Improving interpretation of metabolic acid-base disorders by correcting pH-dependent bias in base excess partitioning.

Acid-Base Disturbances After Cardiac Surgery: A Cohort Study Using the Physicochemical Approach.

Background: High-chloride solutions such as 0.9% saline are widely used for medication dilution in intensive care units (ICUs) and are an underrecognized source of hyperchloremia and acid–base disturbances. Excess chloride reduces the strong ion difference (SID), contributing to hyperchloremic metabolic acidosis and worse clinical outcomes. This study evaluated the impact of replacing isotonic saline with 5% dextrose as a diluent on ICU outcomes in mechanically ventilated patients. Methods: In this retrospective cohort study, 4347 adult ICU patients requiring ≥12 h of mechanical ventilation were analyzed across two periods with different diluent strategies (2015–2018: saline-based; 2019–2025: chloride-sparing, dextrose-based). Demographics, comorbidities, illness severity (APACHE II, SOFA), fluid exposure, SID, and laboratory values over the first 48 h were compared. Predictors of mortality were identified using multivariate logistic regression. Results: Mortality decreased from 44.6% to 39.2% after adoption of chloride-sparing diluents (absolute reduction 5.4%, p = 0.003), despite similar renal function across periods. The later cohort demonstrated significantly higher SID (median 39 vs. 38 mmol/L; p < 0.001), lower chloride levels, and more favorable acid–base profiles. In 2015–2018, chloride showed a strong association with mortality (~12–13% increased odds per mmol/L), while in 2019–2025 the association persisted but was attenuated (~2% per mmol/L). SID emerged as a significant marker of improved acid–base balance after the diluent transition. pH remained the most powerful predictor of mortality in both periods. Mean glucose levels increased by ~30–40 mg/dL after switching to dextrose diluents, although insulin requirements did not change. Conclusions: Transitioning from chloride-rich to chloride-sparing diluents was associated with reduced ICU mortality and improved acid–base balance, without changes in renal function. However, modestly increased glucose levels highlight the need for strict glycemic monitoring. These findings support chloride-sparing strategies with robust glycemic monitoring in critical care.

Sea trout (Salmo trutta) migrate to the seawater (SW) for increased food availability. However, heavy infestations with salmon louse (Lepeophtheirus salmonis) can make them return to freshwater (FW). The aim of the present study was to map if and how reinfection with salmon louse and repeated FW exposure affects survival, growth rate, hepatosomatic index (HSI), acid base regulation (plasma pH, strong ion difference), osmoregulation (plasma ions, osmolality) and semen quality (fertilization rate, embryo/fry survival) in sea trout. Individually tagged sea trout (~100 g) were infected with louse copepodids in SW and then switched to FW at the louse pre-adult stage. Twelve days thereafter, FW was replaced with SW, and a second similar louse infection and salinity change were performed. Treatment groups were (i) uninfected control, and infected during the first (ii), second (iii) or both (iv) infection periods. The study ended after a final three-month follow-up in FW involving egg fertilization with sperm of previously infected and uninfected control mature male trout.Lice infection did not affect fish mortality or semen quality, but elevated HSI. In SW, lice-infected fish had lower specific growth rate in weight, higher plasma pH, Na+, Cl− and osmolality, and lower plasma strong ionic difference and Na+/Cl− ratio compared to uninfected fish. After 48 h in FW, lice-infected fish still had higher plasma pH, while plasma Na+, Cl− and osmolality were lower and plasma Na+/Cl− ratio higher in infected than uninfected fish. Louse reinfection did not affect any end points compared to single infection.The results demonstrate that salmon louse disturbs sea trout’s Cl− more than Na+ regulation, resulting in reduced hypo-osmotic and hyper-osmotic abilities in SW and FW, respectively. Further, a strong effect of lice on acid–base regulation is evident, shown by elevated plasma pH in both SW and FW.

