Phenylephrine increases cardiac output by raising cardiac preload in patients with anesthesia induced hypotension

Feasibility and Safety of Regadenoson Stress Perfusion Protocol in Pediatric Transplant Patients under General Anesthesia

BACKGROUND

Cardiac magnetic resonance with myocardial stress perfusion (stress CMR) is a non-invasive technique that offers assessment of myocardial function, perfusion, and viability. Regadenoson is a selective cardiac adenosine A2 receptor agonist with fewer side effects than adenosine and a favorable safety profile in older pediatric heart transplant recipients (PHTR). There are limited studies evaluating the hemodynamic response of regadenoson in pediatric patients under general anesthesia (GA).

METHODS

We reviewed our experience with regadenoson stress CMR in PHTR under GA from 2020-2024 and compared to a non-GA group of PHTR who underwent regadenoson stress CMR from 2015-2022. Demographic and clinical data were recorded. Hemodynamic response and adverse events were reviewed. CMRs were reviewed for perfusion abnormalities and semi-quantitative analysis was performed using myocardial perfusion reserve index (MPRI).

RESULTS

Forty-six PHTR underwent 53 stress CMRs under GA over the study period (mean age 7.8 years; range 3-19 years). All patients received endotracheal intubation and sevoflurane and were monitored during and after regadenoson administration per institutional protocol. Heart rate (HR) prior to regadenoson administration was 84±12 beats/min with a peak of 109±14 beats/min and average mean blood pressure (BP) was 63±12mmHg with a nadir of 45±8mmHg. Transient hypotension was observed in 33 (77%) scans, which resolved with phenylephrine. There were no other adverse events. Phenylephrine was used in 48 CMRs (91%) for blood pressure support at the discretion of anesthesia. Thirty-eight PHTR underwent 48 stress CMRs without sedation. CMRs were matched by time-since-transplant. The non-GA group was significantly older (mean age 15.8 years; p<0.001). GA patients had a larger percent decrease in mean BP compared to non-GA patients (27±17% vs 15±17%; p <0.001) with no difference in HR change. There were no significant differences in rates of qualitative perfusion defects, (11% vs 4%, p=0.18), late gadolinium enhancement or MPRI values between the two groups.

CONCLUSION

Regadenoson stress CMR is safe and feasible in PHTR under GA. While hypotension was frequently seen, it improved in all cases with phenylephrine. Semi-quantitative myocardial perfusion analysis by MPRI is feasible in these young patients, however further studies are needed to assess its clinical utility in this population.

Development and evaluation of an automated phenylephrine delivery system by lower limit control for managing intraoperative hypotension

PURPOSE

In this study, we aimed to develop and evaluate an automated phenylephrine delivery system by lower limit control for the management of intraoperative hypotension, assessing its efficacy in maintaining adequate blood pressure levels.

METHODS

Twenty patients undergoing surgery with anticipated blood pressure fluctuations were enrolled in this study. Patients were randomly assigned to two groups. Noninvasive blood pressure (NIBP) was measured at 2.5-min intervals using an upper arm cuff. In the automated group, phenylephrine administration was governed by an automated system that delivered bolus doses and adjusted the continuous infusion rate when mean blood pressure (MBP) dropped below 65 mmHg. In the manual group, phenylephrine administration was initiated by the attending anesthesiologist under the same MBP threshold. Propofol, remifentanil, and rocuronium were administered via the automated delivery system for total intravenous anesthesia, to minimize hemodynamic variability between groups. The primary end point was the percentage of time during which MBP remained above 65 mmHg and systolic blood pressure below 140 mmHg, measured from the initiation to the cessation of intravenous anesthesia and assessed using a non-inferiority test.

RESULTS

The automated group adequately maintained blood pressure within the target range for 84.53% of the time, compared to 72.45% in the manual group, confirming statistical non-inferiority (p < 0.001).

CONCLUSION

This system effectively managed intraoperative hypotension using intermittent NIBP measurements, which are more feasible in clinical practice. Despite relying on less frequent and lower-resolution blood pressure data, it demonstrated efficacy comparable to anesthesiologist-led management, indicating its potential for broader clinical application.

Spectroscopic, quantum chemical, and topological calculations of the phenylephrine molecule using density functional theory

In this work, Density Functional Theory (DFT) on Gaussian 09 W software was utilized to investigate the phenylephrine (PE) molecule (C9H13NO2). Firstly, the optimized structure of the PE molecule was obtained using B3LYP/6-311 + G (d, p) and CAM-B3LYP/6-311 + G (d, p) basis sets. The electron charge density is shown in Mulliken atomic charge as a bar chart and also as a color-filled map in Molecular Electrostatic Potential (MEP). Using these properties, the possibility of different charge transfers occurring within the molecule was evaluated. The calculated values of the energy gap from HOMO-LUMO mapping, illustrated in Frontier Molecular Orbitals (FMO) and Density of State (DOS), were found to be similar for both the neutral and anion states in the gaseous and water solvent phases. Both the global and local reactivity were studied to understand the reactivity of the PE molecule. Using the thermodynamic parameters, the thermochemical property of the title molecule was understood. Non-covalent interaction was studied to understand the Van der Waals interactions, hydrogen bonds, and steric repulsion in the title molecule. Natural Bond Orbital (NBO) Analysis was performed to understand the strongest stabilization interaction. In the vibrational analysis, Total Electron Density (TED) assignments were done in the intense region where the frequency of the title molecule was shifted distinctly. For vibrational spectroscopy, FT-IR and Raman spectra in the neutral and anion states were plotted and compared. Using the TD-DFT technique, the UV-Vis spectra along with Tauc's plot were studied. Finally, topological analysis, electron localized function (ELF), and localized orbital locator (LOL) were performed in the PE molecule.

