Metabolic and hemodynamic effects of hypertonic solutions: sodium-lactate versus sodium chloride infusion in postoperative patients

Lactate infusion elevates cardiac output through increased heart rate and decreased vascular resistance: a randomised, blinded, crossover trial in a healthy porcine model

BACKGROUND

Lactate is traditionally recognized as a by-product of anaerobic metabolism. However, lactate is a preferred oxidative substrate for stressed myocardium. Exogenous lactate infusion increases cardiac output (CO). The exact mechanism underlying this mechanism has yet to be elucidated. The aim of this study was to investigate the cardiovascular mechanisms underlying the acute haemodynamic effects of exogenous lactate infusion in an experimental model of human-sized pigs.

METHODS

In this randomised, blinded crossover study in eight 60-kg-pigs, the pigs received infusions with one molar sodium lactate and a control infusion of tonicity matched hypertonic saline in random order. We measured CO and pulmonary pressures using a pulmonary artery catheter. A pressure-volume admittance catheter in the left ventricle was used to measure contractility, afterload, preload and work-related parameters.

RESULTS

Lactate infusion increased circulating lactate levels by 9.9 mmol/L (95% confidence interval (CI) 9.1 to 11.0) and CO by 2.0 L/min (95% CI 1.2 to 2.7). Afterload decreased as arterial elastance fell by  -1.0 mmHg/ml (95% CI  -2.0 to  -0.1) and systemic vascular resistance decreased by  -548 dynes/s/cm5 (95% CI  -261 to  -835). Mixed venous saturation increased by 11 percentage points (95% CI 6 to 16), whereas ejection fraction increased by 16.0 percentage points (95% CI 1.1 to 32.0) and heart rate by 21 bpm (95% CI 8 to 33). No significant changes in contractility nor preload were observed.

CONCLUSION

Lactate infusion increased cardiac output by increasing heart rate and lowering afterload. No differences were observed in left ventricular contractility or preload. Lactate holds potential as a treatment in situations with lowered CO and should be investigated in future clinical studies.

Efficient Nitric Oxide Scavenging by Urea-Functionalized Push-Pull Chromophore Modulates NO-Mediated Diseases

The excess nitric oxide (NO) produced in the body in response to bacterial/proinflammatory stimuli is responsible for several pathological conditions. The current approaches that target the production of excess NO, either through the inhibition of nitric oxide synthase enzyme or its downstream mediators have been clinically unsuccessful. With an aim to regulate the excess NO, urea-functionalized push-pull chromophores containing 1,1,4,4-tetracyanobuta-1,3-dienes (TCBD) or expanded TCBD (eTCBD) were developed as NO scavengers. The NMR mechanistic studies revealed that upon NO binding, these molecules are converted to uncommon stable NONOates. The unique emissive property of Urea-eTCBD enables its application in vitro, as a NO-sensor. Furthermore, the cytocompatible Urea-eTCBD, rapidly inactivated the NO released from LPS-activated cells. The therapeutic efficacy of the molecule in modulating NO-mediated pathological condition was confirmed using a carrageenan-induced inflammatory paw model and a corneal injury model. While the results confirm the advantages of scavenging the excess NO to address a multitude of NO-mediated diseases, the promising sensing and bioactivity of Urea-eTCBD can motivate further exploration of such molecules in allied areas of research.

Lactate infusion as therapeutical intervention: a scoping review

Traditionally, clinicians consider lactate as a waste product of anaerobic glycolysis. Interestingly, research has shown that lactate may serve as an alternative fuel for the brain to protect it against harm. The increasing scientific awareness of the potential beneficial side of lactate, however, is entering the clinic rather slowly. Following this, and realizing that the application of potential novel therapeutic strategies in pediatric populations often lags behind the development in adults, this review summarizes the key data on therapeutic use of intravenous infusion of sodium lactate in humans. PubMed and clinicaltrial.gov were searched up until November 2021 focusing on interventional studies in humans. Thirty-four articles were included in this review, with protocols of lactate infusion in adults with diabetes mellitus, traumatic brain injury, Alzheimer's disease, and cardiac disease. One study on lactate infusion in children was also included. Results of our literature search show that sodium lactate can be safely administrated, without major side effects. Additionally, the present literature clearly shows the potential benefits of therapeutic lactate infusion under certain pathological circumstances, including rather common clinical conditions like traumatic brain injury.

CONCLUSION

This review shows that lactate is a save, alternative energy source for the adult brain warranting studies on the potential therapeutic effects of sodium lactate infusion in children.

WHAT IS KNOWN

• Lactate is generally considered a waste product of anaerobic glycolysis. However, lactate also is an alternative fuel for different organs, including the brain. • Lactate infusion is not incorporated in standard care for any patient population.

WHAT IS NEW

• Thirty-four studies investigated the therapeutic use of intravenous sodium lactate in different patient populations, all with different study protocols. • Literature shows that lactate infusion may have beneficial effects in case of hypoglycemia, traumatic brain injury, and cardiac failure without the risk of major side effects.

Effect of half-molar sodium lactate infusion on biochemical parameters in critically ill patients

OBJECTIVE

To evaluate the impact of the infusion of sodium lactate 500ml upon different biochemical variables and intracranial pressure in patients admitted to the intensive care unit.

DESIGN

A prospective experimental single cohort study was carried out.

SCOPE

Polyvalent intensive care unit of a university hospital.

PATIENTS

Critical patients with shock and intracranial hypertension.

PROCEDURE

A 500ml sodium lactate bolus was infused in 15min. Plasma levels of sodium, potassium, magnesium, calcium, chloride, lactate, bicarbonate, PaCO₂, pH, phosphate and albumin were recorded at 3 timepoints: T0 pre-infusion; T1 at 30min, and T2 at 60min post-infusion. Mean arterial pressure and intracranial pressure were measured at T0 and T2.

RESULTS

Forty-one patients received sodium lactate: 19 as an osmotically active agent and 22 as a volume expander. Metabolic alkalosis was observed: T0 vs. T1 (p=0.007); T1 vs. T2 (p=0.003). Sodium increased at the 3 timepoints (T0 vs. T1, p<0.0001; T1 vs. T2, p=0.0001). In addition, sodium lactate decreased intracranial pressure (T0: 24.83±5.4 vs. T2: 15.06±5.8; p<0.001). Likewise, plasma lactate showed a biphasic effect, with a rapid decrease at T2 (p<0.0001), including in those with previous hyperlactatemia (p=0.002).

