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Oral rehydration solutions for treating exertion-related dehydration: FA 584 Systematic Review

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Conflict of Interest Declaration

The ILCOR Continuous Evidence Evaluation process is guided by a rigorous ILCOR Conflict of Interest policy. The following Task Force members and other authors were recused from the discussion as they declared a conflict of interest: none applicable.

The following Task Force members and other authors declared an intellectual conflict of interest and this was acknowledged and managed by the Task Force Chairs and Conflict of Interest committees: none applicable.

CoSTR Citation

Borra V, De Brier N, Berry D, Zideman D, Singletary EM – on behalf of the International Liaison Committee on Resuscitation First Aid Task Force. Oral rehydration drinks for treating exertion-related dehydration Consensus on Science and Treatment Recommendations [Internet] Belgium, 2021 February 15. Available from: http://ilcor.org

Collaborators: Wei-Tien Chang, Nathan P Charlton, Therese Djarv, Jestin N Carlson, Pascal Cassan, Jason Bendall, Daniel Meyran, Tetsuya Sakamoto, Aaron Orkin, Matthew Douma, Richard Bradley, Michael Nemeth, Jonathan L Epstein, Craig Goolsby, Jeff Woodin, David Markenson, Janel M Swain.

Methodological Preamble and Link to Published Systematic Review

The continuous evidence evaluation process for the production of Consensus on Science with Treatment Recommendations (CoSTR) started with a systematic review of exertion-related dehydration and rehydration ({Borra 2021} – PROSPERO CRD42020153077) conducted by Vere Borra and Niels De Brier with involvement of clinical content experts. This topic was last reviewed by the First Aid Task Force in 2015.{Singletary 2015; Zideman 2015} Evidence for adult literature was sought and considered by the Basic Life Support Adult Task Force and the Pediatric Task Force groups respectively. These data were taken into account when formulating the Treatment Recommendations.

All studies were completed by healthy volunteers who underwent various exercises for a predetermined duration and had outcome measurements before, during and after fluid ingestion. Due to the large heterogeneity between studies (i.e. different protocols for dehydration, large variability in time to rehydrate and timepoints measured), and missing data from the cross-over design, meta-analyses were not possible.

Because different rehydration periods were used, it was decided a priori to only include timepoints after completion of drinking. Since this review focuses on the out-of-hospital setting following exertion-related dehydration, we limited relevant timepoints to 1 h and 2 h after completion of drinking; any later timepoint was excluded (except for cumulative urine volume, where the endpoint of the study was included). If 1 h and or 2 h after completion were not reported, any other timepoint within 2 h after completion of drinking was included. For patient satisfaction outcomes, we included timepoints starting from immediately after completion of drinking until 2 h after completion of drinking.

Determination of desirable and undesirable directions for outcome measurements:

  • Urine output was typically calculated by weighing urine or recording volume using a graduated cylinder. Cumulative urine output was calculated as the sum of the urine volumes measured during the recovery period. When consuming a fixed volume of a drink, a reduced urine output indicates a better retention of the consumed drink and, hence, beneficial by enhancing the rehydration process (Maughan 2016, 717).
  • Net fluid balance is calculated as the sum of the volume of sweat loss during the exercise and urine losses during the exercise and recovery periods, subtracted from the volume of drink consumed (Casa 2000, 212). Restoration of the net fluid balance is beneficial and larger values indicate that the sweat losses have been replaced effectively.
  • Change in plasma volume was calculated as described by Dill and Costill (Dill 1974, 247). Exertion-related dehydration will decrease plasma volume in proportion to the level of fluid loss due to sweating and positive changes in plasma volume are beneficial during rehydration. Fluid replacement should be targeted at plasma volume restoration to ensure that circulation and sweating can progress at optimal levels.
  • Hemoglobin and hematocrit values are based on whole blood and are therefore dependent on plasma volume. If a person is severely dehydrated, the hemoglobin and hematocrit values will appear higher and restoring these measures to their baseline values suggests effective rehydration.
  • The combination of exercising, heat stress, and dehydration contributes to high levels of cardiovascular strain (high heart rate) and lower heart rates are beneficial during the recovery period (Hostler 2010, 194).
  • Serum and plasma osmolality were measured with freezing point depression method and serum electrolyte concentration were typically analyzed with flame photometry or ion selective electrodes. During rehydration, the restoration and maintenance of a high plasma or serum osmolality and serum electrolyte concentrations is desirable and avoids the stimulation of diuresis (Nose 1988, 325).
  • Patient satisfaction outcomes (thirst, gastric fullness, bloating, nausea) were measured with a Visual Analogue Scale (VAS). Lower scores are beneficial when assessing patient satisfaction after drinking.

Systematic Review

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PICOST

The PICOST (Population, Intervention, Comparator, Outcome, Study Designs and Timeframe)

Population: Adults and children with exertion-related dehydration

Intervention: Drinking oral carbohydrate-electrolyte or alternative rehydrating liquids

Comparators: Drinking water.

Outcomes: Critical outcomes: Volume/hydration status (measured as cumulative urine volume, net fluid balance, hematocrit, hemoglobin, plasma volume change), vital signs (measured as heart rate), development of hyponatremia (measured as serum Na, serum/plasma osmolality).
Important outcomes: need for advanced medical care, important patient satisfaction (thirst perception, perceived intensity of gastric fullness or cramps, nausea, abdominal discomfort).

