Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “HEMODYNAMICS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42Linked to original sources
PubMed2006

Noninvasive assessment of cardiac output using thoracic electrical bioimpedance in hemodynamically stable and unstable patients after cardiac surgery: a comparison with pulmonary artery thermodilution.

OBJECTIVE: To compare noninvasive cardiac output (CO)measurement obtained with a new thoracic electrical bioimpedance (TEB) device, using a proprietary modification of the impedance equation, with invasive measurement obtained via pulmonary artery thermodilution. DESIGN: Prospective, observational study. SETTING: Surgical intensive care unit (ICU) of a university-affiliated community hospital. PATIENTS AND PARTICIPANTS: Seventy-four adult patients undergoing elective cardiac surgery with routine pulmonary artery catheter placement. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Simultaneous paired CO and cardiac index (CI) measurements by TEB and thermodilution were obtained in mechanically ventilated patients upon admission to the ICU. For analysis of CI data the patients were subdivided into a hemodynamically stable group and a hemodynamically unstable group. The groups were analyzed using linear regression and tests of bias and precision. We found a significant correlation between thermodilution and TEB (r = 0.83; n < 0.001), accompanied by a bias of -0.01 l/min/m(2) and a precision of +/-0.57 l/min/m(2) for all CI data pairs. Correlation, bias, and precision were not influenced by stratification of the data. The correlation coefficient, bias, and precision for CI were 0.86 (n< 0.001), 0.03 l/min/m(2), and +/-0.47 l/min/m(2) in hemodynamically stable patients and 0.79 (n< 0.001), 0.06 l/min/m(2), and +/-0.68 l/min/m(2) in hemodynamically unstable patients. CONCLUSIONS: Our results demonstrate a close correlation and clinically acceptable agreement and precision between CO measurements obtained with impedance cardiography using a new algorithm to calculate CO from variations in TEB, and those obtained with the clinical standard of care, pulmonary artery thermodilution, in hemodynamically stable and unstable patients after cardiac surgery.

Aged↗
PubMed2007

Age and sex-related differences in dose-dependent hemodynamic response to landiolol hydrochloride during general anesthesia.

OBJECTIVE: Landiolol hydrochloride is a new ultra-short-acting beta(1)-adrenergic receptor blocking agent that is used for patients with tachycardia during general anesthesia. The hemodynamic response to a beta-adrenergic receptor blocking agent is generally dependent on the subject. In the present investigation we investigated the effects of age and sex on the hemodynamic response to different doses of landiolol. METHODS: Following a persistence of tachycardia for more than 1 min, landiolol was infused at 0.03125, 0.0625 and 0.125 mg kg(-1) min(-1) for 1 min followed by 0.01, 0.02 and 0.04 mg kg(-1)min(-1) for 10 min in groups L, M and H, respectively. Heart rate (HR), systolic (sBP) and diastolic blood pressure (dBP) were recorded each minute during the procedure. The respective changes were evaluated using logistic analysis with the equation Y(t) = p + (q - p)/[1 + exp {4m/(q - p))(k - t)}], where p, q, m and k indicate the upper asymptote, lower asymptote, maximum slope and time at the maximum slope. RESULTS: Parameters q and k for HR in group H were smaller than those in group L, whereas the parameters for sBP and dBP were unchanged among the three groups. Parameter q for HR in group H decreased with age of the patient. There was no significant difference in the landiolol-induced change in HR between males and females. CONCLUSION: The hemodynamic response to landiolol is reliably modeled by the logistic function, especially in terms of HR. Landiolol causes a rapid and dose-dependent decrease in HR, whereas landiolol-induced changes in sBP and dBP are independent of dose. The landiolol-induced decrease in HR becomes larger with aging, but shows no sex difference. The logistic model may be useful for studying hemodynamic responses to landiolol based on age and sex differences, and may allow development of an improved monitoring system. IMPLICATION STATEMENT: The logistic function reliably represents the hemodynamic responses to landiolol. Landiolol reduces HR rapidly and in a dose-dependent manner whereas landiolol-induced changes in sBP and dBP are independent of dose. A larger decrease in HR is caused by landiolol in elderly patients, but there is no sex difference in the landiolol-induced change in HR.

