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PubMed2000

Analysis of hemodynamic changes during beating heart surgical procedures.

BACKGROUND: Coronary artery bypass grafting on the beating heart causes significant hemodynamic compromise during displacement of the heart. The precise mechanisms causing altered hemodynamics have not been clearly understood. The purpose of this study was to define the hemodynamic changes caused by displacing the heart in patients undergoing beating heart surgical procedures. METHODS: Forty-four patients (35 men, 9 women; mean age, 64.5 +/- 9.6 years) underwent off-pump coronary artery bypass grafting. The hemodynamic variables were collected before and after positioning the heart for anastomosis of the left anterior descending, circumflex, and posterior descending coronary arteries. RESULTS: There was a significant increase in right ventricular end-diastolic pressure during positioning for all vessels, and in left ventricular end-diastolic pressure during positioning for the left anterior descending and circumflex coronary arteries. Positioning for the circumflex artery showed the largest increase of left and right ventricular end-diastolic pressure, resulting in the greatest hemodynamic compromise. CONCLUSIONS: In the clinical setting of diseased human hearts, there is a biventricular contribution to altered hemodynamics. The increase of right ventricular end-diastolic pressure in all positions suggests that the major cause of hemodynamic changes is disturbed diastolic filling of the right ventricle, especially by direct ventricular compression.

Aged↗
PubMed1996

Hemodynamic significance of pediatric femur fractures.

PURPOSE: To determine whether hemodynamically significant bleeding occurs after pediatric femur fractures. METHOD: A retrospective chart review was performed; demographic and injury data were collected for all patients with the diagnosis of femur fracture over a 30-month period at a level/ pediatric trauma center. Included were patients with multisystem injury and patients with femur fractures as the only injury. The incidence of hemodynamic insufficiency, the reasons for and timing of transfusions, and the changes in hematocrit levels over time were evaluated. RESULTS: One hundred seventy-eight children were identified (182 femur fractures). There were 116 boys and 62 girls, and the mean age was 6.04 +/- 4.5 years (range, 1 month to 19 years). The mechanisms of injury included falls (46), pedestrian/ motor vehicle accidents (43), motor vehicle crashes (19), sports accidents (22), abuse (10), and miscellaneous (38). The mean Injury Severity Score (ISS) was 5.88 +/- 3.93 (range, 4 to 29). There were no deaths. The length of hospital stay was 8.13 +/- 9.37 days (range, 1 to 43 days). Prehospital treatment included early immobilization. Fracture treatment was according to recognized orthopedic techniques based on age, size, and fracture configuration. The mean hematocrit in the emergency department was 34% +/- 3.5% (range, 27.8% to 44.4%) and 32% +/- 6.6% (range, 16.9% to 47.8%) at 24 hours. 67 patients (38%) suffered multiple injuries. Mean ISS for this group was 9.4 +/- 5.0 (range, 5 to 29). Four patients had hemodynamic insufficiency at the time of admission. All were in the multiple-injury group Seven of these 67 patients (10%) required transfusion-three in the first 24 hours (two in the emergency department [associated with severe facial/scalp bleeding] and one in the operating room [associated with severe liver injury]) and four after the first 24 hours (three associated with intraoperative orthopedic procedures and one with a hemothorax). The mean age of those who underwent transfusion was 8.29 +/- 4.79 years, and their mean ISS was 13.71 +/- 4.61. All patients who required transfusion had been injured in motor vehicle crashes or in pedestrian/motor vehicle accidents. One hundred eleven children had isolated closed femur fractures. No patient in this group had evidence of hemodynamic insufficiency or required transfusion. The initial mean hematocrit was 34.5% +/- 2.7%, and the mean 24-hour hematocrit was 34.6% +/- 3.2%. We found that (1) no child with an isolated closed femur fracture had evidence of hemodynamic instability, or showed significant blood loss as evidenced by a decreasing hematocrit at 24 hours, and (2) in this series, evidence of hemodynamic insufficiency and/or the need for transfusion was found only in multiply injured children. CONCLUSION: Hemodynamic instability or evidence of a declining hematocrit in the child should not be attributed to a closed femur fracture and that other sources of blood loss must be found.

Anemia↗
PubMedDate not supplied

Assessment of human ocular hemodynamics.