Study Designs: Randomized controlled trials (RCTs) and non-randomized studies (non-randomized controlled trials, interrupted time series, controlled before-and-after studies, cohort studies) are eligible for inclusion. Unpublished studies (e.g., conference abstracts, trial protocols) were excluded.

Timeframe: All years and all languages were included as long as there was an English abstract; Literature search updated to April 17, 2020. Re-run of the literature search completed on February 15, 2021, with no additional studies meeting inclusion criteria.

PROSPERO Registration CRD42020153077

NOTE FOR RISK OF BIAS: For randomized trials, bias was assessed with RoB2. For non-randomized studies, ROBINS-I was used for bias assessment. Bias was assessed per study, but where applicable, separate assessments were made for objective and subjective outcomes. Every study addressing a particular outcome may differ, to some degree, in risk of bias. To rate the overall certainty of evidence, the study limitations were summarized considering all the evidence from the multiple studies.

Consensus on Science

After the application of inclusion and exclusion criteria to the 2169 initial citations, a total of 22 studies were included. A summary of the evidence from these 22 studies is provided (Table 1).

4.0% - 9.0% carbohydrate-electrolyte drinks (I) compared with water (C)

For the critical outcome of volume/hydration status (measured as cumulative urine output, net fluid balance, plasma volume change or hematocrit), we identified very low certainty evidence (downgraded for risk of bias, imprecision and strongly suspected publication bias) from 9 RCTs (Amano 2019, 1494; Chang 2010, 3220; Pérez-Idárraga 2014, 1167; Shirreffs 2007, 173; Utter 2010, 85; Valiente 2009, 2210; Volterman 2014, 1257; Wijnen 2016, 1; Wong 2000, 375) and 4 non-RCTs (González-Alonso 1992, 399; Niksefat 2019, 43; Seifert 2006, 420; Wong 2011, 300) including 200 subjects.

  • One study showed a significant decrease in cumulative urine output with 4% carbohydrate-electrolyte (CE) drinks (Pérez-Idárraga 2014, 1167) compared with water (MD, -289 ml; 95% CI not calculable). In addition, 2 studies (González-Alonso 1992, 399; Seifert 2006, 420) showed a significant decrease in cumulative urine output with 6% CE drinks when compared with water (MD, 160 ml lower and MD, 465 ml lower; respectively; 95% CI not calculable). One study (Shirreffs 2007, 173) found no significant difference for cumulative urine output when comparing 6% CE drinks with water.
    Two studies (Chang 2010, 3220; Wong 2011, 300) showed a significant decrease of cumulative urine output when comparing 6.6% CE drinks with water (MD, 241 ml lower and MD, 277 ml lower; respectively; 95% CI not calculable). In 5 studies no significant difference in cumulative urine output was shown following rehydration using 6.5% CE (Amano 2019, 1494), 6.9% CE (Wong 2000, 375), 7% CE (Wijnen 2016, 1), 8% CE (Volterman 2014, 1257) or 8.75% CE drinks (Niksefat 2019, 43) compared with water.
  • In 4 studies, no significant difference was shown for net fluid balance 1 h after rehydration with 6% CE (Shirreffs 2007, 173), 6.9% CE (Wong 2000, 375), 7% CE (Wijnen 2016, 1) or 8% CE drinks (Volterman 2014, 1257) compared with water. In addition, in 3 studies, no significant difference was shown for net fluid balance 2 h after rehydration with 6% CE (Shirreffs 2007, 173), 7% CE (Wijnen 2016, 1) or 8% CE drinks compared with water.
  • No significant difference was shown in plasma volume change at 35 min after rehydration with 6% CE drinks in 2 studies (Utter 2010, 85; Valiente 2009, 2210) compared with water. Four studies (Amano 2019, 1494; Seifert 2006, 420; Wong 2011, 300; Wong 2011, 300) measured plasma volume (ml) or plasma volume change (%) 60 min after completion of rehydration with 6% CE (Seifert 2006, 420), 6.5% CE (Amano 2019, 1494), 6.6% CE (Wong 2011, 300) or 6.9% CE drinks (Wong 2000, 375) but did not show a difference compared with water. Also, no significant difference in plasma volume or plasma volume changes we shown at 1.5 h after rehydration with 6.5% CE (Amano 2019, 1494) or 6.6% CE drinks(Chang 2010, 3220) or 2 h after completion of rehydration with a 6% CE drink (Seifert 2006, 420).
  • Low certainty evidence (downgraded for risk of bias and imprecision) from one study (Niksefat 2019, 43) did not show a difference for hematocrit at 30 min following rehydration with a 8.75% CE drink compared with water.

For the critical outcome of vital signs (measured as heart rate) we identified 2 RCTs (Amano 2019, 1494; Kalman 2012, 1) and one non-RCT (Wong 2011, 300) including 53 subjects. Very low certainty evidence (downgraded for risk of bias, imprecision and strongly suspected publication bias) from two studies did not demonstrate a significant difference for heart rate 120 min after rehydration with a 5-6% CE drink (Kalman 2012, 1), or 60 min after rehydration with a 6.6% CE drink (Wong 2011, 300) compared with water. Similarly, very low certainty evidence (downgraded for risk of bias, imprecision and strongly suspected publication bias) from one study (Amano 2019, 1494) did not demonstrate a difference in heart rate at any timepoint following rehydration with a 6.5% CE drink compared with water.

