Impaired sympathetic response before intradialytic hypotension: a study based on spectral analysis of heart rate and pressure variability

1999 ◽  
Vol 96 (1) ◽  
pp. 23-31 ◽  
Author(s):  
Gualtiero PELOSI ◽  
Michele EMDIN ◽  
Clara CARPEGGIANI ◽  
Maria Aurora MORALES ◽  
Marcello PIACENTI ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Systolic Blood Pressure ◽  
Pressure Fluctuations ◽  
Power Spectra ◽  
Low Frequency ◽  
Autonomic Response ◽  
Dialysis Session ◽  
Intradialytic Hypotension ◽  
Sympathetic Response ◽  
A Minor

The purpose of this study was to evaluate the autonomic response to standard haemodialysis and the changes associated with the onset of intradialytic hypotension in 12 normotensive patients with uraemia. Power spectra of R–R interval and of blood pressure fluctuations were obtained during a standard dialysis session and estimated in the low-frequency (LF, 30–150 ;mHz) and high-frequency (HF, 150–400 ;mHz) range. The absolute power of the LF component of blood pressure variations and the LF/HF ratio of R–R interval were assumed as indexes of sympathetic activity. Standard haemodialysis induced hypotension in six patients (unstable) while a minor pressure decline was present in the other six (stable). Normalized blood volume before dialysis and percentage volume reduction were similar in the two groups. Tachycardia in response to pressure and volume decrease was more pronounced in stable than in unstable patients, as evidenced by a higher slope of the relation between R–R interval and systolic blood pressure (7.9 versus 0.9 ;ms/mmHg, P< 0.01). Sympathetic tone was enhanced during early dialysis in all patients (+2±1 for R–R LF/HF ratio, +2.4±0.6 ;mmHg2 and +7.2±2 ;mmHg2 for absolute LF power of diastolic and of systolic blood pressure respectively, P< 0.05), compared with baseline predialysis values. During late dialysis, unstable patients showed an impairment of sympathetic activation which preceded hypotension and was maximal during the crisis (-2.9±1.4 for R–R LF/HF ratio, -2.7±1.4 ;mmHg2 and -8.6±4.0 ;mmHg2 for absolute LF power of diastolic and of systolic blood pressure respectively, P< 0.05). On the contrary, stable patients showed constantly elevated indexes (+3.7±1.4 for R–R LF/HF ratio, +5.9±2.7 ;mmHg2 and +13.3±6.2 ;mmHg2 for LF of diastolic and of systolic blood pressure, P< 0.05). Values returned to predialysis levels after the end of the dialysis session in all patients. We conclude that standard haemodialysis activates a marked and reversible sympathetic response in both stable and unstable uraemic patients. However, in unstable patients, such activation is impaired in late dialysis, therefore contributing to the onset of the hypotensive crisis.

Effect of heavy exercise on spectral baroreflex sensitivity, heart rate, and blood pressure variability in well-trained humans

2008 ◽  
Vol 295 (3) ◽  
pp. H1150-H1155 ◽  
Author(s):  
François Cottin ◽  
Claire Médigue ◽  
Yves Papelier
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Systolic Blood Pressure ◽  
Exercise Test ◽  
Blood Pressure Variability ◽  
Baroreflex Sensitivity ◽  
Low Frequency ◽  
Mechanical Effect ◽  
Heavy Exercise ◽  
Gas Exchange Parameters

