Intra-arterial Pressure Research Articles

Orthostatic Hypertension

See related article, pp 167–173 Orthostatic hypertension (OHT) is beneath the radar of many health care professionals. In the clinic, it is generally both unexpected and counterintuitive. After recheck, it may sometimes regress toward the mean. However, at other times the OHT can be dramatic and persistent. Nevertheless, our knowledge about its causes and significance remains circumscribed. It is in many ways the last hemodynamic frontier. Recently, there has been increasing interest in OHT and its possible consequences on health. The spectrum of degree and clinical context of OHT is very broad.1 In some cases, it can be a dramatic physical manifestation of 50 mm Hg or more in a disorder such as baroreflex failure. In other situations, it may only be an incidental physical finding. OHT is usually defined as an increase in blood pressure with upright posture or tilt, but precise criteria have not been established. Furthermore, few studies have entailed direct measurement of blood pressure in people with OHT. Such measurements would more faithfully reflect intraarterial pressure and would avoid the introduction of potential artifacts. Sphygmomanometers can underestimate blood pressure when it is perturbed by pressor reflexes, such as those engaged by upright posture, or if it is increased by pressor agents. Therefore, the magnitude of the blood pressure increase after standing might be even larger than is generally reported in patients with OHT. OHT has been long recognized. Some of the most thoughtful early studies were conducted by David Streeten …

Can exercise prevent preeclampsia?

Can exercise prevent preeclampsia?

Continuous non-invasive finger arterial pressure monitoring reflects intra-arterial pressure changes in children undergoing cardiac surgery

BackgroundContinuous non-invasive measurement of finger arterial pressure (FAP) is a reliable technology in adults. FAP is measured with an inflatable cuff around the finger and simultaneously converted to a reconstructed brachial artery pressure waveform (reBAP) by the Nexfin™ device. We assessed the adequacy of a prototype device (Nexfin-paediatric), designed for a paediatric population, for detecting rapid arterial pressure changes in children during cardiac surgery. MethodsThirteen anaesthetized children with a median age of 11 months (2 months–7 yr) undergoing congenital cardiac surgery were included in the study. reBAP and intra-arterial pressure (IAP) were recorded simultaneously during the surgical procedure. To assess the accuracy of reBAP in tracking arterial pressure changes, the four largest IAP variations within a 5 min time interval were identified from each procedure. These variations were compared offline with reBAP during a 10 s control period before and a 10 s period after an arterial pressure change had occurred. ResultsIn 10 out of 13 children, a non-invasive arterial pressure recording could be obtained. Therefore, recordings from these 10 children were eligible for further analysis, resulting in 40 data points. The correlation coefficient between reBAP and IAP in tracking mean arterial pressure (MAP) changes was 0.98. reBAP followed changes in IAP with a mean bias for systolic, diastolic arterial pressure, and MAP of 0.0 mm Hg (sd 5.8), 0.1 (sd 2.8), and 0.19 (sd 2.7), respectively. ConclusionsThe prototype device closely follows arterial pressure changes in children. However, in a considerable number of attempts, obtaining a signal was time-consuming or unsuccessful. This technique seems promising but requires further technical development.

Metoprolol, but not atenolol, reduces stress induced neuropeptide Y release in pigs

Objectives. To explore if β-adrenergic receptors in the brain are involved in acute and delayed cardiovascular responses to a brief emotional stress, by comparing the effects of the β1-blockers metoprolol (lipophilic) and atenolol (hydrophilic). Design. Male dominant pigs, singleliving, freely moving, with telemetric recordings of intra-arterial pressure and ECG and assay of plasma levels of the adrenergic cotransmittor neuropeptide Y (NPY), were confronted with four alien pigs for three minutes at weekly intervals. Weeks 1 and 4 were controls, in weeks 2 and 3 randomized crossover treatment with metoprolol or atenolol were given. Results. The confrontation caused instant and transient tachycardia and more prolonged effects in terms of increased plasma NPY levels, increased arterial pressure and reduced cardiac vagal activation. The two β-blockers inhibited the tachycardia equally, but only metoprolol reduced the prolonged effects. Conclusions. Emotionally induced sympathetic activation involves peripheral release of NPY causing a prolonged increase of arterial pressure and a reduction of cardiac vagal activity. These effects are prevented by central nervous β-adrenoceptor blockade.

