Search

Fenoldopam, a vasodilating agent, may represent a potential therapeutic opportunity to increase renal perfusion in those conditions where renal hemodynamics are severely impaired by vascular sub-occlusion, as, indeed, is the case in thrombotic microangiopathies. The renal resistance index (RRI) was measured, on and off fenoldopam, in 27 children with STEC-HUS. A 12% decrease in RRI was observed on fenoldopam compared to off treatment without changes in the systemic hemodynamics and with no side effects. If confirmed in larger series, fenoldopam may become an important addition to supportive care to reduce ischemic damage in STEC-HUS and improve long-term outcomes.

Background Current research highlights the role of microcirculatory disorders in post-cardiac arrest patients. Affected microcirculation shows not only dissociation from systemic hemodynamics but also strong connection to outcome of these patients. However, only few studies evaluated microcirculation directly during cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). The aim of our experimental study in a porcine model was to describe sublingual microcirculatory changes during CA and CPR using recent videomicroscopic technology and provide a comparison to parameters of global hemodynamics. Methods Cardiac arrest was induced in 18 female pigs (50 ± 3 kg). After 3 min without treatment, 5 min of mechanical CPR followed. Continuous hemodynamic monitoring including systemic blood pressure and carotid blood flow was performed and blood lactate was measured at the end of baseline and CPR. Sublingual microcirculation was assessed by the Sidestream Dark Field (SDF) technology during baseline, CA and CPR. Following microcirculatory parameters were assessed off-line separately for capillaries (≤20 µm) and other vessels: total and perfused vessel density (TVD, PVD), proportion of perfused vessels (PPV), microvascular flow index (MFI) and heterogeneity index (HI). Results In comparison to baseline the CA small vessel microcirculation was only partially preserved: TVD 15.64 (13.59–18.48) significantly decreased to 12.51 (10.57–13.98) mm/mm2, PVD 15.57 (13.56–17.80) to 5.53 (4.17–6.60) mm/mm2, PPV 99.64 (98.05–100.00) to 38.97 (27.60–46.29) %, MFI 3.00 (3.00–3.08) to 1.29 (1.08–1.58) and HI increased from 0.08 (0.00–0.23) to 1.5 (0.71–2.00), p = 0.0003 for TVD and

The topic of cardiorespiratory interactions is of extreme importance to the practicing intensivist. It also has a reputation for being intellectually challenging, due in part to the enormous volume of relevant, at times contradictory literature. Another source of difficulty is the need to simultaneously consider the interrelated functioning of several organ systems (not necessarily limited to the heart and lung), in other words, to adopt a systemic (as opposed to analytic) point of view. We believe that the proper understanding of a few simple physiological concepts is of great help in organizing knowledge in this field. The first part of this review will be devoted to demonstrating this point. The second part, to be published in a coming issue of Intensive Care Medicine, will apply these concepts to clinical situations. We hope that this text will be of some use, especially to intensivists in training, to demystify a field that many find intimidating.

The present study was designed to evaluate pulmonary and systemic hemodynamics and blood gas changes on switching from conventional mechanical ventilation (CMV) to high-frequency oscillatory ventilation (HFOV) in a large animal model of acute lung injury.Eleven anesthetised sheep chronically instrumented with vascular monitoring were prepared. Animals received oleic acid (0.08 ml x kg(-1)) intravenously and were ventilated for 4 h h after the administration of oleic acid. The animals were then randomized into the two following different ventilation modes: CMV (tidal volume [V(T)], 6 ml x kg(-1); respiratory rate [RR], 25 x min(-1)) with positive end-expiratory pressure (PEEP) of 12 cmH(2)O; or CMV under the same settings without PEEP. HFOV was then switched. The setting of mean airway pressure with a fixed stroke volume was changed between 25, 18, and 12 cmH(2)O every 20 min. Mean pulmonary artery pressure, pulmonary artery occlusive pressure (Paop), left atrium pressure, systemic arterial pressure, cardiac output (CO), and blood gas composition under each setting were measured before and after HFOV.Switching to HFOV, from without PEEP, resulted in significant increases in Paop and PaO2 and a decrease in CO at higher (25, 18 cmH(2)O) mean airway pressure. However, when changed from low V(T) and PEEP, HFOV produced further improvements in oxygenation without any deterioration of cardiovascular depression. Thus, switching to HFOV from CMV with low V(T) and high PEEP may have little influence on pulmonary or systemic hemodynamics in acute lung injury.We conclude that hemodynamic responses are dependent on the predefined setting of PEEP during CMV, and on applied mean airway pressure during HFOV.

Power spectral density of heart rate fluctuations in the range of 0.02-5.00 Hz in August rats was lower than in Wistar rats. Changes in mean blood pressure and heart rate during stress (15-min immobilization) were similar in animals of both strains. As differentiated from Wistar rats, power spectral density of fluctuations in August rats considerably decreased after stress. August rats were characterized by low spectral power at rest and high resistance to the arrhythmogenic effect of 10-min acute myocardial ischemia.

