Cerebral and cardiovascular responses to changes in head elevation in patients with intracranial hypertension

1983 ◽  
Vol 59 (6) ◽  
pp. 938-944 ◽  
Author(s):  
Quentin J. Durward ◽  
A. Lorne Amacher ◽  
Rolando F. Del Maestro ◽  
William J. Sibbald
Keyword(s):  
Cardiac Output ◽  
Intracranial Hypertension ◽  
Cardiovascular Responses ◽  
Arterial Oxygen ◽  
Optimum Level ◽  
Moderate Degree ◽  
Content Type ◽  
Arterial Oxygen Content ◽  
Head Elevation ◽  
The Mean

✓ To establish if an optimum level of head elevation exists in patients with intracranial hypertension, the authors examined changes in intracranial pressure (ICP), systemic and pulmonary pressures, systemic flows, and intrapulmonary shunt fraction with the patient lying flat, and then with the head elevated at 15°, 30°, and 60°. Cerebral perfusion pressure (CPP) was calculated. The lowest mean ICP was found with elevation of the head to 15° (a fall of −4.5 ± 1.6 mm Hg, p < 0.001) and 30° (a fall of −6.1 ± 3.5 mm Hg, p < 0.001); the CPP and cardiac output were maintained. With elevation of the head to 60°, the mean ICP increased to −3.8 ± 9.3 mm Hg of baseline, while the CPP decreased −7.9 ± 9.3 mm Hg (p < 0.02), and the cardiac index also fell −0.25 ± 0.28 liters/min/sq m (p < 0.01). No significant change in filling pressures, arterial oxygen content, or heart rate was encountered at any level of head elevation. Therefore, a moderate degree (15° or 30°) of head elevation provides a consistent reduction of ICP without concomitant compromise of cardiac function. Lower (0°) or higher (60°) degrees of head elevation may be detrimental to the patient because of changes in the ICP, CPP, and cardiac output.

CARDIAC OUTPUT IN ACUTE EXPERIMENTAL METHEMOGLOBINEMIA

1960 ◽  
Vol 38 (12) ◽  
pp. 1411-1416 ◽  
Author(s):  
C. W. Gowdey
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Blood Viscosity ◽  
Peripheral Resistance ◽  
Cardiovascular Responses ◽  
Arterial Oxygen ◽  
Hematocrit Level ◽  
Arterial Oxygen Content ◽  
Anesthetized Dogs ◽  
Oxygen Difference

Methemoglobinemia induced in normal anesthetized dogs by intravenous infusions of aniline resulted in a decreased arterial oxygen content and a marked increase in cardiac output. Heart rate, arterial pressure, blood viscosity, and oxygen consumption increased, while total peripheral resistance and arteriovenous oxygen difference decreased. The elevation of cardiac output occurred in spite of the fact that the hematocrit level and blood viscosity increased. Ganglion-blocking doses of pentolinium bitartrate did not significantly alter the cardiovascular responses to the methemoglobinemia.

CARDIAC OUTPUT IN ACUTE EXPERIMENTAL METHEMOGLOBINEMIA

1960 ◽  
Vol 38 (1) ◽  
pp. 1411-1416 ◽  
Author(s):  
C. W. Gowdey
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Blood Viscosity ◽  
Peripheral Resistance ◽  
Cardiovascular Responses ◽  
Arterial Oxygen ◽  
Hematocrit Level ◽  
Arterial Oxygen Content ◽  
Anesthetized Dogs ◽  
Oxygen Difference

Methemoglobinemia induced in normal anesthetized dogs by intravenous infusions of aniline resulted in a decreased arterial oxygen content and a marked increase in cardiac output. Heart rate, arterial pressure, blood viscosity, and oxygen consumption increased, while total peripheral resistance and arteriovenous oxygen difference decreased. The elevation of cardiac output occurred in spite of the fact that the hematocrit level and blood viscosity increased. Ganglion-blocking doses of pentolinium bitartrate did not significantly alter the cardiovascular responses to the methemoglobinemia.

