Iterative assessment of a sports rehydration beverage containing a novel amino acid formula on water uptake kinetics.

PURPOSE: Rapid gastric emptying and intestinal absorption of beverages is essential for rapid rehydration, and certain amino acids (AA) may augment fluid delivery. Three sugar-free beverages, containing differing AA concentrations (AA + PZ), were assessed for fluid absorption kinetics against commercial sugar-free (PZ, GZ) and carbohydrate-containing (GTQ) beverages. METHODS: Healthy individuals (n = 15-17 per study) completed three randomised trials. Three beverages (550-600 mL) were ingested in each study (Study 1: AA + PZ [17.51 g/L AA], PZ, GZ; Study 2: AA + PZ [6.96 g/L AA], PZ, GZ; Study 3: AA + PZ [3.48 g/L AA], PZ, GTQ), containing 3.000 g deuterium oxide (D2O). Blood samples were collected pre-, 2-min, 5-min, and every 5-min until 60-min post-ingestion to quantify maximal D2O enrichment (Cmax), time Cmax occurred (Tmax) and area under the curve (AUC). RESULTS: Study 1: AUC (AA + PZ: 15,184 ± 3532 δ‰ vs. VSMOW; PZ: 17,328 ± 3153 δ‰ vs. VSMOW; GZ: 17,749 ± 4204 δ‰ vs. VSMOW; P ≤ 0.006) and Tmax (P ≤ 0.005) were lower for AA + PZ vs. PZ/GZ. Study 2: D2O enrichment characteristics were not different amongst beverages (P ≥ 0.338). Study 3: Cmax (AA + PZ: 440 ± 94 δ‰ vs. VSMOW; PZ: 429 ± 83 δ‰ vs. VSMOW; GTQ: 398 ± 81 δ‰ vs. VSMOW) was greater (P = 0.046) for AA + PZ than GTQ, with no other differences (P ≥ 0.106). CONCLUSION: The addition of small amounts of AA (3.48 g/L) to a sugar-free beverage increased fluid delivery to the circulation compared to a carbohydrate-based beverage, but greater amounts (17.51 g/L) delayed delivery.

Arterial Pressure and the Rate of Elimination of Crystalloid Fluid.

Excretion of crystalloid fluid is slow during general anesthesia. The distribution and elimination of buffered Ringer's solution were analyzed to determine whether the rate of elimination correlates with a hemodynamic factor, consciousness, patient posture, or the type of general anesthesia. Data were derived from 4 separately published studies in which 30 volunteers and 48 anesthetized patients had received 0.833 (1 series 0.667) mL/kg/min of lactated or acetated Ringer's solution over 30 minutes. Frequent measurements of the blood hemoglobin and mean urinary excretion were used as input in a kinetic analysis according to a 2-volume model and covariates, using microconstants and mixed-effects modeling software.The results show that rate of elimination of crystalloid fluid decreased with the mean arterial pressure (MAP) and patient age, but was unaffected by consciousness and inhalational or intravenous anesthesia. The elimination rate constant was 6.5 (95% confidence interval, 5.2-7.9) × 10 × (MAP/mean MAP) × (Age/mean Age). The mean MAP for the 2108 data points was 81.3 mm Hg and the mean age was 40 years. The central fluid space that was expanded by infused fluid (Vc, plasma volume) increased with body weight but decreased with general anesthesia and with reductions of MAP.Simulations revealed a more than 10-fold difference in the excreted fluid volume after a theoretical 30-minute infusion, depending on whether the MAP was 50 or 100 mm Hg.In conclusion, the rate of elimination of crystalloid fluid decreased in proportion to MAP but was independent of general anesthesia and moderate-sized surgery.

The impact of acepromazine on the efficacy of crystalloid, dextran or ephedrine treatment in hypotensive dogs under isoflurane anesthesia.