Pulse contour cardiac output derived from non‐invasive arterial pressure in cardiovascular disease

Pulse contour methods determine cardiac output semi-invasively using standard arterial access. This study assessed whether cardiac output can be determined non-invasively by replacing the intra-arterial pressure input with a non-invasive finger arterial pressure input in two methods, Nexfin CO-trek and Modelflow , in 25 awake patients after coronary artery bypass surgery. Pulmonary artery thermodilution cardiac output served as a reference. In the supine position, the mean (SD) differences between thermodilution cardiac output and Nexfin CO-trek were 0.22 (0.77) and 0.44 (0.81) l.min(-1) , for intra-arterial and non-invasive pressures, respectively. For Modelflow, these differences were 0.70 (1.08) and 1.80 (1.59) l.min(-1) , respectively. Similarly, in the sitting position, differences between thermodilution cardiac output and Nexfin CO-trek were 0.16 (0.78) and 0.34 (0.83), for intra-arterial and non-invasive arterial pressure, respectively. For Modelflow, these differences were 0.58 (1.11) and 1.52 (1.54) l.min(-1) , respectively. Thus, Nexfin CO-trek readings were not different from thermodilution cardiac output, for both invasive and non-invasive inputs. However, Modelflow readings differed greatly from thermodilution when using non-invasive arterial pressure input.

Renal Actions of RGS2 Control Blood Pressure

G protein-coupled receptors (GPCRs) have key roles in cardiovascular regulation and are important targets for the treatment of hypertension. GTPase-activating proteins, such as RGS2, modulate downstream signaling by GPCRs. RGS2 displays regulatory selectivity for the Gαq subclass of G proteins, and mice lacking RGS2 develop hypertension through incompletely understood mechanisms. Using total body RGS2-deficient mice, we used a kidney crosstransplantation strategy to examine separately the contributions of RGS2 actions in the kidney from those in extrarenal tissues with regard to BP regulation. Loss of renal RGS2 was sufficient to cause hypertension, whereas the absence of RGS2 from all extrarenal tissues including the peripheral vasculature did not significantly alter BP. Accordingly, these results suggest that RGS2 acts within the kidney to modulate BP and prevent hypertension. These data support a critical role for the renal epithelium and/or vasculature as the final determinants of the intra-arterial pressure in hypertension.

Arterial Pressure Gradient of Upper Extremity Arteriovenous Access Steal Syndrome: Treatment Implications

Treatment options after arteriovenous fistula (AVF) associated steal include ligation, banding, and distal revascularization-interval ligation (DRIL). The purpose of this study was to evaluate the arterial pressure gradients in upper extremity steal syndrome. Preoperative arteriography and sequential intra-arterial pressure readings were performed on consecutive AVF patients with hand ischemia. Analysis of variance (ANOVA) with repeated measures analyzed intersubject comparisons, and post hoc analysis identified anatomic locations with highest inflow pressures. Nine patients presented with ischemic hand symptoms after AVF. Pullback arterial pressure measurements revealed gradual increases in systolic and mean pressures as the catheter position was moved proximally from the AVF anastomosis. Post hoc analysis after ANOVA revealed higher axillary artery systolic pressure compared to proximal brachial artery (153 vs 116.8, P = .007). AVF-related steal syndrome decreases arterial inflow pressure of the affected extremity more proximally than previously thought. When performing a DRIL procedure, consideration should be given to placing the anastomosis as proximally as possible.

The Mean Prehospital Machine; accurate prehospital non-invasive blood pressure measurement in the critically ill patient

