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.

Association of oliguria with the development of acute kidney injury in the critically ill

Urine output (UO) criterion may increase the sensitivity of the definition of acute kidney injury (AKI). We determined whether the empirically derived definition for oliguria(<0.5 ml/kg/h) is independently associated with adverse outcome. Data analysis included hourly recorded UO from the prospective, multicenter FINNAKI study conducted in 16 Finnish intensive care units. Confounder-adjusted association of oliguria of different severity and duration primarily with the development of AKI defined by creatinine criterion (Cr-AKI) or renal replacement therapy(RRT) was assessed. Secondarily, we determined the association of oliguria with 90-day mortality. Of the 1966 patients analyzed for the development of AKI, 454 (23.1%) reached this endpoint. Within this AKI cohort, 312 (68.7%)developed Cr-AKI, 21 (4.6%) commenced RRT without Cr-AKI, and 121 (26.7%) commenced RRT with Cr-AKI. Episodes of severe oliguria (<0.1 ml/kg/h) for more than 3 h were independently associated with the development of Cr-AKI or RRT. The shortest periods of consecutive oliguria independently associated with an increased risk for 90-day mortality were 6–12 h of oliguria from 0.3 to <0.5 ml/kg/h, over 6 h of oliguria from 0.1 to <0.3 ml/kg/h, and severe oliguria lasting over 3 h.Thus, our findings underlie the importance of hourly UO measurements.

Low urine output during the first twenty-four hours after total knee arthroplasty

BACKGROUND

Low urine output (LUO) for six hours is defined as the stage that is at risk of acute renal failure. Major surgeries with a bloodless field, such as total knee arthroplasty (TKA), may be associated with LUO; however; there has been no study addressing this point. The present study evaluated the incidence of LUO and the effect of fluid balance on LUO in TKA patients during the first 24 hours after surgery.

MATERIAL AND METHOD

The authors retrospectively evaluated 257 uncomplicated patients undergoing unilateral TKA during the first 24 hours after surgery. Patients' demographic data, intra-operative intravenous (IV) fluid replacement, postoperative IV fluid replacement, oral fluid intake, total fluid intake, postoperative urine output, blood collected from the drain, and the total visible fluid output during the first 24 hours after surgery were collected and evaluated.

RESULTS

The incidence of LUO was 19.1% (49/257) in the studied group. There were no significant differences in patients' demographic data between the LUO and normal urine output (NUO) groups. Comparing the LUO and NUO groups, the LUO group had a lower volume of intra-operative fluid replacement, with statistical significance. There were no differences in postoperative IV fluid replacement and postoperative oral fluid intake between groups. Although 80.5% of the studied group had LV fluid replacement at a less than ideal level, at discharge there was no patient suffering from renal complications related to LUO.

DISCUSSION AND CONCLUSION

Urine output is one of the common monitoring parameters of fluid balance in the perioperative period; it should be ≥ 0.5 mL/kg/h. Prolonged low urine output for six hours and for 12 hours are categorized as causing risk and injury to the kidney, respectively. The incidence of LUO at our institution during the first 24 hours after TKA is not uncommon and is significantly related to intra-operative fluid replacement. Fortunately, all LUO patients had further fluid replacement, resulting in no renal complications at discharge. As eighty percent of patients had less than ideal fluid replacement, and patients having LUO during the first 24 hours had a significantly lower volume of intra-operative fluid replacement, the authors propose reconsidering perioperative fluid replacement in TKA patients, especially intra-operative IV fluid to avoid LUO.

Aminophylline improves urine flow rates but not survival in childhood oliguric/anuric acute kidney injury

INTRODUCTION

Acute kidney injury (AKI) morbidity and mortality rates remain high. Variable AKI outcomes have been reported in association with aminophylline treatment. This study evaluated AKI outcome in a group of Nigerian children treated with aminophylline.

METHODS

This is a retrospective study of AKI in children treated with (N=9) and without (N=8) aminophylline. Studied outcome indices comprised urine flow rate (UFR), duration of oliguria/anuria, progression through AKI stages, number of patients requiring dialysis and mortality.

