Hemodynamic effects of head-down tilt in normal subjects and sustained hypertensive patients

1983 ◽  
Vol 245 (2) ◽  
pp. H194-H202 ◽  
Author(s):  
G. M. London ◽  
J. A. Levenson ◽  
M. E. Safar ◽  
A. C. Simon ◽  
A. P. Guerin ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Plasma Renin Activity ◽  
Central Venous Pressure ◽  
Baroreflex Sensitivity ◽  
Venous Pressure ◽  
Plasma Renin ◽  
Arterial Baroreflex ◽  
Central Venous ◽  
Venous Tone ◽  
Hypertensive Patients

Central and forearm arterial and venous hemodynamics, arterial baroreflex sensitivity, plasma renin activity, and catecholamines were studied in supine position and after -10 degrees head-down tilt in 29 patients with sustained essential hypertension and in 29 normotensive controls of the same age and sex. In both populations, blood pressure, heart rate, and arterial baroreflex sensitivity did not change during the maneuver. Head-down tilt induced a similar increase in cardiopulmonary blood volume in controls and hypertensives, whereas the increase in central venous pressure, cardiac output, and forearm blood flow was higher in hypertensives. Forearm venous tone decreased in controls (from 16.6 +/- 0.8 to 13.8 +/- 0.9 mmHg X ml-1 X 100 g-1; P less than 0.01) but did not change in hypertensive patients (24.9 +/- 1.6 vs. 25.1 +/- 1.9. The magnitude of forearm vascular resistance changes induced by head-down tilt were significantly related to the basal venous tone in the overall population (P less than 0.01). The decrease in plasma renin activity and plasma catecholamines was similar in the two groups. The study provides the evidence that the higher increase in cardiac output and local flow observed in head-down tilt in hypertensive patients is probably due to a higher change in central venous pressure related to a decrease in venous distensibility.

Cardiopulmonary blood volume and plasma renin activity in normal and hypertensive humans

1985 ◽  
Vol 249 (4) ◽  
pp. H807-H813
Author(s):  
G. M. London ◽  
A. P. Guerin ◽  
J. D. Bouthier ◽  
A. M. London ◽  
M. E. Safar
Keyword(s):  
Plasma Renin Activity ◽  
Central Venous Pressure ◽  
Blood Volume ◽  
Neural Control ◽  
Venous Pressure ◽  
Plasma Renin ◽  
Renin Activity ◽  
Renin Release ◽  
Central Venous ◽  
Hypertensive Patients

Plasma renin activity (PRA) and systemic and forearm hemodynamics were studied during acute changes in cardiopulmonary blood volume and central venous pressure in 20 subjects, including 9 normotensive controls and 11 essential hypertensive patients of the same age. Changes in cardiopulmonary blood volume and central venous pressure were induced by a "head-down" tilt and thigh-cuff inflation. Blood pressure, pulse pressure, and heart rate did not change during cardiopulmonary blood volume variations, whereas significant changes in cardiac output, forearm blood flow, and PRA were observed. A significant negative correlation between cardiopulmonary blood volume (CPBV) and PRA existed, and slope of this correlation of delta PRA/delta CPBV was estimated as a sensitivity index of control of renin release. Sensitivity of neural control of renin release was not statistically different in normal subjects and hypertensive patients. In two groups, sensitivity of this reflex mechanism similarly decreased with age. Aging seems to be an important factor influencing the sensitivity of neural control of renin release, both in normal and essential hypertensive humans.

Circulation, kidney function, and volume-regulating hormones during prolonged water immersion in humans

1992 ◽  
Vol 73 (2) ◽  
pp. 530-538 ◽  
Author(s):  
C. Stadeager ◽  
L. B. Johansen ◽  
J. Warberg ◽  
N. J. Christensen ◽  
N. Foldager ◽  
...  
Keyword(s):  
Stroke Volume ◽  
Plasma Renin Activity ◽  
Central Venous Pressure ◽  
Water Immersion ◽  
Venous Pressure ◽  
Plasma Renin ◽  
Plasma Aldosterone ◽  
Central Blood Volume ◽  
Central Venous ◽  
Electrolyte Excretion

To investigate whether prolonged water immersion (WI) results in reduction of central blood volume and attenuation of renal fluid and electrolyte excretion, these variables were measured in connection with 12 h of immersion. On separate days, nine healthy males were investigated before, during, and after 12 h of WI to the neck or during appropriate control conditions. Central venous pressure, stroke volume, renal sodium (UNaV) and fluid excretion increased on initiation of WI and thereafter gradually declined but were still elevated compared with control values at the 12th h of WI. Atrial natriuretic peptide (ANP) concentration in plasma initially increased threefold during WI and thereafter declined to preimmersion levels, whereas plasma renin activity, plasma aldosterone, and norepinephrine remained constantly suppressed. It is concluded that, compared with the initial increases, central blood volume (central venous pressure and stroke volume) is reduced during prolonged WI and renal fluid and electrolyte excretion is attenuated. UNaV is still increased at the 12th h of WI, whereas renal water excretion returns to control values within 7 h. The WI-induced changes in ANP, plasma renin activity, plasma aldosterone, and norepinephrine may all contribute to the initial increase in UNaV. The results suggest, however, that the attenuation of UNaV during the later stages of WI is due to the decrease in ANP release.

