Machine-learning model for predicting oliguria in critically ill patients

This retrospective cohort study aimed to develop and evaluate a machine-learning algorithm for predicting oliguria, a sign of acute kidney injury (AKI). To this end, electronic health record data from consecutive patients admitted to the intensive care unit (ICU) between 2010 and 2019 were used and oliguria was defined as a urine output of less than 0.5 mL/kg/h. Furthermore, a light-gradient boosting machine was used for model development. Among the 9,241 patients who participated in the study, the proportions of patients with urine output < 0.5 mL/kg/h for 6 h and with AKI during the ICU stay were 27.4% and 30.2%, respectively. The area under the curve (AUC) values provided by the prediction algorithm for the onset of oliguria at 6 h and 72 h using 28 clinically relevant variables were 0.964 (a 95% confidence interval (CI) of 0.963-0.965) and 0.916 (a 95% CI of 0.914-0.918), respectively. The Shapley additive explanation analysis for predicting oliguria at 6 h identified urine values, severity scores, serum creatinine, oxygen partial pressure, fibrinogen/fibrin degradation products, interleukin-6, and peripheral temperature as important variables. Thus, this study demonstrates that a machine-learning algorithm can accurately predict oliguria onset in ICU patients, suggesting the importance of oliguria in the early diagnosis and optimal management of AKI.

Early detection of oliguric events in critically ill patients in the ICU with a novel continuous urine flow measurement device: results of an initial validation study

OBJECTIVES

Urine output is used to evaluate fluid status and is an important marker for acute kidney injury (AKI). Our primary aim was to validate a new automatic urine output monitoring device by comparison to the current practice - the standard urometer.

METHODS

We conducted a prospective observational study in three ICUs. Urine flow measurements by Serenno Medical Automatic urine output measuring device (Serenno Medical, Yokneam, Israel) were compared to standard urometer readings taken automatically at 5-minutes intervals by a camera, and to hourly urometer readings by the nurses, both over 1 to 7 days. Our primary outcome was the difference between urine flow assessed by the Serenno device and reference camera-derived measurements (Camera). Our secondary outcome was the difference between urine flow assessed by the Serenno device and hourly nursing assessments (Nurse), and detection of oliguria.

RESULTS

Thirty-seven patients completed the study, with 1,306 h of recording and a median of 25 measurement hours per patient. Bland and Altman analysis comparing the study device to camera measurements demonstrated good agreement, with a bias of -0.4 ml/h and 95% confidence intervals ranging from - 28 to 27ml/h. Concordance was 92%. The correlation between Camera and hourly nursing assessment of urine output was distinctly worse with a bias of 7.2 ml and limits of agreement extending from - 75 to + 107 ml. Severe oliguria (urine output < 0.3 ml/kg/h) lasting 2 h or more was common and observed in 8 (21%) of patients. Among the severe oliguric events lasting more than 3 consecutive hours, 6 (41%) were not detected or documented by the nursing staff. There were no device-related complications.

CONCLUSION

The Serenno Medical Automatic urine output measuring device required minimal supervision, little ICU nursing staff attention, and is sufficiently accurate and precise. In addition to providing continuous assessments of urine output, it was considerably more accurate than hourly nursing assessments.

External validation of a deep-learning model to predict severe acute kidney injury based on urine output changes in critically ill patients

OBJECTIVES

The purpose of this study was to externally validate algorithms (previously developed and trained in two United States populations) aimed at early detection of severe oliguric AKI (stage 2/3 KDIGO) in intensive care units patients.

METHODS

The independent cohort was composed of 10'596 patients from the university hospital ICU of Amsterdam (the "AmsterdamUMC database") admitted to their intensive care units. In this cohort, we analysed the accuracy of algorithms based on logistic regression and deep learning methods. The accuracy of investigated algorithms had previously been tested with electronic intensive care unit (eICU) and MIMIC-III patients.

RESULTS

The deep learning model had an area under the ROC curve (AUC) of 0,907 (± 0,007SE) with a sensitivity and specificity of 80% and 89%, respectively, for identifying oliguric AKI episodes. Logistic regression models had an AUC of 0,877 (± 0,005SE) with a sensitivity and specificity of 80% and 81%, respectively. These results were comparable to those obtained in the two US populations upon which the algorithms were previously developed and trained.

CONCLUSION

External validation on the European sample confirmed the accuracy of the algorithms, previously investigated in the US population. The models show high accuracy in both the European and the American databases even though the two cohorts differ in a range of demographic and clinical characteristics, further underlining the validity and the generalizability of the two analytical approaches.

Association of Oliguria With Acute Kidney Injury Diagnosis, Severity Assessment, and Mortality Among Patients With Critical Illness

Importance

The current definition and staging of acute kidney injury (AKI) considers alterations in serum creatinine (sCr) level and urinary output (UO). However, the relevance of oliguria-based criteria is disputed.