Adrenergic beta-Antagonists↗
PubMed2003

Hemodynamic and catecholamine responses during tracheal intubation using a lightwand device (Trachlight) in elderly patients with hypertension.

PURPOSE: Tracheal intubation using a lightwand device (Trachlight) should minimize hemodynamic change by avoiding direct-vision laryngoscopy. We evaluated hemodynamic and catecholamine responses during tracheal intubation using a Trachlight in elderly patients with hypertension. METHODS: Twenty-six hypertensive patients aged over 65 years undergoing orthopedic surgery were randomly divided into two groups, group L (n = 13) and group T (n = 13). Anesthesia was induced with fentanyl (2 microg x kg(-1)) and propofol (1.5 mg x kg(-1)), and then muscle relaxation was obtained with vecuronium (0.15 mg x kg(-1)). The trachea was intubated with either a Macintosh laryngoscope (group L) or a Trachlight (group T). Hemodynamics, plasma catecholamine concentrations, and arterial blood gases were measured before the induction of anesthesia (T0), before tracheal intubation (T1), immediately after tracheal intubation (T2), and 3 min after tracheal intubation (T3). RESULTS: The intubation time was shorter in group T than in group L (12.6 +/- 1.7 vs 23.5 +/- 2.9 s, mean +/- SE; P < 0.01). Compared with the preinduction (T0) value, systolic blood pressure (SBP) showed a significant decrease at T1 and T3 in group L and at T1, T2, and T3 in group T. The heart rate (HR) and plasma norepinephrine (NE) concentration showed no change in either group throughout the time course, whereas the plasma epinephrine (E) concentration showed a significant decrease at T2 and T3 in both groups. The mean values of the rate-pressure product (RPP: HR x SBP) were less than 15000 after tracheal intubation in both groups. There was no significant difference in hemodynamic or catecholamine responses between groups at any point. No patient had ischemic ST-T changes in either group. CONCLUSION: A lightwand has no advantage over a laryngoscope in terms of hemodynamic and plasma catecholamine responses to tracheal intubation in elderly patients with hypertension, despite a shorter intubation time.

Aged↗
PubMed2006

Automatic regulation of hemodynamic variables in acute heart failure by a multiple adaptive predictive controller based on neural networks.

Automated drug-delivery systems that can tolerate various responses to therapeutic agents have been required to control hemodynamic variables with heart failure. This study is intended to evaluate the control performance of a multiple adaptive predictive control based on neural networks (MAPC(NN)) to regulate the unexpected responses to therapeutic agents of cardiac output (CO) and mean arterial pressure (MAP) in cases of heart failure. The NN components in the MAPC(NN) learned nonlinear responses of CO and MAP determined by hemodynamics of dogs with heart failure. The MAPC(NN) performed ideal control against unexpected (1) drug interactions, (2) acute disturbances, and (3) time-variant responses of hemodynamics [average errors between setpoints (+35 ml kg(-1) min(-1) in CO and +/-0 mmHg in MAP) and observed responses; 6.4, 3.7, and 4.2 ml kg(-1) min(-1) in CO and 1.6, 1.4, and 2.7 mmHg (10.5, 20.8, and 15.3 mmHg without a vasodilator) in MAP] during 120-min closed-loop control. The MAPC(NN) could also regulate the hemodynamics in actual heart failure of a dog. Robust regulation of hemodynamics by the MAPC(NN) was attributable to the ability of on-line adaptation to adopt various responses and predictive control using the NN. Results demonstrate the feasibility of applying the MAPC(NN) using a simple NN to clinical situations.

Animals↗
PubMed1995

Doppler echocardiographic pulmonary venous flow-velocity pattern for assessment of the hemodynamic profile in acute congestive heart failure.