Vascular abnormality and altered hemodynamics play important roles in many ophthalmic pathologies. Much of our knowledge of ocular hemodynamics was gained from invasive animal research, although a number of noninvasive methods suitable for in vivo use in humans have been developed. Data from these methods now produce a significant literature of their own. Understanding the origins of the data and appreciating their limitations can be difficult. Modern hemodynamic assessment techniques each examine a unique facet of the ocular circulation. No single facet provides a complete description of the hemodynamic state of the eye. These methods have contributed a great deal to our understanding of normal hemodynamics. More importantly, they continue to add to our understanding of altered hemodynamics found in disease. Some have found their way into limited clinical practice. The predominant ocular hemodynamic assessment techniques are reviewed with the aims of introducing the fundamental principles behind each, highlighting their inherent advantages and limitations, highlighting their contributions to understanding ocular physiology, and considering their potential to provide signs for diagnosis.

Animals↗
PubMed2002

Asymmetric hemodynamic responses of the human auditory cortex to monaural and binaural stimulation.

Applying whole-head functional magnetic resonance imaging (fMRI) in 11 neurologically intact subjects, hemodynamic responses to mon- or binaurally presented auditory stimuli were measured. To expand on previous studies in this research area, we used tones and consonant-vowel (CV) syllables. In one group of subjects (n=6) the perceived loudness of the monaurally presented stimuli were adjusted so that they matched the loudness of the binaurally presented stimuli. In a second group (n=5) no loudness adjustment was performed, thus the monaural stimuli were perceived less loud ( approximately 10 dB) than the binaural stimuli. These extensions allowed us to test whether CV syllables and tones produce different contralaterality effects (stronger hemodynamic responses in the auditory cortex contralateral to the stimulated ear) and whether binaural stimulation results in stronger activations in the auditory areas than during both monaural stimulation conditions (binaural summation) independent of loudness influences. In summary, we obtained the following findings: (1) strong contralaterality effects during monaural acoustic stimulation in the posterior superior temporal gyrus (STG) comprising the planum temporale and the dorsal bank of the superior temporal sulcus to CV syllables and tones; (2) the hemodynamic responses to contralaterally presented stimuli (during the monaural conditions) were mostly stronger than those to binaurally presented CV syllables; (3) there was no interaction between stimulus type and the size of the contralaterality effect; (4) there was no indication of binaural summation, rather we found stronger hemodynamic responses to the sum of both monaural stimulations (right and left ear) than to binaural stimulation in all auditory areas; (5) there were generally stronger hemodynamic responses to CV syllables than to tones in the posterior STG, while the hemodynamic responses to tones were stronger in the anterior part of the STG (temporal pole); and finally (6) there was no general difference in terms of hemodynamic response in the auditory cortex between the two groups when receiving either loudness-matched or non-loudness-matched monaural stimulation. These findings are discussed in the context of the underlying neurophysiological mechanisms, the peculiarities of functional fMRI, and the direct access and callosal relay models of hemispheric lateralization.

Acoustic Stimulation↗
PubMed1987

Pharmacokinetic-hemodynamic studies of transdermal nitroglycerin in congestive heart failure.

Ten patients with chronic congestive heart failure were studied to assess the hemodynamic effects and bioavailability of a transdermal nitroglycerin delivery system. Nitrate sensitivity was defined by a prior 20 minute infusion of nitroglycerin, 21 micrograms/min. Five patients with a satisfactory hemodynamic response to intravenous nitroglycerin received two nitroglycerin patches of 10 cm2 each and five patients who did not achieve a satisfactory response to intravenous nitroglycerin (that is, greater than or equal to 25% reduction in left ventricular filling pressure) received larger doses of transdermal nitroglycerin. In the five nitrate-sensitive patients who received 20 cm2 of transdermal nitroglycerin, one study was terminated at 90 minutes, at which point there was no detectable hemodynamic response or arterial plasma nitroglycerin evident. Two patients had a minimal hemodynamic response and a peak plasma concentration of 1 ng/ml. A fourth patient had a short-lived hemodynamic response at 60 and 120 minutes and a plasma nitroglycerin concentration of 1 ng/ml at 60 minutes. A fifth patient had a hemodynamic response persisting for 24 hours and plasma concentrations between 0.6 and 1.1 ng/ml. The remaining five patients showed little or no hemodynamic response despite doses of transdermal nitroglycerin from 40 to 60 cm2. The highest plasma concentration achieved in these patients was 2 ng/ml and there was no relation between dose administered and plasma concentration achieved. In 4 of the 10 patients who subsequently received nitroglycerin ointment, there were a greater decrease in left- and right-sided filling pressures and greater increase in plasma nitroglycerin concentrations (from 1.6 to 4.8 ng/ml) than those that occurred with transdermal nitroglycerin.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Cutaneous↗
PubMed1998

Hemodynamic changes induced by laparoscopy and their endocrine correlates: effects of clonidine.

