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At least 217 records · Page 12Linked to original sources
PubMed1998

Effects of the prone position on gas exchange and hemodynamics in severe acute respiratory distress syndrome.

OBJECTIVES: To address the following issues regarding the use of prone position ventilation in patients with severe acute respiratory distress syndrome (ARDS): a) response rate; b) magnitude and duration of improved oxygenation in responders during a 12-hr trial and the consequences of returning to the supine position; c) effects of the prone position on gas exchange and hemodynamics; d) consequences of oxygenation in nonresponders; and e) effects of repeated prone position trials. DESIGN: Prospective, nonrandomized interventional study. SETTING: Medical intensive care unit, university tertiary care center. PATIENTS: Nineteen consecutive, mechanically ventilated patients (age 45+/-20 yrs, mean+/-SD) with ARDS and severe hypoxemia, defined as PaO2/FiO2 of < or = 150 with FiO2 of > or = 0.6 persisting for < or =24 hrs, and a pulmonary artery occlusion pressure of <18 mm Hg. INTERVENTIONS: Patients were turned prone for 2 hrs. Nonresponders were returned supine, but responders were maintained prone for 12 hrs before being returned to the supine position. The procedure was repeated on a daily basis in all patients, until inclusion criteria were no longer met or the patients died. MEASUREMENTS AND MAIN RESULTS: Hemodynamic, blood gas, and gas exchange measurements were performed at the following time points: a) baseline supine; b) after 30 mins prone; and c) after 120 mins prone. Additional measurements for nonresponders were taken after 30 mins supine. For responders, additional measurements were taken after 12 hrs prone and 30 mins supine. Patients were considered responders if an increase in PaO2 of > or = 10 torr (> or =1.3 kPa), or increase in the PaO2/FiO2 ratio of >20 occurred within 120 mins. Eleven (57%) patients responded to the prone position. There was no difference in initial baseline parameters between responders and nonresponders. After 30 mins, the prone position in responders increased PaO2 and decreased calculated venous admixture (Qva/Qt). This improvement was the maximal obtained, and was maintained throughout the 12-hr prone period. After 12 hrs prone, mean FiO2 had been lowered from 0.85+/-0.16 to 0.66+/-0.18 (p < .05). Thirty minutes after the patients were returned supine, PaO2, PaO2/FiO2, and Qva/Qt were not different from 12-hr prone values, and were improved in comparison with baseline supine values. There was no worsening of gas exchange or hemodynamics in nonresponders. After the initial trial, a total of 28 additional episodes of prone position ventilation were performed in nine of the 19 patients. Of the 24 additional episodes in the responders, there was a response in 17 (71%) of 24 episodes. In the four additional episodes in nonresponders, there was a response in only one (25%) of four episodes. Response was accompanied by the same beneficial effects on gas exchange and Qva/Qt and absence of effect on hemodynamics as in the initial trial. There was no worsening in gas exchange or hemodynamics in nonresponder trials. CONCLUSIONS: Based on the data from this study, the prone position can improve oxygenation in severely hypoxemic ARDS patients without deleterious effects on hemodynamics. This beneficial effect does not immediately disappear on return to the supine position. In our patients, an absence of response to this technique was not accompanied by worsening hypoxemia or hemodynamic instability. Repeated daily trials in the prone position should be considered in the management of ARDS patients with severe hypoxemia.

Adolescent↗
PubMed1998

Early hemodynamic variations assessed by an echo-Doppler aortic blood flow device in a severely burned infant: correlation with the circulating cytokines.

