Cardiovascular and renal effects of head-out water immersion in man: application of the model in the assessment of volume homeostasis

Aerobic Exercise in the Aquatic Environment Suppresses the Plasma Renin Activity in Individuals with Type 2 Diabetes: A Secondary Analysis of a Randomized Clinical Trial

To compare the acute effects of aquatic walking/running versus dry-land walking/running on blood glucose and plasma renin activity (PRA) in individuals with type 2 diabetes, participants with type 2 diabetes performed deep-water or dry-land walking and/or running sessions in a swimming pool or on an athletics track, respectively. Both sessions comprised seven blocks of 3 min at 85-90% of the heart rate deflection point (HRDP), interspersed with 2 min at <85% HRDP, totaling 35 min, with a 48 h interval between sessions. PRA and blood glucose were assessed before and immediately after the sessions. Generalized estimation equations were used to verify the session effects, with the Bonferroni post hoc test, considering the significance level as 0.05. Twelve individuals (53.2 ± 8.9 years) diagnosed with type 2 diabetes for 6.3 ± 6.34 years participated in the study. A reduction in PRA was found only after the aquatic session (-7.75 ng/mL/h; -69%; p: 0.034), while both aquatic and dry-land sessions similarly reduced the blood glucose levels (aquatic: -38 mg/dL, -21%; dry-land: -26 mg/dL, -14%; time effect, p = 0.007). Despite yielding similar glycemic reductions as dry-land walking/running, aquatic walking/running led to an expressive decrease in PRA among individuals with type 2 diabetes.

Effects of aquatic and land high intensity interval training on hemodynamics and vascular function of middle-aged men

Objective: To investigate the effects of 8-week aquatic and land high intensity interval training (HIIT) on hemodynamics and vascular function in middle-aged men. Methods: Thirty middle-aged men with low physical activity were selected and divided into 15 men (52.43 ± 4.11) in aquatic group and 15 men (52.74 ± 5.62) in land group by random number table. They performed HIIT exercise in aquatic and land 3 times a week for 8 weeks. Pre-test, inter-test and post-test respectively measure hemodynamics and blood vessel function. Results: (1) Body composition: After 8 weeks of exercise, weight, body mass index (BMI) and body fat rate (BF) were lower than before exercise (aquatic group: p < 0.01, land group: p < 0.05). The improvement of BF in the aquatic group was better than that in the land group (p < 0.05); (2) Cardiac function: After 8 weeks of exercise, stroke volume (SV), left ventricular end-diastolic volume (EDV), cardiac output (CO), and left ventricular fractional shortening (FS), were higher than before exercise (aquatic group: p < 0.01, land group: p < 0.05), heart rate (HR) and left ventricular end-systolic volume (ESV) were lower than before exercise (aquatic group: p < 0.01, land group: p < 0.05). The improvement of SV, HR, EDV, ESV, CO and FS in the aquatic group was better than that in the land group (p < 0.05); (3) Hemodynamics: After 8 weeks of exercise, systolic blood pressure (SBP), diastolic blood pressure (DBP) were lower than before exercise (aquatic group: p < 0.01, land group: p < 0.05), wall shear stress (WSS) and peak systolic velocity (PSV) were higher than before exercise (aquatic group: p < 0.01, land group: p < 0.05). The improvement of SBP, WSS and PSV in the aquatic group was better than that in the land group (p < 0.05); (4) Vascular function: basal diameter and brachial artery flow-mediated dilatation (FMD) level in aquatic group and land group was higher than before exercise, pulse wave velocity (PWV) level was lower than before exercise (aquatic and land group: p < 0.05). The improvement of FMD in the aquatic group was better than that in the land group. Conclusion: The body composition, hemodynamics and vascular function of middle-aged men were improved by 8-week aquatic and land HIIT. Aquatic HIIT has better effect on body fat rate, hemodynamics and vascular endothelial function in middle-aged men due to the effect of aquatic pressure and temperature.

Effects of aquatic exercise intervention on executive function and brain-derived neurotrophic factor of children with autism spectrum disorder

BACKGROUND

Limited knowledge exists regarding the effectiveness of aquatic exercise intervention for improving executive function (EF) in children with autism spectrum disorder (ASD). Additionally, the impact of aquatic exercise on brain-derived neurotrophic factor (BDNF) in children with ASD requires further investigation.

AIMS

This study aimed to explore the effects of a 12-week aquatic exercise intervention on core EF and BDNF levels in children with ASD.

METHODS AND PROCEDURES

Thirty children with ASD were assigned to an experimental or control group. The experimental group underwent a 12-week aquatic exercise intervention, while the control group engaged in supervised free activities. Pre- and post-intervention assessments measured EF and BDNF levels.

OUTCOMES AND RESULTS

The experimental group showed significant improvements (p < 0.05) in inhibition control, cognitive flexibility, and BDNF levels. However, working memory did not significantly improve. The control group exhibited no significant changes in EF or BDNF levels.

CONCLUSIONS AND IMPLICATIONS

Aquatic exercise appears to be a beneficial intervention for cognitive development in children with ASD, as it enhances inhibition control, cognitive flexibility, and BDNF levels in children with ASD. Furthermore, the observed improvements in EF following aquatic exercise intervention in children with ASD may be associated with increased BDNF levels.

The effect of a single closed-circuit rebreather decompression dive in extremely cold water to cardiac function

PURPOSE

Dive-induced cardiac and hemodynamic changes are caused by various mechanisms, and they are aggravated by cold water. Therefore, aging divers with pre-existing cardiovascular conditions may be at risk of acute myocardial infarction, heart failure, or arrhythmias while diving. The aim of this study was to assess the effect of a single decompression CCR dive in arctic cold water on cardiac function in Finnish technical divers.