CONCLUSIONS

The infusion of sodium lactate is associated to metabolic alkalosis, hypernatremia, reduced chloremia, and a biphasic change in plasma lactate levels. Moreover, a decrease in intracranial pressure was observed in patients with acute brain injury.

Lactic Acidosis and the Role of Sodium Bicarbonate: A Narrative Opinion

Lactic acidosis occurs commonly and can be a marker of significant physiologic derangements. However what an elevated lactate level and acidemia connotes and what should be done about it is subject to inconsistent interpretations. This review examines the varied etiologies of lactic acidosis, the physiologic consequences, and the known effects of its treatment with sodium bicarbonate. Lactic acidosis is often assumed to be a marker of hypoperfusion, but it can also result from medications, organ dysfunction, and sepsis even in the absence of malperfusion. Acidemia causes deleterious effects in almost every organ system, but it can also have positive effects, increasing localized blood flow and oxygen delivery, as well as providing protection against hypoxic cellular injury. The use of sodium bicarbonate to correct severe acidemia may be tempting to clinicians, but previous studies have failed to show improved patient outcomes following bicarbonate administration. Bicarbonate use is known to decrease vasomotor tone, decrease myocardial contractility, and induce intracellular acidosis. This suggests that mild to moderate acidemia does not require correction. Most recently, a randomized control trial found a survival benefit in a subgroup of critically ill patients with serum pH levels <7.2 with concomitant acute kidney injury. There is no known benefit of correcting serum pH levels ≥ 7.2, and sparse evidence supports bicarbonate use <7.2. If administered, bicarbonate is best given as a slow IV infusion in the setting of adequate ventilation and calcium replacement to mitigate its untoward effects.

Postoperative resuscitation with hypertonic saline or hyperoncotic albumin in patients following cardiac surgery: A review of the literature

BACKGROUND

Over-resuscitation in postcardiac surgery patients is associated with significant morbidity and mortality. Accordingly, there is a growing interest in hyperoncotic albumin and hypertonic saline for resuscitation in patients following cardiac surgery. In this article, we will review the use of hyperosmolar fluid therapies for resuscitation in postcardiac surgical patients from the current literature.

METHODS

A literature search was conducted in MEDLINE (PubMed) utilizing keywords, narrowing publications from 2009 to 2020.

RESULTS

Patients receiving concentrated albumin after cardiac surgery required less fluid bolus therapy, less time on vasopressors, and had a lower positive fluid balance compared with patients receiving crystalloids. There was no difference in mortality in those given 20% albumin compared with crystalloids postcardiac surgery. Patients administered hypertonic saline following cardiac surgery had increased urinary output but its effect on total fluid and body weight was not significantly different compared with crystalloids.

CONCLUSIONS

In this analysis, publications on resuscitation with hyperoncotic albumin and hypertonic saline in patients following cardiac surgery were reviewed. While there is data supporting the use of alternative fluid therapies in other critically ill populations, the limited literature focused on concentrated albumin and hypertonic saline for resuscitation following cardiac surgery is equivocal.

Effect of half-molar sodium lactate infusion on biochemical parameters in critically ill patients

OBJECTIVE

To evaluate the impact of the infusion of sodium lactate 500ml upon different biochemical variables and intracranial pressure in patients admitted to the intensive care unit.

DESIGN

A prospective experimental single cohort study was carried out.

SCOPE

Polyvalent intensive care unit of a university hospital.

PATIENTS

Critical patients with shock and intracranial hypertension.

PROCEDURE

A 500ml sodium lactate bolus was infused in 15min. Plasma levels of sodium, potassium, magnesium, calcium, chloride, lactate, bicarbonate, PaCO₂, pH, phosphate and albumin were recorded at 3timepoints: T0 pre-infusion; T1 at 30minutes, and T2 at 60minutes post-infusion. Mean arterial pressure and intracranial pressure were measured at T0 and T2.

RESULTS

Forty-one patients received sodium lactate: 19 as an osmotically active agent and 22 as a volume expander. Metabolic alkalosis was observed: T0 vs. T1 (P=0.007); T1 vs. T2 (P=0.003). Sodium increased at the 3time points (T0 vs. T1, P<0.0001; T1 vs. T2, P=0.0001). In addition, sodium lactate decreased intracranial pressure (T0: 24.83±5.4 vs. T2: 15.06±5.8; P<0.001). Likewise, plasma lactate showed a biphasic effect, with a rapid decrease at T2 (P<0.0001), including in those with previous hyperlactatemia (P=0.002).

CONCLUSIONS

The infusion of sodium lactate is associated to metabolic alkalosis, hypernatremia, reduced chloremia, and a biphasic change in plasma lactate levels. Moreover, a decrease in intracranial pressure was observed in patients with acute brain injury.

Role of Hypertonic Sodium Lactate in Traumatic Brain Injury Management

Traumatic brain injury (TBI) following increased intracranial pressure (ICP) is a neuroemergency case which should be managed promptly to prevent secondary brain injury. This will lead to a condition called cerebral energy dysfunction which is an important determinant factor toward worse outcome. Lactate, which was historically known as an end waste product, now is considered as an alternative cerebral energetic fuel. Hypertonic sodium lactate (HSL) is a promising hyperosmolar fluid which serves not only to decrease ICP but also to readily supply exogenous lactate to fulfill increased cerebral energy demand. Pioneer studies have shown the harmlessness and usefulness of HSL in treating pathological condition including TBI.

Hypertonic saline in critical illness - A systematic review

INTRODUCTION

The optimal approach to fluid management in critically ill patients is highly debated. Fluid resuscitation using hypertonic saline was used in the past for more than thirty years, but has recently disappeared from clinical practice. Here we provide an overview on the currently available literature on effects of hypertonic saline infusion for fluid resuscitation in the critically ill.

METHODS

Systematic analysis of reports of clinical trials comparing effects of hypertonic saline as resuscitation fluid to other available crystalloid solutions. A literature search of MEDLINE and the Cochrane Controlled Clinical trials register (CENTRAL) was conducted to identify suitable studies.