OBJECTIVES: We investigated endocrine correlates of the hemodynamic changes induced by carbon dioxide pneumoperitoneum (PNO). We then studied whether clonidine might modulate the hemodynamic changes induced by PNO by reducing release of catecholamines and vasopressin. BACKGROUND: Both mechanical and neurohumoral factors contribute to the hemodynamic changes induced by carbon dioxide PNO. Several mediators have been proposed, but no study has correlated hemodynamic changes with changes in levels of these potential mediators. METHODS: We conducted two studies, each including 20 healthy patients scheduled for elective laparoscopic cholecystectomy. In the first study serial measurements of hemodynamics (thermodilution technique) were done during laparoscopy and after exsufflation. Plasma concentrations of cortisol, catecholamines, vasopressin, renin, endothelin and prostaglandins were measured at the same time points. In the second study patients were randomly allocated to receive 8 microg/kg clonidine infused over 1 h or placebo before PNO. Hemodynamics and plasma levels of cortisol, catecholamines and vasopressin were measured during PNO and after exsufflation. RESULTS: Peritoneal insufflation resulted in a significant reduction of cardiac output (18+/-4%) and increases in mean arterial pressure (39+/-8%) and systemic (70+/-12%) and pulmonary (98+/-18%) vascular resistances. Laparoscopy resulted in progressive and significant increases in plasma concentrations of cortisol, epinephrine, norepinephrine and renin. Vasopressin plasma concentrations markedly increased immediately after the beginning of PNO (before PNO 6+/-4 pg/ml; during PNO 129+/-42 pg/ml; p < 0.05). The profile of vasopressin release paralleled the time course of changes in systemic vascular resistance. Prostaglandins and endothelin did not change significantly. Clonidine significantly reduced mean arterial pressure, heart rate and the increase in systemic vascular resistance. Clonidine also significantly reduced catecholamine concentrations but did not alter vasopressin and cortisol plasma concentrations. CONCLUSIONS: Vasopressin and catecholamines probably mediate the increase in systemic vascular resistance observed during PNO. Clonidine before PNO reduces catecholamine release and attenuates hemodynamic changes during laparoscopy.

Adrenergic alpha-Agonists↗
PubMed2003

Computational analysis of effects of external carotid artery flow and occlusion on adverse carotid bifurcation hemodynamics.

OBJECTIVE: This is a computational analysis of the effects of external carotid artery (ECA) flow, waveform, and occlusion geometry on two hemodynamic wall parameters associated with intimal hyperplasia and atherosclerosis. Study design Transient three-dimensional fluid mechanics analysis was applied to a standard carotid artery bifurcation. Mean internal carotid artery (ICA) flow was maintained at 236 mL/min with a normal waveform. ECA flow was increased from zero to 151 mL/min (64% of ICA flow) with both a normal biphasic waveform and a damped waveform. Geometry of five ECA occlusions was studied: distal, proximal stump, smooth, smooth without carotid sinus, and optimal reconstruction.Primary outcome measures Two time-averaged and area-averaged hemodynamic wall parameters were computed from the velocity and wall shear stress (WSS) solutions, ie, wall shear stress angle gradient (WSSAG) and oscillatory shear index (OSI). Both local and area-averaged hemodynamic wall parameters were computed for the distal common carotid artery (CCA) and the proximal ICA. RESULTS: When ECA flow with a normal waveform is increased from zero to 151 mL/min, area-averaged WSS values increase in the CCA, from 3.0 to 4.4 dynes/cm(2) (46%), and in the ICA, from 16.5 to 17.1 dynes/cm(2) (4%); minimum local WSS values in the carotid sinus remain less than 1 dyne/cm(2); maximum local values of WSSAG and OSI are observed in the carotid sinus and increase from 3.5 to 9.1 radian/cm (160%) and 0.23 to 0.46 (100%), respectively; CCA plus ICA area-averaged WSSAG increases by 52%, and OSI increases by 144%; and damping of the ECA waveform has little effect on local or area-averaged WSSAG but reduces OSI to 68%. When the ECA is occluded, the minimum local WSS in the carotid sinus is less than 1 dyne/cm(2). However, if the carotid sinus is removed or the CCA-ICA geometry hemodynamically optimized, the minimum WSS is approximately 4 dynes/cm(2). Similarly, eliminating the carotid sinus markedly reduces local maximum WSSAG, from 3.0-3.5 radian/cm to 0.3 radian/cm, and reduces local maximum OSI from 0.22-0.49 to 0.04. Area-averaged WSSAG and OSI over the CCA and ICA are reduced by approximately 50% with elimination of the carotid sinus. CONCLUSIONS: The degree of adverse carotid bifurcation hemodynamics as measured with WSSAG and OSI is directly proportional to ECA flow. The marked difference in normal ICA and ECA flow waveforms does not contribute to adverse wall hemodynamics. Location of an ECA occlusion (distal, proximal, stump, smooth) does not affect adverse carotid hemodynamics; however, marked improvement is obtained with elimination of the carotid sinus.

