Oliguria in the ICU. Systematic approach to diagnosis and treatment

Robust monitoring of hypovolemia in intensive care patients using photoplethysmogram signals

The paper presents a fingertip photoplethysmography based technique to assess patient fluid status that is robust to waveform artifacts and health variability in the underlying patient population. The technique is intended for use in intensive care units, where patients are at risk for hypovolemia, and signal artifacts and inter-patient variations in health are common. Input signals are preprocessed to remove artifact, then a parameter-invariant statistic is calculated to remove effects of patient-specific physiology. Patient data from the Physionet MIMICII database was used to evaluate the performance of this technique. The proposed method was able to detect hypovolemia within 24 hours of onset in all hypovolemic patients tested, while producing minimal false alarms over non-hypovolemic patients.

Performance and user evaluation of a novel capacitance-based automatic urinometer compared with a manual standard urinometer after elective cardiac surgery

INTRODUCTION

In the intensive care setting, most physiologic parameters are monitored automatically. However, urine output (UO) is still monitored hourly by manually handled urinometers. In this study, we evaluated an automatic urinometer (AU) and compared it with a manual urinometer (MU).

METHODS

This prospective study was carried out in the intensive care unit of a cardiothoracic surgical clinic. In postoperative patients (n = 34) with indwelling urinary catheters and an expected stay of 24 hours or more, hourly UO samples were measured with an AU (Sippi, n = 220; Observe Medical, Gothenburg, Sweden) or an MU (UnoMeter™ 500, n = 188; Unomedical, Birkerød, Denmark) and thereafter validated by cylinder measurements. Malposition of the instrument at the time of reading excluded measurement. Data were analyzed with the Bland-Altman method. The performance of the MU was used as the minimum criterion of acceptance when the AU was evaluated. The loss of precision with the MU due to temporal deviation from fixed hourly measurements was recorded (n = 108). A questionnaire filled out by the ward staff (n = 28) was used to evaluate the ease of use of the AU compared with the MU.

RESULTS

Bland-Altman analysis showed a smaller mean bias for the AU (+1.9 ml) compared with the MU (+5.3 ml) (P <0.0001). There was no statistical difference in measurement precision between the two urinometers, as defined by their limits of agreement (±15.2 ml vs. ±16.6 ml, P = 0.11). The mean temporal variation with the MU was ±7.4 minutes (±12.4%), and the limits of agreement were ±23.9 minutes (±39.8%), compared with no temporal variation with the AU (P <0.0001). The ward staff considered the AU easy to learn to use and rated it higher than the MU (P <0.0001).

CONCLUSIONS

The AU was not inferior to the MU and was significantly better in terms of bias, temporal deviation and staff opinion, although the clinical relevance of these findings may be open to discussion.

Fluid balance, intradialytic hypotension, and outcomes in critically ill patients undergoing renal replacement therapy: a cohort study

Introduction

In this cohort study, we explored the relationship between fluid balance, intradialytic hypotension and outcomes in critically ill patients with acute kidney injury (AKI) who received renal replacement therapy (RRT).

Methods

We analysed prospectively collected registry data on patients older than 16 years who received RRT for at least two days in an intensive care unit at two university-affiliated hospitals. We used multivariable logistic regression to determine the relationship between mean daily fluid balance and intradialytic hypotension, both over seven days following RRT initiation, and the outcomes of hospital mortality and RRT dependence in survivors.

Results

In total, 492 patients were included (299 male (60.8%), mean (standard deviation (SD)) age 62.9 (16.3) years); 251 (51.0%) died in hospital. Independent risk factors for mortality were mean daily fluid balance (odds ratio (OR) 1.36 per 1000 mL positive (95% confidence interval (CI) 1.18 to 1.57), intradialytic hypotension (OR 1.14 per 10% increase in days with intradialytic hypotension (95% CI 1.06 to 1.23)), age (OR 1.15 per five-year increase (95% CI 1.07 to 1.25)), maximum sequential organ failure assessment score on days 1 to 7 (OR 1.21 (95% CI 1.13 to 1.29)), and Charlson comorbidity index (OR 1.28 (95% CI 1.14 to 1.44)); higher baseline creatinine (OR 0.98 per 10 μmol/L (95% CI 0.97 to 0.996)) was associated with lower risk of death. Of 241 hospital survivors, 61 (25.3%) were RRT dependent at discharge. The only independent risk factor for RRT dependence was pre-existing heart failure (OR 3.13 (95% CI 1.46 to 6.74)). Neither mean daily fluid balance nor intradialytic hypotension was associated with RRT dependence in survivors. Associations between these exposures and mortality were similar in sensitivity analyses accounting for immortal time bias and dichotomising mean daily fluid balance as positive or negative. In the subgroup of patients with data on pre-RRT fluid balance, fluid overload at RRT initiation did not modify the association of mean daily fluid balance with mortality.

