Is low proteinuria an early predictor of severity of acute pancreatitis?

[Acute kidney injury following acute pancreatitis (AP-AKI): Definition, Pathophysiology, Diagnosis and Therapy]

Acute pancreatitis (AP) is the most frequent gastrointestinal cause for hospitalization and one of the leading causes of in-hospital deaths. Severe acute pancreatitis is often associated with multiorgan failure and especially with acute kidney injury (AKI). AKI can develop early or late in the course of the disease and is a strong determinator of outcome. The mortality in the case of dialysis-dependent AKI and acute pancreatitis raises exponentially in the affected patients. AP-induced AKI (AP-AKI) shows many similarities but also distinct differences to other causes of AKI occurring in the intensive care unit setting. The knowledge of the exact pathophysiology can help to adjust, control and improve therapeutic approaches to the disease. Unfortunately, there are only a few studies dealing with AP and AKI.In this review, we discuss recent data about pathogenesis, causes and management of AP-AKI in patients with severe acute pancreatitis and exploit in this regard the diagnostic and prognostic potential of respective newer serum and urine markers.

Microalbuminuria assessment after thoracic surgery: Early identification of complication risks

INTRODUCTION

Microalbuminuria (MA) is considered a reflection of systemic capillary leak and an early marker of acute stress reaction to the surgical insult, proportional to the severity of the initiating condition and predictive of the individual response to surgical stress.

OBJECTIVES

We conducted a prospective study to assess for the variation of MA within 4 days after thoracic surgery. We correlated observed MA levels with both their respective PaO₂ /FiO₂ respiratory ratio and the onset of postoperative complications.

METHODS

This single-centre study enrolled 255 consecutive patients having an American Society of Anaesthesiologists (ASA) score ≤ 3. The mean age was 62 years with 67% male. All patients were scheduled for elective pulmonary resection. MA was measured in urine samples as the albumin-to-creatinine ratio (A/C), prior to, at and after extubation up to 96 hours. PaO₂ /FiO₂ was measured at extubation and on the first postoperative day.

RESULTS

Overall, preoperative A/C levels resulted normal, with a significant average increase at extubation which peaked 6 hours later (P < 0.001). Larger postoperative A/C increases were observed in patients who developed postoperative complications, compared to those without these complications (P < 0.019). Moreover, patients undergoing major open pulmonary resections had larger postoperative A/C increases, compared to those undergoing minor video-assisted thoracic surgery resections (P < 0.006). At the time of extubation, A/C was inversely related to the PaO₂ /FiO₂ ratio (r = -0.25; P = 0.038). Peak A/C > 61 mg/g (P = 0.0003) was associated with postoperative cardio-pulmonary complications (OR 3.85; P = 0.003).

CONCLUSION

Within 6 hours after extubation, MA assessment may be a rapid and relatively inexpensive method for better predicting perioperative risk in an ASA score ≤ 3 population.

Multifactorial Scores and Biomarkers of Prognosis of Acute Pancreatitis: Applications to Research and Practice

Acute pancreatitis (AP) is a severe inflammation of the pancreas presented with sudden onset and severe abdominal pain with a high morbidity and mortality rate, if accompanied by severe local and systemic complications. Numerous studies have been published about the pathogenesis of AP; however, the precise mechanism behind this pathology remains unclear. Extensive research conducted over the last decades has demonstrated that the first 24 h after symptom onset are critical for the identification of patients who are at risk of developing complications or death. The identification of these subgroups of patients is crucial in order to start an aggressive approach to prevent mortality. In this sense and to avoid unnecessary overtreatment, thereby reducing the financial implications, the proper identification of mild disease is also important and necessary. A large number of multifactorial scoring systems and biochemical markers are described to predict the severity. Despite recent progress in understanding the pathophysiology of AP, more research is needed to enable a faster and more accurate prediction of severe AP. This review provides an overview of the available multifactorial scoring systems and biochemical markers for predicting severe AP with a special focus on their advantages and limitations.

Association of Urinary Albumin:Creatinine Ratio with Outcome of Children with Sepsis

Objective

The aim of the study was to investigate the association of urinary albumin:creatinine ratio (ACR) with regard to the outcome of sepsis patients and to study the trends of ACR with severity of disease, organ dysfunction, microcirculation status, the use of inotrope, and mechanical ventilation use, and length of pediatric intensive care unit (PICU) stay.

Materials and methods

In the prospective observational study, the patients with varying categories of sepsis admitted in the PICU with stay >24 hours were enrolled consecutively. Urine samples were collected at the time of admission (ACR1), 12 hours (ACR2), and 24 hours (ACR3).

Results

One hundred and thirty-eight patients including 56 cases of sepsis, 31 of severe sepsis, 22 of septic shock, and 29 of multiorgan dysfunction syndrome (MODS) cases were analyzed. There were 29 (21%) deaths. ACR (median, IQR) was significantly higher in nonsurvivors [ACR1 198.9 (111.2–329.4) vs 124.5 (59.37–294.5), p 0.03], [ACR2 213.8 (112.5–350) vs 117.8 (62.6–211.9) p 0.008], [ACR3 231.8 (99.9–441.2 vs 114.4 (44.1–240.3), p 0.005]. The ACR is increased progressively with the increasing severity of sepsis (p < 0.001). The performance of ACR operative characteristics was compared with that of PRISM and PELOD scores. In deceased, ACR was significantly correlated with blood pH, lactate, and base deficit. A cutoff value of ACR 102.7 mg/g had sensitivity 86.2%, specificity 40.4%, positive predictive value 27.8%, and negative predictive value 91.7%. The use of inotropes, mechanical ventilation (>48 hours), and mortality was significantly higher in patients with ACR >102 mg/g. The probability of death varied from 17.6 to 19% in the first 24 hours of admission. ACR was significantly cheaper as compared to PRISM score and PELOD score estimations.

Conclusion

Urinary ACR, a cost-effective tool, correlates with the severity of sepsis and associated morbidity and mortality in children.

How to cite this article

Sachdev A, Raheja K, Gupta N, Chugh P. Association of Urinary Albumin:Creatinine Ratio with Outcome of Children with Sepsis. Indian J Crit Care Med 2020;24(6):465–472.

Investigating the relationship between microalbuminuria and prognosis of patients with severe burns in the Motahari Burn Hospital

Microalbuminuria seems to be a reflection of increased vascular permeability caused by systemic inflammatory response, and is likely to be a predictor of mortality, sepsis and other outcomes of severe burn patients. We investigated the impact of microalbuminuria on the prognosis of patients with severe burns. This is a prospective study on severe burn patients (above 20%) admitted in the first 24 hours after burns to the Motahari Burn Hospital. Patients' microalbuminuria was measured at admission and 48 hours later, and its relationship with patient prognosis (sepsis, renal failure, death, inhalation injury and systemic inflammatory response syndrome) was analyzed. We concluded that microalbuminuria at admission in patients with severe burns was directly related to inhalation injury (P = 0.018), ARDS during hospitalization (P = 0.001) and length of hospital stay (P = 0.025). Moreover, microalbuminuria at 48 hours after admission had a direct connection with patient death (P = 0.001), sepsis (P = 0.001), renal failure (P = 0.001) and SIRS (P = 0.001). Microalbuminuria is a simple, noninvasive, fast and affordable test to predict sepsis, mortality, renal failure, systemic inflammatory response and a finding associated with inhalation injury in severe burn patients, making it a fast prognostic predictor that helps to improve the management of these patients.