Arteriosclerosis↗
PubMed1998

Hemodynamics of human carotid artery bifurcations: computational studies with models reconstructed from magnetic resonance imaging of normal subjects.

PURPOSE: The precise role played by hemodynamics, particularly wall shear stress, in the development and progression of vascular disease remains unclear, in large part because of a lack of in vivo studies with humans. Although technical challenges remain for noninvasively imaging wall shear stresses in humans, vascular anatomy can be imaged with sufficiently high resolution to allow reconstruction of three-dimensional models for computational hemodynamic studies. In this paper we present an entirely noninvasive magnetic resonance imaging (MRI) protocol that provides carotid bifurcation geometry and flow rates from which the in vivo hemodynamics can be computed. Maps of average, oscillatory, and gradients of wall shear stress are presented for two normal human subjects, and their data are compared with those computed for an idealized carotid bifurcation model. METHODS: An MRI protocol was developed to acquire all necessary image data in scan times suitable for patient studies. Three-dimensional models of the carotid bifurcation lumen were reconstructed from serial black blood MR images of two normal volunteers. Common and internal carotid artery flow rate waveforms were determined from MRI phase-contrast velocity imaging in the same subjects and were used to impose fully developed velocity boundary conditions for the computational model. Subject-specific time-resolved velocities and wall shear stresses were then computed with a finite element-based Navier-Stokes equation solver. RESULTS: Models reconstructed from in vivo MRI of two subjects showed obvious differences in branch angle, bulb size and extent, and three-dimensional curvature. Maps of a variety of wall shear stress indices showed obvious qualitative differences in patterns between the in vivo models and between the in vivo models and the idealized model. Secondary, helical flow patterns, induced primarily by the asymmetric and curved in vivo geometries, were found to play a key role in determining the resulting wall shear stress patterns. The use of in vivo flow rate waveforms was found to play a minor but noticeable role in some of the wall shear stress behavior observed. CONCLUSIONS: Conventional "averaged" carotid bifurcation models mask interesting hemodynamic features observed in realistic models derived from noninvasive imaging of normal human subjects. Observation of intersubject variations in the in vivo wall shear stress patterns supports the notion that more conclusive evidence regarding the role of hemodynamics in vascular disease may be derived from such individual studies. The techniques presented here, when combined with subject-specific MRI measurements of carotid artery plaque thickness and composition, provide the tools necessary for entirely noninvasive, prospective, in vivo human studies of hemodynamics and the relationship of hemodynamics to vascular disease.

Adult↗
PubMed2002

Hemodynamic and plasma atrial natriuretic peptide responses to acute digitalis therapy in patients with normal and impaired left ventricular function.

BACKGROUND: Digitalis has a long history in the treatment of heart failure but its effects on cardiac hemodynamics and neurohormonal modulation are not well characterized. AIMS: The purpose of this study was to evaluate the relationship between atrial natriuretic peptide (ANP) and the hemodynamic responses to acute digitalis administration in patients with normal and impaired left ventricular function (LVD). METHODS AND RESULTS: Thirty patients were enrolled in the study, 20 with LVD (LVEF=22+/-8%) and 10 control subjects (LVEF=77+/-10%). Hemodynamics and plasma ANP concentrations were measured supine and with leg elevation before and after digitalis. In patients with normal ventricular function, the hemodynamic stress of leg elevation in the pre-digitalis state resulted in significant (P<0.05) increases in PAWP and MPAP. Digitalis administration in the supine position produced reductions in heart rate, PAWP, MPAP and CI; SVR was increased. In LVD patients leg elevation further increased PAWP, RAP and MPAP. Digitalis in the supine position, however, reduced RAP, MPAP and PAWP and increased CI. These improved hemodynamics were preserved during the stress of leg elevation. Leg elevation following digitalis resulted in increased ANP concentrations despite decreased cardiac filling pressures. CONCLUSIONS: Acute digitalis administration results in hemodynamic improvement in LVD patients which may in part result from digitalis stimulated release of myocardial ANP under conditions of hemodynamic stress.

Adult↗
PubMed1999

The role of Ca2+ and hemodynamics in the action of diltiazem on hepatic energy metabolism.