Non-invasive blood pressure recordings may be inaccurate in the critically ill patient and measurement difficulties are intensified in the prehospital setting. This may adversely impact upon outcomes for many critically ill patients, particularly those with traumatic brain injury and/or lengthy prehospital times. This study aimed to validate a non-invasive, oscillometric, ambulatory blood pressure measuring device, the Oscar 2, Model 222 (SunTech Medical, Morrisville, USA) during the ambulance transport of critically ill patients. We have previously shown that mean arterial blood pressures observed by Intensive Care Unit nurses from a patient monitor can be considered interchangeable with reference intra-arterial integrated mean pressures. In the current study, we compared non-invasive device mean pressures to intra-arterial pressures observed by retrieval nurses from the patient monitor, during the ambulance transportation of critically ill patients. Device performance was required to fulfil the Association for the Advancement of Medical Instrumentation (AAMI) protocol requirements. Additionally, linear mixed effects analyses and Bland-Altman comparisons were undertaken. For 157 measurements recorded from 23 patients, when the Oscar 2 did not indicate a measurement was associated with a fault, the device fulfilled the AAMI protocol requirements, with a mean error of -1.1 mmHg (standard deviation 7.8 mmHg), 95% confidence intervals (linear mixed effects analysis) -2.9, 0.8; P = 0.26. Bland-Altman plots indicated uniform agreement across a wide range of blood pressures. Sixteen percent of recordings were associated with a patient, environment, or device generated fault. When the Oscar 2 does not indicate a fault has occurred, clinicians may be confident the mean pressure, within acceptable limits, is accurate, even during ambulance motion, administration of high doses of vasopressors and mechanical ventilation. The Oscar 2 appears to be an accurate and rugged out-of-hospital device.

Non‐invasive monitoring

For a number of reasons, invasive and non-invasive measuring procedures for monitoring purposes must not be considered to be mutually exclusive alternatives. The transitions between the two are fluid, and their respective advantages and disadvantages frequently complement one another. The complication rate characteristic of a given procedure is the greater, the more invasive this procedure is. For this reason, a non-invasive technique should always be given preference over an invasive method provided it is capable of recording the parameter to be monitored at least as reliably and accurately as the latter. For minimal monitoring during anaesthesia, non-invasive procedures are applied exclusively. These include the monitoring of ventilation (FIO2, pressures, volumes, flows), ECG, measurement of blood pressure employing the cuff method, temperature measurement, and a nerve stimulator for establishing the degree of relaxation. In addition, pulse oximetry and capnography are increasingly becoming accepted elements of basic monitoring. The question as to whether further monitoring procedures need to be employed will depend upon the condition of the patient and the nature and duration of the surgical operation and anaesthesia. Here, preferential use is made of invasive methods of recording pressures and flows (cardiac output) within the circulatory system and of various blood parameters (for example, blood gas analysis). To an increasing extent, they are being supplemented, expanded or replaced by newly developed non-invasive methods. Thus, for example, the time and material requirement for non-invasive blood pressure measurement in the finger by means of servomanometry (Finapres) is reduced as compared with intra-arterial pressure recording.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac imaging and safety evaluation of BMS747158, a novel PET myocardial perfusion imaging agent, in chronic myocardial compromised rabbits

BackgroundBMS747158 labeled with 18F is being developed for PET myocardial perfusion imaging. Imaging studies showed clear detection of necrotic tissue in acute myocardial infarcted (MI) animals and a good safety profile in normal animals. This study evaluated BMS747158 imaging and cardiovascular safety in a rabbit model of chronic MI with cardiac compromise. Methods and ResultsChronic MI rabbits were developed by the left coronary artery ligation followed by 4 weeks recovery. Cardiac PET imaging with BMS747158 (~1.5 mCi, iv) in control rabbits showed clear and uniform myocardial uptake. However, imaging in chronic MI rabbits demonstrated obvious defect area in the left ventricular wall. Before BMS747158 injection, baseline electrocardiogram (ECG) waveforms in lead II configuration were normal with positive QRS complexes in control rabbits. In contrast, MI rabbits exhibited negative QRS complexes with enlarged Q waves and inverted T waves. Baseline values of mean intra-arterial pressure (AP, 61 ± 6 vs 89 ± 11 mmHg), systolic AP (79 ± 11 vs 114 ± 11 mmHg) and diastolic AP (53 ± 4 vs 76 ± 10 mmHg) were lower in MI than in control rabbits. Heart rate (162 ± 36 vs 159 ± 8 beat/minute) and QTc interval (corrected by Fridericia method, 288 ± 17 vs 319 ± 17 ms) were comparable. BMS747158 administration induced no changes from baseline in any of the measured cardiovascular parameters and ECG waveforms in either control or MI rabbits. ConclusionsCardiac imaging with BMS747158 allows clear detection of chronic MI without producing any cardiovascular alterations in cardiac compromised rabbits.

