Acetate- versus lactate-buffered crystalloid solutions: A systematic review with meta-analysis and trial sequential analysis

Objective

There is a widespread use of buffered crystalloid solutions in clinical practice. However, guidelines do not distinguish between specific types of buffered solutions and clinical equipoise exists. We aimed to assess the desirable and undesirable effects of acetate‐ versus lactate‐buffered solutions in hospitalised patients.

Methods

We conducted a systematic review with meta‐analysis and trial sequential analysis of randomised clinical trials assessing the use of acetate‐ versus lactate‐buffered solutions for intravenous administration in hospitalised adults and children. The primary outcome was all‐cause short‐term mortality. We adhered to our published protocol, the Preferred Reporting Items for Systematic Reviews and Meta‐analyses (PRISMA) statement, the Cochrane Handbook and the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) methodology.

Results

We included five RCTs enrolling 390 patients. We found no statistically significant difference in short‐term mortality (random effects, risk ratio [RR] 0.29; 95% confidence interval [CI] 0.06–1.51, p = .14, I² = 0%) or hospital length of stay (LOS) (random effects, mean difference [MD]—1.31, 95% CI −3.66 to 1.05, p = .28, I² = 0%) between acetate‐ versus lactate‐buffered solutions. The quality of evidence was very low. Data regarding intensive care unit LOS were reported by three trials and duration of vasopressor treatment by one trial; none of these data allowed for pooling in meta‐analyses. No trials reported data on long‐term mortality, health‐related quality of life, adverse events, duration of mechanical ventilation or renal replacement therapy.

Conclusion

In this systematic review, we found very low quantity and quality of evidence on the use of acetate‐ versus lactate‐buffered solutions in hospitalised patients.

Modeling acid-base balance during continuous kidney replacement therapy

Clinical studies have suggested that use of bicarbonate-containing substitution and dialysis fluids during continuous kidney replacement therapy may result in excessive increases in the carbon dioxide concentration of blood; however, the technical parameters governing such changes are unclear. The current work used a mathematical model of acid-base chemistry of blood to predict its composition within and exiting the extracorporeal circuit during continuous veno-venous hemofiltration (CVVH) and continuous veno-venous hemodiafiltration (CVVHDF). Model predictions showed that a total substitution fluid infusion rate of 2 L/h (33% predilution) with a bicarbonate concentration of 32 mEq/L during CVVH at a blood flow rate of 200 mL/min resulted in only modest increases in plasma bicarbonate concentration by 2.0 mEq/L and partial pressure of dissolved carbon dioxide by 4.4 mmHg in blood exiting the extracorporeal circuit. The relative increase in bicarbonate concentration (9.7%) was similar to that in partial pressure of dissolved carbon dioxide (8.2%), resulting in no significant change in plasma pH in the blood exiting the CVVH circuit. The changes in plasma acid-base levels were larger with a higher infusion rate of substitution fluid but smaller with a higher blood flow rate or use of substitution fluid with a lower bicarbonate concentration (22 mEq/L). Under comparable flow conditions and substitution fluid composition, model predicted changes in acid-base levels during CVVHDF were similar, but smaller, than those during CVVH. The described mathematical model can predict the effect of operating conditions on acid-base balance within and exiting the extracorporeal circuit during continuous kidney replacement therapy.

Chloride toxicity in critically ill patients: What's the evidence?

Crystalloids have become the fluid of choice in critically ill patients and in the operating room both for fluid resuscitation and fluid maintenance. Among crystalloids, NaCl 0.9% has been the most widely used fluid. However, emerging evidence suggests that administration of 0.9% saline could be harmful mainly through high chloride content and that the use of fluid with low chloride content may be preferable in major surgery and intensive care patients. Administration of NaCl 0.9% is the leading cause of metabolic hyperchloraemic acidosis in critically ill patients and side effects might target coagulation, renal function, and ultimately increase mortality. More balanced solutions therefore may be used especially when large amount of fluids are administered in high-risk patients. In this review, we discuss physiological background favouring the use of balanced solutions as well as the most recent clinical data regarding the use of crystalloid solutions in critically ill patients and patients undergoing major surgery.

