Central venous pressure and plasma arginine vasopressin during water immersion in man

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.

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Reflex control of osmotically stimulated vasopressin in normal humans

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1985.248.6.r660 ◽

1985 ◽

Vol 248 (6) ◽

pp. R660-R663 ◽

Cited By ~ 1

Author(s):

S. R. Goldsmith ◽

A. W. Cowley ◽

G. S. Francis ◽

J. N. Cohn

Keyword(s):

Central Venous Pressure ◽

Hypertonic Saline ◽

Lower Body Negative Pressure ◽

Venous Pressure ◽

Control Mechanisms ◽

Central Venous ◽

Time Control ◽

Osmotic Stimulation ◽

Normal Humans ◽

Plasma Arginine

Previous studies have shown that in normal humans plasma arginine vasopressin (AVP) does not increase in response to unloading of cardiopulmonary and sinoaortic baroreceptors produced by lower body negative pressure (LBNP) unless hypotension occurs. To assess whether prior osmotic stimulation of AVP might bring out latent sensitivity to nonosmotic control mechanisms in humans we studied the response of plasma AVP to graded LBNP after a 105-min infusion of 5% saline in a group of eight normal individuals. During the infusion and before LBNP, serum osmolality increased from 288 +/- 9 to 300 +/- 10 mosmol/kg, and plasma AVP increased from 4.4 +/- 1.7 to 8.0 +/- 2.5 pg/ml. Neither osmolality nor AVP changed significantly during two stages of LBNP that first reduced central venous pressure alone and then reduced central venous pressure with accompanying tachycardia and narrowing of the pulse pressure. Time control studies performed in five individuals subjected to central venous catheterization and an identical hypertonic saline infusion failed to show significant spontaneous changes in AVP during a comparable interval after the infusions but without LBNP. Thus osmotic stimulation with hypertonic saline did not render AVP more sensitive to nonhypotensive unloading of cardiopulmonary and sinoaortic baroreceptors in normal humans.

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Arginine vasopressin, circulation, and kidney during graded water immersion in humans

Journal of Applied Physiology ◽

10.1152/jappl.1986.61.2.565 ◽

1986 ◽

Vol 61 (2) ◽

pp. 565-574 ◽

Cited By ~ 24

Author(s):

P. Norsk ◽

F. Bonde-Petersen ◽

J. Warberg

Keyword(s):

Arginine Vasopressin ◽

Water Immersion ◽

Venous Pressure ◽

Free Water ◽

Systolic Arterial Pressure ◽

Free Water Clearance ◽

Plasma Arginine ◽

Normal Males ◽

Solute Excretion ◽

Rebreathing Method

Ten normal males rested sitting upright at an air temperature of 28 degrees C for 5.5 h (control, C) and underwent 4 h of graded water immersion (WI) to the umbilicus (UI), to the chest (CI), and to the neck (NI), respectively (water temperature = 34.5 degrees C), on different experimental days. Plasma arginine vasopressin (PAVP) was suppressed during WI compared with C and maximally so during NI. However, there was no change in PAVP comparing CI with UI even though central venous pressure (CVP) increased. CVP increased during CI and NI compared with C but was unchanged during UI, whereas cardiac output (rebreathing method), stroke volume, and plasma volume increased to approximately the same level during all three steps of WI compared with C. Heart rate and total peripheral vascular resistance decreased during UI, CI, and NI. Systolic arterial pressure (SAP) and pulse pressure (PP) were increased gradually from prestudy related to the degree of WI. Also diuresis, natriuresis, kaliuresis, osmotic excretion, and clearance were increased gradually compared with C, whereas free water clearance (CH2O) gradually decreased. There were weak negative but statistically significant correlations between PAVP and CVP and between changes in PAVP from prestudy and corresponding changes in SAP and PP. Furthermore, a statistically significant and negative correlation between CH2O and natriuresis could be established. We conclude that graded immersion gradually increases central blood volume and decreases PAVP. However, not only cardiopulmonary mechanoreceptors but also arterial baroreceptors may play a role in AVP suppression during WI in humans. In hydropenic subjects the suppression of PAVP during WI is apparently not effective in counteracting the decrease in CH2O induced by increased solute excretion.

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