Determinants of Urinary Output Response to IV Furosemide in Acute Kidney Injury: A Pharmacokinetic/Pharmacodynamic Study

How a positive fluid balance develops in acute kidney injury: A binational, observational study

PURPOSE

A positive fluid balance (FB) is associated with harm in intensive care unit (ICU) patients with acute kidney injury (AKI). We aimed to understand how a positive balance develops in such patients.

METHODS

Multinational, retrospective cohort study of critically ill patients with AKI not requiring renal replacement therapy.

RESULTS

AKI occurred at a median of two days after admission in 7894 (17.3%) patients. Cumulative FB became progressively positive, peaking on day three despite only 848 (10.7%) patients receiving fluid resuscitation in the ICU. In those three days, persistent crystalloid use (median:60.0 mL/h; IQR 28.9-89.2), nutritional intake (median:18.2 mL/h; IQR 0.0-45.9) and limited urine output (UO) (median:70.8 mL/h; IQR 49.0-96.7) contributed to a positive FB. Although UO increased each day, it failed to match input, with only 797 (10.1%) patients receiving diuretics in ICU. After adjustment, a positive FB four days after AKI diagnosis was associated with an increased risk of hospital mortality (OR 1.12;95% confidence intervals 1.05-1.19;p-value <0.001).

CONCLUSION

Among ICU patients with AKI, cumulative FB increased after diagnosis and was associated with an increased risk of mortality. Continued crystalloid administration, increased nutritional intake, limited UO, and minimal use of diuretics all contributed to positive FB.

KEY POINTS

Question How does a positive fluid balance develop in critically ill patients with acute kidney injury? Findings Cumulative FB increased after AKI diagnosis and was secondary to persistent crystalloid fluid administration, increasing nutritional fluid intake, and insufficient urine output. Despite the absence of resuscitation fluid and an increasing cumulative FB, there was persistently low diuretics use, ongoing crystalloid use, and a progressive escalation of nutritional fluid therapy. Meaning Current management results in fluid accumulation after diagnosis of AKI, as a result of ongoing crystalloid administration, increasing nutritional fluid, limited urine output and minimal diuretic use.

Sepsis-associated acute kidney injury: consensus report of the 28th Acute Disease Quality Initiative workgroup

Sepsis-associated acute kidney injury (SA-AKI) is common in critically ill patients and is strongly associated with adverse outcomes, including an increased risk of chronic kidney disease, cardiovascular events and death. The pathophysiology of SA-AKI remains elusive, although microcirculatory dysfunction, cellular metabolic reprogramming and dysregulated inflammatory responses have been implicated in preclinical studies. SA-AKI is best defined as the occurrence of AKI within 7 days of sepsis onset (diagnosed according to Kidney Disease Improving Global Outcome criteria and Sepsis 3 criteria, respectively). Improving outcomes in SA-AKI is challenging, as patients can present with either clinical or subclinical AKI. Early identification of patients at risk of AKI, or at risk of progressing to severe and/or persistent AKI, is crucial to the timely initiation of adequate supportive measures, including limiting further insults to the kidney. Accordingly, the discovery of biomarkers associated with AKI that can aid in early diagnosis is an area of intensive investigation. Additionally, high-quality evidence on best-practice care of patients with AKI, sepsis and SA-AKI has continued to accrue. Although specific therapeutic options are limited, several clinical trials have evaluated the use of care bundles and extracorporeal techniques as potential therapeutic approaches. Here we provide graded recommendations for managing SA-AKI and highlight priorities for future research.

Non-interventional follow-up versus fluid bolus in RESPONSE to oliguria in hemodynamically stable critically ill patients: a randomized controlled pilot trial

BACKGROUND

Fluid bolus therapy is a common intervention to improve urine output. Data concerning the effect of a fluid bolus on oliguria originate mainly from observational studies and remain controversial regarding the actual benefit of such therapy. We compared the effect of a follow-up approach without fluid bolus to a 500 mL fluid bolus on urine output in hemodynamically stable critically ill patients with oliguria at least for 2 h (urine output < 0.5 mL/kg/h) in randomized setting.

