Femoral Arterial Blood Pressure Research Articles

Age- and sex-related differences in sympathetic vascular transduction and neurohemodynamic balance in humans.

Bursts of muscle sympathetic nerve activity (MSNA) and the ensuing vasoconstriction are pivotal determinants of beat-by-beat blood pressure regulation. Although age and sex impact blood pressure regulation, how these factors affect the central and peripheral arcs of the baroreflex remains unclear. In 27 young [25 (SD 3) yr] males (YM; n = 14) and females (YF; n = 13) and 23 older [71 (SD 5) yr] males (OM; n = 11) and females (OF; n = 12), femoral artery blood flow, blood pressure, and MSNA were recorded for 10 min of supine rest. Sympathetic baroreflex sensitivity (i.e., central arc) was quantified as the relationship between diastolic blood pressure and MSNA burst incidence. Signal averaging was used to determine sympathetic vascular transduction into leg vascular conductance (LVC) for 12 cardiac cycles following MSNA bursts (i.e., peripheral arc). Older adults demonstrated attenuated sympathetic transduction into LVC (both P < 0.001) following MSNA bursts, and smaller increases in sympathetic transduction as a function of MSNA burst size and firing pattern compared with young adults (range, P = 0.004-0.032). YM (r2 = 0.36; P = 0.032) and OM (r2 = 0.51; P = 0.014) exhibited an inverse relationship between the central and peripheral arcs of the baroreflex, whereas females did not (YF, r2 = 0.03, P = 0.621; OF, r2 = 0.06, P = 0.445). MSNA burst incidence was inversely related to sympathetic transduction in YM and OF (range, P = 0.03-0.046) but not in YF or OM (range, P = 0.360-0.603). These data indicate that age is associated with attenuated sympathetic vascular transduction, whereas age- and sex-specific changes are present in the relationship between the central and peripheral arcs of the baroreflex regulation of blood pressure.NEW & NOTEWORTHY Sympathetic vascular transduction is attenuated in older compared with young adults, regardless of biological sex. Males, but not females (regardless of age), demonstrate an inverse relationship between central (sympathetic baroreflex sensitivity) and peripheral (sympathetic vascular transduction) components of the baroreflex arc. Young males and older females exhibit an inverse relationship between resting sympathetic outflow and sympathetic vascular transduction. Our results indicate that age and sex exert independent and interactive effects on sympathetic vascular transduction and sympathetic neurohemodynamic balance in humans.

Pharmacological modulation of adrenergic tone alters the vasodilatory response to passive leg movement in young but not in old adults.

The age-related increase in α-adrenergic tone may contribute to decreased leg vascular conductance (LVC) both at rest and during exercise in the old. However, the effect on passive leg movement (PLM)-induced LVC, a measure of vascular function, which is markedly attenuated in this population, is unknown. Thus, in eight young (25 ± 5 yr) and seven old (65 ± 7 yr) subjects, this investigation examined the impact of systemic β-adrenergic blockade (propanalol, PROP) alone, and PROP combined with either α1-adrenergic stimulation (phenylephrine, PE) or α-adrenergic inhibition (phentolamine, PHEN), on PLM-induced vasodilation. LVC, calculated from femoral artery blood flow and pressure, was determined and PLM-induced Δ peak (LVCΔpeak) and total vasodilation (LVCAUC, area under curve) were documented. PROP decreased LVCΔpeak (PROP: 4.8 ± 1.8, Saline: 7.7 ± 2.7 mL·mmHg-1, P < 0.001) and LVCAUC (PROP: 1.1 ± 0.7, Saline: 2.4 ± 1.6 mL·mmHg-1, P = 0.002) in the young, but not in the old (LVCΔpeak, P = 0.931; LVCAUC, P = 0.999). PE reduced baseline LVC (PE: 1.6 ± 0.4, PROP: 2.3 ± 0.4 mL·min-1·mmHg-1, P < 0.01), LVCΔpeak (PE: 3.2 ± 1.3, PROP: 4.8 ± 1.8 mL·min-1·mmHg-1, P = 0.004), and LVCAUC (PE: 0.5 ± 0.4, PROP: 1.1 ± 0.7 mL·mmHg-1, P = 0.011) in the young, but not in the old (baseline LVC, P = 0.199; LVCΔpeak, P = 0.904; LVCAUC, P = 0.823). PHEN increased LVC at rest and throughout PLM in both groups (drug effect: P < 0.05), however LVCΔpeak was only improved in the young (PHEN: 6.4 ± 3.1, PROP: 4.4 ± 1.5 mL·min-1·mmHg-1, P = 0.004), and not in the old (P = 0.904). Furthermore, the magnitude of α-adrenergic modulation (PHEN - PE) of LVCΔpeak was greater in the young compared with the old (Young: 3.35 ± 2.32, Old: 0.40 ± 1.59 mL·min-1·mmHg-1, P = 0.019). Therefore, elevated α-adrenergic tone does not appear to contribute to the attenuated vascular function with age identified by PLM.NEW & NOTEWORTHY Stimulation of α1-adrenergic receptors eliminated age-related differences in passive leg movement (PLM) by decreasing PLM-induced vasodilation in the young. Systemic β-blockade attenuated the central hemodynamic component of the PLM response in young individuals. Inhibition of α-adrenergic receptors did not improve the PLM response in older individuals, though withdrawal of α-adrenergic modulation augmented baseline and maximal vasodilation in both groups. Accordingly, α-adrenergic signaling plays a role in modulating the PLM vasodilatory response in young but not in old adults, and elevated α-adrenergic tone does not appear to contribute to the attenuated vascular function with age identified by PLM.