For the critical outcome of hyponatremia (measured as serum sodium concentration or serum/plasma osmolality) we identified 3 RCTs (Amano 2019, 1494; Kalman 2012, 1; Wong 2000, 375;) and 4 non-RCTs (González-Alonso 1992, 399; Niksefat 2019, 43; Seifert 2006, 420; Wong 2011, 300) including 86 subjects.

  • Low certainty evidence (downgraded for risk of bias and imprecision) from one study reported a significant increase in serum sodium concentration 60 min after rehydration with a 6.9% CE drink (Wong 2000, 375) compared with water (MD, 4 mmol/L higher; 95% CI not calculable). However, in two other studies of low certainty (downgraded for risk of bias and imprecision) a significant difference in serum sodium concentration 75 min after rehydration with a 6% CE drink (González-Alonso 1992, 399) or 30 min after rehydration with a 8.75% CE drink (Niksefat 2019, 43) was not found compared with water.
  • Very low certainty evidence (downgraded for risk of bias, imprecision and strongly suspected publication bias) from two studies showed a significant increase in serum osmolality 60 min (Seifert 2006, 420) and 75 min (González-Alonso 1992, 399) after completion of rehydration with a 6% CE drink compared with water (MD, 5.9 mOsm/kg higher and 4.5 mOsm/kg higher; respectively; 95% CI not calculable). Three studies of very low certainty (downgraded for risk of bias, imprecision and strongly suspected publication bias) did not show a significant difference in serum osmolality at 120 min after completion of rehydration with a 6% CE drink (Seifert 2006, 420), 60 min after rehydration with a 6.9% CE drink (Wong 2000, 375) or 30 min after rehydration with a 8.75% CE drink (Niksefat 2019, 43) compared with water.
  • Very low certainty evidence (downgraded for risk of bias, imprecision and strongly suspected publication bias) from one study (Kalman 2012, 1) did not demonstrate a significant difference in plasma osmolality 120 min after completion of rehydration with a 5-6% CE drink compared with water. Similarly, in 2 other studies, no significant difference was found in plasma osmolality at 60 min after rehydration with a 6.5% CE drink (Amano 2019, 1494) or a 6.6% CE drink (Wong 2011, 300) or at 90 min after rehydration with a 6.5% CE drink (Amano 2019, 1494) compared with water.

For the important outcome of patient satisfaction (measured as thirst perception, nausea, gastric fullness or cramps ) we identified 5 RCTs (Kalman 2012, 1; Pérez-Idárraga 2014, 1167; Shirreffs 2007, 173; Volterman 2014, 1257; Wong 2000, 375) and one non-RCT (Wong 2011, 300) including 95 subjects.

  • Very low certainty evidence (downgraded for risk of bias, imprecision and strongly suspected publication bias) from 4 studies did not show a significant difference for thirst immediately after rehydration with a 4% CE (Pérez-Idárraga 2014, 1167), 5-6% CE (Kalman 2012, 1), 6% CE (Shirreffs 2007, 173) or 8% CE drink (Volterman 2014, 1257) compared with water. Similarly, no significant difference was shown for the perception of thirst 60 min after rehydration with a 5-6% CE (Kalman 2012, 1); 6% CE (Shirreffs 2007, 173) or 8% CE drink (Volterman 2014, 1257) compared with water. No significant difference was found for the perception of thirst at 120 min after rehydration with a 5-6% CE (Kalman 2012, 1); 6% CE (Shirreffs 2007, 173) or 8% CE drink (Volterman 2014, 1257) compared with water. Additionally, in 2 studies (Wong 2000, 375; Wong 2011, 300) no significant difference was found for the perception of thirst at any timepoint, when comparing a 6.6% or 6.9% CE drink with water.
  • Very low certainty evidence (downgraded for risk of bias, imprecision and strongly suspected publication bias) from 4 studies found no significant difference for gastric fullness immediately after rehydration with a 4% CE (Pérez-Idárraga 2014, 1167), 6% CE (Shirreffs 2007, 173), 6.6% CE (Wong 2011, 300) or 8% CE drink (Volterman 2014, 1257), compared with water. Similarly, no significant difference was found for gastric fullness 60 min after rehydration with a 6% CE (Shirreffs 2007, 173), 6.6% CE (Wong 2011, 300) or 8% CE drink (Volterman 2014, 1257) compared with water. No significant difference was found for gastric fullness 120 min after rehydration with a 6% CE (Shirreffs 2007, 173) or 8% CE drink (Volterman 2014, 1257) compared with water.
  • Very low certainty evidence (downgraded for risk of bias, imprecision and strongly suspected publication bias) from one study (Pérez-Idárraga 2014, 1167), did not show a significant difference for nausea immediately after rehydration with a 4% CE drink, compared with water. The same study did not show a difference in gastric cramps immediately after rehydration with a 4% CE solution, compared with water.
  • Low certainty evidence (downgraded for risk of bias and imprecision) from one study (Kalman 2012, 1) did not demonstrate a significant difference for gastric upset immediately, 60 min or 120 min after rehydration with a 5-6% CE drink compared with water.
  • Very low certainty evidence (downgraded for risk of bias, imprecision and strongly suspected publication bias) from 2 studies did not report a significant difference in bloating immediately after rehydration with a 5-6% CE (Kalman 2012, 1) or 6% CE drink (Shirreffs 2007, 173), compared with water. Similarly, in the same 2 studies, no significant difference in bloating 60 min or 120 min after rehydration with a 5-6% CE drink, or 1h or 2 h after rehydration with a 6% CE drink, compared with water.
  • Low certainty evidence (downgraded for risk of bias and imprecision) from 2 studies did not report a significant difference in abdominal discomfort immediately after rehydration with a 6.6% CE (Wong 2011, 300) or 6.9% CE drink (Wong 2000, 375), compared with water. Similarly, no significant difference was reported at 60 min after rehydration with a 6.6% CE (Wong 2011, 300) or 6.9% CE drink (Wong 2000, 375), compared with water.