METHODS

We randomized 130 patients in 1:1 fashion to receive either (1) non-interventional follow-up (FU) for 2 h or (2) 500 mL crystalloid fluid bolus (FB) administered over 30 min. The primary outcome was the proportion of patients who doubled their urine output, defined as 2-h urine output post-randomization divided by urine output 2 h pre-randomization. The outcomes were adjusted for the stratification variables (presence of sepsis or AKI) using two-tailed regression. Obtained odds ratios were converted to risk ratios (RR) with 95% confidence intervals (CI). The between-group difference in the continuous variables was compared using mean or median regression and expressed with 95% CIs.

RESULTS

Altogether 10 (15.9%) of 63 patients in the FU group and 22 (32.8%) of 67 patients in FB group doubled their urine output during the 2-h period, RR (95% CI) 0.49 (0.23-0.71), P = 0.026. Median [IQR] change in individual urine output 2 h post-randomization compared to 2 h pre-randomization was - 7 [- 19 to 17] mL in the FU group and 19[0-53] mL in the FB group, median difference (95% CI) - 23 (- 36 to - 10) mL, P = 0.001. Median [IQR] duration of oliguria in the FU group was 4 [2-8] h and in the FB group 2 [0-6] h, median difference (95%CI) 2 (0-4) h, P = 0.038. Median [IQR] cumulative fluid balance on study day was lower in the FU group compared to FB group, 678 [518-1029] mL versus 1071 [822-1505] mL, respectively, median difference (95%CI) - 387 (- 635 to - 213) mL, P < 0.001.

CONCLUSIONS

Follow-up approach to oliguria compared to administering a fluid bolus of 500 mL crystalloid in oliguric patients improved urine output less frequently but lead to lower cumulative fluid balance. Trial registration clinical.

TRIALS

gov, NCT02860572. Registered 9 August 2016.

Diuretic strategies in patients with resistance to loop-diuretics in the intensive care unit: A retrospective study from the MIMIC-III database

PURPOSE

To investigate various diuretic strategies to alleviate loop-diuretics resistance in critically ill patients.

MATERIALS AND METHOD

ICU adults requiring more than 1 mg/kg/day of furosemide, from the MIMIC-III database. Four diuretic strategies were investigated: incremental dose of loop diuretics, continuous infusion, combinations with a second class of diuretics and administration of intravenous albumin. A generalized estimating equation was used to investigate the associations between these strategies and endpoints. The primary outcome was the 24-h urine output and secondary endpoints included fluid balance, weight change, electrolyte and acid-base abnormalities, kidney replacement therapy initiation, and mortality.

RESULTS

A total of 7645 ICU stays from 6358 patients were included. After adjustment, the use of continuous loop-diuretic infusion was associated with a higher 24-h urine output (β: 732, 95% CI:669-795, p < 0.001), lower 24-h fluid balance (p < 0.001) and greater weight loss at 48-h (p < 0.001). Thiazide- and carbonic anhydrase inhibitor combinations were both associated with higher urine output (p < 0.001) and weight loss at 48-h (p < 0.01), while intravenous albumin was associated with fluid gain (p < 0.001). Risks of electrolyte and metabolic disturbances varied across diuretic strategies.

CONCLUSIONS

Continuous loop-diuretic infusion and thiazide- or acetazolamide-loop diuretic combinations increased urine output significantly, leading to a negative fluid balance and weight loss.

The furosemide stress test, electrolyte response and Renal Index in critically ill patients

BACKGROUND

Acute kidney injury (AKI) is a common syndrome in critically ill patients. The diagnostic ability of traditional markers such as serum creatinine has recently been questioned, and the use of newer tests such as the furosemide stress test or the ultrasound assessment of renal resistive index have been proposed. Aim of the present study was to compare the response to a furosemide stress test, the Renal Index in mechanically ventilated patients with and without acute kidney injury at admission, and who did or did not develop AKI at day three, among those with normal renal function at the CIU admission.

METHODS

Prospective observational study in consecutive mechanically ventilated patients admitted in a general intensive care. Furosemide stress test and ultrasonographical Renal Index were performed at the admission and clinical and laboratory data were collected before and two hours after the furosemide stress text. The urine output after the first and the second hours was recorded.