Central Versus Peripheral Invasive Arterial Blood Pressure Monitoring in Liver Transplant Surgery.

Introduction Invasive blood pressure monitoring is essential in liver transplant surgery due to expected major hemodynamic shifts.The use of central versusperipheral arterial access, however, is institution-dependent, which can affect clinical decisions regarding vasopressor therapy.Although there are studies that demonstrate inconsistencies based on arterial cannulation sites, few studies have compared femoral and radial artery blood pressures in patients undergoing liver transplant surgery.To our knowledge, there are no studies investigating the differences between continuous minute-to-minute femoral and radial artery measurements during all three phases of liver transplant surgery. Objective The main objective of this study was to evaluate for any differences between central and peripheral blood pressure measurements in liver transplant surgeryand to assess for any correlation between vasopressor infusion dose and femoral-arterial pressure differences. Methods In this retrospective study, we reviewed and studied the data of 61 patientswith American Society of Anesthesiologists (ASA) grade 4who underwent liver transplant surgery at Loma Linda University Medical Center between January and December of 2019.All patients had both femoral and radial arterial lines placed for liver transplant surgery.Femoral and radial arterial blood pressure values were obtained continuously over 60 minutes in the pre-anhepatic phase, 45 minutes during the anhepatic phase, and 60 minutes into the neo-hepatic phase. Vasopressor infusion doses were also recorded for each patient during these time frames. Results This pilot study found statistically significant differences between the mean femoral and radial systolic blood pressure (SBP; p < 0.0001), diastolic blood pressure (DBP; p < 0.0001), and mean arterial pressure (MAP; p < 0.0001)during all phases of liver transplantation.The meanSBP and MAP differences between femoral and radial arteries were highest (femoral blood pressure reading higher than radial blood pressure measurements) in the late anhepatic and early neo-hepatic phases with SBP differences of 20.8 ± 0.8 mmHg and 22.8 ± 0.8 mmHg, respectively, and MAP differences of 10.0 ± 0.4 mmHg and 9.8 ± 0.4 mmHg, respectively. Higher vasopressor infusion doses were strongly associated with greater differences in femoral-radial SBP and MAP measurements (r = 0.69 for vasopressin, 0.68 for norepinephrine, and 0.68 for epinephrine; p < 0.0001) during the anhepatic phase. Conclusions Peripheral invasive blood pressure monitoring may result in underestimation of the central blood pressure, as was seen in all phases of liver transplantation. This may lead to excessive vasopressor use with potentially adverse effects. Although the cause for the difference between femoral and radial artery measurements is unclear, increasing vasopressor infusion dosages appears to contribute. Femoral artery blood pressure monitoring allows clinicians to interpret hemodynamic status and administer appropriate vasopressors more accurately.

The Sheep as a Comprehensive Animal Model to Investigate Interdependent Physiological Pressure Propagation and Multiparameter Influence on Cerebrospinal Fluid Dynamics.

The present study aims to develop a suitable animal model for evaluating the physiological interactions between cerebrospinal fluid (CSF) dynamics, hemodynamics, and abdominal compartment pressures. We seek to contribute to the enhanced recognition of the pathophysiology of CSF-dependent neurological disorders like hydrocephalus and the improvement of available treatment options. To date, no comprehensive animal model of CSF dynamics exists, and establishing an accurate model will advance our understanding of complex CSF physiology. Persisting knowledge gaps surrounding the communication and pressure propagation between the cerebrospinal space and adjacent anatomical compartments exacerbate the development of novel therapies for neurological diseases. Hence, the need for further investigation of the interactions of vascular, craniospinal, and abdominal pressures remains beyond dispute. Moreover, the results of this animal study support the optimization of in vitro test benches for medical device development, e.g., ventriculoperitoneal shunts. Six female white alpine sheep were surgically equipped with pressure sensors to investigate the physiological values of intracranial, intrathecal, arterial, central venous, jugular venous, vesical pressure, and four differently located abdominal pressures. These values were measured simultaneously during the acute animal trial with sheep under general anesthesia. Both carotid and femoral arterial blood pressure indicate a reliable and comparable representation of the systematic blood pressure. However, the jugular venous pressure and the central venous pressure in sheep in dorsal recumbency do not correlate well under general anesthesia. Furthermore, there is a trend for possible comparability of lateral intraventricular and lumbar intrathecal pressure. Nevertheless, animal body position during measurements must be considered since different body constitutions can alter the horizontal line between the cerebral ventricles and the lumbar subarachnoid space. While intra-abdominal pressure measurement in the four different abdominal quadrants yielded greater inter-individual variability, intra-vesical pressure measurements in our setting delivered comparable values for all sheep. We established a novel and comprehensive ovine animal model to investigate interdependent physiologic pressure propagation and multiparameter influences on CSF dynamics. The results of this study will contribute to further in vitro bench testing, the derivation of novel quantitative models, and the development of a pathologic ovine hydrocephalus model.