RESULTS

The applied search strategy produced 2284 potential publications. After eliminating doubles, 855 titles and abstracts were screened and 40 references retrieved for full text analysis. At total of 25 scientific studies meet the prespecified inclusion criteria for this study.

CONCLUSION

Fluid resuscitation using hypertonic saline results in volume expansion and less total infusion volume. This may be of interest in oedematous patients with intravascular volume depletion. When such strategies are employed, renal effects may differ markedly according to prior intravascular volume status. Hypertonic saline induced changes in serum osmolality and electrolytes return to baseline within a limited period in time. Sparse evidence indicates that resuscitation with hypertonic saline results in less perioperative complications, ICU days and mortality in selected patients. In conclusion, the use of hypertonic saline may have beneficial features in selected critically ill patients when carefully chosen. Further clinical studies assessing relevant clinical outcomes are warranted.

No influence of ischemic preconditioning on running economy

PURPOSE

Many of the potential performance-enhancing properties of ischemic preconditioning suggest that the oxygen cost for a given endurance exercise workload will be reduced, thereby improving the economy of locomotion. The aim of this study was to identify whether ischemic preconditioning improves exercise economy in recreational runners.

METHODS

A randomized sham-controlled crossover study was employed in which 18 adults (age 27 ± 7 years; BMI 24.6 ± 3 kg/m²) completed two, incremental submaximal (65-85% VO_2max) treadmill running protocols (3 × 5 min stages from 7.2-14.5 km/h) coupled with indirect calorimetry to assess running economy following ischemic preconditioning (3 × 5 min bilateral upper thigh ischemia) and sham control. Running economy was expressed as mlO₂/kg/km and as the energy in kilocalories required to cover 1 km of horizontal distance (kcal/kg/km).

RESULTS

Ischemic preconditioning did not influence steady-state heart rate, oxygen consumption, minute ventilation, respiratory exchange ratio, energy expenditure, and blood lactate. Likewise, running economy was similar (P = 0.647) between the sham (from 201.6 ± 17.7 to 204.0 ± 16.1 mlO₂/kg/km) and ischemic preconditioning trials (from 202.8 ± 16.2 to 203.1 ± 15.6 mlO₂/kg/km). There was no influence (P = 0.21) of ischemic preconditioning on running economy expressed as the caloric unit cost (from 0.96 ± 0.12 to 1.01 ± 0.11 kcal/kg/km) compared with sham (from 1.00 ± 0.10 to 1.00 ± 0.08 kcal/kg/km).

CONCLUSIONS

The properties of ischemic preconditioning thought to affect exercise performance at vigorous to severe exercise intensities, which generate more extensive physiological challenge, are ineffective at submaximal workloads and, therefore, do not change running economy.

Resuscitation fluids and hyperchloraemic metabolic acidosis

Until recently, saline and Hartmann’s solution were used almost interchangeably, while interest in colloids was mainly focused on the colloid component (gelatin, dextran or starch) rather than the carrier solution. Some clinicians are still not aware that almost all colloids are suspended in saline. There are no studies examining clinical outcomes after trauma or ICU resuscitation that compare saline-based fluids with ‘balanced’ fluids such as Hartmann’s solution. Recent evidence from volunteer and surgical studies suggest that the use of saline-based fluids (both the crystalloid saline and when used as a carrier solution for a colloid) can cause a hyperchloraemic metabolic acidosis. Although this may not be directly harmful, it may result in incorrect treatment of the acidosis such as more saline-based fluid. Increasing awareness of the ‘Stewart hypothesis’ has led to new ways of managing acid-base balance.

Hyperosmolar sodium-lactate in the ICU: vascular filling and cellular feeding

Hyperosmolar lactate-based solutions have been used for fluid resuscitation in ICU patients. The positive effects observed with these fluids have been attributed to both lactate metabolism and the hypertonic nature of the solutions. In a recent issue of Critical Care, Duburcq and colleagues studied three types of fluid infused at the same volume in a porcine model of endotoxic shock. The control group was resuscitated with 0.9% NaCl, and the two other groups received either hypertonic sodium-lactate or hypertonic sodium-bicarbonate. The two hypertonic fluids proved to be more effective than 0.9% NaCl for resuscitation in this model. However, some parameters were more effectively corrected by hypertonic sodium-lactate than by hypertonic sodium-bicarbonate, suggesting that lactate metabolism was beneficial in these cases.

Hypertonic sodium lactate improves fluid balance and hemodynamics in porcine endotoxic shock

Introduction

Based on the potential interest in sodium lactate as an energy substrate and resuscitative fluid, we investigated the effects of hypertonic sodium lactate in a porcine endotoxic shock.

Methods

Fifteen anesthetized, mechanically ventilated pigs were challenged with intravenous infusion of E. coli endotoxin. Three groups of five animals were randomly assigned to receive 5 mL/kg/h of different fluids: a treatment group received hypertonic sodium lactate 11.2% (HSL group); an isotonic control group receiving 0.9% NaCl (NC group); a hypertonic control group with the same amount of osmoles and sodium than HSL group receiving hypertonic sodium bicarbonate 8.4% (HSB group). Hemodynamic and oxygenation variables, urine output and fluid balance were measured at baseline and at 30, 60, 120, 210 and 300 min. Skin microvascular blood flow at rest and during reactive hyperemia was obtained using a laser Doppler flowmetry technique. Results were given as median with interquartile ranges.

Results

Endotoxin infusion resulted in hypodynamic shock. At 300 min, hemodynamics and oxygenation were significantly enhanced in HSL group: mean arterial pressure (103 [81–120] mmHg vs. 49 [41–62] in NC group vs. 71 [60–78] in HSB group), cardiac index (1.6 [1.2–1.8] L/min/m² vs. 0.9 [0.5–1.1] in NC group vs. 1.3 [0.9–1.6] in HSB group) and partial pressure of oxygen (366 [308–392] mmHg vs. 166 [130–206] in NC group vs. 277 [189–303] in HSB group). At the same time, microvascular reactivity was significantly better in HSL group with a lower venoarterial CO₂ tension difference (5.5 [4–10] mmHg vs. 17 [14–25] in NC group vs. 14 [12–15] in HSB group). The cumulative fluid balance was lower in HSL group (-325 [-655; -150] mL) compared to NC (+560 [+230; +900] mL, p = 0.008) and HSB (+185 [-110; +645] mL, p = 0.03) groups.