RESULTS

Forty patients were enrolled, 19 of whom had AKI at admission. The Renal Index was significantly higher in patients with AKI (0.77±0.07 vs. 0.72±0.08, P=0.027); patients with AKI had a significantly lower urine output after the furosemide stress test (400 [340; 1400] vs.1525 [400; 2550] mL; P=0.013). The plasma concentrations of sodium, potassium and chloride were not different before and after the furosemide stress test in patients with and without AKI, whereas in patients with AKI, the total urine output of sodium, potassium and chloride were significantly lower compared to patients without AKI. Similar results were found in patients without AKI at admission and who developed AKI at day three as compared to those who did not develop AKI.

CONCLUSIONS

The response to the furosemide stress test and the Renal Index could be used as additional tools to evaluate the kidney function in critically ill patients.

Noninterventional follow-up vs fluid bolus in RESPONSE to oliguria-The RESPONSE trial protocol and statistical analysis plan

BACKGROUND

Oliguria is a frequent trigger for administering a fluid bolus, but the effect of fluid bolus in improving urine output is inadequately demonstrated. Here, we summarize the protocol and detailed statistical analysis plan of the randomized, controlled RESPONSE trial comparing follow-up as the experimental group and a 500 mL crystalloid fluid bolus as the control group for oliguria in critically ill oliguric patients.

METHODS

Our trial is an investigator-initiated, randomized, controlled, pilot trial conducted in three ICUs in two centers. We aim to randomize 1:1 altogether 130 hemodynamically stable oliguric patients either to a 2-hour follow-up without interventions or to receive a crystalloid bolus of 500 mL over 30 minutes. The primary outcome is the change in individual urine output during the 2-hour period compared to 2 hours preceding randomization. Doubling of the urine output is considered clinically significant. Additionally, we record the duration of oliguria, physiological and biochemical variables, adverse events, and the incidences of acute kidney injury and renal replacement therapy.

CONCLUSIONS

Oliguria is a frequent trigger for potentially harmful fluid loading. Therefore, the RESPONSE trial will give information of the potential effect of fluid bolus on oliguria in critically ill patients.

TRIAL REGISTRATION

clinical.trials.gov, NCT02860572.

A narrative review of pharmacologic de-resuscitation in the critically ill

Despite evidence highlighting harms of fluid overload, minimal guidance exists on counteraction via utilization of diuretics in the de-resuscitation phase. While diuretics have been shown to decrease net volume and improve clinical outcomes in the critically ill, a lack of standardization surrounding selection of diuretic regimen or monitoring of de-resuscitation exists. Current monitoring parameters of de-resuscitation often rely on clinical signs of fluid overload, end organ recovery and other biochemical surrogate markers which are often deemed unreliable. The majority of evidence suggests that achieving a net-negative fluid balance within 72 h after shock resolution may be of benefit; however, approaches to such goal are uncertain. Loop diuretics are a widely available type of diuretic for removal of volume in patients with sufficient kidney function, with the potential for adjunct diuretics in special circumstances. At present, administration of diuretics within the broad critically ill population fails to find uniformity and often efficacy. Given the lack of randomized controlled trials in this susceptible population, we aim to provide a thorough therapeutic understanding of diuretic pharmacotherapy which is necessary in order to achieve desired goal of fluid balance and improve overall outcomes.

Impact of furosemide on mortality and the requirement for renal replacement therapy in acute kidney injury: a systematic review and meta-analysis of randomised trials

OBJECTIVE

To examine the impact of furosemide on mortality and the need for renal replacement therapy (RRT) in adult patients with acute kidney injury (AKI) based on current evidence.

DATA SOURCES

PubMed (Medline) and Embase were searched from 1998 to October 2018.

STUDY SELECTION

We retrieved data from randomised controlled trials comparing prevention/treatment with furosemide at any stage of AKI with alternative treatment/standard of care/placebo. The outcome was short-term mortality and the requirement for RRT, when applicable.

DATA EXTRACTION

Two reviewers independently extracted appropriate data. PRISMA guidelines were followed for data preparation and reporting.