Using noninvasive adjusted pulse transit time for tracking beat-to-beat systolic blood pressure during ventricular arrhythmia.

Tracking beat-to-beat blood pressure noninvasively during ventricular arrhythmia (VA) is of great importance but rarely reported. The goal of our study was to investigate the potential utility of the adjusted pulse transit time (APTT) to track beat-to-beat femoral systolic blood pressure (SBP) during VA. Patients who underwent radiofrequency ablation for arrhythmias at Fuwai Hospital were enrolled. Electrocardiograms (ECGs), finger photoplethysmograms, and femoral arterial blood pressure were recorded simultaneously during VA. The APTT was calculated as the ratio between the square of the conventional pulse transit time (cPTT) and the RR interval of the ECG waveform. Forty-five patients were enrolled in our study, and 22,849 beats were collected during their VA. The inverse of the APTT showed a good correlation with femoral SBP during VA (r = 0.70 ± 0.18). The APTT-derived SBP demonstrated acceptable accuracy in terms of the mean difference ± standard deviation (-0.01 ± 10.54 mmHg) from the invasive femoral SBP. The area under the receiver operating characteristic (ROC) curve for the ability of the APTT to detect ≥30% decreases in femoral SBP was 0.903 (95% confidential interval, 0.895-0.911). In addition, the APTT performed better than the cPTT and RR interval in the above analysis (all P < 0.05). Therefore, the APTT has acceptable accuracy in tracking beat-to-beat femoral SBP and could detect substantially decreased femoral SBP. These findings indicate that the APTT may be a promising noninvasive surrogate for invasive femoral SBP during VA. A multiparameter model combining APTT and other parameters is needed to further improve the accuracy.

Сравнение артериального давления на плечовом и бедренном участках

Вынужденное отсутствие возможности измерения артериального давления на плечевой артерии заставляет искать другие участки для получения значений при неинвазивном определении кровяного давления. Бедренный участок может расцениваться как такая альтернатива. Поэтому установление достоверности взаимосвязи значений артериального давления, измеренного на плечевом и бед-ренном участках, является перспективным направлением поисков. В данном исследовании измерение артериального давления на плечевом и бедренном участках было проведено на 100 соматически здоровых студентах в возрасте 21,0 ± 1,2 года в состоянии покоя, измерения осуществлялись с помощью монитора пациента «UM-300» (Украина) с применением двух стандартных манжеток для измерения давления на участке плеча (25–35 см) и на участке бедра (38–50 см), статистическая достоверность взаимосвязи данных была определена с помощью метода Бленда — Альтмана, а также были использованы элементы регрессионного анализа. Результаты исследования показали отсутствие существенного расхождения в данных, особенно если речь шла о среднем артериальном давлении. Также была разработана регрессионная модель, что может служить ценной информацией для алгоритмической разработки программ прогнозирования артериального давления на плечевой артерии при его измерении на бедренном участке. Таким образом, измерение артериального давления на бедренном участке можно считать альтернативой измерения артериального давления на участке плеча.

Correlation between radial and femoral arterial blood pressure during reperfusion in living donor liver transplantation.

Background and Aims:Accurate blood pressure measurements are the mainstay for the efficient management of abrupt cardiovascular changes during reperfusion in liver transplant. We sought to compare the femoral and radial pressures during reperfusion and at T1:baseline, T2: 1 h in dissection: T3:portosystemic shunt, T4:reperfusion, T5: at bile duct anastomosis.Methods:A retrospective study was performed amongst 102 adult patients who underwent R lobe living donor liver transplantation. Mean arterial pressure (MAP) and systolic arterial pressure (SAP) at 10 s intervals at reperfusion and at five fixed time points were compared by intraclass correlation coefficient (ICC) and limits of agreement by Bland–Altman statistics.Results:MAP by both routes had a good correlation at all time points during reperfusion (overall ICC: 0.946 [0.938, 0.949]) in comparison with SAP (overall ICC: 0.650 [0.6128, 0.684]). At the lowest reperfusion pressure (reperfusion point), MAP showed high levels of agreements (ICC: 0.833 [0.761, 0.885]), whereas SAP showed only a poor level of agreement (ICC 0.343 [0.153, 0.508]). The Bland–Altman analysis for MAP showed a bias of 7.18 (5.94) mmHg and limits of agreement of − 4.5 mmHg to + 18.8 mmHg and for SAP a bias of 25.2 (22.04) mmHg and limits of agreement of − 18.0 mmHg to + 68.4 mmHg at the reperfusion point. The incidence of post-reperfusion syndrome (PRS) was 52.94% by femoral and 57.84% by radial routes.Conclusions:Radial MAP correlated well with femoral MAP during reperfusion and at predefined time points and can be used interchangeably for intraoperative monitoring. A high incidence of PRS was noted by our technique of measurement.