Conclusions

In our hypodynamic model of endotoxic shock, infusion of hypertonic sodium lactate improves hemodynamic and microvascular reactivity with a negative fluid balance and a better oxygenation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-014-0467-3) contains supplementary material, which is available to authorized users.

Sodium lactate for fluid resuscitation: the preferred solution for the coming decades?

In a recent issue of Critical Care, 0.5 M sodium lactate infusion for 24 hours was reported to increase cardiac output in patients with acute heart failure. This effect was associated with a concomitant metabolic alkalosis and a negative water balance. Growing data strongly support the role of lactate as a preferential oxidizable substrate to supply energy metabolism leading to improved organ function (heart and brain especially) in ischemic conditions. Due to its sodium/chloride imbalance, this solution prevents hyperchloremic acidosis and limits fluid overload despite the obligatory high sodium load. Sodium lactate solution therefore shows many advantages and appears a very promising means for resuscitation of critically ill patients. Further studies are needed to establish the most appropriate dose and indications for sodium lactate infusion in order to prevent the occurrence of severe hypernatremia and metabolic alkalosis.

Half-molar sodium lactate infusion improves cardiac performance in acute heart failure: a pilot randomised controlled clinical trial

Introduction

Acute heart failure (AHF) is characterized by inadequate cardiac output (CO), congestive symptoms, poor peripheral perfusion and end-organ dysfunction. Treatment often includes a combination of diuretics, oxygen, positive pressure ventilation, inotropes and vasodilators or vasopressors. Lactate is a marker of illness severity but is also an important metabolic substrate for the myocardium at rest and during stress. We tested the effects of half-molar sodium lactate infusion on cardiac performance in AHF.

Methods

We conducted a prospective, randomised, controlled, open-label, pilot clinical trial in 40 patients fulfilling two of the following three criteria for AHF: (1) left ventricular ejection fraction <40%, (2) acute pulmonary oedema or respiratory failure of predominantly cardiac origin requiring mechanical ventilation and (3) currently receiving vasopressor and/or inotropic support. Patients in the intervention group received a 3 ml/kg bolus of half-molar sodium lactate over the course of 15 minutes followed by 1 ml/kg/h continuous infusion for 24 hours. The control group received only a 3 ml/kg bolus of Hartmann’s solution without continuous infusion. The primary outcome was CO assessed by transthoracic echocardiography 24 hours after randomisation. Secondary outcomes included a measure of right ventricular systolic function (tricuspid annular plane systolic excursion (TAPSE)), acid-base balance, electrolyte and organ function parameters, along with length of stay and mortality.

Results

The infusion of half-molar sodium lactate increased (mean ± SD) CO from 4.05 ± 1.37 L/min to 5.49 ± 1.9 L/min (P < 0.01) and TAPSE from 14.7 ± 5.5 mm to 18.3 ± 7 mm (P = 0.02). Plasma sodium and pH increased (136 ± 4 to 146 ± 6 and 7.40 ± 0.06 to 7.53 ± 0.03, respectively; both P < 0.01), but potassium, chloride and phosphate levels decreased. There were no significant differences in the need for vasoactive therapy, respiratory support, renal or liver function tests, duration of ICU and hospital stay or 28- and 90-day mortality.

Conclusions

Infusion of half-molar sodium lactate improved cardiac performance and led to metabolic alkalosis in AHF patients without any detrimental effects on organ function.

Trial registration

Clinicaltrials.gov NCT01981655. Registered 13 August 2013.

Effect of hyperosmolar sodium lactate infusion on haemodynamic status and fluid balance compared with hydroxyethyl starch 6% during the cardiac surgery

Background and Aim:

No solution has been determined ideal for fluid therapy during cardiac surgery. Previous studies have shown that hyperosmolar sodium lactate (HSL) infusion has improved cardiac performance with smaller volume infusion, which resulted in negative fluid balance. This study compared the effects between a patent-protected HSL infusion and hydroxyethyl starch (HES) 6% on haemodynamic status of the patients undergoing cardiac surgery.

Methods:

In this open-label prospective controlled randomized study, patients were randomly assigned to receive loading dose of either HSL or HES 6%, at 3 mL/kgBW within 15 min, at the beginning of surgery. Haemodynamic parameters and fluid balance were evaluated, while biochemical parameters and any adverse effect were also recorded. Haemodynamic and laboratory parameters were analyzed through repeated measures analysis of variance. Statistical assessment of fluid management was carried out through Student t-test. All statistical analyses were performed using the statistical package for the social sciences^® version 15, 2006 (SPSS Inc., Chicago, IL).

Results:

Out of 100 enrolled patients in this study (50 patients in each arm), 98 patients were included in analysis (50 in HSL group; 48 in HES group). Cardiac index increased higher in HSL group (P = 0.01), whereas systemic vascular resistance index decreased more in HSL than HES group (P = 0.002). Other haemodynamic parameters were comparable between HSL and HES group. Fluid balance was negative in HSL group, but it was positive in HES group (−445.94 ± 815.30 mL vs. +108.479 ± 1219.91 mL, P < 0.009).

Conclusion:

Administration of HSL solution during the cardiac surgery improved cardiac performance and haemodynamic status better than HES did.