Diltiazem causes vasoconstriction in the liver when present at high concentrations, an action that is strictly Ca2+-dependent. Diltiazem is also active on energy metabolism. This toxic action could be partly a consequence of hemodynamic effects. In the absence of Ca2+, the hemodynamic effects are no longer present and, consequently, Ca2+-free experiments are useful for distinguishing between hemodynamics-dependent and hemodynamics-independent effects. The experimental system used was the hemoglobin-free perfused rat liver from fed and fasted rats. Diltiazem was infused at various concentrations in the presence and absence of Ca2+. Several metabolic parameters were measured: lactate and pyruvate production (glycolysis), glycogenolysis, oxygen uptake, gluconeogenesis, and the cellular levels of lactate, pyruvate, glucose, AMP, ADP, and ATP. The effects of diltiazem can be divided into three groups: (1) Effects that are strictly dependent on the Ca2+-mediated hemodynamic action. This group comprises inhibition of oxygen uptake at all concentrations (50-500 micromol/L) inhibition of lactate, pyruvate, and glucose release at high concentrations; the decrease in cellular ATP; the increase in cellular AMP; and the cellular accumulation of glucose and lactate. (2) Effects that are independent of the hemodynamic action. The most relevant effect of this type is inhibition of gluconeogenesis. (3) Effects that are influenced by Ca2+ but are independent of the hemodynamic effects. This is the typical case of lactate and glucose release from endogenous glycogen, whose stimulation by low diltiazem concentrations is more pronounced in the presence of Ca2+ than in its absence.

Adenine Nucleotides↗
PubMed2001

Hemodynamics as surrogate end points for survival in advanced heart failure: an analysis from FIRST.

BACKGROUND: Hemodynamics often are used as surrogate end points in phase II trials of acute heart failure (HF). We reviewed the Flolan International Randomized Survival Trial (FIRST) database to identify the hemodynamic variables that best predict survival in patients with advanced HF receiving epoprostenol therapy and to determine whether hemodynamics could predict the overall effect of a drug. METHODS: The trial enrolled 471 patients with class IIIb/IV HF and ejection fraction or=3 months, all of whom underwent screening pulmonary artery catheter insertion. Patients were randomly assigned to receive either epoprostenol (n = 201) or placebo (n = 235); epoprostenol therapy was guided by pulmonary artery catheter measures, and standard treatment was guided by clinical findings. Multivariable modeling was used to identify and quantify the demographic, clinical, and hemodynamic variables most associated with 1-year survival. RESULTS: In multivariable modeling, HF class, decreased pulmonary capillary wedge pressure (PCWP), and age best predicted 1-year survival. After adjustment for age and HF class, decreased PCWP still significantly predicted survival (hazard ratio, 0.96 for every 1-mm Hg decrease; 95% confidence interval, 0.94 to 0.99; P = .003). Survival was significantly higher with decreases in PCWP >or=9 versus <9 mm Hg, even after adjustment for age and HF class. Survival of patients in the PCWP >or=9 group was comparable with, and that of the PCWP <9 group was significantly higher than, survival of patients in the control group (hazard ratio, 1.44; 95% confidence interval, 1.05 to 1.99; P = .024). CONCLUSIONS: The reduction in PCWP was the hemodynamic measure most predictive of survival in patients with advanced HF. However, patients with a >or=9-mm Hg decrease had no better survival than patients in the control group, who had limited changes in hemodynamics. Thus, improvement in hemodynamics may not predict the overall effect of a drug.

Aged↗
PubMed2003

Effect of elastic compression stockings on venous hemodynamics during walking.

PURPOSE: Venous hemodynamics evaluated during walking better reflect changes that occur under active physiologic conditions than do conventional static modes of exercise such as tip-toe exercise, knee bending, or dorsiflexion. We prospectively studied the efficacy of air-plethysmography (APG) in monitoring venous hemodynamics during ambulation, and with this method we determined the hemodynamic effects of graduated elastic compression stockings on the lower limb during walking at various speeds. METHODS: The residual volume fraction (RVF%) during treadmill walking was monitored with APG in 10 limbs with primary chronic venous insufficiency (CVI)(CEAP(2-4)) at four speeds (1.0, 1.5, 2.0 and 2.5 km/h consecutively), with and without elastic compression (21 mm Hg at the ankle). The method was validated in comparison with standard APG, which is based on tip-toe exercise. RVF obtained during treadmill walking at 1.5 km/h was correlated with RVF measured with standard APG in 30 subjects: 12 healthy volunteers, 11 patients with primary CVI, and 7 postthrombotic limbs. Data were analyzed with nonparametric statistics. RESULTS: RVF measurements during walking were reproduced with an intra-day coefficient of variation of 5.1% to 16.5%. RVF during walking correlated well with RVF during standard APG (tip-toe) (r = 0.5, P =.004). At each of the investigated walking speeds, stockings improved venous hemodynamics by decreasing RVF, from a median of 50.5% without stockings to 40.5% with stockings at 1.0 km/h (19.8% decrease), from 49% to 39.5% at 1.5 km/h (19.4% decrease), from 50.5% to 41% at 2.0 km/h (18.8% decrease), and from 53% to 45.5% at 2.5 km/h (14.2% decrease) (all speeds, P <.02). Efficacy of the stockings in decreasing RVF (percent change in RVF) was similar across the spectrum of examined speeds (P =.47). During walking with elastic stockings, nominal RVF values were also similar across the spectrum of walking speeds, except at 2.5 km/h (P =.012). During walking without stockings, RVF did not change with treadmill speed, nor did it differ from that obtained with conventional APG (tip-toe) (P =.46). The percentage decrease in RVF generated with elastic stockings correlated with the venous filling index (r = 0.73, P =.017) at 1.0 km/h. CONCLUSIONS: APG is a reproducible and valid method for monitoring venous hemodynamics during walking. Graduated elastic compression stockings significantly improved venous hemodynamics by reducing RVF in limbs with primary CVI at all examined walking speeds (1.0 to 2.5 km/h). The effect was linearly correlated with the amount of reflux (1.0 km/h). The modified application of APG during walking offers a new noninvasive method for assessment of venous hemodynamics in limbs with CVI, enabling quantification of the actual effect of elastic compression therapy during ambulation.