We describe the case of a seriously burned infant who suffered from a deep burn covering approximately 30% of his total body surface area. Because invasive hemodynamic monitoring is usually not suggested in infants, hemodynamic profile can be misunderstood. We tested a new echo-Doppler device to determine hemodynamic variation using a small esophageal probe specifically designed for newborns and infants. The aortic flowmeter was connected with satellite devices to obtain the hemodynamic profile, including aortic blood flow (ABF), preejection period, left ventricular ejection time, mean arterial pressure, heart rate, calculated stroke volume, calculated total systemic vascular resistance (TSVR), and end-tidal CO2 pressure. The positioning of the probe was easily obtained at each time. The hemodynamic management initially exhibited a hypovolemic status followed by a hyperdynamic profile, as suggested by a gradually increased ABF, which seemed similar to the variations currently reported in adult burn patients. Concurrent with hemodynamic determinations, plasma samples were drawn to measure interleukin-6 (IL-6), interleukin-1beta(IL-1beta), and tumor necrosis factor-alpha(TNF-alpha)levels. A consistent peak of IL-6 occurred simultaneously with the drop in TSVR. In contrast, no marked modifications were observed with IL-1beta and TNF-alpha. The same circulating cytokines moved alike in burned adults; IL-6 could partly explain the mechanisms of hemodynamic variation through the systemic inflammatory response syndrome. On the other hand, the echo-Doppler device could provide valuable noninvasive findings, allowing early improvement in resuscitation during the acute phase of critically burned infants and children.

Adult↗
PubMed2000

Successful hepatic grafting after partial portal vein ligation in the rat: complete reversal of hemodynamic abnormalities.

BACKGROUND: Partial portal vein ligation (PPVL) is an established approach in the study of prehepatic portal hypertension in animals. The effect of orthotopic liver transplants (OLT) on hemodynamics in PPVL animals has not been investigated to date. The aim of this study was to develop a model of OLT in PPVL rats and to investigate its hemodynamic consequences. METHODS: Three groups of male Lewis rats were investigated (1) control animals (n=7), (2) PPVL (n=9), and (3) PPVL/OLT (n=16). Three weeks after PPVL, 9 animals were taken for hemodynamic measurements. OLT was performed in the remaining 16 PPVL rats (PPVL/OLT), and, 4 weeks later, hemodynamic measurements were made. Blood biochemical analysis was performed at different time points in all 3 groups. RESULTS: The PPVL animals presented with hyperdynamic systemic circulation, extensive collateral vascularization in the hilar region, and portal-systemic shunting (portal systemic shunting; 35.3+/-5.5%). In the PPVL/OLT group, 15 rats survived for 4 weeks (survival: 93.8%, 15 of 16). Of these PPVL/OLT rats, 3 died during the blood sampling protocol. In 3 PPVL/OLT rats, abnormal liver function and histology were found and deranged systemic and hepatic hemodynamics persisted after OLT. In the remaining 9 PPVL/OLT rats, systemic and hepatic hemodynamics had returned to normal at 4 weeks and portal systemic shunting was markedly reduced (2.5+/-0.9%). Liver function was in the normal range. CONCLUSIONS: (1) The possibility of performing OLT in PPVL rats with a high rate of survival has been confirmed. (2) In the majority of cases, complete reversal of hemodynamic abnormalities in the PPVL animals occurs after OLT (3). PPVL/OLT represents a new and important model in OLT research.

Animals↗
PubMed2005

Development of implantable devices for continuous ambulatory monitoring of central hemodynamic values in heart failure patients.

BACKGROUND: Care and management of patients with congestive heart failure (CHF) is a major health-care challenge. The value of acute hemodynamic data in assessing heart failure has been questioned in some studies, while more intensive hemodynamic monitoring has been reported to improve patient care in others. A series of patient studies are reported here that were conducted to identify device requirements and verify the feasibility of continuous hemodynamic monitoring in CHF patients and devices for remote transfer and use of these data. METHODS AND RESULTS: The results of four separate studies in 68 CHF patients who received systems for chronic hemodynamic monitoring between 1992 and the present are reviewed. One early study was with five patients followed for 7-16 months and another study was with nine patients followed for 4-22 months. A third study included 21 patients followed up to 39 months, and the fourth study included 32 patients implanted in 1998-99 with many of them still in follow-up. These studies support the technical feasibility of implanted devices and the external instrumentation required to transfer and manage the collected data. They also support the long-term stability and accuracy of these systems. Three additional acute studies conducted with 30 patients and chronic data from 53 of the 68 patients with the implanted systems are presented that support the feature included in the newer monitors--the ability to reliably estimate pulmonary artery diastolic pressures from the right ventricular pressure signal. CONCLUSIONS: Development of implantable technology to measure several hemodynamic variables in ambulatory CHF patients is feasible. External instrumentation needed to remotely acquire data from the implanted devices has been verified. The potential to eliminate the uncertainties associated with the use of acute, invasive hemodynamics and the ability to evaluate long-term ambulatory hemodynamic patterns is provided. These findings set the stage for determining the potential clinical value of these systems in impacting the care of chronic CHF patients.