Dynamic Estimation of Cardiovascular State From Arterial Blood Pressure Recordings

Real-time estimation of patient cardiovascular states, including cardiac output and systemic vascular resistance, is necessary for personalized hemodynamic monitoring and management. Highly invasive measurements enable reliable estimation of these states but increase patient risk. Prior methods using minimally invasive measurements reduce patient risk but have produced unreliable estimates limited due to trade-offs in accuracy and time resolution. Our objective was to develop an approach to estimate cardiac output and systemic vascular resistance with both a high time resolution and high accuracy from minimally invasive measurements. Using the two-element Windkessel model, we formulated a state-space method to estimate a dynamic time constant - the product of systemic vascular resistance and compliance - from arterial blood pressure measurements. From this time constant, we derived proportional estimates of systemic vascular resistance and cardiac output. We then validated our method with a swine cardiovascular dataset. Our estimates produced using arterial blood pressure measurements not only closely align with those using highly invasive measurements, but also closely align when derived from three separate locations on the arterial tree. Moreover, our estimates predictably change in response to standard cardiovascular drugs. Overall, our approach produces reliable, real-time estimates of cardiovascular states crucial for monitoring and control of the cardiovascular system.

Vasoconstriction with phenylephrine increases cardiac output in preload dependent patients

General Anaesthesia (GA) is accompanied by a marked decrease in sympathetic outflow and thus loss of vasomotor control of cardiac preload. The use of vasoconstriction during GA has mainly focused on maintaining blood pressure. Phenylephrine (PE) is a pure α1-agonist without inotropic effects widely used to correct intraoperative hypotension. The potential of PE for augmenting cardiac stroke volume (SV) and -output (CO) by venous recruitment is controversial and no human studies have explored the effects of PE in preload dependent circulation using indicator dilution technique. We hypothesized that PE-infusion in patients with cardiac stroke volume limited by reduced preload would restore preload and thus augment SV and CO. 20 patients undergoing GA for gastrointestinal surgery were monitored with arterial catheter and LiDCO unity monitor. Upon stable haemodynamics after induction patients were placed in head-up tilt (HUT). All patients became preload responsive as verified by a stroke volume variation (SVV) of > 12%. PE-infusion was then started at 15-20mikrg/min and adjusted until preload was restored (SVV < 12%). Li-dilution cardiac output (CO) was initially measured after induction (baseline), again with HUT in the preload responsive phase, and finally when preload was restored with infusion of PE.At baseline SVV was 10 ± 3% (mean ± st.dev.), CI was 2,6 ± 0,4 L/min*m2, and SVI 43 ± 7mL/m2. With HUT SVV was 19 ± 4%, CI was 2,2 ± 0,4 L/min*m2, SVI 35 ± 7mL/m2. During PE-infusion SVV was reduced to 6 ± 3%, CI increased to 2,6 ± 0,5 L/min*m2, and SVI increased to 49 ± 11mL/m2. All differences p < 0,001. In conclusion: Infusion of phenylephrine during preload dependency increased venous return abolishing preload dependency as evaluated by SVV and increased cardiac stroke volume and -output as measured by indicator-dilution technique. (ClinicalTrials.gov NCT05193097).

In vivo optical assessment of cerebral and skeletal muscle microvascular response to phenylephrine

This study aimed to investigate the simultaneous response of the cerebral and skeletal muscle microvasculature to the same phenylephrine (PE) boluses. A hybrid optical system that combines hyperspectral near-infrared spectroscopy (hs-NIRS) and diffuse correlation spectroscopy (DCS) was used to monitor changes in tissue oxygenation and perfusion. Data were collected from the head and hind limb of seven male Sprague-Dawley rats while administering intravenous (IV) injections of PE or saline to all animals. The response to saline was used as a control. Skeletal muscle oxygenation decreased significantly after PE injection, while a statistically underpowered decrease in perfusion was observed, followed by an increase beyond baseline. Vascular conductance also decreased in the muscle reflecting the drug's vasoconstrictive effects. Tissue oxygenation and perfusion increased in the brain in response to PE. Initially, there was a sharp increase in cerebral perfusion but no changes in cerebral vascular conductance. Subsequently, cerebral flow and vascular conductance decreased significantly below baseline, likely reflecting autoregulatory mechanisms to manage the excess flow. Further, fitting an exponential function to the secondary decrease in cerebral perfusion and increase in muscular blood flow revealed a quicker kinetic response in the brain to adjust blood flow. In the skeletal muscle, PE caused a transient decrease in blood volume due to vasoconstriction, which resulted in an overall decrease in hemoglobin content and tissue oxygen saturation. Since PE does not directly affect cerebral vessels, this peripheral vasoconstriction shunted blood into the brain, resulting in an initial increase in oxygenated hemoglobin and oxygen saturation.

A retrospective study of the effects of a vasopressor bolus on systolic slope (dP/dt) and dynamic arterial elastance (Eadyn)

BACKGROUND

To enhance the utility of functional hemodynamic monitoring, the variables systolic slope (dP/dt) and dynamic arterial elastance (Eadyn) are calculated by the Hypotension Prediction Index (HPI) Acumen® Software. This study was designed to characterize the effects of phenylephrine and ephedrine on dP/dt and Eadyn.

METHODS

This was a retrospective, non-randomized analysis of data collected during two clinical studies. All patients required intra-operative controlled mechanical ventilation and had an indwelling radial artery catheter connected to an Acumen IQ sensor. Raw arterial pressure waveform data was downloaded from the patient monitor and all hemodynamic measurements were calculated off-line. The anesthetic record was reviewed for bolus administrations of either phenylephrine or ephedrine. Cardiovascular variables prior to drug administration were compared to those following vasopressor administrations. The primary outcome was the difference for dP/dt and Eadyn at baseline compared with the average after the bolus administration. All data sets demonstrated non-normal distributions so statistical analysis of paired and unpaired data followed the Wilcoxon matched pairs signed-rank test or Mann-Whitney U test, respectively.

RESULTS

201 doses of phenylephrine and 100 doses of ephedrine were analyzed. All data sets are reported as median [95% CI]. Mean arterial pressure (MAP) increased from 62 [54,68] to 78 [76,80] mmHg following phenylephrine and from 59 [55,62] to 80 [77,83] mmHg following ephedrine. Stroke volume and cardiac output both increased. Stroke volume variation and pulse pressure variation decreased. Both drugs produced significant increases in dP/dt, from 571 [531, 645] to 767 [733, 811] mmHg/sec for phenylephrine and from 537 [509, 596] to 848 [779, 930] mmHg/sec for ephedrine. No significant changes in Eadyn were observed.