RESULTS

Mean ages for the control and aminophylline arms were 4.6±2.7 and 4.9±2.1 years (P=0.7), respectively. All patients progressed to stage-3 AKI. Baseline median UFRs in the aminophylline and control arms were similar (0.13 Vs 0.04 ml/kg/hour respectively, P=0.5). The median UFR was significantly higher on day-5 (0.8 Vs 0.1; P=0.03), day-6 (1.0 Vs 0.2; P=0.02), and day-7 (1.2 Vs 0.2; P=0.03) in the aminophylline than the control arm, respectively. Short duration of oliguria/anuria (≤ 6 days) was more frequently observed in aminophylline- treated patients compared to controls (77.8% Vs 25.0%; odds ratio 0.09; 95% CI: 0.01-0.89; P=0.04). Only the aminophylline group maintained steady serum creatinine levels. Four out of five patients in the control group were dialyzed compared to only one out of eight patients in the aminophylline group (odds ratio 0.16; 95% CI: 0.04-0.71; P=0.03). Mortality rates were similar in aminophylline- treated and control patients (33% Vs 25%; hazard ratio 0.8; 95% CI: 0.1-5.5; P=0.8).

CONCLUSION

Aminophylline therapy was beneficial for patients with AKI in terms of improved UFR and reduced need for dialysis, but failed to impact positively on survival.

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.

Use of creatinine clearances to monitor the effect of low-dose dopamine in critically ill surgical patients

INTRODUCTION

Despite uncertain evidence of its efficacy, "low-dose dopamine" (2-5 microg/kg/min) has often been used to augment renal perfusion in critically ill surgical patients. The 2-h creatinine clearance (CC) has been shown to be a monitor of renal function in critically ill patients. We therefore studied the use of sequential CC determinations to monitor the effect of low-dose dopamine (LDD) in surgical intensive care unit (SICU) patients. We hypothesized that sequential CC measurements could demonstrate whether individual patients had positive responses in renal function to LDD.

METHODS

Data were prospectively collected for patients on LDD in a university SICU. CC were recorded for these patients immediately before and after the institution of LDD or before and after the cessation of LDD. APACHE II scores, gender, urine creatinine, age, blood pressure, heart rate, and urine output (UO) were also recorded for these patients; P < 0.05.

RESULTS

Twenty-four pairs of CC values were observed during the study. The mean APACHE II score for the patients was 15.1. In 10 cases after initiation of LDD, the mean CC increased from 52.5 +/- 23.7 ml/min to 68.1 +/- 33.8 ml/min (P = 0.056). UO also increased from 48.0 +/- 27 to 75.9 +/- 49 ml/h (NS). In 14 cases after discontinuation of LDD, CC decreased from 85.6 +/- 36.3 ml/min to 63.6 +/- 45.5 ml/min (P = 0.044) and UO decreased from 105.1 +/- 73.9 to 89.6 +/- 76.7 ml/h (NS). Overall, 13 of the 24 patients had a 25% change or more in CC upon initiation or cessation of LDD.

CONCLUSIONS

LDD institution increased CC in individual patients in the SICU population. Because using LDD in the absence of a discernable improvement in renal function is costly and may harbor risks, we recommend following CC in patients on LDD to determine which patients derive benefit from the intervention.

Comparison of the efficacy of continuous furosemide and low-dose dopamine infusion in preeclampsia/eclampsia-related oliguria in the immediate postpartum period

AIM

To compare the efficacy of furosemide infusion with that of low-dose dopamine infusion in improving urine output and subsequent renal function in preeclamptic/eclamptic patients with oliguria in the immediate postpartum period.

DESIGN

Prospective randomised single blind clinical trial.

SETTING

Obstetric High Care Unit of King Edward VIII Hospital, a large referral tertiary hospital.

METHOD

Eighty postpartum patients with severe preeclampsia/eclampsia with oliguria were enrolled. Hypovolaemia was corrected under central venous pressure (CVP) monitoring and urine output monitored for 4 hr. Patients who remained oliguric were randomly assigned to a continuous infusion of low-dose dopamine (3 microg/kg/min), or furosemide 5 mg/hr infusion, for 12 hr. In patients with no response after 12 hr, the drugs were switched and continued for a further 12 hr. A subgroup of patients who responded 4 hr after correction of hypovolaemia was observed for 12 hr. The primary outcome measured involved the comparison in urine output between the different drug regimes and the number of patients requiring haemodialysis. Secondary outcome measures involved assessment of serum urea and creatinine values in the two treatment groups.

RESULTS

Of the 80 patients enrolled, 20 improved their urine outputs within the 4-hr observation period. Sixty patients were randomised to furosemide or low-dose dopamine infusion. There was no statistical significant difference in the mean hourly urine output, rate of change in urine output over time and the mean urea or creatinine levels between the treatment groups. Ten percent of patients that failed on furosemide primarily, and 8.5% of patients that failed on initial low-dose dopamine, received haemodialysis. The difference in demographic and clinic data between these groups was not statistically significant.