599-P: Magnetic Field vs. Calcium Channel Blockade Effect on Microcirculation: Potential Implementation in Diabetic Foot Microvascular Dysfunction

The goal was to compare static magnetic field (SMF) vasodilator capacity with verapamil (VER) a potent Ca2+ channel blocking agent infusion, aimed to asses SMF potential implementation in conditions with vascular ischemia. Mean femoral artery blood pressure, heart rate and ear lobe skin microcirculatory blood flow measured by microphotoelectric plethysmogram (MPPG) were simultaneously recorded in conscious rabbits after 40-min carotid baroreceptor exposure to 0.35 T SMF (SMF-Car, n = 14) or 0.25 T SMF, generated by Nd-Fe-B magnets, exposed directly to ear microvascular net (SMF-Ves, n = 20), Fig. 1a, and compared with that after 30 min VER i.v. infusion (20 mg kg-1 min-1, n = 20), Fig. 1b. The principal finding is that SMF-Car, SMF-Ves and VER significantly increased microcirculation by: 22.6 ± 11.11%, 17.9 ± 9.58% and 30.5 ± 14.06% (mean ± SEM) resp. and that was no significant difference between all of three treatments (p = 0.986). Microvascular dilation was accompanied by significant decrease of baroreflex sensitivity in VER and its increase in SMF-Car coupled with enhanced vessel sensitivity to nitric oxide dilatory effect. This suggests SMF strong, comparable with VER vasodilator property tailored to address neural and myogenic component of microvascular dysfunction in diabetic foot and nephropathy especially employing both SMFs vasodilation synergy. Disclosure J. Gmitrov: None.

Dissociation of Cerebral Blood Flow and Femoral Artery Blood Pressure Pulsatility After Cardiac Arrest and Resuscitation in a Rodent Model: Implications for Neurological Recovery.

BackgroundImpaired neurological function affects 85% to 90% of cardiac arrest (CA) survivors. Pulsatile blood flow may play an important role in neurological recovery after CA. Cerebral blood flow (CBF) pulsatility immediately, during, and after CA and resuscitation has not been investigated. We characterized the effects of asphyxial CA on short‐term (<2 hours after CA) CBF and femoral arterial blood pressure (ABP) pulsatility and studied their relationship to cerebrovascular resistance (CVR) and short‐term neuroelectrical recovery.Methods and ResultsMale rats underwent asphyxial CA followed by cardiopulmonary resuscitation. A multimodal platform combining laser speckle imaging, ABP, and electroencephalography to monitor CBF, peripheral blood pressure, and brain electrophysiology, respectively, was used. CBF and ABP pulsatility and CVR were assessed during baseline, CA, and multiple time points after resuscitation. Neuroelectrical recovery, a surrogate for neurological outcome, was assessed using quantitative electroencephalography 90 minutes after resuscitation. We found that CBF pulsatility differs significantly from baseline at all experimental time points with sustained deficits during the 2 hours of postresuscitation monitoring, whereas ABP pulsatility was relatively unaffected. Alterations in CBF pulsatility were inversely correlated with changes in CVR, but ABP pulsatility had no association to CVR. Interestingly, despite small changes in ABP pulsatility, higher ABP pulsatility was associated with worse neuroelectrical recovery, whereas CBF pulsatility had no association.ConclusionsOur results reveal, for the first time, that CBF pulsatility and CVR are significantly altered in the short‐term postresuscitation period after CA. Nevertheless, higher ABP pulsatility appears to be inversely associated with neuroelectrical recovery, possibly caused by impaired cerebral autoregulation and/or more severe global cerebral ischemia.

Pulse-wave transit time with ventilator-induced variation for the prediction of fluid responsiveness.

AimAlthough pulse pressure variation is a good predictor of fluid responsiveness, its measurement is invasive. Therefore, a technically simple, non‐invasive method is needed for evaluating circulatory status to prevent fluid loading and optimize hemodynamic status. We focused in the pulse‐wave transit time (PWTT) defined as the time interval between electrocardiogram R wave to plethysmograph upstroke, which has been recently introduced to non‐invasively assess cardiovascular response. In the present study, we evaluated the efficacy of pulse‐wave transit time (PWTT) with ventilator‐induced variation (PWTTV) in predicting fluid responsiveness.MethodsWe evaluated six domestic pigs weighing 46.0 ± 3.5 kg. After anesthesia induction, electrocardiogram, femoral arterial blood pressure, plethysmograph on the tail, and carotid artery blood flow were monitored and hemorrhage was induced by withdrawing 20 mL/kg blood over 20 min; 5 mL/kg blood volume was then autotransfused over 10 min. Then PWTTV and pulse pressure variation were measured at tidal volumes of 6 and 12 mL/kg.ResultsArea under the receiver operating curve values for the prediction of a >10% change in carotid artery blood flow were 0.979 for pulse pressure variation and 0.993 for PWTTV at a tidal volume of 6 mL/kg and 0.979 and 0.979, respectively, at a tidal volume of 12 mL/kg (all P < 0.0001).ConclusionsMeasured non‐invasively, PWTTV showed similar utility to pulse pressure variation in predicting >10% changes in carotid artery blood flow induced by autotransfusion.