Detailed analysis of the subjective sensations of 135 healthy subjects during 20- to -30 min voluntary hyperventilation was performed. The hyperventilation levels (V EI = 20 l/min, V EII = 30 l/min, V EIII = 40 l/min) were chosen so that manifestations of paroxysms of hyperventilation syndrome (HVS) of different severity were simulated. Regular features in the time course of development of HVS symptoms were revealed: (1) specific peripheral subjective sensations and symptoms changed consistently, being peculiar sensory equivalents (correlates) of hyperventilation-related changes in gaseous metabolism and acid-base balance; (2) sensations and symptoms of central origin developed in waves, with considerable individual variations in manifestation and emotional hue and were closely correlated with changes in systemic hemodynamics and brain circulation disorders.

Systemic vasodilation produced by sodium nitroprusside in various concentrations and accompanied by a decrease in baseline blood pressure was followed by progressive reduction in pressor responses to α-adrenoceptor agonist phenylephrine (mesatone) in rats. In a blood pressure range of below the physiological level (80-100 mm Hg), a positive linear correlation was revealed between the decrease in baseline blood pressure and pressor effect of phenylephrine.

Correlation between blood pressure and parameters of systemic hemodynamics was studied on cats using electrical stimulation of the ventral medulla oblongata. Changes in blood pressure induced by presoor activation were related to venous hemodynamics in the anterior rather than posterior vena cava. Venous blood flow is assumed to be involved in hemodynamic changes caused by stimulation of pressor centers but not depressor centers in the ventral medulla oblongata.

Systemic hemodynamics characterizing blood circulation, body state, and parameters of correction attracts the attention of scientists and physicians. The term "regulation" is generally accepted in biology and physiology, it corresponds to terms "operation" and "control" used in technical literature. Automatic control implies stability of a certain parameter or its changes that obey a specified law (program control) or correspond to an external process (followup control) affecting regulatory elements of the object. Automatic operation maintains or improves the functioning of some controlled object according to certain requirements. Systemic hemodynamics is responsible for adequate blood circulation in organs and tissues. A considerable body of data shows nervous, humoral, hemodynamic, and local mechanisms of regulation of systemic hemodynamics. However, there is no consensus on the object of regulation. There are good reasons to believe that blood pressure (BP), cardiac output (CO), or capillary blood flow is the object of regulation. However, it is necessary to emphasize that BP is an integral parameter depending on CO and total peripheral vascular resistance (TPVR). Therefore, BP is maintained at constant level, while CO and TPVR can vary. Since CO only little changes during short-term and long-term BP fluctuations, BP is primarily determined by TPVR. Hence, TPVR is the regulated parameter (by analogy with organ circulation when the blood supply is determined by the diameter of arterioles). If it is granted that BP is the parameter of control, there

Electroacupuncture decreased total peripheral vascular resistance and increased cardiac output in 12-week-old postinfarction rats without cardiac insufficiency, while opposite changes were observed in rats with cardiac insufficiency. After the electroacupuncture course, norepinephrine decreased cardiac output in the rats with cardiac insufficiency, while acetylcholine increased it to a much higher extent than in the control rats that were not subjected to physiotherapy.

Blockade of NO synthesis in narcotized rats potentiated pressor effects of phenylephrine by 55% and increased total peripheral resistance by 153%. Vasodilation caused by enhanced NO secretion modulated pressor shifts evoked by stimulation of alpha(1)-adrenoceptors with phenylephrine.

Experiments on cats demonstrate the capacity of alert animals to compensate for disorders in pulmonary and systemic hemodynamics caused by organophosphorus compounds. Heart rate, systemic arterial pressure, and total peripheral resistance completely normalize on day 3 after exposure. Pulmonary vascular resistance and pulmonary blood pressure remain negligibly increased.

The effect of acute streptozotocin-induced diabetes mellitus on the systemic hemodynamic parameters was studied in conscious rats by thermodilution technique. Male Wistar rats were made diabetic with a single intravenous injection of streptozotocin (STZ, 50 mg/kg). The most important finding of this work was the elucidation of the systemic vasodilation and increased cardiac index one day after STZ injection. Such alteration in hemodynamic parameters could result in the increased blood flow and capillary hypertension in some vascular beds and, therefore, be considered as a pathogenic factor in the development of diabetic microangiopathy.

The effects of Polyosm (polyethylene oxide 400 solution) on viscoelastic properties of the craniospinal system in cats and parameters of systemic hemodynamics were studied on the model of acute hypertensive encephalopathy, induced by intravenous injection of norepinephrine hydrotartrate and intracarotid infusion of papaverine hydrochloride. In control series, a sustained increase in the central venous and intracranial pressure, enhancement of resistance to liquor drainage, and pronounced increase in rigidity of the craniospinal system were observed. Intravenous infusion of Polyosm moderated these disturbances of the blood and liquor dynamics and restored viscoelastic properties of the craniospinal system to an almost initial level.