METHODS

Thirty-nine divers performed one identical 45 mfw CCR dive in 2-4 °C water. Hydration and cardiac functions were assessed before and after the dive. Detection of venous gas embolization was performed within 120 min after the dive.

RESULTS

The divers were affected by both cold-water-induced hemodynamic changes and immersion-related fluid loss. Both systolic and diastolic functions were impaired after the dive although the changes in cardiac functions were subtle. Venous inert gas bubbles were detected in all divers except for one. Venous gas embolism did not affect systolic or diastolic function.

CONCLUSION

A single trimix CCR dive in arctic cold water seemed to debilitate both systolic and diastolic function. Although the changes were subtle, they appeared parallel over several parameters. This indicates a real post-dive deterioration in cardiac function instead of only volume-dependent changes. These changes are without a clinical significance in healthy divers. However, in a population with pre-existing or underlying heart problems, such changes may provoke symptomatic problems during or after the dive.

Aquatic training improves HbA1c, blood pressure and functional outcomes of patients with type 2 diabetes: A systematic review with meta-analysis

AIM

This study aimed to summarize the effects of aquatic training on the health outcomes of type 2 diabetes (T2D) patients.

METHODS

This is a systematic review with meta-analysis that followed the PRISMA recommendations. Searches were performed in four databases in April 2021. The following eligibility criteria were adopted: adults with T2D; aquatic training (AT) intervention in an upright position; pre- and post-intervention assessments of the following outcomes: HbA1c, SBP and DBP, functional capacity, VO_2peak. The random-effects meta-analysis results are presented as mean differences and 95% confidence intervals.

RESULTS

Of the 375 studies, 12 studies were eligible and included in the meta-analysis. Favorable effects of AT post-intervention were observed in HbA1c (-0.62 %), VO_2peak (2.16 mL.Kg^-1.min^-1), SBP (-5.55 mmHg), DBP (-4.99 mmHg), and the 6-minute walk test (76.64 m). AT also revealed superior effects when compared to the control group (CG) and similar effects to land training (LT) in HbA1c (AT vs CG = -0.67 % and AT vs LT = -0.40 %), VO_2peak (AT vs CG = 3.78 mL.Kg^-1.min^-1; AT vs LT = -0.12 mL/Kg-1.min^-1), SBP (AT vs LT = -0.85 mmHg), and DBP (AT vs LT = 2.12 mmHg).

CONCLUSION

AT improves HbA1c, VO_2peak, SBP, DBP, and functional capacity in T2D patients. Beneficial effects favored AT over CG, while similar effects were verified between AT and LT on HbA1c, VO_2peak, and blood pressure.

Effects of aquatic high-intensity interval training and moderate-intensity continuous training on central hemodynamic parameters, endothelial function and aerobic fitness in inactive adults

Objective

The effects of land-based high-intensity interval training (HIIT) on the cardiovascular system have already been demonstrated. However, the water environment is different from that on land. Therefore, we investigated the effects of 6-week aquatic HIIT and moderate-intensity continuous training (MICT) on central hemodynamic parameters, endothelial function, and aerobic fitness in inactive adults.

Methods

Thirty-one inactive adults were randomly assigned to HIIT or MICT group. HIIT group performed twelve 30-s swimming exercise bouts with the intensity of 95% HR_max and 15-18/20 RPE with a 60-s rest period between each bout. MICT group performed a 30-min uninterrupted swimming exercise with the intensity of 70%-75% HR_max and 12-14/20 RPE. Training frequency for both groups was three times a week. The pulse wave analysis and flow-mediated dilation (FMD) were measured by non-invasive equipments.

Results

The aerobic fitness significantly increased after HIIT, but no change was seen after MICT. Augmentation pressure (AP) and augmentation index normalized at 75 bpm (AIx@HR75) significantly decreased after HIIT but not MICT, whereas MICT rather than HIIT improved subendocardial viability ratio (SEVR), central and peripheral blood pressure, and resting HR. Only HIIT significantly increased brachial endothelial function.

Conclusion

A six-week aquatic HIIT and MICT had no differences in hemodynamic parameters, endothelial function, and aerobic fitness, however 6 weeks of aquatic HIIT reduced arterial stiffness, increased endothelial function and aerobic fitness, while 6 weeks of aquatic MICT reduced arterial blood pressure and resting HR and increased the coronary blood flow reserve.

Hemoglobin During and Following a 4-Week Commercial Saturation Dive to 200 m

Commercial saturation divers must acclimatize to hyperbaric hyperoxia in their work environment, and subsequently readjust to breathing normal air when their period in saturation is over. In this study, we measured hemoglobin (Hb) during and following 4 weeks of heliox saturation diving in order to monitor anemia development and the time for Hb to recover post-saturation. Male commercial saturation divers reported their capillary blood Hb daily, before, and during 28 days of heliox saturation to a working depth of circa 200 m (n = 11), and for 12 days at surface post-saturation (n = 9–7), using HemoCue 201+ Hb devices. Hb remained in normal range during the bottom phase, but fell during the decompression; reaching levels of mild anemia (≤13.6 g/dl) the day after the divers’ return to the surface. Hb was significantly lower than the pre-saturation baseline (14.7 ± 1.1 g/dl) on the fifth day post-saturation (12.8 ± 1.8 g/dl, p = 0.028), before reverting to normal after 6–7 days. At the end of the 12-day post-saturation period, Hb was not statistically different from the pre-saturation baseline. The observed Hb changes, although significant, were modest. While we cannot rule out effect of other factors, the presence of mild anemia may partially explain the transient fatigue that commercial saturation divers experience post-saturation.