Continuous Renal Replacement Therapy for the Management of Acid-Base and Electrolyte Imbalances in Acute Kidney Injury

Continuous renal replacement therapy (CRRT) is used to manage electrolyte and acid-base imbalances in critically ill patients with acute kidney injury. Although a standard solution and prescription is acceptable in most clinical circumstances, specific disorders may require a tailored approach such as adjusting fluid composition, regulating CRRT dose, and using separate intravenous infusions to mitigate and correct these disturbances. Errors in fluid prescription, compounding, or delivery can be rapidly fatal. This article provides an overview of the principles of acid-base and electrolyte management using CRRT.

Bicarbonate- versus lactate-buffered solutions for acute continuous haemodiafiltration or haemofiltration

BACKGROUND

Acute kidney injury (AKI) is a severe loss of kidney function that results in patients' inability to appropriately excrete nitrogenous wastes and creatinine. Continuous haemodiafiltration (HDF) or haemofiltration (HF) are commonly used renal replacement therapies for people with AKI. Buffered dialysates and solutions used in HDF or HF have varying effects on acid-base physiology and several electrolytes. The benefits and harms of bicarbonate- versus lactate-buffered HDF or HF solutions for treating patients with AKI remain unclear.

OBJECTIVES

To assess the benefits and harms of bicarbonate- versus lactate-buffered solutions for HDF or HF for treating people with AKI.

SEARCH METHODS

We searched the Cochrane Renal Group's Specialised Register to 6 January 2015 through contact with the Trials' Search Co-ordinator using search terms relevant to this review. We also searched the Chinese Biomedical Literature Database.

SELECTION CRITERIA

All randomised controlled trials (RCT) and quasi-RCTs that reported comparisons of bicarbonate-buffered solutions with lactate-buffered solutions for AKI were selected for inclusion irrespective of publication status or language.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed titles and abstracts, and where necessary the full text of studies, to determine which satisfied our inclusion criteria. Data were extracted by two authors who independently assessed studies for eligibility and quality using a standardised data extraction form. Methodological quality was assessed using the Cochrane risk of bias tool. Results were expressed as risk ratio (RR) or mean difference (MD) with 95% confidence intervals (CI).

MAIN RESULTS

We identified four studies (171 patients) that met our inclusion criteria. Overall, study quality was suboptimal. There were significant reporting omissions related to methodological issues and potential harms. Outcome measures were not defined or reported adequately. The studies were small and lacked follow-up phases.Serum lactate levels were significantly lower in patients treated with bicarbonate-buffered solutions (4 studies, 171 participants: MD -1.09 mmol/L, 95% CI -1.30 to -0.87; I(2) = 0%). There were no differences in mortality (3 studies, 163 participants: RR 0.76, 95% CI 0.50 to 1.15; I(2) = 0%); serum bicarbonate levels (3 studies, 163 participants: MD 0.27 mmol/L, 95% CI -1.45 to 1.99; I(2) = 78%), serum creatinine (2 studies, 137 participants: MD -22.81 µmol/L, 95% CI -129.61 to 83.99; I(2) = 73%), serum base excess (3 studies, 145 participants: MD 0.80, 95% CI -0.91 to 2.50; I(2) = 38%), serum pH (4 studies, 171 participants: MD 0.01, 95% CI -0.02 to 0.03; I(2) = 70%) or carbon dioxide partial pressure (3 studies, 151 participants: MD -1.04, 95% CI -3.84 to 1.76; I(2) = 83%). A single study reported fewer cardiovascular events (RR 0.39, 95% CI 0.20 to 0.79), higher mean arterial pressure (10.25 mm Hg, 95% CI 6.68 to 13.82) and less hypotensive events (RR 0.44, 95% CI 0.26 to 0.75) in patients receiving bicarbonate-buffered solutions. One study reported no significant difference in central venous pressure (MD 2.00 cm H2O, 95% CI -0.7 to, 4.77). Total length of hospital and ICU stay and relapse were not reported by any of the included studies.