Bei 28 Patienten mit Leberzirrhose wurde die Wirkung von Pituitrin und Phentolamin allein und von der Kombination von beiden auf WHVP (wedged hepatic venous pressure) und auf die systemische Hamodynamik beobachtet. Die Ergebnisse haben gezeigt, das jede der beiden Substanzen bei separater Anwendung zur signifikanten Abnahme von WHVP, aber gleichzeitig auch zu Nebenwirkungen auf die systemische Hamodynamik fuhren konnte. Wenn Pituitrin plus Phentolamin angewandt wurde, konnten wir eine signifikante Senkung von WHVP, jedoch keine signifikante Veranderung von IVCP (inferior vena cava pressure), MAP (mean arterial pressure), P (pulse rate) und CI (cardiac index) beobachten. Auserdem zeigte sich bei der Kombinationstherapie auch eine Verbesserung der Lebermikrozirkulation. Diese Befunde stutzen die Empfehlung zur gleichzeitigen klinischen Anwendung von vasodilatatorischen und vasokonstriktorischen Medikamenten bei der Behandlung der Blutung aus Osophagusvarizen.

The systemic and regional hemodynamics during antiorthostatic hypokinesia were studied in male Wistar rats using the radioactive microsphere technique. The animals were hanged up by the tail with the head tilted down (30 degrees) and were able to exercise using only front limbs. Twenty four hours long exposure to antiorthostasis induced significant changes in systemic hemodynamics as well as in regional blood flow in skeletal muscles, spleen, liver and pancreas. Antiorthostasis induced blood flow changes in lungs, heart and brain were less pronounced.

Two types of hemodynamic rearrangements, due to a decrease in the stroke index and a decrease in the total peripheral vascular resistance, are revealed. As a result of treatment these rearrangements allow the systolic and diastolic arterial pressure to be corrected and enable the severity of clinical symptoms to be reduced along with the doses of administered drugs.

Endogenous peptide DBI inhibits the activity of HABA-ergic system and that is why can be a factor of arterial hypertension development. We investigated DBI influence on cardiac index (CI), arterial pressure (AP) and heart rate (HR) in rats. I.v. administration of DBI caused dose--dependent increase in CI, AP but HR did not change. High dose (150 mg/kg) caused a biphasic answer: hyperkinetic reaction reversed to cardiodepressive one. Long-term immunization against DBI led to decrease of AP and systemic vessel's resistance.

Inhaled nitric oxide (iNO) has been shown to selectively reduce pulmonary hypertension in several biologic models. However, iNO is not as convenient as one might wish. We tested the effects of Neb-NP (a user-friendly analog of inhaled nitric oxide) on pulmonary and systemic hemodynamics during pulmonary hypertension induced by hypoxia in piglets.

The effect of cerebral ischemia produced by compression of both common carotid arteries on the mesenteric microcirculation was studied in experiments on rats. The extent and intensity of the microcirculatory disturbances were shown to depend on the duration of ischemia and of the postischemic period. The state of the systemic hemodynamics was compared with that of the mesenteric microcirculation. The possible mechanisms of the microcirculatory disturbances are discussed.

Portal pressure and systemic hemodynamics were evaluated for 30 minutes after intravenous injection of 400 mg of cimetidine in patients with and without liver cirrhosis when they were operated upon for varying surgical diseases. A transient fall of arterial pressure was seen in both groups of patients, but the change was statistically significant only in those with cirrhosis. Cimetidine did not substantially alter pulse rate, CVP, and portal pressure in both groups. The present results seem to indicate that rapid administration of cimetidine does not induce a fall of portal venous pressure in both cirrhotic and non-cirrhotic patients.

Indices of the central hemodynamics were studied in puppies aged 18–22 days and 2–3 months and in dogs aged 3–5 years after intravenous injection of synthetic vasopressin (0.8 unit/kg body weight). The pressor effect was strongest in the adult dogs and bradycardia in the puppies aged 18–22 days. The cardiac output was reduced in all animals and the peripheral resistance considerably increased. In adult dogs the external work of the left ventricle and the energy consumption of the heart were increased. In puppies a reduction in the volume velocity of ejection of blood and in the external work of the heart was combined with a smaller increase in energy consumption.

It was shown, that local influence of galvanic current upon the lung angiotensin converting enzyme (ACE) in spontaneously hypertensive rats led to a decrease of systemic blood pressure in consequence of reduced peripheral vascular resistance. The development of the hemodynamic alteration was accompanied by variations of physiological and biochemical indices of the lung ACE-activity. These results indicate that the ACE-dependent processes in the lung play on important role in the mechanisms of vasoconstriction, increase in vascular resistance and development of arterial hypertension.

The role of the β-adrenergic system in the adaptation of cardiac output and coronary flow to exercise was investigated in 9 conscious dogs. Some of the experiments were carried out in dogs with experimental atrio-ventricular block and paced heart rates.

The arterial pressure, cardiac output, total peripheral resistance, and heart rate were studied in experiments on puppies aged 18–22 days and 2–3 months and on adult dogs receiving injections of synthetic angiotensin II-amide in a dose of 2 μg/kg body weight/min. Elevation of the arterial pressure in the adult dogs as a result of the action of angiotensin was due to an increase in the total peripheral resistance, but in puppies it was due to an increase both in the total peripheral resistance and in the cardiac output.