Swimming exercise demonstrates advantages over running exercise in reducing proteinuria and glomerulosclerosis in spontaneously hypertensive rats

Experimental studies in animal models have described the benefits of physical exercise (PE) to kidney diseases associated with hypertension. Land- and water-based exercises induce different responses in renal function. Our aim was to evaluate the renal alterations induced by different environments of PE in spontaneously hypertensive rats (SHRs). The SHRs were divided into sedentary (S), swimming exercise (SE), and running exercise (RE) groups, and were trained for 8 weeks under similar intensities (60 min/day). Arterial pressure (AP) and heart rate (HR) were recorded. The renal function was evaluated through urinary volume at each week of training; sodium and potassium excretions, plasma and urinary osmolarities, glomerular filtration rate (GFR), levels of proteinuria, and renal damage were determined. SE and RE rats presented reduced mean AP, systolic blood pressure, and HR in comparison with S group. SE and RE rats showed higher urine osmolarity compared with S. SE rats showed higher free water clearance (P < 0.01), lower urinary density (P < 0.0001), and increased weekly urine volume (P < 0.05) in comparison with RE and S groups. GFR was increased in both SE and RE rats. The proteinuria of SE (7.0 ± 0.8 mg/24 h) rats was decreased at the 8th week of the PE in comparison with RE (9.6 ± 0.8 mg/24 h) and S (9.8 ± 0.5 mg/24 h) groups. The glomerulosclerosis was reduced in SE rats (P < 0.02). SE produced different response in renal function in comparison with RE, in which only swimming-trained rats had better profile for proteinuria and glomerulosclerosis.

Aquatic Training in Upright Position as an Alternative to Improve Blood Pressure in Adults and Elderly: A Systematic Review and Meta-Analysis

BACKGROUND

Meta-analyses have shown that land training (LT) reduces blood pressure; however, it is not known whether aquatic training (AT) promotes this same effect.

OBJECTIVE

The aim was to conduct a meta-analysis on the effects of AT on systolic blood pressure (SBP) and diastolic blood pressure (DBP) in adults and elderly and compare them to those of LT and no training [control group (CG)].

DATA SOURCES

Embase, PubMed, Cochrane and Scopus were searched up to May 2017.

STUDY ELIGIBILITY CRITERIA

Studies that evaluated the effect of upright AT (i.e., AT performed in upright position) on the blood pressure of adult individuals and the elderly who did not present with cardiovascular disease (other than hypertension) were included.

DATA ANALYSIS

Two independent reviewers screened search results, performed data extraction and assessed risk of bias. Random effect was used, and the effect size (ES) was calculated by using the standardized mean difference with a 95% confidence interval.

RESULTS

AT promoted a reduction in SBP (ES - 1.47; 95% CI - 2.23 to - 0.70; p < 0.01) compared to CG. This effect is maintained with training progression (ES - 1.52; 95% CI - 2.70 to - 0.33; p = 0.01) and no progression (ES - 1.43; 95% CI - 2.64 to - 0.23; p = 0.02). These effects were significant only in hypertensive (ES - 2.20; 95% CI - 2.72 to - 1.68; p < 0.01), and not in pre-hypertensive individuals. AT promoted a decrease in DBP (- 0.92; 95% CI - 1.27 to - 0.57; p < 0.01) after training with progression (- 0.81; 95% CI - 1.62 to - 0.001; p = 0.04) and no progression (- 1.01; 95% CI - 1.40 to - 0.62; p < 0.01) in pre-hypertensive (- 1.12; 95% CI - 1.53 to - 0.70; p < 0.01) and hypertensive patients (- 0.69; 95% CI - 1.31 to - 0.06; p = 0.03). AT promoted similar reductions in SBP compared to LT; however, reduction of DBP in hypertensive patients was lower (1.82; 95% CI 0.84 to 2.79; p < 0.01).

CONCLUSION

AT promotes blood pressure reduction in adults and elderly. The reduction in SBP in those performing AT is similar to those performing LT, but reduction of DBP is lower in the AT group compared to that in the LT group.

SYSTEMATIC REVIEW REGISTRATION NUMBER

CRD42016049716.

Aqua walking as an alternative exercise modality during cardiac rehabilitation for coronary artery disease in older patients with lower extremity osteoarthritis

Background

The purpose of this study was to examine the effects of aqua walking (AW) on coronary artery disease (CAD) and cardiorespiratory fitness in older adults with osteoarthritis in the lower extremity and compare it with that of traditional over-ground walking.

Methods

Sixty consecutive eligible patients who had undergone percutaneous coronary intervention for CAD with limited ambulation due to lower extremity osteoarthritis were recruited. They were randomly assigned to the AW program group, treadmill/track walking (TW) program group, or non-exercise control group (CON). Assessments were performed before and after 24 weeks of medically supervised exercise training.

Results

Significant differences were observed in the change in %body fat (TW: −2.7%, AW: −2.8%, CON: −0.4%), total cholesterol level (TW: −23.6 mg/dL, AW: −27.2 mg/dL, CON: 15.8 mg/dL), resting heart rate (TW: −6.3 bpm, AW: −6.9 bpm, CON: 1.3 bpm), and cardiorespiratory fitness expressed as VO₂ peak (TW: 2.3 mL/kg·min⁻¹, AW: 2.0 mL/kg·min⁻¹, CON: −2.5 mL/kg·min⁻¹) over 24 weeks among the groups. However, no significant differences in the change in these measures were found between the TW and AW groups.

Conclusion

AW appears to be a feasible alternative exercise modality to over-ground walking for cardiac rehabilitation and can be recommended for older adults with CAD and osteoarthritis.

