality was 21.3% (95% CI: 19.7%-23.0%), with a gradient across phenotypes (isolated low CO 3.6% [95% CI: 1.0%-9.0%]; isolated hypotension 11.0% [95% CI: 6.9%-16.6%]; normotensive CS 17.0% [95% CI 13.0%-21.8%]; SCAI stage C CS 24.0% [95% CI: 22.1%-26.0%]; global P < 0.001). Among those with an isolated low CO and isolated hypotension on admission, 47 (42.3%) and 56 (30.9%) subsequently developed hypoperfusion. ConclusionsIn a large contemporary registry of cardiac critical illness, there exists a gradient of mortality for phenotypes along the preshock to CS continuum with risk for subsequent worsening of preshock states. These data may inform refinement of CS definitions and severity staging.

Effectiveness and safety of remimazolam tosilate versus propofol for sedation in patients undergoing gastrointestinal endoscopy: a randomized controlled trial.

Remimazolam tosilate is a new type of benzodiazepine currently used for gastrointestinal endoscopy and can be combined with alfentanil. This trial compared the effectiveness and safety of remimazolam with alfentanil to propofol with alfentanil in patients undergoing gastrointestinal endoscopy. One hundred and sixty-six patients were randomly divided into propofol-alfentanil anaesthesia (Group P) and remimazolam-alfentanil anaesthesia (Group R). The primary outcomes were perioperative haemodynamic variables, including systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), heart rate (HR) and oxygen saturation (SpO2) preoperatively (T0); after anaesthesia induction (T1); when the gastroscope passed through the oropharynx (T2); 3min (T3), 5min (T4) and 7min (T5) after T2; at the end of surgery (T6); and when patients successfully awakened (T7). The secondary outcomes included induction and awakening time, patient satisfaction, operator satisfaction, and adverse event occurrences. Compared with those in Group P, the SBP in Group R was significantly higher at T1, T2, T3, and T6 (P < 0.05); the DBP and MAP were significantly higher at T1, T2, T3, T5, and T6 (P < 0.05); the HR was significantly faster at T1 to T6 (P < 0.05); the SpO2 was significantly higher at T1 to T4 (P < 0.05); the incidences of hypoxemia, hypotension, and drug injection pain were significantly lower in Group R (P < 0.05); the incidence of hiccups was higher (P < 0.05); the awakening time was shorter in Group R (P < 0.05); and the operator satisfaction score was high (P < 0.05). Compared to propofol with alfentanil, remimazolam with alfentanil can be used safely and effectively for sedation in patients undergoing gastrointestinal endoscopy, with less impact on the patient's circulatory and respiratory systems and a lower incidence of adverse events. This trial protocol was registered in the Chinese Clinical Trial Registry (ChiCR2300077252, date: 2023-11-02).

Mini-strokes after awake surgery for glioma resection: are there anesthesia related factors?

Awake surgery is now a common approach for the resection of glioma. One of the surgical complications is mini-stroke which take the form of periresectional small areas of brain ischemic lesions. The main objective of this study is to evaluate the association between factors related to anesthetic management and the risk of mini-stroke, in awake surgery for glioma resection. In this single-center retrospective study, all patients who were operated on, between 2011 and 2022, in awake conditions for a glioma resection, were retrospectively included. The studied anesthetic parameters included hemodynamic variables, fluid intake and urinary output. The primary endpoint was the presence of mini-stroke on a magnetic resonance imaging performed within the first 48h postoperatively. A total of 176 surgeries were included. Mini-stroke was present in 120/171 surgeries (70%), with a median volume of 1.2 interquartile range [0.4-2.2] cubic centimeters (cc). In a multivariable analysis, only the per operative urinary output was significantly associated with the incidence of postoperative mini-strokes (adjusted odd-ratio 0.65, 95% confidence interval 0.45-0.94, p = 0.02). No variables related to the anesthetic management were associated with the volume of postoperative mini-strokes. In particular, the time spent below 90% of the baseline systolic blood pressure was not associated with either the risk or the volume of mini-strokes. During awake surgery for glioma resection, among several anesthesia related factors, only the per operative urinary output was associated with the incidence of postoperative mini-stroke.

