-
1.
Insulin-mediated muscle microvascular perfusion and its phenotypic predictors in humans.
Love, KM, Jahn, LA, Hartline, LM, Patrie, JT, Barrett, EJ, Liu, Z
Scientific reports. 2021;(1):11433
Abstract
Insulin increases muscle microvascular perfusion and enhances tissue insulin and nutrient delivery. Our aim was to determine phenotypic traits that foretell human muscle microvascular insulin responses. Hyperinsulinemic euglycemic clamps were performed in 97 adult humans who were lean and healthy, had class 1 obesity without comorbidities, or controlled type 1 diabetes without complications. Insulin-mediated whole-body glucose disposal rates (M-value) and insulin-induced changes in muscle microvascular blood volume (ΔMBV) were determined. Univariate and multivariate analyses were conducted to examine bivariate and multivariate relationships between outcomes, ΔMBV and M-value, and predictor variables, body mass index (BMI), total body weight (WT), percent body fat (BF), lean body mass, blood pressure, maximum consumption of oxygen (VO2max), plasma LDL (LDL-C) and HDL cholesterol, triglycerides (TG), and fasting insulin (INS) levels. Among all factors, only M-value (r = 0.23, p = 0.02) and VO2max (r = 0.20, p = 0.047) correlated with ΔMBV. Conversely, INS (r = - 0.48, p ≤ 0.0001), BF (r = - 0.54, p ≤ 0.001), VO2max (r = 0.5, p ≤ 0.001), BMI (r = - 0.40, p < 0.001), WT (r = - 0.33, p = 0.001), LDL-C (r = - 0.26, p = 0.009), TG (r = - 0.25, p = 0.012) correlated with M-value. While both ΔMBV (p = 0.045) and TG (p = 0.03) provided significant predictive information about M-value in the multivariate regression model, only M-value was uniquely predictive of ΔMBV (p = 0.045). Thus, both M-value and VO2max correlated with ΔMBV but only M-value provided unique predictive information about ΔMBV. This suggests that metabolic and microvascular insulin responses are important predictors of one another, but most metabolic insulin resistance predictors do not predict microvascular insulin responses.
-
2.
Phlebotomy eliminates the maximal cardiac output response to six weeks of exercise training.
Bonne, TC, Doucende, G, Flück, D, Jacobs, RA, Nordsborg, NB, Robach, P, Walther, G, Lundby, C
American journal of physiology. Regulatory, integrative and comparative physiology. 2014;(10):R752-60
Abstract
With this study we tested the hypothesis that 6 wk of endurance training increases maximal cardiac output (Qmax) relatively more by elevating blood volume (BV) than by inducing structural and functional changes within the heart. Nine healthy but untrained volunteers (Vo2max 47 ± 5 ml·min(-1)·kg(-1)) underwent supervised training (60 min; 4 times weekly at 65% Vo2max for 6 wk), and Qmax was determined by inert gas rebreathing during cycle ergometer exercise before and after the training period. After the training period, blood volume (determined in duplicates by CO rebreathing) was reestablished to pretraining values by phlebotomy and Qmax was quantified again. Resting echography revealed no structural heart adaptations as a consequence of the training intervention. After the training period, plasma volume (PV), red blood cell volume (RBCV), and BV increased (P < 0.05) by 147 ± 168 (5 ± 5%), 235 ± 64 (10 ± 3%), and 382 ± 204 ml (7 ± 4%), respectively. Vo2max was augmented (P < 0.05) by 10 ± 7% after the training period and decreased (P < 0.05) by 8 ± 7% with phlebotomy. Concomitantly, Qmax was increased (P < 0.05) from 18.9 ± 2.1 to 20.4 ± 2.3 l/min (9 ± 6%) as a consequence of the training intervention, and after normalization of BV by phlebotomy Qmax returned to pretraining values (18.1 ± 2.5 l/min; 12 ± 5% reversal). Thus the exercise training-induced increase in BV is the main mechanism increasing Qmax after 6 wk of endurance training in previously untrained subjects.
-
3.
Hemodynamic effects of volume expansion in patients with cardiac tamponade.