An acute bout of whole body passive hyperthermia increases plasma leptin, but does not alter glucose or insulin responses in obese type 2 diabetics and healthy adults

Acute and chronic hyperthermic treatments in diabetic animal models repeatedly improve insulin sensitivity and glycemic control. Therefore, the purpose of this study was to test the hypothesis that an acute 1h bout of hyperthermic treatment improves glucose, insulin, and leptin responses to an oral glucose challenge (OGTT) in obese type 2 diabetics and healthy humans. Nine obese (45±7.1% fat mass) type 2 diabetics (T2DM: 50.1±12y, 7.5±1.8% HbA1c) absent of insulin therapy and nine similar aged (41.1±13.7y) healthy non-obese controls (HC: 33.4±7.8% fat mass, P<0.01; 5.3±0.4% HbA1c, P<0.01) participated. Using a randomized design, subjects underwent either a whole body passive hyperthermia treatment via head-out hot water immersion (1h resting in 39.4±0.4°C water) that increased internal temperature above baseline by ∆1.6±0.4°C or a control resting condition. Twenty-four hours post treatments, a 75g OGTT was administered to evaluate changes in plasma glucose, insulin, C-peptide, and leptin concentrations. Hyperthermia itself did not alter area under the curve for plasma glucose, insulin, or C-peptide during the OGTT in either group. Fasting absolute and normalized (kg·fat mass) plasma leptin was significantly increased (P<0.01) only after the hyperthermic exposure by 17% in T2DM and 24% in HC groups (P<0.001) when compared to the control condition. These data indicate that an acute hyperthermic treatment does not improve glucose tolerance 24h post treatment in moderate metabolic controlled obese T2DM or HC individuals.

Saturation diving; physiology and pathophysiology

In saturation diving, divers stay under pressure until most of their tissues are saturated with breathing gas. Divers spend a long time in isolation exposed to increased partial pressure of oxygen, potentially toxic gases, bacteria, and bubble formation during decompression combined with shift work and long periods of relative inactivity. Hyperoxia may lead to the production of reactive oxygen species (ROS) that interact with cell structures, causing damage to proteins, lipids, and nucleic acid. Vascular gas-bubble formation and hyperoxia may lead to dysfunction of the endothelium. The antioxidant status of the diver is an important mechanism in the protection against injury and is influenced both by diet and genetic factors. The factors mentioned above may lead to production of heat shock proteins (HSP) that also may have a negative effect on endothelial function. On the other hand, there is a great deal of evidence that HSPs may also have a "conditioning" effect, thus protecting against injury. As people age, their ability to produce antioxidants decreases. We do not currently know the capacity for antioxidant defense, but it is reasonable to assume that it has a limit. Many studies have linked ROS to disease states such as cancer, insulin resistance, diabetes mellitus, cardiovascular diseases, and atherosclerosis as well as to old age. However, ROS are also involved in a number of protective mechanisms, for instance immune defense, antibacterial action, vascular tone, and signal transduction. Low-grade oxidative stress can increase antioxidant production. While under pressure, divers change depth frequently. After such changes and at the end of the dive, divers must follow procedures to decompress safely. Decompression sickness (DCS) used to be one of the major causes of injury in saturation diving. Improved decompression procedures have significantly reduced the number of reported incidents; however, data indicate considerable underreporting of injuries. Furthermore, divers who are required to return to the surface quickly are under higher risk of serious injury as no adequate decompression procedures for such situations are available. Decompression also leads to the production of endothelial microparticles that may reduce endothelial function. As good endothelial function is a documented indicator of health that can be influenced by regular exercise, regular physical exercise is recommended for saturation divers. Nowadays, saturation diving is a reasonably safe and well controlled method for working under water. Until now, no long-term impact on health due to diving has been documented. However, we still have limited knowledge about the pathophysiologic mechanisms involved. In particular we know little about the effect of long exposure to hyperoxia and microparticles on the endothelium.

Natriuretic hormones, endogenous ouabain, and related sodium transport inhibitors

The work of deWardener and colleagues stimulated longstanding interest in natriuretic hormones (NHs). In addition to the atrial peptides (APs), the circulation contains unidentified physiologically relevant NHs. One NH is controlled by the central nervous system (CNS) and likely secreted by the pituitary. Its circulating activity is modulated by salt intake and the prevailing sodium concentration of the blood and intracerebroventricular fluid, and contributes to postprandial and dehydration natriuresis. The other NH, mobilized by atrial stretch, promotes natriuresis by increasing the production of intrarenal dopamine and/or nitric oxide (NO). Both NHs have short (<35 min) circulating half lives, depress renotubular sodium transport, and neither requires the renal nerves. The search for NHs led to endogenous cardiotonic steroids (CTS) including ouabain-, digoxin-, and bufadienolide-like materials. These CTS, given acutely in high nanomole to micromole amounts into the general or renal circulations, inhibit sodium pumps and are natriuretic. Among these CTS, only bufalin is cleared sufficiently rapidly to qualify for an NH-like role. Ouabain-like CTS are cleared slowly, and when given chronically in low daily nanomole amounts, promote sodium retention, augment arterial myogenic tone, reduce renal blood flow and glomerular filtration, suppress NO in the renal vasa recta, and increase sympathetic nerve activity and blood pressure. Moreover, lowering total body sodium raises circulating endogenous ouabain. Thus, ouabain-like CTS have physiological actions that, like aldosterone, support renal sodium retention and blood pressure. In conclusion, the mammalian circulation contains two non-AP NHs. Identification of the CNS NH should be a priority.

Early aquatic physical therapy improves function and does not increase risk of wound-related adverse events for adults after orthopedic surgery: a systematic review and meta-analysis

OBJECTIVES

To investigate whether early postoperative aquatic physical therapy is a low-risk and effective form of physical therapy to improve functional outcomes after orthopedic surgery.

DATA SOURCES

Databases MEDLINE, CINAHL, AMED, Embase, and PEDro were searched from the earliest date available until October 2011. Additional trials were identified by searching reference lists and citation tracking.

STUDY SELECTION

Controlled trials evaluating the effects of aquatic physical therapy on adverse events for adults <3 months after orthopedic surgery. Two reviewers independently applied inclusion and exclusion criteria, and any disagreements were discussed until consensus could be reached. Searching identified 5069 potentially relevant articles, of which 8 controlled trials with 287 participants met inclusion criteria.