In biological fluids the charge is dominated by strong ions with pH-independent complete dissociation. The requirement of electroneutrality in combination with the principle of mass conservation and rules of dissociation as understood from physical chemistry including auto-dissociation of water allows definite specification of charge in any water-based fluid with known composition. Herein, two important publications are revisited using charge-balance modeling. In the first case it is shown that knowing a fixed pH difference between two types of fibroblasts and knowing also the pH-dependent buffer-capacities in the two cells allows quantitative assessment of buffer concentrations and strong ion differences. In the second example it is shown that the difficult problem of finding by calculation or titration the titratable acidity in urine modeled as a phosphate solution with high ionic strength can be solved with just measuring urine SID and total phosphate concentration without knowing either the correct dissociation constant or pH in urine. It is suggested that charge-balance modeling based on basic physical chemistry may reveal non-trivial ontological details of the system under study.

BackgroundThiazide or thiazide-like diuretics associated hyponatremia (TAH) has a high prevalence in hospitalized patients. Patients might present either with hypovolemic hyponatremia due to volume loss as a diuretic effect of thiazide or with a thiazide-induced syndrome of inadequate antidiuresis-like hyponatremia in need of fluid restriction. Sodium-based urine indices are usually not able to differentiate these two, being directly influenced by thiazide itself. Current guidelines suggest the use of clinical hydration status assessment in patients with TAH, but this approach has a poor diagnostic performance. In a retrospective analysis, we found apparent strong ion difference (aSID) as well as chloride and potassium levels in urine (ChU) to be helpful in the differential diagnosis of TAH.MethodsThis is a randomized (1:1 ratio) controlled, superiority, parallel-group single-center trial. In total, 136 participants with TAH < 130 mmol/l will be enrolled and randomly assigned to undergo either aSID/ChU-guided therapy of TAH or standard of care during hospitalization. At baseline, hydration status will be assessed by history/clinical examination and ultrasound. The primary outcome is the percentage of patients with an increase in serum sodium level > 4 mmol/l at day 1 or > 134 mmol/l in a maximum of 3 days in the aSID/ChU guided therapy group as compared to the standard care group.DiscussionThis study will prospectively investigate whether the implementation of 2 new diagnostic indices (aSID and, if inconclusive, ChU) allows for a correct treatment of TAH. As a secondary outcome, the performance of clinical and ultrasound-guided hydration status assessment will be investigated.Trial registrationClinicalTrials.gov, identifier: NCT06381934. Registered on 19 April 2024. www.kofam.ch, identifier: SNCTP 000005848/BASEC2024-00335.

Abstract Intravenous (IV) fluid resuscitation has been the cornerstone in the management of paediatric sepsis and shock since the last two centuries, yet evidence-based consensus continues to elude treatment guidelines. This narrative review chronicles the origin of IV fluids, documents the evidence leading to the formulation of the current consensus guidelines on IV fluid resuscitation in paediatric sepsis and shock and summarises guidelines for clinical practice. PubMed/Medline and Google Scholar were searched for relevant literature on the origin of IV fluids and its role in paediatric septic shock management. The current consensus guidelines for IV fluid therapy in paediatric sepsis and septic shock are based on low- to medium-GRADE evidence. In summary, fluid bolus therapy initiation in paediatric sepsis is recommended only if hypotension is present (regardless of setting), or with abnormal perfusion (only in high-income settings with intensive care facilities). Balanced crystalloids are the recommended first line for fluid bolus therapy, considering strong ion difference and osmolarity parameters. In high-income settings, fluid boluses of 10–20 ml/kg of ideal body weight up to 40–60 ml/kg over the 1st h of management in paediatric sepsis is recommended. Even smaller volume infusions, especially in low-income settings, is best guided by appropriate clinical laboratory and echocardiographic investigations. There is an urgent need to conduct large multicentric randomised controlled trials encompassing diverse settings with special focus on low-income settings to ascertain the need, choice, volume, duration and monitoring of IV fluid therapy in standard-of-care fluid resuscitation protocols for paediatric sepsis and septic shock management.