Electrocardiography, Ambulatory↗
PubMed1987

Splanchnic and renal hemodynamic responses to intraportal infusion of glucagon.

We compared the 60-min splanchnic and renal hemodynamic responses to intraportal (IPV) and intravenous infusion of glucagon (5 ng.kg-1.min-1) in anesthetized dogs and quantitated the importance of glucose in mediating the renal hemodynamic responses to intraportal infusion of glucagon. Intraportal glucagon elevated superior mesenteric (SMA) and renal (RA) artery blood flows by 8 and 16%, respectively, by minute 15. By minute 30, RA flow had increased by 23%. Thereafter, SMA flow returned to control, while RA flow remained elevated by 24%. Glomerular filtration rate (GFR) followed the same pattern as RA flow over 60 min. Intravenous glucagon elicited smaller hemodynamic responses. During intraportal and intravenous glucagon infusion, plasma glucose rose by 20-25%. Renal hemodynamics were not affected by incremental changes in blood glucose of up to 6.25 mmol/l. At an incremental change in glucose of 10.06 mmol/l, RA flow and GFR were elevated by 12 and 9%, respectively. We conclude that intraportal glucagon infusion increases splanchnic and renal hemodynamics, although the splanchnic response is evanescent. Importantly, hepatic release of glucose into the circulation during intraportal glucagon infusion does not have a significant effect on renal hemodynamics. Thus, similar to intravenous infusion of the hormone, renal hemodynamic responses to intraportal glucagon are independent of and dissociated from elevations in blood glucose produced during hormone infusion.

Animals↗
PubMed1985

Hemodynamic changes mimicking a vasodilator drug response in the absence of drug therapy after right heart catheterization in patients with chronic heart failure.

We suspected that patients with severe chronic heart failure may show hemodynamic changes after cardiac catheterization in the absence of drug therapy that could complicate assessment of the hemodynamic effects of new vasodilator and inotropic agents. To evaluate this phenomenon prospectively, hemodynamic variables were measured in 21 patients with heart failure 30 min and 2, 6, 24, and (in 12 patients) 48 hr after right heart catheterization, during which time therapy was not altered. During the first 2 hr we noted a significant increase in cardiac index and decreases in left ventricular filling pressure, mean arterial pressure, mean right atrial pressure, and systemic vascular resistance (p less than .01); a further decline in left ventricular filling pressure was noted over the next 24 hr, after which all hemodynamic variables remained stable. The magnitude of these hemodynamic changes resembled the effects of many established vasodilator drugs and was further enhanced after meals. These data indicate that hemodynamic improvement may be observed without any therapeutic intervention during the course of invasive studies in patients with severe chronic heart failure; such changes may lead investigators to attribute efficacy to ineffective drug therapy. To minimize the occurrence of such responses, we recommend that intravascular catheters be inserted the day before drug evaluation and that hemodynamic measurements be made with patients in a postprandial state.

Adult↗
PubMed1997

Sustained hemodynamic efficacy of therapy tailored to reduce filling pressures in survivors with advanced heart failure.