Objective

To determine the contribution of oliguria, as defined by the Kidney Disease: Improving Global Outcomes (KDIGO) criteria, to AKI diagnosis, severity assessment, and short- and long-term outcomes.

Design, Setting, and Participants

This cohort study included adult patients admitted to a multidisciplinary intensive care unit from January 1, 2010, to June 15, 2020. Patients receiving long-term dialysis and those who declined consent were excluded. Daily sCr level and hourly UO measurements along with sociodemographic characteristics and severity scores were extracted from electronic medical records. Long-term mortality was assessed by cross-referencing the database with the Swiss national death registry. The onset and severity of AKI according to the KDIGO classification was determined using UO and sCr criteria separately, and their agreement was assessed.

Main Outcomes and Measures

Using a multivariable model accounting for baseline characteristics, severity scores, and sCr stages, the association of UO criteria with 90-day mortality was evaluated. Sensitivity analyses were conducted to assess how missing sCr, body weight, and UO values, as well as different sCr baseline definitions and imputations methods, would affect the main results.

Results

Among the 15 620 patients included in the study (10 330 men [66.1%] with a median age of 65 [IQR, 53-75] years, a median Simplified Acute Physiology Score II score of 40.0 [IQR, 30.0-53.0], and a median follow-up of 67.0 [IQR, 34.0-100.0] months), 12 143 (77.7%) fulfilled AKI criteria. Serum creatinine and UO criteria had poor agreement on AKI diagnosis and staging (Cohen weighted κ, 0.36; 95% CI, 0.35-0.37; P < .001). Compared with the isolated use of sCr criteria, consideration of UO criteria enabled identification of AKI in 5630 patients (36.0%). Those patients had a higher 90-day mortality than patients without AKI (724 of 5608 [12.9%] vs 288 of 3462 [8.3%]; P < .001). On multivariable analysis accounting for sCr stage, comorbidities, and illness severity, UO stages 2 and 3 were associated with a higher 90-day mortality (odds ratios, 2.4 [95% CI, 1.6-3.8; P < .001] and 6.2 [95% CI, 3.7-10.5; P < .001], respectively). These results remained significant in all sensitivity analyses.

Conclusions and Relevance

The findings of this cohort study suggest that oliguria lasting more than 12 hours (KDIGO stage 2 or 3) has major AKI diagnostic implications and is associated with outcomes irrespective of sCr elevations.

Acute kidney injury after liver surgery: does postoperative urine output correlate with postoperative serum creatinine?

BACKGROUND

Acute kidney injury (AKI) after hepatectomy occurs in around 10% of cases. AKI is often defined based only on postoperative serum creatinine increase. This study aimed to assess if postoperative urine output (UO) correlated with serum creatinine after hepatectomy.

METHODS

All consecutive hepatectomy patients (2010-2016) were assessed. AKI was defined according to KDIGO criteria: serum creatinine increase ≥26.5 μmol/l, creatinine increase ≥1.5x baseline creatinine, or postoperative oliguria. Oliguria was defined as daily mean UO <0.5 mL/kg/h. AKI was subdivided into creatinine-based or oliguria-based AKI according to the defining criterion.

RESULTS

Out of 285 patients, AKI was observed in 79 cases (28%). Creatinine-based AKI occurred in 25 patients (9%) and oliguria-based only AKI in 54 patients (19%). Ten patients fulfilled both criteria (4%). Postoperative UO correlated poorly with postoperative serum creatinine level in both whole cohort (rho = -0.34, p <0.001) and AKI subgroup (rho = -0.189, p = 0.124). No association was found between postoperative oliguria and postoperative serum creatinine increase (HR = 0.5, 95%CI: 0.2-1.9, p = 0.341). On multivariable analysis, operation duration >360 minutes was the only predictor of creatinine increase (HR = 3.6, 95%CI: 1.1-11.4, p = 0.032).

CONCLUSION

Postoperative UO showed poor correlation with postoperative serum creatinine both in all patients and AKI patients. Surgery duration >360 minutes appeared as the only independent predictor of postoperative serum creatinine increase.

Improving the Clinical Skills Performance of Graduating Medical Students Using "WISE OnCall," a Multimedia Educational Module

INTRODUCTION

"Transitions to residency" programs are designed to maximize quality and safety of patient care, as medical students become residents. However, best instructional or readiness assessment practices are not yet established. We sought to study the impact of a screen-based interactive curriculum designed to prepare interns to address common clinical coverage issues (WISE OnCall) on the clinical skills demonstrated in simulation and hypothesize that performance would improve after completing the module.