The aim of the study was to assess the instantaneous spectral components of heart rate variability (HRV) and systolic blood pressure variability (SBPV) and determine the low-frequency (LF) and high-frequency baroreflex sensitivity (HF-BRS) during a graded maximal exercise test. The first hypothesis was that the hyperpnea elicited by heavy exercise could entail a significant increase in HF-SBPV by mechanical effect once the first and second ventilatory thresholds (VTs) were exceeded. It was secondly hypothesized that vagal tone progressively withdrawing with increasing load, HF-BRS could decrease during the exercise test. Fifteen well-trained subjects participated in this study. Electrocardiogram (ECG), blood pressure, and gas exchanges were recorded during a cycloergometer test. Ventilatory equivalents were computed from gas exchange parameters to assess VTs. Spectral analysis was applied on cardiovascular series to compute RR and systolic blood pressure power spectral densities, cross-spectral coherence, gain, and α index of BRS. Three exercise intensity stages were compared: below (A1), between (A2), and above (A3) VTs. From A1 to A3, both HF-SBPV (A1: 45 ± 6, A2: 65 ± 10, and A3: 120 ± 23 mm2Hg, P < 0.001) and HF-HRV increased (A1: 20 ± 5, A2: 23 ± 8, and A3:40 ± 11 ms2, P < 0.02), maintaining HF-BRS (gain, A1: 0.68 ± 0.12, A2: 0.63 ± 0.08, and A3: 0.57 ± 0.09; α index, A1: 0.58 ± 0.08, A2: 0.48 ± 0.06, and A3: 0.50 ± 0.09 ms/mmHg, not significant). However, LF-BRS decreased (gain, A1: 0.39 ± 0.06, A2: 0.17 ± 0.02, and A3: 0.11 ± 0.01, P < 0.001; α index, A1: 0.46 ± 0.07, A2: 0.20 ± 0.02, and A3: 0.14 ± 0.01 ms/mmHg, P < 0.001). As expected, once VTs were exceeded, hyperpnea induced a marked increase in both HF-HRV and HF-SBPV. However, this concomitant increase allowed the maintenance of HF-BRS, presumably by a mechanoelectric feedback mechanism.

Spectral Analysis of Systolic Blood Pressure and Heart Rate after Heart Transplantation in Children

1995 ◽  
Vol 88 (1) ◽  
pp. 95-102 ◽  
Author(s):  
Isabelle Constant ◽  
Arlette Girard ◽  
Jérôme Le Bidois ◽  
Elizabeth Villain ◽  
Dominique Laude ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Heart Rate Variability ◽  
Heart Transplantation ◽  
Systolic Blood Pressure ◽  
High Frequency ◽  
Power Spectra ◽  
Critical Factor ◽  
Group B ◽  
Cardiac Afferents

1. The aim of the study was to examine the short-term variability in blood pressure and heart rate in 19 children who had received heart transplants and in eight normal control children. 2. Blood pressure was determined by a finger arterial pressure device. We examined the power spectra for heart rate and systolic blood pressure in the supine and tilted positions. In addition, we studied the acute changes in blood pressure and heart rate during active standing. 3. In the transplanted children we could distinguish two groups (groups A and B) in whom heart rate variability differed, although in both it was greatly reduced compared with controls (group C). In group A there were no significant fluctuations in the mid-frequency range for heart rate. The gain of the relationship between systolic blood pressure and heart rate was very low and there were virtually no heart rate changes associated with passive tilting. 4. By contrast, in group B transplant patients the heart rate variability, as assessed by standard deviation, was about half that of normal controls. The power spectra attenuation was greater in the high-frequency than in the mid-frequency bands. On passive tilting the latter became enhanced, but not the high-frequency variability. On active standing the tachycardic response was about half that of controls. The findings suggest some reinnervation involving cardiac sympathetic fibres to a greater degree than the fast-responding vagal fibres. 5. In both groups A and B the drop in systolic blood pressure observed early in active standing was about 4–6 times as great as in controls. One possible mechanism could be the loss of cardiac afferents. 6. Time since operation was a critical factor for reinnervation, since all subjects from group B were transplanted more than 44 months prior to the recording. 7. We conclude that in a proportion of children who have received heart transplantation there is a delayed reinnervation of the heart, which probably involves sympathetic effectors rather than the vagus.

