Replacement of 24-h creatinine clearance by 2-h creatinine clearance in intensive care unit patients: a single-center study

Comparative analysis of two-hour creatinine clearance and the C-G formula for renal function assessment in critically ill patients

Objective and rationale

To investigate if the 2-h creatinine clearance (Ccr2) provides a more precise and timely assessment of renal function in critically ill patients compared to the Cockcroft-Gault formula (CrC-G).

Materials and methods

This cohort study incorporated 74 patients who were hospitalized for more than 48 h in the Intensive Care Unit over 6 months. A 24-h urine collection protocol was observed, and concurrently, 316 2-h urine specimens were obtained. Then calculated and analyzed the correlation and consistency between Ccr2, CrC-G, and 24-h creatinine clearance (Ccr24) values. The rates of change in Ccr2(ΔCcr2) and CrC-G(ΔCrC-G) were compared over two consecutive samples.

Results

The R-values of Ccr2 and Ccr24 in the early, middle and late 24 h were 0.640, 0.886 and 0.854 (P < 0.001), with biases of -2.1, 1.7, and 6.3 ml/min/1.73 m2, respectively. Meanwhile, the R-values for CrC-G and Ccr24 at these time points were 0.618, 0.822, and 0.828(P < 0.001), with biases of -14.0, -5.2, and -1.8 ml/min/1.73 m2, respectively. For patients with Ccr24≥60 ml/min/1.73 m2, the R-value of Ccr2 and Ccr24 during the middle 2 h was 0.852(P < 0.001), while the R-values for CrC-G and Ccr24 were 0.763(P < 0.001), with biases of -2.3 ml/min/1.73 m2 and -14.2 ml/min/1.73 m2 respectively. For the group with Ccr24 ≥ 120 ml/min/1.73 m2 (n = 72), both Ccr2 and Ccr24 displayed a statistically significant elevation compared to CrC-G (P < 0.001), yet no significant difference was observed between Ccr2 and Ccr24 (P = 0.289). Out of 50 patients, 46(92 %) experienced a ΔCcr2≥20 % at least once, compared to 20(40 %) with a ΔCrC-G≥20 %(P < 0.001). 25(50 %) with a ΔCcr2≥50 %, compared to 3(6 %) with a ΔCrC-G≥50 %(P < 0.001).

Conclusion

Ccr2 demonstrates a more accurate and more timely indicator of renal function in critically ill patients than CrC-G.

Abbreviated Urine Collection Compared With 24-Hour Urine Collection for Measuring Creatinine Clearance in Adult Critically Ill Patients: A Systematic Review

OBJECTIVE

To evaluate the accuracy of abbreviated urine collection (≤12 hours) compared with 24-hour urine collection for measuring creatinine clearance (CrCl) in critically ill adult patients.

DATA SOURCES

We searched PubMed, Embase, Web of Science, Google Scholar, and ProQuest Dissertations and Thesis Global; screened reference lists of included studies; and contacted the authors when needed. English studies only were considered with no restriction on dates.

STUDY SELECTION AND DATA EXTRACTION

After duplicate removal, 2 reviewers screened titles/abstracts, reviewed full-text articles, and extracted data independently. Studies that compared abbreviated versus 24-hour urine collection for measuring CrCl were included. We assessed the risk of bias using the QUADAS-2 tool. We extracted correlation coefficients, mean prediction errors (ME)-as a measure of bias, and root mean squared prediction errors (RMSE)-as a measure of precision.

DATA SYNTHESIS

Five studies were included, comprising 528 adult critically ill adults from surgical, medical, and trauma intensive care units (ICUs). Three studies had high risk of bias, and 2 had low risk. The studies evaluated different durations of urine collection, including 30-minute, 2-hour, 4-hour, 6-hour, and 12-hour. Mean 24-hour CrCl ranged from 57 mL/min/1.73 m2 to 103 mL/min. Abbreviated urine collection led to CrCl that correlated well with the 24-hour measured CrCl (correlation coefficient ranged from 0.8 to 0.95). Mean prediction error ranged from 5 mL/min/1.73 m2 to 16 mL/min (from 8% to 25% of the 24-hour CrCl). Root mean squared prediction error calculated from 1 study was 30.5 mL/min/1.73 m2.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

Abbreviated urine collection is used to measure CrCl for renal drug dosing in critically ill patients, but its accuracy is not well-established.

CONCLUSIONS

Abbreviated urine collection may overestimate CrCl compared with 24-hour urine collection. Larger, well-conducted studies are needed to evaluate the accuracy of CrCl measured using different durations of urine collection in critically ill patients.

Concordance between glomerular filtration rate estimation equations and 4-hour urinary creatinine clearance in critically ill patients with severe trauma

BACKGROUND AND OBJECTIVE

There is a growing body of evidence that the equations used to estimate the glomerular filtration rate (GFR) are not suitable in critically ill patients, a population whose GFR fluctuates continuously. Glomerular filtration is usually estimated by measuring urine creatinine clearance (CrCl) at various time points. The aim of our study was to evaluate the performance of the most widely used GFR calculators in the subpopulation of critically ill patients admitted for severe trauma, and to compare the results against determinations of CrCl in urine collected over a 4-h period (4h-CrCl).

MATERIAL AND METHODS

Observational study in patients hospitalized for severe trauma. We measured the 4h-CrCl and estimated GFR using the Cockcroft-Gault, modified Jelliffe, MDRD, t-MDRD, and CKD-EPI equations, adjusting the results for body surface area (BSA) (ml/min/1.73m2). Data were analysed using R version 4.0.4.

RESULTS

A total of 85 patients were included. Median age was 51 years, and 68 were men (78.82%). The mean BSA-adjusted 4h-CrCl (4h-ClCr/1.73m2) was 84.5 ml/min/1.73m2. We found that GFR estimated using the t-MDRD equation correlated significantly with 4h-CrCl/1.73m2. The Cockcroft-Gault equation correlated significantly with 4h-CrCl/1.73m2 when GFR was greater than 130ml/min/m2.

CONCLUSIONS

In ICU patients, glomerular filtration can be reliably estimated by determining urine CrCl, but GFR calculators are not accurate in this population.

Update on Therapeutic Drug Monitoring of Beta-Lactam Antibiotics in Critically Ill Patients—A Narrative Review

Beta-lactam antibiotics remain one of the most preferred groups of antibiotics in critical care due to their excellent safety profiles and their activity against a wide spectrum of pathogens. The cornerstone of appropriate therapy with beta-lactams is to achieve an adequate plasmatic concentration of a given antibiotic, which is derived primarily from the minimum inhibitory concentration (MIC) of the specific pathogen. In a critically ill patient, the plasmatic levels of drugs could be affected by many significant changes in the patient’s physiology, such as hypoalbuminemia, endothelial dysfunction with the leakage of intravascular fluid into interstitial space and acute kidney injury. Predicting antibiotic concentration from models based on non-critically ill populations may be misleading. Therapeutic drug monitoring (TDM) has been shown to be effective in achieving adequate concentrations of many drugs, including beta-lactam antibiotics. Reliable methods, such as high-performance liquid chromatography, provide the accurate testing of a wide range of beta-lactam antibiotics. Long turnaround times remain the main drawback limiting their widespread use, although progress has been made recently in the implementation of different novel methods of antibiotic testing. However, whether the TDM approach can effectively improve clinically relevant patient outcomes must be proved in future clinical trials.