Three-dimensional anatomic features of the mitral valve that predict systolic anterior motion occurring during dobutamine stress echocardiography.

Left ventricular outflow tract obstruction related to systolic anterior motion (SAM) of the mitral valve is a common complication of dobutamine stress echocardiography (DSE). However, the mechanisms underlying SAM have not been fully characterized. The objective of the present study was to use three-dimensional echocardiography to identify anatomic features of the mitral valve that predispose to SAM during DSE. We retrospectively evaluated consecutive patients included prospectively in our database and who had undergone 3D echocardiography (including an assessment of the mitral valve) before DSE. Patients who had developed SAM during DSE (the SAM+ group) were matched 2:3 with patients who did not (the SAM- group). One hundred patients were included (mean age: 67±10). Compared with SAM- patients (n=60), SAM+ patients (n=40) had a lower mitral annular area, a smaller perimeter, and a smaller diameter (p<.01 for all, except the anteroposterior diameter). The SAM+ group had also a narrower mitral-aortic angle (126±12° vs. 139±11° in the SAM- group; p<.01) and a higher posterior mitral leaflet length (1.4±.27cm vs. 1.25±.29, respectively; p<.01). Furthermore, the mitral annulus was more spherical, more flexible, and more dynamic in SAM+ patients than in SAM- patients (p<.05 for all). In a multivariate analysis of anatomic variables, the mitral-aortic angle, the mitral annular area, and posterior leaflet length were independent predictors of SAM (p ≤ .01 for all). In a multivariate analysis of standard echo and hemodynamic variables, the presence of wall motion abnormalities at rest (p<.01) was an independent predictor of SAM. SAM during DSE is multifactorial. In addition to the pharmacologic effects of dobutamine on the myocardium, 3D echocardiographic features of the mitral valve (a smaller mitral annulus, a narrower mitral-aortic angle, and a longer posterior leaflet) appear to predispose to SAM.

Opioid free analgesia after return home in ambulatory colonic surgery patients: a single-center observational study

BackgroundBecause of the adverse effects of morphine and its derivatives, non-opioid analgesia procedures are proposed after outpatient surgery. Without opioids, the ability to provide quality analgesia after the patient returns home may be questioned. We examined whether an opioid-free strategy could ensure satisfactory analgesia after ambulatory laparoscopic colectomy.MethodsWe performed a retrospective observational single-center study (of prospective collected database) including all patients eligible for scheduled outpatient colectomy. Postoperative analgesia was provided by paracetamol and nefopam. Postoperative follow-up included pain at mobilization (assessed by a numerical rating scale, NRS), hemodynamic variables, temperature, resumption of transit and biological markers of postoperative inflammation. The primary outcome was the proportion of patients with moderate to severe pain (NRS > 4) the day after surgery.ResultsData from 144 patients were analyzed. The majority were men aged 59 ± 12 years with a mean BMI of 27 [25-30] kg/m2. ASA scores were 1 for 14%, 2 for 59% and 3 for 27% of patients. Forty-seven patients (33%) underwent surgery for cancer, 94 for sigmoiditis (65%) and 3 (2%) for another colonic pathology. Postoperative pain was affected by time since surgery (Q3 = 52.4,p < 0.001) and decreased significantly from day to day. The incidence of moderate to severe pain at mobilization (NRS > 4) on the first day after surgery was (0.19; 95% CI, 0.13–0.27).ConclusionNon-opioid analgesia after ambulatory laparoscopic colectomy seems efficient to ensure adequate analgesia. This therapeutic strategy makes it possible to avoid the adverse effects of opioids.Trial registrationThe study was retrospectively registered and approved by the relevant institutional review board (CERAR) reference IRB 00010254–2018 – 188). All patients gave written informed consent for analysis of their data. The anonymous database was declared to the French Data Protection Authority (CNIL) (reference 221 2976 v0 of April 12, 2019).