We did not identify any evidence to address the important outcome need for advanced care.

0 - 3.9 % carbohydrate-electrolyte drinks (I) compared with water (C)

For the critical outcome of volume/hydration status (measured as cumulative urine output, net fluid balance, hematocrit, hemoglobin or plasma volume change), we identified low certainty evidence (downgraded for risk of bias and imprecision) from 5 RCTs (Amano 2019, 1494; Evans 2017, 344; Ismail 2007, 769; Saat 2002, 93; Seery 2016, 1013) and one non-RCT (Lau 2019, 1) including 53 subjects.

  • For the outcome of cumulative urine output, we identified very low certainty evidence (downgraded for risk of bias, imprecision and strongly suspected publication bias) from 5 RCTs (Amano 2019, 1494; Evans 2017, 344; Ismail 2007, 769; Saat 2002, 93; Seery 2016, 1013). Two RCTs showed a significant decrease in cumulative urine output following rehydration with a 0% CE (saline) drink (Evans 2017, 344) and 3.7% CE drink (Ismail 2007, 769) compared with water (MD, 416 ml lower; 95% CI 786 lower to 46 lower; MD, 174.5 ml lower; 95% CI not calculable; respectively). However, in 3 other randomized studies, no significant difference was found in cumulative urine volume, when comparing 2% CE (Amano 2019, 1494), 3.2% CE (Saat 2002, 93) or 3.9% CE (Seery 2016, 1013) drinks with water.
  • In 4 randomized studies of low certainty evidence (downgraded for risk of bias and imprecision), no significant difference in net fluid balance was shown 60 min after rehydration with 0% CE (saline) (Evans 2017, 344), 3.2% CE (Saat 2002, 93), 3.7% CE (Ismail 2007, 769) or 3.9% CE (Seery 2016, 1013) drinks compared with water. In addition, in 2 RCTs, no significant difference was shown in the net fluid balance 120 min after rehydration with a 0% CE (saline) (Evans 2017, 344) or 3.9% CE (Seery 2016, 1013) drinks compared with water.
  • In one non-randomized study (Lau 2019, 1) of low certainty (downgraded for risk of bias and imprecision) no significant difference was reported in hematocrit (MD, -2.0 %; 95% CI not calculable) or hemoglobin 60 min after rehydration with a 1.83% CE drink compared with water.
  • In 2 randomized studies, no significant difference was shown for plasma volume 60 min after rehydration with a 2% CE drink (Amano 2019, 1494) or for plasma volume change 60 min after rehydration with a 3.7% CE drink (Ismail 2007, 769), compared with water. Similarly, one study (Amano 2019, 1494) showed no significant difference in plasma volume 60 min after rehydration with a 2% CE drink, compared with water.

For the critical outcome of vital signs (measured as heart rate) we identified very low certainty evidence (downgraded for risk of bias, imprecision and strongly suspected publication bias) from one study including 10 subjects (Amano 2019, 1494). No significant difference was reported for heart rate following rehydration with a 2% CE solution, compared with water.

For the critical outcome of hyponatremia (measured as serum sodium concentration or serum/plasma osmolality) we identified 4 RCTs (Amano 2019, 1494; Ismail 2007, 769; Saat 2002, 93; Seery 2016, 1013) and one non-RCT (Lau 2019, 1) including 45 subjects.

  • Low certainty evidence (downgraded for risk of bias and imprecision) from one non-RCT and one RCT showed a significant increase in serum sodium concentration 60 min after rehydration with a 1.83% CE (Lau 2019, 1) or 3.7% CE (Ismail 2007, 769) drinks compared with water (MD, 3.4 mmol/L higher and MD, 2 mmol/L higher; respectively; 95% CI not calculable). However, a significant difference in serum sodium concentration was not shown in one other randomized study (Saat 2002, 93) when comparing rehydration with a 3.2% CE drink with water.
  • Low certainty evidence (downgraded for risk of bias and imprecision) from one non-RCT and one RCT showed a significant increase in serum osmolality 60 min after completion of rehydration with a 1.83% CE (Lau 2019, 1) or 3.7% CE (Ismail 2007, 769) drinks compared with water (MD, 9.0 mOsm/kg higher and MD, 4 mOsm/kg higher, respectively; 95% CI not calculable). In one randomized study (Saat 2002, 93) no significant difference was shown in serum osmolality at 60 min after rehydration with a 3.2% CE drink compared with water. Additionally, very low certainty evidence (downgraded for risk of bias, imprecision and strongly suspected publication bias) from 2 other randomized studies, did not show significant difference in plasma osmolality at 60 min after rehydration with 2% CE (Amano 2019, 1494) or 3.9% CE (Seery 2016, 1013) drinks compared with water. Furthermore, no significant difference was shown in plasma osmolality at 120 min after rehydration with 2% CE (Amano 2019, 1494) or 3.9% CE (Seery 2016, 1013) drinks compared with water.