The Baffle Blocks Effects of Pressure Characteristics on USBR III Basin Floor

2012 ◽  
Vol 212-213 ◽  
pp. 821-825
Author(s):  
Keyvan Nasiri ◽  
Mohammad Reza Kavianpour ◽  
Siavash Haghighi
Keyword(s):  
Energy Dissipation ◽  
Hydraulic Jump ◽  
Pressure Fluctuations ◽  
Power Spectra ◽  
Low Frequency ◽  
Dominant Frequency ◽  
Energy Dissipation Rate ◽  
Tension And Compression ◽  
Basin Floor ◽  
Sequent Depth

The principle of energy dissipation in stilling basin is based on hydraulic jump formation. Due to the inherent fluctuating characteristic of the hydraulic jump, basin floor is subjected to variations of pressure, resulting in unstableness due to uplift forces. To increase the efficiency of the stilling basins and improve the energy dissipation rate, one or two rows of baffle blocks are applied on the basin floor. Causing a forced hydraulic jump, tension and compression forces are exerted by pressure fluctuations of rotating roller zone of hydraulic jump. In this investigation, to observe the impacts of baffle blocks on pressure fluctuations on basin floor, a standard USBR basin model type III was constructed, and then a second row of blocks was added to the basin. A set of pressure tubes was fixed along the axis of the basin to measure the static and dynamic pressures on basin floor. The results were expressed in dimensionless parameters including C-p, C+p, C’p, Cp. Also, power spectra of pressure fluctuations were calculated. The results show a decreasing trend in root mean square of pressure fluctuations as distancing from toe of jump along the basin with and without baffle blocks. Also, mean pressure increases when water jet strokes the basin then decreases under roller zone of jump and increases again after sequent depth. The spectral analysis indicates that the dominant frequency is between 10 rad/s and 35 rad/s and pressure fluctuations have low frequency characteristics.

Implementation of an Algorithm Utilizing Saline Versus Albumin for the Treatment of Intradialytic Hypotension

2018 ◽  
Vol 53 (2) ◽  
pp. 159-164
Author(s):  
Ling Yin ◽  
Dennis Dubovetsky ◽  
Patricia Louzon-Lynch
Keyword(s):  
Blood Pressure ◽  
Treatment Failure ◽  
Pharmacy Education ◽  
Dialysis Session ◽  
Intradialytic Hypotension ◽  
Dialysis Patients ◽  
Total Cost ◽  
Treatment Failure Rate ◽  
Time Required ◽  
Algorithm Implementation

Background: Intradialytic hypotension (IDH) is the most commonly reported complication of hemodialysis (HD) treatment. At our institution, dialysis patients often have both 25% albumin and normal saline ordered as rescue options for management of IDH, without specification of which agent to use first. Objective: The purpose of this study was to determine the effect of an algorithm for IDH management. Methods: A retrospective study was conducted in HD patients who experienced IDH. The primary end point was to evaluate albumin use. Secondary end points included albumin costs, study fluid use per dialysis session, compliance with algorithm, efficacy of hypotension reversal to mean arterial pressure (MAP) ⩾60 mm Hg, percentage of target ultrafiltration achieved, time required to restore systolic blood pressure ⩾90 mm Hg, blood pressure post–study fluids, IDH treatment failure rate, and early termination of dialysis as a result of persistent IDH. Results: Implementation of the algorithm was observed in 94% of patients (n = 90). Total albumin use was significantly reduced from 11 400 to 4700 mL in the pre– (n = 90) and post–algorithm implementation group (n = 90; P < 0.001). The associated total cost of albumin was reduced by 59% ($10 534 vs $4343; P < 0.001). No statistical differences were observed between the 2 groups regarding efficacy of hypotension reversal to MAP ⩾60 mm Hg, early HD termination, or treatment failure rates (all P = 0.99). Conclusion and Relevance: Implementation of an evidence-based, standardized algorithm and pharmacy education to nursing staff can result in a reduction in albumin use and its associated drug costs for IDH management without compromising efficacy of IDH reversal.

Cardiovascular autonomic modulation and activity of carotid baroreceptors at altitude

1998 ◽  
Vol 95 (5) ◽  
pp. 565-573 ◽  
Author(s):  
Luciano BERNARDI ◽  
Claudio PASSINO ◽  
Giammario SPADACINI ◽  
Alessandro CALCIATI ◽  
Robert ROBERGS ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Systolic Blood Pressure ◽  
High Altitude ◽  
Sea Level ◽  
Skin Blood Flow ◽  
Low Frequency ◽  
Sympathetic Activation ◽  
High Altitude Natives