Augmented renal clearance in the ICU: estimation, incidence, risk factors and consequences-a retrospective observational study

Background

Augmented renal clearance (ARC) remains poorly evaluated in ICU. The objective of this study is to provide a full description of ARC in ICU including prevalence, evolution profile, risk factors and outcomes.

Methods

This was a retrospective, single-center, observational study. All the patients older than 18 years admitted for the first time in Medical ICU, Bichat, University Hospital, APHP, France, between January 1, 2017, and November 31, 2020 and included into the Outcomerea database with an ICU length of stay longer than 72 h were included. Patients with chronic kidney disease were excluded. Glomerular filtration rate was estimated each day during ICU stay using the measured creatinine renal clearance (CrCl). Augmented renal clearance (ARC) was defined as a 24 h CrCl greater than 130 ml/min/m².

Results

312 patients were included, with a median age of 62.7 years [51.4; 71.8], 106(31.9%) had chronic cardiovascular disease. The main reason for admission was acute respiratory failure (184(59%)) and 196(62.8%) patients had SARS-COV2. The median value for SAPS II score was 32[24; 42.5]; 146(44%) and 154(46.4%) patients were under vasopressors and invasive mechanical ventilation, respectively. The overall prevalence of ARC was 24.6% with a peak prevalence on Day 5 of ICU stay. The risk factors for the occurrence of ARC were young age and absence of cardiovascular comorbidities. The persistence of ARC during more than 10% of the time spent in ICU was significantly associated with a lower risk of death at Day 30.

Conclusion

ARC is a frequent phenomenon in the ICU with an increased incidence during the first week of ICU stay. Further studies are needed to assess its impact on patient prognosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-022-01058-w.

The Japanese Clinical Practice Guidelines for Management of Sepsis and Septic Shock 2020 (J-SSCG 2020)

The Japanese Clinical Practice Guidelines for Management of Sepsis and Septic Shock 2020 (J-SSCG 2020), a Japanese-specific set of clinical practice guidelines for sepsis and septic shock created as revised from J-SSCG 2016 jointly by the Japanese Society of Intensive Care Medicine and the Japanese Association for Acute Medicine, was first released in September 2020 and published in February 2021. An English-language version of these guidelines was created based on the contents of the original Japanese-language version. The purpose of this guideline is to assist medical staff in making appropriate decisions to improve the prognosis of patients undergoing treatment for sepsis and septic shock. We aimed to provide high-quality guidelines that are easy to use and understand for specialists, general clinicians, and multidisciplinary medical professionals. J-SSCG 2016 took up new subjects that were not present in SSCG 2016 (e.g., ICU-acquired weakness [ICU-AW], post-intensive care syndrome [PICS], and body temperature management). The J-SSCG 2020 covered a total of 22 areas with four additional new areas (patient- and family-centered care, sepsis treatment system, neuro-intensive treatment, and stress ulcers). A total of 118 important clinical issues (clinical questions, CQs) were extracted regardless of the presence or absence of evidence. These CQs also include those that have been given particular focus within Japan. This is a large-scale guideline covering multiple fields; thus, in addition to the 25 committee members, we had the participation and support of a total of 226 members who are professionals (physicians, nurses, physiotherapists, clinical engineers, and pharmacists) and medical workers with a history of sepsis or critical illness. The GRADE method was adopted for making recommendations, and the modified Delphi method was used to determine recommendations by voting from all committee members.As a result, 79 GRADE-based recommendations, 5 Good Practice Statements (GPS), 18 expert consensuses, 27 answers to background questions (BQs), and summaries of definitions and diagnosis of sepsis were created as responses to 118 CQs. We also incorporated visual information for each CQ according to the time course of treatment, and we will also distribute this as an app. The J-SSCG 2020 is expected to be widely used as a useful bedside guideline in the field of sepsis treatment both in Japan and overseas involving multiple disciplines.

Acute kidney injury

Acute kidney injury (AKI) is defined by a sudden loss of excretory kidney function. AKI is part of a range of conditions summarized as acute kidney diseases and disorders (AKD), in which slow deterioration of kidney function or persistent kidney dysfunction is associated with an irreversible loss of kidney cells and nephrons, which can lead to chronic kidney disease (CKD). New biomarkers to identify injury before function loss await clinical implementation. AKI and AKD are a global concern. In low-income and middle-income countries, infections and hypovolaemic shock are the predominant causes of AKI. In high-income countries, AKI mostly occurs in elderly patients who are in hospital, and is related to sepsis, drugs or invasive procedures. Infection and trauma-related AKI and AKD are frequent in all regions. The large spectrum of AKI implies diverse pathophysiological mechanisms. AKI management in critical care settings is challenging, including appropriate volume control, nephrotoxic drug management, and the timing and type of kidney support. Fluid and electrolyte management are essential. As AKI can be lethal, kidney replacement therapy is frequently required. AKI has a poor prognosis in critically ill patients. Long-term consequences of AKI and AKD include CKD and cardiovascular morbidity. Thus, prevention and early detection of AKI are essential.

Assessment of kidney proximal tubular secretion in critical illness

BACKGROUNDSerum creatinine concentrations (SCrs) are used to determine the presence and severity of acute kidney injury (AKI). SCr is primarily eliminated by glomerular filtration; however, most mechanisms of AKI in critical illness involve kidney proximal tubules, where tubular secretion occurs. Proximal tubular secretory clearance is not currently estimated in the intensive care unit (ICU). Our objective was to estimate the kidney clearance of secretory solutes in critically ill adults.METHODSWe collected matched blood and spot urine samples from 170 ICU patients and from a comparison group of 70 adults with normal kidney function. We measured 7 endogenously produced secretory solutes using liquid chromatography-tandem mass spectrometry. We computed a composite secretion score incorporating all 7 solutes and evaluated associations with 28-day major adverse kidney events (MAKE28), defined as doubling of SCr, dialysis dependence, or death.RESULTSThe urine-to-plasma ratios of 6 of 7 secretory solutes were lower in critically ill patients compared with healthy individuals after adjustment for SCr. The composite secretion score was moderately correlated with SCr and cystatin C (r = -0.51 and r = -0.53, respectively). Each SD higher composite secretion score was associated with a 25% lower risk of MAKE28 (95% CI 9% to 38% lower) independent of severity of illness, SCr, and tubular injury markers. Higher urine-to-plasma ratios of individual secretory solutes isovalerylglycine and tiglylglycine were associated with MAKE28 after accounting for multiple testing.CONCLUSIONAmong critically ill adults, tubular secretory clearance is associated with adverse outcomes, and its measurement could improve assessment of kidney function and dosing of essential ICU medications.FUNDINGGrants from the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK/NIH) K23DK116967, the University of Washington Diabetes Research Center P30DK017047, an unrestricted gift to the Kidney Research Institute from the Northwest Kidney Centers, and the Vanderbilt O'Brien Kidney Center (NIDDK 5P30 DK114809-03). The funding sources had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript.

Evaluation of glomerular filtration rate using iohexol plasma clearance in critically ill patients with augmented renal creatinine clearance: A single-centre retrospective study

BACKGROUND

Augmented renal creatinine clearance (ARC) (≥130 ml min-1 1.73 m-2) is frequent in intensive care unit (ICU) patients and may impact patient outcome.

OBJECTIVES

To compare glomerular filtration rate (GFR) measured with iohexol plasma clearance and creatinine clearance in critically ill patients with augmented renal clearance.