Adult↗
PubMed1996

Hemodynamic alterations in focal cerebral ischemia: temporal correlation analysis for functional imaging.

We describe a novel approach for analysing the hemodynamic alterations that result after focal cerebral ischemia. This approach utilizes a temporal correlation analysis of first pass transit data obtained with functional imaging. First pass transits of injected contrast agents are measured with dynamic CT scanning. Normal transit profiles are obtained from contralateral cortical regions to serve as reference profiles. Normalized correlations are then calculated to compare transit profiles from each individual pixel within the brain to the normal reference profile. The normalized correlation coefficient is used as a measure of temporal similarity to quantitatively assess deviations from normal hemodynamics. The method is based on the premise that perturbed hemodynamics are manifested as changes in the shape of the cerebral transit profiles. Correlation maps are produced that display regional alterations in cerebral hemodynamics. Results from rabbit (n=4) and rat (n=4) models of focal ischemia are presented. In the normal contralateral hemisphere, correlation values range from 0.83-0.93 with coefficients of variation of less than 3-4% . The ischemic core is comprised of regions without significant bolus transit. The peripheral zones that lie between normal brain and the ischemic core are composed of intermediate correlation values. By setting statistical thresholds (mean minus 2SD, p < 0.05), we quantitatively define these intermediate zones as the hemodynamic penumbra, i.e. regions where the shape of the first pass transit profile has been altered. The resulting correlation maps clearly image gradients of altered cerebral hemodynamics. Perfusion indices calculated based on transit profile peaks revealed that the penumbral zones possess reduced perfusion on the order of about 40 percent of contralateral values. In summary, we believe that temporal correlation analysis of first pass transit profiles can be used to image the hemodynamic penumbra in focal cerebral ischemia.

Animals↗
PubMed1999

Similar central hemodynamics in salt-sensitive and salt-resistant hypertensive patients.

Salt may be involved in the pathogenesis of essential hypertension but no agreement has been reached on how salt might exert its blood pressure control. One reason for the conflicting results could be differences in response to changes in salt intake--i.e. between salt-sensitive and salt-resistant subjects. Hypertension reflects a hemodynamic disturbance: mainly an increase in total peripheral resistance. In order to determine whether central hemodynamics is different in salt-sensitive and salt-resistant essential hypertension, a study was carried out on 37 patients aged 31-63 years with mean casual blood pressure 165/104 mmHg. Based on an increase in ambulatory 24-h mean blood pressure of > or = 10% after one week of dietary salt loading (260 mmol NaCl/24 h) following a one-week salt depletion period (60 mmol NaCl/24 h), 7 patients (19%) were classified as salt sensitive and 30 patients (81%) as salt resistant. Before the salt-sensitivity test, while patients were on their habitual salt intake (160 mmol NaCl/24 h), central hemodynamics (intra-arterial pressure, cardiac output by dye dilution, heart rate by electrocardiogram, and total peripheral resistance) was examined at rest and during bicycle exercise. None of the central hemodynamic variables were different between the two groups, despite a marked difference in blood pressure response to one week of salt loading between the salt-sensitive and the salt-resistant groups (27/9 mmHg vs -2/1 mmHg). Furthermore, no statistically significant differences were observed in neurohumoral variables or echocardiographic indices of left ventricular dimensions between the two groups. Owing to the invasive hemodynamic procedure, central hemodynamics was not restudied during high- or low salt intake. It is concluded that there is no difference in central hemodynamics in salt-sensitive and salt-resistant hypertensive patients when they are on their habitual salt diet.