Experimental study in protecting lung with controlled lung collapse

Objective To investigate the protective effect of controlled lung collapse using a new type single-cavity lung isolation catheter ventilation tool in dogs undergoing thoracotomy. Methods Eighteen dogs were randomly divided into three groups (n=6). After induction of general anesthesia, all dogs were intubated with the controlled intrapulmonary balanced gas lung isolation catheter, and then two Swan-Ganz floating catheters were inserted into the femoral artery and the right internal jugular vein respectively for blood pressure monitoring and blood sample collection. After 20 min of two-lung ventilation (TLV), one-lung ventilation (OLV) was performed to collapse the right lung. The degree of collapse in the right lung in group A, B and C was respectively maintained at 100%, 90% and 50% by a microcapsule. Blood samples from the femoral artery and jugular vein were collected at the following time points: 1 min before OLV (T1), 30 min (T2), 60 min (T3) and 120 min (T4) after OLV. The intrapulmonary shunt rate (Qs/Qt) was determined by blood gas analysis, and serum levels of intercellular adhesion molecule 1 (ICAM-1), malondialdehyde (MDA) and superoxide (SOD) were analyzed by ELISA. HR, femoral arterial blood pressure (ABP), mean pulmonary arterial pressure (MPAP), PEtCO2, rectal temperature and other vital signs were continuously monitored during the whole procedure. Results All physiological indices did not differ in all groups during TLV (P>0.05). OLV significantly elevated Qs/Qt, reduced production of serum ICAM-1 and MDA, and increased serum SOD production in a time dependent manner among all groups. The dogs with 90% and 50% lung collapse showed reduced MPAP, lower serum ICAM-1 and MDA, higher SOD production and lower Qs/Qt as compared to dogs with complete one lung collapse. Furthermore, when compared with 90% lung collapse, 50% lung collapse induced better lung protection as indicated by lower production of serum ICAM-1 and MDA and higher serum SOD production. Conclusions Controlled one lung collapse has beneficial effect on acute lung injury by minimizing inflammatory responses and attenuating impairment of lung function. Especially, 50% one lung collapse has better lung protective effect than 90% collapse. Key words: One-lung ventilation; Controlled lung collapse; Lung protection; Dogs

Sudden death in response to severe acute hypoxemia under urethane anesthesia is caused by catastrophic failure of respiratory control

Respiratory autoresuscitation is normally a robust process that restores eupneic breathing rhythm following severe hypoxemia‐induced respiratory arrest. We previously found that urethane anesthesia prevents autoresustitation and causes predictable cardiorespiratory collapse and sudden death as a result of even a single episode of severe hypoxemia [Krause et al (2016); Respir Physiol Neurobiol. 232:43–53]. It is unknown whether this failure to autoresuscitate is due to a respiratory or cardiovascular deficit. We hypothesized that sudden death in this condition is primarily related to a respiratory deficit, and that intervention with mechanical ventilation (MV) would promote restoration of eupnea. To test this hypothesis we studied 40 urethane‐anesthetized adult male rats that were surgically instrumented to measure tracheal airflow and femoral artery blood pressure during severe hypoxic challenge. Animals were randomly assigned to one of 4 experimental groups (n=10 for each group). Following baseline measurements, animals were subjected to an episode of acute severe hypoxia via breathing 100% N2, and received MV at one of the following time points following respiratory arrest: (1) 70 sec, (2) 90 sec, (3) 110 sec. The ventilator was set to provide room air breaths at 10/min with a 10% inspiratory duty cycle and a volume of 6.6 mL/kg body weight. A fourth group received no intervention but was given access to room air following respiratory arrest. One‐way ANOVA testing and relative risk analyses were performed to compare cardiorespiratory variables and probability of sudden death between groups (a set a prior at 0.05). All animal groups were similar with respect to animal weight, and baseline cardiorespiratory parameters while breathing room air. The ten animals in the control group that did not receive intervention with MV all experienced sudden death in response to acute severe hypoxemia. Only 1/10 of these animals even attempted to gasp. In contrast, MV following respiratory arrest was effective in restoring rhythmic spontaneous breathing and preventing sudden death (p&lt;0.001 for all groups combined vs. control). MV at 70, 90, and 110 sec post‐respiratory arrest rescued 9/10 (p&lt;0.001), 5/10 (p&lt;0.033), and 6/10 (p&lt;0.011) animals respectively, allowing these animals to restore eupneic breathing and recover cardiorespiratory parameters. These results demonstrate that under urethane anesthesia the cardiovascular system is fully capable of distributing oxygen to the brainstem, and that eupneic breathing can be restored provided that sufficient lung ventilations occur post‐respiratory arrest. We interpret these findings to suggest that urethane anesthesia impairs the normal process of triggering gasping rhythm in vivo, supporting our study hypothesis that sudden death in this model is due to a profound respiratory deficit. Urethane anesthesia therefore provides a reliable and reproducible in vivo model of sudden death in response to acute severe hypoxemia, caused by catastrophic failure of respiratory control.Support or Funding InformationAAS was the recipient of a CMU College of Medicine Summer Research Scholars Award. These experiments were funded through an Early Career Award received by HB from the Office of Research and Sponsored Programs at Central Michigan University.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Loss of function RGS2 mutations augment vascular contractility ex vivo