The hemodynamic profile of congestive heart failure (CHF) is best described in terms of its two primary sets of hemodynamic parameters, that is, left atrial pressure and cardiac output, each of which has a specific and independently variable hemodynamic cause. To assess whether analysis of the mitral and/or pulmonary venous flow-velocity patterns provides valuable information in the noninvasive assessment of the hemodynamic profile of CHF, these patterns were obtained by using the transthoracic approach in 18 patients with acute CHF with simultaneous measurements of catheter-derived mean pulmonary capillary wedge pressure and thermodilution cardiac index. Measurements were repeated on two occasions in each case: at the acute stage of CHF and 1 to 5 days after treatment. Peak diastolic pulmonary venous forward flow velocity was higher, the ratio of pulmonary venous systolic to diastolic peak forward flow velocity was lower, and the ratio of mitral early diastolic to late diastolic flow velocity was greater in patients with higher mean pulmonary capillary wedge pressure (r = 0.80, n = 36, p < 0.01; r = -0.69, n = 36, p < 0.01; r = 0.71, n = 36, p < 0.01). Peak systolic pulmonary venous forward flow velocity and time-velocity integral of the systolic pulmonary venous flow wave were greater in patients with larger cardiac index (r = 0.80, n = 36, p < 0.01; r = 0.62, n = 36, p < 0.01). In conclusion, two primary sets of hemodynamic parameters, that is, left atrial pressure and cardiac output, can be estimated with Doppler pulmonary venous flow parameters in patients with acute CHF.

Acute Disease↗
PubMedDate not supplied

Comparison of renal hemodynamics in early non-insulin-dependent and insulin-dependent diabetes mellitus.

The differences in deranged renal hemodynamics in non-insulin-dependent diabetes mellitus (NIDDM) and insulin-dependent diabetes mellitus (IDDM) have never been fully investigated. Whether or not autoregulatory mechanism of renal hemodynamics in NIDDM and IDDM is preserved remains to be clarified. In the present study we directly compared renal hemodynamics and its autoregulatory function in the early stage of NIDDM and IDDM before and after short-term glycemic control. Before glycemic control, mildly exaggerated glomerular filtration rate (GFR), subnormal renal plasma flow (RPF), and elevated filtration fraction (FF) were found in NIDDM as well as in IDDM; but there were no differences in these parameters of renal hemodynamics between the two types of diabetics. Glycemic control decreased GFR, whereas it did not alter RPF, resulting in normalization of FF in NIDDM and in IDDM. Before glycemic control, mean blood pressure was significantly correlated with GFR, but was not correlated after glycemic control in either type of diabetes. In conclusion, hyperglycemia induced glomerular hyperfiltration evenly and disturbed autoregulation of renal hemodynamics in NIDDM and in IDDM.

Adult↗
PubMedDate not supplied

Oral clonidine blunts the hemodynamic responses to brief but not prolonged laryngoscopy.

STUDY OBJECTIVE: To determine whether a 300 micrograms dose of oral clonidine given 90 minutes prior to laryngoscopy and intubation provides hemodynamic protection from the stress of a brief (15-second) and/or a prolonged (45-second) laryngoscopy. DESIGN: Randomized, double-blind, placebo-controlled study. SETTING: Inpatients and outpatients scheduled for general anesthesia with intubation at a university-affiliated medical center. PATIENTS: Forty patients who gave informed, written consent to receive either an oral placebo or clonidine 5 micrograms/kg (up to a maximum dose of 300 micrograms) 90 minutes prior to induction of anesthesia and to undergo either brief or prolonged laryngoscopy prior to intubation. INTERVENTIONS: The patients underwent a standardized induction sequence that included d-tubocurarine 3 mg, thiopental sodium 5 mg/kg, and succinylcholine 1.5 mg/kg. The four treatment groups (each n = 10) included (1) placebo with 15-second laryngoscopy, (2) placebo with 45-second laryngoscopy, (3) clonidine with 15-second laryngoscopy, and (4) clonidine with 45-second laryngoscopy. Heart rate (HR), systolic blood pressure (SBP), and diastolic blood pressure (DBP) were mechanically obtained and recorded at 1-minute intervals for 12 minutes. MEASUREMENTS AND MAIN RESULTS: There were no differences between groups in the premedication hemodynamic measurements. Within each group, maximal hemodynamic variables increased significantly over the corresponding baseline values for that group. In the 15-second, but not the 45-second, laryngoscopy, clonidine successfully blunted the maximum SBP and DBP obtained when compared with the corresponding control group. In both the 15- and 45-second clonidine groups, maximum HR was significantly lower than in the corresponding placebo groups. CONCLUSIONS: Oral clonidine, when used as a preoperative medication, affords hemodynamic protection to patients undergoing a 15-second laryngoscopy. However, the stress of a 45-second laryngoscopy may be too great or the 300 micrograms dose of clonidine too low to provide hemodynamic protection for patients in this group.