CONCLUSION

Bolus administration of phenylephrine or ephedrine increases dP/dt but does not change Eadyn. dP/dt demonstrates potential for predicting the inotropic response to phenylephrine or ephedrine, providing guidance for the most efficacious vasopressor when treating hypotension.

TRIAL REGISTRATION

Data was collected from two protocols. The first was deemed to not require written, informed consent by the Institutional Review Board (IRB). The second was IRB-approved (Effect of Diastolic Dysfunction on Dynamic Cardiac Monitors) and registered on ClinicalTrials.gov (NCT04177225).

Lawrence K, Chui J, Diop M. Assessing changes in regional cerebral hemodynamics in adults with a high-density full-head coverage time-resolved near-infrared spectroscopy device

Significance

Cerebral oximeters have the potential to detect abnormal cerebral blood oxygenation to allow for early intervention. However, current commercial systems have two major limitations: (1) spatial coverage of only the frontal region, assuming that surgery-related hemodynamic effects are global and (2) susceptibility to extracerebral signal contamination inherent to continuous-wave near-infrared spectroscopy (NIRS).

Aim

This work aimed to assess the feasibility of a high-density, time-resolved (tr) NIRS device (Kernel Flow) to monitor regional oxygenation changes across the cerebral cortex during surgery.

Approach

The Flow system was assessed using two protocols. First, digital carotid compression was applied to healthy volunteers to cause a rapid oxygenation decrease across the ipsilateral hemisphere without affecting the contralateral side. Next, the system was used on patients undergoing shoulder surgery to provide continuous monitoring of cerebral oxygenation. In both protocols, the improved depth sensitivity of trNIRS was investigated by applying moment analysis. A dynamic wavelet filtering approach was also developed to remove observed temperature-induced signal drifts.

Results

In the first protocol (28 ± 5 years; five females, five males), hair significantly impacted regional sensitivity; however, the enhanced depth sensitivity of trNIRS was able to separate brain and scalp responses in the frontal region. Regional sensitivity was improved in the clinical study given the age-related reduction in hair density of the patients (65 ± 15 years; 14 females, 13 males). In five patients who received phenylephrine to treat hypotension, different scalp and brain oxygenation responses were apparent, although no regional differences were observed.

Conclusions

The Kernel Flow has promise as an intraoperative neuromonitoring device. Although regional sensitivity was affected by hair color and density, enhanced depth sensitivity of trNIRS was able to resolve differences in scalp and brain oxygenation responses in both protocols.

Effects of phenylephrine on systemic and cerebral circulations in humans: a systematic review with mechanistic explanations

We conducted a systematic review of the literature reporting phenylephrine-induced changes in blood pressure, cardiac output, cerebral blood flow and cerebral tissue oxygen saturation as measured by near-infrared spectroscopy in humans. We used the proportion change of the group mean values reported by the original studies in our analysis. Phenylephrine elevates blood pressure whilst concurrently inducing a reduction in cardiac output. Furthermore, despite increasing cerebral blood flow, it decreases cerebral tissue oxygen saturation. The extent of phenylephrine's influence on cardiac output (r = -0.54 and p = 0.09 in awake humans; r = -0.55 and p = 0.007 in anaesthetised humans), cerebral blood flow (r = 0.65 and p = 0.002 in awake humans; r = 0.80 and p = 0.003 in anaesthetised humans) and cerebral tissue oxygen saturation (r = -0.72 and p = 0.03 in awake humans; r = -0.24 and p = 0.48 in anaesthetised humans) appears closely linked to the magnitude of phenylephrine-induced blood pressure changes. When comparing the effects of phenylephrine in awake and anaesthetised humans, we found no evidence of a significant difference in cardiac output, cerebral blood flow or cerebral tissue oxygen saturation. There was also no evidence of a significant difference in effect on systemic and cerebral circulations whether phenylephrine was given by bolus or infusion. We explore the underlying mechanisms driving the phenylephrine-induced cardiac output reduction, cerebral blood flow increase and cerebral tissue oxygen saturation decrease. Individualised treatment approaches, close monitoring and consideration of potential risks and benefits remain vital to the safe and effective use of phenylephrine in acute care.

The Effect of Intraoperative Hypotension on Postoperative Renal Function

Purpose of Review

This review summarizes the most recent literature on the association between intraoperative hypotension (IOH) and the occurrence of postoperative acute kidney injury (AKI). It provides recommendations for the management of intraoperative blood pressure to reduce the incidence of postoperative AKI. Fluid management strategies, administration of vasopressor medications, and other methods for reducing the incidence of AKI are also briefly discussed.

Recent Findings

Recent retrospective studies have demonstrated a solid association of IOH with postoperative AKI. IOH is associated not only with AKI but also with myocardial infarction, stroke, and death. Strict BP management to avoid a mean blood pressure less than 65mmHg is now recommended to reduce the incidence of postoperative AKI and other adverse outcomes.

Summary

IOH is robustly associated with AKI, and intraoperative mean BP should be maintained above 65 mmHg at all times. The etiology of postoperative AKI is however multifactorial, and factors other than BP therefore also need to be considered to prevent it.

Carbonic anhydrases reduce the acidity of the tumor microenvironment, promote immune infiltration, decelerate tumor growth, and improve survival in ErbB2/HER2-enriched breast cancer

BACKGROUND

Carbonic anhydrases catalyze CO₂/HCO₃^- buffer reactions with implications for effective H⁺ mobility, pH dynamics, and cellular acid-base sensing. Yet, the integrated consequences of carbonic anhydrases for cancer and stromal cell functions, their interactions, and patient prognosis are not yet clear.

METHODS

We combine (a) bioinformatic analyses of human proteomic data and bulk and single-cell transcriptomic data coupled to clinicopathologic and prognostic information; (b) ex vivo experimental studies of gene expression in breast tissue based on quantitative reverse transcription and polymerase chain reactions, intracellular and extracellular pH recordings based on fluorescence confocal microscopy, and immunohistochemical protein identification in human and murine breast cancer biopsies; and (c) in vivo tumor size measurements, pH-sensitive microelectrode recordings, and microdialysis-based metabolite analyses in mice with experimentally induced breast carcinomas.