Sagristà-Sauleda, J, Angel, J, Sambola, A, Permanyer-Miralda, G
Circulation. 2008;(12):1545-9
Abstract
BACKGROUND Volume expansion has been proposed as an alternative treatment for cardiac tamponade; however, the scientific evidence for this recommendation is very poor. METHODS AND RESULTS Forty-nine unselected patients (23 males; age 55+/-16 years) with large pericardial effusion and hemodynamic tamponade underwent fluid overload with intravenous administration of 500 mL of normal saline over 10 minutes. Cardiac index and intrapericardial, left ventricular end-diastolic, right atrial, and right ventricular end-diastolic pressures were measured during basal state (tamponade), after fluid overload, and after pericardiocentesis. Twenty-eight patients (57%) had physical signs of tamponade, and 10 (20%) were hypotensive. Size of pericardial effusion was 31+/-13 mm. Initial mean arterial pressure was 88+/-21 mm Hg, and cardiac index was 2.46+/-0.80 L x min(-1) x m(-2). Intrapericardial pressure was 8.31+/-5.98 mm Hg. Volume expansion caused a significant increase in mean arterial pressure (from 88+/-21 to 94+/-23 mm Hg, P=0.003) and cardiac index (from 2.46+/-0.80 to 2.64+/-0.68 L x min(-1) x m(-2), P=0.013), as well as in intrapericardial pressure (from 8.31+/-5.98 to 11.02+/-6.27 mm Hg, P=0.0001), right atrial pressure (from 9.76+/-5.91 to 12.82+/-6.34 mm Hg, P=0.0001), and left ventricular end-diastolic pressure (from 14.21+/-5.97 to 19.48+/-6.19 mm Hg, P=0.0001). Cardiac index increased by >10% in 23 patients (47%), remained unchanged in 11 (22%), and decreased in 15 (31%). No patient developed clinical complications. Predictors of this favorable response were systolic blood pressure <100 mm Hg and low cardiac index. CONCLUSIONS Approximately one half of patients with cardiac tamponade develop a significant increase in cardiac output after volume overload. Low systolic blood pressure (<100 mm Hg) at baseline was the simplest clinical finding that was predictive of this favorable response.
-
4.
The influence of hydration status on stress-induced hemoconcentration.
Veldhuijzen van Zanten, JJ, Thrall, G, Wasche, D, Carroll, D, Ring, C
Psychophysiology. 2005;(1):98-107
Abstract
This study examined the effects of hydration status on rheological and hemodynamic activity during rest, mental stress, postural stress, and combined mental/postural stress in 24 men when euhydrated and hyperhydrated. The stress tasks elicited hemoconcentration, although the effects were less pronounced during mental stress. Hyperhydration was associated with higher plasma volume throughout. All stress tasks also perturbed hemodynamic activity, irrespective of hydration status, with the exception of heart rate reactivity, which was attenuated when hyperhydrated. As expected the combined stress during euhydration was associated with an unfavorable rheological and cardiovascular profile, which may help explain the increased incidence of cardiovascular events in the morning.
-
5.
Cold-water acclimation does not modify whole-body fluid regulation during subsequent cold-water immersion.
Stocks, JM, Patterson, MJ, Hyde, DE, Jenkins, AB, Mittleman, KD, Taylor, NA
European journal of applied physiology. 2004;(1-2):56-61
Abstract
We investigated the impact of cold-water acclimation on whole-body fluid regulation using tracer-dilution methods to differentiate between the intracellular and extracellular fluid compartments. Seven euhydrated males [age 24.7 (8.7) years, mass 74.4 (6.4) kg, height 176.8 (7.8) cm, sum of eight skinfolds 107.4 (20.4) mm; mean (SD)] participated in a 14-day cold-water acclimation protocol, with 60-min resting cold-water stress tests [CWST; 18.1 (0.1) degrees C] on days 1, 8 and 15, and 90-min resting cold-water immersions [18.4 (0.4) degrees C] on intervening days. Subjects were immersed to the 4th intercostal space. Intracellular and extracellular fluid compartments, and plasma protein, electrolyte and hormone concentrations were investigated. During the first CWST, the intracellular fluid (5.5%) and plasma volumes were reduced (6.1%), while the interstitial fluid volume was simultaneously expanded (5.4%). This pattern was replicated on days 8 and 15, but did not differ significantly among test days. Acclimation did not produce significant changes in the pre-immersion distribution of total body water, or changes in plasma osmolality, total protein, electrolyte, atrial natriuretic peptide or aldosterone concentrations. Furthermore, a 14-day cold-water acclimation regimen did not elicit significant changes in body-fluid distribution, urine production, or the concentrations of plasma protein, electrolytes or the fluid-regulatory hormones. While acclimation trends were not evident, we have confirmed that fluid from extravascular cells is displaced into the interstitium during acute cold-water immersion, both before and after cold acclimation.
-
6.
Hormonal changes during long-term isolation.