Administration, Oral↗
PubMed2006

A prospective study on esophageal Doppler hemodynamic assessment in the ED.

We sought to determine whether physicians' estimates of critically ill patients' hemodynamics are accurate as compared with esophageal Doppler probe (EDP) measurements and whether provision of measured hemodynamic profiles produces treatment changes and changes in physician confidence. At an urban county ED, we enrolled 55 critically ill adults with pulmonary edema of unclear etiology, sustained hypotension, or lactic acidosis. Physicians estimated cardiac output (CO) and systemic vascular resistance (SVR), categorized shock, stated treatment plans, and rated confidence in assessment and treatment plans. Physicians were informed of EDP hemodynamic measurements (CO, SVR, stroke volume, and contractility), and they repeated their assessments and plans. Weighted kappa values between physician estimates and EDP measurements of CO and SVR were 0.57 (95% confidence interval [CI] = 0.77-0.36) and 0.40 (95% CI = 0.64-0.16), respectively. Shock characterization changed in 52%, confidence increased significantly (pre-EDP mean = 3.3 +/- 0.9; post-EDP mean = 4.0 +/- 0.6; P = .0001), and stated treatment plans changed in 68% of the patients. Chart review demonstrated that similar proportions of control subjects had treatment changes, with a mean difference of 20% (95% CI = -2 to 42). Physician assessments of hemodynamic variables were moderately accurate. We conclude that EDP hemodynamic profiles change assessments and increase confidence in assessments but may not alter treatment.

Acidosis, Lactic↗
PubMed2005

Relation of high-sensitivity C-reactive protein level with coronary vasospastic angina pectoris in patients without hemodynamically significant coronary artery disease.

We prospectively investigated the relation of high-sensitivity C-reactive protein (hs-CRP) to coronary vasospasm and no hemodynamically significant coronary artery disease (CAD) in a sample of 428 patients who underwent coronary angiography. These patients were assigned to 1 of 3 groups. The control group consisted of 66 patients who had no coronary vasospasm and no hemodynamically significant CAD. The vasospasm group consisted of 116 patients who had coronary vasospasm and no hemodynamically significant CAD. The acute coronary syndrome (ACS) group consisted of 246 patients who had ACS and hemodynamically significant CAD. Serum hs-CRP was measured immediately before coronary angiography. Patients were followed for subsequent cardiac events and mortality. Median hs-CRP levels in the control, vasospasm, and ACS groups were 1.0, 5.5, and 8.2 mg/L, respectively. The proportion of hs-CRP increased from the lowest to the highest tertile in the control, vasospasm, and ACS groups, respectively. In the control and vasospasm groups, multivariate analysis showed that hs-CRP was independently associated with a diagnosis of coronary vasospastic angina pectoris (odds ratio 68.74, 95% confidence interval 8.03 to 588.71, p<0.001). During a median follow-up period of 26 months (range 0.4 to 48), 27 cardiac deaths occurred in the ACS group, whereas no cardiac death occurred in the control and vasospasm groups. In conclusion, serum hs-CRP level measured immediately before coronary angiography was an independent marker of coronary vasospasm in patients who had no hemodynamically significant CAD.

Aged↗
PubMed2006

Comparative hemodynamic effects of vasopressin and norepinephrine after milrinone-induced hypotension in off-pump coronary artery bypass surgical patients.