OBJECTIVE: To determine the impact of acepromazine on the cardiovascular responses to three treatments for hypotension in dogs during deep isoflurane anesthesia. STUDY DESIGN: Prospective blinded randomized cross-over experimental design. ANIMALS: Six adult (2.5 ± 0.5 year old) healthy mixed breed dogs (24.2 ± 7.6 kg). METHODS: Anesthesia was induced with propofol (4-6 mg kg(-1) , IV) and maintained with isoflurane. Each dog received six treatments separated by at least 5 days. Once instrumented, dogs randomly received acepromazine (0.05 mg kg(-1) ) (Ace) or saline (equal volume) (Sal) IV and end-tidal isoflurane (E'Iso) was adjusted to achieve hypotension, defined as a mean blood pressure between 45 and 50 mmHg. Dogs randomly received dextran (D) (7 mL kg(-1) ) or lactated Ringer's (LR) (20 mL kg(-1) ) over 14 minutes, or ephedrine (Eph) (0.1 mg kg(-1) followed by 10 µg kg(-1) minute(-1) ) throughout the study. Measurements were taken at baseline, 5, 10, 15, 20, 30, and 40 minutes. Data were analyzed with a Latin Square in two factors (Ace/Sal and treatment) for repeated measures, with further comparisons if appropriate (p < 0.05). RESULTS: E'Iso producing hypotension was significantly less following Ace (2.07 ± 0.23%) than Sal (2.43 ± 0.23%). No improvement in cardiac output (CO) was observed with D or LR. LR initially intensified hypotension with a significant reduction in SVR, while D caused a minor improvement in ABP. Eph produced a significant increase in ABP, CO, hemoglobin, oxygen content and delivery. Pre-treatment with Ace minimized ABP improvements with all treatments. CONCLUSIONS AND CLINICAL RELEVANCE: Acepromazine (0.05 mg kg(-1) IV) enhanced the hypotensive effect of isoflurane, although it maintained CO. Administration of LR significantly worsens ABP initially by further vasodilation. D caused minimal improvement in ABP. At the infusion studied, Eph effectively countered the cardiovascular depression produced by deep isoflurane anesthesia, but extremes in ABP associated with initial vasoconstriction prevent our recommendation at this dose.

Distribution and elimination of crystalloid fluid in pre-eclampsia.

Pre-eclampsia (PE) is a disease of pregnancy associated with peripheral oedema and hypovolaemia, but few details are known about how women with PE handle a volume load of crystalloid fluid compared with healthy pregnant women. To study this issue, Ringer's acetate solution (12.5 ml/kg of body weight) was given by intravenous infusion over 30 min to eight women with PE and to eight healthy pregnant women matched with respect to gestational week (mean, 34 weeks). Venous blood was sampled and excreted urine was collected over 90 min to study the time course of the volume expansion by means of volume kinetic analysis. The results show that the size of the central body fluid space expanded by the infused fluid was smaller in PE (mean, 2940 ml compared with 4240 ml respectively; P<0.04), and the clearance constants for distribution (100 ml/min compared with 43 ml/min; P<0.04) and elimination (125 ml/min compared with 36 ml/min; P<0.02) were higher in the women with PE than in the controls. Less excess volume accumulated in the central body fluid space in the presence of PE, whereas the rates of distribution and elimination were higher during and for 15 min after the infusion. It is concluded that Ringer's acetate solution fluid is both distributed and eliminated faster in women with PE than in matched pregnant controls.

Distribution of normal saline and 5% albumin infusions in septic patients.