For the important outcome of patient satisfaction (measured as thirst perception, nausea, gastric fullness or cramps) we identified low certainty evidence (downgraded for risk of bias and imprecision) from 3 RCTs including 25 subjects (Ismail 2007, 769; Saat 2002, 93; Seery 2016, 1013).

  • In 2 studies no significant difference was found for thirst, gastric fullness, cramps or nausea immediately after or 60 min after rehydration with a 3.2% CE (Saat 2002, 93) or 3.7% CE (Ismail 2007, 769) drink compared with water. Additionally, in one study (Seery 2016, 1013) no significant difference was found for the perception of thirst at any timepoint, when comparing rehydration with a 3.9% CE drink with water.

We did not identify any evidence to address the important outcome need for advanced care.

Skim or low-fat cow's milk (I) compared with water (C)

For the critical outcome of volume/hydration status (measured as cumulative urine output or net fluid balance) we identified very low certainty evidence (downgraded for risk of bias, imprecision and suspected publication bias) from 3 RCTs (Seery 2016, 1013; Shirrefs 2007, 173; Volterman 2014, 1275) and one non-RCT (Sayer 2020, 128) including 68 subjects.

  • 4 studies (Sayer 2020, 128; Seery 2016, 1013; Shirrefs 2007, 173; Volterman 2014, 1275) showed a significant decrease in cumulative urine output from rehydration with skim or low-fat cow's milk compared with water (MD, 368 ml lower; MD, 635 ml lower; MD, 594 ml lower and MD, 175 ml lower; respectively; 95% CI not calculable; P<0.05).
  • 3 studies (Seery 2016, 1013; Shirrefs 2007, 173; Volterman 2014, 1275) showed a significant increase in net fluid balance after 60 min (MD, 655 ml higher; MD, 368 ml higher and MD, 111 ml higher; respectively; 95% CI not calculable; P<0.05) and 120 min (MD, 675 ml higher; MD, 621 ml higher and MD, 179 ml higher; respectively; 95% CI not calculable; P<0.05) from rehydration with skim milk compared with water. In addition, one study (Sayer 2020, 128) showed a significant increase in net fluid balance at 30 min to 90 min post rehydration with low-fat cow's milk (MD, 0.26 L higher; 95% CI not calculable; P<0.05) or at 90 to 150 min post rehydration with low-fat cow’s milk (MD, 0.36 L higher; 95% CI not calculable; P<0.05), compared with water.

For the critical outcome hyponatremia (measured as plasma osmolality) we identified one RCT (Seery 2016, 1013) and one non-RCT (Sayer 2020, 128) including 19 subjects.

Very low certainty evidence (downgraded for risk of bias, imprecision and suspected publication bias) from one study (Sayer 2020, 128) showed a significant increase in plasma osmolality at 90 to 150 min post rehydration with skim milk compared with water (MD, 3 mOsm/kg higher; 95% CI not calculable; P<0.05). However, no significant difference was shown by low certainty evidence (downgraded for risk of bias and imprecision due to limited sample size and lack of data) from another study (Seery 2016, 1013) for plasma osmolality at 60 min and 120 min post rehydration with skim milk compared with water.

For the important outcome patient satisfaction (measured as perception of thirst, gastric fullness or bloating) we identified 3 RCTs (Volterman 2014, 1275; Seery 2016, 1013; Shirrefs 2007, 173) and one non-randomized study (Sayer 2020, 128) including 68 subjects.

  • Very low certainty evidence (downgraded for risk of bias, imprecision and suspected publication bias) from 3 studies (Sayer 2020, 128; Shirrefs 2007, 173; Volterman 2014, 1275), did not demonstrate a significant difference in the perception of thirst immediately after rehydration with skim or low-fat cow's milk compared with water.

Very low certainty evidence (downgraded for risk of bias, imprecision and suspected publication bias) from 3 studies did not demonstrate a significant difference for thirst 90 min after rehydration with low-fat cow's milk (Sayer 2020, 128) or 60-120 min after rehydration with skim milk (Shirrefs 2007, 173; Volterman 2014, 1275) compared with water. In addition, low certainty evidence from one study (Seery 2016, 1013) did not demonstrate a significant difference for the perception of thirst at any timepoint after rehydration with skim milk, compared with water.

  • Very low certainty evidence (downgraded for risk of bias, imprecision and suspected publication bias) from one study (Sayer 2020, 128) showed significantly more gastric fullness immediately after rehydration with low-fat cow's milk (MD, 10 higher (30 min rehydration period) and MD, 34 higher (90 min rehydration period); 95% CI not calculable; P<0.05), 30 min after rehydration with milk (MD, 18 higher (90 min rehydration period); 95% CI not calculable; P<0.05) and 90 min after rehydration with milk (MD, 17 higher (30 min rehydration period) and MD, 11 higher (90 min rehydration period); 95% CI not calculable, P<0.05) compared with water. Very low certainty evidence (downgraded for risk of bias, imprecision and suspected publication bias) from 2 other studies (Shirrefs 2007, 173; Volterman 2014, 1275) did not show a significant difference in gastric fullness immediately after rehydration with skim milk, compared with water.
    Very low certainty evidence (downgraded for risk of bias, imprecision and suspected publication bias) from 2 studies (Shirrefs 2007, 173; Volterman 2014, 1275) did not show a significant difference in gastric fullness at 60 min or 120 min after rehydration with skim milk compared with water.
  • Low certainty evidence (downgraded for risk of bias and imprecision) from one study (Seery 2016, 1013) did not demonstrate a significant difference in bloating at any timepoint after rehydration with skim milk compared with water.

