Volume Management with Kidney Replacement Therapy in the Critically Ill Patient

While the administration of intravenous fluids remains an important treatment, the negative consequences of subsequent fluid overload have raised questions about when and how clinicians should pursue avenues of fluid removal. Decisions regarding fluid removal during critical illness are complex even for patients with preserved kidney function. This article seeks to apply general concepts of fluid management to the care of patients who also require KRT. Because optimal fluid management for any specific patient is likely to change over the course of critical illness, conceptual models using phases of care have been developed. In this review, we will examine the implications of one such model on the use of ultrafiltration during KRT for volume removal in distributive shock. This will also provide a useful lens to re-examine published data of KRT during critical illness. We will highlight recent prospective trials of KRT as well as recent retrospective studies examining ultrafiltration rate and mortality, review the results, and discuss applications and shortcomings of these studies. We also emphasize that current data and techniques suggest that optimal guidelines will not consist of recommendations for or against absolute fluid removal rates but will instead require the development of dynamic protocols involving frequent cycles of reassessment and adjustment of net fluid removal goals. If optimal fluid management is dynamic, then frequent assessment of fluid responsiveness, fluid toxicity, and tolerance of fluid removal will be needed. Innovations in our ability to assess these parameters may improve our management of ultrafiltration in the future.

Value of variation of end-tidal carbon dioxide for predicting fluid responsiveness during the passive leg raising test in patients with mechanical ventilation: a systematic review and meta-analysis

Background

The ability of end-tidal carbon dioxide (ΔEtCO2) for predicting fluid responsiveness has been extensively studied with conflicting results. This meta-analysis aimed to explore the value of ΔEtCO2 for predicting fluid responsiveness during the passive leg raising (PLR) test in patients with mechanical ventilation.

Methods

PubMed, Embase, and Cochrane Central Register of Controlled Trials were searched up to November 2021. The diagnostic odds ratio (DOR), sensitivity, and specificity were calculated. The summary receiver operating characteristic curve was estimated, and the area under the curve (AUROC) was calculated. Q test and I² statistics were used for study heterogeneity and publication bias was assessed by Deeks’ funnel plot asymmetry test. We performed meta-regression analysis for heterogeneity exploration and sensitivity analysis for the publication bias.

Results

Overall, six studies including 298 patients were included in this review, of whom 149 (50%) were fluid responsive. The cutoff values of ΔEtCO2 in four studies was 5%, one was 5.8% and the other one was an absolute increase 2 mmHg. Heterogeneity between studies was assessed with an overall Q = 4.098, I² = 51%, and P = 0.064. The pooled sensitivity and specificity for the overall population were 0.79 (95% CI 0.72–0.85) and 0.90 (95% CI 0.77–0.96), respectively. The DOR was 35 (95% CI 12–107). The pooled AUROC was 0.81 (95% CI 0.77–0.84). On meta-regression analysis, the number of patients was sources of heterogeneity. The sensitivity analysis showed that the pooled DOR ranged from 21 to 140 and the pooled AUC ranged from 0.92 to 0.96 when one study was omitted.

Conclusions

Though the limited number of studies included and study heterogeneity, our meta-analysis confirmed that the ΔEtCO2 performed moderately in predicting fluid responsiveness during the PLR test in patients with mechanical ventilation.

Use of 'tidal volume challenge' to improve the reliability of pulse pressure variation

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2017. Other selected articles can be found online at http://ccforum.com/series/annualupdate2017. Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901.

Duration of anuria predicts recovery of renal function after acute kidney injury requiring continuous renal replacement therapy

BACKGROUND/AIMS

Little is known regarding the incidence rate of and factors associated with developing chronic kidney disease after continuous renal replacement therapy (CRRT) in acute kidney injury (AKI) patients. We investigated renal outcomes and the factors associated with incomplete renal recovery in AKI patients who received CRRT.

METHODS

Between January 2011 and November 2013, 408 patients received CRRT in our intensive care unit. Of them, patients who had normal renal function before AKI and were discharged without maintenance renal replacement therapy (RRT) were included in this study. We examined the incidence of incomplete renal recovery with an estimated glomerular filtration rate < 60 mL/min/1.73 m(2) and factors that increased the risk of incomplete renal recovery after AKI.

RESULTS

In total, 56 AKI patients were discharged without further RRT and were followed for a mean of 8 months. Incomplete recovery of renal function was observed in 20 of the patients (35.7%). Multivariate analysis revealed old age and long duration of anuria as independent risk factors for incomplete renal recovery (odds ratio [OR], 1.231; 95% confidence interval [CI], 1.041 to 1.457; p = 0.015 and OR, 1.064; 95% CI, 1.001 to 1.131; p = 0.047, respectively). In a receiver operating characteristic curve analysis, a cut-off anuria duration of 24 hours could predict incomplete renal recovery after AKI with a sensitivity of 85.0% and a specificity of 66.7%.

CONCLUSIONS

The renal outcome of severe AKI requiring CRRT was poor even in patients without further RRT. Long-term monitoring of renal function is needed, especially in severe AKI patients who are old and have a long duration of anuria.

Accuracy of the pleth variability index to predict fluid responsiveness depends on the perfusion index

BACKGROUND

Respiratory variations in plethysmographic waveform amplitudes derived from pulse oximetry are believed to predict fluid responsiveness. The non-invasive pleth variability index (PVI) is a variable based on the calculation of changes in the perfusion index (PI). The aim of the following study was to examine whether the predictive power of PVI depends on different values of PI.