BACKGROUND: During therapy to relieve congestion in advanced heart failure, cardiac filling pressures can frequently be reduced to near-normal levels with improved cardiac output. It is not known whether the early hemodynamic improvement and drug response can be maintained long term. METHODS AND RESULTS: After referral for cardiac transplantation with initially severe hemodynamic decompensation, 25 patients survived without transplantation to undergo hemodynamic reassessment after 8+/-6 months of treatment tailored to early hemodynamic response. Initial changes included net diuresis, increased ACE inhibitor doses, and frequent addition of nitrates. After 8 months of therapy, early reductions were sustained for pulmonary wedge pressure (24+/-9 to 15+/-5 mm Hg early; 12+/-6 mm Hg late) and systemic vascular resistance (1651+/-369 to 1207+/-281 dynes x s(-1) x cm(-5) early; 1003+/-193 dynes x s(-1) x cm(-5) late). Acute response to doses persisted at reevaluation. Sustained reduction in filling pressures was accompanied by a progressive increase in stroke volume (42+/-10 to 56+/-13 mL early; 79+/-20 mL late), improved functional class, and freedom from resting symptoms. Study design did not control for amiodarone, which was initiated for arrhythmias in 12 patients and associated with greater improvement in cardiac index (1.8 to 3.2 L min(-1) x m(-2) late on amiodarone versus 2.0 to 2.6 L x min(-1) x m(-2), P<.05). CONCLUSIONS: During chronic therapy tailored to early hemodynamic response in advanced heart failure, acute vasodilator response persists, and near-normal filling pressures can be maintained in patients who survive without transplantation. Stroke volumes at low filling pressures increase further over time. Chronic hemodynamic improvement was accompanied by symptomatic improvement, but the contributions of the monitored hemodynamic approach, increased vasodilator doses, and comprehensive outpatient management have not yet been established.

Amiodarone↗
PubMed1995

Arterial hemodynamics in human hypertension. Effects of the calcium channel antagonist nifedipine.

Previous studies have shown some distinct hemodynamic alterations in essential hypertension, including increased resistance, wave reflections, and pulse wave velocity and decreased arterial compliance. These abnormalities are completely normalized by nonspecific smooth muscle dilation with nitroprusside but not by combined alpha- and beta-adrenergic blockade or angiotensin-converting enzyme inhibition, suggesting an enhanced smooth muscle tone that cannot be attributed solely to the sympathetic nervous or renin-angiotensin systems. Since hypertensive patients have an enhanced calcium influx-dependent vasoconstriction, we performed the present study to examine the extent to which the dihydropyridine calcium channel antagonist nifedipine could normalize the hemodynamic abnormalities in essential hypertension. An essential hypertensive patient group was compared with a normotensive group similar in age, body size, and proportion of men and women. During diagnostic cardiac catheterization, ascending aortic micromanometer pressures and electromagnetic flows were measured at baseline and after sufficient sublingual nifedipine (mean, 24 mg) to normalize blood pressure. From the pressures and flows, aortic input impedance, wave reflection magnitude, and compliance were computed. In the hypertensive group, the hemodynamic alterations were indistinguishable from those summarized above. Nifedipine produced sufficient vasodilation to completely normalize all of these hemodynamic alterations, including wave reflections. From these results, together with those reported in our previous studies, it is clear that the various classes of antihypertensive agents affect hemodynamics differently. All are capable of decreasing blood pressure to normotensive levels, but only nitroprusside and nifedipine can also completely normalize all the other pulsatile hemodynamic alterations. Thus, these hemodynamic effects of the different classes of antihypertensive agents should be considered in choosing a therapeutic modality.

Adult↗
PubMed1998

YM872, a highly water-soluble AMPA receptor antagonist, preserves the hemodynamic penumbra and reduces brain injury after permanent focal ischemia in rats.

BACKGROUND AND PURPOSE: We recently described an image analysis technique based on the temporal correlation mapping (TCM) of injected contrast agents that can be used to distinguish the hemodynamic core and hemodynamic penumbra after focal ischemia. In this study we used this technique for the first time to investigate the effects of the water-soluble AMPA receptor antagonist YM872 in permanent focal ischemia. METHODS: Fischer 344 rats were subjected to permanent occlusion of the middle cerebral artery. Approximately 30 minutes after ischemia, functional CT images were collected with the use of a dynamic scanning protocol with bolus injections of nonionic contrast agent iohexol (1 mL/kg). TCM analysis defined the distributions of hemodynamic core and hemodynamic penumbra. Cerebral perfusion indices were calculated on the basis of the area under the first-pass transit curves. One hour after ischemia, animals were randomly treated with YM872 (n=8, 20 mg/kg per hour over 4 hours) or normal saline (n=10). Twenty-four hours later, neurological deficits were evaluated, and conventional CT and triphenyltetrazolium chloride staining were used to define volumes of ischemic damage. RESULTS: At 24 hours after ischemia, hypodense lesions were visible on conventional CT scans that were highly correlated with triphenyltetrazolium chloride lesion volumes. YM872 improved neurological deficits and reduced volumes of ischemic damage in cortex (90+/-14 versus 170+/-16 mm3 in controls) but not striatum (57+/-14 versus 79+/-6 mm3 in controls). Comparison of early TCM images with conventional CT scans of ischemic injury showed that the hemodynamic core was always damaged in all rats. In controls, 54% of the tissue within the hemodynamic penumbra evolved into ischemic damage compared with 24% in YM872-treated rats. Furthermore, the perfusion index corresponding to the ischemic damage threshold was significantly reduced by YM872 (28+/-2% versus 37+/-2% in controls). CONCLUSIONS: These results indicate that YM872 is a neuroprotective compound that ameliorates the deterioration of the hemodynamic penumbra after focal ischemia.