OBJECTIVE: To determine the relative distribution of fluid within the extracellular fluid volume (ECFV) after infusing either normal saline or 5% albumin in septic, critically ill patients. DESIGN: Prospective, randomized, unblinded, interventional study. SETTING: Intensive care unit in a 450-bed, tertiary care, teaching hospital. PATIENTS: Septic, critically ill patients (n = 18). INTERVENTIONS: Infusion of either normal saline or 5% albumin to a hemodynamic end point determined by the patient's clinician. MEASUREMENTS AND MAIN RESULTS: Plasma volume (PV), ECFV, cardiac index, and arterial oxygen content were measured immediately before (baseline) and after each fluid infusion. PV and ECFV were measured by dilution of 131I-albumin and 35S sodium sulfate, respectively. Interstitial fluid volume (ISFV) was calculated as ECFV - PV. Baseline values for PV, ISFV, ECFV, and oxygen delivery index did not differ between treatment groups. Infusion of normal saline increased the ECFV by approximately the volume infused, and the expansion of the PV to ISFV was in a ratio of 1:3. Infusion of 5% albumin increased the ECFV by double the volume infused, with both the PV and ISFV expanding by approximately equal amounts. Oxygen delivery index did not increase after either infusion due to the effect of hemodilution. CONCLUSION: Expansion of the ECFV in excess of the volume of 5% albumin infused suggests that fluid may move from the intracellular fluid volume to the ECFV in septic patients who receive this fluid.

Gastric emptying of oral rehydration solutions at rest and after exercise in horses.

We examined the gastric emptying (GE) of oral rehydration solutions (ORS) at rest and after exercise in four Standardbred horses. In one study isotonic, cold isotonic (5 degrees C), isotonic containing glucose and hypertonic fluid were tested at rest. In another study, isotonic fluid was given following a bout of treadmill exercise at 70 per cent VO2 max until exhaustion or at rest. In both studies, a single dose of 8 litres was given via nasogastric tube. GE and electrolyte concentrations (Na+, K+ and Cl-) of the stomach content were measured at 15 minutes intervals for one hour. In both studies, 90 per cent of the fluid was emptied within 15 minutes of administration. There was no treatment effect on electrolyte concentrations in either study but significant changes did occur over time. The data showed that GE is unlikely to significantly affect rehydration.

The effects of tonicity, glucose concentration and temperature of an oral rehydration solution on its absorption and elimination.

Effects of different tonicities, glucose concentrations and temperatures of an oral rehydration solution (ORS) on its uptake and elimination in resting horses were studied. Fluid and electrolyte deficits similar to those occurring during prolonged exercise were induced by the administration of 1 mg/kg bwt of frusemide i.m., 3 h prior to the ORS. Fluid was administered via nasogastric tube at a volume equivalent to 4% bodyweight, which approximated diuretic induced losses. The uptake of fluid was evaluated by changes in haematocrit (PCV) and plasma total protein concentration (TP). Changes in electrolyte balance were studied by measurements of plasma and urinary electrolyte concentrations while changes in bodyweight, urine volume and faecal water content were used to estimate retention of the administered fluids. Changes in acid base status were assessed from venous blood bicarbonate values. Fluid tonicity had a major effect on the uptake and elimination of the ORS. The hypertonic fluid (628 mOsm/kg bwt) was less rapidly absorbed and resulted in more rapid fluid and electrolyte excretion than the isotonic (314 mOsm/kg bwt) and hypotonic (water) fluids. The inclusion of glucose did not enhance the absorption of the ORS, although fluids containing higher concentrations of electrolytes resulted in more rapid elimination of fluid in urine. There was a direct relationship between higher concentrations of sodium in the ORS, plasma sodium values and osmolality. Fluid temperature (5, 21 and 37 degrees C) had no demonstrable effect on absorption of the ORS and elimination of fluids post administration. We concluded that while glucose concentration and fluid temperature have minimal effects on fluid absorption and elimination, fluid tonicity was a key element in the uptake and elimination of orally administered fluid. These findings are likely to be of relevance when administering ORS in association with exercise.

Studies of water movement across the gut using oral rehydration solutions in a rat perfusion model.