Computational framework for the generation of one-dimensional vascular models accounting for uncertainty in networks extracted from medical images.

One-dimensional (1D) cardiovascular models offer a non-invasive method to answer medical questions, including predictions of wave-reflection, shear stress, functional flow reserve, vascular resistance and compliance. This model type can predict patient-specific outcomes by solving 1D fluid dynamics equations in geometric networks extracted from medical images. However, the inherent uncertainty in in vivo imaging introduces variability in network size and vessel dimensions, affecting haemodynamic predictions. Understanding the influence of variation in image-derived properties is essential to assess the fidelity of model predictions. Numerous programs exist to render three-dimensional surfaces and construct vessel centrelines. Still, there is no exact way to generate vascular trees from the centrelines while accounting for uncertainty in data. This study introduces an innovative framework employing statistical change point analysis to generate labelled trees that encode vessel dimensions and their associated uncertainty from medical images. To test this framework, we explore the impact of uncertainty in 1D haemodynamic predictions in a systemic and pulmonary arterial network. Simulations explore haemodynamic variations resulting from changes in vessel dimensions and segmentation; the latter is achieved by analysing multiple segmentations of the same images. Results demonstrate the importance of accurately defining vessel radii and lengths when generating high-fidelity patient-specific haemodynamics models. KEY POINTS: This study introduces novel algorithms for generating labelled directed trees from medical images, focusing on accurate junction node placement and radius extraction using change points to provide haemodynamic predictions with uncertainty within expected measurement error. Geometric features, such as vessel dimension (length and radius) and network size, significantly impact pressure and flow predictions in both pulmonary and aortic arterial networks. Standardizing networks to a consistent number of vessels is crucial for meaningful comparisons and decreases haemodynamic uncertainty. Change points are valuable to understanding structural transitions in vascular data, providing an automated and efficient way to detect shifts in vessel characteristics and ensure reliable extraction of representative vessel radii.

Impact of the HeartMate 3 Pump Speed Modulation Algorithm on Derived Pump Parameters and Measured Haemodynamic Variables

Impact of the HeartMate 3 Pump Speed Modulation Algorithm on Derived Pump Parameters and Measured Haemodynamic Variables

Restrictive versus Decision Support Guided Fluid Therapy during Major Hepatic Resection Surgery: A Randomized Controlled Trial.

Fluid therapy during major hepatic resection aims at minimizing fluids during the dissection phase to reduce central venous pressure, retrograde liver blood flow, and venous bleeding. This strategy, however, may lead to hyperlactatemia. The Acumen assisted fluid management system uses novel decision support software, the algorithm of which helps clinicians optimize fluid therapy. The study tested the hypothesis that using this decision support system could decrease arterial lactate at the end of major hepatic resection when compared to a more restrictive fluid strategy. This two-arm, prospective, randomized controlled, assessor- and patient-blinded superiority study included consecutive patients undergoing major liver surgery equipped with an arterial catheter linked to an uncalibrated stroke volume monitor. In the decision support group, fluid therapy was guided throughout the entire procedure using the assisted fluid management software. In the restrictive fluid group, clinicians were recommended to restrict fluid infusion to 1 to 2 ml · kg-1 · h-1 until the completion of hepatectomy. They then administered fluids based on advanced hemodynamic variables. Noradrenaline was titrated in all patients to maintain a mean arterial pressure greater than 65 mmHg. The primary outcome was arterial lactate level upon completion of surgery (i.e., skin closure). A total of 90 patients were enrolled over a 7-month period. The primary outcome was lower in the decision support group than in the restrictive group (median [quartile 1 to quartile 3], 2.5 [1.9 to 3.7] mmol · l-1vs. 4.6 [3.1 to 5.4] mmol · l-1; median difference, -2.1; 95% CI, -2.7 to -1.2; P < 0.001). Among secondary exploratory outcomes, there was no difference in blood loss (median [quartile 1 to quartile 3], 450 [300 to 600] ml vs. 500 [300 to 800] ml; P = 0.727), although central venous pressure was higher in the decision support group (mean ± SD of 7.7 ± 2.0 mmHg vs. 6.6 ± 1.1 mmHg; P < 0.002). Patients managed using a clinical decision support system to guide fluid administration during major hepatic resection had a lower arterial lactate concentration at the end of surgery when compared to a more restrictive fluid strategy. Future trials are necessary to make conclusive recommendations that will change clinical practice.