Microproteinuria Predicts Organ Failure in Patients Presenting with Acute Pancreatitis

BACKGROUND AND AIMS

The disease course of acute pancreatitis (AP) ranges from mild and self-limiting to severe inflammation, associated with significant morbidity and mortality. At present, there are no universally accepted and reliable predictors for severity. Microproteinuria has been associated with the presence of systemic inflammatory response syndrome as well as trauma, although its association with AP is not well understood. The aim of this study was to investigate the value of microproteinuria to predict development of organ failure in AP.

METHODS

Consecutive AP patients were prospectively enrolled. Urine samples were collected upon admission, 12-24 h after admission, and 3 months post-discharge for calculation of urine α1-microglobulin-, albumin-, IgG-, and IgM/creatinine ratios. Data regarding AP etiology, severity, and development of organ failure were registered.

RESULTS

Overall, 92 AP patients were included (14 % with organ failure; 6 % with severe AP). The α1-microglobulin-, albumin-, and IgG/creatinine ratios correlated with high-sensitivity C-reactive protein 48 h after admission (r = 0.47-0.61, p < 0.001 for all). They were also significantly higher in patients with versus without organ failure (p < 0.05 for all). The α1-microglobulin/creatinine ratio upon admission predicted organ failure [adjusted odds ratio 1.286, 95 % confidence interval (CI) 1.024-1.614] with similar accuracy (AUROC 0.81, 95 % CI 0.69-0.94) as the more complex APACHE II score (AUROC 0.86, 95 % CI 0.70-1.00).

CONCLUSION

The α1-microglobulin/creatinine ratio upon presentation with AP is related to inflammation and predicts development of organ failure. Further studies are warranted to evaluate its potential usefulness in predicting outcome for AP patients.

The predictive value of proteinuria in acute pancreatitis

BACKGROUND/OBJECTIVES

Acute pancreatitis has a highly variable clinical course. Early and reliable predictors for the severity of acute pancreatitis are lacking. Proteinuria appears to be a useful predictor of disease severity and outcome in a variety of clinical conditions. This study aims to investigate the predictive value of proteinuria on admission for the severity of acute pancreatitis compared with other commonly used predictors; the APACHE II score, Modified Glasgow score and C-reactive protein (CRP).

METHODS

This is a post-hoc analysis of 64 patients admitted with acute pancreatitis treated in one teaching hospital, who participated in a previous randomized trial. Proteinuria was defined as a Protein/Creatinine (P/C) ratio >23 mg/mmol. The primary endpoint was severe acute pancreatitis. Secondary endpoints included infectious complications, need for invasive intervention, ICU stay and in-hospital mortality.

RESULTS

Proteinuria was present in 30/64 patients (47%). Eleven patients (17%) had severe acute pancreatitis. There was no difference in incidence of severe acute pancreatitis between patients with and without proteinuria: 6/30 patients (20%) versus 5/34 patients (15%) respectively (p = 0.58). Likewise, the occurrence of infectious complications, need for intervention and ICU stay and mortality did not differ significantly (p = 0.58, p = 0.99, p = 0.33 and p = 0.60 respectively). The diagnostic performance of the P/C ratio for the prediction of severe pancreatitis was inferior to the Modified Glasgow score (p = 0.04) and CRP (p = 0.03).

CONCLUSION

Proteinuria on admission does not seem to be a reliable predictor for disease severity in acute pancreatitis. The diagnostic performance of the P/C ratio is inferior to the Modified Glasgow score and CRP.

The utility of microalbuminuria measurements in pediatric burn injuries in critical care

PURPOSE

Microalbuminuria, as measured by urinary albumin-creatinine ratios (ACRs), has been shown to be a marker of systemic inflammation and an indicator of the potential severity of trauma and critical illness. Severe pediatric burns represent the best model in which to investigate the clinical utility of microalbuminuria. This study aims to ascertain whether ACR measurements have any role in predicting the severity or the intensive care requirements in the critically unwell pediatric burn population.

MATERIALS AND METHODS

A retrospective observational study was undertaken within a regional burn center with a dedicated 8-bed burn intensive care unit (ICU). This looked at 8 years of consecutive pediatric burns requiring intensive care support-a total of 63 patients after exclusions. Daily urinary ACR measurements were acquired from all patients.

RESULTS

All patients had greater than or equal to 1 ACR measurement out with the reference range, and only 8% (5/63) presented to the ICU with a normal ACR. The median day for the peak ACR measurement was day 4. The relative lack of mortalities (3/63) precluded adequate correlations between ACR and outcomes. Peak and mean ACR values correlate well with length of ICU stay, and the peak ACR also correlates with total length of hospital stay and severity of burn injury as measured by total body surface area burnt and number of organ systems requiring support. No significant differences were found when the patients were stratified by age. The peak ACR measurement was found to be independently predictive of the length of the ICU stay. As such, we have created a predictive model to prove that an ACR that remains less than 12 mg/mmol is predicative of an ICU stay of less than or equal to 7 days.

CONCLUSIONS

The clinical utilities of ACR measurements are demonstrated by their correlation with the severity of injury, length of ICU stay, and requirements for multiple organ support. Albumin-creatinine ratios raised over certain thresholds highlight to the clinician the need for closer observation and the potential deterioration of patients.

Prevalence, predictors and prognostic significance of microalbuminuria in acute cardiac patients: a single center experience

The objective of this study was to prospectively assess the prevalence, predictors and prognostic significance of microalbuminuria in a large cohort of consecutive acute cardiac patients, admitted to an intensive cardiac care unit from 1 January 2008 to 30 June 2009. In 815 acute cardiac patients, microalbuminuria is detectable in 39.3%. Microalbuminuria shows a significant negative correlation with left ventricular ejection fraction (Spearman's ρ = -0.228; p < 0.001), while it is positively correlated with C-reactive protein (Spearman's ρ = 0.239; p < 0.001), NT-pro-BNP (Spearman's ρ = 0.306; p < 0.001) and glycemia (Spearman's ρ = 0.191; p < 0.001). Microalbuminuria is an independent predictor for in-hospital mortality (1 μg/min step) (OR 1.015; 95% CI 1.008-1.023; p < 0.001). In the acute phase of cardiac patients, microalbuminuria is a common finding, and it represents an independent predictor for early mortality. It is strictly linked to the inflammatory activation (as indicated by C-reactive protein) and to acute glucose values, thus suggesting that it may be part of the acute response to stress.

Microalbuminuria in non-diabetic STEMI: an independent predictor for acute kidney injury

AIMS

To assess the impact of microalbuminuria on the development of acute kidney injury and to investigate its prognostic role at long term follow-up in 526 consecutive patients with ST elevation myocardial infarction without previously known diabetes.

METHODS

Microalbuminuria was measured using immunonephelemetry in the urine collected in the night.