DATA SYNTHESIS

We identified 20 relevant studies (2608 patients: 1330 in the treatment arm and 1278 in the control arm). Heterogeneity between studies was deemed acceptable, and the publication bias was low. Furosemide had neither an impact on mortality (OR = 1.015; 95% CI 0.825-1.339) nor the need for RRT (OR = 0.947; 95% CI 0.521-1.721). Furosemide had also no effect on the outcomes in strata defined by intervention strategy (prevention/treatment), AKI origin (cardio-renal syndrome, post-cardiopulmonary bypass, critical illness), control arm comparator (RRT, saline/placebo/standard of care) and its dose (< 160/≥ 160 mg) (p > 0.05 for all). Subjects who received furosemide with matched hydration in prevention of contrast-induced nephropathy (CIN) had a less frequent need for RRT (OR = 0.218; 95% CI 0.05-1.04; p = 0.055).

CONCLUSIONS

Furosemide administration has neither an impact on mortality nor the requirement for RRT. Patients at risk of CIN may benefit from furosemide administration. Further well-designed RCTs are needed to verify these findings.

Patterns of diuretic use in the intensive care unit

Purpose

To inform future outcomes research on diuretics, we sought to describe modern patterns of diuretic use in the intensive care unit (ICU), including diuretic type, combination, and dosing. We also investigated two possible quality improvement targets: furosemide dosing in renal impairment and inclusion of an initial bolus with continuous furosemide infusions.

Materials and methods

In this descriptive study, we retrospectively studied 46,037 adult ICU admissions from a publicly available database of patients in an urban, academic medical center.

Results

Diuretics were employed in nearly half (49%, 22,569/46,037) of ICU admissions. Mechanical ventilation, a history of heart failure, and admission to the post-cardiac surgery unit were associated with a higher frequency of diuretic use. Combination use of different diuretic classes was uncommon. Patients with severely impaired kidney function were less likely to receive diuretics. Furosemide was by far the most common diuretic given and the initial intravenous dose was only 20 mg in more than half of ICU admissions. Among patients treated with a continuous infusion, 30% did not receive a bolus on the day of infusion initiation.

Conclusions

Patterns of diuretic use varied by patient-specific factors and by ICU type. Diuretic dosing strategies may be suboptimal.

Furosemide reverses medullary tissue hypoxia in ovine septic acute kidney injury

In experimental sepsis, the rapid development of renal medullary hypoxia precedes the development of acute kidney injury (AKI) and may contribute to its pathogenesis. We investigated whether inhibiting active sodium transport and oxygen consumption in the medullary thick ascending limb with furosemide attenuates the medullary hypoxia in experimental septic AKI. Sheep were instrumented with flow probes on the pulmonary and renal arteries and fiber optic probes to measure renal cortical and medullary perfusion and oxygen tension (Po₂). Sepsis and AKI were induced by infusion of live Escherichia coli. At 24 h of sepsis there were significant decreases in renal medullary tissue perfusion (1,332 ± 233 to 698 ± 159 blood perfusion units) and Po₂ (44 ± 6 to 19 ± 6 mmHg) (both P < 0.05). By 5 min after intravenous administration of furosemide (20 mg), renal medullary Po₂ increased to 43 ± 6 mmHg and remained at this normal level for 8 h. Furosemide caused transient increases in fractional excretion of sodium and creatinine clearance, but medullary perfusion, renal blood flow, and renal oxygen delivery were unchanged. Urinary F₂-isoprostanes, an index of oxidative stress, were not significantly changed at 24 h of sepsis but tended to transiently decrease after furosemide treatment. In septic AKI, furosemide rapidly restored medullary Po₂ to preseptic levels. This effect was not accompanied by changes in medullary perfusion or renal oxygen delivery but was accompanied by a transient increase in fractional sodium excretion, implying decreased oxygen consumption as a mechanism.