IntroductionFluid responsiveness is crucial concept in management of critically ill patients. Studies have shown that dyschloremia, serum chloride levels not within the limits of normal, has major impact on clinical outcomes in critical illnesses.ObjectivesTo assess the influence of Chloride guided fluid resuscitation on acidbase homeostasis in critically ill patients, by using Stewart approach.Materials and methodsThe study was conducted in ICU of Fortis Escorts Heart Institute, Okhla, Delhi. All Adult patients admitted in ICU, were assessed within 24 hours for fluid responsiveness and thereby fluid resuscitation was done using Stewart approach of ABG, based on chloride level in ABG. Normal chloride level in ABG was considered in the range of 97–107 mmol/L. Values less than range indicated Metabolic alkalosis and values higher than 107 mmol/L indicated non anion gap metabolic acidosis by Stewart Approach. Fluid responsiveness will also be confirmed with the dynamic measures of ultrasound. Exclusion criteria are–Acetazolamide useAddisons diseaseRenal tubular AcidosisIlliostomies, fistulaeUreteral diversionPancreaticoduodenal fistulaResultsWe found significant correlation between Chloride levels in ABG and fluid responsiveness of all critically ill patients admitted in ICU within 24 hours.Discussions/ConclusionsChloride is the major strong anion in blood, accounting for approximately one-third of plasma tonicity, for 97 to 98% of all strong anionic charges and for two-thirds of all negative charges in plasma.1 over the years, chloride has become the forgotten ion. With progress in our understanding of acid-base and chloride channel physiology, the chloride ion is regaining its prominence.2 Within the Stewart approach, chloride is the dominant negative strong ion in plasma and a key contributor to the strong ion difference (SID), one of three independent variables that determine the hydrogen ion concentration. Hyperchloraemia is quite commonly encountered in intensive care unit (ICU) patients3 and plays an important role in the pathogenesis of metabolic acidosis. Data from various observational investigation demonstrate that temporary hyperchloremia may even occur in 75% of ICU patients during the first 24 h of ICU stay. However, despite a rather high prevalence in critically ill patients, few outcome-related data regarding systemic chloride levels exist. This study aims to provide an overview on chloride physiology and to reflect chloride guided fluid resuscitation for better outcome of critically ill patients.

Metabolic acidosis is a common acid-base disorder in critically ill dogs, with fluid therapy being a key but debated treatment. Sodium bicarbonate's risks have spurred interest in safer alternatives such as sodium lactate. To compare the efficacy of a chloride-free, high strong ion difference solution (H-SID) to Ringer's lactate (RL) for treating metabolic acidosis, hypothesizing the superiority of the H-SID solution. Forty-six dogs with metabolic acidosis from two veterinary hospitals. Prospective randomized multicenter study. Dogs were randomly assigned to receive either RL or H-SID at infusion rates of 4 or 10 mL/kg/h for 4 h, based on their volume status. H-SID was compounded with sodium (145 mmol/L), lactate (145 mmol/L), potassium (10 mmol/L), and aspartate (10 mmol/L) in sterile water for injection. The H-SID group showed a significant increase in BE-ecf (mmol/L) at infusion rates of 4 mL/kg/h (p < 0.001) and 10 mL/kg/h (p < 0.001) when compared to the RL group. At the lower infusion rate, the median increase was 4.1 mmol/L (95% CI: 3.37, 6.71), whereas the RL group exhibited a variation of -0.1 (95% CI: -0.75, 2.2). At the higher infusion rate, the median increase was 11 mmol/L (95% CI: 8.16, 12.52) compared to the RL group variation of 1.3 (95% CI: 0.01, 2.96). Our results indicate a significant alkalizing effect of the H-SID solution in dogs with non-lactic metabolic acidosis, demonstrating a superior effect compared to the RL solution without notable adverse effects.