RESULTS

Patients with microalbuminuria were older (p = 0.013). They showed higher values of peak glycemia (p = 0.017), peak Tn I (p < 0.001), NT-pro BNP (p = 0.020), ESR (p = 0.003), CRP (p = 0.020), and leukocyte count (p < 0.001). Lower eGFR was observed in patients with microalbuminuria both on admission and during ICCU stay (p = 0.048 and p = 0.003, respectively). A positive correlation was observed between CRP and microalbuminuria (Spearman's rho 0.114, p = 0.024). The composite end point was observed in 73 patients (18 patients died and 59 patients developed acute kidney injury). At multivariable regression analysis, microalbuminuria was an independent predictor of acute kidney injury. At follow-up [42.6 (25th-75th percentile, 17.5-56.8) months], Kaplan-Meier curve analysis showed that patients with microalbuminuria had a lower survival rate in respect to patients without microalbuminuria. Cox regression analysis documented that microalbuminuria was an independent predictor of long term mortality (HR: 1.089; 97% CI 1.036-1.145; p < 0.001).

CONCLUSIONS

In a large series of STEMI patients without previously known diabetes submitted to PCI, microalbuminuria, as a marker of endothelial permeability following higher systemic inflammatory activation and larger infarct lesions, is an independent predictor for the development acute kidney injury. Furthermore, microalbuminuria identifies a subset of patients at higher risk for long term mortality.

Point-of-care urine albumin:creatinine ratio is associated with outcome in emergency department patients with sepsis: a pilot study

OBJECTIVES

Sepsis is characterized by an initial systemic proinflammatory response leading to endothelial damage and increased capillary permeability. The authors conducted a pilot study to determine if microalbuminuria, measured by the urine albumin:creatinine ratio (ACR), was associated with outcome in emergency department (ED) sepsis patients.

METHODS

This was an observational cohort study of a convenience sample of adult patients presenting to two EDs over 10 months with sepsis (two or more systemic inflammatory response syndrome [SIRS] criteria and suspected infection). Those who received a urinalysis were prospectively enrolled. Patients with anuria, grossly contaminated specimens, or concurrent noninfectious diagnoses were excluded. Urine ACR was measured on a point-of-care (POC) device. The primary study outcome was ED disposition (three groups): treated and discharged, admitted to the floor, or admitted to the intensive care unit (ICU). Kruskal-Wallis testing was used to compare ACR based on disposition. Variables associated with ACR were identified by Spearman rank correlation or Mann-Whitney rank-sum testing. A post hoc subgroup analysis of patients with and without a genitourinary (GU) source of infection was also performed.

RESULTS

A total of 121 patients were screened, and 29 (24%) were excluded; 92 patients met criteria (mean ± SD age, 51.2 ± 17.0 years; 51 [55%] had severe sepsis, three [3%] had septic shock). There were three in-hospital deaths. Median ACR for patients treated and discharged (n = 22), admitted to floor (n = 50), and admitted to ICU (n = 20) was 2.54 (interquartile range [IQR] = 0.89 to 6.16) versus 2.8 (IQR = 1.69 to 8.8) versus 12.15 (IQR = 4.76 to 20.95), respectively (p = 0.0049). Age, serum creatinine, and GU source of infection were associated with ACR. ACR was significantly associated with disposition among patients without a GU source of infection (p = 0.003), but not among patients with a GU source (p = 0.3744).

CONCLUSIONS

In this pilot study, microalbuminuria measured by POC ACR was associated with disposition in ED patients with sepsis or severe sepsis. Larger studies using more robust outcomes comparing ACR with validated sepsis biomarkers are needed to elaborate on these results.

Microalbuminuria: An inexpensive, non invasive bedside tool to predict outcome in critically ill patients

This study was conducted to evaluate whether microalbuminuria on admission and after 24 hrs of admission to intensive care unit (ICU) predicts outcome as well as the Acute Physiology and Chronic Health Evaluation (APACHE) II severity illness score, the current accepted method of doing so. The study was carried out in a 20 bed mixed medical-surgical ICU of a tertiary care hospital. Of 525 consecutive adult patients with ICU stay of more than 24 hrs, 238 were included for the study. Patients with pregnancy, menstruation, anuria, macroscopic hematuria, urinary tract infection, marked proteinuria due to renal and post-renal structural diseases, were excluded. Spot urine samples were collected on admission to ICU and 24 hrs thereafter. Urine albumincreatinine ratio (ACR) was measured on ICU admission (ACR1) and after 24 hrs (ACR2) and expressed in mg/g. Patient demographics were noted on admission. For disease severity scoring, APACHE II scores were calculated. Each patient was followed up throughout their ICU stay for a maximum of 28 days and the following outcome data were obtained: ICU length of stay and ICU mortality. Of the 238 patients, 196 survived while 42 patients died in the ICU. Non-survivors had a significantly higher median ACR2 [162.7 mg/g (IQR 69.5-344.3)] in comparison to the survivors who had a median ACR2 = 54.4 mg/g (IQR 19.0-129.1) (P< 0.0001). The median ACR1 [161.0 mg/g (IQR 29.0-369.3)] of non-survivors was higher than the median ACR1 [80.4 mg/g (IQR 35.1-167.6)] of survivors but failed to reach statistical significance (P= 0.0948). In a receiver operating characteristic curve (ROC) analysis, ACR2 emerged as the best indicator of mortality [(area under curve (AUC) of ACR2 = 0.71 > AUC (ACR1) =0.58 > AUC (ΔACR) =0.55] similar to the currently used APACHE II scores (AUC = 0.78) (P=0.3). At a cutoff of 101 mg/g, ACR2 had a sensitivity of 69%, specificity of 67%, positive predictive value of 31% and a negative predictive value of 91% for predicting mortality in the critically ill patients. Absence of significant microalbuminuria at 24 hrs of ICU admission may help to predict survival in the ICU.

Usefulness of serum IgG4 in the diagnosis and follow up of autoimmune pancreatitis: A systematic literature review and meta-analysis

High circulating serum immunoglobulin G4 (IgG4) levels have been proposed as a marker of autoimmune pancreatitis (AIP). The aim of the present study was to review the data existing in the English literature on the usefulness of the IgG4 serum levels in the diagnosis and follow up of patients with AIP. A total of 159 patients with AIP and 1099 controls were described in seven selected papers reporting the usefulness of serum IgG4 in diagnosing AIP. In total, 304 controls had pancreatic cancer, 96 had autoimmune diseases, and the remaining 699 had other conditions. The summary receiver-operating characteristic curve analysis was carried out by means of Meta-DiSc open-access software. Serum IgG4 showed good accuracy in distinguishing between AIP and the overall controls, pancreatic cancer and other autoimmune diseases (area under the curve [+/- SE]: 0.920 +/- 0.073, 0.914 +/- 0.191, and 0.949 +/- 0.024, respectively). The studies analyzed showed significantly heterogeneous specificity values in each of the three analyses performed. The analysis of the four studies comparing AIP and pancreatic cancers also showed significantly heterogeneous values of sensitivities and odds ratios. Regarding the usefulness of IgG4 as a marker of efficacy of steroid treatment, a decrease in the serum concentrations of IgG4 was found in the four available studies. The serum IgG4 subclass is a good marker of AIP, and its determination should be included in the diagnostic workup of this disease. However, the heterogeneity of the studies published until now means that more studies are necessary in order to better evaluate the true accuracy of IgG4 in discriminating AIP versus other autoimmune diseases.

Probing the urinary proteome of severe acute pancreatitis

BACKGROUND

Proteinuria is a characteristic feature of severe acute pancreatitis (SAP) that may allow unique insights into AP pathophysiology. This study used a proteomic approach to differentiate the abundant urinary proteins in AP patients.