DATA EXTRACTION

A predefined data extraction form was completed in detail for each included study by 1 reviewer and checked for accuracy by another. Methodologic quality of included trials was assessed independently by 2 reviewers using the PEDro scale.

DATA SYNTHESIS

Pooled analyses were performed using random effects model with inverse variance methods to calculate standardized mean differences (SMDs) and 95% confidence intervals (CIs) (continuous outcomes) and risk difference and 95% CIs (dichotomous outcomes). When compared with land-based physical therapy, early aquatic physical therapy does not increase the risk of wound-related adverse events (risk difference=.01, 95% CI -.05 to .07) and results in improved performance of activities of daily living (SMD=.33, 95% CI=.07-.58, I(2)=0%). There were no significant differences in edema (SMD=-.27, 95% CI=-.81 to .27, I(2)=58%) or pain (SMD=-.06, 95% CI=-.50 to .38, I(2)=32%).

CONCLUSIONS

After orthopedic surgery aquatic physical therapy improves function and does not increase the risk of wound-related adverse events and is as effective as land-based therapy in terms of pain, edema, strength, and range of motion in the early postoperative period.

Role of dietary salt in hypertension

Certain things have not changed since my colleague and I last reviewed the role of dietary salt in hypertension [Haddy, F.J., Pamnani, M.B., 1995. Role of dietary salt in hypertension. Journal of the American College of Nutrition 14, 428-438]. Over half of hypertensives are still salt sensitive, i.e., they respond to a high NaCl intake with a rise in blood pressure. This can be ameliorated by restricting NaCl intake, supplementing potassium intake, and consuming diuretics. Some things have changed. We now have more insight into mechanism; we suspected that volume expansion and endogenous Na(+),K(+)-ATPase inhibitors were the connection between excessive salt intake and the hypertension, but we were not certain as to the nature of the inhibitors. Now it appears that the inhibitors are steroids released from the adrenal gland and are members of the cardenolide family, e.g., ouabain, and the bufadienolide family, e.g., marinobufagenin. This presents new possibilities in therapy, including antibodies to these agents and competitive inhibitors to their binding to Na(+),K(+)-ATPase.

Management of cirrhotic ascites: physiological basis of diuretic action

Ascites is a significant complication of cirrhosis that occurs in approximately 50% of patients. The mortality rate is high in patients with cirrhosis and ascites. Conventional interventions rest with dietary sodium restriction, diuretic use, large-volume paracentesis, peritoneovenous shunts and transjugular intrahepatic portosystemic shunts. The mainstay of therapy, however, is the judicious use of diuretics. This article reviews the physiological basis of diuretic use in patients with cirrhosis and ascites, as well as recent concepts on the pathogenesis of ascites formation. Through a better understanding of the pathophysiology of ascites formation and the mechanism of action of diuretics, improved extracellular fluid balance can be achieved in these patients.

Glycerol hyperhydration: physiological responses during cold-air exposure

Hypohydration occurs during cold-air exposure (CAE) through combined effects of reduced fluid intake and increased fluid losses. Because hypohydration is associated with reduced physical performance, strategies for maintaining hydration during CAE are important. Glycerol ingestion (GI) can induce hyperhydration in hot and temperate environments, resulting in greater fluid retention compared with water (WI) alone, but it is not effective during cold-water immersion. Water immersion induces a greater natriuresis and diuresis than cold exposure; therefore, whether GI might be effective for hyperhydration during CAE remains unknown. This study examined physiological responses, i.e., thermoregulatory, cardiovascular, renal, vascular fluid, and fluid-regulating hormonal responses, to GI in seven men during 4 h CAE (15°C, 30% relative humidity). Subjects completed three separate, double-blind, and counterbalanced trials including WI (37 ml water/l total body water), GI (37 ml water/l total body water plus 1.5 g glycerol/l total body water), and no fluid. Fluids were ingested 30 min before CAE. Thermoregulatory responses to cold were similar during each trial. Urine flow rates were higher ( P = 0.0001) with WI (peak 11.8 ml/min, SD 1.9) than GI (5.0 ml/min, SD 1.8), and fluid retention was greater ( P = 0.0001) with GI (34%, SD 7) than WI (18%, SD 5) at the end of CAE. Differences in urine flow rate and fluid retention were the result of a greater free water clearance with WI. These data indicate glycerol can be an effective hyperhydrating agent during CAE.

The physiology of deep-water running

Deep-water running is performed in the deep end of a swimming pool, normally with the aid of a flotation vest. The method is used for purposes of preventing injury and promoting recovery from strenuous exercise and as a form of supplementary training for cardiovascular fitness. Both stroke volume and cardiac output increase during water immersion: an increase in blood volume largely offsets the cardiac decelerating reflex at rest. At submaximal exercise intensities, blood lactate responses to exercise during deep-water running are elevated in comparison to treadmill running at a given oxygen uptake (VO2). While VO2, minute ventilation and heart rate are decreased under maximal exercise conditions in the water, deep-water running nevertheless can be justified as providing an adequate stimulus for cardiovascular training. Responses to training programmes have confirmed the efficacy of deep-water running, although positive responses are most evident when measured in a water-based test. Aerobic performance is maintained with deep-water running for up to 6 weeks in trained endurance athletes; sedentary individuals benefit more than athletes in improving maximal oxygen uptake. There is some limited evidence of improvement in anaerobic measures and in upper body strength in individuals engaging in deep-water running. A reduction in spinal loading constitutes a role for deep-water running in the prevention of injury, while an alleviation of muscle soreness confirms its value in recovery training. Further research into the applications of deep-water running to exercise therapy and athletes' training is recommended.