OBJECTIVE: Phosphodiesterase inhibitor is essential to the pharmacologic management of decompensated heart failure because it increases contractility and decreases afterload of right ventricle. It also improves hemodynamics and increases blood flow of the grafted internal mammary arteries and middle cerebral arteries during coronary artery bypass surgery. However, it induces vasodilation and necessitates the use of vasoconstrictors, such as norepinephrine. We hypothesized that vasopressin could recover hypotension induced by milrinone with less effect on pulmonary vascular resistance (PVR) compared to norepinephrine. METHODS: Fifty patients, undergoing coronary artery bypass graft (CABG) surgery, were assigned randomly in a double-blind manner to receive either vasopressin or norepinephrine. After baseline hemodynamic measurements, a loading dose of milrinone 50 microg/kg was infused slowly for 20 min followed by continuous infusion of 0.5 microg/(kg min). Immediately after the loading dose of milrinone, hemodynamic variables were measured, and vasopressin (VP group) or norepinephrine (NE groups) was infused. After being titrated until the mean arterial pressure was increased by 20%, hemodynamic variables were measured again. RESULTS: Milrinone infusion reduced both systemic vascular resistance (SVR, 1218+/-299 dynes/cm5 vs 838+/-209 dynes/cm5, 1345+/-299 dynes/cm5 vs 1011+/-195 dynes/cm5) and PVR (95+/-34 dynes/cm5 vs 72+/-30 dynes/cm5, 119+/-85 dynes/cm5 vs 87+/-33 dynes/cm5) in the VP and NE groups, respectively. Vasopressin and norepinephrine infusion increased both SVR (838+/-209 dynes/cm5 vs 1100+/-244 dynes/cm5, 1011+/-195 dynes/cm5 vs 1446+/-681 dynes/cm5, respectively) and PVR (72+/-30 dynes/cm5 vs 84+/-18 dynes/cm5, 87+/-33 dynes/cm5 vs 139+/-97 dynes/cm5, respectively). The PRV/SVR ratio was decreased after vasopressin infusion (0.10+/-0.03 vs 0.08+/-0.03), while no changes were found after norepinephrine infusion (0.09+/-0.02 vs 0.09+/-0.02). CONCLUSIONS: In the patients undergoing CABG surgery, both norepinephrine and low dose vasopressin were effective in restoring milrinone-induced decrease of SVR. However, only low-dose vasopressin decreased the PVR/SVR ratio that was increased by milrinone. Considering the importance of maintaining systemic perfusion pressure as well as reducing right heart afterload, milrinone-vasopressin may provide better hemodynamics than milrinone-norephinephrine during the management of right heart failure.

Aged↗
PubMed2005

Hemodynamic comparison of bioprostheses for complete supra-annular position in patients with small aortic annulus.

OBJECTIVES: The present study evaluates complete supra-annular bioprostheses in patients with an aortic annulus of 18 to 23 mm in diameter. BACKGROUND: Aortic valve replacement in patients with small aortic annulus using stented bioprostheses is often associated with unsatisfactory hemodynamic results and high incidence of patient-prosthesis mismatch. METHODS: Between February 2000 and January 2004, 156 patients with aortic valve disease and an aortic annulus of 18 to 23 mm in diameter received the stented bovine Soprano (Sorin Biomedica Cardio, Saluggia, Italy) (n = 18), Perimount (Edwards Lifesciences, Irvine, California) (n = 52), Perimount Magna (Edwards Lifesciences) (n = 42), or the stented porcine Mosaic (Medtronic Inc., Minneapolis, Minnesota) (n = 44) bioprostheses. Intraoperatively, the surgeon measured the aortic annulus diameter by inserting a hegar dilator. Thus, postoperative hemodynamic results could be referred to the patient's aortic annulus diameter instead of referring the results to the labeled valve size. This allows for objective comparisons between different valve types. RESULTS: There was no significant difference in hemodynamic results between the different valve types in patients with an aortic annulus 18 to 20 mm. In patients with an annulus 21 to 23 mm, the Magna was significantly superior to the other investigated devices in mean pressure gradient, effective orifice area, and incidence of patient-prosthesis mismatch. There was no significant difference between the complete supra-annular bioprostheses Mosaic and Soprano and the intra-supra-annular Perimount valve. CONCLUSIONS: In patients with an aortic annulus of 18 to 20 mm in diameter, hemodynamic performance is independent of the implanted stented valve type and the annular position. Root enlargement or stentless valves may be beneficial alternatives. Patients with annulus diameter 21 to 23 mm benefit from the Magna in complete supra-annular position leading to superior hemodynamic results.

Aged↗
PubMed2006

Rate, predictors, and consequences of hemodynamic depression after carotid artery stenting.