MATERIALS AND METHODS

Urine samples were prospectively collected from 4 groups (5 SAP, 10 mild gallstone AP, 7 mild alcohol AP, 7 controls). Reverse-phase high-performance liquid chromatography (RP-HPLC) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (LC MALDI) were used to identify urinary proteins and determine any differences between the groups.

RESULTS

There were 17 RP-HPLC major peaks in SAP groups of significantly greater absorbance magnitude than the corresponding ones in mild and control groups. Various mass spectrometry methods were used to identify 21 different parent proteins from these SAP peaks. They included fibrinogen, serum amyloid A, insulin and calcitonin gene-related peptides. There were no identifiable protein peaks at the corresponding elution times in the mild pancreatitis and controls samples.

DISCUSSION

Proteomic techniques offer a unique unexplored window into AP pathophysiology. The utility of these proteins as markers of pancreatitis severity now need to be further investigated and the identification extended to the full urinary proteome as technology permits.

Microalbuminuria: A marker of endothelial dysfunction in thermal injury

INTRODUCTION

Systemic endothelial dysfunction (SED) and capillary leak occur following severe burn. SED can be assessed as low-level albuminuria (microalbuminuria) detectable only by sensitive immunoassay. This study compared the magnitude and duration of microalbuminuria with burn surface area and associated aggravating factors.

METHODS

Serial urine specimens were collected from 2 to 36 h after injury from 43 adult burn patients with a mean total body surface area (TBSA) of 32% (range 15-68%) and during 44 episodes of wound manipulation within the same period. Urinary albumin was expressed as the albumin/creatinine ratio (ACR, normal <2.3 mg/mmol).

RESULTS

Median ACR was highest 2h after injury (12.3 range 1.8-118 mg/mmol) returning to normal within 6 h. Full thickness burns (mean 17%) showed a significant association with ACR between 3 and 7h after burn. ACR was higher for up to 8 h in the presence of inhalation injury, alcohol intoxication or accelerant (p<0.05). ACR rose within 30 min of escharotomy or wound scrubbing (p<0.01).

CONCLUSION

Severe burn produces variable SED which recurs with wound manipulation. Inhalation injury, alcohol intoxication and accelerant all showed a stronger association with SED than TBSA. Microalbuminuria provides a means of monitoring microvascular integrity during the early after injury period.

Microalbuminuria in the intensive care unit: Clinical correlates and association with outcomes in 431 patients*

OBJECTIVE

Comparison of urine albumin within 6 hrs of intensive care unit (ICU) admission with demography, clinical classification, outcome, inotrope/vasopressor requirement, clinical assessment of mortality risk, and Sequential Organ Failure Assessment (SOFA) and Acute Physiology and Chronic Health Evaluation (APACHE) II scores.

DESIGN

Urine albumin-creatinine ratio (ACR) was measured on ICU admission (ACR 1) and after 4-6 hrs (ACR 2).

SETTING

A 17-bed general ICU in a university teaching hospital.

PATIENTS

Unselected medical (206) and surgical (225) patients recruited prospectively.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Bedside urine ACR was measured by nurses using a Bayer DCA 2000 analyzer and expressed in mg/mmol (reference range <2.3). ACR 1 in medical and surgical patients was 15.5 (12.4-19.5) and 8.2 (5.9-11.1) mg/mmol, respectively (p = .0002), and ACR 2 was 9.0 (5.8-12.5) and 4.6 (3.6-5.3), respectively (p < .0001). For all patients, median (95% confidence interval) ACR fell from 11.2 (8.7-13.2) to 5.4 (4.7-6.8) mg/mmol 4-6 hrs after ICU admission (p < .0001). ACR 1 for nonsurvivors (n = 90) and survivors (n = 341) was 16.1 (11.2-21.3) and 8.8 (6.9-11.9), respectively (p = .0002) and ACR 2, 12.4 (8.2-18.9) and 4.8 (3.9-5.4), respectively (p < .0001). In both medical and surgical patients who died on the ICU, median ACR failed to decrease significantly following admission. ACR1 and ACR 2 were higher in patients who required inotropic or vasopressor support and correlated with duration of therapy. ACR 1 and 2 were inversely correlated with mean Po2/Fio2 ratio 48 hrs after ICU admission and positively correlated with duration of mechanical ventilation and ACR 1 with ICU stay. ACR 2 predicted mortality and ACR 1 inotrope requirement independent of clinical mortality risk assessment and APACHE II and SOFA scores.

CONCLUSIONS

Urine albumin changes rapidly within the first 6 hrs following ICU admission and predicts ICU mortality and inotrope requirement as well as or better than APACHE II and SOFA scores. Serial urine albumin measurement may provide a means of monitoring the microvascular effects of systemic inflammation.

Does microalbuminuria predict illness severity in critically ill patients on the intensive care unit? A systematic review

CONTEXT

Studies assessing the accuracy of microalbuminuria to predict illness severity on the intensive care unit have produced inconsistent results.

OBJECTIVE

To determine the diagnostic accuracy of microalbuminuria to predict illness severity in critically ill patients on the intensive care unit.

DATA SOURCE

MEDLINE (1951 to September 2004) and EMBASE (1980 to September 2004) electronic databases were searched for relevant studies. Reference lists of all abstracts were manually searched to identify studies not included in the electronic database.

STUDY SELECTION

Studies that prospectively evaluated the accuracy of microalbuminuria to predict illness severity and/or mortality probability in adult patients on the intensive care unit were selected.

DATA EXTRACTION

We included nine studies in the review. Data to evaluate methodological quality and results were abstracted.

DATA SYNTHESIS

The methodological quality of a number of studies was poor. Significant heterogeneity in the design and conduct of the studies circumvented the data being subjected to meta-analysis. Studies also differed in the timing of the index test, in the methods of quantifying microalbuminuria, and in the cutoff values used.

CONCLUSIONS

This descriptive analysis reveals that microalbuminuria may hold promise as a predictor of illness severity and mortality on the intensive care unit. However, future epidemiologic studies need to be conducted to determine the optimal timing as well as the threshold reference value for the urine albumin creatinine ratio in the adult intensive care unit population. Thereafter, multiple-center prospective epidemiologic studies must be conducted to confirm and validate the findings of these preliminary studies. Future studies should conform to the Standards for Reporting of Diagnostic Accuracy checklist in terms of study design, conduct, and reporting. Presently there is no evidence to warrant the use of this tool on the intensive care unit.

Prognostic significance of microalbuminuria in non-diabetic patients with acute myocardial infarction

BACKGROUND

The aim of this study was to examine whether the presence of microalbuminuria (20-200 microg/min) can predict in-hospital morbidity and mortality in non-diabetic patients with acute myocardial infarction.

METHODS

Two hundred twenty-three (172 men and 51 women) non-diabetic patients with acute myocardial infarction were studied prospectively. The main outcome measures of the study were based on a comparison of in-hospital mortality and major non-fatal in-hospital events (pulmonary edema, post-infarction angina, infarct extension, mechanical complications, conduction disturbances and ventricular arrhythmias) between microalbuminuric and normoalbuminuric patients.