Very low certainty evidence (downgraded for risk of bias, imprecision and strongly suspected publication bias) from one study (Sayer 2020, 128) showed significantly more bloating immediately after rehydration with low-fat cow's milk (MD, 9 higher (30 min rehydration period) and MD, 9 higher (90 min rehydration period); 95% CI not calculable; P<0.05), 30 min after rehydration with milk (MD, 14 higher (90 min rehydration period); 95% CI not calculable; P<0.05) and 90 min after rehydration with milk (MD, 10 higher (30 min rehydration period) and MD, 5 higher (90 min rehydration period); 95% CI not calculable, P<0.05) compared with water. Very low certainty evidence (downgraded for risk of bias, imprecision and strongly suspected publication bias) from one other study (Shirrefs 2007, 173) did not show a significant difference in bloating immediately after or 120 min after rehydration with skim milk, compared with water.

We did not identify any evidence to address the critical outcome vital signs or the important outcome need for advanced care.

Coconut water (as fresh coconut water or coconut water from concentrate) (I) compared with water (C)

For the critical outcome of volume/hydration status (measured as cumulative urine output, net fluid balance, plasma volume change) we have identified 3 RCTs including 30 subjects (Ismail 2007, 769; Pérez-Idárraga 2014, 1167; Saat 2002, 93).

  • Very low certainty evidence (downgraded for risk of bias, imprecision due to limited sample sizes and lack of data, and suspected publication bias) from 3 studies (Ismail 2007, 769; Pérez-Idárraga 2014, 1167; Saat 2002, 93) did not demonstrate a significant difference in cumulative urine output from rehydration with fresh coconut water compared with water.
  • Low certainty evidence (downgraded for risk of bias, imprecision due to limited sample sizes and lack of data) from 2 studies (Ismail 2007, 769; Saat 2002, 93) did not demonstrate a significant difference in net fluid balance 60 min after rehydration with fresh coconut water compared with water.
  • Low certainty evidence from one study (Ismail 2007, 769) did not demonstrate a significant difference in plasma volume change 60 min after rehydration with fresh coconut water compared with water.

For the critical outcome vital signs (measured as heart rate) we identified low certainty evidence (downgraded for risk of bias and imprecision) from one study (Kalman 2012, 1) including 12 subjects. No significant difference was reported for heat rate 120 min after rehydration with fresh coconut water or coconut water from concentrate compared with water.

For the critical outcome development of hyponatremia (measured as serum sodium concentration or serum/plasma osmolality) we identified low certainty evidence (downgraded for risk of bias and imprecision) from 3 RCTs including 30 subjects (Ismail 2007, 769; Kalman 2012, 1; Saat 2002, 93).

  • One study (Ismail 2007, 769) showed a significant increased serum sodium concentration 60 min after rehydration with fresh coconut water compared with water (MD, 2 mmol/l higher; 95% CI not calculable; P<0.05). However, no significant difference was shown in another study (Saat 2002, 93) for serum sodium concentration 60 min after rehydration with fresh coconut water compared with water.
  • One study (Ismail 2007, 769) showed a significant increase in serum osmolality 60 min after rehydration with fresh coconut water compared with water (MD, 3 mOsm/kg higher; 95% CI not calculable; P<0.05). However, another study (Saat 2002, 93) did not demonstrate a significant difference in serum osmolality 60 min after rehydration with fresh coconut water compared with water.
  • One study (Kalman 2012, 1) did not demonstrate a significant difference in plasma osmolality 120 min after rehydration with fresh coconut water compared with water. However, the same study showed a significant increase in plasma osmolality 120 min after rehydration with coconut water from concentrate compared with water (MD, 1.5 higher; 95% CI not calculable; P=0.049).

For the important outcome patient satisfaction (measured as the perception of thirst, gastric fullness, bloating or discomfort, nausea) we identified 4 RCTs including 42 subjects (Ismail 2007, 769; Kalman 2012, 1; Pérez-Idárraga 2014, 1167; Saat 2002, 93).