OBJECTIVES: We sought to determine the frequency, predictors, and consequences of hemodynamic depression (HD) after carotid artery stenting (CAS). BACKGROUND: Hemodynamic depression has been reported after carotid artery stenting CAS and carotid endarterectomy (CEA). METHODS: We retrospectively analyzed data on 500 consecutive CAS procedures performed over a 5-year period. Hemodynamic depression was defined as periprocedural hypotension (systolic blood pressure <90 mm Hg) or bradycardia (heart rate <60 beats/s). Univariate and multivariate binary logistic regression models were used to determine the predictors and consequences of HD and persistent HD. RESULTS: The mean age of the patients was 70.5 +/- 10 years, and 69% were men. Hemodynamic depression occurred during 210 procedures (42%), whereas persistent HD developed in 84 procedures (17%). Features that independently predicted HD included lesions involving the carotid bulb (odds ratio [OR] 2.18 [range 1.46 to 3.26], p < 0.0001) or the presence of a calcified plaque (OR 1.89 [range 1.25 to 2.84], p < 0.002). Prior ipsilateral CEA was associated with reduced risk of HD (OR 0.35 [range 0.20 to 0.60], p < 0.0001). Patients who developed persistent HD were at a significantly increased risk of a periprocedural major adverse clinical event (OR 3.05 [range 1.35 to 5.23], p < 0.02) or stroke (OR 3.34 [range 1.13 to 9.90], p < 0.03). CONCLUSIONS: Hemodynamic depression is common after CAS, particularly in patients with a calcified plaque in the carotid bulb, but is easily treated with conventional methods. Patients who develop persistent HD are at an increased risk of periprocedural major adverse clinical events and stroke.

Aged↗
PubMed2006

Hemodynamic patterns of blunt and penetrating injuries.

BACKGROUND: The aims of this prospective observational study were to describe early hemodynamic patterns of blunt and penetrating truncal injury and to evaluate outcomes prediction using noninvasive hemodynamic monitoring with a mathematical model tested against actual in-hospital outcomes. The hypothesis was that traumatic shock is a circulatory disorder that can be monitored by noninvasive hemodynamic parameters that reflect cardiac, pulmonary, and tissue perfusion functions. STUDY DESIGN: The cardiac index (CI), heart rate (HR), mean arterial pressure (MAP), pulse oximetry (SapO(2)), transcutaneous oxygen tension indexed to FiO(2) (PtcO(2)/FiO(2)), and carbon dioxide (PtcCO(2)) tensions were monitored beginning shortly after emergency department admission in 657 emergency patients with severe blunt and penetrating chest, abdominal, and extremity trauma. Of these, 113 patients had associated head injury, and these patients also were analyzed separately. A search and display mathematical model, with a decision support program, was based on continuous online, real-time, noninvasive hemodynamic monitoring. RESULTS: There were similar patterns in the blunt and penetrating injuries; the cardiac index, mean arterial pressure, pulse oximetry, transcutaneous oxygen tension indexed to FiO(2), and survival probability values of the survivors were significantly higher (p < 0.01) than the corresponding values of those who died, although heart rate and carbon dioxide tension were higher in the nonsurvivors during the first 24 hours after their emergency department admission. These patterns occurred more rapidly in patients with penetrating injuries. After initial resuscitation in the emergency department, results were correlated with actual outcomes at hospital discharge and found to be 88% correct. CONCLUSIONS: Early noninvasive hemodynamic monitoring with a computerized information system provided a feasible pattern recognition program for outcomes prediction and therapeutic decision support.

Adult↗
PubMed2006

Oscillatory cerebral hemodynamics--the macro- vs. microvascular level.