DESIGN

Single-centre, retrospective study.

SETTING

French University Hospital ICU from November 2016 to May 2019.

PATIENTS

Adult patients with augmented renal clearance who had a measurement of iohexol plasma clearance.

MAIN OUTCOME MEASURE

Agreement between 6 h creatinine clearance (6 h CrCl) and iohexol plasma clearance (GFRio).

RESULTS

Twenty-nine patients were included. The median 6 h creatinine clearance was 195 [interquartile range (IQR) 162 to 251] ml min-1 1.73 m-2 and iohexol clearance was 133 [117 to 153] ml min-1 1.73 m-2. Sixteen patients (55%) had hyperfiltration (clearance >130 ml min-1 1.73 m-2) measured with iohexol clearance. Mean bias between iohexol and creatinine clearance was -80 [limits of agreement (LoA) -216 to 56 ml min-1 1.73 m-2]. For Cockcroft and Gault Modification of Diet in Renal Disease equation (MDRD), Chronic Kidney Disease Epidemiology Collaboration equation (CKD-EPI) formulae, mean biases were, respectively -27 (LoA -99 to 45), -14 (LoA -86 to 59) and 15 (LoA -33 to 64) ml min-1 1.73 m-2.

CONCLUSION

In the present study, we found that in patients with augmented renal creatinine clearance, half of the patients do not have hyperfiltration using iohexol clearance measurements. We observed an important bias between 6 h CrCl and GFRio with large LoA. In critically patients with ARC, 6 h CrCl does not reliably estimate GFR and 6 h CrCl nearly systematically overestimates renal function. Comparison of creatinine-based GFR estimations and GFRio show acceptable bias but wide LoA.

Augmented renal clearance. An unnoticed relevant event

Augmented renal clearance (ARC) is a phenomenon that can lead to a therapeutic failure of those drugs of renal clearance. The purpose of the study was to ascertain the prevalence of ARC in the critically ill patient, to study the glomerular filtration rate (GFR) throughout the follow-up and analyze the concordance between the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) estimation formula and measured GFR. Observational, prospective, multicenter study. ARC was defined as a creatinine clearance greater than 130 ml/min/1.73 m2. Eighteen hospitals were recruited. GFR measurements carried out twice weekly during a 2-month follow-up period. A total of 561 patients were included. ARC was found to have a non-negligible prevalence of 30%. More even, up to 10.7% already had ARC at intensive care unit (ICU) admission. No specific pattern of GFR was found during the follow-up. Patients in the ARC group were younger 56.5 (53.5-58.5) versus 66 (63.5-68.5) years than in the non-ARC group, p < 0.001. ICU mortality was lower in the ARC group, 6.9% versus 14.5%, p = 0.003. There was no concordance between the estimation of GFR by the CKD-EPI formula and GFR calculated from the 4-h urine. ARC is found in up to 30% of ICU patients, so renal removal drugs could be under dosed by up to 30%. And ARC is already detected on admission in 10%. It is a dynamic phenomenon without an established pattern that usually occurs in younger patients that can last for several weeks. And the CKD-EPI formula does not work to estimate the real creatinine clearance of these patients.

The Japanese Clinical Practice Guidelines for Management of Sepsis and Septic Shock 2020 (J-SSCG 2020)

The Japanese Clinical Practice Guidelines for Management of Sepsis and Septic Shock 2020 (J-SSCG 2020), a Japanese-specific set of clinical practice guidelines for sepsis and septic shock created as revised from J-SSCG 2016 jointly by the Japanese Society of Intensive Care Medicine and the Japanese Association for Acute Medicine, was first released in September 2020 and published in February 2021. An English-language version of these guidelines was created based on the contents of the original Japanese-language version. The purpose of this guideline is to assist medical staff in making appropriate decisions to improve the prognosis of patients undergoing treatment for sepsis and septic shock. We aimed to provide high-quality guidelines that are easy to use and understand for specialists, general clinicians, and multidisciplinary medical professionals. J-SSCG 2016 took up new subjects that were not present in SSCG 2016 (e.g., ICU-acquired weakness [ICU-AW], post-intensive care syndrome [PICS], and body temperature management). The J-SSCG 2020 covered a total of 22 areas with four additional new areas (patient- and family-centered care, sepsis treatment system, neuro-intensive treatment, and stress ulcers). A total of 118 important clinical issues (clinical questions, CQs) were extracted regardless of the presence or absence of evidence. These CQs also include those that have been given particular focus within Japan. This is a large-scale guideline covering multiple fields; thus, in addition to the 25 committee members, we had the participation and support of a total of 226 members who are professionals (physicians, nurses, physiotherapists, clinical engineers, and pharmacists) and medical workers with a history of sepsis or critical illness. The GRADE method was adopted for making recommendations, and the modified Delphi method was used to determine recommendations by voting from all committee members. As a result, 79 GRADE-based recommendations, 5 Good Practice Statements (GPS), 18 expert consensuses, 27 answers to background questions (BQs), and summaries of definitions and diagnosis of sepsis were created as responses to 118 CQs. We also incorporated visual information for each CQ according to the time course of treatment, and we will also distribute this as an app. The J-SSCG 2020 is expected to be widely used as a useful bedside guideline in the field of sepsis treatment both in Japan and overseas involving multiple disciplines.

Area under the Curve-Based Dosing of Vancomycin in Critically Ill Patients Using 6-Hour Urine Creatinine Clearance Measurement

BACKGROUND

The area under the curve- (AUC-) guided vancomycin dosing is the best strategy for individualized therapy in critical illnesses. Since AUC can be calculated directly using drug clearance (CLvan), any parameter estimating CLvan will be able to achieve the goal of 24-hour AUC (AUC24 h). The present study was aimed to determine CLvan based on 6-hour urine creatinine clearance measurement in critically ill patients with normal renal function.

METHOD

23 adult critically ill patients with an estimated glomerular filtration rate (eGFR) ≥60 mL/min who received vancomycin infusion were enrolled in this pilot study. Vancomycin pharmacokinetic parameters were determined for each patient using serum concentration data and a one-compartment model provided by MONOLIX software using stochastic approximation expectation-maximization (SAEM) algorithm. Correlation of CLvan with the measured creatinine clearance in 6-hour urine collection (CL6 h) and estimated creatinine clearance by the Cockcroft-Gault formula (CLCG) was investigated.

RESULTS

Data analysis revealed that CL6 h had a stronger correlation with CLvan rather than CLCG (r = 0.823 vs. 0.594; p < 0.001 vs. 0.003). The relationship between CLvan and CL6 h was utilized to develop the following equation for estimating CLvan: CLvan (mL/min) = ─137.4 + CL6 h (mL/min) + 2.5 IBW (kg) (R 2  = 0.826, p < 0.001). Regarding the described model, the following equation can be used to calculate the empirical dose of vancomycin for achieving the therapeutic goals in critically ill patients without renal impairment: total daily dose of vancomycin (mg) = (─137.4CL6-h (mL/min) + 2.5 IBW (kg)) × 0.06 AUC24 h (mg.hr/L).

CONCLUSION

For AUC estimation, CLvan can be obtained by collecting urine in a 6-hour period with good approximation in critically ill patients with normal renal function.