Conclusions

In this cohort of patients with AKI requiring RRT, a more positive mean daily fluid balance and intradialytic hypotension were associated with hospital mortality but not with RRT dependence at hospital discharge in survivors.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-014-0624-8) contains supplementary material, which is available to authorized users.

An observational study fluid balance and patient outcomes in the Randomized Evaluation of Normal vs. Augmented Level of Replacement Therapy trial

OBJECTIVE

To examine associations between mean daily fluid balance during intensive care unit study enrollment and clinical outcomes in patients enrolled in the Randomized Evaluation of Normal vs. Augmented Level (RENAL) replacement therapy study.

DESIGN

Statistical analysis of data from multicenter, randomized, controlled trials.

SETTING

Thirty-five intensive care units in Australia and New Zealand.

PATIENTS

Cohort of 1453 patients enrolled in the RENAL study.

INTERVENTIONS

We analyzed the association between daily fluid balance on clinical outcomes using multivariable logistic regression, Cox proportional hazards, time-dependent analysis, and repeated measure analysis models.

MEASUREMENTS AND MAIN RESULTS

During intensive care unit stay, mean daily fluid balance among survivors was -234 mL/day compared with +560 mL/day among nonsurvivors (p < .0001). Mean cumulative fluid balance over the same period was -1941 vs. +1755 mL (p = .0003). A negative mean daily fluid balance during study treatment was independently associated with a decreased risk of death at 90 days (odds ratio 0.318; 95% confidence interval 0.24-0.43; p < .000.1) and with increased survival time (p < .0001). In addition, a negative mean daily fluid balance was associated with significantly increased renal replacement-free days (p = .0017), intensive care unit-free days (p < .0001), and hospital-free days (p = .01). These findings were unaltered after the application of different statistical models.

CONCLUSIONS

In the RENAL study, a negative mean daily fluid balance was consistently associated with improved clinical outcomes. Fluid balance may be a target for specific manipulation in future interventional trials of critically ill patients receiving renal replacement therapy.

Oliguria as predictive biomarker of acute kidney injury in critically ill patients

INTRODUCTION

During critical illness, oliguria is often used as a biomarker of acute kidney injury (AKI). However, its relationship with the subsequent development of AKI has not been prospectively evaluated.

METHODS

We documented urine output and daily serum creatinine concentration in patients admitted for more than 24 hours in seven intensive care units (ICUs) from six countries over a period of two to four weeks. Oliguria was defined by a urine output < 0.5 ml/kg/hr. Data were collected until the occurrence of creatinine-defined AKI (AKI-Cr), designated by RIFLE-Injury class or greater using creatinine criteria (RIFLE-I[Cr]), or until ICU discharge. Episodes of oliguria were classified by longest duration of consecutive oliguria during each day were correlated with new AKI-Cr the next day, examining cut-offs for oliguria of greater than 1,2,3,4,5,6, or 12 hr duration,

RESULTS

We studied 239 patients during 723 days. Overall, 32 patients had AKI on ICU admission, while in 23, AKI-Cr developed in ICU. Oliguria of greater than one hour was significantly associated with AKI-Cr the next day. On receiver-operator characteristic area under the curve (ROCAUC) analysis, oliguria showed fair predictive ability for AKI-Cr (ROCAUC = 0.75; CI:0.64-0.85). The presence of 4 hrs or more oliguria provided the best discrimination (sensitivity 52% (0.31-0.73%), specificity 86% (0.84-0.89%), positive likelihood ratio 3.8 (2.2-5.6), P < 0.0001) with negative predictive value of 98% (0.97-0.99). Oliguria preceding AKI-Cr was more likely to be associated with lower blood pressure, higher heart rate and use of vasopressors or inotropes and was more likely to prompt clinical intervention. However, only 30 of 487 individual episodes of oliguria preceded the new occurrence of AKI-Cr the next day.

CONCLUSIONS

Oliguria was significantly associated with the occurrence of new AKI-Cr, however oliguria occurred frequently compared to the small number of patients (~10%) developing AKI-Cr in the ICU, so that most episodes of oliguria were not followed by renal injury. Consequently, the occurrence of short periods (1-6 hr) of oliguria lacked utility in discriminating patients with incipient AKI-Cr (positive likelihood ratios of 2-4, with > 10 considered indicative of a useful screening test). However, oliguria accompanied by hemodynamic compromise or increasing vasopressor dose may represent a clinically useful trigger for other early biomarkers of renal injury.