Adult↗
PubMed2003

Target-controlled infusion for remifentanil in vascular patients improves hemodynamics and decreases remifentanil requirement.

UNLABELLED: Remifentanil is a potent ultra-short-acting opioid, which permits rapid emergence. However, remifentanil is expensive and may have detrimental effects on hemodynamics in case of overdose. Target-controlled infusion (TCI) permits adapting infusion to pharmacokinetic models. In this prospective randomized study, we compared intra- and postoperative hemodynamics, remifentanil requirement during anesthesia, and postoperative morphine requirement in patients scheduled for carotid surgery, and receiving either continuous IV weight-adjusted infusion of remifentanil (RIVA) or TCI for remifentanil (TCIR). Forty-six patients were enrolled in this study: all were anesthetized by using TCI for propofol. Twenty-three received RIVA (0.5 micro g. kg(-1) x min(-1)) for the induction of anesthesia and endotracheal intubation, with the infusion rate decreased to 0.25 micro g x kg(-1) x min(-1) after intubation, then adapted by step of 0.05 micro g x kg(-1) x min(-1) according to hemodynamics. Twenty-three patients received TCIR (Minto model, Rugloop), with an effect-site concentration at 4 ng/mL during induction, then adapted by step of 1 ng/mL according to hemodynamics. All patients received atracurium and a 50% mixture of N(2)O/O(2). Hemodynamic variables were recorded each minute. The number and duration of hemodynamic events were collected, and total doses of anesthetics (remifentanil and propofol) and vasoactive drugs were noted in both groups of patients. Data were analyzed by using unpaired t-tests. RIVA was significantly associated with more frequent episodes of intraoperative hypotension (16 versus 6, P < 0.001) and more frequent episodes of postoperative hypertension and/or tachycardia requiring more frequent administration of beta-adrenergic blockers (16 vs 10, P < 0.04) in comparison with TCIR. The need for morphine titration was not significantly different between groups. TCIR led to a significantly smaller requirement of remifentanil (700 +/- 290 versus 1390 +/- 555 micro g, P < 0.001) without difference in propofol requirement. This prospective randomized study demonstrated that, during carotid endarterectomy, in comparison with patients receiving remifentanil using continuous RIVA, TCI results in less hypotensive episodes during the induction of anesthesia, in fewer episodes of tachycardia and/or hypertension and a smaller beta-adrenergic blocker requirement during recovery, and a decrease in remifentanil requirement. Recommendations to prefer TCI for remifentanil administration during carotid endarterectomy may be justified. IMPLICATIONS: Remifentanil for intraoperative analgesia in carotid artery surgery is associated with a better stability in perioperative hemodynamics when administered in target-controlled infusion compared with continuous weight-adjusted infusion. This may be related to a smaller requirement of this drug when using target-controlled infusion, as well as a smooth mode of administration.

Adrenergic beta-Antagonists↗
PubMed1996

Cardiovascular responses during sedation after coronary revascularization. Incidence of myocardial ischemia and hemodynamic episodes with propofol versus midazolam. Institutions of the McSPI Research Group.

BACKGROUND: Propofol sedation offers advantages for titration and rapid emergence in the critically ill patient, but concern for adverse hemodynamic effects potentially limits its use in these patients. The current study compares the cardiovascular effects of sedation with propofol versus midazolam during the first 12 h after coronary revascularization. METHODS: Three hundred fifty-one patients undergoing coronary revascularization were anesthetized using a standardized sufentanil/midazolam regimen, and assigned randomly to 12 h of sedation with either propofol or midazolam while tracheally intubated. The incidence and characteristics of hemodynamic episodes, defined as heart rate less than 60 or greater than 100 beats/min or systolic blood pressure greater than 140 or less than 90 mmHg, were determined using data electronically recorded at 1-min intervals. The presence of myocardial ischemia was determined using continuous three-channel Holter electrocardiography (ECG) and of myocardial infarctions (MI) using 12-lead ECG (Q wave MI, Minnesota Code) or creatine kinase isoenzymes (CK-MB) analysis (non-Q wave MI, peak CK-MB > 70 ng/ml, or CK-MB > 70 IU/I). RESULTS: Ninety-three percent of patients in both treatment groups had at least one hemodynamic episode during the period of postoperative sedation. Propofol sedation resulted in a 17% lower incidence of tachycardia (58% vs. 70%, propofol vs. midazolam; P = 0.04), a 28% lower incidence of hypertension (39% vs. 54%; P = 0.02), and a greater incidence of hypotension (68% vs. 51%; P = 0.01). Despite these hemodynamic effects, the incidence of myocardial ischemia did not differ between treatment groups (12% propofol vs. 13% midazolam; P = 0.66), nor did its severity, as measured by ischemic minutes per hour monitored (8.7 +/- 5.8 vs. 6.2 +/- 4.6 min/h, propofol vs. midazolam; P = 0.19) or ischemic area under the curve (6.8 +/- 4.0 vs. 5.3 +/- 4.2; P = 0.37). The incidence of cardiac death (one per group), Q wave MI (propofol, n = 7; midazolam, n = 3; P = 0.27), or non Q wave MI (propofol, n = 16; midazolam, n = 18; P = 0.81) did not differ between treatment groups. CONCLUSIONS: Hemodynamic episodes occur frequently in the first 12 h after coronary revascularization. Compared with a standard sedation regimen (midazolam), propofol sedation appears to modulate postoperative hemodynamic responses by reducing the incidence and severity of tachycardia and hypertension and increasing the incidence of hypotension. Both sedation regimens appear similarly safe with respect to myocardial ischemia. These findings indicate that propofol infusion provides effective sedation without deleterious hemodynamic effects in patients recovering from cardiac surgery.