Estimation of piperacillin clearance with different glomerular filtration rate formulas in critically ill children

AIMS

Glomerular filtration rate (GFR) is difficult to assess in critically ill children using gold standard method and alternatives are needed. This study aimed to determine the most accurate GFR estimation formula for assessing piperacillin clearance in critically ill children, using a published piperacillin pharmacokinetics (PK) population model.

METHODS

All children hospitalized in the paediatric intensive care unit of a single institution who were receiving piperacillin were included. PK were described using the nonlinear mixed effect modelling software MONOLIX. In the initial PK model, GFR was estimated according to the Schwartz 1976 formula. We evaluated a set of 12 additional validated formulas, developed using plasma creatinine and/or cystatin C concentrations, in the building model to assess the lowest between-subject variability for piperacillin clearance.

RESULTS

We included 20 children with a median (range) postnatal age of 1.9 (0.1-19) years, body weight of 12.5 (3.5-69) kg. Estimated GFR according to the Schwartz 1976 formula was 160.5 (38-315) mL min^-1 1.73 m^-2 . Piperacillin clearance was best predicted by the Bouvet combined formula.

CONCLUSION

The combined Bouvet formula was the most accurate GFR estimation formula for assessing piperacillin clearance in critically ill children.

Augmented renal clearance is associated with inadequate antibiotic pharmacokinetic/pharmacodynamic target in Asian ICU population: a prospective observational study

BACKGROUND

Augmented renal clearance (ARC) is common in critically ill patients and could result in subtherapeutic antibiotic concentration. However, data in the Asian population are still lacking. The aim of this study was to explore the incidence and risk factors of ARC and its effect on β-lactam pharmacokinetics/pharmacodynamics (PK/PD) in Asian populations admitted to a medical ICU. In addition, we evaluated the appropriateness of using three estimated glomerular filtration (eGFR) formulas [Cockcroft-Gault (CG), Modification of Diet in Renal Disease (MDRD), and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI)] as screening tools.

METHODS

We measured 2-, 8-, and 24-hr creatinine clearance (CLCr) and calculated eGFR by using three formulas for each. ARC was defined as CLCr24hr >130 mL/min/1.73 m2. Concentrations at the mid-dosing interval and prior to the next dose were collected if patients received the β-lactam antibiotic of piperacillin/tazobactam, cefepime, and meropenem, to determine the PK/PD index of fT > MIC. Multiple logistic regression analysis was conducted to identify the risk factors for ARC. Pearson correlation coefficient and the Bland and Altman method were applied to assess the accuracy of CLCr2hr, CLCr8hr, and eGFR for predicting ARC.

RESULTS

Of 100 patients, 46 (46%) manifested ARC. Younger age (<50 years) and lower Sequential Organ Failure Assessment score increased the likelihood of ARC. ARC resulted in a low chance of achieving 50% fT >4MIC (33% vs 75%, p<0.01), 100% fT > MIC (23% vs 69%, p<0.01), and 100% fT >4MIC (3% vs 25%, p<0.02). CLCr8hr wielded the best correlation and agreement with CLCr24hr. eGFRCG was the most appropriate screening tool, and the optimal cutoff value for detecting ARC was 130.5 mL/min/1.73 m2.

CONCLUSION

ARC is associated with inadequate β-lactam PK/PD target in Asian ICU.

Effect of intraoperative dexmedetomidine on renal function after cytoreductive surgery and hyperthermic intraperitoneal chemotherapy: a randomized, placebo-controlled trial

INTRODUCTION

Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) predispose to postoperative renal dysfunction. Dexmedetomidine is an α₂ adrenoreceptor agonist, which has renoprotective effects after cardiac surgery.

OBJECTIVE

To assess the effect of dexmedetomidine on renal function after CRS and HIPEC.

MATERIALS

Thirty-eight patients undergoing CRS and HIPEC were randomized to receive dexmedetomidine (dexmedetomidine group, n = 19, loading 1 μg/kg over 20 min followed by infusion at 0.5 μg/kg/h) or 0.9% sodium chloride (control group, n = 19) during surgery. Creatinine clearance (CrCl) was assessed daily until postoperative day 7. Urine neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule (KIM)-1 were measured for 24 h after surgery.

RESULTS

There was no difference in the lowest CrCl value during the first 7 days postoperatively, but the % change from baseline to the lowest value was lower in the dexmedetomidine group than in the control group (p = .037). Urine NGAL and KIM-1 levels were increased over time in both groups, but the increases were significantly less in the dexmedetomidine group (p = .018 and 0.038, respectively). In the dexmedetomidine group, the length of intensive care unit stay was shorter (p = .034).

CONCLUSIONS

Intraoperative dexmedetomidine infusion did not improve renal function in terms of serum Cr-related indices following CRS and HIPEC. However, as the decrease in CrCl was attenuated and early tubular-injury markers were lower in the dexmedetomidine group, dexmedetomidine may have protective effects against early tubular injury in CRS and HIPEC. Clinical Trials Registry: http://clinicaltrials.gov (NCT02641938).

"Do not do" recommendations of the working groups of the Spanish Society of Intensive and Critical Care Medicine and Coronary Units (SEMICYUC) for the management of critically ill patients

The project "Commitment to Quality of Scientific Societies", promoted since 2013 by the Spanish Ministry of Health, seeks to reduce unnecessary health interventions that have not proven effective, have little or doubtful effectiveness, or are not cost-effective. The objective is to establish the "do not do" recommendations for the management of critically ill patients. A panel of experts from the 13 working groups (WGs) of the Spanish Society of Intensive and Critical Care Medicine and Coronary Units (SEMICYUC) was selected and nominated by virtue of clinical expertise and/or scientific experience to carry out the recommendations. Available scientific literature in the management of adult critically ill patients from 2000 to 2017 was extracted. The clinical evidence was discussed and summarized by the experts in the course of consensus finding of each WG, and was finally approved by the WGs after an extensive internal review process carried out during the first semester of 2017. A total of 65 recommendations were developed, of which 5 corresponded to each of the 13 WGs. These recommendations are based on the opinion of experts and scientific knowledge, and aim to reduce those treatments or procedures that do not add value to the care process; avoid the exposure of critical patients to potential risks; and improve the adequacy of health resources.

[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.

Acute Kidney Injury in the Critically Ill

Acute kidney injury (AKI) occurs frequently in the surgical intensive care unit and results in significant morbidity and mortality. AKI needs to be identified early and underlying causes treated or eliminated. Sepsis, major surgery such as coronary artery bypass, and hypovolemia are the most common causes and patients with underlying comorbidities have increased susceptibility. Treatment should begin by ensuring that patients are adequately resuscitated and all contributing causes are replaced or eliminated. After stabilization of hemodynamic status and elimination of contributing causes, treatment becomes largely supportive and may require the use of a renal replacement therapy.

Issues of Acute Kidney Injury Staging and Management in Sepsis and Critical Illness: A Narrative Review

Acute kidney injury (AKI) has a high incidence on intensive care units around the world and is a major complication in critically ill patients suffering from sepsis or septic shock. The short- and long-term complications are thereby devastating and impair the quality of life. Especially in terms of AKI staging, the determination of kidney function and the timing of dialytic AKI management outside of life-threatening indications are ongoing matters of debate. Despite several studies, a major problem remains in distinguishing between beneficial and unnecessary "early" or even harmful renal replacement therapy (RRT). The latter might prolong disease course and renal recovery. AKI scores, however, provide an insufficient outcome-predicting ability and the related estimation of kidney function via serum creatinine or blood urea nitrogen (BUN)/urea is not reliable in AKI and critical illness. Kidney independent alterations of creatinine- and BUN/urea-levels further complicate the situation. This review critically assesses the current AKI staging, issues and pitfalls of the determination of kidney function and RRT timing, as well as the potential harm reflected by unnecessary RRT. A better understanding is mandatory to improve future study designs and avoid unnecessary RRT for higher patient safety and lower health care costs.