Abdominal decompression plays a major role in early postparacentesis haemodynamic changes in cirrhotic patients with tense ascites

BACKGROUND

Some cirrhotic patients with tense ascites who undergo paracentesis develop a circulatory dysfunction syndrome, manifested by an increase in plasma renin activity. Recently, a significant inverse correlation between postparacentesis changes in plasma renin activity and systemic vascular resistance has been demonstrated in these patients, suggesting that peripheral arterial vasodilatation could be responsible for this circulatory dysfunction, but the mechanisms by which tense ascites removal induces such changes are unknown

AIM

To investigate the role of a decrease in intra-abdominal pressure (IAP) in the development of early postparacentesis haemodynamic changes

METHODS

Eleven cirrhotic patients with tense ascites received a large volume paracentesis. A specially designed pneumatic girdle was used to compress the abdomen to avoid a decrease in IAP during ascites removal. Haemodynamic studies were performed before paracentesis, one hour after ascites flow stopped, and 30 minutes after pneumatic girdle deflation

RESULTS

When IAP was maintained at its original level, no haemodynamic changes were observed, despite large volume paracentesis. However, a significant decrease in systemic vascular resistance was seen immediately after pneumatic girdle deflation

CONCLUSIONS

Early haemodynamic changes after paracentesis are avoided if IAP is maintained at its original level. The abrupt decrease in IAP could be the trigger for the development of the initial haemodynamic changes that eventually produce postparacentesis circulatory dysfunction.

Blunted natriuretic response to human urine extracts with Na+,K(+)-ATPase inhibiting activity in experimental cirrhosis

Human urine and plasma extracts contain a material that inhibits the enzyme Na+,K(+)-ATPase (the endogenous sodium pump) and produces natriuresis in the bioassay animal. This endogenous sodium pump inhibitor(s), also known as digitalis-like factor, is thought to be involved in sodium and extracellular fluid volume homeostasis. Increased urine and plasma sodium pump inhibiting activity have been reported in patients with cirrhosis and sodium retention. The aim of the study was to assess the renal response to i.v. administration (0.2 ml/min per kg bw for 10 min) of a human urine extract containing sodium pump inhibiting activity (28.5 nmol equivalent ouabain/ml) in eight conscious rats with cirrhosis and ascites and eight control rats. Baseline urinary excretion of Na+,K(+)-ATPase inhibiting activity was significantly higher in cirrhotic rats with ascites than in control rats (235 +/- 40 vs 91 +/- 16; p < 0.01). Human urine extract induced a significant (p < 0.05) increase in glomerular filtration rate in control (3.2 +/- 0.4 to 4.2 +/- 0.5 ml/min) and cirrhotic rats (3.0 +/- 0.3 to 4.0 +/- 0.5 ml/min). In control rats it also increased urinary sodium excretion (1.47 +/- 0.22 to 2.43 +/- 0.5 microEq/min, p < 0.01) and fractional sodium excretion (0.29 +/- 0.01 to 0.43 +/- 0.04%, p < 0.025). In contrast, in cirrhotic rats with ascites neither sodium excretion nor fractional sodium excretion was significantly affected. No changes were observed in plasma aldosterone and atrial natriuretic peptide concentrations in either group. These data suggest that in cirrhosis there is a renal resistance to the natriuretic effect of endogenous sodium pump inhibitor(s).

Acute effects of head-down tilt and hypoxia on modulators of fluid homeostasis

In an effort to understand the interaction between acute postural fluid shifts and hypoxia on hormonal regulation of fluid homeostasis, the authors measured the responses to head-down tilt with and without acute exposure to normobaric hypoxia. Plasma atrial natriuretic peptide (ANP), cyclic guanosine monophosphate (cGMP), cyclic adenosine monophosphate (cAMP), plasma aldosterone (ALD), and plasma renin activity (PRA) were measured in six healthy male volunteers who were exposed to a head-down tilt protocol during normoxia and hypoxia. The tilt protocol consisted of a 17 degrees head-up phase (30 minutes), a 28 degrees head-down phase (1 hour), and a 17 degrees head-up recovery period (2 hours, with the last hour normoxic in both experiments). Altitude equivalent to 14,828 ft was simulated by having the subjects breathe an inspired gas mixture with 13.9% oxygen. The results indicate that the postural fluid redistribution associated with a 60-minute head-down tilt induces the release of ANP and cGMP during both hypoxia and normoxia. Hypoxia increased cGMP, cAMP, ALD, and PRA throughout the protocol and significantly potentiated the increase in cGMP during head-down tilt. Hypoxia had no overall effect on the release of ANP, but appeared to attenuate the increase with head-down tilt. This study describes the acute effects of hypoxia on the endocrine response during fluid redistribution and suggests that the magnitude, but not the direction, of these changes with posture is affected by hypoxia.

Prolonged water immersion. Effects on blood pressure maturation in normotensive rats

The purpose of this experiment was to study the impact of simulated microgravity and of chronic removal of hydrostatic pressure gradients on blood pressure maturation and body growth in rats. A special device was developed in our laboratory to transfer prolonged "dry" water immersion (a technique that has been used for training astronauts under hypogravic conditions) to six Sprague-Dawley test rats (immersion-G group). The time course of heart rate, systolic blood pressure, urinary output, and body weight was monitored from weaning to maturity and then compared with those responses from six sex- and age-matched Sprague-Dawley rats grown in a gravity environment (group G). A downward shift in systolic blood pressure and body weight maturation curves was observed in immersion-G rats from the age of 60 days. Cessation of dry water immersion produced a gradual, significant rise in systolic blood pressure but not in body weight to control values. No marked changes in heart rate and urinary output between G and immersion-G rats were noticed throughout the investigation. Our results provide indirect evidence that an interference in the natural history of blood pressure maturation was introduced by immersion, which dissociated the effects of body weight increase during growth from the effects of ageing per se. It is concluded that the physiological increase in systolic blood pressure during growth is partly gravity-dependent.