RESULTS

Carbonic anhydrases-particularly the extracellular isoforms CA4, CA6, CA9, CA12, and CA14-undergo potent expression changes during human and murine breast carcinogenesis. In patients with basal-like/triple-negative breast cancer, elevated expression of the extracellular carbonic anhydrases negatively predicts survival, whereas, surprisingly, the extracellular carbonic anhydrases positively predict patient survival in HER2/ErbB2-enriched breast cancer. Carbonic anhydrase inhibition attenuates cellular net acid extrusion and extracellular H⁺ elimination from diffusion-restricted to peripheral and well-perfused regions of human and murine breast cancer tissue. Supplied in vivo, the carbonic anhydrase inhibitor acetazolamide acidifies the microenvironment of ErbB2-induced murine breast carcinomas, limits tumor immune infiltration (CD3⁺ T cells, CD19⁺ B cells, F4/80⁺ macrophages), lowers inflammatory cytokine (Il1a, Il1b, Il6) and transcription factor (Nfkb1) expression, and accelerates tumor growth. Supporting the immunomodulatory influences of carbonic anhydrases, patient survival benefits associated with high extracellular carbonic anhydrase expression in HER2-enriched breast carcinomas depend on the tumor inflammatory profile. Acetazolamide lowers lactate levels in breast tissue and blood without influencing breast tumor perfusion, suggesting that carbonic anhydrase inhibition lowers fermentative glycolysis.

CONCLUSIONS

We conclude that carbonic anhydrases (a) elevate pH in breast carcinomas by accelerating net H⁺ elimination from cancer cells and across the interstitial space and (b) raise immune infiltration and inflammation in ErbB2/HER2-driven breast carcinomas, restricting tumor growth and improving patient survival.

The haemodynamic effects of phenylephrine after cardiac surgery

BACKGROUND

Phenylephrine increases systemic- and pulmonary resistances and therefore may increase blood pressures at the expense of blood flow. Cardio-pulmonary bypass alters vasoreactivity and many patients exhibit chronotropic insufficiency after cardiac surgery. We aimed to describe the haemodynamic effects of phenylephrine infusion after cardiac surgery.

METHODS

Patients in steady state after low-risk cardiac surgery received incremental infusion rates of phenylephrine up to 1.0 μg/kg/min with the aim of increasing systemic mean arterial blood pressure 20 mmHg. Invasive haemodynamic parameters, including pulmonary wedge pressures, were captured along with echocardiographic measures of biventricular function before, during phenylephrine infusion at target systemic blood pressure, and 20 min after phenylephrine discontinuation.

RESULTS

Thirty patients were included. Phenylephrine increased mean arterial pressure increased from 78 (±9) mmHg to 98 (±10) mmHg with phenylephrine infusion. Also, pulmonary blood pressure as well as systemic- and pulmonary resistances increased. The ratio between systemic- and pulmonary artery resistances did not change statistically significantly (p = .59). Median cardiac output was 4.35 (interquartile range [IQR] 3.6-5.4) L/min at baseline and increased significantly with phenylephrine infusion (median Δcardiac output was 0.25 [IQR 0.1-0.6] L/min) (p = .012). Pulmonary artery wedge pressure increased from 10.2 (±3.0) mmHg to 11.9 (±3.4) mmHg (p < .001). This was accompanied by significant increases in central venous pressure. Phenylephrine infusion increased left ventricular end-diastolic volume from 105 (±46) mL to 119 (±44) mL (p < .001). All results of phenylephrine infusion were reversed with discontinuation.

CONCLUSION

In haemodynamically stable patients after cardiac surgery, phenylephrine increased PVR and SVR, but did not change the PVR/SVR ratio. Phenylephrine increased biventricular filling pressures and left ventricular end-diastolic area. Consequently, CO increased as ejection fraction was maintained. These findings do not discourage the use of phenylephrine after low-risk cardiac surgery.

REGISTRATION

clinicaltrial.gov (identifier NCT04419662).

Norepinephrine combined with phenylephrine versus norepinephrine in patients with septic shock: a retrospective cohort study

BACKGROUND

Phenylephrine (PE) and norepinephrine (NE) may be used to maintain adequate blood pressure and tissue perfusion in patients with septic shock, but the effect of NE combined with PE (NE-PE) on mortality remains unclear. We hypothesized that NE-PE would not inferior to NE alone for all-cause hospital mortality in patients with septic shock.

METHODS

This single-center, retrospective cohort study included adult patients with septic shock. According to the infusion type, patients were divided into the NE-PE or NE group. Multivariate logistic regression, propensity score matching and doubly robust estimation were used to analyze the differences between groups. The primary outcome was the all-cause hospital mortality rate after NE-PE or NE infusion.

RESULTS

Among 1, 747 included patients, 1, 055 received NE and 692 received NE-PE. For the primary outcome, the hospital mortality rate was higher in patients who received NE-PE than in those who received NE (49.7% vs. 34.5%, p < 0.001), and NE-PE was independently associated with higher hospital mortality (odds ratio = 1.76, 95% confidence interval = 1.36-2.28, p < 0.001). Regarding secondary outcomes, patients in the NE-PE group had longer lengths of stay in ICU and hospitals. Patients in the NE-PE group also received mechanical ventilation for longer durations.

CONCLUSIONS

NE combined with PE was inferior to NE alone in patients with septic shock, and it was associated with a higher hospital mortality rate.

Photoelectrochemical imaging of single cardiomyocytes and monitoring of their action potentials through contact force manipulation of organoids

Accurate monitoring of cardiomyocyte action potentials (APs) is essential to understand disease propagation and for trials of novel therapeutics. Patch clamp techniques offer 'gold standard' measurements in this field, but are notoriously difficult to operate and only provide measurements of a single cell. Here we propose photoelectrochemical imaging (PEI) with light-addressable potentiometric sensors (LAPS) in conjunction with a setup for controlling the contact force between the cardiomyocyte organoids and the sensor surface for measuring APs with high sensitivity. The method was validated through measuring the responses to drugs, and the results successfully visualized the expected electrophysiological changes to the APs. PEI allows for several cells to be monitored simultaneously, opening further research to the electrophysiological interactions of adjoining cells. This method expands the applications of PEI to three-dimensional geometries and provides the fields of stem cell research, drug trials and heart disease modelling with an invaluable tool to further investigate the role of APs.