AIM: To measure water influx and efflux, as well as net water, sodium and potassium absorption from a range of oral rehydration solutions (ORS) in which the glucose content had been partially replaced with the amino acid leucine or with food supplements. METHODS: A series of in vivo steady-state perfusion studies in normal rat intestine. The oral rehydration solutions contained 60 or 90 mmol/L of sodium. The reference solution used was the World Health Organization (WHO) formula. RESULTS: There was a significant negative correlation between the oral rehydration solution osmolality and net water absorption (r = -0.722, P < 0.05). The highest net water absorption occurred using comminuted chicken supplemented oral rehydration solution containing 60 mmol/L sodium (P < 0.001). This oral rehydration solution also showed a significant increase in the rate of influx of water (P < 0.05) in comparison with the WHO formula containing 60 mmol/L sodium. CONCLUSION: This work provides further evidence that food-based oral rehydration solutions, including non-vegetable sources, may have a useful role to play in the management of patients with acute diarrhoea.

[Transepithelial transport of water, sodium, and glucose of oral hydration solutions in jejunal loops of rats undergoing "in vivo" perfusion]. / Transporte transepitelial de água, sódio e glicose de soluções de hidratação oral em alças jejunais de ratos submetidos à perfusão "in vivo".

There are several different oral hydration solutions of variable composition commercially available besides WHO 90. The purpose of this paper was to establish the type of solution more favorable to hydroelectrolytic transport. Water, Na and glucose transport of oral hydration solutions were measured by analysis of 728 samples from perfusions with 7 different solutions in jejunal loops of rats "in vivo". The following solutions were studied: homemade (96), Rehidrat (96), Hydrax (104), WHO 90 (104), WHO 60 (112), Pedyalite 30 (104), Pedyalite 90 (112) and a control solution (144). Hypotonic solutions with a molar ratio Na/glucose 2:1, had the greatest water absorption (homemade and WHO 60), while the solution with 90 mEq/L of Na had the greatest absorption of this ion (Pedyalite 90, WHO 90). Regarding glucose transport, Pedyalite 90 promoted the greater absorption (25 g/L). Solution with 30 mEq/L of Na and high osmolality resulted in water and Na secretion (Pedyalite 30).

Comparison of rat and human intestinal perfusion models for assessing efficacy of oral rehydration solutions.

The optimal composition for oral rehydration solutions remains controversial. Animal models have been used to assess the efficacy of new formulations but the relevance of these studies to the handling of oral rehydration solutions in human intestine during diarrhoeal disease states remains uncertain. Using steady state perfusion techniques we have compared water and solute transport from a variety of oral rehydration solutions in both the entire rat small intestine and in the human jejunum. Overall the pattern of water, sodium and glucose absorption was similar from the three oral rehydration solutions tested, indicating close parallelism between the two models despite the species and methodological differences. Although the relationship between the findings of these studies to the handling of oral rehydration solution in diarrhoeal disease states remains uncertain, we believe they do support the view that animal models may have a part to play in the preliminary screening of oral rehydration solutions before clinical trial.

Hiperglicemia en lactantes con deshidratación / Hyperglicemia in infants with dehydration

Se estudian 171 pacientes internados de los cuales fuerón seleccionados 70 que tenian deshidratación del 10 al 15 o niños con deshidratación moderada, pero con un estado general compremetido y que requerían hidratación parenteral; a estos se los determinó la glicemia. El objetivo es determinar la insidencia de la hiperglicemia y proponer un esquema de tratamiento. La insidencia de la hiperglicemia fué de 40 (28 casos). La rehidratación con Solución Fisiológica normalizó la hiperglicemia en el 68 de los casos a las tres horas 5 no se normalizo a las seis horas(1 caso). Con Solución Glucosada Clorurada al 2,5 de 7 casos 3 permanecierón con hiperglicemia a las seis horas. Con Solución Glucosada al 5 no se normalizo en ningún caso. La ganancia de peso las tres horas se observó en 86 de los casos. El grado de deshidratación, 12 al 15 en la primera hora fué de un 61 a las seis horas.