PURPOSE: There is no data about the effect of anti-embolism stockings on intrasession hemodynamics in end stage renal disease patients on hemodialysis (HD). We investigated whether it affects the hemodynamic changes during HD or not. METHODS: We performed 2 HD sessions, before (stocking negative, SN) and after (stocking positive, SP) putting on thigh-high anti-embolism stockings in 11 ESRD patients on HD. In each session, cardiac output (CO), stroke volume (SV), central blood volume (CBV), and peripheral resistance (PR) were measured by ultrasound velocity dilution method at 1 and 3 hours of HD. Ultrafiltration (UF) amount was matched during study. Hemodynamic variables were compared between SN and SP. RESULTS: Mean ages were 51+/-14 years, female was 8, diabetes mellitus was 4, and duration of HD was 56.9+/-28.9 months. There were no differences in pre- and post-HD SBP and DBP, UF amount at 1 hr and 3 hr of HD, and total UF amount between SN and SP. At 1 hr of HD, CBV was greater in SP than in SN (0.85+/-0.32 L vs. 0.93+/-0.32 L, p=0.003). CO (5.56+/-1.22 L/min vs. 5.14+/-1.35 L/min, p=0.075) and SV (73.77+/-19.11 mL vs. 68.95+/-22.21 mL, p=0.05) tended to be increased in SP than in SN. However, there were no differences in TPR between 2 groups. At 3 hr of HD, there were no differences in all hemodynamic variables bewteen SP and SN. CONCLUSION: At early phase of HD, anti-embolism stockings seem to increase CBV, but this effect seems to be attenuated at later phase.
Blood Volume ; Cardiac Output ; Cardiovascular Physiological Phenomena ; Diabetes Mellitus ; Female ; Hemodynamics ; Humans ; Kidney Failure, Chronic ; Renal Dialysis ; Stockings, Compression ; Stroke Volume ; Ultrafiltration ; Vascular Resistance

BACKGROUND: Melatonin has been shown to attenuate the reflex sympathetic increases that arise in response to orthostatic challenges. We tested the hypothesis that the attenuated sympathetic increase induced by melatonin premedication may weaken the arterial blood pressure (ABP) preserving the capability during acute hypotension, thereby altering dynamic cerebral autoregulation and causing a further decrease in cerebral blood flow (CBF). METHODS: Acute hypotension was induced in 12 healthy subjects by releasing bilateral thigh cuffs before and after an oral dose of melatonin (0.2 mg/kg). Heart rate (HR), arterial blood pressure (ABP), Modelflow estimate of cardiac output (CO), total peripheral resistance (TPR) and cerebral blood flow velocity (CBFV) by transcranial Doppler were measured. RESULTS: Steady state HR, the mean arterial pressure and CBFV were not altered 60 minutes after melatonin ingestion. Reduced systolic arterial pressure (DeltaSAP), changes in HR (DeltaHR), CO (DeltaCO), and TPR (DeltaTPR), DeltaHR/DeltaSAP and percentage restoration of SAP were not affected after a temporal decrease in ABP induced by thigh cuff release. In the cerebral circulation, melatonin did not affect changes in CBFV, cerebrovascular resistance index, the rate of regulation and percentage restoration of CBFV following a sudden decrease in ABP. CONCLUSIONS: Contrary to our hypothesis, melatonin did not affect the rapid vasodilatory and recovery responses of cardiovascular and dynamic cerebral autoregulation. These results suggest that melatonin premedication may not impair ABP and CBF preserving capability induced by sudden postural changes or hemorrhage.
Arterial Pressure ; Blood Flow Velocity ; Blood Pressure ; Cardiac Output ; Cerebrovascular Circulation ; Eating ; Heart Rate ; Hemorrhage ; Homeostasis ; Humans ; Hypotension ; Male ; Melatonin ; Premedication ; Reflex ; Thigh ; Vascular Resistance

OBJECTIVETo observe the sensitivity of stroke volume variation (SVV) for assessing volume change during induction period of general anesthesia.

METHODSPatients who underwent orthopaedic surgery under general anesthesia and mechanical ventilation were divided into two groups randomly. Patients in the group Ⅰwere subjected to progressive central hypovolemia and correction of hypovolemia sequentially; patients in the Group Ⅱ were exposed to hypervolemia alone. Each step was implemented after 5 minutes when the hemodynamics was stable. SVV and cardiac index (CI) were recorded, and Pearson's product-moment correlation was used to analyze correlation between SVV and CI.

RESULTSForty patients were included in this study, 20 cases in each group. For group Ⅰ patients, SVV was increased significantly along with blood volume reduction, and changes in CI were negatively correlated with changes in SVV (r=-0.605, P<0.01); SVV decreased significantly along with correction of blood volume; changes in CI were negatively correlated with changes in SVV (r=-0.651, P<0.01). For group Ⅱ patients, along with blood volume increase, SVV did not change significantly; changes in CI revealed no significant correlation with changes in SVV (r=0.067, P>0.05).