RESULTS

A significant proportion of patients (33.6%) had microalbuminuria. Seventy-six patients (34%) developed an in-hospital event (fatal or non-fatal). Six patients (2.7%) with acute myocardial infarction died in the hospital. Patients with microalbuminuria had a higher mortality rate in comparison with normoalbuminuric patients (6.6% vs. 0.68%, p = 0.01). For non-fatal events, the incidence of pulmonary edema and ventricular arrhythmias was significantly higher in patients with microalbuminuria (14.6% vs. 3.4%, p < 0.001 and 12% vs. 3.4%, p = 0.01, respectively). The combined end-point of the total number of fatal and non-fatal events was significantly higher in patients with microalbuminuria (57.3% vs. 22.3%, p < 0.001). In multiple logistic regression analysis, microalbuminuria (p < 0.001) and ejection fraction (p = 0.01) were independently related to the occurrence of major in-hospital events.

CONCLUSIONS

Microalbuminuria is a significant predictor of in-hospital morbidity and mortality in non-diabetic patients with acute myocardial infarction.

Monitoring Urinary Orosomucoid in Acute Inflammation: Observations on Urinary Excretion of Orosomucoid, Albumin, α1-Microglobulin, and IgG

Background: Inflammation-associated proteinuria in acute, nonrenal disease is a common but poorly understood phenomenon. We performed an observational study of the urinary excretion of orosomucoid (α1-acid glycoprotein), albumin, α1-microglobulin (protein HC), and IgG to obtain quantitative and temporal data on these 4 proteins.

Methods: Urine samples were collected at daily intervals for up to 23 days from 6 patients with surgery-induced inflammation and at hourly intervals for a 24-h period from 7 sepsis patients. Urinary protein concentrations were assessed by immunoturbidimetry.

Results: During surgery-induced inflammation, the increase and decrease in orosomucoid excretion mirrored changes in plasma C-reactive protein. Values for all 4 urinary proteins were increased in sepsis patients. The observed maximum increases in urinary protein excretion relative to the upper reference values were 280-fold for orosomucoid, 98-fold for α1-microglobulin, 33-fold for albumin, and 26-fold for IgG.

Conclusions: Orosomucoid, usually present in plasma and urine in much lower concentrations than albumin, is increased in urine to concentrations equal to or higher than albumin in proteinuria associated with acute inflammation. The pathophysiologic mechanisms responsible for this markedly increased excretion are unknown. Monitoring of urinary excretion of orosomucoid and other specific proteins, expressed as protein/creatinine ratios, may provide a window for clinically relevant real-time observation of changes in acute inflammatory processes. Orosomucoid in urine may be a more informative marker than albumin for inflammation.

Pulmonary and renal function following cardiopulmonary bypass is associated with systemic capillary leak

OBJECTIVE

The purpose of this study was to compare perioperative capillary permeability during cardiac surgery with subsequent pulmonary and renal function.

DESIGN

An observational prospective comparison of capillary permeability (microalbuminuria) during and after cardiopulmonary bypass (CPB), with postoperative pulmonary and renal function.

SETTING

A university teaching hospital.

PARTICIPANTS

Forty patients, mean (range) age 67.8 (50-85) years, undergoing elective first-time coronary artery bypass grafting (CABG).

INTERVENTIONS

Urine albumin concentration (AC) and albumin creatinine ratio (ACR) were compared with PO2 /FIO2 ratio, mechanical ventilation (intermittent positive-pressure ventilation [IPPV]) duration, and renal function.

MEASUREMENTS AND MAIN RESULTS

Median (range) AC and ACR increased from 8.3 (1.6-184.2) mg/L and 0.65 (0.1-18.8) mg/mmol preoperatively to 13.6 (1.6-267.2) mg/L and 4.80 (0.3-54.2) mg/mmol 10 minutes postbypass (p = 0.003 for ACR Wilcoxon rank test: not significant for AC). AC 2 hours postbypass was associated with mean PO2 /FIO2 ratio 0 to 2 hours postbypass and AC 4 hours postbypass was associated with mean PO2 /FIO2 ratio 0 to 2 and 2 to 12 hours postbypass (p < 0.05 Spearman). ACR 2 hours postbypass was associated with mean PO2 /FIO2 ratio 0 to 2 and 2 to 12 hours postbypass (p < 0.05 Spearman). AC 10 minutes and 2 hours postbypass and ACR 2 hours postbypass were associated with the duration of IPPV (p < 0.03). Day 1 serum creatinine was associated with pre- and 4 hours postbypass AC and ACR (p < 0.05). Day 2 serum creatinine was associated with 2 and 4 hours postbypass ACR (p < 0.05).

CONCLUSIONS

The magnitude of increase in capillary permeability during CABG is associated with later pulmonary and renal function.

Urine albumin excretion in acute ischaemic stroke is related to serum interleukin-6

BACKGROUND AND PURPOSE

Several studies show a link between microalbuminuria and markers of inflammation. Increased urine albumin excretion accompanies acute ischaemic stroke. The mechanisms responsible for microalbuminuria in acute stroke patients remain unclear. The goal of this study was to determine if there is a relationship between urine albumin excretion and interleukin-6, a key mediator of acute phase reaction.

METHODS

Nineteen acute ischaemic stroke patients and 13 controls matched for age, sex and cardiovascular risk factors were included. Serum interleukin-6 level was measured on the 2nd day of stroke at 06:00 am, 10:00 am, 06:00 pm and 10:00 pm using ELISA method. Urine albumin excretion was determined using immunonephelometric method.

RESULTS

Interleukin-6 level and urine albumin excretion were significantly higher in stroke patients than in controls. There was a significant correlation between interleukin-6 level and urine albumin excretion in stroke patients (R = -0.60 at 06:00 am; R = -0.49 at 10:00 am; R = -0.64 at 06:00 pm; R = -0.54 at 10:00 pm) but not in controls.

CONCLUSIONS

Urine albumin excretion in acute ischaemic stroke is related to serum interleukin-6.

[Proteinuria and urinary beta 2-microglobulin as markers of tubular malfunction in the assessment of severity of acute pancreatitis]

INTRODUCTION

Proteinuria is a common finding in acute pancreatitis (AP). Increased urinary beta 2-microglobulin can be explained by renal tubular malfunction induced by substances released from the pancreas. The degree of renal tubular malfunction may reflect the severity of AP.

AIM

To assess proteinuria and urinary beta 2-microglobulin as prognostic factors in AP.

PATIENTS AND METHODS

We retrospectively studied patients with AP with symptom onset within 24 hours before admission. Random urine specimens were obtained on days 1, 2 and 3 after admission. In a subgroup of 25 patients, urine samples could be obtained within 24 hours of symptom onset on day 1. The severity of AP was established using the Atlanta criteria. Proteinuria and beta 2-microglobulin were determined and were adjusted by urinary creatinine concentrations.

RESULTS

We studied 51 patients with AP (26 men and 25 women; age: 59.6 (+/-16.7 years). Fifteen cases of AP were severe and 36 were mild. The most frequent etiology was gallstones (60.1%). Levels of proteinuria were (median and interquartile range) in mg/g creatinine: day 1: 180.5 (84.0-250.9), day 2: 164.3 (16.7-421.7), and day 3: 136.7 (24.0-371.29). Differences between severe and mild AP were significant on day 2 of admission: 339.7 (191.7-471.8) versus 120,1 (11.0-382.6); p = 0.04. Levels of urinary beta 2-microglobulin in AP on days 1 to 3 postadmission were: 9.7 (1.1-93.3), 27.6 (4.7-421.4) and 88.3 (7.3-415.2) microg/mg of creatinine, respectively. When urinary beta 2-microglobulin was compared between severe and mild AP, no significant differences were found among days 1, 2 and 3. Selection of only the subgroup of patients whose urine samples were obtained within 24 h of symptom onset, did not improve the results of these urine markers for the group as a whole.