Rethinking Heart Failure

An increasing body of clinical observations and experimental evidence suggests that cardiac dysfunction results from autonomic dysregulation of the contractile output of the heart. Excessive activation of the sympathetic nervous system and a decrease in parasympathetic tone are associated with increased mortality. Elevated levels of circulating catecholamines closely correlate with the severity and poor prognosis in heart failure. Sympathetic over-stimulation causes increased levels of catecholamines, which induce excessive aerobic metabolism leading to excessive cardiac oxygen consumption. Resulting impaired mitochondrial function causes acidosis, which results in reduction in blood flow by impairment of contractility. To the extent that the excessive aerobic metabolism resulting from adrenergic stimulation comes to a halt the energy deficit has to be compensated for by anaerobic metabolism. Glucose and glycogen become the essential nutrients. Beta-adrenergic blockade is used successfully to decrease hyperadrenergic drive. Neurohumoral antagonists block adrenergic over-stimulation but do not provide the heart with fuel for compensatory anaerobic metabolism. The endogenous hormone ouabain reduces catecholamine levels in healthy volunteers, promotes the secretion of insulin, induces release of acetylcholine from synaptosomes and potentiates the stimulation of glucose metabolism by insulin and acetylcholine. Ouabain stimulates glycogen synthesis and increases lactate utilisation by the myocardium. Decades of clinical experience with ouabain confirm the cardioprotective effects of this endogenous hormone. The so far neglected sympatholytic and vagotonic effects of ouabain on myocardial metabolism clearly make a clinical re-evaluation of this endogenous hormone necessary. Clinical studies with ouabain that correspond to current standards are warranted.

The impact of increased blood lactate on serum S100B and prolactin concentrations in male adult athletes

S100B is an astroglial protein that is increased in the peripheral bloodstream after traumatic brain injury (TBI). Elevated serum levels of S100B have been shown to be predictive of mild TBI. Furthermore, physical activity (PA) can affect S100B levels. Interestingly, increased serum S100B concentrations have been detected in athletes without apparent TBI. Such increases could be attributed to tissue hypoperfusion reflected by blood lactate concentrations [BLa(-)] and/or increased serotonergic activity reflected by prolactin (PRL). The impact of increased blood lactates on peripheral S100B levels per se are yet unknown. The purpose of our study was to investigate if increased blood lactate induced by sodium lactate infusion, without the "side effects" of PA, resulted in changes in serum S100B and PRL. Twelve male adults were given a sodium lactate infusion for a period of 24 min by a perfusor with an infusion rate of 0.01 mL kg(-1) min(-1), increased every 3 min. The main outcome measures showed no increase in serum S100B (p > 0.05). Prolactin increased significantly (p < 0.05) after [BLa(-)] exceeded a concentration of 4 mmol L(-1). Furthermore, the expected values of blood lactate achieved peak values ranging from 11 to 15 mmol L(-1). We conclude that neither increased blood lactate nor serum PRL play an exclusive role in the regulation of S100B. Nevertheless, PA should be surveyed in medical history and critically assessed in determining the severity of TBI, especially in sports. Further studies are needed to clarify the impact of PA on the biomarker S100B.

Effects of endotoxin on lactate metabolism in humans

Introduction

Hyperlactatemia represents one prominent component of the metabolic response to sepsis. In critically ill patients, hyperlactatemia is related to the severity of the underlying condition. Both an increased production and a decreased utilization and clearance might be involved in this process, but their relative contribution remains unknown. The present study aimed at assessing systemic and muscle lactate production and systemic lactate clearance in healthy human volunteers, using intravenous endotoxin (LPS) challenge.

Methods

Fourteen healthy male volunteers were enrolled in 2 consecutive studies (n = 6 in trial 1 and n = 8 in trial 2). Each subject took part in one of two investigation days (LPS-day with endotoxin injection and placebo-day with saline injection) separated by one week at least and in a random order. In trial 1, their muscle lactate metabolism was monitored using microdialysis. In trial 2, their systemic lactate metabolism was monitored by means of a constant infusion of exogenous lactate. Energy metabolism was monitored by indirect calorimetry and glucose kinetics was measured with 6,6-H₂ glucose.

Results

In both trials, LPS increased energy expenditure (p = 0.011), lipid oxidation (p<0.0001), and plasma lactate concentration (p = 0.016). In trial 1, lactate concentration in the muscle microdialysate was higher than in blood, indicating lactate production by muscles. This was, however, similar with and without LPS. In trial 2, calculated systemic lactate production increased after LPS (p = 0.031), while lactate clearance remained unchanged.

Conclusions

LPS administration increases lactatemia by increasing lactate production rather than by decreasing lactate clearance. Muscle is, however, unlikely to be a major contributor to this increase in lactate production.

Trial registration

ClinicalTrials.gov NCT01647997

Lactate infusion at rest increases BDNF blood concentration in humans

Studies in humans use blood lactate to determine the degree of the exercise intensity, suggesting that exercise with elevated blood lactate concentrations results in increased BDNF plasma concentrations. However, it is not clear if lactate per se or rather other mechanisms are responsible for changes in blood BDNF concentrations. The lactate clamp method at rest is an appropriate method to examine physiological responses of lactate on the human organism without the effects of exercise. Eight male sport students placed in a sitting position received intravenous infusions with a 4 molar sodium-lactate solution in an incremental design starting with an infusion rate of 0.01ml/kgBW/min for the first three minutes, which was increased every three minutes by 0.01ml/kgBW/min up to 0.08ml/kg/min in the 24th minute. All together each subject received 4.2mmol of infusion. Venous blood samples were taken before and immediately after the infusion as well as in the 24th and the 60th min after the infusion period and analysed for BDNF. Blood gases and capillary blood lactate (La) were analysed before the test, every three minutes directly before increasing the infusion rate, at the end of the infusion and in the post infusions period until the 12th min and after 24 and 60min. BDNF and La increased significantly after the infusion and reached baseline values at the end of the experiment (p<0.05, p<0.01, respectively). pH and hydrogen ions increased from the beginning until the end of the infusion period (p<0.01). This data suggest that blood lactate is involved in the regulation of BDNF blood concentrations.

Treatment of lactic acidosis: appropriate confusion

BACKGROUND

Lactic acidosis (LA) is common in hospitalized patients and is associated with poor clinical outcomes. There have been major recent advances in our understanding of lactate generation and physiology. However, treatment of LA is an area of controversy and uncertainty, and the use of agents to raise pH is not clearly beneficial.

AIM AND METHODS

We reviewed animal and human studies on the pathogenesis, impact, and treatment of LA, published in the English language and available through the PubMed/MEDLINE database. Our aim was to clarify the physiology of the generation of LA, its impact on outcomes, and the different treatment modalities available. We also examined relevant data regarding LA induced by medications commonly prescribed by hospitalists: biguanides, nucleoside analog reverse-transcriptase inhibitors (NRTIs), linezolid, and lorazepam.