AUTHORS' CONCLUSIONS

There were no significant different between bicarbonate- and lactate-buffered solutions for mortality, serum bicarbonate levels, serum creatinine, serum base excess, serum pH, carbon dioxide partial pressure, central venous pressure and serum electrolytes. Patients treated with bicarbonate-buffered solutions may experience fewer cardiovascular events, lower serum lactate levels, higher mean arterial pressure and less hypotensive events. With the exception of mortality, we were not able to assess the main primary outcomes of this review - length of time in ICU, total length of hospital stay and relapse.

Solutions for peritoneal dialysis in children: recommendations by the European Pediatric Dialysis Working Group

The purpose of this article is to provide recommendations on the choice of peritoneal dialysis (PD) fluids in children by the European Pediatric Dialysis Working Group. The literature on experimental and clinical studies with PD solutions in children and adults was analyzed together with consensus discussions within the group. A grading was performed based on the international KDIGO nomenclature and methods. The lowest glucose concentration possible should be used. Icodextrin may be applied once daily during the long dwell, in particular in children with insufficient ultrafiltration. Infants on PD are at risk of ultrafiltration-associated sodium depletion, while anuric adolescents may have water and salt overload. Hence, the sodium chloride balance needs to be closely monitored. In growing children, the calcium balance should be positive and dialysate calcium adapted according to individual needs. Limited clinical experience with amino acid-based PD fluids in children suggests good tolerability. The anabolic effect, however, is small; adequate enteral nutrition is preferred. CPD fluids with reduced glucose degradation products (GDP) content reduce local and systemic toxicity and should be preferred whenever possible. Correction of metabolic acidosis is superior with pH neutral bicarbonate-based fluids compared with single-chamber, acidic, lactate-based solutions. Prospective comparisons of low GDP solutions with different buffer compositions are still few, and firm recommendations cannot yet be given, except when hepatic lactate metabolism is severely compromised.

Safety of Regional Citrate Anticoagulation for Continuous Sustained Low Efficiency Dialysis (C-SLED) in Critically Ill Patients

BACKGROUND

Sustained low efficiency dialysis (SLED) is a hybrid therapy that uses a conventional hemodialysis machine to deliver lower solute clearance over prolonged periods of time, typically 8 to 12 hours per treatment, and utilizes the same sodium and bicarbonate concentrations as intermittent hemodialysis. The therapy has been shown to be an effective dialysis mode for the critically ill patient with acute renal failure and hemodynamic instability. At our institution, critically ill patients requiring renal replacement therapy receive SLED on a continuous, 24-hour schedule (C-SLED). The higher dialysis dose with C-SLED compared to continuous venovenous hemodiafiltration (CVVHDF) or traditional SLED would likely alter the prescription needed to provide regional citrate anticoagulation and the incidence of hypernatremia and metabolic alkalosis.

OBJECTIVE

To evaluate the safety of utilizing regional citrate anticoagulation with continuous SLED in critically ill patients who frequently clot the hemofilter and have contraindications to systemic anticoagulation with heparin. We hypothesized that the higher dialysis dose with C-SLED would affect the prescription of citrate anticoagulation and the development of hypernatremia and metabolic alkalosis.

DESIGN

We prospectively followed the first 20 patients who received regional citrate anticoagulation on C-SLED for acute renal failure in the intensive care unit. Important outcomes measured included serum sodium, bicarbonate, ionized calcium concentration, serum pH, and PCO2. The number of clotting episodes for each patient while on regional citrate anticoagulation was recorded. Setting. Surgical and medical intensive care units at The University of Texas MD Anderson Cancer Center.

RESULTS

In over 2200 hours of continuous dialysis with citrate anticoagulation none of the 20 patients had derangements in the serum sodium or acid base status requiring cessation of regional citrate anticoagulation. In 14 patients, no clotting occurred during 1500 hours of SLED with the citrate infusion. There were eight episodes of hemofilter clotting in six patients during 750 hours of C-SLED.

CONCLUSION

Regional citrate anticoagulation is a safe method of anticoagulation in critically ill patients on continuous SLED.