The phase shift between oscillations of blood pressure (BP) and Doppler middle cerebral artery flow velocity (MCAFV) reflects continuous cerebral autoregulatory action. It is not known whether a similar phase shift exists for cortical hemodynamics ('microvascular level') assessed by near infrared spectroscopy (NIRS) and what the effects are of pathological conditions. This study investigates the phase relations between oscillations of BP, MCAFV and NIRS parameters in 38 healthy older adults and 28 patients with unilateral severe obstructive carotid disease. BP was recorded noninvasively by finger plethysmography. Stable 0.1 Hz oscillations of all hemodynamic parameters were induced by regular breathing at a rate of 6/min. Basic results were that: (1) BP-induced cortical microvascular oscillations (NIRS) follow those of macrovascular oscillations (MCAFV) with a phase of 80-90 degrees (corresponding to 2-2.5 s at 0.1 Hz), most likely reflecting a transit time phenomenon; (2) oxy- and deoxyhemoglobin thereby oscillate in counterphase; (3) hemodynamic compromise in carotid obstruction leads to (a) delayed NIRS oscillations in comparison to BP which are highly correlated to a shorter phase lead of MCAFV against BP and (b) a decoupling of the oxy-/deoxyhemoglobin counterphase to 240 degrees . Cortical hemodynamic responses to BP oscillations follow specific phase relationships due to cerebral autoregulatory action and circulatory transit times. With hemodynamic impairment, as in unilateral carotid obstruction, these phases are significantly changed reflecting disturbed autoregulation.

Aged↗
PubMed2007

Hemodynamic effects of partial ventricular support in chronic heart failure: results of simulation validated with in vivo data.

OBJECTIVE: Current left ventricular assist devices are designed to provide full hemodynamic support for patients with end-stage failing hearts, but their use has been limited by operative risks, low reliability, and device-related morbidity. Such concerns have resulted in minimum use of left ventricular assist devices for destination therapy. We hypothesize that partial circulatory support, which could be achieved with small pumps implanted with less-invasive procedures, might expand the role of circulatory support devices for treatment of heart failure. METHODS: We examine the hemodynamic effects of partial left ventricular support using a previously described computational model of the cardiovascular system. Results from simulations were validated by comparison with an in vivo hemodynamic study. RESULTS: Simulations demonstrated that partial support (2-3 L/min) increased total cardiac output (left ventricular assist device output plus native heart output) by more than 1 L/min and decreased left ventricular end-diastolic pressure by 7 to 10 mm Hg with moderate-to-severe heart failure. Analyses showed that the hemodynamic benefits of increased cardiac output and decreased left ventricular end-diastolic pressure are greater in less-dilated and less-dysfunctional hearts. Both the relationships between ventricular assist device flow and cardiac output and ventricular assist device flow and left atrial pressure predicted by the model closely approximated the same relationships obtained during hemodynamic study in a bovine heart failure model. CONCLUSIONS: Results suggest that a pump with a flow rate of 2 to 3 L/min could meaningfully affect cardiac output and blood pressure in patients with advanced compensated heart failure. The development of small devices capable of high reliability and minimal complications that can be implanted with less-invasive techniques is supported by these findings.

Animals↗
PubMed1994

A positive intracavernous injection test implies normal veno-occlusive but not necessarily normal arterial function: a hemodynamic study.

During impotence evaluations a positive intracavernous injection test has been presumed to signify normal erectile hemodynamics. This premise was tested by obtaining hemodynamic data in 80 patients 17 to 65 years old with positive injection tests: patients achieved maximal circumference responses and equilibrium intracavernous pressures of 80 mmHg or more (range 80 to 136) sustained for 30 minutes or longer. Corporeal veno-occlusive testing revealed that flow-to-maintain (0.5 to 3 ml. per minute) and pressure decay (0 to 47 mmHg) values as well as pharmaco-cavernosography findings (absent or minimal contrast medium in venous structures in 92% of the cases) were all consistent with low outflow erection states. Arterial testing revealed right and/or left cavernous systolic arterial blood pressures always at 80 mmHg or more, consistent with a prerequisite cavernous artery pressure value for a positive injection test. Systemic-cavernous systolic arterial blood pressure gradients were 0 to 24 mmHg, 25 to 34 mmHg and 35 mmHg or more in 47 (59%), 18 (22%) and 15 (19%) patients, respectively. Large systemic-cavernous pressure gradients suggested the presence of arterial occlusive disease. In 8 patients with positive injection tests and gradients of 35 mmHg or more pharmaco-arteriography revealed hemodynamically significant arterial occlusions. In conclusion, hemodynamic data in selected patients with positive injection tests revealed low outflow erection states, threshold cavernous artery pressures and disparities in systemic-cavernous systolic pressure gradients that suggested arterial disease in 19% of the cases. The erectile response in a positive test is equal to or greater than a threshold response, not always the maximum response as determined by the systemic blood pressure. A positive intracavernous injection test did not necessarily signify normal erectile hemodynamics.