Monitoring of plasma creatinine and urinary γ-glutamyl transpeptidase improves detection of acute kidney injury by more than 20%

OBJECTIVES

We sought to determine how early we can detect acute kidney injury inpatients at intensive care unit admission by combining the use of plasma creatinine and urinary γ-glutamyl transpeptidase.

DESIGN

Prospective study including development (n = 100) and validation (n = 56) cohorts.

SETTINGS

Intensive care unit of a university hospital.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

To determine acute kidney injury, we subtracted measured creatinine clearance from theoretical creatinine clearance with a 25% reduction signifying acute kidney injury. Its incidence in 100 consecutive patients was 36%. An indexed urinary γ-glutamyl transpeptidase-to-urinary creatinine ratio was significantly increased in the patients with acute kidney injury and did not correlate with plasma creatinine (p = .3). Using a predefined threshold of indexed urinary γ-glutamyl transpeptidase-to-urinary creatinine ratio (>12.4 units/mmol) and plasma creatinine (>89 μmol/L), acute kidney injury detection was significantly improved, making it possible to detect 22 (22%) additional patients with acute kidney injury. This finding was confirmed in the validation group. The rates of false-positive results were 30% and 19% in the data development and internal validation cohorts, respectively.

CONCLUSIONS

The use of low-cost, widely available markers (creatinine and urinary γ-glutamyl transpeptidase) increases the detection of acute kidney injury. Further studies are needed to determine the impact on outcome with the use of these biomarkers.

Fluid balance and acute kidney injury

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

Postoperative acute renal failure in patients with gynecologic malignancies: analysis of 10 cases and review of the literature

OBJECTIVE

Postoperative acute renal failure (PO-ARF) is an important cause of mortality among surgical patients. Although there have been many reports on PO-ARF after cardiac surgery and liver transplantation, less is known about the risk of PO-ARF after gynecologic operations. We aimed to investigate the risk of PO-ARF on gynecologic malignancy operations.

METHODS

1,155 patients' medical charts were reviewed who underwent therapeutic surgery for gynecologic malignancies from January 1, 2005 to December 31, 2007, at the Asan Medical Center, Seoul, Korea.

RESULTS

Of these, 10 patients, comprising 0.89% of those who underwent radical hysterectomies and 0.86% of those who underwent debulking operations, were diagnosed with PO-ARF. Their mean age was 61.9+/-10.1 years. Five patients had preoperative risk factors. Mean operating time was 360.8+/-96.2 minutes. Five patients experienced intra-operative hypotension and all patients were given blood transfusions during surgery. Eight patients underwent hemodialysis, with two continuing on dialysis to date. Only two patients fully recovered.

CONCLUSION

Patients undergoing surgery for gynecologic malignancies may be at high risk for PO-ARF, because of old age, long operation times, and profuse bleeding. It is necessary to monitor these patients for postoperative renal function and urine output. If a postoperative oliguric state is detected, aggressive volume expansion should be started immediately, followed by hemodialysis.

Monitoring Hepatic and Renal Function

Liver disease represents a serious risk factor for patients requiring anesthesia and surgery. Even subclinical liver disease increases perioperative morbidity and mortality. Perioperative renal dysfunction and failure have similar implications. Thus, detection of early hepatic and renal dysfunction and monitoring of their progress is essential. This article discusses methods for monitoring hepatic and renal function in patients who have high risk for liver or renal injury in the perioperative period.

Acute renal failure in hospitalized patients: part II

BACKGROUND

Acute renal failure (ARF) is a common condition in hospitalized patients. Research has been unable to identify the optimal target for therapeutic intervention; hence, effective prevention of and/or treatment for ARF remain elusive.

OBJECTIVE

To examine the usefulness of current and potential pharmacologic treatments in seriously ill, hospitalized patients.

DATA SOURCES

A MEDLINE search (1996-June 2002) was conducted using the search terms kidney (drug effects) and acute kidney failure (drug therapy). Bibliographies of selected articles were also examined to include all relevant investigations.

STUDY SELECTION AND DATA EXTRACTION

Review articles, meta-analyses, and clinical trials describing prevention of and treatment for hospital-acquired ARF were identified. Results from prospective, controlled trials were given priority when available.

CONCLUSIONS

Appropriate management of ARF includes prospective identification of at-risk patients, fluid administration, and optimal hemodynamic support. Drug treatments, including low-dose dopamine and diuretics, have demonstrated extremely limited benefits and have not been shown to improve patient outcome. Experimental agents influence cellular processes of renal dysfunction and recovery; unfortunately, relatively few drugs show promise for the future.