CONCLUSIONSVV is a useful indicator for hypovolemia, but not for hypervolemia.

Adult ; Aged ; Arterial Pressure ; Blood Volume ; Cardiac Output ; Central Venous Pressure ; Female ; Humans ; Male ; Middle Aged ; Perioperative Period ; Stroke Volume

BACKGROUND AND PURPOSE: External counterpulsation (ECP) is a noninvasive method used to enhance cerebral perfusion by elevating the blood pressure in ischemic stroke. However, the response of the beat-to-beat blood pressure variability (BPV) in ischemic stroke patients during ECP remains unknown. METHODS: We enrolled recent ischemic stroke patients and healthy controls. Changes in the blood flow velocities in bilateral middle cerebral arteries and the continuous beat-to-beat blood pressure before, during, and after ECP were monitored. Power spectral analysis revealed that the BPV included oscillations at very low frequency (VLF; <0.04 Hz), low frequency (LF; 0.04-0.15 Hz), and high frequency (HF; 0.15-0.40 Hz), and the total power spectral density (TP; <0.40 Hz) and LF/HF ratio were calculated. RESULTS: We found that ECP significantly increased the systolic and diastolic blood pressures in both stroke patients and controls. ECP decreased markedly the systolic and diastolic BPVs at VLF and LF and the TP, and the diastolic BPV at HF when compared with baseline. The decreases in diastolic and systolic BPV reached 37.56% and 23.20%, respectively, at VLF, 21.15% and 12.19% at LF, 8.76% and 16.59% at HF, and 31.92% and 23.62% for the total TP in stroke patients, which did not differ from those in healthy controls. The change in flow velocity on the contralateral side was positively correlated with the total TP systolic BPV change induced by ECP (r=0.312, p=0.035). CONCLUSIONS: ECP reduces the beat-to-beat BPV when increasing the blood pressure and cerebral blood flow velocity in ischemic stroke patients. ECP might be able to improve the clinical outcome by decreasing the beat-to-beat BPV in stroke patients, and this should be explored further in future studies.
Blood Flow Velocity ; Blood Pressure* ; Cerebrovascular Circulation* ; Counterpulsation* ; Humans ; Methods ; Middle Cerebral Artery ; Perfusion ; Stroke*

Head-out water immersion induces marked increase in the cardiac stroke volume. The present study was undertaken to characterize the stroke volume change by analyzing the aortic blood flow and left ventricular systolic time intervals. Ten men rested on a siting position in the air and in the water at 34.5degreeC for 30 min each. Their stroke volume, heart rate, ventricular systolic time intervals, and aortic blood flow indices were assessed by impedance cardiography. During immersion, the stroke volume increased 56%, with a slight (4%) decrease in heart rate, thus cardiac output increased ~50%. The slight increase in R-R interval was due to an equivalent increase in the systolic and diastolic time intervals. The ventricular ejection time was 20% increased, and this was mainly due to a decrease in pre-ejection period (28%). The mean arterial pressure increased 5 mmHg, indicating that the cardiac afterload was slightly elevated by immersion. The left ventricular end-diastolic volume index increased 24%, indicating that the cardiac preload was markedly elevated during immersion. The mean velocity and the indices of peak velocity and peak acceleration of aortic blood flow were all increased by ~30%, indicating that the left ventricular contractile force was enhanced by immersion. These results suggest that the increase in stroke volume during immersion is characterized by an increase in ventricular ejection time and aortic blood flow velocity, which may be primarily attributed to the increased cardiac preload and the muscle length-dependent increase in myocardial contractile force.
Acceleration ; Arterial Pressure ; Blood Flow Velocity ; Cardiac Output ; Cardiography, Impedance ; Heart Rate ; Humans ; Immersion* ; Male ; Stroke Volume ; Systole ; Water*

Utilizing the third-order polynomial curve fitted to the experimental data, which represents the relationship between cerebral blood flow (CBF) and mean artery blood pressure (MABP), we constructed a lumped-parameter dynamic model with 5 elements. In this model; the resistance is not constants it is determined by the fitted curve. We simulated the process of CBF autoregulation numerically by solving the govern equation of this model and got quite accurate results. Furthermore, we studied the influence of hemodynamic parameters on the CBF autoregulation by this model and proved that the characteristic resistance is the most important factor.
Blood Flow Velocity ; Blood Pressure ; physiology ; Cerebrovascular Circulation ; physiology ; Homeostasis ; Humans ; Hypotension ; physiopathology ; Models, Biological ; Oxygen ; metabolism ; Regional Blood Flow