ObjectiveRegulator of G protein signaling 2 (RGS2) plays a significant role in alleviating vascular contraction and promoting vascular relaxation due to its GTPase accelerating protein activity toward Gαq. Through a cell‐based Ca2+ mobilization assay, we identified 4 loss‐of‐function (LOF) mutations (Q2L, D40Y, R44H and R188H) out of 16 rare, missense mutations in RGS2 selected from various human exome sequencing projects. This study is to investigate whether these LOF RGS2 mutations disrupt the protein function in regulating vascular contractility.Approach and resultWe confirmed that RGS2‐deficient mice expressed a hypertensive phenotype by telemetric femoral artery blood pressure measurement in conscious mice (WT SBP 120 ± 3 vs RGS2−/−SBP 128 ± 2 mmHg, p&lt;0.01). Isolated mesenteric arteries from RGS2−/− mice showed higher contractile response to 10 nM angiotensin II (AngII) stimulation in pressure myograph while isolated aortic rings from those animals generated more tension upon phenylephrine (PE) stimulation (Emax 238 mg vs 68 mg, p = 0.01) compared to aortic rings from RGS2+/+ mice. Reintroduction of wild‐type RGS2‐GFP plasmids into RGS2−/− mesenteric arteries by reversible permeabilization suppressed the vasoconstrictor response to 50 nM AngII (RGS2 WT plasmid −4% vs pcDNA control −35% of basal diameter, p = 0.01). Transfection with RGS2 LOF mutation plasmidss did not suppress Ang II constriction compared to those expressing WT‐RGS2 (Q2L −20%, D40Y, R44H and R188H −30% of basal diameter, p &lt; 0.05).ConclusionsThis study is the first to investigate the function of human mutant RGS2 in resistance arteries in a near physiological condition. It demonstrates that RGS2 attenuates vasoconstriction in the mesenteric arteries and that RGS2 mutations disrupt this effect. Although these mutations are rare, knowledge about their function may provide insights into pathophysiology and treatment.Support or Funding InformationThis work was supported by the American Heart Association predoctoral fellowship [15PRE24680004] to H.P).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Differences in perioperative femoral and radial arterial blood pressure in neonates and infants undergoing cardiac surgery requiring cardiopulmonary bypass

ObjectiveSeveral reports claim that blood pressure (BP) in the radial artery may underestimate the accurate BP in critically ill patients. Here, the authors evaluated differences in mean blood pressure (MBP) between the radial and femoral artery during pediatric cardiac surgery to determine the effectiveness of femoral arterial BP monitoring. MethodThe medical records of children under 1 year of age who underwent open‐heart surgery between 2007 and 2013 were retrospectively reviewed. Radial and femoral BP were measured simultaneously, and the differences between these values were analyzed at various times: after catheter insertion, after the initiation of cardiopulmonary bypass (CPB‐on), after aortic cross clamping (ACC), after the release of ACC, after weaning from CPB, at arrival in the intensive care unit (ICU), and every 6h during the first day in the ICU. ResultsA total of 121 patients who underwent open‐heart surgery met the inclusion criteria. During the intraoperative period, from the beginning to the end of CPB, radial MBPs were significantly lower than femoral MBPs at each time‐point measured (p<0.05). Multivariate analysis showed that longer CPB time (>60min, odds ratio: 7.47) was a risk factor for lower radial pressure. However, discrepancies between these two values disappeared after arrival in the ICU. There was no incidence of ischemic complications associated with the catheterization of both arteries. ConclusionThe authors suggest that femoral arterial pressure monitoring can be safely performed, even in neonates, and provides more accurate BP values during CPB‐on periods, and immediately after weaning from CPB, especially when CPB time was greater than 60min.

CRRT in critically Ill children: Clinical profile from a tertiary care hospital in South India

Background : Continuous renal replacement therapy (CRRT) is a valuable tool in a pediatric intensive care unit (PICU), however the literature available from developing countries is scarce. Methods : Retrospective analysis of children who underwent CRRT during the past 1 year (June 2016 to May 2017). 24 sessions of CRRT was performed in 22 patients using Prismaflex® Baxter. Serum levels of urea, creatinine, and liver function tests were done in all patients. Activated clotting time (ACT) was monitored in all patients every 1 hourly till target ACT was achieved (180 – 220 seconds), thereafter every 4 hourly if the ACT continues in the target range. Unfractionated heparin was used for anticoagulation. Blood priming was done in patients with hematocrit less than 30% or in infants weighing less than 10 kg. Hemodialysis catheter (8.5Fr) was used in all patients, placed in the right internal jugular vein (IJV) under ultrasound guidance. Transthoracic echocardiography was used in all patients to confirm the position of the catheter tip within the right atrium. Central venous access in the femoral vein and arterial blood pressure monitoring was done in all patients as per unit protocol. Primary outcome measure was death during the procedure. Data collected were part of PRBC transfusion in pediatric ICU study and fluid balance study at JIPMER. Results : The median age of patients was 2 years (1 to 6 IQR). Mean bodyweight was 13.4 kg, 6.6 SD. Continuous venovenous hemofiltration (CVVH) was done in 5 patients (22.7%) and 17 patients (67.3%) were started on continuous venovenous hemodiafiltration (CVVHDF). Mortality during the procedure among the patients who underwent CRRT was 50% (n=11). Mean PRISM III score was 14. Out of 22 patients, 15 patients (68.7%) were on vasoactive medications at the time of initiation of CRRT. Median fluid overload (FO%) was 0.62 (0.45 to 1.62 IQR). Average time to start CRRT since PICU admission was 55 hours. The common indications were acute kidney injury with fluid overload (n=9), acute liver failure with hyperammonemia (n=3), organic acidemia with severe high anion gap acidosis (n=1), unknown poisoning with high anion gap acidosis (n=2), pigment nephropathy following wasp sting (n=1) and electrocution (n=1). CRRT along with venovenous extra corporeal membrane oxygenation (vv ECMO) (n=1) was done in a case of hemophagolymphohistiocytosis syndrome with ARDS. Effluent dose 35ml/kg/hour in all patients except in 2 cases of acute liver failure where the effluent dose was increased up to 42ml/kg/hour due to persistent hyperammonemia. CRRT with plasma exchange using P2 plasma filter was done with CRRT circuit modification in 2 cases of thrombocytopenia associated multiorgan failure (TAMOF). Mean duration of CRRT was (55 hours, SD 23.8). Maximum circuit life with systemic heparin as anticoagulant was 92 hours. Filter clotting and new circuit requirement was encountered in 6 patients (27.7%). Conclusion : CRRT can be used safely in critically ill children. The circuit life can be prolonged with serial ACT monitoring and titration of anticoagulation.