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

OBJECTIVES

This study assessed the determinants of urinary output response to furosemide in acute kidney injury; specifically, whether the response is related to altered pharmacokinetics or pharmacodynamics.

DESIGN

Prospective cohort.

SETTING

Tertiary ICU.

PATIENTS

Thirty critically ill patients with acute kidney injury without preexisting renal impairment or recent diuretic exposure.

INTERVENTION

A single dose of IV furosemide.

MEASUREMENTS AND MAIN RESULTS

Baseline markers of intravascular volume status were obtained prior to administering furosemide. Six-hour creatinine clearance, hourly plasma/urinary furosemide concentrations, and hourly urinary output were used to assess furosemide pharmacokinetics/pharmacodynamics parameters. Of 30 patients enrolled, 11 had stage-1 (37%), nine had stage-2 (30%), and 10 had stage-3 (33%) Acute Kidney Injury Network acute kidney injury. Seventy-three percent were septic, 47% required norepinephrine, and 53% were mechanically ventilated. Urinary output doubled in 20 patients (67%) following IV furosemide. Measured creatinine clearance was strongly associated with the amount of urinary furosemide excreted and was the only reliable predictor of the urinary output after furosemide (area under the receiver-operating-characteristic curve, 0.75; 95% CI, 0.57-0.93). In addition to an altered pharmacokinetics (p < 0.01), a reduced pharmacodynamics response to furosemide also became important when creatinine clearance was reduced to less than 40 mL/min/1.73 m (p = 0.01). Acute kidney injury staging and markers of intravascular volume, including central venous pressure, brain-natriuretic-peptide concentration, and fractional urinary sodium excretion were not predictive of urinary output response to furosemide.

CONCLUSIONS

The severity of acute kidney injury, as reflected by the measured creatinine clearance, alters both pharmacokinetics and pharmacodynamics of furosemide in acute kidney injury, and was the only reliable predictor of the urinary output response to furosemide in acute kidney injury.

Recommendations of the Working Groups from the Spanish Society of Intensive and Critical Care Medicine and Coronary Units (SEMICYUC) for the management of adult critically ill patients

The standardization of the Intensive Care Medicine may improve the management of the adult critically ill patient. However, these strategies have not been widely applied in the Intensive Care Units (ICUs). The aim is to elaborate the recommendations for the standardization of the treatment of critical patients. A panel of experts from the thirteen working groups (WG) of the Spanish Society of Intensive and Critical Care Medicine and Coronary Units (SEMICYUC) was selected and nominated by virtue of clinical expertise and/or scientific experience to carry out the recommendations. Available scientific literature in the management of adult critically ill patients from 2002 to 2016 was extracted. The clinical evidence was discussed and summarised by the experts in the course of a consensus finding of every WG and finally approved by the WGs after an extensive internal review process that was carried out between December 2015 and December 2016. A total of 65 recommendations were developed, of which 5 corresponded to each of the 13 WGs. These recommendations are based on the opinion of experts and scientific knowledge, and are intended as a guide for the intensivists in the management of critical patients.

Prevention of acute kidney injury in Intensive Care Units

Acute kidney injury (AKI) is a growing concern in Intensive Care Units. The advanced age of our patients, with the increase in associated morbidity and the complexity of the treatments provided favor the development of AKI. Since no effective treatment for AKI is available, all efforts are aimed at prevention and early detection of the disorder in order to establish secondary preventive measures to impede AKI progression. In critical patients, the most frequent causes are sepsis and situations that result in renal hypoperfusion; preventive measures are therefore directed at securing hydration and correct hemodynamics through fluid perfusion and the use of inotropic or vasoactive drugs, according to the underlying disease condition. Apart from these circumstances, a number of situations could lead to AKI, related to the administration of nephrotoxic drugs, intra-tubular deposits, the administration of iodinated contrast media, liver failure and major surgery (mainly heart surgery). In these cases, in addition to hydration, there are other specific preventive measures adapted to each condition.

Assessment of Modification of Diet in Renal Disease Equation to Predict Reference Serum Creatinine Value in Severe Trauma Patients: Lessons From an Observational Study of 775 Cases

OBJECTIVE

We assessed the Modification of Diet in Renal Disease (MDRD) performance to predict serum creatinine (SCr) in severe trauma population and determined the best theoretical glomerular filtration rate (GFR) to use in this estimation.

BACKGROUND

Baseline SCr may be misestimated in severe trauma patients because of their specific demographic characteristics including renal hyperfiltration. However, the back-calculated MDRD equation is supposed to estimate SCr using a predetermined GFR of 75 mL/min/1.73 m.

METHODS

All severe trauma patients with a normal SCr were retrospectively included between January 2005 and January 2011. For each patient, the lowest SCr (oSCr) observed during the first week was used to estimate the GFR. The median GFR in period 1 (2005-2006) was determined. The back-calculated MDRD performance was assessed in period 2 (2007-2011) to predict oSCr by agreement, precision, and accuracy using a GFR of 75 mL/min/1.73 m (eSCr75-MDRD) or the median GFR observed in period 1 (eSCrTRAUMA-MDRD).

RESULTS

A total of 775 patients were studied: mean age, 37.7 ± 17 years; mean Injury Severity Score, 19 ± 11; 75% of male. In period 1 (n = 243), median GFR was 121 mL/min/1.73 m. In period 2 (n = 532), eSCrTRAUMA-MDRD demonstrated better agreement in predicting oSCr than eSCr75-MDRD (mean bias 2 vs 35 μmol/L; P < 0.001). Both precision (14 vs 39 μmol/L, respectively) and accuracy were significantly improved with eSCrTRAUMA-MDRD. Proportion of estimated SCr values that deviated less than 15%, 30%, or 50% was also higher with eSCrTRAUMA-MDRD (P < 0.001).

CONCLUSIONS

The eSCr75-MDRD equation systematically overestimates oSCr of severe trauma patients. The eSCrTRAUMA-MDRD equation determined was statistically superior allowing more accurate qualification of acute kidney injury.

Acute kidney injury: Renal disease in the ICU

Acute kidney injury (AKI) in the ICU frequently requires costly supportive therapies, has high morbidity, and its long-term prognosis is not as good as it has been presumed so far. Consequently, AKI generates a significant burden for the healthcare system. The problem is that AKI lacks an effective treatment and the best approach relies on early secondary prevention. Therefore, to facilitate early diagnosis, a broader definition of AKI should be established, and a marker with more sensitivity and early-detection capacity than serum creatinine - the most common marker of AKI - should be identified. Fortunately, new classification systems (RIFLE, AKIN or KDIGO) have been developed to solve these problems, and the discovery of new biomarkers for kidney injury will hopefully change the way we approach renal patients. As a first step, the concept of renal failure has changed from being a "static" disease to being a "dynamic process" that requires continuous evaluation of kidney function adapted to the reality of the ICU patient.