Animals↗
PubMed1999

Frequency and determinants of postprocedural hemodynamic instability after carotid angioplasty and stenting.

BACKGROUND AND PURPOSE: Hemodynamic instability can occur acutely after carotid angioplasty and stent placement (CAS). We performed this study to determine the frequency of hemodynamic instability in a series of patients who underwent CAS and to analyze factors associated with development of postprocedural hemodynamic events. METHODS: We reviewed medical records and angiograms in a series of 51 patients (mean age 68.3+/-8.9 years) who underwent CAS for symptomatic (n=29) or asymptomatic (n=22) carotid artery stenosis. Any episodes of hypotension (systolic blood pressure <90 mm Hg), hypertension (systolic blood pressure >160 mm Hg), or bradycardia (heart rate <60 bpm) that occurred in the acute postprocedural period were recorded. The effect of demographic, clinical, intraprocedural, and angiographic factors on subsequent development of hemodynamic instability was analyzed by logistic regression. RESULTS: The frequency of postprocedural hemodynamic complications in our patient series was as follows: hypotension, 22.4%; hypertension, 38.8%; and bradycardia, 27.5%. Intraprocedural hypotension (odds ratio [OR] 14.6, P=0.024) and history of myocardial infarction (OR 14.1, P=0.04) independently predicted postprocedural hypotension. Postprocedural hypertension was predicted by intraprocedural hypertension (OR 7.6, P=0.01) and previous ipsilateral carotid endarterectomy (OR 7.6, P=0.02). Postprocedural bradycardia was associated with intraprocedural hypotension (OR 74, P=0.001) and intraprocedural bradycardia (OR 12, P=0.008). All events had resolved at the conclusion of the intensive care unit monitoring period (mean 25.7 hours, range 18 to 43 hours). CONCLUSIONS: Postprocedural hemodynamic instability is frequent after CAS and supports the need for monitoring in settings suited to expeditious management of cardiovascular emergencies. Patients who have evidence of hemodynamic instability during the procedure are at highest risk.

Aged↗
PubMed2005

Continuous aortic flow augmentation: a pilot study of hemodynamic and renal responses to a novel percutaneous intervention in decompensated heart failure.

BACKGROUND: Diminished aortic flow may induce adverse downstream vascular and renal signals. Investigations in a heart failure animal model have shown that continuous aortic flow augmentation (CAFA) achieves hemodynamic improvement and ventricular unloading, which suggests a novel therapeutic approach to patients with heart failure exacerbation that is inadequately responsive to medical therapy. METHODS AND RESULTS: We studied 24 patients (12 in Europe and 12 in the United States) with heart failure exacerbation and persistent hemodynamic derangement despite intravenous diuretic and inotropic and/or vasodilator treatment. CAFA (mean+/-SD 1.34+/-0.12 L/min) was achieved through percutaneous (n=19) or surgical (n=5) insertion of the Cancion system, which consists of inflow and outflow cannulas and a magnetically levitated and driven centrifugal pump. Hemodynamic improvement was observed within 1 hour. Systemic vascular resistance decreased from 1413+/-453 to 1136+/-381 dyne.s.cm(-5) at 72 hours (P=0.0008). Pulmonary capillary wedge pressure decreased from 28.5+/-4.9 to 19.8+/-7.0 mm Hg (P<0.0001), and cardiac index (excluding augmented aortic flow) increased from 1.97+/-0.44 to 2.27+/-0.43 L.min(-1).m(-2) (P=0.0013). Serum creatinine trended downward during treatment (overall P=0.095). There were 8 complications during treatment, 7 of which were self-limited. Hemodynamics remained improved 24 hours after CAFA discontinuation. CONCLUSIONS: In patients with heart failure and persistent hemodynamic derangement despite intravenous inotropic and/or vasodilator therapy, CAFA improved hemodynamics, with a reduction in serum creatinine. CAFA represents a promising, novel mode of treatment for patients who are inadequately responsive to medical therapy. The clinical impact of the observed hemodynamic improvement is currently being explored in a prospective, randomized, controlled trial.