Metabolic effects of citrate- vs bicarbonate-based substitution fluid in continuous venovenous hemofiltration: a prospective sequential cohort study

BACKGROUND

Studies investigating the metabolic effects of citrate-based substitution fluids are lacking. This study aims to compare the effect of citrate- vs bicarbonate-based substitution fluid used during continuous venovenous hemofiltration (CVVH) for acute kidney injury on acid-base balance and electrolytes in critically ill patients.

METHODS

This was a prospective sequential cohort study in patients with a contraindication for systemic anticoagulation. The first cohort was treated by bicarbonate-based CVVH (n = 10) and the second cohort was treated by CVVH with citrate-based substitution fluid (n = 19). Flow of the latter was coupled to blood flow, and ionized calcium concentrations were monitored and kept constant by calcium-glubionate infusion.

RESULTS

No major differences between the 2 groups were found in baseline acid-base parameters. In both groups, arterial pH increased after initiation of treatment and normalized on the average within 18 hours in either group. No differences were found in bicarbonate concentrations. Electrolyte control was comparable for the groups.

CONCLUSION

Citrate-based substitution fluid is comparable to bicarbonate-based substitution fluid during CVVH in critically ill patients with acute kidney injury, concerning acid-base balance and electrolyte control. This implies complete conversion of citrate to bicarbonate in the patients studied.

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.

Acid-base disturbances in the intensive care unit: current issues and the use of continuous renal replacement therapy as a customized treatment tool

Continuous renal replacement therapies (CRRT) are often used to manage complex acid-base problems in critically ill patients. These techniques allow a constant manipulation of the plasma composition. Several technical factors from CRRT influence the acid-base status; namely, the effluent rate, the operational characteristics of the technique, the content of the solutions and the metabolic rate of the buffer. This article reviews the common acid base disorders occurring in the intensive care unit, using both the anion gap and the strong ion gap approaches, and describes the influence of CRRT on acid-base physiology. The use of CRRT as a customized therapy for acid-base disorders is discussed, allowing an integration of both physiological and technical concepts.

Impact of chloride balance in acidosis control: The Stewart approach in hemodialysis critically ill patients

BACKGROUND

Metabolic acidosis is highly prevalent in critically ill patients with acute renal failure. Little is known about the mechanisms by which renal replacement therapy intervenes in such cases. The objective of this study is to analyze the role of hemodialysis in acidosis correction in intensive care unit patients, with an emphasis on chloride levels in plasma and dialysate.

METHODS

We studied 19 intermittent hemodialysis procedures in 17 acidotic patients. The patients were grouped by procedure type (conventional or sustained low-efficiency dialysis) and by predialysis plasma chloride level (higher or lower than the dialysate chloride concentration). Immediately before and after each procedure, blood samples were collected for biochemical analysis. The Stewart method was used to calculate the strong ion difference and strong ion gap.

RESULTS

The patients presented acidosis related to hyperchloremia, hyperphosphatemia, and high unmeasured anions. Hypoalbuminemia had an alkalinizing effect. Hemodialysis corrected acidosis mainly by reducing phosphate and unmeasured anions. In the group as a whole, chloride levels did not change after dialysis. However, when analyzed according to predialysis plasma chloride, the high-chloride group presented a reduction in plasma chloride, resulting in better base excess improvement (Delta standard base excess) than in the low-chloride group. Among the determinants of acid-base status, the only factors correlating with Delta SBE were Delta strong ion gap and Delta chloride.

CONCLUSION

The serum chloride/dialysate chloride relationship during hemodialysis has an important impact on acidosis control.

Composition and clinical use of hemodialysates

A thorough knowledge and understanding of the principles underlying the preparation and the clinical application of hemodialysates can help us provide exemplary patient care to individuals having end-stage renal disease. It is prudent to be conversant with the following: (a) how each ingredient in a dialysate works, (b) the clinical circumstances under which the concentration of an ingredient can be altered, and (c) the special situations in which unconventional ingredients can be introduced into a dialysate. The potential to enrich dialysates with appropriate ingredients (such as iron compounds) is limited only by the boundaries of our imagination.