Validation of arterial blood pressures observed from the patient monitor; a tool for prehospital research

For some time, the inaccuracies of non-invasive blood pressure measurement in critically ill patients have been recognised. Measurement difficulties can occur even in optimal conditions, but in prehospital transportation vehicles, problems are exacerbated. Intra-arterial pressures must be used as the reference against which to compare the performance of non-invasive methods in the critically ill patient population. Intra-arterial manometer data observed from the patient monitor has frequently been used as the reference against which to assess the accuracy of noninvasive devices in the emergency setting. To test this method's validity, this study aimed to determine whether numerical monitor pressures can be considered interchangeable with independently sampled intra-arterial pressures. Intensive Care Unit nurses were asked to document arterial systolic, diastolic and mean pressures numerically displayed on the patient monitor. Observed pressures were compared to reference intra-arterial pressures independently recorded to a computer following analogue to digital conversion. Differences between observed and recorded pressures were evaluated using the Association for the Advancement of Medical Instrumentation (AAMI) protocol. Additionally, two-level linear mixed effects analyses and Bland-Altman comparisons were undertaken. Systolic, diastolic and integrated mean pressures observed during 60 data collection sessions (n = 600) fulfilled AAMI protocol criteria. Integrated mean pressures were the most robust. For these pressures, mean error (reference minus observed) was 0.5 mm Hg (SD 1.4 mm Hg); 95% CI (two-level linear mixed effects analysis) 0.4-0.6 mm Hg; P < 0.001. Bland-Altman plots demonstrated tight 95% limits of agreement (-2.3 to 3.2 mm Hg), and uniform agreement across the range of mean blood pressures. Integrated mean arterial pressures observed from a well maintained patient monitor can be considered interchangeable with independently sampled intra-arterial pressures and may be confidently used as the reference against which to test the accuracy of non-invasive blood pressure measuring methods in the prehospital or emergency setting.

The intrauterine to intra-arterial pressure ratio: a new parameter for the study of uterine contractility physiology

The objective of the study was to examine the uterine contractions and the arterial perfusion pressure changes after application of oxytocin, endothelin 1, prostaglandins PGE(1), PGE(2) and PGF(2alpha), in order to identify the substance with the greatest intrauterine pressure (IUP)/intra-arterial pressure (IAP) ratio, which means the substance most suitable for inducing uterine contractility without raising the systemic vascular pressure. Increasing doses of oxytocin, endothelin 1, PGE(1), PGE(2) and PGF(2alpha) were applied as bolus injection through the uterine artery of perfused swine uteri and the intrauterine and intra-arterial pressure rises were recorded. All substances showed a significant cervicofundic pressure gradient and, with the exception of PGF(2alpha), the uterine peristalsis moved towards the cervix uteri. The perfusion pressure after application of oxytocin, PGE(1), PGE(2) and PGF(2alpha) reached a maximum value and started to decrease, whereas endothelin 1 caused a continuous increase in the perfusion pressure. Endothelin 1 showed the lowest IUP/IAP ratio and oxytocin the greatest. In conclusion, the IUP/IAP ratio provides a promising new parameter for the study of uterine contractility physiology. Besides oxytocin, PGE(2) and PGF(2alpha) emerged as the best candidate substances to improve uterine contractility without raising the intra-arterial pressure.

The Mean Machine; Accurate Non-invasive Blood Pressure Measurement in the Critically Ill Patient

Accurate indirect prehospital blood pressure measurement in the critically ill patient remains an important challenge to both patient management and prehospital research. Ambulatory blood pressure measuring devices have not been trialled for prehospital use in critically ill patients. Prior to prehospital validation where conditions are suboptimal, we aimed to test under favourable conditions in the Intensive Care Unit, a selection of ambulatory devices that may be suitable for use in the field. Systolic, diastolic and mean pressures of three ambulatory devices were compared to the average of 1 min of independently recorded, high fidelity intra-arterial reference pressures. Eighteen critically ill patients were recruited. Device performance was required to fulfil the Association for the Advancement of Medical Instrumentation (AAMI) protocol. Additionally, agreement between measurement methods was examined using Bland-Altman plots. Two-level linear mixed model analyses were under- taken. For each device, 150 paired measurements (arterial reference and device) were analysed. According to the AAMI protocol, no device measured systolic pressures accurately. One device measured diastolic pressures accurately. Integrated mean pressures were accurately measured by all devices. Overall, SunTech Medical's Oscar 2 performed best with mean pressure error not exceeding 17 mmHg. For this device, Bland-Altman plots showed uniform agreement across a wide range of mean pressures. Two-level linear mixed effects analyses showed that Oscar 2 mean error reduced during vasopressor use by (-) 3.9 mmHg (95% CI -5.9, -1.9; P < 0.001), and clinically, performance was little affected during mechanical ventilation. For the Oscar 2, there was up to (-) 7.0 mmHg (95% CI -10.3, -3.5; P < 0.001) l ess mean error during hypotension compared to normo- tension. In the Intensive Care Unit, the performance of one device, the Oscar 2, surpassed the others and fulfilled the AAMI protocol criteria for mean pressure measurement. This device is suitable for prehospital validation.