CONCLUSION

Administration of continuous infusion of furosemide showed comparable efficacy to low-dose dopamine infusion in ameliorating oliguria in severe preeclampsia/eclampsia post delivery; there was no difference in the percentage of patients that required haemodialysis in either group.

Oliguria. A sign of renal success or impending renal failure?

Limiting renal impairment begins with identifying patients at increased risk for renal dysfunction (monitoring of renal function is important in these patients) and understanding the physiology of urine formation, the influence of anesthetic drugs, and intraoperative events on the physiology and pathophysiology of renal function. The fundamental principles emphasized in this article include avoidance of hypovolemia or renal hypoperfusion (e.g., hypotension, decreased cardiac output) in patients at risk (because of pre-existing disease or the nature of the operative procedure) and limitation of toxins that might jeopardize residual renal function. Direct monitors of renal well-being are still in the rudimentary stage of development. Indirect measures of renal function (CVP, MAP) are used on a minute-to-minute basis. The clinical measurement of urine output still is relied on when evaluating renal function over longer time intervals. Currently, only one drug (N-acetylcysteine) improves renal outcome after a high-risk procedure (radiocontrast administration) prophylactically. Manipulation of autorenal regulatory vasodilators (e.g., nitric oxide, PGE2) and vasoconstrictors (e.g., endothelin, vasopressin, angiotensin II) may prove helpful in the future. Currently, maintenance of adequate intravascular volume, MAP, and cardiac output are the most important renal protective measures an anesthesiologist can provide to preserve renal function high-risk patients.

Reemergence of sucrose nephropathy: acute renal failure caused by high-dose intravenous immune globulin therapy

Sucrose nephropathy was first described more than 50 years ago. The disorder is characterized by acute renal failure caused by the uptake of sucrose by renal proximal tubule cells with subsequent cellular swelling and occlusion of the tubule lumen. Approximately 114 cases of renal failure have been associated with high-dose intravenous immune globulin (IVIG) therapy. Almost all cases were caused by preparations containing large amounts of sucrose. Clinicians should consider using IVIG preparations containing no sucrose in patients who are at high risk for renal failure. Risk factors include older age, baseline renal failure, and volume contraction.

Antimony excretion in a patient with renal impairment during meglumine antimoniate therapy

Meglumine antimoniate was administered to a patient with visceral leishmaniasis with normal renal function. Soon after the first intramuscular administration of meglumine antimoniate 20 mg/kg, equivalent to 510 mg antimony (Sb), the patient developed septic shock with oliguria. Creatinine clearance decreased to 23 ml/minute. Treatment was discontinued, and Sb urinary excretion was measured. After the initial dose, 500.25 mg Sb was recovered in urine over 8 days, corresponding to 98% of the amount of Sb given intramuscularly (66% eliminated within first 48 hrs). Nine days after the dose, meglumine antimoniate was reintroduced at a dosage of 11.7 mg/kg (equivalent to 300 mg Sb) every 48 hours with good tolerance. At that time creatinine clearance had returned to 87.8 ml/minute. By day 14 of therapy the interval was reduced to daily administration of the same dose; the dosage was increased to 16.6 mg/kg/day (equivalent to 425 mg Sb) from day 17 to day 31. The patient eventually completely recovered and was discharged with normal renal function. Although no specific guidelines exist for dosage adjustment in renal failure, monitoring of Sb urinary excretion indicates that the kidneys are the almost exclusive route of elimination.

Low-dose theophylline increases urine output in diuretic-dependent critically ill children

OBJECTIVE

Determine the effect of low-dose theophylline on urine output and the urinary adenosine: cAMP (cyclic adenosine monophosphate) excretion ratio (a measure of phosphodiesterase inhibition) in diuretic-dependent critically ill children.

DESIGN

Observational clinical case series and animal laboratory experiment.

SETTING

A university pediatric intensive care unit and a pharmacology research laboratory.

PATIENTS

10 consecutive oliguric patients treated with theophylline for diuresis.

INTERVENTIONS

Urine output, fluid intake, diuretic dosages, and number of pressors (including dopamine) were monitored over the 24-h period prior to and the 24-h period immediately after theophylline was started. Hourly collections of urine were obtained at baseline and 1 and 3 h after theophylline was started and urinary excretion rates of adenosine and cAMP were measured and calculated.