METHODS

Senior medical students were recruited to participate in this single group prestudy/poststudy. Students responded to a call from a standardized nurse (SN) and assessed a standardized patient (SP) with low urine output, interacted with a 45-minute WISE OnCall module on the assessment and management of oliguria, and then evaluated a different SP with low urine output of a different underlying cause. Standardized patients assessed clinical skills with a 37-item, behaviorally anchored checklist measuring clinical skills (intraclass correlation coefficient [ICC], 0.55-0.81). Standardized nurses rated care quality and safety and collaboration and interprofessional communication using a 33-item literature-based, anchored checklist (ICC, 0.47-0.52). Standardized patient and SN ratings of the same student performance were correlated (r, 0.37-0.62; P < 0.01). Physicians assessed clinical reasoning quality based on the students' patient encounter note (ICC, 0.55-0.68), ratings that did not correlate with SP and SN ratings. We compared pre-post clinical skills performance and clinical reasoning. Fifty-two medical students (31%) completed this institutional review board -approved study.

RESULTS

Performance as measured by the SPs, SNs, and the postencounter note all showed improvement with mostly moderate to large effect sizes (range of Cohen's d, 0.30-1.88; P < 0.05) after completion of the online module. Unexpectedly, professionalism as rated by the SP was poorer after the module (Cohen's d, -0.93; P = 0.000).

DISCUSSION

A brief computer-based educational intervention significantly improved graduating medical students' clinical skills needed to be ready for residency.

Acute kidney injury and fluid overload in infants and children after cardiac surgery

Acute kidney injury is a common and serious complication after congenital heart surgery, particularly among infants. This comorbidity has been independently associated with adverse outcomes including an increase in mortality. Postoperative acute kidney injury has a complex pathophysiology with many risk factors, and therefore no single medication or therapy has been demonstrated to be effective for treatment or prevention. However, it has been established that the associated fluid overload is one of the major determinants of morbidity, particularly in infants after cardiac surgery. Therefore, in the absence of an intervention to prevent acute kidney injury, much of the effort to improve outcomes has focused on treating and preventing fluid overload. Early renal replacement therapy, often in the form of peritoneal dialysis, has been shown to be safe and beneficial in infants with oliguria after heart surgery. As understanding of the pathophysiology of acute kidney injury and the ability to confidently diagnose it earlier continues to evolve, it is likely that novel preventative and therapeutic interventions will be available in the future.

Increased urinary neutrophil gelatinase-associated lipocalin in very-low-birth-weight infants with oliguria and normal serum creatinine

BACKGROUND

In infants, oliguria is defined as a urine output of <1.5 mL/kg/h. The aim of our study was to assess the impact of oliguria on urinary neutrophil gelatinase-associated lipocalin (NGAL) and serum cystatin C (CysC) levels in very-low-birth-weight infants (VLBWIs) with a normal serum creatinine (Cr) level.

METHODS

Fifty-seven VLBWIs were enrolled in the study. Urinary NGAL, serum CysC and Cr levels and urinary NGAL/Cr ratios were measured. Infants with Apgar scores of >5 at 5 min and/or a serum Cr level of >1.5 mg/dL or those treated for patent ductus arteriosus were excluded. In case of antibiotic treatment, blood and urine samples were collected at ≥48 h after discontinuation of antibiotic treatment.

RESULTS

There was a significant difference in gestational age between infants with oliguric episodes during hospitalization and those without, but not in birth weight, perinatal or postnatal factors. Gestational age was negatively correlated with urinary NGAL and serum CysC levels and urinary NGAL/Cr ratio (p < 0.05), whereas postnatal age was negatively correlated with serum Cr level and urinary NGAL/Cr ratio (p < 0.05). Of the 117 urine and blood samples collected, 25 (21.4%) were obtained from neonates with oliguric episodes. After adjusting for gestational age and postnatal age, comparison of samples collected in infants with and without oliguric episodes revealed significant differences in the mean level of urinary NGAL and in the urinary NGAL/Cr ratio, but not in mean serum CysC or serum Cr levels. The urinary NGAL level [area under the curve (AUC) 0.886, 95% confidence interval (CI) 0.814-0.937] and urinary NGAL/Cr ratio (AUC 0.853, 95% CI 0.775-0.911) showed significantly greater discrimination for oliguria than serum CysC (AUC 0.610, 95% CI: 0.515-0.699) or serum Cr (AUC 0.747, 95%CI 0.659-0.823) levels.

CONCLUSIONS

Urinary NGAL level and urinary NGAL/Cr ratio were more sensitive markers for the presence of oliguria in VLBWIs with normal serum Cr levels than serum CysC level.