Cardiovascular actions of histamine and potassium

1959 ◽  
Vol 197 (5) ◽  
pp. 1005-1007 ◽  
Author(s):  
Calvin Hanna ◽  
Patricia B. McHugo ◽  
William H. MacMillan
Keyword(s):  
Cardiac Output ◽  
Central Venous Pressure ◽  
Potassium Chloride ◽  
Venous Pressure ◽  
Plasma Potassium ◽  
Dilution Method ◽  
Cardiac Rate ◽  
Central Venous ◽  
Arterial Blood ◽  
Cardiovascular Actions

The cardiovascular actions of intravenous histamine, in doses from 2.5 to 20 µg/kg of the free base, were studied in the pentobarbitalized dog using the dye dilution method. With the small dose there was a consistent but small initial increase in cardiac output and with the larger doses there was a biphasic change in output. Cardiac rate, central venous pressure, central blood volume, hematocrit and the mean circulation time were essentially unchanged. Infusions of histamine and of potassium chloride at the rate of 1 µg and 1 mg/kg/min., respectively, moderately increased the cardiac output. Potassium chloride had no effect on the arterial blood pressure, cardiac rate and central venous pressure. Both the infusion of potassium chloride and injection of histamine produced a comparable elevation of the plasma potassium. It is possible that the actions of histamine to increase the plasma potassium contribute to the cardiovascular actions of this amine, especially on the cardiac output.

Effect of head-down tilt on basal plasma norepinephrine and renin activity in humans

1985 ◽  
Vol 59 (4) ◽  
pp. 1068-1071 ◽  
Author(s):  
S. R. Goldsmith ◽  
G. S. Francis ◽  
J. N. Cohn
Keyword(s):  
Arterial Pressure ◽  
Central Venous Pressure ◽  
Venous Pressure ◽  
Plasma Renin ◽  
Normal Subjects ◽  
Renin Activity ◽  
Plasma Norepinephrine ◽  
Central Venous ◽  
Basal Plasma ◽  
Cardiopulmonary Baroreceptors

The effects of loading cardiopulmonary baroreceptors on basal norepinephrine and renin activity were studied in six normal subjects. Loading of cardiopulmonary baroreceptors was accomplished by a 60-min 30 degrees head-down tilt with small supplemental saline infusions. Central venous pressure was measured continuously by intrathoracic catheter; arterial pressure was measured indirectly by cuff. During the tilt, central venous pressure increased from 5.1 +/- 1.3 to 8.9 +/- 1.7 mmHg (P less than 0.001), whereas arterial pressure was unchanged. Plasma norepinephrine (185 +/- 85 pg/ml) and plasma renin activity (3.9 +/- 5.7 ng . ml-1 . h-1) did not change. Moderate sustained loading of cardiopulmonary baroreceptors is therefore without effect on unstressed plasma norepinephrine and renin activity in normal humans, suggesting that the tonic inhibitory effects of these receptors on these neurohumoral control systems are not readily increased in the basal state.

scholarly journals Effects of Different Doses of Magnesium Sulfate on Pneumoperitoneum-related Hemodynamic Changes in Patients Undergoing Gastrointestinal Laparoscopy: a randomized, double-blind, controlled trial

2019 ◽  
Author(s):  
Wei Tan ◽  
Dong-chen Qian ◽  
Meng-meng Zheng ◽  
Xuan Lu ◽  
Yuan Han ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Central Venous Pressure ◽  
Magnesium Sulfate ◽  
Systemic Vascular Resistance ◽  
Vascular Resistance ◽  
Venous Pressure ◽  
Control Group ◽  
Central Venous

Abstract Background: The infusion of magnesium sulfate is well known to reduce arterial pressure and attenuate hemodynamic response to pneumoperitoneum. This study aimed to investigate whether different doses of magnesium sulfate can effectively attenuate the pneumoperitoneum-related hemodynamic changes and the release of vasopressin in patients undergoing laparoscopic gastrointestinal surgery. Methods: Sixty-nine patients undergoing laparoscopic partial gastrectomy were randomized into three groups: group L received magnesium sulfate 30 mg/kg loading dose and 15 mg/kg/h continuous maintenance infusion for 1 h; group H received magnesium sulfate 50 mg/kg followed by 30 mg/kg/h for 1 h; and group S (control group) received same volume 0.9% saline infusion, immediately before the induction of pneumoperitoneum. Systemic vascular resistance (SVR), cardiac output (CO), mean arterial pressure (MAP), heart rate (HR), central venous pressure(CVP), serum vasopressin and magnesium concentrations were measured. The extubation time, visual analogue scale were also assessed. The primary outcome is the difference in SVR between different groups. The secondary outcome is the differences of other indicators between groups, such as CO, MAP, HR, CVP, vasopressin and postoperative pain score. Results: Pneumoperitoneum instantly resulted in a significant reduction of cardiac output and an increase in mean arterial pressure, systemic vascular resistance, central venous pressure and heart rate in the control group (P < 0.01). The mean arterial pressure (T2 – T4), systemic vascular resistance (T2 – T3), central venous pressure(T3-T5) and the level of serum vasopressin were significantly lower (P < 0.05) and the cardiac output (T2 – T3) was significantly higher (P < 0.05) in group H than those in the control group. The mean arterial pressure (T4), systemic vascular resistance (T2), and central venous pressure(T3-T4) were significantly lower in group H than those in group L (P < 0.05). Furthermore, the visual analog scales at 5 min and 20 min, the level of vasopressin, and the dose of remifentanil were significantly decreased in group H compared to the control group and group L (P < 0.01). Conclusion: Magnesium sulfate could safely and effectively attenuate the pneumoperitoneum-related hemodynamic instability during gastrointestinal laparoscopy and improve postoperative pain at serum magnesium concentrations above 2 mmol/L.

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