Vascular Reactivity during Cardiopulmonary Bypass in Patients at Punjab Institute of Cardiology and Shalamar Hospital Lahore, Pakistan

Background: The operative treatment of cardiac diseases remains associated with systemic inflammation and a suboptimal outcome in many patients. These inflammatory changes are manifested by systemic hypotension, myocardial failure, increased vascular permeability and consequent dysfunction of organs such as the lungs, gut and brain. In general terms, sympathetic innervations of the small arteries and arterioles allows vasoconstriction, thereby increasing resistance to blood flow, whereas innervations of the large arteries and veins decreases the volume in these vessels, resulting in the redistribution of blood volume. This study was conducted to determine the effect of vasodilator drugs on duration of vasodilatation in patients undergoing coronary artery bypass grafting (CABG) with Cardiopulmonary bypass (CPB).Methods: We evaluated prospectively the effect of vasodilator medications before CABG surgery on hemodynamic variables and use of vasoactive drugs. We studied 30 patients with good left ventricular function allocated randomly to continue vasodilator drugs before cardiac surgery. Arterial pressure, Cardiac output, systemic vascular resistance and use of vasoactive drugs were recorded during anaesthesia, perioperative and in the early postoperative period.Results: Patients who using vasodilator drugs before cardiac surgery had not significant relationship between vasodilator drugs and vessels reactivity (vasoconstriction &amp; vasodilatation). However, these patients required more vasodilator drugs to control hypertension after CPB and in the early postoperative period.Conclusion: There was no difference in hypotension at the onset of CPB or in the use of vasodilator drugs before cardiac surgery. We conclude that vasodilator drugs before cardiac surgery did not have sufficient effect to be recommended routinely.

Evaluation of fluid responsiveness using liver compression in dogs with experimentally induced hypovolemia.

To investigate whether liver compression (LC) could increase stroke volume (SV) by more than 15% in healthy, anesthetized dogs with hypovolemia and suggest LC as a novel method to evaluate fluid responsiveness. 6 healthy Beagles. This prospective, nonrandomized experimental study was conducted from November 2023 to February 2024. The dogs were anesthetized with isoflurane and mechanically ventilated under neuromuscular blockade. After instrumentation, the dogs underwent the following 4 experimental stages in a sequential, nonrandomized manner: stage 1, baseline; stage 2, 30% withdrawal of circulating blood volume; stage 3, 50% infusion of the collected blood; and stage 4, the remaining 50% infusion of the collected blood. At each stage, SV via pulmonary artery thermodilution and hemodynamic variables were measured before, during, and after the LC. In stage 2, LC significantly increased mean SV by 30%, from 6.9 to 9 mL/beat. Simultaneously, LC significantly increased mean arterial pressure by 11 mm Hg and mean central venous pressure by 2 mm Hg, while pulse pressure variation significantly decreased from 28% to 22%. In stages 1, 3, and 4, LC did not significantly change mean SV, mean arterial pressure, and pulse pressure variation; however, mean central venous pressure significantly increased during stage 3. This study demonstrates that LC at 22 mm Hg for 1 minute could increase SV more than 15% in anesthetized, hypovolemic dogs and LC could be used as a novel method to evaluate fluid responsiveness.

Sex and circadian regulation of metabolic demands in the rat kidney: A modeling analysis.