CONCLUSIONS

1) Proteinuria was slightly increased in severe AP and was able to discriminate between mild and severe episodes on day 2 of admission. 2) Urinary beta 2-microglobulin as a tubular malfunction marker did not discriminate between mild and severe AP in patients in our study.

Microalbuminuria in critically ill medical patients: prevalence, predictors, and prognostic significance

OBJECTIVE

To ascertain the prevalence, predictors, and prognostic significance of microalbuminuria in critically ill patients.

DESIGN

Prospective cohort study.

SETTING

Medical intensive care unit of a community teaching hospital.

PATIENTS

Admitted critically ill patients.

MEASUREMENTS AND MAIN RESULTS

We measured serial spot urine albumin-creatinine ratios in 104 critically ill patients, with a median age of 64.5 yrs and median Acute Physiology and Chronic Health Evaluation (APACHE) II and Sequential Organ Failure Assessment (SOFA) scores of 20.5 and 5.0, respectively. Sixty-nine percent of the patients had microalbuminuria or clinical proteinuria and 43.3% had an albumin-creatinine ratio >/=100 mg/g at admission. The acuity of illness, being non-White, and having diabetes mellitus were independent predictors of albumin-creatinine ratio >/=100 mg/g. The overall mortality rate was 26.9% (28/104). Patients with an albumin-creatinine ratio >/=100 mg/g were 2.7 times as likely to die compared with those with an albumin-creatinine ratio <100 mg/g, even after simultaneous adjustments for age, and APACHE II and SOFA scores (odds ratio, 2.7; 95% confidence interval, 1.1-7.2, p =.04). The association of albumin-creatinine ratio >/=100 mg/g with death was consistent across age, ethnicity, renal function, acuity of illness, and comorbid conditions. Among survivors, patients with an albumin-creatinine ratio >/=100 mg/g stayed approximately 5 days longer in the hospital (p =.0007). Overall, the albumin-creatinine ratio shared similar predictive characteristics with APACHE II and SOFA scores.

CONCLUSIONS

This study confirms a high prevalence of microalbuminuria in critically ill patients and suggests that an albumin-creatinine ratio >/=100 mg/g is an independent predictor of mortality and hospital stay.

Mortality prediction at admission to intensive care: a comparison of microalbuminuria with acute physiology scores after 24 hours

OBJECTIVE

To compare low level albumin excretion (microalbuminuria), a marker of systemic capillary permeability, with mortality, Acute Physiologic And Chronic Health Evaluation (APACHE II) score, the Simplified Acute Physiologic (SAP II) score, and their derived mortality probabilities in patients admitted to a general intensive care unit.

DESIGN

Prospective observational study.

SETTING

A 14-bed intensive care unit in a university teaching hospital.

PATIENTS

A total of 140 consecutive patients (59 surgical, 48 medical, 22 trauma, and 11 burns).

INTERVENTIONS

Urine collection within 15 mins of intensive care unit admission for assessment of microalbuminuria.

MEASUREMENTS AND MAIN RESULTS

Microalbuminuria, expressed as the albumin-creatinine ratio (ACR: normal, <2.3 mg/mmol), was compared with mortality, APACHE II and SAP II scores and their derived mortality probabilities after 24 hrs, intensive care unit stay, and markers of organ function and inflammation. Median (95% confidence interval) ACR at admission for survivors (n = 115) and nonsurvivors (n = 25) were 4.2 (3.6-6.5) and 17.8 (8.0-40.8) mg/mmol, respectively (p =.0002 Mann Whitney). For 92 surgical, trauma, and burn patients, of whom 81 survived, ACR of >5.9 mg/mmol gave a sensitivity for death of 100%, specificity of 59%, positive predictive value of 25%, and negative predictive value of 100%. Mortality probability receiver operator characteristic curve areas for ACR, APACHE II, and SAP II were 0.843 (p <.0001), 0.793 (p =.0004), and 0.770 (p =.0017), respectively. ACR was associated with intensive care unit stay (p =.0021) and highest serum C-reactive protein (p =.0002), serum creatinine (p <.0001), and bilirubin (p =.0009). For 48 medical patients, of whom 34 survived, admission ACRs for survivors and nonsurvivors were 8.3 (5.7-10.8) and 10.7 (4.1-48.2) mg/mmol, respectively (p =.32). SAP II, but not APACHE II, score was significantly higher for nonsurvivors.

CONCLUSIONS

For surgical, trauma, and burn patients, but not medical patients, microalbuminuria within 15 mins of intensive care unit admission predicted death as well as APACHE II and SAP II scores calculated after 24 hrs, and it shows promise as a predictor of outcome.

C-reactive protein and soluble vascular cell adhesion molecule-1 are associated with elevated urinary albumin excretion but do not explain its link with cardiovascular risk

An elevated urinary albumin excretion rate (UAER) is associated with an increased risk of cardiovascular mortality, but the pathophysiological mechanism underlying this association is poorly understood. To investigate the role of endothelial dysfunction, leukocyte adhesion, and low-grade inflammation (1) in the development of elevated UAER (study I) and (2) in linking elevated UAER with risk of cardiovascular mortality (study II), we performed a prospective study in an age-, sex-, and glucose tolerance- stratified sample of a population-based cohort aged 50 to 75 years. High levels of von Willebrand factor, soluble vascular cell adhesion molecule-1 (sVCAM-1), and C-reactive protein (CRP) were used as markers of endothelial dysfunction, leukocyte adhesion, and low-grade inflammation, respectively. For study I, subjects who had normal UAER at baseline (n=316 subjects, 66 with type 2 diabetes) were reexamined after a mean follow-up of 6.1 years. The development of elevated UAER was defined as a mean albumin-to-creatinine ratio >2.0 mg/mmol at follow-up. Age-, sex-, and glucose tolerance- adjusted logistic regression analyses showed the development of elevated UAER to be significantly associated with levels of sVCAM-1 and CRP (odds ratio 1.14 [95% CI 1.02 to 1.27] per 10% increase of sVCAM-1 and odds ratio 1.17 [95% CI 1.04 to 1.32] per 50% increase of CRP). The results were not materially different after additional adjustment for hypertension, body mass index, cardiovascular disease, and creatinine clearance or stratification by the presence of diabetes. For study II, the vital status of all subjects (n= 575) was determined after a mean follow-up of 6.6 years. Eighty-one of 575 subjects died (30 died of cardiovascular disease). The presence of elevated UAER at baseline was associated with a 4.1-fold (1.94 to 8.73) increased risk of cardiovascular death after adjustment for age, sex, and glucose tolerance status. Adjustment for levels of von Willebrand factor, sVCAM-1, or CRP did not materially affect the results, nor did additional adjustment for the presence of hypertension, retinopathy, and cardiovascular disease and for levels of homocysteine, triglycerides, and high density lipoprotein cholesterol. Leukocyte adhesion (sVCAM-1) and low-grade inflammation (CRP) are determinants of the development of elevated UAER. However, these determinants do not explain the association between elevated UAER and cardiovascular mortality.