Acute Pulmonary Edema During a Cesarean Delivery After an Adverse Drug Event

Acute pulmonary edema (APEd) is rare in pregnancy and in the postpartum period. An intermediate type of APEd characterized as a transudate with a protein concentration between that of cardiogenic and noncardiogenic APEd has been described in the literature. This transudate might actually be the result of capillary pressure having increased to a point of high-permeability edema and/or alveolar hemorrhage. Clinically, the presentation would be a dramatic form of APEd - flash pulmonary edema - characterized by a rapid accumulation of fluid within the lung's interstitial and alveolar spaces as a result of suddenly elevated cardiac filling pressures. Here, we present a case of a healthy pregnant woman who underwent cesarean delivery and developed a constellation of signs and symptoms, suggestive of an APEd, after a supratherapeutic bolus of phenylephrine. During the diagnostic excursion, bilateral parenchymal infiltrations suggestive of hemorrhage were observed on a computed tomography scan. This case highlights the high morbidity associated with adverse drug events and the imperative to prevent them. It also underscores the critical need for careful management of volume shifts and hemodynamics in full-term pregnancies.

Vasopressors and Risk of Acute Mesenteric Ischemia: A Worldwide Pharmacovigilance Analysis and Comprehensive Literature Review

Vasodilatory shock, such as septic shock, requires personalized management which include adequate fluid therapy and vasopressor treatments. While these potent drugs are numerous, they all aim to counterbalance the vasodilatory effects of a systemic inflammatory response syndrome. Their specific receptors include α- and β-adrenergic receptors, arginine-vasopressin receptors, angiotensin II receptors and dopamine receptors. Consequently, these may be associated with severe adverse effects, including acute mesenteric ischemia (AMI). As the risk of AMI depends on drug class, we aimed to review the evidence of plausible associations by performing a worldwide pharmacovigilance analysis based on the World Health Organization database, VigiBase®. Among 24 million reports, 104 AMI events were reported, and disproportionality analyses yielded significant association with all vasopressors, to the exception of selepressin. Furthermore, in a comprehensive literature review, we detailed mechanistic phenomena which may enhance vasopressor selection, in the course of treating vasodilatory shock.

The Regulatory Mechanism and Effect of RIPK3 on PE-induced Cardiomyocyte Hypertrophy

ABSTRACT

As a critical regulatory molecule, receptor-interacting protein kinase 3 (RIPK3) can mediate the signaling pathway of programmed necrosis. Calcium/calmodulin-dependent protein kinase II (CaMKII) has been proved as a new substrate for RIPK3-induced necroptosis. In the present study, we aimed to investigate the regulatory mechanism of RIPK3 on phenylephrine (PE)-induced cardiomyocyte hypertrophy. Cardiomyocyte hypertrophy was induced by exposure to PE (100 μM) for 48 h. Primary cardiomyocytes were pretreated with RIPK3 inhibitor GSK'872 (10 μM), and RIPK3 siRNA was used to deplete the intracellular expression of RIPK3. The indexes related to myocardial hypertrophy, cell injury, necroptosis, CaMKII activation, gene expression, oxidative stress, and mitochondrial membrane potential were measured. We found that after cardiomyocytes were stimulated by PE, the expressions of hypertrophy markers, atrial and brain natriuretic peptides (ANP and BNP), were increased, the release of lactate dehydrogenase (LDH) was increased, the level of adenosine triphosphate (ATP)was decreased, the oxidation and phosphorylation levels of CaMKII were increased, and CaMKIIδ alternative splicing was disturbed. However, both GSK'872 and depletion of RIPK3 could reduce myocardial dysfunction, inhibit CaMKII activation and necroptosis, and finally alleviate myocardial hypertrophy. In addition, the pretreatment of RIPK3 could also lessen the accumulation of reactive oxygen species (ROS) induced by PE and stabilize the membrane potential of mitochondria. These results indicated that targeted inhibition of RIPK3 could suppress the activation of CaMKII and reduce necroptosis and oxidative stress, leading to alleviated myocardial hypertrophy. Collectively, our findings provided valuable insights into the clinical treatment of hypertrophic cardiomyopathy.

The effect of vasoconstriction on intestinal perfusion is determined by preload dependency: A prospective observational study

BACKGROUND

The effects of vasoconstriction on cardiac stroke volume (SV) and indices of peripheral and intestinal perfusion are insufficiently described.

METHODS

In a non-randomized clinical study, 30 patients undergoing elective rectal surgery were exposed to modulation of preload. The primary endpoint was intestinal perfusion (flux), measured by single-point laser Doppler flowmetry. Secondary endpoints were central cardiovascular variables obtained by the LiDCO rapid monitor, the peripheral perfusion index (PPI) derived from the pulse oximetry signal and muscle (StO₂ ) and cerebral oxygenation (ScO₂ ) determined by near-infrared spectroscopy.

RESULTS

For the whole cohort (n = 30), administration of Phenylephrine during HUT induced a median [IQR] increase in SV by 22% [14-41], p = .003 and in mean arterial pressure (MAP) by 54% [31-62], p < .001, with no change in PPI, StO₂ and ScO₂ or flux. In patients who were preload dependent during HUT (stroke volume variation; SSV >10%; n = 23), administration of phenylephrine increased SV by 29% [12-43], p = .01 and MAP by 54% [33-63], p < .001, followed by an increase in intestinal perfusion flux by 60% [15-289], p = .05, while PPI, StO₂ and ScO₂  remained unchanged. For non-preload dependent patients (SSV <10%; n = 7), no changes in hemodynamic indices were seen besides an increase in MAP by 54% [33-58], p = .002.

CONCLUSION

The reflection of vasoconstrictive modulation of preload in systemic cardiovascular variables and indices of perfusion was dependent on preload responsiveness. Administration of phenylephrine to increase preload did not appear to compromise organ perfusion.