Water immersion induced alterations of plasma vasopressin levels and activity of the renin-angiotensin-aldosterone system in noninflammatory acute renal failure and end-stage renal failure

Water immersion (WI) induced alterations of plasma renin activity (PRA), plasma aldosterone (Aldo), vasopressin (AVP), sodium and potassium concentrations and plasma volume (PV) were examined in 12 patients with noninflammatory acute renal failure (NARF) in the anuric/oliguric phase, in 20 patients with chronic renal failure (CRF) and in 15 healthy subjects. In all examined groups a significant increase of PV and decrease of PRA, plasma Aldo, AVP after WI were observed. Significantly more marked decreases of PRA were observed in patients with NARF than in those with CRF and in healthy subjects. In patients with NARF the increase of PV was significantly greater than in CRF and in healthy subjects. In patients with NARF a significantly more marked decrease of plasma sodium concentration was also noted after WI than in subjects with CRF and in normals. Only in healthy subjects was a significant negative correlation noted between the WI increase of PV and decrease of plasma AVP level. In healthy subjects, significantly positive correlations were noted between WI induced decrease of PRA and Aldo and between PRA and plasma AVP, respectively. Such correlations were absent in uraemic patients.

IN CONCLUSION

(1) patients with CRF and NARF show similar, but quantitatively different responses of PRA, Aldo and AVP secretion to WI as compared with normals; (2) patients with NARF and CRF are characterized by an inappropriate volumetric and osmotic regulation of AVP secretion; (3) in uraemic patients the physiological relationship between the renin-angiotensin system and AVP secretion seems to be dissociated.

Predicting new effective treatments of alcohol addiction on the basis of their properties of inhibition of noradrenergic activity and/or thromboxane or on the activation of the dopamine reward system and/or beta-endorphin

On the basis of their properties of noradrenergic and/or thromboxane inhibition, or on their activation of the dopaminergic reward system and/or beta-endorphin, the following substances or treatments are predicted to be effective in treating alcohol or drug addiction: ginger; carbon dioxide; dietary sulfur; methionine; calcium; LHRH; high intensity light; interferon; negative ions; serotonin antagonists such as methysergide and cyproheptadine; guanabenz and guenfacine; antihistamines; head-out water immersion; X-irradiation; and forced unilateral left nostril breathing.

Vasopressin inhibition via combined head-out water immersion and a prostaglandin E-1 precursor in the treatment of male reproductive failure due to chronic alcohol abuse

Male reproductive failure and infertility are quite common in alcoholics. There are very high correlations between elevated vasopressin levels and male infertility on the one hand, and probable deficiencies of prostaglandin E1 which may raise levels of PGE2 and endorphins which, in turn, release vasopressin on the other. Since head-out water immersion rapidly decreases vasopressin levels, a suggested joint protocol of head-out water immersion and a prostaglandin E-1 precursor is proposed for male reproductive failure in alcoholics.

Atrial natriuretic peptide is only a minor diuretic factor in dehydrated subjects immersed to the neck in water

To determine if the atrial natriuretic peptide (ANP) is an important factor for inducing diuresis during head-out water immersion even in dehydrated subjects, six healthy volunteers were immersed up to the neck in water at 34.5 degrees C for three hrs. Significant diuresis and natriuresis occurred, but urine osmolality decreased and negative CH2O was restored in a positive direction toward zero, even though subjects were still in a state of considerable dehydration. Plasma renin activity and plasma angiotensin I and II concentrations decreased but that of plasma aldosterone remained unchanged during water immersion, and plasma ANP did not increase throughout the examination. On the basis of the data of the present study, the factor inducing diuresis during head-out water immersion in hydrated subjects appears to differ from that in dehydrated subjects, and the main factor inducing diuresis during water immersion in dehydrated subjects may be the suppression of vasopressin release and not ANP.

Effect of head-out water immersion on cardiorespiratory response to dynamic exercise

Head-out water immersion is known to produce several cardiopulmonary adjustments at rest due to a cephalad shift in blood volume. The purpose of this study was to determine the effect of head-out water immersion on the cardiorespiratory response to graded dynamic exercise. Nineteen healthy middle-aged men performed upright cycling exercise at 40, 60 and 80% of maximal oxygen consumption on land and in water (31.0 +/- 1.0 degrees C) to the shoulders. Cardiac output (measured by the carbon dioxide rebreathing technique) was significantly greater in water at 40 and 80% maximal oxygen consumption. Stroke volume was significantly elevated at all stages of exercise. Heart rate did not differ significantly at 40 and 60% maximal oxygen consumption but was significantly lower in water at 80% maximal oxygen consumption. Total ventilation did not differ significantly in water and on land at any stage of exercise. The results suggest that the central redistribution of blood volume with head-out water immersion leads to an increase in stroke volume. Because there is not a proportional decrease in heart rate with the elevated stroke volume, cardiac output is regulated at a higher level during upright exercise in water compared with that on land. In conclusion, there are serious limitations of available, prerecorded rhythm data bases for designing and testing of automatic external defibrillators. Performance can be adequately assessed only by extensive clinical tests, which seem mandatory for this new and important type of defibrillator.

Studies on the optimal temperature of flotation tanks in the management of skeletal injuries in the horse

In order to determine optimum tank temperature, nine horses were allocated randomly to three groups and placed in a flotation tank at temperatures of 28 degrees C, 32 degrees C and 36 degrees C. Their progress was monitored by subjective and objective clinical measurements and a variety of laboratory parameters. A 'reacclimatisation crisis' following removal from the tank was observed in most horses after immersion for 21 days and it was concluded that a tank temperature of 36 degrees C provided maximum patient comfort and minimum homoeostatic disturbance.