Transient reciprocal change of renal hepatocyte growth factor and transforming growth factor-beta1 may relate to renal hypertrophy in rats with liver injury or unilateral nephrectomy

We examined an animal model of liver injury using ligation of the common bile duct (CBD) in young rats to observe nephromegaly and to determine plasma and renal changes in hepatocyte growth factor (HGF) and transforming growth factor (TGF)-beta1. To examine the role of TGF-beta1 in the process of compensatory renal growth, renal tissue HGF, TGF-beta1, TGF-beta1 mRNA, and c-met protein were measured. Plasma HGF level decreased significantly at 1 wk, and plasma TGF-beta1 level also decreased at 1 wk and remained low at 2 wk after surgery in CBD ligation rats. Increased renal HGF/TGF-beta1 ratio was noted at 2 wk, followed by a higher kidney weight/body weight ratio and an elevated protein/DNA ratio at 3 wk after operation in CBD ligation rats. The increased renal HGF/TGF-beta1 ratio in CBD ligation rats was mainly attributed to elevated renal HGF levels. Renal HGF/TGF-beta1 ratio was also elevated at 12 h after unilateral nephrectomy. This elevated renal HGF/TGF-beta1 resulted exclusively from low renal TGF-beta1. Renal TGF-beta1 mRNA decreased significantly at 12-24 h after surgery in unilateral nephrectomized rats, whereas renal c-met receptor protein levels increased. Transient reciprocal change of HGF and TGF-beta1 manifesting as an increased renal HGF/TGF-beta1 ratio soon after uninephrectomy and later during CBD ligation suggests the probable role of TGF-beta1 in renal growth control and its possible initiating of renal hypertrophy in liver injury or unilateral nephrectomy.

Crystalloid strong ion difference determines metabolic acid–base change during acute normovolaemic haemodilution

OBJECTIVE

To study the acid-base effects of crystalloid strong ion difference (SID) during haemodilution.

DESIGN

Prospective in vivo study.

SETTING

University laboratory.

SUBJECTS

Anaesthetised, mechanically ventilated Sprague-Dawley rats.

INTERVENTIONS

Rats were studied in seven groups of three. Each group underwent normovolaemic haemodilution with one of seven crystalloids, with SID values from 0 to 40 mEq/l. Six exchanges of 9 ml crystalloid for 3 ml blood were performed.

MEASUREMENTS AND MAIN RESULTS

[Hb] fell from 142+/-17 to 44+/-10 g/l ( p<0.0001). Final plasma [lactate] was 1.1+/-0.6 mmol/l. Final standard base excess values ranged from -8 to +7 mmol/l, and were directly correlated with crystalloid SID (R(2)=0.91). By linear regression, the SID of a crystalloid balanced to maintain standard base excess=0 mmol/l was 23.7 mEq/l. Dilutions 2-5 produced similar results.

CONCLUSIONS

There is a linear relationship between crystalloid SID and post-dilutional metabolic acid-base status. The SID of a crystalloid balanced for normovolaemic haemodilution is 24 mEq/l. These principles are applicable in designing fluids for volume resuscitation, acute normovolaemic haemodilution and cardio-pulmonary bypass.

A novel regional citrate anticoagulation protocol for CRRT using only commercially available solutions

PURPOSE

To describe a citrate regional anticoagulation (CRA) protocol for patients with acute renal failure and contraindications to heparin who require continuous renal replacement therapy (CRRT), using only commercially available solutions, for units that do not want or cannot prepare extemporaneously made solutions.

MATERIALS AND METHODS

Case report and series from a medical/surgical intensive care unit of a university teaching hospital. A CRA protocol was developed by using only commercially available solutions. Five dialysis-specific clinical parameters were identified to allow simplified measurement and control.

RESULTS

There was a dramatic improvement of dialysis filter survival in the index patient that was seen in the subsequent patients receiving CRA. This was accompanied by excellent control of the clinical and biochemical parameters as well as nursing acceptance and ownership of the protocol.

CONCLUSION

It is possible to provide safe and effective CRA with only commercially available solutions. The protocol is applicable to most patients requiring CRRT.

Continuous renal replacement therapy: does technique influence electrolyte and bicarbonate control?