Custaud, MA, Belin de Chantemele, E, Larina, IM, Nichiporuk, IA, Grigoriev, A, Duvareille, M, Gharib, C, Gauquelin-Koch, G
European journal of applied physiology. 2004;(5-6):508-15
Abstract
Confinement and inactivity induce considerable psychological and physiological modifications through social and sensory deprivation. The aim of the SFINCSS-99 experiment was to determine the cardiovascular and hormonal pattern of blood volume regulation during long-term isolation and confinement. Simulation experiments were performed in pressurized chambers similar in size to the volumes of modern space vehicles. Group I consisted of four Russian male volunteers, who spent 240 days in a 100-m(3 )chamber. Group II included four males (one German and three Russians) who spent 110 days in isolation (200-m(3) module). The blood samples, taken before, during and after the isolation period, were used to determine haematocrit (Ht), growth hormone (GH), active renin, aldosterone, and osmolality levels. From the urine samples, electrolytes, osmolality, nitrites, nitrates, cortisol, antidiuretic hormone (ADH), aldosterone, normetanephrine and metanephrine levels were determined. The increase in plasma volume (PV) that is associated with a tendency for a decrease in plasma active renin is likely to be due to decreased sympathetic activity, and concords with the changes in urinary catecholamine levels during confinement. Urinary catecholamine levels were significantly higher during the recovery period than during confinement. This suggests that the sympathoadrenal system was activated, and concords with the increase in heart rate. Vascular resistance is determined by not only the vasoconstrictor but also vasodilator systems. The ratio of nitrite/nitrate in urine, as an indicator of nitric oxide release, did not reveal any significant changes. Analysis of data suggests that the duration of the isolation was a main factor involved in the regulation of hormones.
-
7.
Effects of tilting and volume loading on plasma levels and urinary excretion of relaxin, NT-pro-ANP, and NT-pro-BNP in male volunteers.
Heringlake, M, Heide, C, Bahlmann, L, Eichler, W, Pagel, H, Schmucker, P, Wergeland, R, Armbruster, FP, Klaus, S
Journal of applied physiology (Bethesda, Md. : 1985). 2004;(1):173-9
Abstract
The polypeptide relaxin (RLX) has been suggested to play a role in cardiorenal integration and to be related to the natriuretic peptide system. We hence examined the effects of variations in thoracic blood volume and intravenous volume loading on plasma and urinary RLX levels and associated changes in natriuretic peptide levels in healthy men. Two groups of eight subjects were randomly tilted into a 15 degrees feet-down or a 15 degrees head-down position. Ten volunteers were crossover subjected to an infusion of 15 ml/kg of 0.9% NaCl (over 60 min) or control during an observation period of 10 h. Blood and urine were sampled at timed intervals. RLX, NH(2)-terminal prohormones of atrial natriuretic peptide (NT-pro-ANP), and NH(2)-terminal prohormones of brain natriuretic peptide (NT-pro-BNP) were determined by enzyme, radio-, and electrochemoluminescence immunoassays, respectively. NT-pro-ANP levels (in percentage of baseline levels) were higher (P < 0.05) during the head-down (124 +/- 13%) than during the feet-down position (82 +/- 6%). NT-pro-BNP and RLX were not affected by tilting. Volume loading induced a short-lasting increase in plasma NT-pro-ANP, a delayed increase in plasma NT-pro-BNP, had no effect on plasma RLX, and induced a parallel increase in urine flow, renal excretion of sodium, RLX, and NT-pro-BNP. It is concluded that variations in thoracic blood volume in healthy men are not associated with variations in plasma RLX. Increased urinary RLX and NT-pro-BNP excretion during volume loading suggest renal production and a possible role of kidney-derived RLX and brain natriuretic peptide in sodium homeostasis in men.
-
8.
Plasma fatty acids response to central volume expansion in salt-sensitive hypertension.
Coruzzi, P, Brambilla, L, Brambilla, V, Gualerzi, M, Parati, G, Di Rienzo, M, Zanardi, E, Novarini, A
Metabolism: clinical and experimental. 2003;(4):508-13
Abstract
The purpose of the present study was to investigate the possible regulation of plasma fatty acids by an acute isotonic-isooncotic central volume expansion. We measured the levels of nonesterified fatty acids (NEFA) in plasma from 12 essential hypertensive patients subjected to water immersion (WI). Central hypervolemia by WI over 2 hours caused the levels of most NEFA to increase, concomitantly with a marked natriuretic and kaliuretic response. With respect to baseline values, serum insulin levels did not change during WI, while there was a profound suppression of plasma renin activity (PRA) and plasma aldosterone. In addition, when individual NEFA percent increase was expressed as a function of salt-sensitivity index (calculated as the change in mean arterial pressure [MAP] divided by the change in urinary sodium excretion rate), a greater percent increase in stearic acid (r =.72, P <.009), palmitic acid (r =.83, P <.001), and palmitoleic acid (r =.58, P <.048) was found during WI in those hypertensive subjects showing higher salt-sensitivity index. Thus, by demonstrating that an acute isotonic-isooncotic volume expansion may induce a significant increase of most NEFA plasma levels, we suggest that volume expansion per se could be included among the well-recognized risk factors for cardiovascular morbid events.