[Volume assessment in the acute heart and renal failure]

Acute kidney injury (AKI) is an important clinical issue, especially in the setting of critical care. It has been shown in multiple studies to be a key independent risk factor for mortality, even after adjustment for demographics and severity of illness. There is wide agreement that a generally applicable classification system is required for AKI which helps to standardize estimation of severity of renal disfunction and to predict outcome associated with this condition. That's how RIFLE (Risk-Injury-Failure-Loss-End-stage renal disease), and AKIN (Acute Kidney Injury Network) classifications for AKI were found in 2004 and 2007, respectively. In the clinical setting of heart failure, a positive fluid balance (often expressed in the literature as weight gain) is used by disease management programs as a marker of heart failure decompensation. Oliguria is defined as urine output less than 0,3 ml/kg/h for at least 24 h. Since any delay in treatment can lead to a dangerous progression of the AKI, early recognition of oliguria appears to be crucial. Critically ill patients with oliguric AKI are at increased risk for fluid imbalance due to widespread systemic inflammation, reduced plasma oncotic pressure and increased capillary leak. These patients are particulary at risk of fluid overload and therefore restrictive strategy of fluid administration should be used. Objective, rapid and accurate volume assessment is important in undiagnosed patients presenting with critical illness, as errors may result in interventions with fatal outcomes. The historical tools such as physical exam, and chest radiography suffer from significant limitations. As gold standard, radioisolopic measurement of volume is impractical in the acute care enviroment. Newer technologies offer the promise of both rapid and accurate bedside estimation of volume status with the potential to improve clinical outcomes. Blood assessment with bioimpendance vector analysis, and bedside ultrasound seem to be promising technologies for this need.

Hemodynamic and related challenges: monitoring and regulation in the postoperative period

The clinician caring for patients in the immediate postoperative period must maintain a high index of suspicion for the development of complications. Evolving illness manifests itself throughout the continuum of care and must be recognized and aggressively managed to ensure optimal outcome. This article discusses common hemodynamic problems encountered in the postanesthesia care unit. These problems are presented in a clinical framework that is familiar to experienced practitioners and recognizable to trainees. This article reviews of these common problems including relevant physiologic principles; effects on hemodynamics; and a logical approach to evaluation, monitoring, and management of a complex postoperative patient.

Oliguria, creatinine and other biomarkers of acute kidney injury

Acute kidney injury (AKI) and fluid overload are conditions that require an early diagnosis and a prompt intervention. The recognition of these pathologic conditions is possible in the early stages if specific signs and symptoms are taken into account. Among them, oliguria represents an important sign. Reduced urine output for a certain number of hours may be an important sign of kidney dysfunction. This must be evaluated in conjunction with other factors such as hydration status and use of drugs. At the same time, traditional markers of kidney function such as urea nitrogen and creatinine must be evaluated in light of a possible altered balance. Increased levels may be due to reduced kidney function but also increased generation or altered solute distribution space due to non-optimal hydration status. Finally, novel biomarkers for renal tissue damage are becoming popular. Molecules such as NGAL or cystatin C may become altered well before creatinine or oliguria signal a condition of reduced kidney function. Here, the difference between insult and dysfunction becomes evident. Novel biomarkers seem to enable the clinician to make early diagnosis of kidney damage, distinguishing between AKI and acute kidney failure. Reduced glomerular filtration rate is, in fact, a late event in the continuum of the AKI syndrome.

How to ensure patient observations lead to effective management of oliguria

Fluid balance is essential for normal functioning of the body. Oliguria (poor urine output) is usually associated with low circulatory blood volume (hypovolaemia), and can be a sign that a patient is acutely ill and deteriorating. Early warning scoring systems should identify the condition so that appropriate interventions can be undertaken to restore urine output and protect renal function.

A device for automatically measuring and supervising the critical care patient's urine output

Critical care units are equipped with commercial monitoring devices capable of sensing patients’ physiological parameters and supervising the achievement of the established therapeutic goals. This avoids human errors in this task and considerably decreases the workload of the healthcare staff. However, at present there still is a very relevant physiological parameter that is measured and supervised manually by the critical care units’ healthcare staff: urine output. This paper presents a patent-pending device capable of automatically recording and supervising the urine output of a critical care patient. A high precision scale is used to measure the weight of a commercial urine meter. On the scale’s pan there is a support frame made up of Bosch profiles that isolates the scale from force transmission from the patient’s bed, and guarantees that the urine flows properly through the urine meter input tube. The scale’s readings are sent to a PC via Bluetooth where an application supervises the achievement of the therapeutic goals. The device is currently undergoing tests at a research unit associated with the University Hospital of Getafe in Spain.

Delayed hypercalcemia after non-oliguric acute renal failure associated with rhabdomyolysis

Alterations in the calcium metabolism are a characteristic paraclinical finding in patients with oliguric acute renal failure associated with rhabdomyolysis. A 20-year-old male operated on under general anesthesia developed non-oliguric acute renal failure due to malignant hyperthermia with rhabdomyolysis (urine myoglobin greater than 20,000 nmol/l; reference range less than 0.85 nmol/l). On the 20th postoperative day hypercalcemia was found, reaching a maximum serum level of 3.74 mmol/l (reference range 2.18-2.65 mmol/l) on the 27th postoperative day. Delayed hypercalcemia in non-oliguric acute renal failure associated with rhabdomyolysis has not been reported previously. This case suggests that prolonged control of the serum calcium level should be performed in patients with rhabdomyolysis, even in the absence of oliguria.