Phenylephrine-Induced Cardiovascular Changes in the Anesthetized Mouse: An Integrated Assessment of in vivo Hemodynamics Under Conditions of Controlled Heart Rate

Objective

Investigating the cardiovascular system is challenging due to its complex regulation by humoral and neuronal factors. Despite this complexity, many existing research methods are limited to the assessment of a few parameters leading to an incomplete characterization of cardiovascular function. Thus, we aim to establish a murine in vivo model for integrated assessment of the cardiovascular system under conditions of controlled heart rate. Utilizing this model, we assessed blood pressure, cardiac output, stroke volume, total peripheral resistance, and electrocardiogram (ECG).

Hypothesis

We hypothesize that (i) our in vivo model can be utilized to investigate cardiac and vascular responses to pharmacological intervention with the α₁-agonist phenylephrine, and (ii) we can study cardiovascular function during artificial pacing of the heart, modulating cardiac function without a direct vascular effect.

Methods

We included 12 mice that were randomly assigned to either vehicle or phenylephrine intervention through intraperitoneal administration. Mice were anesthetized with isoflurane and intubated endotracheally for mechanical ventilation. We measured blood pressure via a solid-state catheter in the aortic arch, blood flow via a probe on the ascending aorta, and ECG from needle electrodes on the extremities. Right atrium was electrically paced at a frequency ranging from 10 to 11.3 Hz before and after either vehicle or phenylephrine administration.

Results

Phenylephrine significantly increased blood pressure, stroke volume, and total peripheral resistance compared to the vehicle group. Moreover, heart rate was significantly decreased following phenylephrine administration. Pacing significantly decreased stroke volume and cardiac output both prior to and after drug administration. However, phenylephrine-induced changes in blood pressure and total peripheral resistance were maintained with increasing pacing frequencies compared to the vehicle group. Total peripheral resistance was not significantly altered with increasing pacing frequencies suggesting that the effect of phenylephrine is primarily of vascular origin.

Conclusion

In conclusion, this in vivo murine model is capable of distinguishing between changes in peripheral vascular and cardiac functions. This study underlines the primary effect of phenylephrine on vascular function with secondary changes to cardiac function. Hence, this in vivo model is useful for the integrated assessment of the cardiovascular system.

Effect of 15° Reverse Trendelenburg Position on Arterial Oxygen Tension during Isoflurane Anesthesia in Horses

Simple Summary

Horses commonly develop low blood oxygen levels during anesthesia, especially when they are placed on their backs. This study investigated whether a 15° head-up tilt, in a homogenous group of anesthetized horses positioned on their backs, would result in better blood oxygen levels as compared to no tilt. The results showed significantly greater blood oxygen levels with tilt compared to no tilt in five out of six horses tested. In one horse the effect was the opposite. The concurrent effect on cardiovascular function remains to be tested in detail. Further studies are needed to confirm these findings in a larger group of horses and to determine the effects on blood pressure and treatment options.

Abstract

Lower than expected arterial oxygen tension (PaO₂) continues to be an unresolved problem in equine anesthesia. The aim of this randomized, crossover, and prospective study using six adult horses is to determine if a 15° reverse Trendelenburg position (RTP) increases PaO₂ during inhalation anesthesia. Under constant-dose isoflurane anesthesia, dorsally recumbent horses were positioned either horizontally (HP) or in a 15° RTP for 2 h. Lungs were mechanically ventilated (15 mL/kg, 6 breaths/min). Arterial carbon dioxide tension (PaCO₂), PaO₂, inspired oxygen fraction (FiO₂), and end-tidal carbon dioxide tension (EtCO₂) were determined every 30 min during anesthesia. Indices of dead-space ventilation (Vd/Vt), oxygenation (P–F ratio), and perfusion (F–shunt) were calculated. Dobutamine and phenylephrine were used to support mean arterial pressure (MAP). Data are presented as median and range. In one horse, which was deemed an outlier due to its thoracic dimensions and body conformation, indices of oxygenation worsened in RTP compared to HP (median PaO₂ 438 vs. 568 mmHg; P–F ratio 454 vs. 586 mmHg, and F–shunt 13.0 vs. 5.7 mmHg). This horse was excluded from calculations. In the remaining five horses they were significantly better with RTP compared to HP. Results in remaining five horses showed that PaO₂ (502, 467–575 vs. 437, 395–445 mmHg), P-F ratio (518, 484–598 vs. 455, 407–458 mmHg), and F-shunt (10.1, 4.2–11.7 vs. 14.2, 13.8–16.0 mmHg) were significantly different between RTP and HP (p = 0.03). Other variables were not significantly different. In conclusion, the 15° RTP resulted in better oxygenation than HP in dorsally recumbent, isoflurane-anesthetized horses, although worsening of oxygenation may occur in individual horses. A study detailing the cardiovascular consequences of RTP is necessary before it can be recommended for clinical practice.

Over a century since ephedrine discovery: an updated revisit to its pharmacological aspects, functionality and toxicity in comparison to its herbal extracts

Ephedrine, a sympathomimetic amine that exhibits several adrenaline actions, is a plant alkaloid that is a common ingredient in several cold, asthma and narcolepsy treatment preparations, and in obesity management and sport medicine. Its principal action mechanism relies on its direct adrenergic actions as well as indirect role that involves the release of epinephrine and norepinephrine, thus increasing the activity of epinephrine and norepinephrine at the postsynaptic α and β receptors. Nevertheless, its serious side effects, including stroke, heart attack, drug abuse and interactions, have never been comprehensively reviewed. We conducted a systematic review of data on ephedrine, including its occurrence in functional foods, pharmacological aspects, metabolism, pharmaco/toxicokinetics and clinical features. Furthermore, a review of ephedrine natural structural analogues with regards to their differential adrenergic receptor binding affinities, food interaction, and their impact on the pharmacokinetics and effects relative to ephedrine are presented for the first time, and in comparison to its action when present in herbs.

