The Effects Of A Novel "Fluid Loading" Strategy On The Cardiovascular And Haematological Responses To Orthostatic Stress

Abstract

Patients restricted to bed rest and astronauts exposed to microgravity experience large reductions in body mass (BM), total body water (TBW), plasma volume (PV) and skeletal muscle mass which can lead to orthostatic intolerance, and as yet there are no effective countermeasures. However, a novel fluid loading strategy combining creatine (Cr) and glycerol (Gly) results in a significant increase in BM, TBW and PV, which may attenuate some of the detrimental physiological effects of immobilisation.. PURPOSE: To examine the cardiovascular and haematological responses to orthostatic stress following supplementation with Cr and Gly. METHODS: 10 male subjects were subjected to 3 postural tilt tests designed to induce orthostatic stress, during which they lay supine for 30 min followed by a further 30 min in the 70 o head up position. Following 2 baseline experimental trials, subjects ingested 20g Cr and 1 g Gly•kg-1 BM per day for 7 days, flavoured with 200 ml diluting juice made up in 1 L of warm water. RESULTS: Tilting subjects from the supine position to 70 o resulted in a significant mean increase in heart rate of 16 beats•min-1 indicating a significant orthostatic challenge with no difference between experimental trials. During both baseline trials 3 subjects experienced hypotension and syncope during the 70 o head up tilt phase. Following supplementation, BM increased (mean ± S.D.) by 0.9 ± 0.3 kg, TBW by 0.7 ± 0.2 L and PV by 3.2 ± 2.4%. Cr and Gly supplementation resulted in a significant mean increase in systolic (11 mmHg; P=0.02) and diastolic (7 mmHg; P=0.04) blood pressure during the tilt test and a reduced incidence of orthostatic hypotension and presyncope (1 subject). CONCLUSION: These data suggest that the expansion of body water compartments through Cr/Gly supplementation coupled with the purported anabolic properties of Cr may prove an effective countermeasure to combat orthostatic intolerance in patients exposed to prolonged periods of bed rest and astronauts following spaceflight.

The effects of creatine supplementation on thermoregulation and physical (cognitive) performance: a review and future prospects

“…The Cr/Gly hyperhydrating protocol developed by Easton et al (2007) has been successfully applied to counter orthostatic intolerance in male subjects undertaking a postural tilt test whereby subjects lay supine for 30 minutes before being tilted head-up to 70º for a further 30 minutes or until the limit of tolerance (Easton et al 2009). While cardiovascular parameters were monitored, indices of cognitive performance were not measured.…”

“…No effects on core temperature compared to placebo Reduced plasma volume loss during 1 hour of hyperthermic submaximal exercise Cognitive performance and neuroprotection Jones et al 2009Tan, 2014Haussinger et al 1993 Francaux and Poortmans 1999; Saab et al 2002Kilduff et al 2003Kilduff et al 2004;Easton et al 2007;Beis et al 2011;Polyviou et al 2012Tarnopolsky et al 1997Andrews et al 1998;Hespel et al 2001Fuld et al 2005Easton et al 2009Bennett et al 2001Branch et al 2007 Increase in psychomotor, complex cognitive task and motor skill performance post-sleep deprivation Some evidence of neuroprotection Reduced hypoxic brain damage McMorris et al 2006;McMorris et al 2007;Cook et al 2011Turner et al 2015Carter et al 1995 Footnote: All studies presented in Table 1 are human studies with the exception of Carter et al 1995 and who used in vitro animal models…”

Hydration and Health

“…Osmolytes that have been shown to enhance fluid retention include creatine, betaine, glycerol, sodium, and even carbohydrate, each of which has been shown to increase the TBW or plasma volume through transient reduction in urine output. [121][122][123][124][125][126][127][128] Improvement in physical performance associated with ingesting these osmolytes and an increase in fluid content have been shown. With the exception of improved orthostatic intolerance, 127 other health benefits have yet to be demonstrated for elevating and maintaining TBW.…”