The effect of water temperature on orthostatic tolerance: a randomised crossover trial, 2022, Lain T Parsons et al

Abstract

Purpose

Bolus water drinking, at room temperature, has been shown to improve orthostatic tolerance (OT), probably via sympathetic activation; however, it is not clear whether the temperature of the water bolus modifies the effect on OT or the cardiovascular responses to orthostatic stress. The aim of this study was to assess whether differing water temperature of the water bolus would alter time to presyncope and/or cardiovascular parameters during incremental orthostatic stress.

Methods
Fourteen participants underwent three head-up tilt (HUT) tests with graded lower body negative pressure (LBNP) continued until presyncope. Fifteen minutes prior to each HUT, participants drank a 500 mL bolus of water which was randomised, in single-blind crossover fashion, to either room temperature water (20 °C) (ROOM), ice-cold water (0–3 °C) (COLD) or warm water (45 °C) (WARM). Cardiovascular parameters were monitored continuously.

Results
There was no significant difference in OT in the COLD (33 ± 3 min; p = 0.3321) and WARM (32 ± 3 min; p = 0.6764) conditions in comparison to the ROOM condition (31 ± 3 min). During the HUT tests, heart rate and cardiac output were significantly reduced (p < 0.0073), with significantly increased systolic blood pressure, stroke volume, cerebral blood flow velocity and total peripheral resistance (p < 0.0054), in the COLD compared to ROOM conditions.

Conclusions
In healthy controls, bolus cold water drinking results in favourable orthostatic cardiovascular responses during HUT/LBNP without significantly altering OT. Using a cold water bolus may result in additional benefits in patients with orthostatic intolerance above those conferred by bolus water at room temperature (by ameliorating orthostatic tachycardia and enhancing vascular resistance responses). Further research in patients with orthostatic intolerance is warranted.

https://link.springer.com/article/10.1007/s10286-022-00860-7

 

Wow, they skipped the whole feasibility phase? How did they know it was feasible to do such a trial without checking whether it's feasible to do it? And acceptable to patients?

I'm still very confused about the purpose of those, and how common and mindlessly repetitive they are. Other than how they fit together in the process loop where the conclusion of biopsychosocial research is always to conclude that more psychosocial research is needed.

This is a very odd study, though. Oh, look at that, it concludes that more research is needed.

 

Funny thing is that I found drinking warm milk (hot cacao, pink of salt) to be very hydrating and helped with orthostatic stress.

I don't urinate for hours, unlike water that keeps me up all night.

 

The effect of cool water immersion is clear enough for me that I don't need instruments. I'm however not certain that what changes is the ANS.

Within seconds, something in the body calms down, breathing and heart seem to go slower, deeper, stronger and it just feels right.

 

My OT became bad during very hot weather. I thought it had become permanent but it got better during the winter. The next summer I took steps to stay as cool as possible and it has never been completely disabling since.

 

Heat intolerance is definitely a thing, also common in LC. It'd be great if it could be studied seriously. Drinking cold water is probably irrelevant in itself, and rather is about the same issue, just inside rather than outside. There have been some attempts with cold immersion therapy as well, they don't seem to have any effect on the cause, so keeping at a pragmatic level will never tell us anything.

It even should hint at something, a possibility is that the issues with blood vessels and what affects them to cause dysautonomia affects heat dissipation. There's probably some very useful information in there, if there could just be a coherent research effort.

Or decades into knowing about this condition, we could just stick to small studies like this that ultimately don't advance anything.

 

I haven’t read the article itself, but the abstract leaves open if the effects observed relate to the consumption of fluid plus temperature conditions or to the temperature impact alone regardless of presence the fluid vector.

[edited to clarify]

 

Water boluses, which involve drinking glasses of water in rapid succession, can help to expand blood volume. The specific amount reported in the medical literature varies, but is approximately two 8 ounce glasses of water.

 

I hadn't considered it but my temperature control is very bad. Right from when I was first ill if I am too hot I have great difficulty cooling down and if I am cold I need an outside source to heat up.

In the days when I could still get out shopping my FiL would pick us up from the town centre but if he was delayed I would get very cold. Strangely, when I got home and wrapped up in heated throws and wheat bags I would carry on getting colder for hours (literally) until I would suddenly become too hot. Never understood it.

I know I have a problem with the part of the brain that keeps everything in homeostasis but I never connected it to OT.

 

Can somebody please start a poll about this here on the forum? And/or on Twitter? I'd love to learn more about people's experiences. Even if it's not "bolus drinking" per se, but just drinking some amount of extra water? (I'm too crashed to start a poll myself.)

 

As far as I can see all the evidence quoted relates to shifts in cardiovascular measures 15 minutes after drinking a bolus in an artificial situation with negative lower body pressure as well as tilt.

I don't think it is meaningful to say that it 'improves orthostatic intolerance' as if it was actually useful to patients.

Presumably 15 minutes is the single time point when there is actually some slight blood volume expansion. At 5 minutes it has not happened yet and by 25 minutes most of the water is in the bladder or peed out.

To be of any interest they should have measured orthostatic tolerance three hours after drinking.

 

I think it might be too unspecific, tbh. It must be common in the very young, the very old, and folk who're unwell with all sorts of conditions. Oh, and carrot-topped pink people like me.

 

I can report, coincidentally, having switched from drinking room temperature water to cold water over the last few weeks.

Zero noticeable change. Other than it's very soothing for the throat, which is nice. My throat is constantly clogged up so it can get irritated and stuffy. It's nice for that and nothing else.