Hemodynamic and Intestinal Microcirculatory Changes in a Phenylephrine Corrected Porcine Model of Hemorrhage

BACKGROUND

Intraoperative hypotension is a common event, and a recent study suggests that maintenance of blood pressure may reduce complications. The splanchnic circulation provides a reservoir of blood that can be mobilized during hemorrhage; hence, intestinal microcirculation is sensitive to volume changes. The aim of this study was to assess the impact of hemorrhage on intestinal microcirculation and hemodynamics, and the effects of phenylephrine on these parameters.

METHODS

Eight anesthetized, mechanically ventilated Yorkshire/Landrace crossbreed pigs were studied. Graded hemorrhage was performed with the removal of 20% of blood volume in 5% increments. Hemodynamic and intestinal microcirculatory measurements were performed at each stage with side-stream dark field microscopy, following which mean arterial pressure (MAP) was corrected with phenylephrine to baseline values and measurements repeated. A repeated measurement 1-way analysis of variance (ANOVA) was used to compared changes from baseline measurements.

RESULTS

The mean baseline microcirculation score was 42 (standard deviation [SD] = 5). A 5% hemorrhage decreased the microcirculation score by a mean difference of 19 (95% confidence interval [CI], 12-27; P < .0001), and an additional 5% hemorrhage further reduced the microcirculation score by a mean difference of 12 (95% CI, 4-19; P = .0001). Subsequent hemorrhage or administration of phenylephrine did not significantly change the microcirculation scores except when phenylephrine was administered at the 15% hemorrhage stage, which increased the microcirculation score by a mean difference of 7 (95% CI, 1-13; P = .003). All hemodynamic variables were returned to baseline values following hemorrhage by the phenylephrine infusion.

CONCLUSIONS

Intestinal microcirculatory flow is reduced early in hemorrhage and is uncorrected by phenylephrine infusion. Hemodynamic changes associated with hemorrhage are corrected by phenylephrine and do not reflect microcirculatory flow status.

Causes of arterial hypotension during anesthetic induction with propofol investigated with perfusion index and ClearSightTM in young and elderly patients

BACKGROUND

Mechanism underlying the hypotension during anesthetic induction in elderly patients is inferred to differ from that in younger patients due to structural changes in arteries. The aim of the study was to determine if a decrease in cardiac output (CO) or systemic vascular resistance (SVR) is the main mechanism of the hypotension.

METHODS

Fifty-six patients comprising 28 healthy elderly patients aged 75-90 years (group E) and 28 healthy younger patients aged 20-40 years (group Y) were enrolled. General anesthesia was induced with propofol (1.2 mg/kg, group E; 2 mg/kg, group Y), remifentanil (0.15 µg/kg/min, group E; 0.3 µg/kg/min, group Y) and rocuronium. Primary outcome was to compare serial changes in PI of Radical-7^TM, SVR, CO and stroke volume variations (SVV) of ClearSight^TM (Edwards Lifesciences Corp., Irvine, CA, USA) during the five-minute period from propofol administration until intubation.

RESULTS

The degree of increase in PI and reduction in SVR in group Y were significantly greater than those in group E (P<0.01 with repeated measure ANOVA). The degree of reduction in CO and increase in SVV were significantly larger in group E (P<0.01). All values of mean arterial blood pressure measured during the five-minute correlated negatively with PI in group Y (r=0.44, P<0.01) and positively with CO in group E (r=0.4, P<0.01).

CONCLUSIONS

The main mechanisms of hypotension during anesthetic induction contribute to the decrease in CO in elderly and reduction of SVR in younger. PI only shows the vascular tone of a finger but can be a surrogate for SVR.

Effects of dobutamine and phenylephrine on cerebral perfusion in patients undergoing cerebral bypass surgery: a randomised crossover trial

Background

Patients undergoing cerebral bypass surgery are prone to cerebral hypoperfusion. Currently, arterial blood pressure is often increased with vasopressors to prevent cerebral ischaemia. However, this might cause vasoconstriction of the graft and cerebral vasculature and decrease perfusion. We hypothesised that cardiac output, rather than arterial blood pressure, is essential for adequate perfusion and aimed to determine whether dobutamine administration resulted in greater graft perfusion than phenylephrine administration.

Methods

This randomised crossover study included 10 adult patients undergoing cerebral bypass surgery. Intraoperatively, patients randomly and sequentially received dobutamine to increase cardiac index or phenylephrine to increase mean arterial pressure (MAP). An increase of >10% in cardiac index or >10% in MAP was targeted, respectively. Before both interventions, a reference phase was implemented. The primary outcome was the absolute difference in graft flow between the reference and intervention phase. We compared the absolute flow difference between each intervention and constructed a random-effect linear regression model to explore treatment and carry-over effects.

Results

Graft flow increased with a median of 4.1 (inter-quartile range [IQR], 1.7–12.0] ml min⁻¹) after dobutamine administration and 3.6 [IQR, 1.3–7.8] ml min⁻¹ after phenylephrine administration (difference –0.6 ml min⁻¹; 95% confidence interval [CI], –14.5 to 5.3; P=0.441). There was no treatment effect (0.9 ml min⁻¹; 95% CI, 0.0–20.1; P=0.944) and no carry-over effect.

Conclusions

Both dobutamine and phenylephrine increased graft flow during cerebral bypass surgery, without a preference for one method over the other.

Clinical trial registration

Netherlands Trial Register, NL7077 (https://www.trialregister.nl/trial/7077).

Perioperative Quality Initiative (POQI) consensus statement on fundamental concepts in perioperative fluid management: fluid responsiveness and venous capacitance

Background

Optimal fluid therapy in the perioperative and critical care settings depends on understanding the underlying cardiovascular physiology and individualizing assessment of the dynamic patient state.

Methods

The Perioperative Quality Initiative (POQI-5) consensus conference brought together an international team of multidisciplinary experts to survey and evaluate the literature on the physiology of volume responsiveness and perioperative fluid management. The group used a modified Delphi method to develop consensus statements applicable to the physiologically based management of intravenous fluid therapy in the perioperative setting.