Differences in perioperative femoral and radial arterial blood pressure in neonates and infants undergoing cardiac surgery requiring cardiopulmonary bypass

ObjectiveSeveral reports claim that blood pressure (BP) in the radial artery may underestimate the accurate BP in critically ill patients. Here, the authors evaluated differences in mean blood pressure (MBP) between the radial and femoral artery during pediatric cardiac surgery to determine the effectiveness of femoral arterial BP monitoring. MethodThe medical records of children under 1 year of age who underwent open-heart surgery between 2007 and 2013 were retrospectively reviewed. Radial and femoral BP were measured simultaneously, and the differences between these values were analyzed at various times: after catheter insertion, after the initiation of cardiopulmonary bypass (CPB-on), after aortic cross clamping (ACC), after the release of ACC, after weaning from CPB, at arrival in the intensive care unit (ICU), and every 6h during the first day in the ICU. ResultsA total of 121 patients who underwent open-heart surgery met the inclusion criteria. During the intraoperative period, from the beginning to the end of CPB, radial MBPs were significantly lower than femoral MBPs at each time-point measured (p<0.05). Multivariate analysis showed that longer CPB time (>60min, odds ratio: 7.47) was a risk factor for lower radial pressure. However, discrepancies between these two values disappeared after arrival in the ICU. There was no incidence of ischemic complications associated with the catheterization of both arteries. ConclusionThe authors suggest that femoral arterial pressure monitoring can be safely performed, even in neonates, and provides more accurate BP values during CPB-on periods, and immediately after weaning from CPB, especially when CPB time was greater than 60min.

EFFECT OF OXACOM ON THE RIGHT VENTRICULAR PRESSURE IN RATS WITH MONOСROTALIN-INDUCED PULMONARY ARTERIAL HYPERTENSION

Background. Pulmonary arterial hypertension (PAH) is a relatively rare disease, but its therapy is expensive and effectiveness is moderate. One of important mechanisms of PAH pathogenesis is reduced formation of nitric oxide in pulmonary vascular endotheliocytes. Objective . To study the effect of oxacom (dinitrosyle iron complex with ligand glutathione), which already demonstrated long-term decline in blood pressure (BP) in systemic circulation, on pressure in pulmonary circulation. Design and method . To induce PAH, the standard monocrotalin rat model was used. Three weeks after monocrotalin introduction (60 mg/kg), a catheterization of the right ventricle was performed in anesthetized rats (100 mg/kg ketamine) through jugular vein and pressure was measured. Simultaneously, BP in femoral artery and ECG were recorded. Results . Systolic pressure in the right ventricle (SPRV) in rats after monocrotalin introduction doubled compared with the control group, from 35 to 70 mmHg, but myocardial contractility index fell by 28 %, also duration of QRS complex and the height of T-wave increased. Intravenous oxacom (40 mg/kg) quickly reduced SPRV by average of 12 ± 3 mmHg, and this level was maintained for an hour. This effect was absent in control rats. Similar BP changes in systemic circulation were observed in both groups. Inhalation of nitric oxide led to BP decrease only in animals with high level of SPRV. Inhalation of oxacom was ineffective. Conclusion . Oxacom is a promising substance for sustained pressure decline in the pulmonary circulation in PAH, but further investigations are needed for the development of a more suitable prolonged-action form of the drug.

The agreement between oscillometric and intra-arterial technique for blood pressure monitoring in the lower extremities for infants and toddlers undergoing aortic coarctation repair.