1.To assess the effects of acute exposure to high altitude on baroreceptor function in man we evaluated the effects of baroreceptor activation on R–R interval and blood pressure control at high altitude. We measured the low-frequency (LF) and high-frequency (HF) components in R–R, non-invasive blood pressure and skin blood flow, and the effect of baroreceptor modulation by 0.1-Hz sinusoidal neck suction. Ten healthy sea-level natives and three high-altitude native, long-term sea-level residents were evaluated at sea level, upon arrival at 4970 ;m and 1 week later. 2.Compared with sea level, acute high altitude decreased R–R and increased blood pressure in all subjects [sea-level natives: R–R from 1002±45 to 775±57 ;ms, systolic blood pressure from 130±3 to 150±8 ;mmHg; high-altitude natives: R–R from 809±116 to 749±47 ;ms, systolic blood pressure from 110±12 to 125±11 ;mmHg (P< 0.05 for all)]. One week later systolic blood pressure was similar to values at sea level in all subjects, whereas R–R remained elevated in sea-level natives. The low-frequency power in R–R and systolic blood pressure increased in sea-level natives [R–R-LF from 47±8 to 65±10% (P< 0.05), systolic blood pressure-LF from 1.7±0.3 to 2.6±0.4 ln-mmHg2 (P< 0.05)], but not in high-altitude natives (R–R-LF from 32±13 to 38±19%, systolic blood pressure-LF from 1.9±0.5 to 1.7±0.8 ln-mmHg2). The R–R-HF decreased in sea-level natives but not in high-altitude natives, and no changes occurred in systolic blood pressure-HF. These changes remained evident 1 week later. Skin blood flow variability and its spectral components decreased markedly at high altitude in sea-level natives but showed no changes in high-altitude natives. Neck suction significantly increased the R–R- and systolic blood pressure-LF in all subjects at both sea level and high altitude. 3.High altitude induces sympathetic activation in sea-level natives which is partially counteracted by active baroreflex. Despite long-term acclimatization at sea level, high-altitude natives also maintain active baroreflex at high altitude but with lower sympathetic activation, indicating a persisting high-altitude adaptation which may be genetic or due to baroreflex activity not completely lost by at least 1 year's sea-level residence.

Plasma Na-K Atpase Inhibitor Activity and Intracellular Ions during Hemodialysis

1993 ◽  
Vol 16 (1) ◽  
pp. 23-30 ◽  
Author(s):  
J.M. Krzesinski ◽  
F. Du ◽  
M.L. Pequeux ◽  
G.L. Rorive
Keyword(s):  
Blood Pressure ◽  
Systolic Blood Pressure ◽  
Weight Change ◽  
Dialysis Session ◽  
Atpase Inhibitor ◽  
Inhibitor Activity ◽  
Hypertensive Patients ◽  
Uremic Patients ◽  
The Relationship ◽  
Intracellular Ions

We have investigated the relationship between plasma Na-K ATPase inhibitor activity (EDLS) and intracellular ions in 37 uremic hemodialysed hypertensive patients, and in 20 normotensive non uremic controls (NC). As compared with the NC population, significantly enhanced values for erythrocyte (RBC) Na, Ca, platelet cytosolic Ca and EDLS were observed in all the uremic patients tested just before a dialysis session, as well as a decrease in RBC Ca ATPase and in the platelet pH. In uremia, significant correlations have been noted between RBC Na and platelet Ca (r = 0.6) or systolic BP (r = 0.45); between platelet Ca and systolic blood pressure (r = 0.8) or diastolic BP (r = 0.5) and between EDLS and RBC Na, Ca or platelet Ca (r = 0.5). Anti-hypertensive treatment has no influence on these parameters. During dialysis, a significant decrease has been noted in RBC Na, Ca, platelet Ca, SBP (only in untreated patients) and EDLS and an increase in RBC Ca ATPase and platelet pH. These modifications are significantly correlated with the weight change.