This review focuses on managing dairy animals during the transition period using the dietary cation-anion difference (DCAD) concept. Transition period is described as the period from 3 weeks before and 3 weeks after parturition. Dietary Cation-Anion Difference (DCAD) is a concept based on the strong ion difference theory, which is important for the maintenance of desirable acid-base status and is placed 3rd in homeostatic priorities. The authors have compiled and evaluated research on both dairy cattle and buffalo, examining the effects of DCAD on nutrient utilization, milk yield, milk composition, blood metabolites, urine pH, hypocalcaemia, ketosis, negative energy balance, and overall health. The findings indicate that DCAD is an effective management strategy for the transition period in dairy animals. Based on research conducted on cattle and buffalo species, author recommend -100 and +200 mEq/kg of DM, in prepartum and postpartum stage, respectively for better efficiency of milk production and the lowest cases of hypocalcemia and ketosis. However, while extensive research has been conducted on dairy cattle, there is a notable gap in knowledge regarding buffaloes. Therefore, more research on this species is necessary.

BackgroundThis in-vitro and in-vivo study investigates the Gibbs-Donnan effect across the filter during continuous veno-venous hemofiltration (CVVH). In particular, we assessed its acid–base implications, applying the physical–chemical approach.MethodsA prospective, single-center study was conducted using the PrismaMax machine (Baxter). Two sets of in-vitro CVVH experiments (with and without albumin) were performed to quantify the Gibbs-Donnan effect. Electrolytes, glucose, and osmolarity changes were measured across the filter and in the ultrafiltrate. Strong ion difference and sieving coefficients of the main solutes were calculated. Similar measurements were performed in oligo-anuric critically ill patients undergoing CVVH.ResultsIn-vitro experiments without albumin showed a sieving coefficient of 1 for both positive and negative ions. On the contrary, when albumin was added, the sieving coefficient for sodium and chloride changed linearly with albumin concentration (r = −0.94, p < 0.001 for sodium, r = 0.88, p < 0.001 for chloride), resulting in a progressive linear increase in post-filter strong ion difference (β = 1.1, r = 0.77, p = 0.003). In 22 studied patients, calculated albumin concentration increased across the filter (2.2 ± 0.5 g/dL vs. 3.1 ± 0.7 g/dL), leading to sodium retention (138 ± 6 vs. 141 ± 6 mmol/L, p < 0.001) and chloride excretion (100 ± 5 vs. 97 ± 5 mmol/L, p < 0.001), thus resulting in a higher post-filter strong ion difference (46 ± 4 vs. 40 ± 4 mmol/L, p < 0.001).ConclusionsThese in-vitro and in-vivo studies demonstrate that albumin linearly affects the sieving coefficient of ions, increasing the strong ion difference of plasma water during its passage through the filter and thus having a systemic alkalizing effect.Graphic abstract

Several studies have explored alternatives to enhance the performance, health, and safety of sports horses. One promising method involves the use of vibrating platforms (VP), which offer passive exercise stimulation via mechanical oscillations distributed throughout the body. This type of exercise is referred to as whole-body vibration (WBV) and is an emerging strategy for accelerating muscle recovery. This study examined the dynamics of proteins responsible for transporting monocarboxylates (MCT1 and MCT4), and their relationship with lactatemia and acid-base balance in connection with WBV recovery following intense treadmill exercise in horses. Eight crossbred horses underwent the standardized exercise test on the treadmill to determine the velocity corresponding to the lactate threshold. This velocity was used to prescribe the external load of the acute intense exercise bout (AIEB), which was performed to recruit rapidly fatigable type II muscle fibers and induce hyperlactatemia and metabolic acidosis. The horses were assigned to three experimental groups in a crossover design, with a 7-day washout period. The treadmill group (TG) actively recovered through low-intensity treadmill walking. The WBV group (WBVG) followed a stepwise recovery protocol on VP, with each step lasting 2 min and the frequencies decreasing in a specific order: 76, 66, 55, 46, and 32 Hz. The sham group (SG) was designated for horses with the VP turned off. All groups experienced a uniform recovery strategy duration of 10 min. Heart rate (HR), rectal temperature (RT), lactatemia, glycemia, acid-base status and electrolytes, strong ion difference (SID), and muscle monocarboxylate transporters (MCT1 and MCT4), were assessed. AIEB induced positive chronotropic effects, hyperlactatemia and moderate metabolic acidosis in all experimental groups. All groups also showed transitory hyperthermia, hyperglycemia, hypernatremia, hyperchloremia, hyperkalemia and SID reduction. HR was higher in TG than in the WBVG and SG immediately after the recovery procedures. Between the groups, there was no change in RT, lactatemia, glycemia and MCT1 and MCT4 content. Regardless of groups, the MCT4 content decreased 3 and 6 h after recovery strategies. It was concluded that a single whole-body vibration session did not enhance recovery of lactatemia or acid-base balance in horses after intense treadmill exercise.