-
9.
The effects of hydration on core temperature in pediatric surgical patients.
Ezri, T, Szmuk, P, Weisenberg, M, Serour, F, Gorenstein, A, Sessler, DI
Anesthesiology. 2003;(4):838-41
-
-
Free full text
-
Abstract
BACKGROUND Reduced vascular volume might influence body temperature by diverting heat flow from peripheral tissues to the central organs. We therefore tested the hypothesis that mild hypovolemia helps to prevent intraoperative hypothermia in pediatric patients. METHODS Twenty-two pediatric patients (aged 1-3 yr) undergoing prolonged minor surgery were randomly assigned to conservative (n = 12) or aggressive (n = 10) perioperative fluid management. The conservative group fasted 8 h before surgery and received a crystalloid at 1 ml. kg-1. h-1 during surgery. The aggressive group was allowed to drink liquids until 3 h before surgery and was given a maintenance crystalloid at 8 ml. kg-1. h-1. Anesthesia was induced and maintained with halothane in nitrous oxide. Ambient temperature was kept near 25 degrees C, but the patients were not actively warmed. During recovery from anesthesia, additional fluid was given to the conservative group so that perioperative fluid totaled 9.5 ml. kg-1. h-1 in both groups. RESULTS Intraoperative body weight remained unchanged in the aggressive group and decreased only 1% in patients managed conservatively. Heart rate was slightly greater in the conservative group (107 +/- 9 vs. 95 +/- 4 beats/min, P = 0.002), but blood pressure was similar. Esophageal temperature in patients whose fluid was managed conservatively increased significantly, by 0.4 +/- 0.3 degrees C, to 37.1 degrees C; in contrast, temperature in the aggressive group decreased significantly, by 0.4 +/- 0.2 degrees C, to 36.4 degrees C (P < 0.001 between groups). Temperatures remained significantly different 1 h after surgery. CONCLUSIONS Conservative fluid management, which decreased body weight by only 1%, prevented reduction in core body temperature, presumably by reducing dissipation of metabolic heat from the core thermal compartment to peripheral tissues.
-
10.
Potassium supplementation improves the natriuretic response to central volume expansion in primary aldosteronism.
Coruzzi, P, Gualerzi, M, Parati, G, Brambilla, L, Brambilla, V, Di Rienzo, M, Novarini, A
Metabolism: clinical and experimental. 2003;(12):1597-600
Abstract
Potassium depletion induced by dietary potassium restriction is known to cause sodium retention, while potassium supplementation is known to increase urinary sodium excretion. However, the ability of potassium deficiency to affect mineralocorticoid-induced sodium retention in aldosterone-producing adenoma (APA) subjects has not been extensively investigated, neither in baseline conditions nor when facilitating natriuresis through a physiological manoeuver such as central blood volume expansion. With the aim of testing the hypothesis that potassium supplementation would attenuate the mineralocorticoid-induced sodium retention, in 7 APA patients elevation of serum potassium was obtained by infusion of isosmotic potassium chloride (KCl) at a constant rate of 36 mmol/h for a 2-hour period for 5 consecutive days. The same patients were also submitted to acute central volume expansion by head-out water immersion (WI) associated with either low or normal serum potassium levels. The assessment of natriuresis in baseline condition and during WI was also performed in 10 age-matched control subjects. Central hypervolemia by WI induced a significant natriuretic response in APA hypokalemic subjects; on the other hand, in the same APA subjects giving potassium supplementation, WI-induced urinary sodium excretion was significantly higher (P <.001) than that obtained during WI at normal potassium intake (hypokalemic condition). Blood pressure responses and hormonal profiles were almost superimposable during the 2 WI experiments performed at different serum potassium levels. By confirming that amelioration of hypokalemia attenuates mineralocorticoid-induced sodium retention, this study also suggests that potassium intake may represent an important determinant of mineralocorticoid escape.