The use and risks of antibiotics in critically ill patients

INTRODUCTION

The altered pathophysiology in critically ill patients presents a unique challenge in both the diagnosis of infection and the appropriate prescription of antibiotics. In this context, the importance of effective and timely treatment needs to be weighed against the individual and community harms associated with antibiotic collateral damage and antibiotic resistance.

AREAS COVERED

We evaluate the principles of antibiotic use in critically ill patients, including dose optimisation, use of combination antibiotic therapy, therapeutic drug monitoring, appropriate antibiotic therapy duration, de-escalation, and utilisation of sepsis biomarkers. We also describe the potential risks associated with antibiotic therapy including antibiotic resistance, delayed treatment, treatment failure, and collateral damage.

EXPERT OPINION

Prescribing teams must be aware of the impact of critical illness on their patients and tailor antibiotic therapy appropriately to prevent the significant harms associated with suboptimal antibiotic administration.

[Antibiotic dosing for renal function disorders and continuous renal replacement therapy]

For patients with acute kidney injury (AKI) and continuous renal replacement therapy, it is essential that the dosing of antibiotics is adequately adjusted in order to achieve an effective drug level above the minimum inhibition concentration but avoiding toxic side effects. In the selection of substances, preference should be given to antibiotics with a broad therapeutic spectrum, low incidence of side effects and, as far as possible, extrarenal elimination. Determination of serum levels should always be carried out, when this is possible. In any case, a sufficiently high loading dose should be included. An accurate as possible estimation of residual renal function and calculation of the mechanical clearance allows determination of the necessary maintenance dosage, which is acceptably accurate for clinical needs. Recent studies have shown that under modern continuous renal replacement therapy, the extent of elimination of antibiotics is regularly underestimated so that nowadays, the risk of antibiotic underdosing is higher than toxicity due to overdosing.

[Augmented renal clearance in critically ill patients: incidence, associated factors and effects on vancomycin treatment]

OBJECTIVE

An augmented renal clearance has been described in some groups of critically ill patients, and it might induce sub-optimal concentrations of drugs eliminated by glomerular filtration, mainly antibiotics. Studies on its occurrence and determinants are lacking. Our goals were to determine the incidence and associated factors of augmented renal clearance and the effects on vancomycin concentrations and dosing in a series of intensive care unit patients.

METHODS

We prospectively studied 363 patients admitted during 1 year to a clinical-surgical intensive care unit. Patients with serum creatinine >1.3 mg/dL were excluded. Creatinine clearance was calculated from a 24-hour urine collection. Patients were grouped according to the presence of augmented renal clearance (creatinine clearance >120 mL/min/1.73 m²), and possible risk factors were analyzed with bivariate and logistic regression analysis. In patients treated with vancomycin, dosage and plasma concentrations were registered.

RESULTS

Augmented renal clearance was present in 103 patients (28%); they were younger (48±15 versus 65±17 years, p<0.0001), had more frequent obstetric (16 versus 7%, p=0.0006) and trauma admissions (10 versus 3%, p=0.016) and fewer comorbidities. The only independent determinants for the development of augmented renal clearance were age (OR 0.95; p<0.0001; 95%CI 0.93-0.96) and absence of diabetes (OR 0.34; p=0.03; 95%CI 0.12-0.92). Twelve of the 46 patients who received vancomycin had augmented renal clearance and despite higher doses, had lower concentrations.

CONCLUSIONS

In this cohort of critically ill patients, augmented renal clearance was a common finding. Age and absence of diabetes were the only independent determinants. Therefore, younger and previously healthy patients might require larger vancomycin dosing.

Antibiotic dose optimization in critically ill patients

The judicious use of existing antibiotics is essential for preserving their activity against infections. In the era of multi-drug resistance, this is of particular importance in clinical areas characterized by high antibiotic use, such as the ICU. Antibiotic dose optimization in critically ill patients requires sound knowledge not only of the altered physiology in serious infections - including severe sepsis, septic shock and ventilator-associated pneumonia - but also of the pathogen-drug exposure relationship (i.e. pharmacokinetic/pharmacodynamic index). An important consideration is the fact that extreme shifts in organ function, such as those seen in hyperdynamic patients or those with multiple organ dysfunction syndrome, can have an impact upon drug exposure, and constant vigilance is required when reviewing antibiotic dosing regimens in the critically ill. The use of continuous renal replacement therapy and extracorporeal membrane oxygenation remain important interventions in these patients; however, both of these treatments can have a profound effect on antibiotic exposure. We suggest placing emphasis on the use of therapeutic drug monitoring and dose individualization when optimizing therapy in these settings.

Population pharmacokinetics of imipenem in critically ill patients with suspected ventilator-associated pneumonia and evaluation of dosage regimens

AIMS

Significant alterations in the pharmacokinetics (PK) of antimicrobials have been reported in critically ill patients. We describe PK parameters of imipenem in intensive care unit (ICU) patients with suspected ventilator-associated pneumonia and evaluate several dosage regimens.

METHODS

This French multicentre, prospective, open-label study was conducted in ICU patients with a presumptive diagnosis of ventilator-associated pneumonia caused by Gram-negative bacilli, who empirically received imipenem intravenously every 8 h. Plasma imipenem concentrations were measured during the fourth imipenem infusion using six samples (trough, 0.5, 1, 2, 5 and 8 h). Data were analysed with a population approach using the stochastic approximation expectation maximization algorithm in Monolix 4.2. A Monte Carlo simulation was performed to evaluate the following six dosage regimens: 500, 750 or 1000 mg with administration every 6 or 8 h. The pharmacodynamic target was defined as the probability of achieving a fractional time above the minimal inhibitory concentration (MIC) of >40%.

RESULTS

Fifty-one patients were included in the PK analysis. Imipenem concentration data were best described by a two-compartment model with three covariates (creatinine clearance, total bodyweight and serum albumin). Estimated clearance (between-subject variability) was 13.2 l h(-1) (38%) and estimated central volume 20.4 l (31%). At an MIC of 4 μg ml(-1) , the probability of achieving 40% fractional time > MIC was 91.8% for 0.5 h infusions of 750 mg every 6 h, 86.0% for 1000 mg every 8 h and 96.9% for 1000 mg every 6 h.

CONCLUSIONS

This population PK model accurately estimated imipenem concentrations in ICU patients. The simulation showed that for these patients, the best dosage regimen of imipenem is 750 mg every 6 h and not 1000 mg every 8 h.

Estimation of creatinine clearance using plasma creatinine or cystatin C: a secondary analysis of two pharmacokinetic studies in surgical ICU patients

BACKGROUND

In ICU patients, glomerular filtration is often impaired, but also supraphysiological values are observed ("augmented renal clearance", >130 mL/min/1.73 m(2)). Renally eliminated drugs (e.g. many antibiotics) must be adjusted accordingly, which requires a quantitative measure of renal function throughout all the range of clinically encountered values. Estimation from plasma creatinine is standard, but cystatin C may be a valuable alternative.

METHODS

This was a secondary analysis of renal function parameters in 100 ICU patients from two pharmacokinetic studies on vancomycin and betalactam antibiotics. Estimated clearance values obtained by the Cockcroft-Gault formula (eCLCG), the CKD-EPI formula (eCLCKD-EPI) or the cystatin C based Hoek formula (eCLHoek) were compared with the measured endogenous creatinine clearance (CLCR). Agreement of values was assessed by modified Bland-Altman plots and by calculating bias (median error) and precision (median absolute error). Sensitivity and specificity of estimates to identify patients with reduced (<60 mL/min/1.73 m(2)) or augmented (>130 mL/min/1.73 m(2)) CLCR were calculated.