Pulmonary changes associated with flotation techniques in the treatment of skeletal injuries in the horse

Six adult horses with normal blood gas values, normal thoracic radiographs and free from overt signs of respiratory disease were confined in flotation tanks for periods from one to seven weeks. With one exception, they all coughed, had a variable amount of nasal discharge and, at autopsy, showed cranio-ventral alterations to their lungs which were characterised by patchy irregular areas of absorption atelectasis with or without an inflammatory reaction and an accompanying alveolar emphysema.

Immersion anesthesia for extracorporeal shock wave lithotripsy. Review of two hundred twenty treatments

Two hundred twenty extracorporeal shockwave lithotripsy (ESWL) treatments at the New York Hospital-Cornell Medical Center between September, 1984, and April, 1985, were reviewed with respect to anesthetic management. One hundred seventy-four treatments (79%) were performed under a regional anesthetic technique (RA), either with an indwelling epidural catheter (155 treatments), or with a single spinal injection (19 treatments). Forty-six treatments (21%) were performed under general anesthesia (GA). Ninety per cent of the patients were classified as ASA I or II. Hypotension during treatment, defined as blood pressure falls greater than 20 per cent of baseline mean arterial pressure, was recorded with 19.5 per cent of the regional anesthetic treatments (18.7% of the epidurals and 26.3% of the spinals) and 13.0 per cent of the general anesthetic treatments. Blood pressure falls were larger in the regional group than in the general group. The average recovery room stay was longer for the bupivacaine (0.25-0.5%) epidurals and the tetracaine (0.4%) spinals (252 min and 212.1 min, respectively) than for the lidocaine (1.5-2.0%) epidurals and the general anesthetics (101.7 min and 102.1 min, respectively). General anesthesia, with controlled ventilation, was advantageous in minimizing renal excursion and stone movement during treatment. Yet, in appropriately selected and sedated patients, regional anesthesia with continuous lidocaine epidural techniques was found to provide acceptable anesthesia for patients undergoing ESWL.

Rubidium and sodium transport across erythrocyte membrane: alterations due to a circulating factor

Essential hypertension patients can be divided into two groups on the basis of the presence or absence of a plasma factor able to inhibit rubidium uptake and sodium extrusion by the red blood cells. Nearly fifty percent of the patients studied present this factor. Preliminary results show that it is dialyzable, has a molecular weight around 500 daltons and cannot be extracted by chloroform.

Hemodynamic effects of massive peripheral edema

The possibility that noncardiac massive peripheral edema reduces venous distensibility was investigated in eight patients in the supine and 80-degree head-up tilt position before and after diuretic therapy. After clearance of the edema with diuretic therapy, total blood volume (TBV) was not significantly decreased; therefore, in the supine position the significant (2p less than 0.001) decrease of right atrial pressure, stroke volume, cardiac output, and cardiopulmonary blood volume (CBV) by the diuretics was due to an improvement in venous compliance which resulted in peripheral redistribution of CBV since the ratio CBV/TBV was decreased during diuretic therapy (2p less than 0.001). Furthermore, before diuretic therapy, tilt significantly decreased right atrial pressure, stroke volume, cardiac output, CBV, and the ratio CBV/TBV; but after diuretic therapy, the decrease of the same variables during tilt was significantly (2p less than 0.001) greater. These results indicate that marked peripheral edema considerably decreases venous compliance which can be improved with diuretic therapy.

Evidence that some mechanism other than the renin system causes sodium retention in nephrotic syndrome

8 of 16 patients with nephrotic syndrome had normal or low plasma renin activity while spontaneously retaining sodium. The other 8 patients had a high plasma renin activity which may have caused the sodium retention. Oral captopril and albumin infusion given separately both suppressed the renin system in these patients. Despite this, urinary sodium excretion remained less than sodium intake and patients continued to retain sodium and gain weight. These results suggest that, even in patients with nephrotic syndrome who do have stimulation of the renin angiotensin system, some other overriding mechanism is responsible for sodium retention. Therefore it seems unlikely that angiotensin-converting enzyme inhibitors will be useful in the treatment of sodium retention in nephrotic syndrome.

Body fluid homeostasis in congestive heart failure and cirrhosis with ascites

The urinary excretion of salt and water in man is regulated by a variety of renal and extrarenal mechanisms that respond to changes in dietary sodium intake as well as to alterations in the holding capacity of the vascular and interstitial compartments. Changes in extracellular fluid volume are detected by volume sensors located in the intrathoracic vascular bed, the kidney and other organs. These sensing mechanisms gauge the adequacy of intravascular volume relative to capacitance at various sites within the circulation. Congestive heart failure and cirrhosis with ascites are two disease states of man in which a hemodynamic disturbance within a given circulatory subcompartment is perceived by these sensing mechanisms and results in renal sodium retention. While the primary disturbance in both of these conditions originates outside the kidney, a variety of renal effector mechanisms respond to the perceived circulatory disturbance and result in enhanced tubule reabsorption of salt and water. These effector mechanisms involve physical adjustments in renal microvascular hemodynamics, tubule fluid composition and flow rate and transtubular ion gradients. These in turn are partially regulated by a variety of neural and humoral pathways including the renin-angiotensin-aldosterone axis, prostaglandins, and kinins.

Renin release after furosemide and ethacrynic acid in man. Evidence for neural reflex control mechanisms

The mechanisms of renin release after furosemide (F) and ethacrynic acid (EA) in man were examined. We evaluated whether acute volume shifts within the low pressure system after F induce renin release via neural pathways. Immersion in a water-bath or beta-blockade reduced the increase of plasma renin concentration after F but not after EA. It is concluded that acute renin release after F but not after EA in man is partially due to neurally mediated reflexes originating from volume receptors in the cardiopulmonary area.