Oxalosis presenting as early renal allograft failure

Hyperoxaluria can result in the deposition of oxalate in bones, arteries, eyes, heart, nerves, kidneys and other structures when there is a reduction in glomerular filtration rate. Liver and kidney transplantation is curative for patients with Type I primary hyperoxaluria. Here we report a case of recurrent oxalosis in a post-transplant kidney with early graft failure in an adult male.

Prognostic factors associated with severe leptospirosis

Leptospirosis is an anthropozoonosis caused by Leptospira interrogans. It occurs worldwide and is endemic in French Polynesia. Leptospirosis is associated with a large variety of clinical symptoms. Most infections caused by leptospires are either sub-clinical or of very mild severity, but 5-10% of infections result in multiple organ damage, including kidney, liver and lung lesions. Among 71 patients hospitalised in Papeete for severe leptospirosis during a period of 2 years, the main risk-factors for a severe outcome were hypotension, oliguria and an abnormal chest auscultation at the first physical examination. Survival depends on rapid diagnosis and early appropriate management. Well-defined criteria may help physicians to improve the timely treatment of high-risk patients.

[Clinical reasoning and decision-making in practice. A patient with oliguria following prostatectomy]

A 70-year-old man with clinically localised prostate carcinoma underwent extraperitoneal endoscopic radical prostatectomy. His medical history revealed hypertension, renal colic, hypogonadotropic hypogonadism and recurrent deep venous thrombosis in the legs. The operation was uneventful with 500 ml blood loss and no periods ofhypotension. The patient developed oliguria within 12 h after surgery. A hypovolemic state was initially suggested to explain the oliguria and increasing amounts of intravenous fluids were administered. The oliguria persisted, however, and the patient did not respond to a diuretic. There was no fluid loss in the drain. Blood pressure, pulse and temperature were normal. Peritonitis and bowel perforation were excluded. Ultrasound examination of the bladder and kidneys revealed an empty bladder and no dilatation of the upper urinary tract, which excluded a post-renal obstruction. The clinical situation deteriorated within hours as the patient developed anuria, bowel distension, metabolic acidosis with progressive renal failure and signs of respiratory distress for which mechanical ventilation was needed. A chest X-ray prior to intubation did not show pneumonia or signs indicating pulmonary embolism. CT of the abdomen was performed to evaluate urinary leakage but revealed no fluid collection or urinoma. Thus pre- and post-renal causes of oliguria were excluded. In view of the systemic symptoms, intra-abdominal pressure was measured using a bladder catheter; it varied between 25 and 35 cm water. Together with the clinical situation, a diagnosis of abdominal compartment syndrome was made and coeliotomy was performed immediately. Within 10 min after decompression of the peritoneal cavity, diuresis started spontaneously. Renal function was restored to preoperative levels in 3 weeks. Abdominal compartment syndrome is a potentially life-threatening cause of anuria. The syndrome should be part of the differential diagnosis for patients with postoperative anuria, including those who underwent extraperitoneal minimally invasive procedures.

Oliguria, Volume Overload, Na+ Balance, and Diuretics

This article discusses the pathophysiology and treatment of common fluid and electrolyte disorders in the ICU. The presence of oliguria should alert the intensivist to identify the underlying cause rather than to resort reflexively to measures, such as diuretics or dopamine, to establish urine flow. Hypo- and hypernatremia, which are exceedingly commonly in the ICU setting, also are discussed using a pathophysiologic approach.

Voiding dysfunction in pediatric patients

The goals of this study were to describe the pattern of voiding disorders in children in our community, to describe clinical criteria for making the specific diagnoses, and to comment on management. The medical records of 226 children referred because of voiding dysfunction or urinary tract infections (UTI) were evaluated. Children with normal voiding patterns when uninfected, with monosymptomatic nocturnal enuresis, and with known neurologic or anatomic abnormalities were excluded. Detrusor instability, an abnormal voiding pattern characterized by urgency with or without frequency, was the diagnosis in 175 of the 226 children. Children with detrusor instability who used various posturing maneuvers to avoid urinary incontinence had a significantly higher incidence of UTIs than those who did not attempt to obstruct urine outflow. Detrusor instability appeared to be secondary to constipation in 19 of the children. The other diagnoses were extraordinary daytime urinary frequency, infrequent voiding, monosymptomatic daytime wetting, transient voiding dysfunction, giggle incontinence, dysfunctional voiding, and unexplained dysuria. It is concluded that children with detrusor instability who use posturing maneuvers to avoid incontinence are at high risk for recurrent UTIs. Constipation is 1 cause of detrusor instability. Dysfunctional voiding, the form of voiding dysfunction most likely to result in renal damage, was present in only 2 of 226 children seen for voiding disorders.