Discussion

We discussed the clinical and physiological evidence underlying fluid responsiveness and venous capacitance as relevant factors in fluid management and developed consensus statements with clinical implications for a broad group of clinicians involved in intravenous fluid therapy. Two key concepts emerged as follows: (1) The ultimate goal of fluid therapy and hemodynamic management is to support the conditions that enable normal cellular metabolic function in order to produce optimal patient outcomes, and (2) optimal fluid and hemodynamic management is dependent on an understanding of the relationship between pressure, volume, and flow in a dynamic system which is distensible with variable elastance and capacitance properties.

Hypotension during hip fracture surgery and postoperative morbidity

Background

Hip fracture is a growing healthcare challenge, with 6–8% 30-day mortality and 20–30% of patients incurring major morbidity, including impaired mobilisation and ability to live independently. While observational studies have shown no benefit of general versus spinal anaesthesia on 30-day mortality, intraoperative hypotension during hip fracture surgery is associated with increased 30-day mortality regardless of anaesthetic technique. Although a recent trial on younger patients demonstrated reduced postoperative complications by maintaining intraoperative arterial blood pressure close to preoperative baseline, there are no data correlating intraoperative hypotension during hip fracture surgery with postoperative morbidity.

Objective

We evaluated the hypothesis that duration and severity of intraoperative hypotension during hip fracture surgery is associated with increased postoperative morbidity.

Methods

A retrospective analysis was carried out on n = 52 patients undergoing hip fracture surgery between January and June 2017. Measurements of patients’ intraoperative systolic arterial pressure (SAP) and mean arterial pressure (MAP) during anaesthesia, logged electronically through an anaesthesia information management system, were reviewed. We calculated the total duration of time where SAP or MAP were below pre-defined thresholds for hypotension (MAP < 75 mmHg, MAP < 55 mmHg, SAP ≤ 80% admission baseline or SAP ≤ 80% pre-induction baseline). Univariate and bivariate descriptive statistics were generated for all relevant variables. With multivariable regression models containing known predictors, cumulative duration of hypotension was correlated with postoperative comorbidities as quantified by the Clavien-Dindo and Comprehensive Complication Indices.

Results

Mean age (± SD) was 78 ± 13 years, 75% were female, 87% were ASA II or III and 60% underwent spinal anaesthesia. Mean Comprehensive Complication Index was 20.4 ± 19.2. Lowest absolute SAP and MAP values were 82 ± 18 mmHg and 55 ± 12 mmHg respectively. Cumulative time of SAP < 80% pre-induction value adjusted to gender, age and the Charlson Comorbidity Index was associated with progression to a higher Clavien-Dindo classification (odds ratio 1.020 per additional minute; 95% CI 1.008–1.035; P = 0.003).

Conclusions

In this exploratory retrospective analysis, the cumulative time of hypotension during hip fracture surgery correlated with extensive postoperative morbidity when adjusting to other known predictors. Intraoperative cumulative time of hypotension may be a good candidate for larger prediction studies as a predictor of postoperative complications. A randomised controlled trial evaluating the effect of actively minimising intraoperative hypotension on postoperative morbidity in hip fracture patients seems warranted.

Effects of remote ischemic preconditioning on regional cerebral oxygen saturation in patients in the beach chair position during shoulder surgery: A double-blind randomized controlled trial

STUDY OBJECTIVE

The beach chair position for shoulder surgery induces cerebral hypoperfusion. We evaluated the effects of remote ischemic preconditioning (RIPC) prior to surgery to ameliorate cerebral desaturation in a double-blind randomized fashion.

DESIGN

Blinded, prospective, randomized study.

SETTING

Operating room & postoperative recovery room, tertiary university hospital.

PATIENTS

Seventy patients scheduled for shoulder surgery were recruited. After excluding 7 patients according to the exclusion criteria, 63 patients were randomized into two groups (control and RIPC).

INTERVENTIONS

Remote ischemic preconditioning was applied by briefly inflating a tourniquet on the thigh three times just after inducing anesthesia in the RIPC group.

MEASUREMENTS

The changes in regional cerebral oxygen saturation, hemodynamic values, laboratory values, and serum levels of cytokines including interleukin (IL)-1β, IL-6, IL-10 and transforming growth factor-β were measured.

MAIN RESULTS

The remote ischemic preconditioning group had higher regional cerebral oxygen saturation just after establishment of the beach chair position (P = 0.002) and lower cerebral desaturation (P = 0.007) during operation than the control group. Hemodynamic and laboratory values did not differ between the groups. There were no significant intergroup differences in cytokine levels.

CONCLUSION

Remote ischemic preconditioning before surgery ameliorates cerebral desaturation in patients in the beach chair position during shoulder surgery. Trial Registry Number: KCT0001384 (http://cris.nih.go.kr).

Journal of clinical monitoring and computing end of year summary 2018: hemodynamic monitoring and management

Hemodynamic management is a mainstay of patient care in the operating room and intensive care unit (ICU). In order to optimize patient treatment, researchers investigate monitoring technologies, cardiovascular (patho-) physiology, and hemodynamic treatment strategies. The Journal of Clinical Monitoring and Computing (JCMC) is a well-established and recognized platform for publishing research in this field. In this review, we highlight recent advancements and summarize selected papers published in the JCMC in 2018 related to hemodynamic monitoring and management.

Journal of Clinical Monitoring and Computing 2017/2018 end of year summary: monitoring-and provocation-of the microcirculation and tissue oxygenation

The microcirculation is the ultimate goal of hemodynamic optimization in the perioperative and critical care setting. In this fourth end-of-year summary of the Journal of Clinical Monitoring and Computing on this topic, we take a closer look at papers published in the last 2 years that focus on this important aspect. The majority of these papers investigated the use of either cerebral or peripheral tissue oxygen saturation, derived non-invasively using near infrared spectroscopy (NIRS). In some of these studies, the microcirculation was “provocated” by inducing short-term tissue hypoxia, allowing the assessment of functional microvascular reserve. Additionally, studies on technical differences between NIRS monitors are summarized, as well as studies investigating the feasibility of NIRS monitoring, mainly in the pediatric patient population. Last but not least, novel monitoring tools allow assessing oxygenation at a (sub)cellular level, and those papers incorporating these techniques are also reviewed here.