Plasma renin activity and serum aldosterone during prolonged physical strain. The significance of sleep and energy deprivation

Exercise-Induced Fluid Retention, Cardiac Volume Overload, and Peripheral Edema in Ultra-Distance Cyclists

Introduction

Ultracyclists expose themselves to extreme physical challenges. This study aimed to elucidate the effects of ultracycling on electrolyte and fluid balance and investigate the potential occurrence of peripheral edema.

Methods

A total of 4 clinical visits were performed before, during, and after a 6-day bicycle ride in 13 ultracyclists (5 female, 8 male) including serial laboratory analyses of blood and urine, bioelectrical impedance, and echocardiography. Throughout the ride, participants continuously tracked fluid intake, measured extremity circumferences daily, and self-tested urinary electrolytes using a point-of-care testing device. Portrait photos were judged by 20 physicians for occurrence of facial and eyelid edema.

Results

Participants covered a mean distance of 1205 km and 19,417 vertical meters. From baseline to day 6, body weight remained stable (P = 0.479); however, body composition changed with increasing total body water (TBW) (+1.98 l ± 1.37, P = 0.003) and plasma volume (+18.86 % ± 10.7, P < 0.001). A significant increase in N-terminal pro brain natriuretic peptide (NT-proBNP) (+297.99 ng/l ± 190.42, P < 0.001) until day 6 indicates concomitant cardiac volume overload. Swelling of face and eyelids peaked on day 5 (both P ≤ 0.033). On recovery, changes partly resolved. Although urinary sodium concentration showed a nadir on day 4 (-32.18 mmol/l ± 23.88, P = 0.022), plasma osmolality (+5.69 mmosmol/kg ± 5.88, P = 0.004) and copeptin (+38.28 pg/ml ± 18.90, P < 0.001) increased steadily until day 6.

Conclusion

Ultracycling over multiple days induces extracellular volume expansion, peripheral edema, and cardiac volume overload. Renal sodium and water retention is likely contributing to this condition.

Early ICU-acquired hypernatraemia is associated with injury severity and preceded by reduced renal sodium and chloride excretion in polytrauma patients

PURPOSE

To further elucidate the origin of early ICU-acquired hypernatraemia.

MATERIAL AND METHODS

In this retrospective single-centre study, polytrauma patients requiring ICU treatment were analysed.

RESULTS

Forty-eight (47.5%) of 101 included polytrauma patients developed hypernatraemia within the first 7 days on ICU. They were more severely ill as described by higher SAPS III, ISS, daily SOFA scores and initial norepinephrine requirements as well as longer requirements of mechanical ventilation and ICU treatment in general. The development of hypernatraemia was neither attributable to fluid- or sodium-balances nor renal impairment. Although lower in the hypernatraemic group from day 4 onwards, median creatinine clearances were sufficiently high throughout the observation period. However, in the hypernatraemic group, urine sodium and chloride concentrations prior to the evolvement of hypernatraemia (56 (27-87) mmol/l and 39 (23-77) mmol/l) were significantly decreased when compared to i) the time after developing hypernatraemia (94 (58-134) mmol/l and 78 (36-115) mmol/l; p < 0.001) and ii) the non-hypernatraemic group in general (101 (66-143) mmol/l and 75 (47-109) mmol/l; p < 0.001).

CONCLUSIONS

Early ICU-acquired hypernatraemia is associated with injury severity and preceded by reduced renal sodium and chloride excretion in polytrauma patients.

Moving in extreme environments: extreme loading; carriage versus distance

This review addresses human capacity for movement in the context of extreme loading and with it the combined effects of metabolic, biomechanical and gravitational stress on the human body. This topic encompasses extreme duration, as occurs in ultra-endurance competitions (e.g. adventure racing and transcontinental races) and expeditions (e.g. polar crossings), to the more gravitationally limited load carriage (e.g. in the military context). Juxtaposed to these circumstances is the extreme metabolic and mechanical unloading associated with space travel, prolonged bedrest and sedentary lifestyle, which may be at least as problematic, and are therefore included as a reference, e.g. when considering exposure, dangers and (mal)adaptations. As per the other reviews in this series, we describe the nature of the stress and the associated consequences; illustrate relevant regulations, including why and how they are set; present the pros and cons for self versus prescribed acute and chronic exposure; describe humans' (mal)adaptations; and finally suggest future directions for practice and research. In summary, we describe adaptation patterns that are often U or J shaped and that over time minimal or no load carriage decreases the global load carrying capacity and eventually leads to severe adverse effects and manifest disease under minimal absolute but high relative loads. We advocate that further understanding of load carrying capacity and the inherent mechanisms leading to adverse effects may advantageously be studied in this perspective. With improved access to insightful and portable technologies, there are some exciting possibilities to explore these questions in this context.

One night on-call: sleep deprivation affects cardiac autonomic control and inflammation in physicians

BACKGROUND

Sleep loss is associated with increased cardiovascular morbidity and mortality. It is known that chronic sleep restriction affects autonomic cardiovascular control and inflammatory response. However, scanty data are available on the effects of acute sleep deprivation (ASD) due to night shifts on the cardiovascular system and its capability to respond to stressor stimuli. The aim of our study was to investigate whether a real life model of ASD, such as "one night on-call", might alter the autonomic dynamic response to orthostatic challenge and modify the immune response in young physicians.

METHODS

Fifteen healthy residents in Internal Medicine were studied before and after one night on-call at Rest and during a gravitational stimulus (head up-tilt test, HUT). Heart rate variability (HRV), blood pressure variability (BPV) and baroreflex sensitivity (BRS) were analyzed during Rest and HUT before and after ASD. Plasmatic hormones (epinephrine, norepinephrine, cortisol, renin, aldosterone, ACTH) and tissue inflammatory cytokines were measured at baseline and after ASD.