Renal hemodynamics, renal transporter expression levels, and urine excretion exhibit circadian variations. Disruption of these diurnal patterns is associated with the pathophysiology of hypertension and chronic kidney disease. Renal hemodynamics determines oxygen delivery, whereas renal transport and metabolism determines oxygen consumption; the balance between them yields renal oxygenation which also demonstrates 24-h periodicity. Another notable modulator of kidney function is sex, which has impacts on renal hemodynamics and transport function that are regulated by as well as independent of the circadian clock. The goal of this study was to investigate the diurnal and sexual variations in renal oxygen consumption and oxygenation. For this purpose, we developed computational models of rat kidney function that represent sexual dimorphism and circadian variation in renal hemodynamics and transporter activities. Model simulations predicted substantial differences in tubular Na+ transport and oxygen consumption among different nephron segments. We also simulated the effect of loop diuretics, which are used in the treatment of renal hypoxia, on medullary oxygen tension. Our model predicted a significantly higher effect of loop diuretics on medullary oxygenation in female rats compared to male rats and when administered during the active phase.

Computational Hemodynamics-Based Growth Prediction for Small Abdominal Aortic Aneurysms: Laminar Simulations Versus Large Eddy Simulations.

Prior studies have shown that computational fluid dynamics (CFD) simulations help assess patient-specific hemodynamics in abdominal aortic aneurysms (AAAs); patient-specific hemodynamic stressors are frequently used to predict an AAA's growth. Previous studies have utilized both laminar and turbulent simulation models to simulate hemodynamics. However, the impact of different CFD simulation models on the predictive modeling of AAA growth remains unknown and is thus the knowledge gap that motivates this study. Specifically, CFD simulations were performed for 70 AAA models derived from 70 patients' computed tomography angiography (CTA) data with known growth status (i.e., fast-growing [> 5mm/yr] or slowly growing [< 5mm/yr]). We used laminar and large eddy simulation (LES) models to obtain hemodynamic parameters to predict AAAs' growth status. Predicting the growth status of AAAs was based on morphological, hemodynamic, and patient health parameters in conjunction with three classical machine learning (ML) classifiers, namely, support vector machine (SVM), K-nearest neighbor (KNN), and generalized linear model (GLM). Our preliminary results estimated aneurysmal flow stability and wall shear stress (WSS) were comparable in both laminar and LES flow simulations. Moreover, computed WSS and velocity-related hemodynamic variables obtained from the laminar and LES simulations showed comparable abilities in differentiating the growth status of AAAs. More importantly, the predictive modeling performance of the three ML classifiers mentioned above was similar, with less than a 2% difference observed (p-value>0.05). In closing, our findings suggest that two different flow simulations investigated did not significantly affect outcomes of computational hemodynamics and predictive modeling of AAAs' growth status, given the data investigated.

The Impact of Increased PEEP on Hemodynamics, Respiratory Mechanics, and Oxygenation in Pediatric ARDS.

PEEP is a cornerstone treatment for children with pediatric ARDS. Unfortunately, its titration is often performed solely by evaluating oxygen saturation, which can lead to inadequate PEEP level settings and consequent adverse effects. This study aimed to assess the impact of increasing PEEP on hemodynamics, respiratory system mechanics, and oxygenation in children with ARDS. Children receiving mechanical ventilation and on pressure-controlled volume-guaranteed mode were prospectively assessed for inclusion. PEEP was sequentially changed to 5, 12, 10, 8 cm H2O, and again to 5 cm H2O. After 10 min at each PEEP level, hemodynamic, ventilatory, and oxygenation variables were collected. A total of 31 subjects were included, with median age and weight of 6 months and 6.3 kg, respectively. The main reasons for pediatric ICU admission were respiratory failure caused by acute viral bronchiolitis (45%) and community-acquired pneumonia (32%). Most subjects had mild or moderate ARDS (45% and 42%, respectively), with a median (interquartile range) oxygenation index of 8.4 (5.8-12.7). Oxygen saturation improved significantly when PEEP was increased. However, although no significant changes in blood pressure were observed, the median cardiac index at PEEP of 12 cm H2O was significantly lower than that observed at any other PEEP level (P = .001). Fourteen participants (45%) experienced a reduction in cardiac index of > 10% when PEEP was increased to 12 cm H2O. Also, the estimated oxygen delivery was significantly lower, at 12 cm H2O PEEP. Finally, respiratory system compliance significantly reduced when PEEP was increased. At a PEEP of 12 cm H2O, static compliance had a median reduction of 25% in relation to the initial assessment (PEEP of 5 cm H2O). Although it may improve arterial oxygen saturation, inappropriately high PEEP levels may reduce cardiac output, oxygen delivery, and respiratory system compliance in pediatric subjects with ARDS with low potential for lung recruitability.