  • Very low certainty evidence (downgraded for risk of bias, imprecision and strongly suspected publication bias) from 4 studies (Ismail 2007, 769; Kalman 2012, 1; Pérez-Idárraga 2014, 1167; Saat 2002, 93) did not demonstrate a significant difference in the perception of thirst immediately after rehydration with fresh coconut water compared with water. Two studies (Ismail 2007, 769; 1167; Saat 2002, 93) did not demonstrate a significant difference in the perception of thirst 60 min after rehydration with fresh coconut water compared with water. Also, no significant difference was reported for thirst 60 or 120 min after rehydration with fresh coconut water or coconut water from concentrate compared with water in one study (Kalman 2012, 1).
  • Very low certainty evidence (downgraded for risk of bias, imprecision and strongly suspected publication bias) from 3 studies (Ismail 2007, 769; Pérez-Idárraga 2014, 1167; Saat 2002, 93) did not demonstrate a significant increase in gastric fullness immediately after rehydration with fresh coconut water compared with water. In addition, low certainty evidence (downgraded for risk of bias and imprecision) from 2 studies (Ismail 2007, 769; Saat 2002, 93) did not demonstrate a significant difference in gastric fullness 60 min after rehydration with fresh coconut water compared with water.
  • Very low certainty evidence (downgraded for risk of bias, imprecision and strongly suspected publication bias) from 2 studies (Ismail 2007, 769; Pérez-Idárraga 2014, 1167) did not demonstrate a significant difference in nausea immediately after rehydration with fresh coconut water compared with water. Low certainty evidence (downgraded for risk of bias and imprecision) from one study (Saat 2002, 93) showed a significant decrease in nausea immediately and 60 min after rehydration with fresh coconut water, compared with water (MD, 1.75 lower and MD, 1.25 lower); respectively; 95% CI not calculable; P<0.05). In one study (Ismail 2007, 769) no difference in nausea was shown 60 min after rehydration with fresh coconut water compared with water.
  • Low certainty evidence from one study (Saat 2002, 93) showed significantly less upset stomach immediately after rehydration with fresh coconut water compared with water (MD, 1 lower, 95% CI not calculable; P<0.05). However, low certainty evidence (downgraded for risk of bias and imprecision) did not demonstrate a significant difference for gastric discomfort immediately after rehydration with fresh coconut water (Ismail 2007, 769; Kalman 2012, 1) or coconut water from concentrate (Kalman 2012, 1) compared with water. In addition, low certainty evidence (downgraded for risk of bias and imprecision) from one study (Kalman 2012, 1) did not demonstrate a significant difference for gastric discomfort 60 min after rehydration with fresh coconut water or coconut water from concentrate compared with water. However, the same study showed a significant increase in gastric discomfort 120 min after rehydration with fresh coconut water or coconut water from concentrate compared with water (MD, 1.84 higher and MD, 1.47 higher; respectively; 95% CI not calculable; P<0.05).
  • Very low certainty evidence (downgraded for risk of bias, imprecision and strongly suspected publication bias) from one study (Pérez-Idárraga 2014, 1167) did not demonstrate a significant difference in gastric cramps immediately after rehydration with fresh coconut water compared with water.
  • Low certainty evidence (downgraded for risk of bias and imprecision) from one study (Kalman 2012, 1) did not demonstrate a significant difference in bloating immediately, 60 min or 120 min after rehydration with fresh coconut water or coconut water from concentrate compared with water.

We did not identify any evidence to address the important outcome need for advanced medical care.

Regular beer (4.5 – 5% alcohol) (I) compared with water (C)

For the critical outcome of volume/hydration status (measured as cumulative urine output, net fluid balance, hematocrit, plasma volume change) we identified 3 RCTs including 38 subjects (Jimenez-Pavon 2015, 1; Flores-Salamance 2014, 1175; Wijnen 2016, 1).

  • Very low certainty evidence (downgraded for risk of bias, imprecision and lack of data, and suspected publication bias) from 2 studies (Jimenez-Pavon 2015, 1; Wijnen 2016, 1) did not demonstrate a significant difference in cumulative urine output from rehydration with regular beer compared with water. However, in one study (Flores-Salamance 2014, 1175), rehydration with regular beer compared with water resulted in a statistically significant increase of cumulative urine output (MD, 444 ml higher; 95% CI not calculable, P=0.043).
  • Very low certainty evidence (downgraded for risk of bias, imprecision due to limited sample sizes and lack of data, and suspected publication bias) from one study (Wijnen 2016, 1) did not demonstrate a significant difference in net fluid balance 60 min after rehydration with regular beer compared with water. Very low certainty evidence (downgraded for risk of bias, imprecision due to limited sample sizes and lack of data, and suspected publication bias) from 2 studies (Jimenez-Pavon 2015, 1; Wijnen 2016, 1), did not demonstrate a significant difference in net fluid balance 120 min after rehydration with regular beer compared with water.
  • Low certainty evidence (downgraded for risk of bias, imprecision) from one study (Jimenez-Pavon 2015, 1) did not demonstrate a significant difference in hematocrit or plasma volume change after rehydration with regular beer compared with water.

For the critical outcome of development of hyponatremia (measured as serum sodium concentration) we identified low certainty evidence (downgraded for risk of bias and imprecision due to limited sample size and lack of data) from one study (Jimenez-Pavon 2015, 1) including 16 subjects. No significant difference was found in serum sodium concentration following rehydration with regular beer compared with water.

We did not identify any evidence to address the critical outcome of vital signs or the important outcomes need for advanced care or important patient satisfaction.

Low-alcohol beer (0.5% – 2%) (I) compared with water (C)

For the critical outcome of volume/hydration status (measured as cumulative urine output or net fluid balance) we identified very low certainty evidence (downgraded for risk of bias, imprecision and suspected publication bias) from 2 RCTs including 22 subjects (Flores-Salamance 2014, 1175; Wijnen 2016, 1):

  • No significant difference was found in 2 studies (Flores-Salamance 2014, 1175; Wijnen 2016, 1) for cumulative urine output after rehydration with low-alcohol beer (0.5% or 2%, respectively) compared with water.
  • No significant difference was found in one study (Wijnen 2016, 1) in net fluid balance at 60-120 min after rehydration with low-alcohol beer (2%) compared with water.

We did not identify any evidence to address the critical outcomes of vital signs or development of hyponatremia or the important outcomes need for advanced care or patient satisfaction.