RESULT

HRV analysis revealed a predominant sympathetic modulation and a parasympathetic withdrawal after ASD. During HUT, the sympathovagal balance shifted towards a sympathetic predominance before and after ASD. However, the magnitude of the autonomic response was lower after ASD. BPV and BRS remained unchanged before and after ASD as the hormone levels, while IFN-γ increased after ASD compared to baseline.

CONCLUSION

In summary, one night of sleep deprivation, at least in this real-life model, seems to affect cardiovascular autonomic response and immune modulation, independently by the activation of the hypothalamic-pituitary axis.

Fluid balance and renal response following dehydrating exercise in well-trained men and women

We examined the recovery of plasma volume, plasma osmolality, renal water and sodium handling and fluid-regulating hormones to dehydrating exercise in well-trained women and compared them to men. Ten male and eight female athletes cycled at anaerobic threshold at an ambient temperature of 32 degrees C until dehydration by 3% of their body mass (mb). After exercise, they drank water equal to 1% mb and rested for 240 min. Plasma renin activity (PRA), serum aldosterone [ALDO]s, plasma arginine vasopressin [AVP]pl, norepinephrine concentrations and plasma osmolality (Osmpl) were determined at baseline, end of exercise, 30, 60, 120 and 240 min postexercise. Urine was collected at baseline, end of exercise, 60, 120 and 240 min postexercise. Renal free water and sodium handling were assessed. The recovery of OSMpl and plasma volume occurred within the first 60 min of recovery and at similar rates between the groups. However, women had lower PRA at the end of exercise (P = 0.05), an earlier recovery of [ALDO]s, and a slower [AVP]pl recovery. Overall fluid balance was similar between the men and women, as were the early recovery of renal free water clearance (CH2O). During the last 120 min of recovery CH2O was more negative (greater water reabsorption) and fractional sodium excretion was increased in the women compared to the men. Despite small differences in sodium and water reabsorption following dehydration, it appears from other study that recovery from dehydrating exercise in well-trained men and women is remarkably similar.

Atrial natriuretic peptide in plasma after prolonged physical strain, energy deficiency and sleep deprivation

Plasma concentrations of atrial natriuretic peptide (ANP) were investigated daily in 16 male cadets during a 6-day military training course with continuous heavy physical activities, sleep and energy deficiency (course I). At the end of another similar course (course II) 15 cadets were studied during 30-min cycle exercise at 50% maximal oxygen uptake with and without glucose infusion. A small, but not significant increase was found in the plasma concentrations of ANP during course I from 9.6 (SEM 1.1) pmol.l-1 in the control experiment to 11.1 (SEM 0.5) pmol.l-1 on day 5. During course II a small but significant increase was found from 7.8 (SEM 0.5) pmol.l-1 in the control experiment to 9.1 (SEM 0.5) pmol.l-1 at the end of the course. Plasma osmolality and chloride concentration decreased during the course. During the exercise test a significant increase was seen in ANP concentration from 8.2 (SEM 0.8) to 13.1 (SEM 2.0) pmol.l-1 in the control experiment and from 9.4 (SEM 0.7) to 13.5 (SEM 1.2) pmol.l-1 during the course. This response was attenuated by glucose infusion, an effect which may have been due to an exercise induced increase in plasma chloride concentration being abolished. In contrast, the potassium concentration response to exercise was increased during the course but unaffected by glucose infusion. In conclusion, the large increases in endogenous plasma catecholamine concentration shown to take place during previous courses were not reflected in the plasma concentrations of ANP, indicating only a moderate cardiac stress or no cardiac work overload during such courses.

Enzymatic and hormonal responses following a 24 h endurance run and a 10 h triathlon race

Muscle cell leakage and hormonal changes were compared immediately after and during the 3 days following a 24 h endurance run (R24h) in 8 subjects, and a 10 h triathlon non-competitive race (T10h) in 6 subjects. The study showed three main differences: 1) plasma enzyme increases were considerably more significant in R24h than in T10h: compared with resting levels, creatine kinase increased x 120 after R24h but only x 2 after T10h; lactic dehydrogenase x 4, as opposed to x 1.5; and transaminases only showed an increase after R24h. The plasma myoglobin increase after R24h was double that found after T10h; 2) for the same magnitude of plasma aldosterone and cortisol after R24h and T10h (3 times the resting levels), a highly significant decrease in urinary Na+ (p less than 0.001) and an increase in urinary K+ (p less than 0.01) were found only after R24h; and 3) the plasma free noradrenaline level increased significantly after R24h (x 2.6) whereas it was unchanged after T10h. In contrast, the plasma level of conjugated dopamine increased only after T10h (x 3.7, p less than 0.05). These results suggest that long-distance running causes more muscular lesions than the triathlon, and that important factors other than aldosterone are probably involved in the regulation of urinary electrolyte excretions during T10h.

A retrospective and explorative study of hypokalemia in psychiatric disorders: a beta 2-receptor related phenomenon

Since the serum potassium level is under beta 2-adrenergic influence, we studied serum potassium values on admission in psychiatric patients. Data are reported on 683 patients from nine major diagnostic groups. Among these nine groups significant differences were found concerning the mean serum potassium level and incidence of hypokalemia. Significant differences existed between the alcohol withdrawal and attempted suicide groups compared to the dysthymic, bipolar manic, schizophrenic and nonschizophrenic psychosis groups. Like alcohol withdrawal, attempted suicide is assumed to be a hyper-adrenergic state. Although the relative contribution of factors like nutritional state, aldosterone, insulin, and beta 2-receptor density or sensitivity is unclear, the catecholamine-potassium relationship deserves further study.