Furosemide as a functional marker of acute kidney injury in ICU patients: a new role for an old drug

New pharmacokinetics insight suggests that the furosemide pharmacology occurring in ICU patients with AKI is similar, but not equal to that described in chronic stable renal patients. Even if the diuretic response to furosemide is expressed by a steep dose-response curve positively correlated with renal function, pharmacodynamic limitations occur when creatinine clearance is < 20 ml/min or urine output is < 500 ml/12 h. In such cases, other factors specifically due to acute tubular injury can interfere with the furosemide-induced diuretic output. As modality of administration recent reports and metanalysis, even if not conclusive, suggest that for the same given dose a continuous infusion of furosemide was superior in diuretic response. For septic shock patients on CVVHDF where treatment adds an additional clearance of furosemide the maximum diuretic response is achieved by a continuous infusion of 20 mg/h of furosemide. At this infusion rate the reached plasma level was < 20 mg/L, a range considered safe and not ototoxic. Therefore, the severity of AKI establishes whether a patient will respond to furosemide. In this review we summarized all these recent updates, also suggesting that the diuretic response under continuous infusion may allow assessing glomerular and tubular functions with increased reliability than a bolus dose. However, validation studies are still needed to support continuous infusion as a stress test.

Urine volume as a predicting factor for furosemide clearance during continuous infusion in AKI septic shock patients on hemodiafiltration

BACKGROUND

This study assessed the contribution of intracorporeal (IC) and extracorporeal clearance (EC) of furosemide in patients with septic acute kidney injury (AKI), and the relationship between plasma concentrations and urine volume.

METHODS

Prospective cohort observational study of 15 patients with septic AKI undergoing continuous veno-venous hemodiafiltration (CVVHDF) divided according to urine volume (< 500 ml/12 h, Oliguria group, n = 5; > 500 ml/12 h, Diuresis group, n = 10) during continuous infusion of furosemide (120 mg/12 h) at steady-state condition. Plasma and effluent furosemide concentrations were determined by high-performance liquid chromatography (HPLC)-mass spectrometry every 12 h for 48 h.

RESULTS

Furosemide plasma concentrations and total body clearance (TBC) were 6.14 mg/l and 22.1 ml/min for the Oliguria group, and 2.63 mg/l and 54.4 ml/min for the Diuresis group, respectively (p < 0.05). When urine volume was < 500 ml/24 h, the furosemide plasma concentrations peaked at the potentially toxic value of 13.0 mg/l. Furosemide EC was not relevant for the Diuresis group, but it represented 18% of TBC for the Oliguria group. Furosemide plasma concentrations correlated positively with dose infusion for both groups (r = 0.728 and 0.685, p < 0.05), and negatively with urine volume only for the Diuresis (r = - 0.578, p < 0.01) but not for the Oliguria group (r = - 0.089, p = 0.715).

CONCLUSIONS

For patients with urine volume > 500 ml/12 h continuous infusion of furosemide up to 480 mg/24 h leads to increasing urine volume, which can predict furosemide plasma levels within its safety range. When the urine volume is lower, the furosemide plasma levels are increased beyond any further diuretic efficacy.

[New kidney function tests: Renal functional reserve and furosemide stress test]

Acute kidney injury (AKI) occurs in 30-50% of all intensive care patients. Renal replacement therapy (RRT) has to be initiated in 10-15%. The early in-hospital mortality is about 50%. Up to 20% of all survivors develop chronic kidney disease after intensive care discharge and progress to end-stage kidney disease within the next 10 years. For timely initiation of prophylactic or therapeutic interventions, it is crucial to exactly determine the actual kidney function, i. e., glomerular filtration rate (GFR), and to gain insight into the further development of kidney function. Traditionally, renal function has been estimated using serum levels of creatinine or urea. Unfortunately, both are notoriously unreliable and insensitive in intensive care patients. Cystatin C has fewer non-GFR determinants when compared to creatinine and is more sensitive and accurate to detect early decreases of GFR. At present, new functional tests are discussed, namely the furosemide stress test (FST) and renal functional reserve (RFR). The FST consists of an intravenous infusion of 1.0-1.5 mg/kgBW furosemide to critically ill patients with AKI. An increase in urine output to >100 ml/h is indicative of a GFR >20 ml/min and almost certainly excludes progression to AKI stage III and need for RRT. Estimation of RFR can be made by short-term oral or intravenous administration of a high protein load. A subsequent increase in GFR defines the presence and the magnitude of functional reserve which can be activated. Loss of RFR is an indicator of loss of functioning nephron mass and incomplete recovery following AKI. Both FST and RFR can help to improve diagnosis and care of high-risk patients with acute and chronic kidney disease.