RESULTS

The CLCR was well distributed from highly compromised to supraphysiological values (median 73.2, range 16.8-234 mL/min/1.73 m(2)), even when plasma creatinine was not elevated (≤0.8 mg/dL for women, ≤1.1 mg/dL for men). Bias and precision were +13.5 mL/min/1.73 m(2) and ±18.5 mL/min/1.73 m(2) for eCLCG, +7.59 and ±16.8 mL/min/1.73 m(2) for eCLCKD-EPI, and -4.15 and ±12.9 mL/min/1.73 m(2) for eCLHoek, respectively, with eCLHoek being more precise than the other two (p < 0.05). The central 95% of observed errors fell between -59.8 and +250 mL/min/1.73 m(2) for eCLCG, -83.9 and +79.8 mL/min/1.73 m(2) for eCLCKD-EPI, and -103 and +27.9 mL/min/1.73 m(2) for eCLHoek. Augmented renal clearance was underestimated by eCLCKD-EPI and eCLHoek. Patients with reduced CLCR were identified with good specificity by eCLCG, eCLCKD-EPI and eCLHoek (0.95, 0.97 and 0.91, respectively), but with less sensitivity (0.55, 0.55 and 0.83). For augmented renal clearance, specificity was 0.81, 0.96 and 0.96, but sensitivity only 0.69, 0.25 and 0.38.

CONCLUSIONS

Normal plasma creatinine concentrations can be highly misleading in ICU patients. Agreement of the cystatin C based eCLHoek with CLCR is better than that of the creatinine based eCLCG or eCLCKD-EPI. Detection and quantification of augmented renal clearance by estimates is problematic, and should rather rely on CLCR.

Comparison of different equations to assess glomerular filtration in critically ill patients

PURPOSE

To evaluate equations for estimation of glomerular filtration rate (GFR) and measured urinary creatinine clearance, compared to measured GFR in critically ill patients.

METHODS

GFR was measured using inulin clearance. Multiple blood samples were collected per patient for determination of serum creatinine, cystatin C and inulin. GFR was estimated by the use of the following estimation equations (eGFR): four commonly used creatinine-based equations [Cockcroft-Gault, Modification of Diet in Renal Disease (both the short and long formula) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI)], five cystatin C based estimation equations (Hoek, Larsson, Filler, Le Bricon, CKD-EPIcys) and one equation combining cystatin C and serum creatinine (CKD-EPIcr-cys). In addition we measured urinary creatinine clearance. Bias, precision and accuracy of all estimates were compared to those of the inulin clearance.

RESULTS

Data were collected from 83 patients, of whom 68 were considered evaluable. The median age was 58 years [interquartile range (IQR) 39-68]. The median inulin clearance was 80 mL/min/1.73 m(2) (IQR 31-114). Equations based on creatinine had much bias and poor precision and accuracy. Measured urinary creatinine clearances overestimated GFR. Equations based on cystatin C were free of bias, but also had limited precision and accuracy.

CONCLUSIONS

In this cohort of patients, estimates of GFR had low accuracy and precision. Cystatin C based formulas, especially CKD-EPIcr-cys, showed limited bias; however, the accuracy and precision of these estimates were still insufficient. Measured urinary creatinine clearance overestimates GFR, but may provide a cheap alternative, when this is taken into account.

Select critically ill patients at risk of augmented renal clearance: experience in a Malaysian intensive care unit

Augmented renal clearance (ARC) refers to increased solute elimination by the kidneys. ARC has considerable implications for altered drug concentrations. The aims of this study were to describe the prevalence of ARC in a select cohort of patients admitted to a Malaysian intensive care unit (ICU) and to compare measured and calculated creatinine clearances in this group. Patients with an expected ICU stay of <24 hours plus an admission serum creatinine concentration <120 µmol/l, were enrolled from May to July 2013. Twenty-four hour urinary collections and serum creatinine concentrations were used to measure creatinine clearance. A total of 49 patients were included, with a median age of 34 years. Most study participants were male and admitted after trauma. Thirty-nine percent were found to have ARC. These patients were more commonly admitted in emergency (P=0.03), although no other covariants were identified as predicting ARC, likely due to the inclusion criteria and the study being under-powered. Significant imprecision was demonstrated when comparing calculated Cockcroft-Gault creatinine clearance (Crcl) and measured Crcl. Bias was larger in ARC patients, with Cockcroft-Gault Crcl being significantly lower than measured Crcl (P <0.01) and demonstrating poor correlation (rs=-0.04). In conclusion, critically ill patients with 'normal' serum creatinine concentrations have varied Crcl. Many are at risk of ARC, which may necessitate individualised drug dosing. Furthermore, significant bias and imprecision between calculated and measured Crcl exists, suggesting clinicians should carefully consider which method they employ in assessing renal function.

The definition of acute kidney injury and its use in practice

Acute kidney injury (AKI) is a common syndrome that is independently associated with increased mortality. A standardized definition is important to facilitate clinical care and research. The definition of AKI has evolved rapidly since 2004, with the introduction of the Risk, Injury, Failure, Loss, and End-stage renal disease (RIFLE), AKI Network (AKIN), and Kidney Disease Improving Global Outcomes (KDIGO) classifications. RIFLE was modified for pediatric use (pRIFLE). They were developed using both evidence and consensus. Small rises in serum creatinine are independently associated with increased mortality, and hence are incorporated into the current definition of AKI. The recent definition from the international KDIGO guideline merged RIFLE and AKIN. Systematic review has found that these definitions do not differ significantly in their performance. Health-care staff caring for children or adults should use standard criteria for AKI, such as the pRIFLE or KDIGO definitions, respectively. These efforts to standardize AKI definition are a substantial advance, although areas of uncertainty remain. The new definitions have enabled the use of electronic alerts to warn clinicians of possible AKI. Novel biomarkers may further refine the definition of AKI, but their use will need to produce tangible improvements in outcomes and cost effectiveness. Further developments in AKI definitions should be informed by research into their practical application across health-care providers. This review will discuss the definition of AKI and its use in practice for clinicians and laboratory scientists.

Measuring renal function in critically ill patients: tools and strategies for assessing glomerular filtration rate

PURPOSE OF REVIEW

Alterations in kidney function are common in critically ill patients and are generally assessed by changes in serum creatinine (sCr) or urine output, which are considered surrogates for glomerular filtration rate (GFR) but do not reflect the overall kidney function. There is a great need for more reliable measurements of glomerular filtration in order to guide diagnosis and therapy for acute kidney injury. In this review, we will focus on recent advances to measure GFR that could help to better evaluate kidney function and improve patient care.

RECENT FINDINGS

Standardized assays for sCr measurements, the use of a more precise scale with more frequent measurements, and the interpretation of the results based on patient's characteristics can increase the clinical value of sCr. New endogenous and exogenous markers will provide a more precise estimation. Imaging techniques are being developed and will probably be available in the near future. New gold standards for glomerular filtration will help in the development and improvement in the use of new biomarkers of kidney injury.

Comparative study of three methods of estimation of creatinine clearance in critically ill patients

BACKGROUND

At the bedside, the reference method for creatinine clearance determination is based on the measurement of creatinine concentrations in urine and serum (mCrCl). Several models are available to calculate the creatinine clearance from the serum creatinine concentration. This observational survey aimed at testing the hypothesis that the proposed equations are unreliable to determine accurate creatinine clearance in patients admitted to intensive care unit (ICU).