Pressure in the sagittal sinus during intracranial hypertension in man

1974 ◽  
Vol 40 (5) ◽  
pp. 603-608 ◽  
Author(s):  
Albert N. Martins ◽  
Arthur I. Kobrine ◽  
Douglas F. Larsen
Keyword(s):  
Brain Tumors ◽  
Intracranial Hypertension ◽  
Cerebral Blood Volume ◽  
Content Type ◽  
Sagittal Sinus ◽  
Sagittal Sinus Pressure ◽  
The Mean ◽  
The Difference ◽  
Spatial Compensation ◽  
Sinus Pressure

✓ Intracranial pressure (ICP) and sagittal sinus pressure (SSP) were measured simultaneously in 12 patients with brain tumors and secondary intracranial hypertension (ICH). In nine, the mean SSP was largely unaffected by changes in ICP. In three, SSP changed with the ICP. In all but one patient, the ICP remained higher than SSP and, as the ICP increased, the difference between the two also increased. Sinograms performed during ICH demonstrated partial collapse of the sinuses in some patients and not in others. The mean SSP in adults with brain tumors appears to respond unpredictably to changes in ICP. Since the rate of cerebrospinal fluid drainage depends upon the gradient between ICP and SSP, intracranial spatial compensation is probably influenced by the response of SSP to ICP. Individuals with gradients that rapidly increase because their sinuses do not collapse probably compensate more rapidly than those whose sinuses do collapse. This assumed difference in the rate of spatial compensation may account for some of the variability of the ICP response to an enlarging intracranial mass or a change in cerebral blood volume.

Systemic oxygen transport in induced normovolemic anemia and polycythemia

1962 ◽  
Vol 203 (4) ◽  
pp. 720-724 ◽  
Author(s):  
John F. Murray ◽  
Philip Gold ◽  
B. Lamar Johnson
Keyword(s):  
Cardiac Output ◽  
Oxygen Transport ◽  
Arterial Oxygen Saturation ◽  
Peripheral Resistance ◽  
Arterial Oxygen ◽  
Peripheral Vascular ◽  
Arterial Oxygen Content ◽  
Normovolemic Anemia ◽  
Systemic Oxygen ◽  
Negative Linear Relationship

The hemodynamic effects of normovolemic anemia and polycythemia were studied in 14 dogs. Anemia (5 dogs) and polycythemia (5 dogs) were induced by bleeding and simultaneously infusing dextran or packed erythrocytes. Measurements included cardiac output, arterial oxygen saturation, peripheral vascular resistance, and systemic oxygen transport (cardiac output X arterial oxygen content). Cardiac output had a significant negative linear relationship to hematocrit ( r = –0.74, P < 0.01) over the range studied (13–74%). Peripheral resistance fell 46% in anemic animals and increased 152% in four of five polycythemic animals. Arterial saturation was significantly correlated to changes in hematocrit ( r = 0.62, P < 0.01) and cardiac output ( r = –0.55, P < 0.01); these values were due primarily to the linearity encountered in the anemia experiments and a reversal in these relationships tended to occur at high hematocrits. Systemic oxygen transport was maximum at normal hematocrits and decreased in anemia and polycythemia. The data indicate that hemodynamic adjustments in normovolemic anemia and polycythemia are insufficient to maintain normal oxygen delivery.

Effects of khellin on coronary blood flow and related metabolic functions

1959 ◽  
Vol 196 (2) ◽  
pp. 391-393 ◽  
Author(s):  
Richard L. Farrand ◽  
Steven M. Horvath
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Coronary Blood Flow ◽  
Control Period ◽  
Systemic Arterial Pressure ◽  
Arterial Oxygen ◽  
Arterial Oxygen Content ◽  
Fick Principle ◽  
Metabolic Functions ◽  
Pulmonary Arterial

Khellin, a drug employed as a coronary dilator, was tested to determine its effects on the cardiovascular system of the dog. Ten mongrel dogs were anesthetized with Nembutal and, after control observations were made, given an intravenous administration of 1 mg/kg body weight of khellin. Coronary blood flow and cardiac output samples were drawn during the control period and at 10, 40 and 80 minutes after administration of the drug Cardiac output was calculated by the direct Fick principle and coronary blood flow by the nitrous oxide method. There was a significant (5%) increase in the arterial oxygen content during the 10- and 40-minute intervals, but no change was observed at 80 minutes. An increase in arterial-mixed venous oxygen difference occurred at 40 and 80 minutes. No change in systemic arterial pressure or cardiac output was noted at any time. Coronary blood flow had decreased slightly at 80 minutes. A significant decrease in carbon dioxide content of the arterial, pulmonary arterial and coronary sinus blood was observed, possibly as a consequence of hyperventilation. Khellin appeared to alter the metabolism of the myocardial and splanchnic tissues.