RESULTS/CONCLUSIONS

Lactic acid is a marker of tissue ischemia but it also may accumulate without tissue hypoperfusion. In the latter circumstance, lactic acid accumulation may be an adaptive mechanism-a novel possibility quite in contrast to the traditional view of lactic acid as only a marker of tissue ischemia. Studies on the treatment of LA with sodium bicarbonate or other buffers fail to show consistent clinical benefit. Severe acidemia in the setting of LA is a particularly poorly studied area. In the settings of medication-induced LA, optimal treatment, apart from prompt cessation of the offending agent, is still unclear.

Acid-base effects of a bicarbonate-balanced priming fluid during cardiopulmonary bypass: comparison with Plasma-Lyte 148. A randomised single-blinded study

Fluid-induced metabolic acidosis can be harmful and can complicate cardiopulmonary bypass. In an attempt to prevent this disturbance, we designed a bicarbonate-based crystalloid circuit prime balanced on physico-chemical principles with a strong ion difference of 24 mEq/l and compared its acid-base effects with those of Plasma-Lyte 148, a multiple electrolyte replacement solution containing acetate plus gluconate totalling 50 mEq/l. Twenty patients with normal acid-base status undergoing elective cardiac surgery were randomised 1:1 to a 2 litre prime of either bicarbonate-balanced fluid or Plasma-Lyte 148. With the trial fluid, metabolic acid-base status was normal following bypass initiation (standard base excess 0.1 (1.3) mEq/l, mean, SD), whereas Plasma-Lyte 148 produced a slight metabolic acidosis (standard base excess -2.2 (2.1) mEq/l). Estimated group difference after baseline adjustment was 3.6 mEq/l (95% confidence interval 2.1 to 5.1 mEq/l, P=0.0001). By late bypass, mean standard base excess in both groups was normal (0.8 (2.2) mEq/l vs. -0.8 (1.3) mEq/l, P=0.5). Strong ion gap values were unaltered with the trial fluid, but with Plasma-Lyte 148 increased significantly on bypass initiation (15.2 (2.5) mEq/l vs. 2.5 (1.5) mEq/l, P < 0.0001), remaining elevated in late bypass (8.4 (3.4) mEq/l vs. 5.8 (2.4) mEq/l, P < 0.05). We conclude that a bicarbonate-based crystalloid with a strong ion difference of 24 mEq/l is balanced for cardiopulmonary bypass in patients with normal acid-base status, whereas Plasma-Lyte 148 triggers a surge of unmeasured anions, persisting throughout bypass. These are likely to be gluconate and/or acetate. Whether surges of exogenous anions during bypass can be harmful requires further study.

Operating room use of hypertonic solutions: a clinical review

Hyperosmotic-hyperoncotic solutions have been widely used during prehospital care of trauma patients and have shown positive hemodynamic effects. Recently, there has been a growing interest in intra-operative use of hypertonic solutions. We reviewed 30 clinical studies on the use of hypertonic saline solutions during surgeries, with the majority being cardiac surgeries. Reduced positive fluid balance, increased cardiac index, and decreased systemic vascular resistance were the main beneficial effects of using hypertonic solutions in this population. Well-designed clinical trials are highly needed, particularly in aortic aneurysm repair surgeries, where hypertonic solutions have shown many beneficial effects. Examining the immunomodulatory effects of hypertonic solutions should also be a priority in future studies.

Sodium lactate versus mannitol in the treatment of intracranial hypertensive episodes in severe traumatic brain-injured patients

OBJECTIVES

Traumatic brain injury (TBI) is still a major cause of mortality and morbidity. Recent trials have failed to demonstrate a beneficial outcome from therapeutic treatments such as corticosteroids, hypothermia and hypertonic saline. We investigated the effect of a new hyperosmolar solution based on sodium lactate in controlling raised intracranial pressure (ICP).

DESIGN AND SETTING

Prospective open randomized study in an adult ICU.

PATIENTS

Thirty-four patients with isolated severe TBI (Glasgow Coma Scale <or= 8) and intracranial hypertension were allocated to receive equally hyperosmolar and isovolumic therapy, consisting of either mannitol or sodium lactate. Rescue therapy by crossover to the alternative treatment was indicated when ICP could not be controlled. The primary endpoint was efficacy in lowering ICP after 4 h, with a secondary endpoint of the percentage of successfully treated episodes of intracranial hypertension. The analysis was performed with both intention-to-treat and actual treatments provided.

MEASUREMENTS AND RESULTS

Compared to mannitol, the effect of the lactate solution on ICP was significantly more pronounced (7 vs. 4 mmHg, P = 0.016), more prolonged (fourth-hour-ICP decrease: -5.9 +/- 1 vs. -3.2 +/- 0.9 mmHg, P = 0.009) and more frequently successful (90.4 vs. 70.4%, P = 0.053).

CONCLUSION

Acute infusion of a sodium lactate-based hyperosmolar solution is effective in treating intracranial hypertension following traumatic brain injury. This effect is significantly more pronounced than that of an equivalent osmotic load of mannitol. Additionally, in this specific group of patients, long-term outcome was better in terms of GOS in those receiving as compared to mannitol. Larger trials are warranted to confirm our findings.

Lactate-buffered dialysis in cardiogenic shock associated with severe combined lactic acidosis

The level of lactate that would serve as cut-off for contraindication of lactate buffer is so far unclear. An acute exogenous load of lactate does not affect the basal endogenous lactate production and metabolism. It is also well metabolized in patients suffering from acute renal failure and severe sepsis with a compromised haemodynamic status. We report a case of extreme lactic acidosis in a patient admitted with a combination of cardiogenic shock, uraemia and suspected accumulation of biguanide. The patient was successfully treated with lactate-buffered dialysis due to the accidental absence of the bicarbonate-buffered fluids.

Cardio-cerebral and metabolic effects of methylene blue in hypertonic sodium lactate during experimental cardiopulmonary resuscitation

BACKGROUND

Methylene blue (MB) administered with a hypertonic-hyperoncotic solution reduces the myocardial and cerebral damage due to ischaemia and reperfusion injury after experimental cardiac arrest and also increases short-term survival. As MB precipitates in hypertonic sodium chloride, an alternative mixture of methylene blue in hypertonic sodium lactate (MBL) was developed and investigated during and after cardiopulmonary resuscitation (CPR).