Complication of oliguric acute renal failure in patients treated with low-molecular weight dextran

Acute renal failure (ARF) is a well-documented but infrequent complication in patients treated with low-molecular weight dextran (LMWD). We herein report 3 cases of oliguric ARF following the administration of dextran-40. One case developed ARF totally after 1.200 g of LMWD administration. In contrast, two cases having increased serum creatinine developed oliguria despite the acceptable therapeutic doses (totally 450 and 650 g). Contrast media was also co-administered in these patients. Plasma exchange (PE), double filtration plasmapheresis (DFPP), or continuous hemodiafiltration (CHDF) but not hemodialysis (HD) reduced circulating dextran concentrations by 35-44% during a single session. All patients completely recovered from ARF by 14-32 days after the treatment. Our cases suggested that radiocontrast could predispose to the development of LMWD-induced ARF especially in patients having pre-existing renal dysfunction. In addition, PE, DFPP and CHDF afforded a beneficial effect for removing accumulated LMWD from the circulation.

Haemodynamic, invasive and echocardiographic monitoring in the hypertensive parturient

AIM

To determine the clinical usefulness of invasive and non-invasive haemodynamic assessment in pre-eclampsia.

METHOD

A systematic review of the literature was undertaken, using a MEDLINE electronic search using a combination of MESH headings and textwords. Over 1500 abstracts were perused; we obtained 156 full papers that were related to the subject matter. Of the full papers, 55 yielded relevant information. Hand-searching the reference lists of the retrieved papers completed the search.

RESULTS

There are no data from randomized controlled clinical trials illustrating the clinical usefulness of pulmonary artery catheters or echocardiographic techniques in hypertensive pregnancy. There are a wealth of data illustrating the haemodynamic profiles of both untreated and treated pre-eclamptic women. Data are also available comparing right heart and left heart filling pressures, demonstrating a relatively poor correlation between the two values. The clinical impact of either measurement is unclear. Data are available illustrating the correlation between echocardiographic techniques and pulmonary artery catheterization.

Care of the critically ill parturient: oliguria and renal failure

The incidence of acute renal failure in pregnancy has decreased. This decrease is less marked in developing countries in which resources are more scarce. The clinical diagnosis of acute renal failure is crude due to the variability of clinical signs and the late occurrence of basic biochemical abnormalities. Obstetric and gynaecological diseases are found among the traditional pre-renal, intra-renal and post-renal causes of acute renal failure. The cornerstone of management is the identification of high-risk cases and the prevention of acute renal failure by maintaining intravascular volume. The evidence for the efficacy of other prophylactic medical interventions, such as the use of loop diuretics, mannitol, low-dose dopamine and others, is poor. Management of established acute renal failure includes restoration of intravascular volume, treatment of any reversible causes, especially pregnancy complications such as pre-eclampsia, strict fluid balance and correction of any electrolyte abnormality or metabolic acidosis. Dialysis is a supportive measure until the kidneys recover.

Changes in expression of sodium cotransporters and aquaporin-2 during ischemia-reperfusion injury in rabbit kidney

Ischemic renal injury is associated with defects in transport functions of the proximal tubules and urinary concentration ability. To determine whether alterations in expression of various transporter genes contribute to an impairment in renal functions, the expression of various solute transport genes was analyzed in renal cortex and medulla of rabbits with ischemic acute renal failure. Rabbits were subjected to 60 min of renal pedicle clamping followed by 24, 48, or 72 h of reperfusion. Urine volume and glomerular filtration rate were markedly decreased, which were accompanied by an increase in serum creatinine level and fraction Na+ excretion. Glucosuria and phosphaturia were evident during reperfusion periods. These alterations in renal functions were persisted to 72 h after reperfusion. The Na+-dependent uptakes of glucose and phosphate by brush border membrane vesicles were inhibited by 24 h of reperfusion. mRNA levels for Na+-glucose, Na+-phosphate, and Na+-succinate cotransporter analyzed by RT-PCR were not changed by 60 min of ischemia alone, but were significantly reduced by 24 h of reperfusion. mRNA levels for apical Na+-K+-2Cl- cotransporter, NaCl cotransporter, and turea transporter in the medulla were not changed during reperfusion. Protein levels for AQP2 in the medulla, but not AQP1 in the cortex, analyzed by Western blot were significantly reduced at 24 h after reperfusion. These results suggest that reductions in expression of Na+-cotransporter genes in the proximal tubules may be important factors in the impairment in Na+-dependent reabsorption of solutes and that decrease in AQP2 protein may be involved in defect in urinary concentration ability in rabbits with ischemic acute renal failure.

