Crosstalk of Pain and Thirst Perception: A Brief Review

Post-Exercise Voluntary Drinking Cessation Is Associated with the Normalization of Plasma Osmolality and Thirst Perception, but Not of Urine Indicators or Net Fluid Balance

Post-exercise rehydration has been widely studied, with particular emphasis on retention of ingested fluid; comparatively little research has been conducted on why we drink more or less. To identify physiological values corresponding to voluntary drinking cessation (VDC), nine males exercised intermittently at 70−80% HRmax in the heat (WBGT = 28.1 ± 0.7 °C) to achieve a dehydration of approximately 4.0% body mass (BM). After exercise, participants were instructed to drink water as long and as much as they needed. Urine color (Ucolor), specific gravity (USG), osmolality (Uosm), plasma osmolality (Posm), fullness, BM, and thirst perception (TP) were measured pre- and post-exercise and at VDC. Each variable was compared for the three points in time with a one-way ANOVA. Participants reached dehydration of −3.6 ± 0.3% BM. Pre-exercise USG (1.022 ± 0.004) was lower than at VDC (1.029 ± 0.004, p = 0.022), Uosm did not change over time (p = 0.217), and Ucolor was lower pre-exercise (3.4 ± 0.7) vs. post-exercise (5.5 ± 1.23, p = 0.0008) and vs. VDC (6.3 ± 1.1, p < 0.0001). Posm showed a difference between pre-exercise (289.5 ± 2.3) and post-exercise (297.8 ± 3.9, p = 0.0006) and between post-exercise and VDC (287.3 ± 5.4, p < 0.0001). TP post-exercise (96.4 ± 4.34) was significantly higher than pre-exercise (36.2 ± 19.1) and VDC (25.0 ± 18.2, p < 0.0001). At VDC, participants had recovered 58.7 ± 12.1% of BM loss. At the point of voluntary drinking cessation, Posm and thirst perception had returned to their pre-exercise values, while rehydration relative to initial BM was still incomplete.

Comparing thirst and spot urine concentrations in humans of differing body sizes: An observational study

Elevated body mass index (BMI) has been associated with elevated urine osmolality (UOsm), despite having higher total water intake, but it is unclear if overweight/obese individuals have reduced thirst. In this observational study, we found that overweight/obese individuals had higher UOsm compared to normal-weight individuals (749 ± 37 vs. 624 ± 35 mmol•kg^-1; P < 0.01) while possessing similar thirst ratings (56.4 ± 3 vs. 51.6 ± 3 mm; P = 0.3). In this observational study, overweight/obese individuals possessed more concentrated urine in the absence of higher thirst perception.

Thirst in patients admitted to intensive care units: an observational study

Background

Despite various studies reporting a high prevalence, reaching 71%, the sensation of thirst in intensive care unit (ICU) patients, its prevention, detection, and management, is not well known nor considered. Limited research has examined the causes of thirst in ICU patients, while it has been examined in other patient populations.

Aim

To determine the incidence and intensity of thirst in patients admitted to ICU and its association with airway devices (endotracheal tube, tracheostomy, oxygen mask), airway humidification, patients’ characteristics, and therapy (serum sodium concentration, hematocrit, fluid balance, possibility of oral hydration, and dosage of diuretics).

Methods

Patients were interviewed daily to report the presence of thirst and rate its intensity on a Numeric Rating Scale (NRS) from 0 (no thirst) –10 (intolerable thirst). Other data were obtained through direct evaluation or by consulting medical records. Patients admitted to three ICUs from May to August 2014 in a university hospital in Italy were included.

Results

A total of 220 Patients were enrolled. Thirst was found in 76.1% of patients’ observations, with a mean thirst score of 5.37. Thirst intensity was predicted by high doses of diuretics (> 100 mg/die), increasing serum sodium concentration, absence of oral hydration and the presence of xerostomia. Thirst was associated with the use of humidified Venturi mask.

Conclusions

Thirst is highly prevalent among patients in this population of intensive care patients. It would be desirable to evaluate this stressor at least daily, to eliminate or relieve this sensation.