MEASUREMENTS AND RESULTS

Mean theophylline level in the children was 5.0 microg/ml. Urine output increased from 1.58 +/- 0.46 to 3.75 +/- 0.77 ml/kg per h (p = 0.008, paired t-test) after theophylline administration. There was no significant change in fluid intake, vasoactive agents, or dosages of other diuretics during the study periods. Intrarenal infusion of the IC50 concentration of isobutylmethylxanthine for phosphodiesterase activity resulted in a reduction of the adenosine: cAMP urinary excretion ratio in rats (p < 0.05). Low-dose theophylline had no effect on the adenosine: cAMP urinary excretion ratio in children. Concurrent therapy with dopamine was associated with an enhanced diuretic effect of theophylline (with dopamine, 1.30 +/- 0.30 to 5.07 +/- 0.77 ml/kg per h vs without dopamine, 1.77 +/- 0.76 to 2.86 +/- 1.08 ml/kg per h; p = 0.03, two-way ANOVA). There was no interaction between dopamine and low-dose theophylline on the urinary adenosine: cAMP excretion ratio (p = 0.56, two-way ANOVA).

CONCLUSIONS

Theophylline increased urine output in diuretic-dependent critically ill children and the diuretic effect may have been potentiated by concurrent use of dopamine. Adenosine receptor antagonism may be a more likely mechanism for the diuretic effect of theophylline than phosphodiesterase inhibition.

Low dose dopamine in postpartum pre-eclamptic women with oliguria: a double-blind, placebo controlled, randomised trial

OBJECTIVE

To assess the effect of low dose dopamine on the urine output in postpartum pre-eclamptic or eclamptic women with oliguria.

DESIGN

A double blind, randomised controlled study.

SETTING

The high care area of the labour ward in a teaching hospital.

SAMPLE

Forty postpartum pre-eclamptic women with oliguria, defined as < 30 mL/hour, who have not responded to a 300 mL crystalloid fluid challenge.

INTERVENTION

Dopamine was infused at a rate of 1 to 5 microg/kg per minute, or sterile water was given as placebo in the same dilution.

MAIN OUTCOME MEASURE

Urine output, blood pressure and pulse was measured for six hours before and for six hours after the intervention.

RESULTS

Women who received dopamine (344 mL over 6 hours) showed a clinically and statistically significant (P = 0.0014, Mann-Whitney U test) higher median urine output compared with those receiving placebo (135 mL over 6 hours) for the duration of therapy. The respective 95% confidence intervals were 212.3 to 712.7 mL compared with 73.8 to 244.7 mL. No differences in blood pressure or pulse were found between the two groups.

CONCLUSIONS

The use of low dose dopamine in a labour setting improved urine output in postpartum pre-eclamptic women with oliguria who had not responded to a single fluid challenge without a detrimental effect on the blood pressure or pulse.

Serum aldosterone concentrations and urine output in oliguric intensive care unit patients receiving low-dose dopamine

OBJECTIVE

To determine whether the diuretic and natriuretic effects of low-dose dopamine (2.5 micrograms/kg/min) are associated with changes in serum aldosterone concentration.

DESIGN

Prospective clinical study.

SETTING

Surgical intensive care unit (SICU) of a university hospital.

PARTICIPANTS

Oliguric (urine output < 0.5 mL/kg/h) SICU patients. All patients were resuscitated to pulmonary artery occlusion pressure > 10 mm Hg, mean arterial pressure > 65 mm Hg, and cardiac index > 2.5 L/min/m2. Patients with a serum creatinine concentration > 176.8 mumol/L (2.0 mg/dL), those who received diuretics within 12 hours prior to entry into the study, and renal transplant recipients were excluded.

MAIN OUTCOME MEASURES

Hourly urine output (mean +/- SD) was recorded 2 hours before and for 6 hours after the initiation of low-dose dopamine. Urine sodium and serum aldosterone concentrations were obtained prior to and 6 hours after the start of low-dose dopamine.

RESULTS

Fifteen patients were enrolled in the study. Urine output (mean +/- SD) increased from 0.31 +/- 0.11 mL/kg/h before to 0.80 +/- 0.34 mL/kg/h following low-dose dopamine (p < 0.01). Urine sodium concentrations increased from 46 +/- 32 mmol/L baseline to 72 +/- 53 mmol/L following low-dose dopamine (p < 0.05), and serum aldosterone concentrations decreased from 415.82 +/- 341.48 pmol/L prior to low-dose dopamine infusion to 256.04 +/- 204.17 pmol/L (p < 0.05). Cardiac output, pulmonary artery occlusion pressure, mean arterial pressure, and heart rate did not change.