Hypertonie bei Patienten mit Nierenarterienstenosen

Renal artery stenosis (RAS) is often present in patients with severe hypertension and atherosclerotic vascular disease. In this setting it is important to screen patients for renovascular disease, e.g. with Duplex-ultrasound, CT- or MR-angiography. The challenge of treating these patients is to find the evidence proving that the RAS is responsible for hypertension and/or renal dysfunction. Measurement of the intra-arterial pressure gradient is necessary in order to determine hemodynamic relevance. On the other side, in these patients hypertension is often of primary and/or renoparenchymatous origin and is aggravated by a renovascular disease. This explains why hypertension cannot be cured even if a high grade stenosis has been removed. In addition, thromb- and cholesterol-embolic material is often mobilized during an invasive procedure and leads to renaparenchymatous ischemia which sustains hypertension after intervention. An individual evaluation of profit versus risk is important for the decision for or against an invasive procedure, especially since there is no sufficient evidence for a decrease of mortality after interventions of RAS. The optimal conservative treatment, including the treatment of atherosclerotic risk factors is recommended.

Intra-arterial haemodynamic changes during cerebral three-dimensional rotational angiography

Three-dimensional rotational angiography (3DRA) is useful for detecting, classifying and planning treatment for intracranial aneurysms. Prolonged contrast material (CM) injection, required for 3DRA, might cause blood pressure changes in the selectively catheterized artery. The purpose of this study was to assess the extent and clinical relevance of haemodynamic changes in the selected artery during 3DRA. Twenty-five consecutive patients with intracranial aneurysms were prospectively examined with 3DRA (18 ml, 3 ml/s power injector) for planning treatment. Intra-arterial pressure was measured in the internal carotid or vertebral artery by using a pressure guidewire. Mean and systolic blood pressure acquired by the guidewire (Pd) and fractional flow reserve (FFR) were measured before, during and after CM injection. The extent of Pd and FFR changes was evaluated by Student's t-test and linear regression analysis and their clinical relevance with the limits-of-agreement analysis. Mean systolic Pd and FFR increased significantly (P<0.001) from 105.2+/-22 mmHg and 0.98+/-0.04, respectively, at the baseline to 118.1+/-23 mmHg and 1.09+/-0.12, respectively, during injection and decreased thereafter to baseline. The correlation between mean and systolic Pd during injection and at baseline was moderate (r(2)=0.47 and 0.63, respectively) but remained significant (P=0.001 and <0.001, respectively). Moderate bias and range of agreement were found for systolic Pd (12.8+/-29.2 mmHg) and FFR (0.1+/-0.24). Selective CM injection during 3DRA causes a temporary but clinically tolerable increase in blood pressure and pressure gradient.

Intra-arterial Pressure Monitoring in Patients with Peripheral Vascular Disease

Intra-arterial Pressure Monitoring in Patients with Peripheral Vascular Disease

Is it time to celebrate a century of blood pressure management?

Even after a century of hypertension management, several trivial issues have remained unsolved and still result in inadequate control of blood pressure in many patients. We have performed a critical literature review on topics pertaining the assessment and management of hypertension, focusing on the gaps in knowledge and pitfalls of hypertension management in clinical practice. Physicians are often not capable of adequately measuring blood pressure themselves; the office blood pressure recordings are not sufficiently reliable and the timing of the start of the treatment is often not satisfactory. However, much progress has been made in the past century. Research in this field not only expanded the potential of blood pressure measurements for risk stratification and risk management but also identified many erroneous assumptions and technical mistakes. An important step forward may be the development of affordable 'high tech' blood pressure measuring devices that continuously monitor the intra-arterial pressure in a noninvasive way to eliminate human factors and equipment errors. Technological advances will also provide adequate data storage and software allowing management on an international scale. Hypertension management can almost be celebrated; however, the pressure is still on!