The role of α-adrenergic receptors in carbon monoxide hypoxia

1986 ◽  
Vol 64 (11) ◽  
pp. 1442-1446 ◽  
Author(s):  
S. M. Villeneuve ◽  
C. K. Chapler ◽  
C. E. King ◽  
S. M. Cain
Keyword(s):  
Carbon Monoxide ◽  
Blood Flow ◽  
Cardiac Output ◽  
Adrenergic Receptors ◽  
Muscle Blood Flow ◽  
Control Period ◽  
Arterial Oxygen ◽  
Adrenergic Blockade ◽  
Limb Blood Flow ◽  
Arterial Oxygen Content

The importance of α-adrenergic receptors in the cardiac output and peripheral circulatory responses to carbon monoxide (CO) hypoxia was studied in anesthetized dogs. Phenoxybenzamine (3 mg/kg i.v.) was injected to block α-receptor activity and the data obtained were then compared with those from a previous study of CO hypoxia in unblocked animals. Values for cardiac output, hindlimb blood flow, vascular resistance, and oxygen uptake were obtained prior to and at 30 and 60 min of CO hypoxia which reduced arterial oxygen content by approximately 50%. α-Adrenergic blockade resulted in a lower (p < 0.05) control value for cardiac output than observed in unblocked animals, but no differences were present between the two groups at 30 or 60 min of CO hypoxia. Similarly, limb blood flow was lower (p < 0.05) during the control period in the α-blocked group but rose to the same level as that in the unblocked animals at 60 min of COH. No change in limb blood flow occurred during CO hypoxia in the unblocked group. These findings demonstrated that during CO hypoxia (i) α-receptor mediated venoconstriction does not contribute to the cardiac output response and (ii) α-receptor mediated vasoconstriction probably does prevent a rise in hindlimb skeletal muscle blood flow.

Haemoglobin, Blood Volume, Cardiac Function, and Aerobic Power

1999 ◽  
Vol 24 (1) ◽  
pp. 54-65 ◽  
Author(s):  
Norman Gledhill ◽  
Darren Warburton ◽  
Veronica Jamnik
Keyword(s):  
Cardiac Output ◽  
Aerobic Power ◽  
Endurance Performance ◽  
Endurance Athletes ◽  
Aerobic Performance ◽  
Arterial Oxygen ◽  
Blood Doping ◽  
Arterial Oxygen Content ◽  
The Difference ◽  
Key Words Blood

Alterations in [Hb], which are mediated through changes in arterial oxygen content, and alterations in BV, which are mediated through changes in cardiac output [Formula: see text] have a significant effect on both [Formula: see text] and aerobic performance. If BV is held constant, a decrease in [Hb] (anaemia) causes a decrease in [Formula: see text] and aerobic performance, while an increase in [Hb] (blood doping) causes an increase in [Formula: see text] and aerobic performance. If [Hb] is held constant, an increase in BV can cause an increase in both [Formula: see text] and aerobic performance, while a decrease in BV can cause a decrease in both [Formula: see text] and aerobic performance. In addition, an increase in BV can compensate for moderate reductions in [Hb] through increases in [Formula: see text], allowing [Formula: see text] to remain unchanged or even increase. Also, a large portion of the difference in the enhanced cardiovascular function of endurance athletes is due to their high BV and the resultant enhancement of diastolic function. Hence, optimizing both [Hb] and BV is a very important consideration for endurance performance. Key words: blood doping, sport anemia, stroke volume

Dobutamine Pharmacokinetics and Cardiovascular Responses in Critically Ill Neonates

PEDIATRICS ◽  
1992 ◽  
Vol 89 (1) ◽  
pp. 47-51
Author(s):  
Alma M. Martinez ◽  
Jamés F. Padbury ◽  
Siang Thio
Keyword(s):  
Cardiac Output ◽  
Critically Ill ◽  
Cardiovascular Responses ◽  
Threshold Value ◽  
Constant Infusion ◽  
Plasma Catecholamine ◽  
First Order Kinetics ◽  
Critically Ill Neonates ◽  
The Mean ◽  
Cardiac Output Measurements