Non-alcoholic beer (0%) (I) compared with water (C)

For the critical outcome of volume/hydration status (measured as cumulative urine output or net fluid balance) we identified very low certainty evidence (downgraded for risk of bias, imprecision and suspected publication bias) from one RCT including 11 subjects (Wijnen 2016, 1). No significant difference in cumulative urine output or net fluid balance was found at 60-120 min after rehydration with non-alcoholic beer compared with water.

Treatment Recommendations

  • We recommend the use of any readily available rehydration drink or water for treating exertion related dehydration in the first aid setting. (Good Practice Statement)
  • We suggest rehydration for exertion-related dehydration using a 4-9% carbohydrate-electrolyte drink. Alternative rehydration options include 0-3.9% carbohydrate-electrolyte drinks, water, coconut water or skim or low-fat cow's milk (weak recommendation, very low certainty evidence).
  • There is insufficient evidence to recommend for or against rehydration with beer (0-5% alcohol).

Justification and Evidence to Decision Framework Highlights

This topic was prioritized by the First Aid Task Force based on the knowledge of new identified studies that were published since the previous CoSTR in 2015.

Although there is variability among the identified studies, we identified a potential beneficial effect with use of CE drinks compared with water for many of the reviewed outcomes. Differences seen in urine production between the various drinks used for rehydration were discussed by the task force and are likely a result of the drink composition. Ingested drinks with high energy content (i.e. from carbohydrate, fat, protein or alcohol) will empty from the stomach more slowly than drinks containing no energy. They will therefore potentially reduce or delay diuresis when compared with water. In other words, when large volumes of dilute drinks are consumed, a fall in serum electrolyte concentrations and osmolality occurs and urine production and excretion are stimulated. However, if the electrolyte concentration of a rehydration drink is high, this will maintain high serum or plasma electrolyte concentration and osmolality, reducing the excretion of dilute urine. As a consequence, low cumulative urine outputs and, hence, high net fluid balances can be associated with improved fluid retention and, hence, effective rehydration. (Maugan 2016, 717; Volterman 2014, 1257)

In making these recommendations, the First Aid Task Force considered the following:

  • In cases of exertional dehydration, it is most important to rehydrate as soon as possible. The choice will often be made based on what the dehydrated person is willing to drink; the drink needs to be palatable to increase patient compliance with the need for increased fluid intake. This is suggested as a good practice statement.
  • First aid providers are commonly recruited to assist at first aid stations located at sporting and challenge events where exercise-induced dehydration is a common problem. It may not be possible to determine the exact quantity or percent of fluid loss in the first aid setting, nor the volume required for adequate rehydration.
  • Skim or low-fat cow's milk appears to have a similar water, energy and macronutrient content as sports drinks. This explains the beneficial effects of milk on rehydration. However, rehydration with milk may be associated with other issues of patient satisfaction or compliance when compared with water. In addition, in some regions, the prevalence of lactose intolerance is higher than in other regions, making milk a less suitable rehydration solution. The use of milk by people with lactose intolerance may induce adverse effects such as diarrhea, which could hamper the effects of rehydration. A further challenge is that milk generally needs refrigeration, which may not always be accessible.
  • Coconut water may be more costly in geographic regions where fresh coconuts are not readily available. In addition, some people may find coconut water less palatable than water.
  • The use of alcoholic beverages may have other unwanted effects and is probably not recommended as a rehydration drink in competition for athletes. Moreover, alcohol may have a diuretic effect.
  • This PICO question specifically looked at sodium levels reported after rehydration in the included studies and agreed that oral rehydration with CE drinks may assist in preventing hyponatremia, although this review did not specifically address exercise-associated hyponatremia. In addition, all included studies conducted exercise in a controlled environment and for a specific time period. Extreme events such as ultramarathons were not included in the evidence evaluation.
  • Excessive fluid consumption may lead to an electrolyte imbalance, specifically, a drop in plasma/serum sodium concentration. This reduction in sodium concentration may result in clinical hyponatremia, a rare condition but not infrequently seen in endurance athletes. Signs and symptoms of exertional hyponatremia include excessive drinking, nausea, vomiting, dizziness, muscular twitching, peripheral tingling or swelling, headache, disorientation, altered mental status, physical exhaustion, pulmonary edema, seizures, and cerebral edema.
  • If clean, drinkable water is available, its cost, relative to CE drinks, make it an acceptable alternative. However, water may require a longer time to rehydrate and, in some cases, may be associated with an increased risk of hyponatremia.

This CoSTR differs from the previous CoSTR in 2015 in the following ways:

  • We limited the review to rehydration drinks for which more than one study was identified. In addition, the inclusion of studies was made based on reported outcomes. The Task Force discussed in advance which outcomes should be included. Based on this, no studies were included for any type of tea.
  • This review also includes beer (in percentages ranging from 0 to 5%). Based on the current insufficient evidence we were not able to make a recommendation for or against the use of beer (in any percentage).
  • How can a first aid provider determine the amount of liquid required for rehydration?
  • How can a first aid provider determine the amount of time required to ensure adequate rehydration?
  • How can a first aid provider determine the chemical composition of available rehydration products?

Knowledge Gaps

  • How can a first aid provider determine the amount of liquid required for rehydration?
  • How can a first aid provider determine the amount of time required to ensure adequate rehydration?
  • How can a first aid provider determine the chemical composition of available rehydration products?

Attachments

FA-584-Et D-Exertional-dehydration

References

References listed alphabetically by first author last name in this citation format (Circulation)

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