Adolescent↗
PubMed1997

Hemodynamic impact of vein graft stenoses and their prediction in the vascular laboratory.

PURPOSE: We undertook this prospective evaluation to define the direct hemodynamic impact of vein graft stenoses and to correlate intraoperative hemodynamic findings with the preoperative duplex scan. METHODS: Twelve consecutive isolated vein graft stenoses were identified in the vascular laboratory during our routine duplex scanning surveillance protocol over 10 months. Peak systolic flow velocity ratios (PSFVRs; velocity within stenosis/velocity proximal to the stenosis) at the stenoses ranged from 2.7 to 10 (mean, 5.5), and ankle-brachial indexes ranged from 0.47 to 0.94 (mean, 0.68) Preoperative arteriograms were obtained and confirmed the isolated stenoses, which radiographically ranged from 20% to 83% diameter reduction (mean, 64%). At the time of surgery the stenotic graft segment was isolated, and simultaneous pressure measurements proximal and distal to the graft stenosis were measured, along with ultrasound transit-time blood flow measurements. Pressure and flow wave forms were recorded for 10 seconds at 200 Hz and were stored on a personal computer-based digital acquisition system. The graft stenoses were then repaired with either a vein patch or short interposition graft, and the hemodynamic measurements were repeated. Fourier transformation of the pressure and flow curves was performed, and the resistance and longitudinal impedance were calculated for each graft segment. RESULTS: Before repair, mean pressure gradients across the stenotic graft segments (delta P) ranged from 1.0 to 74.6 mm Hg (mean, 20.4 mm Hg), and vein graft flow ranged from 4.9 to 140 ml/min (mean, 45.2 ml/min). After repair of the stenotic segments, the mean pressure gradient was decreased to a mean of 1.3 mm Hg, and vein graft flow increased to a mean of 104.8 ml/min. The PSFVR recorded in the vascular laboratory correlated significantly with delta P (r = 0.71; p = 0.01) and allowed prediction of delta P as: delta P = 7.4 (PSFVR) - 19.8. PSFVR also correlated with measured resistance across the stenosis (r = 0.79; p = 0.004). Conversely, the angiographic measurement of stenosis did not correlate significantly with these parameters. The angiographic measurement of stenosis showed a moderate correlation with the PSFVR (r = 0.58; p = 0.046). CONCLUSIONS: The PSFVR, as measured in the laboratory, is an accurate and useful indicator of the hemodynamic impact of vein graft stenosis. Revision of stenotic vein graft segments resulted in a significant improvement in graft hemodynamics.

Blood Flow Velocity↗
PubMed1998

Hemodynamic instability following carotid endarterectomy does not affect early discharge.

Over the last few years, there has been increased emphasis on early discharge of patients following carotid endarterectomy in the United States. Recent studies have shown that short-stay hospitalization for carotid endarterectomy may be safe and cost-effective. However, this is not always possible because of reasons that are not clearly delineated. In order to optimize the early discharge of patients following carotid endarterectomy, an analysis of the causes of delayed discharges was performed in the present series. Since hemodynamic instability has been shown to be the most frequent complication following carotid endarterectomy, the authors investigated whether it was an important factor preventing early postoperative discharge. This study reviewed the data of 100 consecutive patients admitted for elective carotid endarterectomy. The incidence of post-carotid endarterectomy hemodynamic instability was 37% (n = 37), with hypertension occurring in 25 patients (68%) and hypotension occurring in 12 patients (32%). Hemodynamic instability tended to occur with the use of general anesthesia as compared with regional anesthesia. Hemodynamic instability did not correlate with pre-existent history of hypertension, nor with the type of drug used when general anesthesia was applied. All the patients were successfully treated either in the recovery room or in a monitored area. The average total length of stay was 1.65 days with 79% of the patients being discharged on the first postoperative day and 21% having delayed discharge ranging from 2 to 15 days (mean 4 days). The main reasons for delayed discharges were cardiac and urinary tract complications. Blood pressure instability accounted for only 2% of cases. Thus, these data show that hemodynamic instability does not significantly affect early discharge.

Aged↗