METHODS

Eighty-one patients undergoing elective coronary artery surgery were studied before operation: at baseline after induction of anaesthesia and during passive leg raising (PLR). Each patient was monitored with central venous pressure (CVP), the PiCCO monitor and the non-invasive Masimo monitoring system. Stroke volume index by transpulmonary thermodilution (SVI(TPTD)), pulse pressure variation (PPV), stroke volume variation (SVV) and systemic vascular resistance index (SVRI) were measured using the PiCCO monitoring system. PI and PVI were obtained by pulse oximetry.

RESULTS

Responders were defined to increase their SVI(TPTD) >15% after PLR. The highest area under the curve (AUC) was found for PPV (AUC: 0.83, P<0.0001) and SVV (AUC: 0.72, P=0.002), in contrast to PVI (AUC: 0.60, P=0.11) and CVP (AUC: 0.60, P=0.13). The accuracy of PVI to predict fluid responsiveness was improved on analysing patients with higher PI values. PI of about 4% (n=45) achieved statistical significance (AUC: 0.72, P=0.01).

CONCLUSION

The PVI was not able to predict fluid responsiveness with sufficient accuracy. In patients with higher perfusion states, the PVI improved its ability to predict haemodynamic changes, strongly suggesting a relevant influence of the PI on the PVI.

Fluid overload and acute kidney injury

Acute kidney injury is commonly encountered in critically ill patients, and is associated with worse outcomes. Fluid therapy is a key component in the management of these patients, often leading to fluid overload, especially in the setting of septic acute kidney injury. Emerging data overwhelmingly suggest that fluid overload in these patients may be associated with adverse outcomes. Management of such patients should include a strategy of early guided resuscitation, followed by careful assessment of fluid status, and early initiation of renal replacement therapy as soon as it is deemed safe, aiming for a neutral or negative fluid balance. This review will focus on the pathophysiological link between fluid overload and acute kidney injury, mechanisms of organ dysfunction in fluid overload, and strategies for management.

Pediatric renal supportive therapies: the changing face of pediatric renal replacement approaches

PURPOSE OF REVIEW

The term 'renal replacement therapy' has been employed for describing dialytic interventions for acute and chronic patients. The implications of this terminology do not correctly reflect the extent that we are able to address native renal function. Provision of correct terminology to describe dialytic therapies may provide insight and investigation into the 'nonreplaceable' aspects of renal function in the acute and chronic settings.

RECENT FINDINGS

The terms 'chronic kidney disease' and 'acute kidney injury' have replaced the terms chronic renal failure and acute renal failure, respectively. Changing terminology has improved definitions and clinical care in these patient groups. Improvements in dialytic therapies have not been paralleled by changes in our understanding of the native renal function components that are not replaced during dialysis.

SUMMARY

A paradigm shift in our understanding of replacement of renal function is necessary. The terminology of 'renal replacement therapy' should be supplanted by more appropriate terminology, 'renal supportive therapy'. The benefits of employing terminology that adequately reflects the extent to which we can offer supportive dialytic treatment to our acute and chronic patients may be realized as a significant stimulus for scientific investigation and clinical care improvements.

Fluid balance and acute kidney injury

Intravenous fluids are widely administered to patients who have, or are at risk of, acute kidney injury (AKI). However, deleterious consequences of overzealous fluid therapy are increasingly being recognized. Salt and water overload can predispose to organ dysfunction, impaired wound healing and nosocomial infection, particularly in patients with AKI, in whom fluid challenges are frequent and excretion is impaired. In this Review article, we discuss how interstitial edema can further delay renal recovery and why conservative fluid strategies are now being advocated. Applying these strategies in critical illness is challenging. Although volume resuscitation is needed to restore cardiac output, it often leads to tissue edema, thereby contributing to ongoing organ dysfunction. Conservative strategies of fluid management mandate a switch towards neutral balance and then negative balance once hemodynamic stabilization is achieved. In patients with AKI, this strategy might require renal replacement therapy to be given earlier than when more-liberal fluid management is used. However, hypovolemia and renal hypoperfusion can occur in patients with AKI if excessive fluid removal is pursued with diuretics or extracorporeal therapy. Thus, accurate assessment of fluid status and careful definition of targets are needed at all stages to improve clinical outcomes. A conservative strategy of fluid management was recently tested and found to be effective in a large, randomized, controlled trial in patients with acute lung injury. Similar randomized, controlled studies in patients with AKI now seem justified.

The prevention of acute kidney injury: an in-depth narrative review Part 1: volume resuscitation and avoidance of drug- and nephrotoxin-induced AKI

This narrative clinical review in two parts discusses the prevention of clinical acute kidney injury (AKI). The first part focuses on general prevention measures, including identification of individuals at high risk for AKI, and on the role of volume expansion and fluid therapy. The latter discusses the timing, the goals, the selection of the fluids and the haemodynamic management of the patient receiving parenteral fluids for the prevention of AKI. In addition, this part summarizes the interaction of intensivist-nephrologist in the ICU with attention to tight glycaemia control and the use of low doses of corticoids in the septic shock patients. Finally, the avoidance of drug- and nephrotoxin-induced AKI is discussed. The second part of this review will summarize the possible pharmacological interventions in the patient at risk.