METHODS

Using an experimental pig model of cardiac arrest (12 min cardiac arrest and 8 min CPR) the cardio-cerebral and metabolic effects of MBL (n=10), MB in normal saline (MBS; n=10) or in hypertonic saline dextran (MBHSD; n=10) were compared. Haemodynamic variables and cerebral cortical blood flow (CCBF) were recorded. Biochemical markers of cerebral oxidative injury (8-iso-PGF2alpha), inflammation (15-keto-dihydro-PGF2alpha), and neuronal damage (protein S-100beta) were measured in blood from the sagittal sinus, whereas markers of myocardial injury, electrolytes, and lactate were measured in arterial plasma.

RESULTS

There were no differences between groups in survival, or in biochemical markers of cerebral injury. In contrast, the MBS group exhibited not only increased CKMB (P<0.001) and troponin I in comparison with MBHSD (P=0.019) and MBL (P=0.037), but also greater pulmonary capillary wedge pressure 120 min after return of spontaneous circulation (ROSC). Lactate administration had an alkalinizing effect started 120 min after ROSC.

CONCLUSIONS

Methylene blue in hypertonic sodium lactate may be used against reperfusion injury during experimental cardiac arrest, having similar effects as MB with hypertonic saline-dextran, but in addition better myocardial protection than MB with normal saline. The neuroprotective effects did not differ.

Enhancement of cerebral blood flow using systemic hypertonic saline therapy improves outcome in patients with poor-grade spontaneous subarachnoid hemorrhage

OBJECT

Systemic administration of 23.5% hypertonic saline enhances cerebral blood flow (CBF) in patients with poor-grade spontaneous subarachnoid hemorrhage (SAH). Whether the increment of change in CBF correlates with changes in autoregulation of CBF or outcome at discharge remains unknown.

METHODS

Thirty-five patients with poor-grade spontaneous SAH received 2 ml/kg 23.5% hypertonic saline intravenously, and they underwent bedside transcranial Doppler (TCD) ultrasonography and intracranial pressure (ICP) monitoring. Seventeen of them underwent Xe-enhanced computed tomography (CT) scanning for measuring CBF. Outcome was assessed using the modified Rankin Scale (mRS) at discharge from the hospital. The data were analyzed using repeated-measurement analysis of variance and Dunnett correction. A comparison was made between patients with favorable and unfavorable outcomes using multivariate logistic regression.

RESULTS

The authors observed a maximum increase in blood pressure by 10.3% (p < 0.05) and cerebral perfusion pressure (CPP) by 21.2% (p < 0.01) at 30 minutes, followed by a maximum decrease in ICP by 93.1% (p < 0.01) at 60 minutes. Changes in ICP and CPP persisted for longer than 180 and 90 minutes, respectively. The results of TCD ultrasonography showed that the baseline autoregulation was impaired on the ipsilateral side of ruptured aneurysm, and increments in flow velocities were higher and lasted longer on the contralateral side (48.75% compared with 31.96% [p = 0.045] and 180 minutes compared with 90 minutes [p < 0.05], respectively). The autoregulation was briefly impaired on the contralateral side during the infusion. A dose-dependent effect of CBF increments on favorable outcome was seen on Xe-CT scans (mRS Score 1-3, odds ratio 1.27 per 1 ml/100 g tissue x min, p = 0.045).

CONCLUSIONS

Bolus systemic hypertonic saline therapy may be used for reversal of cerebral ischemia to normal perfusion in patients with poor-grade SAH.

Acid-base and bio-energetics during balanced versus unbalanced normovolaemic haemodilution

Fluids balanced to avoid acid-base disturbances may be preferable to saline, which causes metabolic acidosis in high volume. We evaluated acid-base and bio-energetic effects of haemodilution with a crystalloid balanced on physical chemical principles, versus crystalloids causing metabolic acidosis or metabolic alkalosis. Anaesthetised, mechanically ventilated Sprague-Dawley rats (n=32, allocated to four groups) underwent six exchanges of 9 ml crystalloid for 3 ml blood. Exchange was with one of three crystalloids with strong ion difference (SID) values of 0, 24 (balanced) and 40 mEq/l. Controls did not undergo haemodilution. Mean haemoglobin concentration fell to approximately 50 g/l after haemodilution. With SID 24 mEq/l fluid, metabolic acid-base remained unchanged. Dilution with SID 0 mEq/l and 40 mEq/l fluids caused a progressive metabolic acidosis and alkalosis respectively. Standard base excess (SBE) and haemoglobin concentration were directly correlated in the SID 0 mEq/l group (R2 = 0.61), indirectly correlated in the SBE 40 mEq/l group (R2 = 0.48) and showed no correlation in the SID 24 mEq/l group (R2 = 0.003). There were no significant differences between final ileal values of CO2 gap, nucleotides concentration, energy charge, or luminal lactate concentration. SID 40 mEq/l crystalloid dilution caused a significant rise in subcutaneous lactate. In this group mean kidney ATP concentration was significantly less than controls and renal energy charge significantly lower than SID 0 mEq/l and control groups. We conclude that a crystalloid SID of 24 mEq/l provides balanced haemodilution. Bio-energetic perturbations with higher SID haemodilution may be more severe and need further investigation.

Qu'apporte le modèle de Stewart à l'interprétation des troubles de l'équilibre acide–base?

OBJECTIVES

To explain the different approaches for interpreting acid-base disorders; to develop the Stewart model which offers some advantages for the pathophysiological understanding and the clinical interpretation of acid-base imbalances.

DATA SOURCE

Record of french and english references from Medline data base. The keywords were: acid-base balance, hyperchloremic acidosis, metabolic acidosis, strong ion difference, strong ion gap.

DATA EXTRACTION

Data were selected including prospective and retrospective studies, reviews, and case reports.