Evidence of Profiled Hemodialysis Efficacy in the Treatment of Intradialytic Hypotension

1998 ◽  
Vol 21 (7) ◽  
pp. 398-402 ◽  
Author(s):  
L. Colì ◽  
G. La Manna ◽  
V. Dalmastri ◽  
A. De Pascalis ◽  
G. Pace ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Blood Volume ◽  
Sodium Concentration ◽  
Dialysis Session ◽  
Intradialytic Hypotension ◽  
Dialysis Patients ◽  
Non Invasive ◽  
Comparison Of The Results ◽  
Weight Decrease ◽  
Dialysate Sodium

In the last 10 years the percentage of dialysis patients suffering from clinical intradialytic intolerance has greatly increased. Profiled hemodialysis (PHD) is a new technical approach, alternative to standard hemodialysis (SHD) for the treatment of intradialytic symptomatic hypotension. It is based on intradialytic modulation of the dialysate sodium concentration, using a dialysate sodium concentration profile elaborated by a new mathematical kinetic model. The aim of PHD is to reduce the intradialytic blood volume decrease, thanks to a dialysate sodium profile, which allows a reduction in the plasma osmolarity decrease, thereby boosting intravascular fluid refilling. This work aims at clinically validating the PHD technique, by testing its ability, against SHD, to maintain a more stable intradialytic blood volume; this evaluation was supported by monitoring some hemodynamic parameters. Twelve dialysis patients on SHD treatment were selected because of their intradialytic symptomatic hypotension. Twelve SHD (one per patient) and 12 PHD sessions (one per patient) were performed to achieve the same sodium mass removal and body weight decrease on both PHD and SHD. During these sessions we monitored the blood volume variation % by the critline (a non invasive blood volume monitoring device), the mean blood pressure and heart rate directly and, finally, the stroke volume and cardiac output indirectly by bidimensional doppler-echocardiography. Comparison of the results obtained with the two techniques shows PHD to achieve a significantly more stable blood volume, blood pressure and cardiovascular function than SHD, in particular during the second and the third hour of the dialysis session.

Very low frequency blood pressure fluctuations: not only myogenic responsiveness

2008 ◽  
Vol 26 (6) ◽  
pp. 1065-1068 ◽  
Author(s):  
Claude Julien ◽  
J Philip Saul ◽  
Gianfranco Parati
Keyword(s):  
Blood Pressure ◽  
Pressure Fluctuations ◽  
Low Frequency ◽  
Very Low Frequency

Hemodynamic regulation: investigation by spectral analysis

1985 ◽  
Vol 249 (4) ◽  
pp. H867-H875 ◽  
Author(s):  
S. Akselrod ◽  
D. Gordon ◽  
J. B. Madwed ◽  
N. C. Snidman ◽  
D. C. Shannon ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Spectral Analysis ◽  
Pressure Fluctuations ◽  
Low Frequency ◽  
Cardiovascular Control ◽  
Respiratory Frequency ◽  
Atrial Pacing ◽  
Loop Model ◽  
Short Term ◽  
Renin Angiotensin

We investigated the hypothesis that beat-to-beat variability in hemodynamic parameters reflects the dynamic interplay between ongoing perturbations to circulatory function and the compensatory response of short-term cardiovascular control systems. Spontaneous fluctuations in heart rate (HR), arterial blood pressure, and respiration were analyzed by spectral analysis in the 0.02- to 1-Hz frequency range. A simple closed-loop model of short-term cardiovascular control was proposed and evaluated in a series of experiments: pharmacological blockades of the parasympathetic, alpha-sympathetic, beta-sympathetic, and renin-angiotensin systems were used to open the principal control loops in order to examine changes in the spectral pattern of the fluctuations. Atrial pacing was used to examine blood pressure variability in the absence of HR variability. We found that respiratory frequency fluctuations in HR are parasympathetically mediated and that blood pressure fluctuations at this frequency result almost entirely from the direct effect of centrally mediated HR fluctuations. The sympathetic nervous system appears to be too sluggish to mediate respiratory frequency variations. Low-frequency (0.02-0.09 Hz) fluctuations in HR are jointly mediated by the parasympathetic and beta-sympathetic systems and appear to compensate for blood pressure fluctuations at this frequency. Low-frequency blood pressure fluctuations are probably due to variability in vasomotor activity which is normally damped by renin-angiotensin system activity. Blockade of the alpha-adrenergic system, however, does not significantly alter low-frequency blood pressure fluctuations.

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