CONCLUSIONS

Low-dose dopamine significantly increases urine output and urine sodium excretion in oliguric, critically ill, surgical patients, and is associated with a decrease in serum aldosterone concentration. The diuretic and natriuretic effects of low-dose dopamine may be, in part, related to a dopamine-mediated inhibition of aldosterone secretion.

Fractional excretion of trace lithium and uric acid in acute renal failure

The early distinction between prerenal azotemia, characterized by an avid proximal tubular sodium reabsorption, and ATN, in which proximal tubule function is depressed, remains an important but difficult clinical task. Indices of acute renal failure based on urinary sodium excretion may be helpful but have several limitations, among which is the use of diuretics. The effectiveness of the fractional excretion of uric acid (FEUA) and that of endogenous lithium (FELi) in the diagnosis of acute renal failure has been evaluated in an unselected group of 46 patients, 28 with prerenal azotemia and 18 with ATN. In the entire group, FELi concurred with the clinical diagnosis in 78% of the patients, whereas the fractional excretion of sodium (FENa) and FEUA were in agreement in only 63 and 50%, respectively. FELi was more sensitive to identify hemodynamic renal failure, because 93% of prerenal failure patients had a low FELi, contrasting with a low FEUA in only 68% and a low FENa in 75%. The major reason for the discrepancy between FENa and FELi was the administration of diuretics. In both acute renal failure groups, FENa was higher in the subgroups receiving diuretics. In contrast, diuretic therapy had no effect on FELi in either group. These results suggest that FELi is more accurate than either FENa or FEUA for distinguishing prerenal azotemia from ATN. The superiority of FELi appears especially relevant in patients treated with the usual diuretics.

[Urinary excretion of Tamm-Horsfall protein by patients with acute renal failure]

Urinary excretion of Tamm-Horsfall protein (THP), sodium and potassium was assessed in 12 patients 5, 8, 11, 14, 17, and 22 days after the onset of acute renal failure (ARF) and in 23 control subjects. In patients with ARF at the oliguric phase urinary excretion was significantly reduced but significantly increased (when compared with controls) at the onset of the polyuric phase. In contrast to healthy subjects in patients with ARF no significant correlation was found between urine volume and urinary excretion of THP. Normalization of THP excretion was noticed prior to normalization of serum creatinine level. Results obtained in this study prove absence of the physiological relationship between urinary excretion of THP and urine volume in patients with ARF.

Use of dopexamine hydrochloride in patients with septic shock

The short and long-term hemodynamic effects of iv dopexamine hydrochloride (DPX) were studied in ten patients with septic shock. In the short-term study, a dose-dependent increase in cardiac index and heart rate, and a dose-dependent decrease in systemic vascular resistance were demonstrated. These effects diminished gradually during the long-term study, suggesting a problem of tolerance. Although the administration of DPX during septic shock appeared to be relatively safe, its hemodynamic effects suggest that it may be more indicated in selected patients with a low cardiac output.

Effects of low-dose dopamine therapy in the oliguric patient with preeclampsia

Central hemodynamic and renal responses to low-dose dopamine (1 to 5 micrograms/kg/min) infusion were studied in six oliguric (less than 0.5 ml/kg/hr) patients with severe preeclampsia. Hemodynamic parameters were measured and renal function tests were done before and during therapy. There was a significant rise in urine output from a mean (+/- SD) of 21 +/- 10 to 43 +/- 23 ml/hr, accompanied by a rise in cardiac output from 6.8 +/- 1.8 to 8.0 +/- 2.3 L/min (p less than or equal to 0.05). There were no significant changes in blood pressure, central venous pressure, or pulmonary capillary wedge pressure. The fractional excretion of sodium, negative free water clearance, and osmolar clearance tended to rise during dopamine therapy. No adverse maternal or fetal effects occurred. We conclude that low-dose dopamine produces a significant increase in urine production with resolution of oliguria in severe preeclampsia.

[Neonatal oliguria associated with hyperuricemia]

Acute renal failure syndrome in the newborn has many etiologic factors. Hyperuricemia as unique etiology of this syndrome has been seldom cited in literature, although is a well know factor operating together with others. From nine newborns with oliguria, hyperuricemia vas a contributing factor in appearance of the syndrome in seven. In the other two cases hyperuricemia was the sole possible etiologic factor in development of oliguria which was classified as functional. Hyperuricemia alone may be the unique etiologic factor in functional oliguria of the newborn being further investigations needed to understand its precise mechanism.