Adult↗
PubMed1979

Vectorcardiographic detection of early hemodynamic abnormalities in chronic obstructive pulmonary disease.

The ability of the vectorcardiogram to detect mild circulatory abnormalities in patients with chronic obstructive pulmonary disease (COPD) is unclear. Therefore, vectorcardiographic changes were correlated with hemodynamic measurements made at rest and during supine exercise in 32 patients with COPD and no clinical or electrocardiographic evidence of right ventricular hypertrophy. Twelve patients had normal hemodynamic data (group 1), nine had abnormal hemodynamic data only during exercise (group 2), and 11 had abnormal hemodynamic data at rest and during exercise (group 3). The extent of rightward terminal QRS forces noted on the vectorcardiogram was significantly less in group 1 (5.5 +/- 8.7 percent) than in either group 2 (19.0 +/- 10.7 percent) or group 3 (17.8 +/- 14.8 percent). Sixty-five percent (13) of the 20 patients with hemodynamic abnormalities had rightward terminal QRS forces of 15 percent or more, whereas only 8 percent (one) of the 12 patients with normal hemodynamic data had such forces of 15 percent or more. The mean of the rightward terminal QRS forces in 27 age-matched normal subjects was 5.0 +/- 5.4 percent, and only one subject had forces of 15 percent or more. We conclude that hemodynamic abnormalities are frequent in patients with COPD and no clinical evidence of right ventricular hypertrophy and that the vectorcardiogram provides an indirect method of detecting these abnormalities.

Adult↗
PubMed2004

Relationship of hemodynamic indices and prognosis in patients with liver cirrhosis.

BACKGROUND: Hyperdynamic circulation due to reduced peripheral vascular resistance and increased cardiac output, and the development of portal hypertension are the hemodynamic changes observed in patients with liver cirrhosis. Such hemodynamic abnormalities appear in patients with late stage liver cirrhosis. Therefore, hemodynamic indices, which represent hyperdynamic circulation and portal hypertension, are significant for the prognosis of patients with liver cirrhosis. The aim of this study was to determine the hemodynamic indices associated with the prognosis of patients with liver cirrhosis. METHODS: A total of 103 patients diagnosed with liver cirrhosis between December 1999 and June 2003, with a mean follow-up period of 73 weeks, ranging from 7 to 168 weeks, were recruited. Using Child-Pugh classification, the mean arterial pressure, heart rate and hepatic venous pressure gradient (HVPG) were measured. The indices of Doppler ultrasonography, including the portal and splenic venous flows, and the resistance of the hepatic, splenic, and renal arteries were also measured using the arterial pulsatility index (PI). The prognostic values of these indices were determined by their comparison with the patient survivals. RESULTS: Significant hemodynamic indices for a bad prognosis were high HVPG (> or = 15 mmHg) and renal arterial PI (> or = 1.14)(p<0.05). A Child-Pugh score > or = 10 was important for a poor prognosis (p<0.05). CONCLUSION: Severe portal hypertension (HVPG > or = 15 mmHg) and high renal arterial resistance (PI +/- 1.14) were valuable hemodynamic indices for the prognosis of patients with liver cirrhosis. Therefore, it was concluded that the measurement of these hemodynamic indices, in addition to the Child-Pugh classification, is helpful in the prognosis of patients with liver cirrhosis.

Female↗
PubMed2005

[With-time change of hemodynamics in fMRI: linearity consideration after stimulation ends from stimulation beginning].