Oliguria in the ICU. Systematic approach to diagnosis and treatment

Perioperative oliguria is common but rarely implies acute renal failure. We should interpret oliguria as a sign of intravascular hypovolemia and treat it as prerenal until proven otherwise. On the other hand, the absence of oliguria does not exclude acute renal failure. The most reliable clinical indicator of progressive renal dysfunction is a serial decline in creatinine clearance estimation, a measure of glomerular filtration rate.

[Acute oliguric kidney failure secondary to acetic acid poisoning]

A case of acute oliguric renal failure secondary to poisoning by acetic acid (AA) is described. The patient presents caustic damage in the mucous digestive, myoglobinuria, thrombopaenia, elevation of the enzymes of damage tissular and acute hepatic affectation. To the entrance, the patient show a good hemodynamic state and the hematologic study discarded the hemolysis presence, what allowed to establish the direct action of the AA on the kidney like cause of the oliguric failure renal next to the tubular toxic effect of the myoglobin. The oral ingesta of AA is an unusual fact and its relationship with the acute renal failure it has not been communicated previously in our country.

Oliguria

Oliguria is a common finding in adult patients in hospitals and carries a significant morbidity if its origin is not corrected promptly. The differential diagnosis of oliguria is broad; thus a solid knowledge of its causes is required for advanced practice nurses to diagnose oliguria correctly.

The reduced urinary output after spinal cord injury: a review

Oliguria in patients following spinal cord injury was first mentioned in 1649, but has since been referred to only occasionally. The work detailed here was completed 30 years ago but is reported because of the lack of any comparable study and because suitable patients are not now readily available. A total of 27 water load tests were carried out on 20 patients. The test included measurement of serum osmolality to confirm absorption of ingested water. Impaired response to the water load was obtained in 17 tests: 12/13 between 1 and 5 days after onset of the cord lesion and 5/14 more than 2 weeks after injury. The possibilities that oliguria was due to dehydration, failure to absorb ingested water, hypotension or renal failure are discounted. In the first few days after injury, oliguria may be due to release of antidiuretic hormone as part of the metabolic response to trauma. The impaired response seen later is discussed in relation to possible neural and hormonal mechanisms. There is a need for further study of factors influencing water excretion in tetraplegic and paraplegic patients.

A study on oliguric standard in the elderly

Water deprivation test was done in 44 healthy elderly persons, 26 were male, and 18 were female. They were deprived of the intake of water for 25 hours. The results showed that the maximal renal concentration function both in the elderly males and females was 887 +/- 91 mmol/L and 888 +/- 127 mmol/L respectively. The renal excretion of waste products in 24 hours both in the elderly males and females was 815 + 170 mmol/d and 620 + 132 mmol/d respectively. On the basis of point estimation, the minimal essential urine volume per day in the elderly males and females was 926 ml/d and 708 ml/d respectively, if the daily urine volume of the elderly is less than this level, then, the metabolic products generated per day can not be excreted by the kidney, and it would result in disorders of internal environment. Therefore, the oliguric standard in elderly males and females must be less than 926 ml/d and 708 ml per day respectively.

Evaluation of diagnostic criteria of acute renal failure in premature infants

A prospective study was performed to investigate the validity of renal failure index (RFI) or fractional excretion of sodium (FENa) in preterm infants. The subjects were 128 newborn infants, 72 with oliguria and 56 without renal dysfunction (control). Oliguric infants were divided into two categories: acute renal failure (ARF) and prerenal failure (PRF), according to creatinine clearance (Ccr). Furthermore, all subjects were divided into four groups according to gestation, that is, 38 infants with gestational age of 25-28 weeks (group 1), 28 with 29-30 weeks (group 2), 38 with 31-36 weeks (group 3) and 24 of > 37 weeks (group 4). As a result, differentiation between ARF and PRF was valid when the RFI or FENa was used in infants of > 29 weeks gestation (groups 2, 3 and 4). Although infants of > 31 weeks gestation (groups 3 and 4) who present with an RFI > 3 or an FENa > 3% may be diagnosed as having ARF, infants in group 2 with an RFI of > 8 or an FENa of > 6% may be diagnosed as having ARF. For the infants in group 1, the application of RFI or FENa for diagnosis of ARF may be limited because of some overlap among the groups.

Serial MR intensity changes of the posterior pituitary in a patient with anorexia nervosa, high serum ADH, and oliguria

The posterior pituitary high signal (PPHS) seen on MRI of the sella in normal individuals probably reflects antidiuretic hormone (ADH) granules stored in the posterior pituitary lobe (PPL). We present a case with anorexia nervosa, high serum ADH, and oliguria who underwent three cerebral MR studies over the course of treatment. The first MR examination showed absence of PPHS and early enhancement of the PPL on dynamic MRI. In subsequent MR examinations PPHS became evident in concomitance with clinical improvement. This case suggests that PPHS changes may reflect reaccumulation of ADH granules and that dynamic MR of the PPL may be useful for assessing the vascularity of the PPL and/or the reversibility of its function.