Evaluation of Postoperative Acid-Base Balance and Lactate Levels as Predictors of ICU Length of Stay in Liver Transplant Patients.

Introduction Albumin substantially influences the acid-base equilibrium within the human body and the regulation of acid-base homeostasis. The precise role of albumin remains a subject of debate. Human plasma protein fraction 5% (PPF5%) (Octapharma Pharmazeutika Produktionsgesellschaft m.b.H., Vienna, Austria) contains selected plasma with approximately 88% normal human albumin. We hypothesize that the use of PPF5% in patients undergoing liver resection surgery will enhance tissue perfusion and augment the buffering capacity of blood. Methods A prospective, randomized controlled study spanning 18 months was conducted at Hamad General Hospital, Qatar, involving 48 patients scheduled for liver resection surgeries. Patients were allocated into two groups: group A received an intravenous infusion of PPF5%, while group R received an intravenous infusion of crystalloid (lactated Ringer's solution). Acid-base electrolyte fluctuations were evaluated on four occasions at different time intervals. Results There were significant alterations within each group at different time points. Group A exhibited a substantial variance in strong ion difference (SID) values compared to group R at the time after liver resection (TAR) and at the time of end of surgery (TE). Group A demonstrated significantly enhanced tissue perfusion at TAR and TE relative to group R. There was a noteworthy decrease in hemoglobin and hematocrit levels in group A compared to group R at TE due to the hemodilution effect of the PPF5%. Conclusions The use of PPF5% in significant quantities for rehydration during liver resection procedures appears safe, exhibiting no equivalent alterations in acid-base balance, electrolyte levels, and coagulation when compared to lactated Ringer's solution. Moreover, it demonstrates improved tissue perfusion alongside increased hemodilution.

IntroductionAfter the neonatal period Eimeriosis is one of the most common causes of large intestinal diarrhea in calves. In contrast to neonatal calves with diarrhea, there are very few reports about the clinicopathological alterations in affected animals, which are mainly based on experimental data. The aim of the present study was therefore to characterize acid–base and related clinicopathologic alterations in calves with Eimeria-associated diarrhea and to identify variables associated with in-hospital mortality.MethodsRetrospective analysis of clinical and clinicopathologic findings extracted from medical records of 118 calves aged 1 to 5 months admitted to a veterinary teaching hospital.ResultsSeverely affected calves were profoundly hyponatremic and hypochloremic, with a strong correlation between plasma sodium and chloride concentrations (Spearman’s rs = 0.90). Acidemia was found in 57.6% of calves and was associated with hyperphosphatemia, hyper-L-lactatemia, and the presence of unidentified strong ions. Forty-seven calves (39.8%) did not survive to hospital discharge. Classification tree analysis indicated that hospital mortality was associated with plasma ionized calcium concentrations <1.05 mmol/L, initial leukocyte counts >16 × 109 cells/L, and a poor or cachectic body condition. The resulting sensitivity and specificity for predicting non-survival of this model was 59.6 and 90.1%, respectively. In addition to plasma ionized calcium [Odds ratio (OR) = 0.011] and leukocyte concentrations (OR = 1.08), recumbency (OR = 6.1), albumin (OR = 0.90), and decreased strong ion difference (OR = 0.91) were associated with mortality in a second modeling approach (sensitivity 78.7%, specificity 71.8%).ConclusionCalves with Eimeria-associated diarrhea can develop profound clinicopathologic derangements. The identified prognostic factors suggest that advanced disease severity, indicated by an inability to stand and reduced body condition, is associated with a lower chance of survival.