Anesthetic management for patients undergoing surgical repair of aortic coarctation (CoA) should include constant blood pressure monitoring of the right upper extremity and a lower extremity. The delayed or absent pulse in the lower limbs often leads to unsuccessful arterial cannulation in infants and the oscillometric technique used for blood pressure measurement. The aim of this study was to evaluate the agreement between the oscillometric method and intra-arterial technique for blood pressure monitoring in the lower limbs of infants undergoing CoA. A total of 45 infants diagnosed with isolated CoA were initially enrolled in this study and five were excluded because of cannulation failure. Thus, 40 patients had their blood pressure measured simultaneously by both oscillometric technique on the thigh and femoral artery catheterization. After induction and intubation, five pairs of blood pressure readings from each patient were collected in an interval of 3 min. Statistical analysis was accomplished by revised Bland-Altman analysis. There was a strong correlation between oscillometric and invasive blood pressure measurements [systolic blood pressure (SBP) r = 0.771, diastolic blood pressure (DBP) r = 0.704 and mean artery pressure (MAP) r = 0.850]. The mean difference and 95% limits of agreement (95% LOA) between oscillometric and femoral artery blood pressure readings was 3.830 mmHg (-19.297, 26.957) for SBP, -8.725 mmHg (-26.236, 8.786) for DBP, and -3.235 mmHg (-18.842, 12.372) for MAP. There were only one pair of MAP (1/40) and two pairs of SBP readings (2/40) out of range (95% LOA), and all of paired DBP readings were within 95% LOA. There was a good agreement between oscillometric and invasive blood pressure measurements of lower extremities in infants with isolated CoA statistically. However, the oscillometry-measured SBP showed a tendency to overestimate the intra-arterial blood pressure reference, while oscillometry-measured DBP underestimated its reference. MAP measurement provided the most accurate and reliable results in this study.

Dynamics of Cardio‐Respiratory Coupling During Sighs in Conscious Rats

IntroductionProduction of sighs is an inherent property of medullary respiratory rhythm generating regions. Sighing is accompanied by a brief period of tachycardia (Ramirez, 2014, Prog Brain Res, 209, 91). In our recent study (under review) we simultaneously recorded blood pressure in femoral artery (telemetry) and respiration (plethysmography) in rats given saline or diazepam pre‐treatment during acclimatization and restraint stress. The incidence of sighs was increased during restraint, but was unaffected by diazepam.MethodsIn the current study we reanalyzed data from 4 conscious freely moving rats after saline and after diazepam pre‐treatments to determine the dynamics of cardio‐respiratory coupling during sighs. We averaged 6‐second windows of heart rate (HR) and arterial blood pressure (AP) signals during production of sighs (# of sighs during acclimatization after saline = 133; acclimatization/diazepam = 145; restraint/saline = 60; restraint/diazepam = 48).ResultsA normal sigh consists of four distinct phases – initial inspiration, augmented inspiration, expiration and apneic pause of variable duration (average duration in our sample = 1.3s; range: 0.3 to 2.4s). We observed an increase in HR during initial inspiration, followed by brief bradycardia during augmented inspiration, and tachycardia during expiration and apneic pause (see supplementary figure). AP decreased during inspiration and augmented inspiration, but then rapidly increased during expiration. After that we observed a prolonged tri‐phasic baroreflex response spanning over 5 seconds (depressor‐pressor‐depressor) until AP equalized. Pre‐treatment with diazepam inhibited tachycardia during expiration and apneic pause, but preserved the AP response. Sighs exhibited during restraint stress (on both diazepam and saline trials) were accompanied by more pronounced HR and AP responses than during acclimatization.ConclusionsWe have two novel findings: (1) a brief period of bradycardia during augmented inspiration and (2) baroreceptor reflex following sighing. The bradycardia is likely due to respiratory sinus arrhythmia‐like vagal activation following termination of normal inspiration. Decrease in AP often preceded commencement of augmented inspiration presumably due to vasodilation of skeletal muscles as reported by Marshall and Metcalfe (1988, JPhysiol, 400, 15). However, unlike their study, we observed a very rapid pressor response during sigh expiration followed by a prolonged tri‐phasic baroreceptor reflex. This response was virtually unaffected by diazepam pre‐treatment, which induced vagal withdrawal, tachycardia and inhibited any tachycardic responses to sighs. One of the possible explanations for the AP response is that arterial stretch receptors are being activated by rapid contraction of the diaphragm during expiration in conscious animals. Presumably, sigh duration is shorter in conscious animals, thus contraction of the diaphragm is more rapid than under anesthesia and can cause stretch receptor activation unlike anesthetized animals, where hyperinflation or subsequent deflation of lungs do not induce any cardiovascular changes (Marshall &amp; Metcalfe, 1988). In line with this, HR and AP responses were more pronounced during restraint, when respiratory rate is faster and sigh duration is even shorter than during acclimatization. This prolonged baroreflex is likely to be one of physiological functions of sighs to maintain proper gas exchange.Support or Funding InformationThis study was supported by the Hunter Medical Research Institute and the National Heart Foundation of Australia.

Feasibility of Intraprocedural Transluminal Hepatic and Femoral Artery Blood Pressure Measurements as an Alternative Embolization Safety Endpoint When Antireflux Devices Are Used During Lobar Chemoembolization.

The purpose of this study was to describe the technique for evaluating hepatic arterial blood pressure changes during lobar chemoembolization using antireflux devices. Intraprocedural femoral and hepatic arterial blood pressures were measured and chemoembolization terminated when significant reduction in the difference occurred. Liver toxicity was evaluated. Eleven patients underwent 24 lobar chemoembolization procedures. Early termination of delivery occurred in 11 of 24 (46%) procedures in which the mean relative reduction in systemic-hepatic arterial pressure differential was 48%. The mean liver toxicity score was 1.2. This compares to delivery of the entire dose in 13 of 24 (54%) procedures in which the mean relative reduction in systemic-hepatic arterial pressure differential was 12% with a mean liver toxicity score of 1.2. When antireflux devices are used, intraprocedural assessment of hepatic artery blood pressure changes may be a useful embolization safety endpoint.