Low-dose dopamine in critically ill oliguric patients: the influence of the renin-angiotensin system

OBJECTIVE

To assess the effect of low-dose dopamine on urine output and natriuresis in critically ill oliguric patients and the relationship of this response to the renin-angiotensin aldosterone system.

DESIGN

A prospective, controlled study.

SETTING

A multidisciplinary intensive care unit of a teaching hospital.

SUBJECTS

Critically ill, volume-resuscitated, oliguric patients.

INTERVENTION

Dopamine was infused at a rate of 2 micrograms/kg/min. The change in urine output and sodium excretion was measured over a 6-hour period. Plasma Renin Activity (PRA) and serum aldosterone were measured before commencing low-dose dopamine.

OUTCOME MEASURE

Patients whose mean urine output increased by greater than 20 ml/hour were considered to have responded to low-dose dopamine.

RESULTS

Nine patients were studied. Five of the nine patients responded to low-dose dopamine. The mean increase in urine volume was 58.4 ml/hr in the responders compared with 5.0 ml/hr in the nonresponders. The mean PRA (normal, 0.8 to 2.5 ng/ml/hr) was 5.7 ng/ml/hr in the responders compared with 26.8 ng/ml/hr in the nonresponders (p = 0.042). A significant inverse correlation existed between the PRA and the increase in urinary output (r = -0.75; p = 0.019).

CONCLUSION

The response to renal dopamine in critically ill patients appears to be dependent on the interaction between the vasodilating-natriuretic effect of dopamine and the vasoconstricting antinatriuretic effect of the renin-angiotensin aldosterone system.

Renal dysfunction in enteric fever

Twenty-five culture positive cases of enteric fever were studied to see the effect of the disease on various kidney functions. The parameters studied were urine examination, blood urea, serum creatinine, serum electrolytes, 24 hours urinary examination (proteins, creatinine, electrolytes), creatinine clearance rate, plain X-ray abdomen, intravenous urogram and circulating immune complexes. Fifteen patients with fever of non-specific origin served as controls. Renal dysfunction was observed in four patients (16%). Repeat tests showed that abnormalities of renal functions, though significant, were short lasting and reversible. Renal biopsy done in three of these cases did not reveal any abnormality.

Ureteric sludge syndrome

Four cases of a form of obstructive uropathy previously unreported in children are described. All presented with oligoanuria and either flank pain or fluid retention and had evidence of crystalline sludge in their lower ureters. Three cases had an underlying crystalluria.

Pseudo-renal failure associated with internal leakage of urine

Three patients with internal leakage of urine are described. As a result of urine resorption into the blood a condition developed resembling acute renal failure. Internal loss of urine is divided into intraperitoneal and extraperitoneal leakage and usually gives rise to oliguria and microscopic haematuria. In the intraperitoneal type increasing abdominal complaints and ascites will develop whereas in the extraperitoneal type regional oedema will become present without, in the case of sterile urine, abdominal complaints of importance. Important clues as to the diagnosis are the concentrations in serum and urine of urea, creatinine and sodium, and the demonstration of the leak by means of imaging techniques. Treatment of choice is a drainage procedure, for instance by a bladder catheter. In acute renal failure this pseudo form should be distinguished from the real thing.

[Carbon tetrachloride poisoning: a report of 3 cases]

Carbon tetrachloride is a toxic solvent easily obtained in our country. 3 cases of poisoning by accidental inhalation at place of work. The main clinical manifestations were acute renal failure and toxic hepatopathy. All patients, had a good evolution with dialysis therapy after a few weeks. We comment on some possible additional therapies to be used in treating patients with severe poisoning due to carbon tetrachloride.

Monitoring renal function

Acute renal failure is a common cause of morbidity and mortality in critically ill patients. The prompt, effective management of acute oliguria, frequently the presenting sign of renal deterioration, remains difficult because of the lack of suitable monitors. No monitor presently in common use is sufficiently specific, sensitive, or rapidly available to satisfy clinical needs.

Urinary electrolytes

Urinary electrolytes can be a useful tool in the Emergency Department. For those patients with volume depletion, acute oliguria and hyponatremia, the determination of urinary sodium levels can aid in diagnosing the etiology of the presenting condition. Urinary potassium levels can aid the clinician in determining the cause of the potassium loss, either renal or extrarenal. For those patients with metabolic alkalosis, determination of the urinary chloride levels will allow the physician to determine if the alkalosis is chloride responsive or chloride resistant. It must be kept in mind that the measurement of any urinary electrolyte is relatively valueless unless it is interpreted with other data and/or observation of the patient. It should be noted also that a solitary value may not be adequate for making a diagnosis, and serial urinary electrolyte value assessment may be necessary. In the critically ill patient, it may be prudent to obtain a urine sample before the administration of a diuretic, the administration of potassium, or large amounts of saline. This procedure will allow for a more accurate assessment of the patient's pretreatment status.