Adult↗
PubMed1980

Hemodynamic responses to different modes of mechanical ventilation in dogs with normal and acid aspirated lungs.

Hemodynamic function during spontaneous breathing (SB), IMV, IPPV, continuous positive airway pressure with 10 torr PEEP (CPAP10), IMV with 10 torr PEEP (IMV10), and continuous positive pressure ventilation with 10 torr PEEP (CPPV10) were studied in 13 normovolemic anesthetized dogs. Hemodynamic function was also studied during each type of ventilation after inducing acid aspiration with 0.1 molar HCl, 5 ml/kg, in these animals. In normal dogs, hemodynamic function during IMV and IPPV did not differ significantly from that observed in spontaneously breathing dogs. CPAP10 had no effect on the hemodynamic function. IMV10 decreased cardiac index, increased arterial-mixed venous O2 content difference (avDO2) compared to SB and decreased stroke index compared to SB, IMV, and CPAP10. CPPV10 significantly decreased cardiac and stroke indicies compared to SB, IMV, IPPV and CPAP10, and increased avDO2 compared to SB. After acid aspiration, IMV did not affect the hemodynamic function, but IPPV caused a significant decrease in stroke index compared to SB. Again, CPAP10 had no significant effect on the hemodynamic function. IMV10 decreased cardiac index and increased systemic vascular resistance compared to SB and decreased stroke index compared to SB and IMV. CPPV10 increased pulmonary vascular resistance and avDO2 compared to SB, decreased cardiac index compared to SB and IMV, decreased stroke index compared to SB, IMV, and CPAP10 and increased systemic vascular resistance compared to SB, IMV, IPPV, and CPAP10. Comparing percentage change of cardiac and stroke indices before and after aspiration indicated that the decrease in lung compliance caused by acid aspiration did not prevent the hemodynamic effects of different types of ventilation. Among different types of mechanical ventilation with PEEP, CPAP10 caused the least cardiovascular depression.

Animals↗
PubMed1996

Acute hemodynamic and neurohoromonal effects of furosemide in critically ill pediatrics patients.

OBJECTIVES: To study the acute hemodynamic effects of furosemide in critically ill pediatrics patients, the temporal relationship between hemodynamic changes and changes in neuroendocrine axis, and the temporal relationship between hemodynamic changes and urine output. DESIGN: Prospective study. SETTING: Pediatric intensive care unit in a tertiary care university center. PATIENTS: Fourteen critically ill pediatric patients who clinically required diuretic therapy. INTERVENTIONS: Before and after furosemide administration, hemodynamic and neurohormonal measurements were taken. MEASUREMENTS AND MAIN RESULTS: Hemodynamic and neurohormonal responses to acute diuretic therapy were measured in 14 pediatric patients treated with furosemide (1 mg/kg/dose). Cardiac index deteriorated by 10 mins after drug administration (-9.4+/-3.9%, p<.05) and was associated with an increase in systemic vascular resistance (17.1+/-4.8%, p<.05). There was a subsequent increase in cardiac index (20+/-4.9%, p<.05) at 30 mins, with a decrease in systemic vascular resistance (-11.5+/-5.2%, p<.05). These hemodynamic changes were associated with marked increases in renin and norepinephrine concentrations and an increase in urinary prostaglandin release. The hemodynamic and neurohormonal effects had their onset before maximum diuresis. CONCLUSION: Intravenous furosemide administration in acutely ill pediatric patients results in an acute but transient deterioration in cardiac function that appears to parallel the neuroendocrine changes rather than the acute diuresis.

Adolescent↗