METHOD

Creatinine clearance was determined by the use of mCrCl. Then, we compared three equations: Cockcroft-Gault (CG), Simplified Modification of Diet in Renal Disease (MDRDs), and Chronic Kidney Disease Epidemiology (CKD-EPI) in 156 consecutive patients within the first 24hours after ICU admission. We tested the hypothesis that the three equations were equivalent. The agreement between the three equations was evaluated by linear regression and Bland and Altman analysis.

RESULTS

Bland and Altman analysis showed similar agreement between the three equations. The biases and precisions were -4.8±51, -1.3±50, and 8.2±44 for CG, MDRDs, and CKD-EPI equations, respectively (P>0.05). The precisions were similar for the three equations (P>0.05). The percentages of outliers at ±30% were 44%, 45%, and 49% for CG, MDRDs, and CKD-EPI, respectively (P>0.05).

CONCLUSION

Regarding the high percentage of outliers, the use of these equations cannot be recommended in ICU patients.

A comparison of CKD-EPI estimated glomerular filtration rate and measured creatinine clearance in recently admitted critically ill patients with normal plasma creatinine concentrations

Background

The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) estimated glomerular filtration rate (eGFR) has been widely integrated into clinical practice. Although useful in screening for CKD, its’ application in critically ill patients with normal plasma creatinine concentrations remains uncertain. The aim of this study was to assess the performance of CKD-EPI eGFR in comparison to creatinine clearance (CL_CR) in this setting.

Methods

This prospective observational study was performed in a tertiary level, university affiliated intensive care unit (ICU). Study participants had to have an expected ICU length of stay > 24 hours, a plasma creatinine concentration < 121 μmol/L, and no history of prior renal replacement therapy or CKD. CKD-EPI eGFR was compared against 8-hour measured urinary CL_CR. Data capture occurred within 48 hours of admission.

Results

One hundred and ten patients (n = 110) were enrolled in the study. 63.6% were male, the mean age was 50.9 (16.9) years, 57.3% received invasive mechanical ventilation, and 30% required vasopressor support. The mean CL_CR was 125 (45.1) ml/min/1.73 m², compared to a CKD-EPI eGFR of 101 (23.7) ml/min/1.73 m² (P < 0.001). Moderate correlation was evident (r = 0.72), although there was significant bias and imprecision (24.4 +/− 32.5 ml/min/1.73 m²). In those patients with a CKD-EPI eGFR between 60–119 ml/min/1.73 m² (n = 77), 41.6% displayed augmented renal clearance (CL_CR ≥ 130 ml/min/1.73 m²), while 7.8% had a CL_CR < 60 ml/min/1.73 m².

Conclusions

These data suggest CKD-EPI eGFR and measured CL_CR produce significantly disparate results when estimating renal function in this population. Clinicians should consider carefully which value they employ in clinical practice, particularly drug dose modification.

Measuring glomerular filtration rate in the intensive care unit: no substitutes please

Acute kidney injury (AKI), due to its increasing incidence, associated morbidity and mortality, and potential for development of chronic kidney disease with acceleration to end-stage renal disease, has become of major interest to nephrologists and critical care physicians. The development of biomarkers to diagnose AKI, quantify risk and predict prognosis is receiving considerable attention. Yet techniques to accurately assess functional changes within patients still rely on the use of an insensitive marker (creatinine), creatinine-based estimating equations and unreliable urinary tests. Therefore, it is critical that functional tests be developed and used in combination with biomarkers, thus allowing improved care in AKI and chronic kidney disease patient populations.

Approaches for dosage individualisation in critically ill patients

INTRODUCTION

Pharmacokinetic variability in critically ill patients is the result of the overlapping of multiple pathophysiological and clinical factors. Unpredictable exposure from standard dosage regimens may influence the outcome of treatment. Therefore, strategies for dosage individualisation are recommended in this setting.

AREAS COVERED

The authors focus on several approaches for dosage individualisation that have been developed, ranging from the well-established therapeutic drug monitoring (TDM) up to the innovative application of pharmacogenomics criteria. Furthermore, the authors summarise the specific population pharmacokinetic models for different drugs developed for critically ill patients to improve the initial dosage selection and the Bayesian forecasting of serum concentrations. The authors also consider the use of Monte Carlo simulation for the selection of dosage strategies.

EXPERT OPINION

Pharmacokinetic/pharmacodynamics (PK/PD) modelling and dosage individualisation methods based on mathematical and statistical criteria will contribute in improving pharmacologic treatment in critically ill patients. Moreover, substantial effort will be necessary to integrate pharmacogenomics criteria into critical care practice. The lack of availability of target biomarkers for dosage adjustment emphasizes the value of TDM which allows a large part of treatment outcome variability to be controlled.

Assessing glomerular filtration rate (GFR) in critically ill patients with acute kidney injury--true GFR versus urinary creatinine clearance and estimating equations

INTRODUCTION

Estimation of kidney function in critically ill patients with acute kidney injury (AKI), is important for appropriate dosing of drugs and adjustment of therapeutic strategies, but challenging due to fluctuations in kidney function, creatinine metabolism and fluid balance. Data on the agreement between estimating and gold standard methods to assess glomerular filtration rate (GFR) in early AKI are lacking. We evaluated the agreement of urinary creatinine clearance (CrCl) and three commonly used estimating equations, the Cockcroft Gault (CG), the Modification of Diet in Renal Disease (MDRD) and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations, in comparison to GFR measured by the infusion clearance of chromium-ethylenediaminetetraacetic acid (51Cr-EDTA), in critically ill patients with early AKI after complicated cardiac surgery.

METHODS

Thirty patients with early AKI were studied in the intensive care unit, 2 to 12 days after complicated cardiac surgery. The infusion clearance for 51Cr-EDTA obtained as a measure of GFR (GFR51Cr-EDTA) was calculated from the formula: GFR (mL/min/1.73m2)=(51Cr-EDTA infusion rate×1.73)/(arterial 51Cr-EDTA×body surface area) and compared with the urinary CrCl and the estimated GFR (eGFR) from the three estimating equations. Urine was collected in two 30-minute periods to measure urine flow and urine creatinine. Urinary CrCl was calculated from the formula: CrCl (mL/min/1.73m2)=(urine volume×urine creatinine×1.73)/(serum creatinine×30 min×body surface area).

RESULTS

The within-group error was lower for GFR51Cr-EDTA than the urinary CrCl method, 7.2% versus 55.0%. The between-method bias was 2.6, 11.6, 11.1 and 7.39 ml/min for eGFRCrCl, eGFRMDRD, eGFRCKD-EPI and eGFRCG, respectively, when compared to GFR51Cr-EDTA. The error was 103%, 68.7%, 67.7% and 68.0% for eGFRCrCl, eGFRMDRD, eGFRCKD-EPI and eGFRCG, respectively, when compared to GFR51Cr-EDTA.

CONCLUSIONS

The study demonstrated poor precision of the commonly utilized urinary CrCl method for assessment of GFR in critically ill patients with early AKI, suggesting that this should not be used as a reference method when validating new methods for assessing kidney function in this patient population. The commonly used estimating equations perform poorly when estimating GFR, with high biases and unacceptably high errors.