The BOLD signal responses that occur after a few seconds at the beginning and the end of stimulus are due to hemodynamic delay. A temporary increase of deoxyhemoglobin just after the beginning of stimulus causes an initial dip in the hemodynamic signal (response). After the initial dip, an increase of BOLD signal causes an overshoot. After the overshoot, a decrease of the BOLD signal due to the end of stimulus causes an undershoot. Many reports have examined the period of stimulus, but only a few have described the period after stimulus. This paper reports on a peak between the overshoot and undershoot. After the end of stimulus, the signal does not simply decrease, but shows a peak after some delay. An activated map showed the same tendency as the hemodynamics signal. This peak was termed hemodynamic over-saturation (HOS). Time control in chronological order is important to obtain a hemodynamic change in chronological order and a large, significant difference between the task and rest signal. The entire hemodynamic signal was evaluated by controlling the timing of the scan using an external trigger and by indicating the beginning of the task (rest) period using sound. The timing of the external trigger and sound are built into the sequence design as a program. From the results of the hemodynamic signal, the causal relationship between this signal and the fluctuation in oxyhemoglobin and deoxyhemoglobin can be considered.

Adult↗
PubMed1989

Hemodynamic validation of Doppler assessment of fetoplacental circulation in a sheep model system.

Several clinical studies suggest that the Doppler indices (DI) derived from Doppler waveform analysis may be powerful predictors of perinatal compromise. In contrast, significant paucity exists in experimental verification of the central premise that the DI reliably reflect hemodynamic state downstream from the measurement point. This paper presents the results from two sets of acute animal experiments in which experimentally induced changes in the ovine fetoplacental circulation as reflected by the independently measured hemodynamic parameters were correlated with the corresponding variations in the DI. Doppler velocimetric measurements were performed under general anesthesia in ovine fetuses with gestational ages ranging from 100 to 110 days. A continuous wave Doppler instrument with a 4-MHz transducer was used. In three fetuses, variable vascular constriction was produced by a ligature placed approximately 10 cm from the probe location. In four fetuses, vasopressin was rapidly infused. The hemodynamic parameters measured included the peripheral resistance, volumetric flow, and pressure. The DI included the systolic-diastolic ratio, pulsatility index, and resistance index. The results indicate that, in hemodynamically stable and well-defined obstruction to downstream flow as achieved in the constriction experiments, the DI highly correlated with the hemodynamic state (p less than .005); however, during the more complex and unstable circulatory changes associated with vasopressin administration, these correlations were inconsistent and poor (p greater than .05). This study experimentally establishes in an in vivo animal system the hemodynamic validity of the DI within certain limits. However, the validity does not extend to hemodynamic changes associated with vasopressin administration. Further studies are required to address this issue.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1999

Hemodynamic and biochemical effects of 100% oxygen breathing in humans.

High concentrations of inspired oxygen have been reported to have significant hemodynamic effects that may be related to increased free radical production. If oxygen therapy increases free radical production, it may also modify hemodynamic responses to a nitric oxide donor. Twenty-nine healthy male volunteers were studied using randomized, double-blind, placebo-controlled, crossover designs to determine whether oxygen therapy is associated with hemodynamic and forearm vascular effects. We measured hemodynamic parameters and forearm vascular responses before and 1 h after exposure to 100% oxygen versus medical air. Plasma 8-iso-PGF2alpha and plasma vitamin C were measured to assess the biochemical effects of oxygen administration. Hemodynamic measurements were also made following the acute administration of sublingual nitroglycerin. Oxygen therapy caused no significant change in blood pressure, plasma 8-iso-PGF2alpha, or vitamin C. Oxygen did cause a significant reduction in heart rate and forearm blood flow, and an increase in peripheral vascular resistance. Oxygen caused no change in the hemodynamic response to nitroglycerin. Therefore, in healthy young adults, therapy with 100% oxygen does not affect blood pressure, despite causing an increase in vascular resistance, is not associated with evidence of increased free radical injury, and does not affect the hemodynamic responses to nitroglycerin.

Adult↗
PubMedDate not supplied

[Comparison of preoperative and postoperative hemodynamic parameters in replacement or reconstruction of the mitral valve in ischemic dilated cardiomyopathy].