Cerebral blood flow and end-tidal CO2 predict lightheadedness during head-up tilt in patients with orthostatic intolerance.

Orthostatic intolerance (OI) is a common problem. Reliable markers of OI are missing, as orthostatic blood pressure and heart rate poorly correlate with orthostatic symptoms. The objective of this study was to assess the relationship between orthostatic lightheadedness and cerebral blood flow. In this retrospective study patients with OI were evaluated at the Autonomic Laboratory of the Department of Neurology, Brigham and Women's Faulkner Hospital, Boston. The 10-minute head-up tilt test was performed as a part of autonomic testing. Orthostatic lightheadedness was evaluated at every minute of the head-up tilt. Heart rate, blood pressure, capnography, and cerebral blood flow velocity (CBFv) in the middle cerebral artery using transcranial Doppler were measured. Repeated-measures design with a linear mixed-effects model was used to evaluate the relationship between orthostatic lightheadedness and hemodynamic variables. Correlation analyses were done by calculating Pearson's coefficient. Twenty-two patients with OI were compared to nineteen controls. Orthostatic CBFv and end-tidal CO2 decreased in OI patients compared to controls (p < 0.001) and predicted orthostatic lightheadedness. Orthostatic heart rate and blood pressure failed to predict orthostatic lightheadedness. The lightheadedness threshold, which marked the onset of lightheadedness, was equal to an average systolic CBFv decrease of 18.92% and end-tidal CO2 of 12.82%. The intensity of lightheadedness was proportional to the CBFv and end-tidal CO2 decline. Orthostatic lightheadedness correlated with systolic CBFv (r=-0.6, p < 0.001) and end-tidal CO2 (r=-0.33, p < 0.001) decline. In conclusion, orthostatic CBFv and end-tidal CO2 changes predict orthostatic lightheadedness and can be used as objective markers of OI.

Cardiac vagal activity changes moderated the association of cognitive and cerebral hemodynamic variations in the prefrontal cortex

Phasic cardiac vagal activity (CVA), reflecting ongoing, moment-to-moment psychophysiological adaptations to environmental changes, can serve as a predictor of individual difference in executive function, particularly executive performance. However, the relationship between phasic CVA and executive function demands requires further validation because of previous inconsistent findings. Moreover, it remains unclear what types of phasic changes of CVA may be adaptive in response to heightened executive demands. This study used the standard N-back task to induce different levels of working memory (WM) load and combined functional Near-Infrared Spectroscopy (fNIRS) with a multipurpose polygraph to investigate the variations of CVA and its interactions with cognitive and prefrontal responses as executive demands increased in fifty-two healthy young subjects. Our results showed phasic decreases in CVA as WM load increased (t (51) = -3.758, p < 0.001, Cohen's d = 0.526). Furthermore, phasic changes of CVA elicited by increased executive demands moderated the association of cognitive and cerebral hemodynamic variations in the prefrontal cortex (B = 0.038, SE = 0.014, p < 0.05). Specifically, as executive demands increased, individuals with larger phasic CVA withdrawal showed a positive relationship between cognitive and hemodynamic variations in the prefrontal cortex (β = 0.281, p = 0.031). No such significant relationship was observed in individuals with smaller phasic CVA withdrawal. The current findings demonstrate a decrease in CVA with increasing executive demands and provide empirical support for the notion that a larger phasic CVA withdrawal can be considered adaptive in situations requiring high executive function demands.