Predictive value of microalbuminuria in medical ICU patients: results of a pilot study

STUDY OBJECTIVES

To evaluate the predictive value of microalbuminuria in the development of acute respiratory failure (ARF) and multiple organ failure (MOF) in ICU patients.

DESIGN

Prospective, observational study.

SETTING

A 31-bed, mixed medicosurgical ICU in a university hospital.

PATIENTS

All adult medical patients admitted to the ICU over a 2-month period, except those receiving nephrotoxic drugs, or those with urologic trauma resulting in frank hematuria or urinary infection, or with existing chronic renal disease (serum creatinine level > or 2.0 mg/dL).

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Urinary samples for microalbumin measurement were collected at hospital admission and at 8, 24, 48, 72, 96, and 120 h after hospital admission. The severity of illness was assessed by the APACHE (acute physiology and chronic health evaluation) II score calculated on the first ICU day, and the degree of organ dysfunction was assessed using the sequential organ failure assessment (SOFA) score. Acute respiratory failure (ARF) was defined as a SOFA respiratory score > or = 3. Patients were separated into two groups according to the trend in microalbuminuria levels over the first 48 h: patients in group 1 had increasing microalbuminuria levels, and patients in group 2 had decreasing microalbuminuria levels. Group 1 included 14 patients in whom microalbuminuria levels increased from 5.2 +/- 2.0 to 19.0 +/- 3.0 mg/dL. Group 2 included 26 patients in whom microalbuminuria levels decreased from 16.4 +/- 4.0 to 7.8 +/- 3.0 mg/dL. The hospital mortality rate was 43% in group 1 and 15% in group 2 (p < 0.05). The APACHE II score and the SOFA score were higher in group 1 than in group 2. The negative predictive value of increasing microalbuminuria was 100% for the development of ARF and 96% for MOF; the positive predictive value of increasing microalbuminuria was 57% for the development of ARF and 50% for MOF.

CONCLUSIONS

Accurate identification of patients destined for ARF and MOF development may enable therapeutic strategies to be applied to limit the disease process. Trend analysis of urinary albumin excretion over the first 48 h of an ICU admission may provide a useful means of identifying such patients. Additional studies need to be performed in larger, mixed patient populations to confirm these findings.

Review of feline pancreatitis part two: clinical signs, diagnosis and treatment

In the past decade pancreatitis has become recognised as a significant disease in the cat. Chronic, mild pancreatitis is often associated with more commonly diagnosed diseases such as inflammatory bowel disease or cholangitis/cholangiohepatitis. Furthermore, acute pancreatitis with similar complications to those seen in dogs is now diagnosed more frequently in cats. Unfortunately, the clinical signs and clinicopathological findings in cats with pancreatitis are often non-specific and vague. The lack of specific signs often results in a diagnosis being made only when the veterinary surgeon has a strong index of suspicion for pancreatitis and vigorously pursues that diagnosis. Pancreatitis is an important disease in cats, has been implicated as a potential cause of diabetes mellitus, and when present complicates the treatment of diabetes and other intra-abdominal diseases in cats.

Glomerular permeability after surgical trauma in children: relationship between microalbuminuria and surgical stress score

OBJECTIVES

To determine whether there is an increase of urinary albumin during and after surgical trauma and investigate a possible relationship between microalbuminuria and the severity of surgical stress.

DESIGN

Prospective study.

SETTING

University hospital pediatric intensive care unit.

PATIENTS

Forty consecutive children scheduled for elective surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Microalbuminuria/urinary creatinine ratio (MACR) was measured before, during, and after elective moderate or major surgical procedures. The Oxford Surgical Stress Score (SSS) was determined for each patient at the end of the operation, and its relationship with maximum deviation of MACR from baseline values was investigated. MACR showed a progressive increase during surgery and a decrease afterward, reaching preoperative values in most cases within 24 hrs after the end of surgery. There was a significant correlation between the increase in MACR and severity of the surgical trauma as measured by SSS. Two patients showed a rise in MACR after the initial postoperative normalization before clinical appearance of a surgical complication and one patient showed a persistent rise in MACR before clinical appearance of a septic complication. None of the other patients showed any rise in MACR after postoperative normalization, and they all had an uneventful recovery.

CONCLUSIONS

MACR rises during and after major or moderate elective surgery in children. There is a significant positive correlation between severity of surgical trauma and capillary permeability in pediatric patients. Microalbuminuria, as an index of capillary permeability, may be an early sign of incipient complications and assist in the identification of those patients whose condition will deteriorate. The test is a cheap, blood-sparing, easy-to-perform bedside procedure that may have a useful role in clinical practice for evaluating the effect of surgical trauma on capillary permeability in children.

Inflammation and microalbuminuria in nondiabetic and type 2 diabetic subjects: The Insulin Resistance Atherosclerosis Study

BACKGROUND

Microalbuminuria is a risk factor for cardiovascular disease, but the underlying pathomechanisms are still poorly understood. A relationship between C-reactive protein (CRP), a sensitive marker of inflammation, and atherosclerotic disease has been reported recently.

METHODS

We hypothesized that microalbuminuria might be associated with chronic inflammation and investigated the relationship of urinary albumin excretion, as assessed from the albumin-to-creatinine ratio (ACR), in an untimed morning urine specimen, and two inflammatory markers (CRP and fibrinogen) in the large, triethnic population of the Insulin Resistance Atherosclerosis Study (IRAS). After exclusion of subjects with macroalbuminuria, 1481 subjects were studied.

RESULTS

Both inflammatory markers were related to urinary ACR (r = 0.17 for CRP and r = 0.14 for fibrinogen, both P = 0.0001), an association that remained significant after adjustment for demographic variables, diabetic status, smoking, and use of angiotensin-converting enzyme inhibitors (P < 0.01). Mean levels of CRP and fibrinogen were elevated in microalbuminuric (N = 262) versus normoalbuminuric (N = 1219) subjects (5.37 +/- 0.47 vs. 3.80 +/- 0.15 mg/L and 295.7 +/- 4. 0 vs. 278.2 +/- 1.6 mg/dL, both P < 0.0001). The associations were consistent among nondiabetic and type 2 diabetic subjects and among the three ethnic groups of the IRAS (non-Hispanic whites, blacks, Hispanics). In a logistic regression model, fibrinogen was independently associated with microalbuminuria (P = 0.047), along with hypertension, female gender, waist circumference, and fasting blood glucose, while CRP was not independently related to microalbuminuria in this model (P = 0.26).

CONCLUSION

We have shown an association of CRP and fibrinogen with urinary albumin excretion in the microalbuminuric range in type 2 diabetic and nondiabetic individuals. Chronic inflammation therefore emerges as a potential mediator between microalbuminuria and macrovascular disease.