The use of urinary diagnostic indices in pre-eclampsia-associated oliguria

A case is presented of severe pregnancy-induced hypertension that was complicated by oliguria and managed with the aid of a pulmonary artery catheter. This case illustrates that urinary diagnostic indices may be unreliable in predicting the etiology of oliguria. Although urinary diagnostic tests are advocated routinely as reliable in the nonobstetric literature, possible misinterpretation of these values in severe pre-eclampsia with oliguria may require confirmation with hemodynamic data obtained from a pulmonary artery catheter.

Urinary diagnostic indices in preeclampsia-associated oliguria: correlation with invasive hemodynamic monitoring

Seven oliguric women with preeclampsia were identified among patients admitted for obstetric care at Jefferson Davis or Hermann Hospitals in Houston, Texas. Urinary diagnostic indices (including urine-to-plasma ratios of creatinine, urea nitrogen, and osmolality) were generally consistent with a prerenal etiology for the observed oliguria. Conversely, invasive hemodynamic monitoring revealed a volume replete state in five of seven preeclamptic women studied. All patients were observed to have markedly elevated urinary sodium concentrations. The transient oliguria observed in these patients spontaneously resolved without diuretic or hyperosmolar agents. We conclude that oliguria is a poor index of volume status in preeclamptic women. Urinary diagnostic indices may also be misleading if used to guide fluid management in these patients. Finally, the clinical significance and therapeutic alternatives relating to preeclampsia-associated oliguria are discussed.

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.

Urinary sodium and chloride during renal salt retention

One hundred ten episodes of renal salt retention (urinary sodium and/or chloride less than 10 mEq/L) were studied retrospectively to determine the significance of discordance of urinary sodium from chloride. In 16 episodes the urinary sodium exceeded chloride by at least 15 mEq/L. This disparity was associated with the necessity for urinary excretion of substantial quantities of poorly reabsorbed anions (penicillin, ketones, or diatrizoate), a rapidly falling serum bicarbonate level (due to resolving metabolic or developing respiratory alkalosis), or substantial renal insufficiency (serum creatinine greater than 3 mg/dL). In 14 of 110 episodes, urinary chloride exceeded urinary sodium by at least 15 mEq/L. These patients were more often oliguric and had a higher mean serum chloride than patients without this dissociation. In patients with oliguria, hyponatremia, or metabolic alkalosis, measurement of urinary sodium or chloride alone will, in a substantial number of cases, fail to detect renal salt retention. When evidence is sought for renal salt retention, both urinary sodium and chloride should be determined.

Plasma retinol and retinol binding protein concentrations in patients on maintenance haemodialysis with and without vitamin A supplements

Plasma retinol and retinol-binding protein (RBP) concentrations have been estimated in patients on maintenance haemodialysis over a 4-year period. For the first 2 years multivitamin supplements containing vitamin A were taken, and for the second 2 years no vitamin A supplements were given. Mean plasma retinol concentrations decreased significantly but only from 3.8 times normal to 3.1 times normal after vitamin A supplements stopped. There was no significant change in th high plasma RBP levels. Ultracentrifugation of plasma at a salt density of 1.21 showed that nearly all the retinol was associated with RBP in the high density protein fraction, as it is with normal subjects. Column chromatography confirmed that there was no increase in plasma retinyl esters in the renal failure patients, as is found in hypervitaminosis A due to drug overdosage. The high plasma retinol and RBP levels remained remarkably stable in individual patients throughout the 4-year study. The increase in plasma RBP was possibly related to residual urine output. The results are compatible with a feedback mechanism whereby the extent of the increase in plasma RBP as renal failure develops controls the consequent high plasma level of retinol.

Patterns of N-acetyl-beta-D-glucosaminidase excretion after renal transplantation

N-Acetyl-beta-D-glucosaminidase activity (NAG) was assayed in 750 early morning urine samples from 25 renal transplant patients during the post operative period. Eighty four per cent of all acute rejection episodes were preceded or accompanied by a greater than two-fold rise in NAG activity; similar increases were caused by dialysis, gentamicin therapy and ureteric dehiscence. Only 9% of all significant increases in NAG excretion could not be accounted for by any of these four processes. Analysis of the day-to-day pattern of NAG activity as opposed to individual NAG values provided a clue to the occurrence of rejection during immediate post-transplantation oliguria.