BackgroundStewart’s acid–base theory states that, under isocapnic conditions, crystalloid infusion affects plasma pH due to changes in strong ion difference and total weak acid concentration: a comprehensive study also assessing renal response and hemodilution effects has not been conducted in humans. We aimed to evaluate Stewart’s approach during crystalloid infusion in humans.MethodsIn this randomized trial, patients undergoing surgery with minimal blood losses were randomized to receive to normal saline (chloride content 154 mEq/L, strong ion difference 0 mEq/L), lactated Ringer’s (chloride content 112 mEq/L, strong ion difference 29 mEq/L) or Crystalsol (chloride content 98 mEq/L, strong ion difference 50 mEq/L): patients received 10 ml/kg immediately after intubation, and 20 ml/kg after 2 h. Plasma/urinary acid–base and electrolytes were measured before study start and then at prespecified timepoints. The primary endpoint was pH one hour after the second fluid bolus: secondary outcomes included urinary/plasmatic electrolyte concentrations and strong ion difference during the study.ResultsForty-five patients were enrolled (15 in each group). The extent of hemodilution achieved with the first (median [Interquartile range]: saline 9% [6–15], Ringer’s 7% [4–9], Crystalsol 8% [5–12]) and the second fluid bolus (saline 13% [5–17], Ringer’s 12% [9–15], Crystalsol 15% [10–20]) was not different between groups (p = 0.39 and p = 0.19, respectively). Patients in saline group received more chloride (449 mEq [383–495]) vs. Ringer’s (358 mEq [297–419]) and Crystalsol groups (318 mEq [240–366]) (p = 0.001). One hour after the second bolus, pH was lower in saline group (7.34 [7.32–7.36]) vs. Ringer’s (7.40 [7.35–7.43) and Crystalsol groups (7.42 [7.38–7.44]) (both p < 0.01), since plasma chloride increased significantly over time in saline group but not in Ringer’s and Crystalsol groups. Overall chloride urinary excretion was not different between study groups (saline 36 mEq [28–64], Ringer’s 42 mEq [29–68], Crystalsol 44 mEq [27–56], p = 0.60) but, at the end of experiments, urinary chloride concentration was higher and diuresis was lower in saline group vs. Ringer’s and Crystalsol groups (p = 0.01, p = 0.04, respectively).ConclusionsConsistent with Stewart’s approach, crystalloid solutions with high chloride content lower pH due to reduced strong ion difference, progressive hemodilutional acidosis and limited renal response to chloride load.Trial RegistrationRegistered on clinicaltrials.gov (NCT03507062) on April, 24th 2018.

ABSTRACT: Oral rehydration in calves is traditionally performed by administering an oral electrolyte solution in which the electrolyte concentrate (EC) is diluted in water. Dilution of EC in milk has been used as an alternative method because it encourages voluntary water intake. Although practical, its effectiveness has not been proven consistently. This study compared the effectiveness of these two rehydration methods for correcting imbalances in diarrheal calves. Twenty-four newborn calves with induced osmotic diarrhea were divided into two treatment groups: MG with EC diluted in milk at meals and WG with EC diluted in water (5% body weight at 4 and 12 hours). All calves were fed with milk (4% body weight at 0, 8, and 16 hours) and had free access to water. Venous blood samples were collected at the times: -48 (before induction), -24, 0 (start of treatment), 8, 16, 24, and 48 hours.Packed cell volume (PCV), total plasma protein (TP), pH, pCO2, HCO3 -, BE, Na+, K+, Cl-, L-lactate, creatinine, strong ion difference (SID3), anion gap (AG), total concentration of non-volatile weak acids (Atot), and percentage change in plasma volume (%PV) were measured or calculated. Calves exhibited moderate dehydration, hyponatremia, and mild strong ion acidosis. Both rehydration methods were effective in correcting the imbalances. Plasma volume expansion was faster in the WG and voluntary water intake was higher in the MG. Results based on induced rather than natural diarrhea are the main limitation of the study. Owing to its practicality and effectiveness, dilution of EC in milk can be used to treat non-depressed diarrheal calves with mild to moderate imbalances.