The pharmacokinetics and pharmacodynamics of dobutamine were studied in 13 critically ill neonates requiring inotropic support. Dobutamine was administered as a constant infusion in increasing doses of 2.5, 5, and 7.5 µg/kg per minute. During dobutamine infusions, there were significant increases in cardiac output measurements above preinfusion values. There were no statistically significant changes in systolic or diastolic blood pressure or heart rate during the infusions. The mean calculated threshold value, or the minimum plasma concentration necessary for a change in cardiac output, was 39±8 ng/mL. The mean plasma clearance rate was 90±38 mL/min per kilogram and was most consistent with first-order kinetics over the range of dosages studied. Plasma catecholamine levels were unchanged during the dobutamine infusions. These data suggest that dobutamine is an effective but limited inotropic agent in the neonate. Dobutamine may be most beneficial when cardiogenic failure is present.

CARDIOVASCULAR RESPONSES IN DOGS TO LARGE INTRAVENOUS INFUSIONS

1954 ◽  
Vol 32 (3) ◽  
pp. 282-292 ◽  
Author(s):  
C. W. Gowdey ◽  
J. D. Hatcher ◽  
F. A. Sunahara
Keyword(s):  
Cardiac Output ◽  
Peripheral Blood ◽  
Cardiovascular Responses ◽  
Blood Flows ◽  
Gum Acacia ◽  
Cardiac Decompensation ◽  
Arterial Blood ◽  
Anesthetized Dogs ◽  
The Mean ◽  
Slow Intravenous Infusion

The effects of a continuous, slow, intravenous infusion of gum acacia solution have been measured in anesthetized dogs. When the volume of the circulation was increased and the hematocrit value reduced, the cardiac output, intracardiac pressures, and peripheral blood flows began to increase. In some experiments these changes continued until sudden cardiac decompensation occurred during which the arterial blood pressure, cardiac output, and peripheral blood flows were reduced while the mean right auricular and ventricular pressures increased markedly. Analysis of the results indicates that up to the time of the highest cardiac output there is a closer correlation between cardiac output and hematocrit value than between cardiac output and mean right auricular pressure.

Acute intracranial hypertension and brain-stem blood flow

1984 ◽  
Vol 60 (3) ◽  
pp. 566-571 ◽  
Author(s):  
Seigo Nagao ◽  
Norio Sunami ◽  
Takumi Tsutsui ◽  
Yutaka Honma ◽  
Fumiyuki Momma ◽  
...  
Keyword(s):  
Blood Flow ◽  
Intracranial Hypertension ◽  
Brain Stem ◽  
Inferior Colliculus ◽  
Medulla Oblongata ◽  
Systemic Arterial Pressure ◽  
Content Type ◽  
Cushing Response ◽  
The Mean ◽  
Mass Lesions

✓ This study has been carried out to evaluate the effect of supratentorial mass lesions on the local cerebral blood flow (CBF) of the brain stem. Local CBF of the thalamus, inferior colliculus, and medulla oblongata, and supra- and infratentorial pressure were serially measured in 52 cats with intracranial hypertension produced by supratentorial balloon expansion. The mean control local CBF's in the thalamus, inferior colliculus, and medulla oblongata were 37.5, 42.1, and 30.7 ml/100 gm/min, respectively. At 20 to 30 mm Hg of supratentorial pressure, the local CBF of the thalamus started to decrease, and at 20 mm Hg of infratentorial pressure, the local CBF of the inferior colliculus began to decrease. Finally, at 40 to 60 mm Hg of infratentorial pressure, the local CBF of the medulla oblongata was affected. At the beginning of uncal herniation, indicated by anisocoria, the mean local CBF of the inferior colliculus abruptly decreased from 33.7 to 19.6 ml/100 gm/min in 16 cats. The Cushing response was evoked at a mean supratentorial pressure of 93.4 mm Hg and infratentorial pressure of 49.9 mm Hg in 16 cats. When the systemic arterial pressure was increased to the highest level in 13 cats, the mean local CBF of the medulla oblongata did not show significant change (a decrease from 22.8 to 20.9 ml/100 gm/min). The results suggest that at the beginning of uncal herniation, the local CBF of the upper brain stem markedly decreased. During the Cushing response, the local CBF of the medulla oblongata did not change significantly.

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