In order to study the cardiovascular hemodynamic characteristics and evaluate the blood pump, we made a series of cardiovascular simulation devices which could reflect the hemodynamics of blood circulation system by the elastic chamber model, and tested the relations between cardiovascular hemodynamic parameters (such as systole pressure, diastole pressure, average pressure, pulsative pressure, flow rate) and ventricular afterload (peripheral resistance and vascular compliance) as well as cardiac output, diastolic period, systole period and preload. The effect of the parameters on the arterial pressure and flow rate was estimated when any one of the parameters was changed. The result of simulating experiment was coincided with that deduced from mathematical model and physiologic condition. Therefore the series of cardiovascular simulation devices can reflect the hemodynamics of blood circulation.
Blood Pressure ; physiology ; Cardiac Output ; physiology ; Cardiovascular Physiological Phenomena ; In Vitro Techniques ; Models, Cardiovascular ; Vascular Resistance ; physiology

OBJECTIVETo explore the role of central venous pressure (CVP), global end diastolic volume index (GEDI) and extravascular lung water index (ELWI) monitoring in patients with septic shock during fluid resuscitation by pulse induced continuous cardiac output (PiCCO) test.

METHODSForty-six patients with severe sepsis and septic shock were enrolled in this study. Hemodynamic monitoring was performed during fluid resuscitation and the data including CVP, GEDI and ELWI were collected to analyze their relationship and the clinical values.

RESULTSIn patients with septic shock, CVP showed a weak linear correlation with GEDI during fluid resuscitation (r=0.137, P=0.009). In the subgroups stratified with CVP cut-off values of 8 mmHg and 12 mmHg, the correlation coefficient between CVP and GEDI was 0.149 (P=0.029) in CVP<8 mmHg group, 0.075 (P=0.462) in 8 mmHg ≤ CVP ≤ 12 mmHg group, and 0.049 (P=0.726) in CVP>12 mmHg group. In the total of 367 data groups obtained, CVP showed no linear correlation with ELWI (r=0.040, P=0.445). In the CVP subgroups, CVP and ELWI were weakly correlated in CVP<8 mmHg group (r=0.221, P=0.001), but they showed no correlations in 8 mmH g≤ CVP ≤ 12 mmHg and CVP>12 mmHg groups (r=-0.047, P=0.646; r=0.042, P=0.765).

CONCLUSIONThere is no significant linear correlation between CVP and GEDI or between CVP and ELWI in patients with septic shock. CVP can not reflect the circulatory blood volume or the degree of pulmonary edema.

Blood Volume ; Cardiac Output ; Central Venous Pressure ; Extravascular Lung Water ; Fluid Therapy ; Humans ; Pulmonary Edema ; Resuscitation ; Shock, Septic ; therapy

As one of the important indexes for the diagnosis and treatment of cardiovascular diseases, cardiac output can reflect the state of cardiovascular system timely, and can play a guiding role in the treatment of related diseases. In recent years detection technology of cardiac output has caused great attention, especially minimally invasive and non-invasive methods. In this paper, the principle of non-invasive detection methods and their recent developments are described, and various detection methods are also analyzed.
Cardiac Output ; Cardiovascular Diseases ; diagnosis ; Cardiovascular Physiological Phenomena ; Humans

Ischemia can cause decreased cerebral neurovascular coupling, leading to a failure in the autoregulation of cerebral blood flow. This study aims to investigate the effect of varying degrees of ischemia on cerebral hemodynamic reactivity using in vivo real-time optical imaging. We utilized direct cortical stimulation to elicit hyper-excitable neuronal activation, which leads to induced hemodynamic changes in both the normal and middle cerebral artery occlusion (MCAO) ischemic stroke groups. Hemodynamic measurements from optical imaging accurately predict the severity of occlusion in mild and severe MCAO animals. There is neither an increase in cerebral blood volume nor in vessel reactivity in the ipsilateral hemisphere (I.H) of animals with severe MCAO. The pial artery in the contralateral hemisphere (C.H) of the severe MCAO group reacted more slowly than both hemispheres in the normal and mild MCAO groups. In addition, the arterial reactivity of the I.H in the mild MCAO animals was faster than the normal animals. Furthermore, artery reactivity is tightly correlated with histological and behavioral results in the MCAO ischemic group. Thus, in vivo optical imaging may offer a simple and useful tool to assess the degree of ischemia and to understand how cerebral hemodynamics and vascular reactivity are affected by ischemia.
Animals ; Arteries ; Blood Volume ; Cerebrovascular Circulation ; Hemodynamics* ; Homeostasis ; Infarction, Middle Cerebral Artery* ; Ischemia ; Middle Cerebral Artery* ; Neurons ; Neurovascular Coupling ; Optical Imaging ; Rodentia* ; Stroke