Practical approach to detection and management of acute kidney injury in critically ill patient

Background

Acute kidney injury (AKI) is a common complication in critically ill patients and is associated with high morbidity and mortality. This paper provides a critical review of the etiologies of AKI and a systematic approach toward its diagnosis and management with emphasis on fluid volume assessment and the use of urine biochemical profile and microscopy in identifying the nature and the site of kidney injury.

Materials and methods

The search of PubMed and selection of papers had employed observational designs or randomized control trials relevant to AKI.

Results

AKI is defined by the rate of rise of serum creatinine and a decline in urine output. The pathophysiology is diverse and requires a careful and systematic assessment of predisposing factors and localization of site of injury. The majority of AKIs are due to prerenal causes such as fluid volume deficit, sepsis, or renal as in acute tubular injury. The use of central venous and arterial blood pressure monitoring and inferior vena cava echocardiography complemented by urine analysis and microscopy allows assessment of fluid volume status and AKI etiology.

Conclusions

Timely intervention by avoidance of fluid volume deficit and nephrotoxic agents and blood pressure support can reduce the incidence of AKI in critically ill patients.

The effect of low-dose furosemide in critically ill patients with early acute kidney injury: A pilot randomized blinded controlled trial (the SPARK study)

PURPOSE

Furosemide is commonly prescribed in acute kidney injury (AKI). Prior studies have found conflicting findings on whether furosemide modifies the course and outcome of AKI.

METHODS

Pilot multi-center randomized blinded placebo-controlled trial in adult patients with AKI admitted to three intensive care units. Participants were randomly allocated to furosemide bolus and infusion or 0.9% saline placebo. Primary endpoint was worsening AKI, defined by the RIFLE criteria. Secondary endpoints were kidney recovery, renal replacement therapy (RRT) and adverse events.

RESULTS

The trial was terminated after enrollment of 73 participants (37 to furosemide and 36 to placebo). Mean (SD) age was 61.7 (14.3), 79.5% were medical admissions, mean (SD) APACHE II score was 26.6 (7.8), 90.4% received mechanical ventilation and 61.6% received vasoactives. Groups were similar at baseline. No differences were found in the proportion with worsening AKI (43.2% vs. 37.1%, p=0.6), kidney recovery (29.7% vs. 42.9%, p=0.3), or RRT (27.0% s. 28.6%, p=0.8). Adverse events, mostly electrolyte abnormalities, were more common in furosemide-treated patients (p<0.001). Protocol deviations were common, due often to supplementary furosemide.

CONCLUSIONS

In this pilot trial, furosemide did not reduce the rate of worsening AKI, improve recovery or reduce RRT; however, was associated with greater electrolyte abnormalities.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT00978354 registered September 9, 2014.

Does Furosemide Increase Oxidative Stress in Acute Kidney Injury?

Furosemide, a loop diuretic, is used to increase urine output in patients with acute kidney injury (AKI). It remains uncertain whether the benefits of furosemide in AKI outweigh its potential harms. We investigated if furosemide influenced oxidative stress in 30 critically ill patients with AKI by measuring changes in F₂-isoprostanes (F₂-IsoPs), markers of in vivo oxidative stress, in plasma and urine following intravenous furosemide. Urine F₂-IsoPs were higher in sepsis (p = 0.001) and increased in proportion to urine furosemide (p = 0.001). The furosemide-induced increase in urine F₂-IsoPs differed depending on AKI severity (p < 0.001) and was greatest in those with the most severe AKI. Furosemide had no effect on plasma F₂-IsoPs. We demonstrate for the first time that furosemide increases renal oxidative stress in AKI and find that patients with the most severe AKI-to whom the largest doses are likely to be administered-showed the greatest increase in oxidative stress. These findings lead to the hypothesis that the common practice of administering high-dose furosemide to convert oliguric to nonoliguric AKI may induce harmful oxidative stress in the kidneys, and an adequately powered, randomized controlled trial is required to determine if clinical benefits of this dosing strategy justify its potential harms. Antioxid. Redox Signal. 26, 221-226.