DATA SYNTHESIS

Acid-base disorders are commonly analysed by using the traditional Henderson-Hasselbalch approach which attributes the variations in plasma pH to the modifications in plasma bicarbonates or PaCO2. However, this approach seems to be inadequate because bicarbonates and PaCO2 are completely dependent. Moreover, it does not consider the role of weak acids such as albuminate, in the determination of plasma pH value. According to the Stewart concept, plasma pH results from the degree of plasma water dissociation which is determined by 3 independent variables: 1) strong ion difference (SID) which is the difference between all the strong plasma cations and anions; 2) quantity of plasma weak acids; 3) PaCO2. Thus, metabolic acid-base disorders are always induced by a variation in SID (decreased in acidosis) or in weak acids (increased in acidosis), whereas respiratory disorders remains the consequence of a change in PaCO2. These pathophysiological considerations are important to analyse complex acid-base imbalances in critically ill patients. For example, due to a decrease in weak acids, hypoalbuminemia increases SID which may counter-balance a decrease in pH and an elevated anion gap. Thus if using only traditional tools, hypoalbuminemia may mask a metabolic acidosis, because of a normal pH and a normal anion gap. In this case, the association of metabolic acidosis and alkalosis is only expressed by respectively a decreased SID and a decreased weak acids concentration. This concept allows to establish the relationship between hyperchloremic acidosis and infusion of solutes which contain large concentration of chloride such as NaCl 0.9%. Finally, the Stewart concept permits to understand that sodium bicarbonate as well as sodium lactate induces plasma alkalinization. In fact, sodium remains in plasma, whereas anion (lactate or bicarbonate) are metabolized leading to an increase in plasma SID.

CONCLUSION

Due to its simplicity, the traditional Henderson-Hasselbalch approach of acid-base disorders, remains commonly used. However, it gives an inadequate pathophysiological analysis which may conduct to a false diagnosis, especially with complex acid-base imbalances. Despite its apparent complexity, the Stewart concept permits to understand precisely the mechanisms of acid-base disorders. It has to become the most appropriate approach to analyse complex acid-base abnormalities.

Myocardial lactate deprivation is associated with decreased cardiovascular performance, decreased myocardial energetics, and early death in endotoxic shock

OBJECTIVE

We examined whether lactate availability is a limiting factor for heart function during endotoxic shock, and whether lactate deprivation thus induces heart energy depletion, thereby altering cardiovascular performance. The study goals were to determine whether muscle lactate production is linked to beta(2)-stimulation and to ascertain the effects of systemic lactate deprivation on hemodynamics, lactate metabolism, heart energetics, and outcome in a lethal model of rat's endotoxic shock.

INTERVENTIONS

We modulated the adrenergic pathway in skeletal muscle using microdialysis with ICI-118551, a selective beta(2)-blocker. Muscle lactate formation in endotoxic shock was further inhibited by intravenous infusion of ICI-118551 or dichloroacetate (DCA), an activator of pyruvate dehydrogenase (DCA) and their combination.

RESULTS

Muscle lactate formation was decreased by ICI-118551. During endotoxic shock both ICI-118151 and DCA decreased circulating and heart lactate concentrations in parallel with a decrease in tissue ATP content. The combination ICI-118551-DCA resulted in early cardiovascular collapse and death. The addition of molar lactate to ICI-1185111 plus DCA blunted the effects of ICI-118551+DCA on hemodynamics. Survival was markedly less with ICI-118551 than with endotoxin alone.

CONCLUSION

Systemic lactate deprivation is detrimental to myocardial energetics, cardiovascular performance, and outcome.

Lactate metabolism in acute uremia

Lactate is a key metabolite that is produced by every cell and oxidized by most of them, provided that they do contain mitochondria. Its metabolism is connected to energetic homeostasis and the cellular redox state. It is well recognized as an indicator of severe outcome in severely ill patients, however, it is not a detrimental factor per se. Conversely, some recent data tend even to indicate a beneficial effect in several metabolic disorders. Although the liver has long been recognized as a key organ in lactate homeostasis, the kidney also plays a major role as a gluconeogenic organ significantly involved in the glucose-lactate cycle. In acute renal failure, sodium lactate is widely used as a buffer in replacement fluids because the anion (lactate - ) is metabolized and the cation (Na + ) remains, leading to decreased water dissociation and proton concentration. The metabolic disorders related to acute renal failure or associated with it, such as liver failure, may affect lactate metabolism, and therefore they are often regarded as limiting factors for the use of lactate-containing fluids in such patients. By investigating endogenous lactate production in severe septic patients with acute renal failure, we found that an acute exogenous load of lactate did not affect the basal endogenous lactate production and metabolism. This indicates that exogenous lactate is well metabolized even in patients suffering from acute renal failure and severe sepsis with a compromised hemodynamic status.

Acid–base and electrolyte analysis in critically ill patients: are we ready for the new millennium?

PURPOSE OF REVIEW

Disorders of acid-base and electrolytes are commonly seen in critically ill patients. The presence of these disorders typically signals the development of an underlying pathology. These disturbances can be severe and are often associated with worse outcome. Indeed, metabolic acidosis is one of the ways we quantify organ failure. Although acid-base and electrolyte disorders may be a result of the underlying pathophysiology (eg, renal failure, respiratory failure, shock), they may also result from the way in which we manage critically ill patients.

RECENT FINDINGS

The application of the physical-chemical approach to acid-base analysis has led to recent developments in the identification and quantification and understanding of mechanisms for acid-base disorders commonly found in critically ill patients. Examples include a better understanding of the role of electrolytes (especially sodium and chloride) and weak acids in the pathophysiology of acid-base disorders, the implication of acid-base derangements on the inflammatory process and organ perfusion, and the importance of resuscitation fluid composition.

SUMMARY

By adopting a physical-chemical approach to acid-base analysis we are gaining insight to the complexities of acid-base disorders and how their treatments may affect outcome.

Lactate: A key metabolite in the intercellular metabolic interplay

Most physicians involved in intensive care consider lactate solely as a deleterious metabolite, responsible for high morbidity and bad prognosis in severe patients. For the physiologist, however, lactate is a key metabolite, alternatively produced or consumed. Many studies in the literature have infused animals or humans with exogenous lactate, demonstrating its safety and usefulness, but the bad reputation of lactate is still widespread. The metabolic meaning of glucose–lactate cycling exceeds its initial role described by Cori and Cori. According to recent works concerning lactate, it can be predicted that a new role as a therapeutic agent will arise for this metabolite.