Biochemical and inflammatory changes in the exercising claudicant

Intermittent claudication is an early manifestation of atherosclerosis in the leg. The prognosis for the claudicating limb is reasonably good, but patients have excess cardiovascular morbidity and mortality rates compared with a control population. Increasing evidence suggests that the calf pain experienced when walking followed by rest generates a low-grade inflammatory response. The cumulative effects of these individual events may have an adverse effect on the progression of atherosclerosis. A review of the literature was performed to identify studies measuring the exercise-induced inflammatory response in claudicants and to try to identify the role of cumulative inflammatory changes in the progression of atherosclerosis. The effect of exercise training on these markers is briefly explored. Walking until the onset of calf pain (ischaemia) followed by rest (reperfusion) results in the generation of oxygen-derived free radicals, neutrophil activation and a generalized increase in vascular permeability. Baseline levels of chronic inflammatory markers such as acute-phase proteins are elevated in claudicants compared with controls, suggesting that the transient acute inflammatory response has longer-term consequences. Therapeutic exercise training appears to lead to an attenuation of these inflammatory markers. Intermittent claudication can be considered as part of an inflammatory disease process. However, the concerns that exercise training might potentiate the vascular inflammatory response appear to be unjustified, although further work is needed to clarify this. Exercise training should therefore be considered as an important treatment option for claudication.

The evidence for exercise-induced inflammation in intermittent claudication: should we encourage patients to stop walking?

OBJECTIVES

To review clinical and experimental evidence that exercise to the onset of calf pain in patients with intermittent claudication results in an inflammatory response, and to consider whether repeated inflammatory events induced by therapeutic exercise training may lead to progression of atherosclerosis.

METHODS

A literature search was performed to identify studies measuring biochemical markers of exercise-induced ischaemia-reperfusion injury in patients with intermittent claudication. Current theories of atherogenesis were reviewed and the use of acute-phase proteins as potential markers of vascular disease explored.

RESULTS

Exercise to the onset of calf pain results in an inflammatory response with free radical formation, neutrophil activation and systemic vascular endothelial damage. Acute-phase proteins such as C-reactive protein and serum amyloid A protein have exciting potential use as stable biochemical markers of disease in claudication.

CONCLUSIONS

Further studies are needed to determine the effect of long-term exercise training on exercise-induced inflammation in claudication. Early work suggests, in fact, that exercise attenuates this inflammatory response. If this were confirmed then it would support the clinical impression that exercise training is beneficial in terms of symptomatic improvement and cardiovascular health in patients with intermittent claudication.

Antioxidant consumption during exercise in intermittent claudication

Twenty male claudicant patients and nine age-matched controls were exercised on a treadmill. Blood and urine samples were taken before and after exercise. Total antioxidant concentration was measured using an enhanced chemiluminescent assay and microalbuminuria determined by radioimmunoassay. Claudicants had increased microalbuminuria after exercise. Mean (s.e.m.) antioxidant concentrations were similar for patients and controls at rest: 479(28) and 438(23) mumol/l respectively. Claudicants showed a significant decrease in antioxidant concentration 1 min after exercise to 428(27) mumol/l; this returned to 470(30) mumol/l by 10 min. A correlation was found between the decrease in antioxidant concentration and the increase in microalbuminuria (rs = -0.496, P < 0.05). This study supports the concept of ischaemia-reperfusion injury in claudicant patients and has implications for treatment.

Inflammatory mediators in acute pancreatitis

The cellular events leading to acute pancreatitis are not well defined and the mechanism by which known aetiological factors initiate the disease process remains to be established. Inflammatory mediators have recently been implicated as potential early markers of disease severity and may help elucidate the pathophysiology of the disease. Oxidative stress is emerging as a common effector of the acinar cell injury in experimental acute pancreatitis and clinical findings indicate that neutrophil activation is a significant early event. In common with neutrophil-mediated tissue damage in states of tissue hypoperfusion, acute pancreatitis shows many features of an ischaemia-reperfusion injury. Increased levels of phospholipase A2 have been demonstrated; this enzyme induces synthesis of prostaglandins and platelet-activating factor, a potent inflammatory mediator. New therapeutic approaches to the complications of acute pancreatitis may be through manipulation of such mediators of inflammation.

Pharmacological reduction of the systemically damaging effects of local ischaemia

Many patients with intermittent claudication are encouraged to exercise. However, transient exercise-induced muscle ischaemia results in systemic vascular endothelial injury associated with increased vascular permeability manifest as an increase in urinary albumin excretion. Repetitive systemic vascular endothelial injury leads to accelerated atherogenesis and may explain the high cardiovascular mortality rate of claudicants. Oxpentifylline, a haemorheological agent, has recently been shown to prevent vascular endothelial injury in animal models. A double-blind, placebo-controlled, cross-over trial was undertaken to determine the effect of oxpentifylline on exercise-induced systemic vascular endothelial injury in 20 claudicants. Urinary albumin, expressed as a creatinine ratio (ACR), was measured before and 1 and 2 hours after standardised exercise following 1 week treatment with either active drug or placebo. Oxpentifylline reduced the median (range) 1 hour post exercise increase in ACR from 0.35 (-0.46-12.72) to 0.02 (-6.00-14.10) mg/mmol. (p = 0.030, z = 2.2 Wilcoxon rank sign test). These results confirm that local ischaemia is associated with a potentially deleterious systemic effect and that it may be possible to attenuate this pharmacologically. The clinical significance of this is yet to be determined.

Microproteinuria predicts the severity of systemic effects of reperfusion injury following infrarenal aortic aneurysm surgery

Noncardiogenic pulmonary dysfunction can be demonstrated in all patients following elective aortic aneurysm repair and is a cause of postoperative morbidity. Aortic clamping and reperfusion initiate a systemic inflammatory response producing endothelial damage and increases in vascular permeability. In the lung this is manifest as pulmonary edema and in the kidney as detectable increases in urinary protein excretion (microproteinuria). Immunoassay of low-level protein excretion appears to provide an index of the systemic effects of local reperfusion injury and may allow early prediction of complications such as pulmonary edema. Hourly urinary albumin and IgG excretion was measured in 40 patients undergoing infrarenal aortic aneurysm repair and expressed as ratios to urinary creatinine (albumin/creatinine ratio [ACR] and IgG/creatinine ratio [IgGCR]). These were compared to clinical outcome. Pulmonary dysfunction was assessed according to PaO2:FiO2 ratios and chest radiography. Within 180 minutes of beginning surgery all patients had significant increases in ACR and IgGCR. Ten patients who manifested respiratory dysfunction had significantly higher ACRs at 4 hours (median 84.8, 95% confidence intervals, range 47.7 to 136) than patients who made uneventful recoveries (median 16.6, 95% confidence intervals, range 7.9 to 31.7). IgGCR increases paralleled that of ACRs. Differences persisted for 24 hours. Urinary protein excretion rises rapidly during aortic surgery. The degree of increase appears to predict development of pulmonary dysfunction. This simple test may provide a rational basis for evaluation of therapeutic modalities to limit reperfusion injury in these patients.

Assessment of intermittent claudication by quantitation of exercise-induced microalbuminuria

Urinary albumin excretion rates, expressed as albumin-creatinine ratios (ACR, mg/mmol) were measured before and after exercise in 23 claudicants and 10 controls. The mean (range) resting ACRs in the claudicants and controls were 4.42 (0.2-34.6) and 0.77 (0.3-2.8) respectively (P less than 0.001). ACR increased after exercise by a mean of 153% in claudicants to 9.7 (0.2-48.1; P less than 0.001) with no change in controls, 0.79 (0.2-2.1). In patients with claudication there was a positive correlation between ankle pressure recovery time and the relative increase in ACR after exercise (r = 0.64, P less than 0.01). The post-exercise increase in ACR was reduced in all nine patients who underwent bypass surgery. Measurement of ACR after exercise appears to be related to severity of muscle ischaemia and may assist in the assessment of patients with intermittent claudication.