INTRODUCTION: Ischemic mitral insufficiency is a clinical syndrome described as a consequence of the coronary artery disease where the basic problem is blood regurgitation between the left ventricle and left atrium following mitral annulus dilatation. Mitral regurgitation occurs in different degrees during the natural evolution of the ischemic heart disease. The main reason for the existence of mitral regurgitation is global deterioration in the left ventricle geometry as a consequence of myocardial infarction or/and left ventricle dilatation. Surgical correction of this problem is possible by simultaneous correction of mitral insufficiency (repair or replacement) and complete myocardial revascularisation. MATERIAL AND METHODS: Complete hemodynamic monitoring was followed by Swan-Ganz catheter including: central venous pressure, mean pulmonary artery pressure, pulmonary capillary wedge pressure, cardiac output, cardiac index and pulmonary vascular resistance. All surgical procedures were performed in extracorporeal circulation (ECC) with membrane oxygenator using moderate systemic hypothermia and transseptal surgical approach to mitral valve. Hemodynamic parameters were followed before and after ECC, immediately after surgery and during the first 48 hours after operation in the intensive care unit. In 88 patients posterior semicircular annuloplasty by N. Radovanović was performed whereas in 13 patients mitral valve replacement was done. RESULTS: There is a great, statistically significant hemodynamic improvement after the surgical procedure and during the continuous 48 hours monitoring in the intensive care unit no matter if mitral repair or replacement was done. No statistically significant difference was recorded between these two groups considering that the hemodynamic improvement is very similar. DISCUSSION: Simultaneous surgical procedures, including myocardial revascularization, mitral and usually consecutive tricuspid insufficiency correction, are a very common surgical problem with higher operative risk than isolated coronary bypass procedures. In 88 cases where mitral reconstruction was possible, posterior semicircular reductive annuloplasty was performed. Thus mitral annulus area reduction is achieved preserving its physiologic shape and avoiding rigidity. Mitral valve replacement includes implantation of the latest generation of bileaflet valve prosthesis and operative technique that preserves subvalvular apparatus to maintain myocardial contractility as much as possible. This policy and also good immediate postoperative care, improve the hemodynamic status in both groups. CONCLUSION: All hemodynamic parameters followed by ECC and 48 hours in the intensive care unit were significantly improved no matter whether mitral reconstruction or replacement was done. There is no statistically significant difference in hemodynamic parameters and clinical improvement between these two groups. Carefully chosen operative tactic and techniques as well as good preoperative and postoperative care may explain these very good results.

Cardiomyopathy, Dilated↗
PubMed2002

Cardiac positioning using an apical suction device maintains beating heart hemodynamics.

BACKGROUND: Cardiac positioning during off-pump coronary artery bypass (OPCAB) using deep pericardial sutures (DPS) typically results in some degree of hemodynamic compromise. We sought to determine whether cardiac positioning using an apical suction device was hemodynamically superior to DPS. METHODS: Five healthy pigs underwent sternotomy and instrumentation to measure right atrial (RA) pressure, left ventricular (LV) pressure and volume, and aortic pressure and flow. These variables were recorded at baseline, with simple attachment of the apical suction device (Xpose Access Device, Guidant, Inc.), and during exposure of the posterior descending artery (PDA) and obtuse marginal (OM) branches of the left circumflex artery using DPS and the apical suction device. RESULTS: Application of the apical suction device to the beating heart in neutral anatomic position did not result in any statistically significant change in hemodynamics compared to baseline except for a small decrease in RA pressure. DPS positioning resulted in statistically significant compromise in nearly all measured hemodynamic parameters, including cardiac output (-21% PDA, -30% OM), mean arterial pressure (-18% PDA, -26% OM), and stroke work (-31% PDA, -38% OM). In addition, LV end-diastolic pressure decreased (-59% PDA, -51% OM) while RA pressure increased (+17% PDA, +16% OM). Similar target exposure using the apical suction device resulted in near-baseline hemodynamics. The only statistically significant changes were a modest decrease in cardiac output (-18% OM) and RA pressure (-11% PDA). CONCLUSION: DPS positioning significantly compromises hemodynamics due to reduced LV filling. The apical suction device provides good exposure with less hemodynamic compromise.

Animals↗