BackgroundEfficient oxygen transport depends on hemoglobin (Hb) affinity for O2, which is modulated by factors like PCO2, as described by the Bohr effect. This in vitro study explored how varying PO2 and PCO2 influence hemoglobin oxygen saturation (HbO2) and plasma electrolyte concentrations in whole human blood.MethodsBlood from six healthy volunteers was equilibrated at 37°C with gas mixtures spanning PO2 and PCO2 ranges. A total of 346 samples were analyzed for blood gases, HbO2, and electrolytes. The HbO2 dissociation curve was modeled using a Gompertz function within a non-linear mixed-effects framework, while electrolyte dynamics were assessed via polynomial models.ResultsHbO2 saturation ranged from 1.4 to 99.6%. Increasing PCO2 shifted the dissociation curve rightward, steepening its slope and raising the inflection point—hallmarks of the Bohr effect—without affecting maximal HbO2. Electrolyte analysis revealed that chloride decreased with PCO2 and increased with HbO2, consistent with the erythrocyte chloride shift. Sodium increased with PCO2, and a significant interaction between HbO2 and PCO2 was observed. Strong ion difference (SID) decreased linearly with HbO2 and increased quadratically with PCO2, suggesting a compensatory role in CO2-induced acid-base changes.ConclusionThese findings, validated against external datasets, underscore the tight coupling between respiratory gas exchange and electrolyte homeostasis. The study provides novel insights into how CO2 modulates both oxygen delivery and plasma ionic composition, with implications for understanding acid-base physiology and its regulation in health and disease.

Fractional excretion of sodium and potassium and urinary strong ion difference in the evaluation of persistent AKI in sepsis

Neonatal calf diarrhea is a frequent disease of calves and may result in dehydration and metabolic acidosis. The disease causes mortality and reduces growth and future productivity. Early identification of disease improves calf outcomes and thus there is increasing interest in technological methods for detecting disease. Dehydration leads to the blood becoming more concentrated and this can be measured using serum osmolality. Research in humans has shown that saliva conductivity is correlated with serum osmolality. Saliva conductivity may therefore offer a non-invasive opportunity to assess hydration status in calves. Furthermore, as blood pH is a prognostic indicator and there is ion exchange in the salivary ducts, saliva pH may act as an indicator of metabolic acidosis. This observational study aimed to assess the relationship of saliva conductivity and pH with the clinical and biochemical parameters of calves suffering from neonatal calf diarrhea. One hundred and forty-one dairy-bred calves were recruited onto the study at approximately 1 week of age. The health of the calves was assessed daily. Calves had blood and saliva samples taken weekly until 25 days of age or the development of neonatal calf diarrhea. When calves developed diarrhea, they were sampled for three consecutive days. Hematocrit, plasma total protein, saliva pH and saliva conductivity were measured at each sampling. Saliva pH and saliva conductivity were measured using portable meters (LAQUAtwin-pH-33 and LAQUAtwin-EC22). In a subset of 30 matched samples, serum proteins and electrolytes were also measured. Saliva conductivity was not associated with diarrhea or dehydration. Saliva pH was lower in calves with diarrhea, regardless of hydration status. The Lin's concordance correlation coefficients between saliva variables and hematocrit and strong ion difference were negligible. Dehydrated calves with diarrhea had a higher hematocrit and albumin and the lowest sodium and SID. Calves with diarrhea and no dehydration had a lower plasma total protein. While saliva conductivity has been associated with measures of dehydration in humans, this does not appear to be the case in calves. Saliva pH has not previously been considered for disease detection; however as it is associated with diarrhea, further research is warranted.