BACKGROUND AND OBJECTIVES

Different techniques of continuous renal replacement therapy (CRRT) might have different effects on electrolyte and acid-base control. The aim of this study was to determine whether continuous veno-venous hemodiafiltration (CVVHDF) or continuous veno-venous hemofiltration (CVVH) achieve better control of serum sodium, potassium and bicarbonate concentrations.

DESIGN

Retrospective controlled study.

SETTING

Two tertiary intensive care units.

PATIENTS

Critically ill patients with acute renal failure (ARF) treated with CVVHDF (n=49) or CVVH (n=50).

INTERVENTIONS

Retrieval of daily morning sodium and potassium values and arterial bicarbonate levels from computerized biochemical records before and after the initiation of CRRT for up to 2 weeks of treatment. Statistical comparison of findings.

MEASUREMENTS AND RESULTS

Before treatment, abnormal (high or low) values were frequently observed for sodium (65.1% for CVVHDF vs. 80.0% for CVVH; NS), potassium (45.9% vs. 34.0%; NS), and bicarbonate (73.3% vs. 68.0%; NS). After treatment, however, CVVHDF was more likely to achieve serum sodium concentrations within the normal range (74.1% vs. 62.9%; p=0.0026). Both treatments decreased the mean serum potassium concentration over the first 48 h (p=0.0059 and p<0.0001, respectively), but there was no difference in terms of the normalization of serum potassium concentration during the entire treatment period (88.3% vs. 90.5%; NS). Both treatments increased the mean arterial bicarbonate concentration over the first 48 hours (p=0.011 and p<0.0001, respectively). However, CVVH was associated with a lower incidence of metabolic acidosis (13.8% for CVVH vs. 34.5% for CVVHDF; p<0.0001) and a higher incidence of metabolic alkalosis (38.9% vs. 1.1%; p<0.0001) during the entire treatment period.

CONCLUSIONS

CRRT strategies based on different techniques have a significantly different impact on sodium and bicarbonate control.

Customized bicarbonate buffered dialysate and replacement solutions for continuous renal replacement therapies: effect of crystallization on the measured levels of electrolytes and buffer

The aim of this study was to investigate the impact of the addition of calcium to bicarbonate solutions for continuous renal replacement therapy (CRRT). We tested single bag (bicarbonate and calcium mixed 24 h before testing) and double bag solutions (mixed immediately before) with and without the addition of 4 mEq/L of acetate. Prescribed calcium varied from 0 to 5 mEq/L. All test solutions containing calcium showed crystallization at light microscopy. The double bag solutions decreased but did not prevent crystallization. The addition of acetate did not interfere with crystallization. Crystallization, as measured by the weight of the crystals after filtration of the solutions, showed a significant positive correlation with the calcium deficit (prescribed minus measured) and with partial pressure of carbon dioxide. The measured level of calcium was lower than expected and correlated with crystallization. Our results suggest that the use of bicarbonate solutions containing calcium as replacement fluids for CRRT is a potentially unsafe procedure.

The value of blood lactate measurements in ICU: an evaluation of the role in the management of patients on haemofiltration

In response to clinical demand some point-of-care analysers now provide blood lactate measurements, but recently concern has been expressed about the value and interpretation of these measurements. We undertook this study to evaluate blood lactate measurements in patients with acute renal failure undergoing haemofiltration (HF) with lactate replacement fluid. At baseline, 27 patients had base deficits of >5 mmol/l and 14 (52%) had blood lactates of >3.5 mmol/l. Lactate 'tolerance' was monitored by peak changes in these parameters during the procedure. There was a worsening of base deficit in only three of the patients in whom lactate rises exceeded 10 mmol/l with one survivor. Twelve patients with rises of blood lactate greater than 5 mmol/l improved their base deficit (+1 to +17) with eight (67%) survivors. Of the remaining 12 patients with improved base deficit (+2 to +20), 10 (83%) survived. Lactate tolerance was compromised in patients with co-incidental liver disease, those on inotropic support, and in patients with initial blood lactate measurements of >10 mmol/l and large base deficits. The data suggest that blood lactate and simultaneous acid-base response measurements during HF help to assign correct buffer replacement and should be performed on all patients.