Central Blood Pressure and Hypertension

During the 20th century, the brachial artery auscultatory method of blood pressure (BP) measurement has been the major basis for our understanding of clinical hypertension. First, the height of systolic (S) and diastolic (D) BP was used to define cardiovascular (CV) risk. Second, BP reduction by drug treatment was shown to be associated with a substantial decrease of CV risk in several varieties of high BP, including systolic hypertension in the elderly.1,2 However, drug treatment often reduced DBP more than SBP, resulting in increased pulse pressures (PP) and the related arterial stiffness. An associated increase in coronary risk was also observed.1,3 Because PP and arterial stiffness did not respond readily to drug treatment and was made even less responsive by aging, it has been suggested and shown that mechanical factors such as PP, arterial stiffness, and wave reflections, preferably measured by central (aortic or carotid) BP, should be fully investigated. Because the majority of the studies used noninvasive peripheral BPs the need arose for invasive methods to verify and validate central BP measurement in the evaluation of CV risk.4 In the present issue of this journal, Jankowski et al5 established, in a 4.5-year follow-up of 1109 patients undergoing coronary angiography, that central BP was a significant and independent predictor of CV risk, as potent as cardiac ejection fraction and more powerful than brachial sphygmomanometric measurements. For these coronary patients, the pulsatile …

A long-term moderate magnesium-deficient diet aggravates cardiovascular risks associated with aging and increases mortality in rats

The present study aimed to show whether long-term moderate magnesium (Mg)-deficient (150 mg/kg) and Mg-supplemented (3200 mg/kg) diets (versus control diet: 800 mg/kg), modified the occurrence of cardiovascular risk induced by aging in the rat. Cardiovascular and arterial functions were determined by a systemic hemodynamic study and by ex vivo measurements of vasoconstriction and endothelium dependent-vasorelaxation. Arterial wall structure was determined using pressure myograph chamber and histomorphometric methods. The main changes observed in old rats (96 weeks old) fed a control diet, in comparison to adult rats (16 weeks old) were increased pulse pressure, a loss of aortic endothelium-dependent relaxation, increased aortic wall thickness and a decrease of the aortic wall elastin/collagen ratio. Long-term moderate Mg deficiency progressively increased systolic blood pressure. Intra-arterial pulse pressure was higher in Mg-deficient old rats than in age-matched control rats. Histological examination showed that Mg deficiency increased the age-induced deleterious effects on composition and structure of aorta (media thickness, increased collagen content and reduction in the elastin/collagen ratio), which lead to large artery rigidity. Hypertension and increased pulse pressure may have contributed to the increase in the mortality rate observed in the hypertensive Mg-deficient group. Although the long-term Mg-supplemented diet lowered blood pressure and decreased the mortality rate, it had no significant effect on aortic wall thickening and stiffening. It is suggested that a long-term and moderate Mg-deficient diet increases age-induced arterial thickness and stiffness in rats, and thus increases the cardiovascular risks incurred by aging.

Pleiotropic effects: Should statins be considered an essential component in the treatment of dyslipidemia?

Cardiovascular disease (CVD) is the leading cause of death in the developed world. Lower risks of morbidity and mortality in trials of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor (statin) have changed the conventional wisdom regarding lipid lowering. Since 2001, there have been surprising results concerning the early benefits of statin therapy, which suggest that some benefits may be derived from effects other than those of simply improving dyslipidemias. The earlier than expected CVD benefits from statin trials have led to the theory that statins have effects other than, or concomitant to, the benefits on serum lipid levels, and that these effects may be at least partly responsible for their early and often significant reduction in CVD risk. These have been defined as pleiotropic effects. Possible means by which statins reduce CVD risk independent of their lipid regulation may include antithrombotic and anti-inflammatory effects, antioxidation, plaque stabilization, and endothelial wall relaxation resulting in lower intra-arterial pressure and increased blood flow.